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Background: Following maternal COVID-19 vaccination, the persistence of antibodies in sera and breast milk for mothers and infants is not well characterized. We sought to describe the persistence of antibodies through 2 months after delivery in maternal and infant serum and breast milk following maternal COVID-19 mRNA vaccination and to examine differences by receipt of booster dose during pregnancy or postpartum., Methods: This is a prospective cohort study with enrollment from July 2021 to January 2022 at 9 US academic sites. Pregnant or postpartum participants and their infants were enrolled after COVID-19 mRNA monovalent vaccination during pregnancy (primary 2-dose series) with booster (third dose) vaccination during pregnancy or within 2 months post-partum. SARS-CoV-2-binding and functional antibody responses at delivery and 2 months after delivery in mothers and infants were measured by spike and receptor-binding domain immunoglobulin (Ig) G, pseudovirus and live neutralizing antibody (nAb) titers to ancestral and Omicron BA.1 and BA.5 strains. Breast milk spike and receptor-binding domain IgG and IgA titers were also measured., Results: A total of 237 maternal/infant dyads were included (110 primary series during pregnancy, 99 pregnancy booster and 28 postpartum booster). A pregnancy booster resulted in 2.2-4.7-fold higher IgG and nAb at delivery and 2 months for both mothers and infants compared to the primary series alone (P < 0.001 for all comparisons). While infant IgG and nAb titers decreased by 2 months of age, the proportion of infants with detectable nAb at 2 months was greater in infants of mothers boosted during pregnancy compared with primary series for all variants (D614G: 99% vs. 56%; BA.1: 56% vs. 4% and BA.5: 57% vs. 9%; P < 0.001 for all comparisons). Breast milk spike IgA and IgG were present in 64%-100% and 100% of participants, respectively, and those boosted during pregnancy or postpartum had 3.1-4.6-fold higher levels of breast milk antibodies at 2 months compared to primary series during pregnancy (P < 0.001)., Conclusions: mRNA COVID-19 monovalent booster vaccination during pregnancy results in significantly higher maternal and infant serum-binding IgG and nAb titers compared to a primary 2-dose series, including against Omicron variants, through 2 months of age. Breast milk antibodies following maternal vaccination during pregnancy or postpartum may provide additional protection during early infancy., Competing Interests: F.M.M. is an investigator of pediatric studies of COVID-19 vaccines for Pfizer and for a pediatric Remdesivir study conducted by Gilead Sciences, Inc; serves as an investigator on projects supported by a National Institutes of Health (NIH) contract for a Vaccine Treatment and Evaluation Unit (VTEU), serves as a member of the Data Safety Monitoring Board (DSMB) for clinical trials conducted by Pfizer, Moderna, Meissa Vaccines, Virometix and the NIH; is a member of the American Academy of Pediatrics Section of Infectious Diseases and the Immunization Expert Group of the American College of Obstetrics and Gynecology; and Chair of the Coalition for Epidemic Preparedness and Innovation-Safety Platform for Emergency Vaccines (CEPI-SPEAC) Maternal Immunization Working Group. K.M.N. is a member of the World Health Organization Strategic Advisory Group of Experts on Immunization, serves as co-investigator on an NIH contract for a VTEU and the Co-Chair of the NIH COVID Prevention Network and served as an investigator for Phase I/II Pfizer COVID-19 vaccine grant, with a grant to the institution, but no salary support. K.M.N. receives grants from Pfizer to conduct clinical trials of COVID vaccines through the Center for Vaccine Development and Global Health at the University of Maryland, Baltimore. K.M.N. receives grants from NIH to participate in the overall organization of COVID-19 vaccine trials and for participation in vaccine trials. M.J.M. conducts laboratory research and clinical trials with contract funding for vaccines or monoclonal antibodies versus SARS-CoV-2 with Lilly, Pfizer and Sanofi and receives personal fees for the Scientific Advisory Board service from Merck, Meissa Vaccines, Inc, and Pfizer. M.S.S. served as an advisor for Moderna (ended December 2021) and is currently serving as an advisor for Ocugen, Inc. B.A.R. currently holds a position on a DSMB for clinical trials at Gilead Sciences, Inc. R.C.B. at Cincinnati Children’s Hospital receives research grant support for clinical trials from PATH, Astra Zeneca and Pfizer in which she serves as a co-investigator. B.B. owns shares in HDT Bio Corp. J.S.G. receives research funds from NIH for the Moderna KidCOVE study. R.M.N. is a paid advisor to Gilead and an investigator on NIH-funded trials of Moderna, Pfizer and Janssen vaccines. All authors have completed relevant conflicts of interest in the Disclosure of Potential Conflicts of Interest Section of the Authorship Form., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

For COVAIL recipients of a COVID-19 Sanofi booster vaccine, neutralizing antibody titers were assessed as a correlate of risk (CoR) of COVID-19. Peak and exposure-proximal titers were inverse CoRs with covariate-adjusted hazard ratios (95% confidence intervals) 0.30 (0.11, 0.78) and 0.25 (0.07, 0.85) per 10-fold increase in weighted average titer., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background and Objectives: Maternal vaccination may prevent infant coronavirus disease 2019 (COVID-19). We aimed to quantify protection against infection from maternally derived vaccine-induced antibodies in the first 6 months of an infant's life., Methods: Infants born to mothers vaccinated during pregnancy with 2 or 3 doses of a messenger RNA COVID-19 vaccine (nonboosted or boosted, respectively) had full-length spike (Spike) immunoglobulin G (IgG), pseudovirus 614D, and live virus D614G, and omicron BA.1 and BA.5 neutralizing antibody (nAb) titers measured at delivery. Infant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was determined by verified maternal-report and laboratory confirmation through prospective follow-up to 6 months of age between December 2021 and July 2022. The risk reduction for infection by dose group and antibody titer level was estimated in separate models., Results: Infants of boosted mothers (n = 204) had significantly higher Spike IgG, pseudovirus, and live nAb titers at delivery than infants of nonboosted mothers (n = 271), and were 56% less likely to acquire infection in the first 6 months (P = .03). Irrespective of boost, for each 10-fold increase in Spike IgG titer at delivery, the infant's risk of acquiring infection was reduced by 47% (95% confidence interval 8%-70%; P = .02). Similarly, a 10-fold increase in pseudovirus titers against Wuhan Spike, and live virus nAb titers against D614G, and omicron BA.1 and BA.5 at delivery were associated with a 30%, 46%, 56%, and 60% risk reduction, respectively., Conclusions: Higher transplacental binding and nAb titers substantially reduced the risk of SARS-CoV-2 infection in infants, and a booster dose amplified protection during a period of omicron predominance. Until infants are age-eligible for vaccination, maternal vaccination provides passive protection against symptomatic infection during early infancy., (Copyright © 2024 by the American Academy of Pediatrics.)

We compared the serologic responses of 1 dose versus 2 doses of a variant vaccine (Moderna mRNA-1273 Beta/Omicron BA.1 bivalent vaccine) in adults. A 2-dose boosting regimen with a variant vaccine did not increase the magnitude or the durability of the serological responses compared to a single variant vaccine boost., Competing Interests: Potential conflicts of interest. A. R. B. has received research support from NIH-NIAID, grants from Pfizer, Cyanvac, Moderna, Vaccine.co and Merck as well as consulting fees from Janssen and GSK. She serves as DSMB member for NIH, IDSA Public Health Committee. Honoraria as a speaker from Virology Education. L. R. B. has received grants from Wellcome Trust, Gates Foundation, NIH/Harvard Medical School through institution. Serves as member of DSMB for NIH and AMDAC for FDA. Dr Baden is involved in HIV and SARS-CoV-2 vaccine clinical trials conducted in collaboration with the NIH, HIV Vaccine Trials Network (HVTN), Covid Vaccine Prevention Network (CoVPN), International AIDS Vaccine Initiative (IAVI), Crucell/Janssen, Moderna, Military HIV Research Program (MHRP), the Gates Foundation, and Harvard Medical School. D. J. D. has received a contract from Leidos Biomedical/NIH research to conduct the clinical trial through institution. A. R. F. has received grants from Janssen, Pfizer, Merck, BioFire Diagnostics, Moderna, Vaccine company and CyanVac through institution. Consultant fees from Arrow Pharmaceutical, ADMA biologics, GSK, and honoraria as a speaker from Sanofi and GlaxoSmithKline. Serves as DSMB advisory boards for Novavax and received travel/meeting support from GlaxoSmithKline. S. E. F. has received funding from Leidos to Saint Louis University to conduct Protocol DMID 22-0004. Funding was also received to conduct the Moderna and Janssen trials phase 3 SARS-CoV-2 trials. Serves as DSMB for HVTN Safety Monitoring Board. D. N. F. has as a contract from CDC and is the site PI for DN Fusco study of COVID in Special Populations. D. N. F. served on an HBV Advisory board for Gilead related to hepatitis C & B viruses and Axcella related to Long COVID. P. A. G. has received funding from NIH. PAG has a patent for COVID-19 monoclonal not developed clinically and received consulting fees from International AIDS Society as speaker. L. C. I. has received support from NIH, Moderna, Pfizer, and Sanofi. L. C. I. has also received grants from GSK, Merck, Sharpe & Dohme Corp, CDC, Novavax, Pediatric Emergency Medicine Associates, and NIH/NLM/National Institute on Minority Health and Health Disparities as well as consulting fees from Moderna. L. C. I. has received honoraria as a speaker from American Academy of Pediatrics, Rockefeller University, Moderna, CDC and American Academy of Pediatrics- Georgia Chapter. L. C. I. Serves on Data Safety Monitoring for NIH-Phase 2 Vaccine Trial for Monkeypox, Moderna Scientific Advisory Board- North America, and CoVID-19 Task Force, Georgia. L. C. I. has a leadership role Break the Cycle of Health Disparities Inc, the Center for Spatial Analytics of the Georgia Institute of Technology, and the American Academy of Pediatrics (Executive Board for Section on Infectious Diseases). L. C. I. has received travel/meeting support from the American Academy of Pediatrics and Moderna. L. A. J. has received funding from NIH for support for this study, funding from Pfizer to support a clinical trial and contract funding for research support from the CDC and the NIH, all through institution. L. A. J. also reports unpaid participation on Data Safety Monitoring Boards for NIH funded clinical trials. S. K. has received research grants from NIH, Pfizer, U.S. Centers for Disease Control and Prevention, Meisa, Emergent BioSolutions. S. K. also received support from American Academy of Pediatrics as speaker. A. C. K. has received research support from COVID-19 Adaptive Variance Immunologic Landscape Trial # 28C15000NYUPG266894. S. J. L. has received NIH grants through institution. Consulting fees from Hookipa Pharma. A. F. L. has received grants from Merck, Gilead and, GSK through institution as well as consulting fees from Vir Biotechnology. A. F. L. has also received travel support from Merck to attend a required investigator meeting, testing kits and supplies to support research study from Hologic, Cepheid and medication donated by Mayne Pharma to support research study. M. M. has received funding from Emmes through NIH contract # HHSN272201500002C. L. J. M. has received funding from Emmes through NIH contract # HHSN272201500002C. D. C. M. has received funding from NIH/75N93019C00050-21A: CIVICS A- Option 21A-DMID Trials of COVID-19 Vaccines. J. M. has received funding from Division of Microbiology and Infectious Diseases, contract # 75N93021C00012. A. N. has received support from NIH-NIAID, CEIRR (Centers of Excellence for Influenza Research and Response) and Gates Cambridge Trust as well as grants from NIH-NIAID R01. R. M. N. has received grants from NIAID-DMID and travel/meeting support from Moderna. C. M. P. has received funding from NIAID UM1AI148684. R. M. P. has received funding from NIH DMID COVAIL as well as grants from Janssen, Moderna and NIH through institution. N. G. R. has received research grants from NIH, Pfizer, Merck, Sanofi, Quidel, Immorna, Vaccine Company and Lilly through her institution, consulting fees from Krog, honoraria as speaker for Virology education, and travel support from Sanofi and Moderna. N. G. R. serves as DSMB on safety committees for ICON, Micron and EMMES and is a member of the Moderna, Sanofi, Seqirus and Pfizer selected Advisory boards. Plays leadership advisory role for ARLG, TMRC, CDC-Pertussis challenge, Clinical Infectious Diseases. Equipment supports from Georgia Research Alliance. D. J. S. has received support from NIH-NIAID CEIRR, grants from NIH-NIAID R01, and travel support from NIH-NIAID CEIRR for NIH-related meetings. K. T. has received funding from Emmes through NIH contract # HHSN272201500002C. E. B. W. has received funding from Leidos Biomedical Research AGREEMENT NO. 22CTA-DM0009 as well as grants from Pfizer, Moderna, Sequiris, Clinetic, and Najit Technologies, with payments made to institution. E. B. W. has also received honoraria as a speaker from College of Diplomates of the American Board of Pediatric Dentistry, consulting fees from Iliad Biotechnologies, and travel/meeting support from the American Academy of Pediatrics. E. B. W. serves as member of Vaxcyte Scientific Advisory board. P. L. W. has received subcontract funding from NIH for this study as well as NIH grant funding and contract funding from Pfizer through University of Iowa. P. L. W. has also received consulting fees from Pfizer and serves on DSMB advisory board for Emmes Corporation, Blue Lake. M. B. has received research grants from Leidos Biomedical Research and Pfizer through institution. J. A. W. has received funding from NIH-DMID 75N91019D00024. R. L. A., T. M. B., S. M. M., M. K. M., J. H. B., S. C., C. L., P. C. R., R. R. authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Vaccine protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection wanes over time, requiring updated boosters. In a phase 2, open-label, randomized clinical trial with sequentially enrolled stages at 22 US sites, we assessed safety and immunogenicity of a second boost with monovalent or bivalent variant vaccines from mRNA and protein-based platforms targeting wild-type, Beta, Delta and Omicron BA.1 spike antigens. The primary outcome was pseudovirus neutralization titers at 50% inhibitory dilution (ID 50 titers) with 95% confidence intervals against different SARS-CoV-2 strains. The secondary outcome assessed safety by solicited local and systemic adverse events (AEs), unsolicited AEs, serious AEs and AEs of special interest. Boosting with prototype/wild-type vaccines produced numerically lower ID 50 titers than any variant-containing vaccine against all variants. Conversely, boosting with a variant vaccine excluding prototype was not associated with decreased neutralization against D614G. Omicron BA.1 or Beta monovalent vaccines were nearly equivalent to Omicron BA.1 + prototype or Beta + prototype bivalent vaccines for neutralization of Beta, Omicron BA.1 and Omicron BA.4/5, although they were lower for contemporaneous Omicron subvariants. Safety was similar across arms and stages and comparable to previous reports. Our study shows that updated vaccines targeting Beta or Omicron BA.1 provide broadly crossprotective neutralizing antibody responses against diverse SARS-CoV-2 variants without sacrificing immunity to the ancestral strain. ClinicalTrials.gov registration: NCT05289037 ., (© 2023. The Author(s).)

In a randomized clinical trial, we compare early neutralizing antibody responses after boosting with bivalent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) messenger RNA (mRNA) vaccines based on either BA.1 or BA.4/BA.5 Omicron spike protein combined with wild-type spike. Responses against SARS-CoV-2 variants exhibited the greatest reduction in titers against currently circulating Omicron subvariants for both bivalent vaccines., Competing Interests: Potential conflicts of interest. E. J. A. has received grants from Pfizer, Moderna, Janssen, GSK, Sanofi, Micron, and Regeneron through institution as well as consulting fees from Pfizer, Janssen, Moderna, and Sanofi. E. J. A. serves on safety/advisory boards for Sanofi, ACI Clinical/WCG and Kentucky Bioscience, Inc. A. R. B. has received research support from NIH-NIAID, grants from Pfizer, Cyanvac, and Merck as well as consulting fees from Janssen and GSK. L. R. B. has received grants from Wellcome Trust, Gates Foundation, NIH/Harvard Medical School through institution. Serves as member of DSMB for NIH and AMDAC for Food and Drug Administration (FDA). L. R. B. is involved in HIV and SARS-CoV-2 vaccine clinical trials conducted in collaboration with the NIH, HIV Vaccine Trials Network (HVTN), COVID Vaccine Prevention Network (CoVPN), International AIDS Vaccine Initiative (IAVI), Crucell/Janssen, Moderna, Military HIV Research Program (MHRP), the Gates Foundation, and Harvard Medical School. D. J. D. has received a contract from Leidos Biomedical research to conduct the clinical trial through institution. A. R. F. has received grants from Janssen, Pfizer, Merck, BioFire Diagnostics, and CyanVac through institution, consultant fees from Arrowhead and Icosavax, and honoraria as a speaker from Moderna and GlaxoSmithKline. A. R. F. also serves on safety/advisory boards for Novavax and received travel/meeting support from GlaxoSmithKline. S. E. F. has received funding from Leidos to Saint Louis University to conduct Protocol DMID22-0004. D. N. F. has as a contract from Centers for Disease Control and Prevention (CDC) and is the site principal investigator (PI) for clinical trials from Gilead, Regeneron, and MetroBiotech, LLC. She is the PI on 1 investigator-initiated award from Gilead and the co-PI on another investigator-initiated award from Gilead. D. N. F. served on an HBV Advisory board for Gilead in 2021 and received payment for expert testimony not related to COVID in 2022. P. A. G. has received funding for COVAIL clinical trial. P. A. G. has also received consulting fees from Janssen Vaccines. L. C. I. has received support for the present manuscript from NIH-NIAID/DMID, Moderna, Pfizer, and Sanofi. L. C. I. has also received grants from GSK, Merck, Sharpe & Dohme Corp, CDC, Novavax, AHRQ, and NIH/NLM/NIMHD as well as consulting fees from Moderna, CDC, and Pediatric Emergency Medicine Associates, LLC. L. C. I. has received honoraria as a speaker from American Academy of Pediatrics, Rockefeller University, and American Academy of Pediatrics- Georgia Chapter. L. C. I. serves on Data Safety Monitoring for NIH-Phase 2 Vaccine Trial for Monkeypox, Moderna Scientific Advisory Board- North America, and COVID-19 Task Force, Georgia. L. C. I. has a leadership role in the Pediatric Infectious Disease Society, serves as board member on the Emory University- Pediatric and Reproductive Environmental Health Scholars-Southeastern, the Center for Spatial Analytics of the Georgia Institute of Technology, and the American Academy of Pediatrics (Executive Board for Section on Infectious Diseases). L. C. I. has received travel/meeting support from the American Academy of Pediatrics and Moderna. L. A. J. has received funding from NIH for support for this study, funding from Pfizer to support a clinical trial and contract funding for research support from the CDC and the NIH, all through institution. L. A. J. also reports unpaid participation on Data Safety Monitoring Boards for NIH funded clinical trials. S. J. L. has received NIH grants through institution. A. F. L. has received grants from Merck, Gilead, and ViiV through institution as well as consulting fees from Vir Biotechnology. A. F. L. has also received travel support from Merck to attend a required investigator meeting, testing kits and supplies to support research study from Hologic, and medication donated by Mayne Pharma to support research study. M. M. has received funding from Division of Microbiology and Infectious Diseases for contract number 75N93021C00012. D. C. M. has received funding from NIH/75N93019C00050-21A: CIVICS A- Option 21A-DMID Trials of COVID-19 Vaccines. J. M. has received funding from Division of Microbiology and Infectious Diseases, contract number 75N93021C00012. A. N. has received support from NIH-NIAID, CEIRR (Centers of Excellence for Influenza Research and Response) and Gates Cambridge Trust as well as grants from NIH-NIAID R01. R. M. N. has received grants from Moderna and Janssen and travel/meeting support from Moderna. C. M. P. has received funding from NIAID UM1AI148684. R. M. P. has received funding from NIH DMID COVAIL as well as grants from Janssen, Moderna, and NIH through institution. N. G. R. has received research grants from Pfizer, Merck, Sanofi, Quidel, and Lilly through institution, consulting fees from Krog, honoraria as speaker for Virology education, and travel support from Sanofi. N. G. R. serves on safety committees for ICON and EMMES and is a member of the Moderna Advisory board. D. J. S. has received support from NIH-NIAID CEIRR, grants from NIH-NIAID R01, and travel support from NIH-NIAID CEIRR for NIH-related meetings. K. T. has received funding from Division of Microbiology and Infectious Diseases contract number 75N93021C00012. E. B. W. has received funding from Leidos Biomedical Research agreement number. 22CTA-DM0009 as well as grants from Pfizer, Moderna, Sequiris, Clinetic, and Najit Technologies, with payments made to institution. E. B. W. has also received honoraria as a speaker from College of Diplomates of the American Board of Pediatric Dentistry, consulting fees from Iliad Biotechnologies, and travel/meeting support from the American Academy of Pediatrics. E. B. W. serves as member of Vaxcyte Scientific Advisory board. P. L. W. has received subcontract funding from NIH for this study as well as NIH grant funding and contract funding from Pfizer through University of Iowa. P. L. W. has also received consulting fees from Pfizer and serves on safety/advisory board for Emmes Corporation. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The immune response to COVID-19 booster vaccinations during pregnancy for mothers and their newborns and the functional response of vaccine-induced antibodies against Omicron variants are not well characterized. We conducted a prospective, multicenter cohort study of participants vaccinated during pregnancy with primary or booster mRNA COVID-19 vaccines from July 2021 to January 2022 at 9 academic sites. We determined SARS-CoV-2 binding and live virus and pseudovirus neutralizing antibody (nAb) titers pre- and post-vaccination, and at delivery for both maternal and infant participants. Immune responses to ancestral and Omicron BA.1 SARS-CoV-2 strains were compared between primary and booster vaccine recipients in maternal sera at delivery and in cord blood, after adjusting for days since last vaccination. A total of 240 participants received either Pfizer or Moderna mRNA vaccine during pregnancy (primary 2-dose series: 167; booster dose: 73). Booster vaccination resulted in significantly higher binding and nAb titers, including to the Omicron BA.1 variant, in maternal serum at delivery and in cord blood compared to a primary 2-dose series (range 0.44-0.88 log 10 higher, p < 0.0001 for all comparisons). Live virus nAb to Omicron BA.1 were present at delivery in 9 % (GMT ID50 12.7) of Pfizer and 22 % (GMT ID50 14.7) of Moderna primary series recipients, and in 73 % (GMT ID50 60.2) of mRNA boosted participants (p < 0.0001), although titers were significantly lower than to the D614G strain. Transplacental antibody transfer was efficient for all regimens with median transfer ratio range: 1.55-1.77 for IgG, 1.00-1.78 for live virus nAb and 1.79-2.36 for pseudovirus nAb. COVID-19 mRNA vaccination during pregnancy elicited robust immune responses in mothers and efficient transplacental antibody transfer to the newborn. A booster dose during pregnancy significantly increased maternal and cord blood binding and neutralizing antibody levels, including against Omicron BA.1. Findings support the use of a booster dose of COVID-19 vaccine during pregnancy., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: F.M.M. is an investigator of pediatric studies of COVID-19 vaccines for Pfizer and for a pediatric remdesivir study conducted by Gilead Sciences, Inc; serves as investigator on projects supported by an NIH contract for a Vaccine Treatment and Evaluation Unit (VTEU), serves as member of the Data Safety monitoring Board (DSMB) for clinical trials conducted by Pfizer, Moderna, Meissa Vaccines, Virometix, and the NIH; and is a member of the American Academy of Pediatrics Section of Infectious Diseases (SOID), the Immunization Expert Group of the American College of Obstetrics and Gynecology (ACOG), and was co-Chair of the COVAX-CEPI Maternal Immunization Working Group. K.M.N. is a member of the World Health Organization (WHO) Strategic Advisory Group of Experts on Immunization, serves as co-investigator on an NIH contract for a Vaccine Treatment and Evaluation Unit (VTEU), serves as Co-Chair of the NIH COVID Prevention Network (CoVPN), and served as an investigator for Phase I/II Pfizer COVID-19 vaccine grant, with a grant to the institution, but no salary support. M.J.M. conducts laboratory research and clinical trials with contract funding for vaccines or MABs vs SARS-CoV-2 with Lilly, Pfizer, and Sanofi and receives personal fees for Scientific Advisory Board service from Merck, Meissa Vaccines, Inc. and Pfizer. M.S.S. served as an advisor for Moderna (ended December 2021) and is currently serving as an advisor for Ocugen, Inc. B.A.R. currently holds a position on a DSMB for clinical trials at Gilead Sciences, Inc. R.C.B. at Cincinnati Children’s Hospital receives research grant support for clinical trials from PATH, Astra Zeneca and Pfizer on which she serves as co-investigator. B.B. owns shares in HDT Bio Corp. J.S.G. receives research funds from NIH for Moderna KidCOVE study. R.M.N. is a paid advisor to Gilead and an investigator on NIH-funded trials of Moderna, Pfizer and Janssen vaccines. J.R-K is a medical speaker for Abbott Nutrition with the UIC team. A.R.F. holds research grants from Pfizer, Janssen, Merck, Cyanvac, Biofire Diagnostics and serves on the DSMB for Novavax. N.R. receives funds to conduct industry trials from Pfizer, Merck, and Sanofi-Pasteur and serves as a safety consultant for EMMES and ICON. R.W.F. Jr., MD has received funds to conduct industry trials from Pfizer, Moderna and Astra Zeneca, serves on advisory boards for Merck, Sanofi-Pasteur, Johnson and Johnson and Seqirus and serves on an ICON-sponsored DSMB for a C difficile study., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

As part of a multicenter study evaluating homologous and heterologous COVID-19 booster vaccines, we assessed the magnitude, breadth, and short-term durability of binding and pseudovirus-neutralizing antibody (PsVNA) responses following a single booster dose of NVX-CoV2373 in adults primed with either Ad26.COV2.S, mRNA-1273, or BNT162b2 vaccines. NVX-CoV2373 as a heterologous booster was immunogenic and associated with no safety concerns through Day 91. Fold-rises in PsVNA titers from baseline (Day 1) to Day 29 were highest for prototypic D614G variant and lowest for more recent Omicron sub-lineages BQ.1.1 and XBB.1. Peak humoral responses against all SARS-CoV-2 variants were lower in those primed with Ad26.COV2.S than with mRNA vaccines. Prior SARS CoV-2 infection was associated with substantially higher baseline PsVNA titers, which remained elevated relative to previously uninfected participants through Day 91. These data support the use of heterologous protein-based booster vaccines as an acceptable alternative to mRNA or adenoviral-based COVID-19 booster vaccines. This trial was conducted under ClinicalTrials.gov: NCT04889209., (© 2023. The Author(s).)

In this brief report, we compare the magnitude and durability of the serologic response of one versus two doses (separated by 56 days) of a variant vaccine (Moderna mRNA-1273 Beta/Omicron BA.1 bivalent vaccine) in adults.

In a randomized clinical trial, we compare early neutralizing antibody responses after boosting with bivalent SARS-CoV-2 mRNA vaccines based on either BA.1 or BA.4/BA.5 Omicron spike protein combined with wildtype spike. Responses against SARS-CoV-2 variants exhibited the greatest reduction in titers against currently circulating Omicron subvariants for both bivalent vaccines., Competing Interests: EJA has received grants from Pfizer, Moderna, Janssen, GSK, Sanofi, Micron, and Regeneron through institution as well as consulting fees from Pfizer, Janssen, Moderna, and Sanofi. EJA serves on safety/advisory boards for Sanofi, ACI Clinical/WCG and Kentucky Bioscience, Inc.ARB has received research support from NIH-NIAID, grants from Pfizer, Cyanvac, and Merck as well as consulting fees from Janssen and GSK.LRB has received grants from Wellcome Trust, Gates Foundation, NIH/Harvard Medical School through institution. Serves as member of DSMB for NIH and AMDAC for FDA. Dr Baden is involved in HIV and SARS-CoV-2 vaccine clinical trials conducted in collaboration with the NIH, HIV Vaccine Trials Network (HVTN), Covid Vaccine Prevention Network (CoVPN), International AIDS Vaccine Initiative (IAVI), Crucell/Janssen, Moderna, Military HIV Research Program (MHRP), the Gates Foundation, and Harvard Medical School.DJD has received a contract from Leidos Biomedical research to conduct the clinical trial through institution.ARF has received grants from Janssen, Pfizer, Merck, BioFire Diagnostics, and CyanVac through institution, consultant fees from Arrowhead and Icosavax, and honoraria as a speaker from Moderna and GlaxoSmithKline. ARF also serves on safety/advisory boards for Novavax and received travel/meeting support from GlaxoSmithKline.SEF has received f unding from Leidos to Saint Louis University to conduct Protocol DMID22-0004.DNF has as a contract from CDC and is the site PI for clinical trials from Gilead, Regeneron and MetroBiotech LLC. She is the PI on one investigator-initiated award from Gilead and the co-PI on another investigator initiated award from Gilead. DNF served on an HBV Advisory board for Gilead in 2021 and received payment for expert testimony not related to COVID in 2022.PAG has received funding for COVAIL clinical trial. PAG has also received consulting fees from Janssen Vaccines.LCI has received support for the present manuscript from NIH-NIAID/DMID, Moderna, Pfizer, and Sanofi. LCI has also received grants from GSK, Merck, Sharpe & Dohme Corp, CDC, Novavax, AHRQ, and NIH/NLM/NIMHD as well as consulting fees from Moderna, CDC, and Pediatric Emergency Medicine Associates, LLC. LCI has received honoraria as a speaker from American Academy of Pediatrics, Rockefeller University, and American Academy of Pediatrics- Georgia Chapter. LCI Serves on Data Safety Monitoring for NIH-Phase 2 Vaccine Trial for Monkeypox, Moderna Scientific Advisory Board- North America, and CoVID-19 Task Force, Georgia. LCI has a leadership role in the Pediatric Infectious Disease Society and serves as board member on the Emory University- Pediatric and Reproductive Environmental Health Scholars-Southeastern, the Center for Spatial Analytics of the Georgia Institute of Technology, and the American Academy of Pediatrics (Executive Board for Section on Infectious Diseases). LCI has received travel/meeting support from the American Academy of Pediatrics and Moderna.LAJ has received funding from NIH for support for this study, funding from Pfizer to support a clinical trial and contract funding for research support from the CDC and the NIH, all through institution. LAJ also reports unpaid participation on Data Safety Monitoring Boards for NIH funded clinical trials.SJL has received NIH grants through institution.AFL has received grants from Merck, Gilead and, Viiv through institution as well as consulting fees from Vir Biotechnology. AFL has also received travel support from Merck to attend a required investigator meeting, testing kits and supplies to support research study from Hologic, and medication donated by Mayne Pharma to support research study.MM has received funding from Division of Microbiology and Infectious Diseases for contract # 75N93021C00012.DCM has received funding from NIH/75N93019C00050-21A: CIVICS A- Option 21A-DMID Trials of COVID-19 Vaccines.JM has received funding from Division of Microbiology and Infectious Diseases, contract # 75N93021C00012.AN has received support from NIH-NIAID, CEIRR (Centers of Excellence for Influenza Research and Response) and Gates Cambridge Trust as well as grants from NIH-NIAID R01.RMN has received grants from Moderna and Janssen and travel/meeting support from Moderna.CMP has received funding from NIAID UM1AI148684.RMP has received funding from NIH DMID COVAIL as well as grants from Janssen, Moderna and NIH through institution.NGR has received research grants from Pfizer, Merck, Sanofi, Quidel and Lilly through institution, consulting fees from Krog, honoraria as speaker for Virology education, and travel support from Sanofi. NGR serves on safety committees for ICON and EMMES and is a member of the Moderna Advisory board.DJS has received support from NIH-NIAID CEIRR , grants from NIH-NIAID R01, and travel support from NIH-NIAID CEIRR for NIH-related meetings.KT has received funding from Division of Microbiology and Infectious Diseases contract # 75N93021C00012.EBW has received funding from Leidos Biomedical Research AGREEMENT NO. 22CTA-DM0009 as well as grants from Pfizer, Moderna, Sequiris, Clinetic, and Najit Technologies, with payments made to institution. EBW has also received honoraria as a speaker from College of Diplomates of the American Board of Pediatric Dentistry, consulting fees from Iliad Biotechnologies, and travel/meeting support from the American Academy of Pediatrics. EBW serves as member of Vaxcyte Scientific Advisory board.PLW has received subcontract funding from NIH for this study as well as NIH grant funding and contract funding from Pfizer through University of Iowa. PLW has also received consulting fees from Pfizer and serves on safety/advisory board for Emmes Corporation.The following group has no conflicts to declare: RLA, TMB, SMM, MB, MKM, JHB , SC, ACK, CL, PCR, RR, JAW.

Numerous safe and effective coronavirus disease 2019 vaccines have been developed worldwide that use various delivery technologies and engineering strategies. We show here that vaccines containing prefusion-stabilizing S mutations elicit antibody responses in humans with enhanced recognition of S and the S 1 subunit relative to postfusion S as compared with vaccines lacking these mutations or natural infection. Prefusion S and S 1 antibody binding titers positively and equivalently correlated with neutralizing activity, and depletion of S 1 -directed antibodies completely abrogated plasma neutralizing activity. We show that neutralizing activity is almost entirely directed to the S 1 subunit and that variant cross-neutralization is mediated solely by receptor binding domain-specific antibodies. Our data provide a quantitative framework for guiding future S engineering efforts to develop vaccines with higher resilience to the emergence of variants than current technologies.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant of concern comprises several sublineages, with BA.2 and BA.2.12.1 having replaced the previously dominant BA.1 and with BA.4 and BA.5 increasing in prevalence worldwide. We show that the large number of Omicron sublineage spike mutations leads to enhanced angiotensin-converting enzyme 2 (ACE2) binding, reduced fusogenicity, and severe dampening of plasma neutralizing activity elicited by infection or seven clinical vaccines relative to the ancestral virus. Administration of a homologous or heterologous booster based on the Wuhan-Hu-1 spike sequence markedly increased neutralizing antibody titers and breadth against BA.1, BA.2, BA.2.12.1, BA.4, and BA.5 across all vaccines evaluated. Our data suggest that although Omicron sublineages evade polyclonal neutralizing antibody responses elicited by primary vaccine series, vaccine boosters may provide sufficient protection against Omicron-induced severe disease.

The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibits reduced susceptibility to vaccine-induced neutralizing antibodies, requiring a boost to generate protective immunity. We assess the magnitude and short-term durability of neutralizing antibodies after homologous and heterologous boosting with mRNA and Ad26.COV2.S vaccines. All prime-boost combinations substantially increase the neutralization titers to Omicron, although the boosted titers decline rapidly within 2 months from the peak response compared with boosted titers against the prototypic D614G variant. Boosted Omicron neutralization titers are substantially higher for homologous mRNA vaccine boosting, and for heterologous mRNA and Ad26.COV2.S vaccine boosting, compared with homologous Ad26.COV2.S boosting. Homologous mRNA vaccine boosting generates nearly equivalent neutralizing activity against Omicron sublineages BA.1, BA.2, and BA.3 but modestly reduced neutralizing activity against BA.2.12.1 and BA.4/BA.5 compared with BA.1. These results have implications for boosting requirements to protect against Omicron and future variants of SARS-CoV-2. This trial was conducted under ClincalTrials.gov: NCT04889209., Competing Interests: Declaration of interests R.L.A., C.D.I., C.M.P., D.S., R.P.C., M.E.D., A.E., H.M.E.S., R.E.R., M.B., A.C.K., T.M.B., D.D., R.N.C., J.I.A., S.C., J.A.Z., S.U.N., E.R.B., and D.J.P. report no competing interests. K.E.L. receives grant awards from Pfizer, Inc., COVID-19 vaccine research. L.A.J.’s institution receives grant funding from NIH and CDC for vaccine-related assessments, including those of COVID-19 vaccines. A.R.B. has grant funding from Pfizer, Janssen, Merck, and Cyanvac for non-COVID-19-related work and serves as a consultant for GSK and Janssen. C.A.R.'s institution has received funds to conduct clinical research from the National Institutes of Health, CDC, BioFire, Inc., Genentech, GSK, Janssen, MedImmune, Merck, Micron, Moderna, Novavax, PaxVax, Pfizer, Regeneron, and Sanofi-Pasteur. She is co-inventor of patented RSV vaccine technology, which has been licensed to Meissa Vaccines, Inc. J.M.M. has served as a consultant for Merck, Sharp, and Dohme for non-Covid-related work. C.J. receives funding from the Bill and Melinda Gates Foundation, NIH, and CDC, consults for Gilead and Abbvie, serves on a DSMB for MedPace, and receives royalties from UpToDate. M.J.M. has laboratory research and clinical trials contracts for vaccines or MAB versus SARS-CoV-2 with Lilly, Pfizer (exclusive of the current work), and Sanofi and personal fees for Scientific Advisory Board service from Merck, Meissa Vaccines, Inc., and Pfizer. R.C.B. receives funding for vaccine trials from Path Nipah and Pfizer. R.W.F. receives funding to perform clinical trials from Pfizer, Moderna, Astra Zeneca, and Emergent Health, and he serves on advisory boards for Johnson & Johnson, Merck, Sanofi Pasteur, and Seqirus. S.E. receives funding to her institution from Sanofi Pasteur for a non-COVID-19 vaccine study. K.M.N. holds a grant from Pfizer, without salary support, for a COVID-19 vaccine study and salary support from the National Institutes of Health (NIH) for work on multiple COVID-19 vaccine trials. D.S.S. is supported by grant awards from NIH/NIAID. P.C.R. and J.H.B. report a pending US patent application no. 63/025918 entitled “Coronavirus RNA vaccines and methods of use.” D.C.M. receives funding from NIH and Moderna for laboratory studies of COVID-19 vaccine antibody responses. M.S.S. receives funding from Moderna, Inc., and Ocugen. D.C.M. receives funding from Moderna, Inc., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Protection from SARS-CoV-2 vaccines wanes over time and is compounded by emerging variants including Omicron subvariants. This study evaluated safety and immunogenicity of SARS-CoV-2 variant vaccines., Methods: This phase 2 open-label, randomized trial enrolled healthy adults previously vaccinated with a SARS-CoV-2 primary series and a single boost. Eligible participants were randomized to one of six Moderna COVID19 mRNA vaccine arms (50µg dose): Prototype (mRNA-1273), Omicron BA.1+Beta (1 or 2 doses), Omicron BA.1+Delta, Omicron BA.1 monovalent, and Omicron BA.1+Prototype. Neutralization antibody titers (ID 50 ) were assessed for D614G, Delta, Beta and Omicron BA.1 variants and Omicron BA.2.12.1 and BA.4/BA.5 subvariants 15 days after vaccination., Results: From March 30 to May 6, 2022, 597 participants were randomized and vaccinated. Median age was 53 years, and 20% had a prior SARS-CoV-2 infection. All vaccines were safe and well-tolerated. Day 15 geometric mean titers (GMT) against D614G were similar across arms and ages, and higher with prior infection. For uninfected participants, Day 15 Omicron BA.1 GMTs were similar across Omicron-containing vaccine arms (3724-4561) and higher than Prototype (1,997 [95%CI:1,482-2,692]). The Omicron BA.1 monovalent and Omicron BA.1+Prototype vaccines induced a geometric mean ratio (GMR) to Prototype for Omicron BA.1 of 2.03 (97.5%CI:1.37-3.00) and 1.56 (97.5%CI:1.06-2.31), respectively. A subset of samples from uninfected participants in four arms were also tested in a different laboratory at Day 15 for neutralizing antibody titers to D614G and Omicron subvariants BA.1, BA.2.12.2 and BA.4/BA.5. Omicron BA.4/BA.5 GMTs were approximately one third BA.1 GMTs (Prototype 517 [95%CI:324-826] vs. 1503 [95%CI:949-2381]; Omicron BA.1+Beta 628 [95%CI:367-1,074] vs. 2125 [95%CI:1139-3965]; Omicron BA.1+Delta 765 [95%CI:443-1,322] vs. 2242 [95%CI:1218-4128] and Omicron BA.1+Prototype 635 [95%CI:447-903] vs. 1972 [95%CI:1337-2907)., Conclusions: Higher Omicron BA.1 titers were observed with Omicron-containing vaccines compared to Prototype vaccine and titers against Omicron BA.4/BA.5 were lower than against BA.1 for all candidate vaccines., Clinicaltrialsgov: NCT05289037.

Importance: COVID-19 vaccination is recommended during pregnancy for the protection of the mother. Little is known about the immune response to booster vaccinations during pregnancy., Objective: To measure immune responses to COVID-19 primary and booster mRNA vaccination during pregnancy and transplacental antibody transfer to the newborn., Design: Prospective cohort study of pregnant participants enrolled from July 2021 to January 2022, with follow up through and up to 12 months after delivery., Setting: Multicenter study conducted at 9 academic sites., Participants: Pregnant participants who received COVID-19 vaccination during pregnancy and their newborns., Exposures: Primary or booster COVID-19 mRNA vaccination during pregnancy., Main Outcomes and Measures: SARS-CoV-2 binding and neutralizing antibody (nAb) titers after primary or booster COVID-19 mRNA vaccination during pregnancy and antibody transfer to the newborn. Immune responses were compared between primary and booster vaccine recipients in maternal sera at delivery and in cord blood, after adjusting for days since last vaccination., Results: In this interim analysis, 167 participants received a primary 2-dose series and 73 received a booster dose of mRNA vaccine during pregnancy. Booster vaccination resulted in significantly higher binding and nAb titers, including to the Omicron BA.1 variant, in maternal serum at delivery and cord blood compared to a primary 2-dose series (range 0.55 to 0.88 log 10 higher, p<0.0001 for all comparisons). Although levels were significantly lower than to the prototypical D614G variant, nAb to Omicron were present at delivery in 9% (GMT ID50 12.7) of Pfizer and 22% (GMT ID50 14.7) of Moderna recipients, and in 73% (GMT ID50 60.2) of boosted participants (p<0.0001). Transplacental antibody transfer was efficient regardless of vaccination regimen (median transfer ratio range: 1.55-1.77 for binding IgG and 1.00-1.78 for nAb)., Conclusions and Relevance: COVID-19 mRNA vaccination during pregnancy elicited robust immune responses in mothers and efficient transplacental antibody transfer to the newborn. A booster dose during pregnancy significantly increased maternal and cord blood antibody levels, including against Omicron.Findings support continued use of COVID-19 vaccines during pregnancy, including booster doses., Trial Registration: clinical trials.gov; Registration Number: NCT05031468 ; https://clinicaltrials.gov/ct2/show/NCT05031468., Key Points: Question: What is the immune response after COVID-19 booster vaccination during pregnancy and how does receipt of a booster dose impact transplacental antibody transfer to the newborn? Findings: Receipt of COVID-19 mRNA vaccines during pregnancy elicited robust binding and neutralizing antibody responses in the mother and in the newborn. Booster vaccination during pregnancy elicited significantly higher antibody levels in mothers at delivery and cord blood than 2-dose vaccination, including against the Omicron BA.1 variant. Meaning: COVID-19 vaccines, especially booster doses, should continue to be strongly recommended during pregnancy.

Background: Pregnant women were excluded from investigational trials of COVID-19 vaccines. Limited data are available to inform pregnant and postpartum women on their decisions to receive a COVID-19 vaccine., Methods: The goal of this observational, prospective cohort study is to evaluate the immunogenicity and safety of various Emergency Use Authorization (EUA) or licensed COVID-19 vaccines administered to pregnant or lactating women and describe the transplacental antibody transfer and kinetics of antibodies in mothers and infants. The study is adaptive, allowing additional groups to be added as new vaccines or vaccine regimens are authorized. Up to 20 clinical research institutions in the United States (U.S.) will be included. Approximately 200 pregnant women and 65 postpartum women will be enrolled per EUA or licensed COVID-19 vaccine formulation in the U.S. This study will include pregnant and postpartum women of all ages with and without chronic medical conditions. Their infants will be enrolled and followed beginning at birth in the pregnant cohort and beginning at the earliest possible time point in the postpartum cohort. Blood samples will be collected for immunogenicity outcomes and pregnancy and birth outcomes assessed among women and infants. Primary analyses will be descriptive and done by vaccine type and/or platform., Discussion: Given the long-standing and legitimate challenges of enrolling pregnant individuals into clinical trials early in the vaccine development pipeline, this study protocol describes our current study and provides a template to inform the collection of data for pregnant individuals receiving COVID-19 or other vaccines., Trial Registration: NCT05031468 ., (© 2022. The Author(s).)

Antigen-specific T RM persist and protect against skin or female reproductive tract (FRT) HSV infection. As the pathogenesis of HSV differs between humans and model organisms, we focus on humans with well-characterized recurrent genital HSV-2 infection. Human CD8+ T RM persisting at sites of healed human HSV-2 lesions have an activated phenotype but it is unclear if T RM can be cultivated in vitro . We recovered HSV-specific T RM from genital skin and ectocervix biopsies, obtained after recovery from recurrent genital HSV-2, using ex vivo activation by viral antigen. Up to several percent of local T cells were HSV-reactive ex vivo. CD4 and CD8 T cell lines were up to 50% HSV-2-specific after sorting-based enrichment. CD8 T RM displayed HLA-restricted reactivity to specific HSV-2 peptides with high functional avidities. Reactivity to defined peptides persisted locally over several month and was quite subject-specific. CD4 T RM derived from biopsies, and from an extended set of cervical cytobrush specimens, also recognized diverse HSV-2 antigens and peptides. Overall we found that HSV-2-specific T RM are abundant in the FRT between episodes of recurrent genital herpes and maintain competency for expansion. Mucosal sites are accessible for clinical monitoring during immune interventions such as therapeutic vaccination., Competing Interests: DK, CP, and LC are co-inventors of patents concerning HSV vaccines owned and managed by their institutions. DMK receives research funding from Sanofi Pasteur concerning testing samples from a clinical trial of an HSV vaccine. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Koelle, Dong, Jing, Laing, Zhu, Jin, Selke, Wald, Varon, Huang, Johnston, Corey and Posavad.)

Background: Although the three vaccines against coronavirus disease 2019 (Covid-19) that have received emergency use authorization in the United States are highly effective, breakthrough infections are occurring. Data are needed on the serial use of homologous boosters (same as the primary vaccine) and heterologous boosters (different from the primary vaccine) in fully vaccinated recipients., Methods: In this phase 1-2, open-label clinical trial conducted at 10 sites in the United States, adults who had completed a Covid-19 vaccine regimen at least 12 weeks earlier and had no reported history of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection received a booster injection with one of three vaccines: mRNA-1273 (Moderna) at a dose of 100 μg, Ad26.COV2.S (Johnson & Johnson-Janssen) at a dose of 5×10 10 virus particles, or BNT162b2 (Pfizer-BioNTech) at a dose of 30 μg. The primary end points were safety, reactogenicity, and humoral immunogenicity on trial days 15 and 29., Results: Of the 458 participants who were enrolled in the trial, 154 received mRNA-1273, 150 received Ad26.COV2.S, and 153 received BNT162b2 as booster vaccines; 1 participant did not receive the assigned vaccine. Reactogenicity was similar to that reported for the primary series. More than half the recipients reported having injection-site pain, malaise, headache, or myalgia. For all combinations, antibody neutralizing titers against a SARS-CoV-2 D614G pseudovirus increased by a factor of 4 to 73, and binding titers increased by a factor of 5 to 55. Homologous boosters increased neutralizing antibody titers by a factor of 4 to 20, whereas heterologous boosters increased titers by a factor of 6 to 73. Spike-specific T-cell responses increased in all but the homologous Ad26.COV2.S-boosted subgroup. CD8+ T-cell levels were more durable in the Ad26.COV2.S-primed recipients, and heterologous boosting with the Ad26.COV2.S vaccine substantially increased spike-specific CD8+ T cells in the mRNA vaccine recipients., Conclusions: Homologous and heterologous booster vaccines had an acceptable safety profile and were immunogenic in adults who had completed a primary Covid-19 vaccine regimen at least 12 weeks earlier. (Funded by the National Institute of Allergy and Infectious Diseases; DMID 21-0012 ClinicalTrials.gov number, NCT04889209.)., (Copyright © 2022 Massachusetts Medical Society.)

The SARS-CoV-2 Omicron variant of concern comprises three sublineages designated BA.1, BA.2, and BA.3, with BA.2 steadily replacing the globally dominant BA.1. We show that the large number of BA.1 and BA.2 spike mutations severely dampen plasma neutralizing activity elicited by infection or seven clinical vaccines, with cross-neutralization of BA.2 being consistently more potent than that of BA.1, independent of the vaccine platform and number of doses. Although mRNA vaccines induced the greatest magnitude of Omicron BA.1 and BA.2 plasma neutralizing activity, administration of a booster based on the Wuhan-Hu-1 spike sequence markedly increased neutralizing antibody titers and breadth against BA.1 and BA.2 across all vaccines evaluated. Our data suggest that although BA.1 and BA.2 evade polyclonal neutralizing antibody responses, current vaccine boosting regimens may provide sufficient protection against Omicron-induced disease.

Vaccine-induced neutralizing antibodies (nAbs) are key biomarkers considered to be associated with vaccine efficacy. In United States government-sponsored phase 3 efficacy trials of COVID-19 vaccines, nAbs are measured by two different validated pseudovirus-based SARS-CoV-2 neutralization assays, with each trial using one of the two assays. Here we describe and compare the nAb titers obtained in the two assays. We observe that one assay consistently yielded higher nAb titers than the other when both assays were performed on the World Health Organization's anti-SARS-CoV-2 immunoglobulin International Standard, COVID-19 convalescent sera, and mRNA-1273 vaccinee sera. To overcome the challenge this difference in readout poses in comparing/combining data from the two assays, we evaluate three calibration approaches and show that readouts from the two assays can be calibrated to a common scale. These results may aid decision-making based on data from these assays for the evaluation and licensure of new or adapted COVID-19 vaccines., (© 2021. The Author(s).)

Background: While Coronavirus disease 2019 (Covid-19) vaccines are highly effective, breakthrough infections are occurring. Booster vaccinations have recently received emergency use authorization (EUA) for certain populations but are restricted to homologous mRNA vaccines. We evaluated homologous and heterologous booster vaccination in persons who had received an EUA Covid-19 vaccine regimen., Methods: In this phase 1/2 open-label clinical trial conducted at ten U.S. sites, adults who received one of three EUA Covid-19 vaccines at least 12 weeks prior to enrollment and had no reported history of SARS-CoV-2 infection received a booster injection with one of three vaccines (Moderna mRNA-1273 100-μg, Janssen Ad26.COV2.S 5×10 10 virus particles, or Pfizer-BioNTech BNT162b2 30-μg; nine combinations). The primary outcomes were safety, reactogenicity, and humoral immunogenicity on study days 15 and 29., Results: 458 individuals were enrolled: 154 received mRNA-1273, 150 received Ad26.CoV2.S, and 153 received BNT162b2 booster vaccines. Reactogenicity was similar to that reported for the primary series. Injection site pain, malaise, headache, and myalgia occurred in more than half the participants. Booster vaccines increased the neutralizing activity against a D614G pseudovirus (4.2-76-fold) and binding antibody titers (4.6-56-fold) for all combinations; homologous boost increased neutralizing antibody titers 4.2-20-fold whereas heterologous boost increased titers 6.2-76-fold. Day 15 neutralizing and binding antibody titers varied by 28.7-fold and 20.9-fold, respectively, across the nine prime-boost combinations., Conclusion: Homologous and heterologous booster vaccinations were well-tolerated and immunogenic in adults who completed a primary Covid-19 vaccine regimen at least 12 weeks earlier.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mutations may diminish vaccine-induced protective immune responses, particularly as antibody titers wane over time. Here, we assess the effect of SARS-CoV-2 variants B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), B.1.429 (Epsilon), B.1.526 (Iota), and B.1.617.2 (Delta) on binding, neutralizing, and angiotensin-converting enzyme 2 (ACE2)–competing antibodies elicited by the messenger RNA (mRNA) vaccine mRNA-1273 over 7 months. Cross-reactive neutralizing responses were rare after a single dose. At the peak of response to the second vaccine dose, all individuals had responses to all variants. Binding and functional antibodies against variants persisted in most subjects, albeit at low levels, for 6 months after the primary series of the mRNA-1273 vaccine. Across all assays, B.1.351 had the lowest antibody recognition. These data complement ongoing studies to inform the potential need for additional boost vaccinations.

Vaccine-induced neutralizing antibodies (nAbs) are key biomarkers considered to be associated with vaccine efficacy. In United States Government-sponsored phase 3 efficacy trials of COVID-19 vaccines, nAbs are measured by two different validated pseudovirus-based SARS-CoV-2 neutralization assays, with each trial using one of the two assays. Here we describe and compare the nAb titers obtained in the two assays. We observe that one assay consistently yielded higher nAb titers than the other when both assays were performed on the World Health Organization’s anti-SARS-CoV-2 immunoglobulin International Standard, COVID-19 convalescent sera, and mRNA-1273 vaccinee sera. To overcome the challenge this difference in readout poses in comparing/combining data from the two assays, we evaluate three calibration approaches and show that readouts from the two assays can be calibrated to a common scale. These results may aid decision-making based on data from these assays for the evaluation and licensure of new or adapted COVID-19 vaccines.

Vaccine-induced neutralizing antibodies (nAbs) are key biomarkers considered to be associated with vaccine efficacy. In United States Government-sponsored phase 3 efficacy trials of COVID-19 vaccines, nAbs are measured by two different validated pseudovirus-based SARS-CoV-2 neutralization assays, with each trial using one of the two assays. Here we describe and compare the nAb titers obtained in the two assays. We observe that one assay consistently yielded higher nAb titers than the other when both assays were performed on the World Health Organization’s anti-SARS-CoV-2 immunoglobulin International Standard, COVID-19 convalescent sera, and mRNA-1273 vaccinee sera. To overcome the challenge this difference in readout poses in comparing/combining data from the two assays, we evaluate three calibration approaches and show that readouts from the two assays can be calibrated to a common scale. These results may aid decision-making based on data from these assays for the evaluation and licensure of new or adapted COVID-19 vaccines.

Local mucosal cellular immunity is critical in providing protection from HSV-2. To characterize and quantify HSV-2-reactive mucosal T cells, lymphocytes were isolated from endocervical cytobrush and biopsy specimens from 17 HSV-2-infected women and examined ex vivo for the expression of markers associated with maturation and tissue residency and for functional T-cell responses to HSV-2. Compared with their circulating counterparts, cervix-derived CD4+ and CD8+ T cells were predominantly effector memory T cells (CCR7-/CD45RA-) and the majority expressed CD69, a marker of tissue residency. Co-expression of CD103, another marker of tissue residency, was highest on cervix-derived CD8+ T cells. Functional HSV-2 reactive CD4+ and CD8+ T-cell responses were detected in cervical samples and a median of 17% co-expressed CD103. HSV-2-reactive CD4+ T cells co-expressed IL-2 and were significantly enriched in the cervix compared with blood. This first direct ex vivo documentation of local enrichment of HSV-2-reactive T cells in the human female genital mucosa is consistent with the presence of antigen-specific tissue-resident memory T cells. Ex vivo analysis of these T cells may uncover tissue-specific mechanisms of local control of HSV-2 to assist the development of vaccine strategies that target protective T cells to sites of HSV-2 infection.

The Alphaherpesvirinae subfamily includes HSV types 1 and 2 and the sequence-divergent pathogen varicella zoster virus (VZV). T cells, controlled by TCR and HLA molecules that tolerate limited epitope amino acid variation, might cross-react between these microbes. We show that memory PBMC expansion with either HSV or VZV enriches for CD4 T cell lines that recognize the other agent at the whole-virus, protein, and peptide levels, consistent with bidirectional cross-reactivity. HSV-specific CD4 T cells recovered from HSV-seronegative persons can be explained, in part, by such VZV cross-reactivity. HSV-1-reactive CD8 T cells also cross-react with VZV-infected cells, full-length VZV proteins, and VZV peptides, as well as kill VZV-infected dermal fibroblasts. Mono- and cross-reactive CD8 T cells use distinct TCRB CDR3 sequences. Cross-reactivity to VZV is reconstituted by cloning and expressing TCRA/TCRB receptors from T cells that are initially isolated using HSV reagents. Overall, we define 13 novel CD4 and CD8 HSV-VZV cross-reactive epitopes and strongly imply additional cross-reactive peptide sets. Viral proteins can harbor both CD4 and CD8 HSV/VZV cross-reactive epitopes. Quantitative estimates of HSV/VZV cross-reactivity for both CD4 and CD8 T cells vary from 10 to 50%. Based on these findings, we hypothesize that host herpesvirus immune history may influence the pathogenesis and clinical outcome of subsequent infections or vaccinations for related pathogens and that cross-reactive epitopes and TCRs may be useful for multi-alphaherpesvirus vaccine design and adoptive cellular therapy., (Copyright © 2016 by The American Association of Immunologists, Inc.)

Relatively little is known about the human T-cell response to herpes simplex virus type 2 (HSV-2) in the female genital tract, a major site of heterosexual HSV-2 acquisition, transmission, and reactivation. In order to understand the role of local mucosal immunity in HSV-2 infection, T-cell lines were expanded from serial cervical cytobrush samples from 30 HSV-2-infected women and examined for reactivity to HSV-2. Approximately 3% of the CD3+ T cells isolated from the cervix were HSV-2 specific and of these, a median of 91.3% were CD4+, whereas a median of 3.9% were CD8+. HSV-2-specific CD4+ T cells expanded from the cervix were not only more frequent than CD8+ T cells but also exhibited greater breadth in terms of antigenic reactivity. T cells directed at the same HSV-2 protein were often detected in serial cervical cytobrush samples and in blood. Thus, broad and persistent mucosal T-cell responses to HSV-2 were detected in the female genital tract of HSV-2+ women suggesting that these cells are resident at the site of HSV-2 infection. Understanding the role of these T cells at this biologically relevant site will be central to the elucidation of adaptive immune mechanisms involved in controlling HSV-2 disease.

Background: The need for an HSV-2 vaccine is great considering the increasing prevalence of HSV-2 despite the widespread use of antiviral drugs. Human clinical trials of HSV-2 vaccines that elicit neutralizing antibodies have proven to be only partially effective suggesting that induction of effective T cell responses to HSV-2 is also a critical component to an efficacious vaccine. A sensitive and specific assay to measure HSV-specific T cell responses is a necessary part of vaccine development and thus we undertook the development of an interferon-γ (IFN-γ) ELISPOT assay to measure T cell responses to HSV-2., Methods: PBMC from HSV-seronegative (HSVneg) (n=35), HSV-1-seropositive (HSV-1+/2-) (n=20) and HSV-2-seropositive (HSV-2+) subjects (n=26) were screened by IFN-γ ELISPOT for T cell responses using 34 peptide pools representing 16 HSV-2 proteins including mostly virion and immediate-early (IE) proteins., Results: Overall, 85% of HSV-2+ subjects had a positive response to the HSV-2 peptide pools and on average, HSV-2+ subjects responded to 3 peptide pools (range 1-10). The most frequent responses were to gD-2, UL39, UL46, ICP0, UL49, gB-2, and ICP4. In contrast, only 2 of 35 (6%) HSVneg subjects had detectable T cell responses and in both cases, responses were of low magnitude relative to responses in HSV-2+ subjects and were directed at a single peptide pool. The response rate to the HSV-2 peptide pools in HSV-1+/2- subjects was 40% suggesting that the HSV-2 peptide pools contain a significant number of type-common T cell epitopes. The IFN-γ ELISPOT assay detected CD4 and CD8 T cells directed at HSV-2 peptides as confirmed by intracellular cytokine staining and flow cytometry., Conclusion: We have developed a quantitative IFN-γ ELISPOT assay that detects both CD4 and CD8 T cells to HSV-2 peptides. This assay does not require large quantities of PBMC to generate dendritic cells for T cell stimulation, making it an ideal assay for monitoring the immunogenicity of candidate HSV-2 vaccines designed to elicit T cell responses to HSV-2 specific epitopes., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

In 2003, we described a small cohort of subjects (n = 6) who possessed no detectable serum Abs to HSV-1 or HSV-2 and no clinical or virological evidence of mucosal HSV infection yet possessed consistently detectable HSV-specific T cell responses measured primarily by lymphoproliferative (LP) and CTL assays to whole HSV-2 Ag. We termed these persons immune seronegative (IS). This report characterizes the T cell responses in 22 IS subjects largely recruited from studies of HSV-seronegative subjects in ongoing sexual relationships with HSV-2-seropositive (HSV-2(+)) partners using pools of overlapping peptides spanning 16 immuno-prevalent HSV-2 proteins. Overall, 77% of IS subjects had HSV-specific LP responses, 85% had IFN-gamma ELISPOT responses to at least one HSV-2 peptide pool, and 55% had both LP and IFN-gamma ELISPOT responses. In some cases, IFN-gamma ELISPOT responses were in excess of 500 spot-forming cells per 10(6) PBMCs and persisted for over 5 y. Although HSV-2(+) subjects (n = 40) had frequent responses to glycoproteins and tegument and immediate-early (IE) proteins of HSV-2, T cell responses in IS subjects were directed primarily at UL39 and the IE proteins ICP4 and ICP0. These data suggest that the antigenic repertoire of T cells in IS subjects is skewed compared with that of HSV-2(+) subjects and that IS subjects had more frequent T cell responses to IE proteins and infrequent T cell responses to virion components. Understanding the mechanism(s) by which such responses are elicited may provide important insights in developing novel strategies for preventing acquisition of sexually acquired HSV-2.

We conducted a double-blind, vehicle-controlled, dose escalation safety and immunogenicity trial of a candidate herpes simplex virus type 2 (HSV-2) surface glycoprotein D2 (gD2) DNA vaccine administered by use of a needle-free device. Sixty-two healthy adults were randomized using a 4:1 vaccine-to-placebo ratio. Half of the participants were HSV-1 seronegative, and all were HSV-2 seronegative. Vaccine doses included 100 microg, 300 microg, 1,000 microg or 3,000 microg of a plasmid expressing the gD2 protein. Subjects received vaccine at 0, 4, 8, and 24 weeks. Some subjects received an additional 1,000-microg boost at 52 weeks. We found that the vaccine was safe and well tolerated, with most adverse events being local site reactions. No dose-limiting toxicities were observed. gD2-specific cytotoxic T-lymphocyte and lymphoproliferation responses were detected 2 weeks after the third vaccine injection in one of four HSV-1-seronegative, HSV-2-seronegative participants who received 3,000 microg of vaccine. A DNA-based vaccination strategy against HSV-2 appears to be safe and may generate a vaccine-specific cellular immune response, but high vaccine doses are likely needed to elicit an immune response in most vaccinees.

The effect of highly active antiretroviral therapy (HAART) on control of herpes simplex virus (HSV) in human immunodeficiency virus (HIV) type 1-infected subjects is not known. Among 28 HAART-treated and 49 untreated subjects with HIV-1 and HSV-2 infections, mucosal HSV shedding (median, 18% and 29% of days positive for HSV DNA, respectively; P=.08) and HSV DNA level (median, 56,250 and 50,000 copies/mL, respectively; P=.20) were similar. Treated subjects reported significantly fewer days with HSV lesions, compared with untreated subjects (2.8% vs. 11.3% of days, respectively; P=.001). Thus, mucosal HSV shedding and HSV-2 reactivation were still frequent among treated subjects, even though HAART was associated with fewer days with HSV lesions.

Numerous cell-to-cell signals tightly regulate CTL function. Human fibroblasts infected with HSV type 1 or 2 can generate such a signal and inactivate human CTL. Inactivated CTL lose their ability to release cytotoxic granules and synthesize cytokines when triggered through the TCR. Inactivation requires cell-to-cell contact between CTL and HSV-infected cells. However, inactivated CTL are not infected with HSV. The inactivation of CTL is sustainable, as CTL function remains impaired when the CTL are removed from the HSV-infected cells. IL-2 treatment does not alter inactivation, and the inactivated phenotype is not transferable between CTL, distinguishing this phenotype from traditional anergy and T regulatory cell models. CTL inactivated by HSV-infected cells are not apoptotic, and the inactivated state can be overcome by phorbol ester stimulation, suggesting that inactivated CTL are viable and that the signaling block is specific to the TCR. HSV-infected cells require the expression of U(S)3, a viral protein kinase, to transmit the inactivating signal. Elucidation of the molecular nature of this signaling pathway may allow targeted manipulation of CTL function.

During the course of investigating T cell responses to HSV among volunteers entering trials of investigational genital herpes vaccines, 6 of the 24 immunocompetent subjects with no prior history of oral/labial or genital herpes possessed HSV-specific T cell immunity but, by multiple determinants of even the most sensitive serological assays, remained seronegative to HSV-1 and -2. Of these six immune seronegative (IS; HSV-seronegative with HSV-specific T cell responses) subjects, two had transient HSV-specific T cell responses, while four had CD4(+) and CD8(+) T cell responses directed at HSV that persisted for up to 4 years. CD4(+) T cell clones were isolated that recognized and had high binding affinities to epitopes in HSV-2 tegument proteins. All six IS subjects had potential sexual exposure to an HSV-2-infected sexual partner. Oral and genital mucosal secretions were sampled and tested for the presence of infectious HSV and HSV DNA. No evidence of HSV was detected in >1500 samples obtained from these IS subjects. The identification of persistent T cell responses to HSV in seronegative subjects is a novel finding in the herpesvirus field and suggests either undetected infection or acquired immunity in the absence of infection. Understanding the basis of these acquired immune responses may be critical in developing effective vaccines for genital herpes.

Recently, individuals have been identified who possess T cell responses to herpes simplex virus (HSV) antigens despite the absence of detectable anti-HSV antibodies in their serum. The significance of this immune seronegative status is unclear, but it could indicate resistance to overt HSV infection. The aims of the present study were to investigate whether genetic differences in receptors used by HSV for cell entry (herpesvirus entry mediator [HVEM], nectin-1, and nectin-2) could be detected in immune seronegative individuals. Coding polymorphisms were identified in the HVEM and nectin-1 genes. The variant receptor proteins were expressed, and their ability to bind the viral ligand glycoprotein D and to mediate HSV entry after transient transfection into normally resistant cells was compared with that of their wild-type counterparts. HSV entry activity in wild-type and variant forms of the receptors was indistinguishable, which indicates that the polymorphisms observed are unlikely to explain the possible restrictions on HSV replication or spread in immune seronegative individuals.

Herpes simplex virus (HSV) establishes a lifelong infection in humans. Reactivation of latent virus occurs intermittently so that the immune system is frequently exposed to viral Ag, providing an opportunity to evaluate memory T cells to a persistent human pathogen. We studied the persistence of genital herpes lesion-derived HSV-specific CD8+ CTL from three immunocompetent individuals with frequently recurring genital HSV-2 infection. All CTL clones were HSV-2 type specific and only one to three unique clonotypes were identified from any single biopsy specimen. The TCRBV genes utilized by these clonotypes were sequenced, and clonotype-specific probes were used to longitudinally track these clonotypes in PBMC and genital lesions. CTL clonotypes were consistently detected in PBMC and lesions for at least 2 and up to 7 years, and identical clonotypes infiltrated herpes lesions spaced as long as 7.5 years apart. Moreover, these clones were functionally lytic in vivo over these time periods. Additionally, CTL clones killed target cells infected with autologous viral isolates obtained 6.5 years after CTL clones were established, suggesting that selective pressure by these CTL did not result in the mutation of CTL epitopes. Thus, HSV recurs in the face of persistent CD8+ CTL with no evidence of clonal exhaustion or mutation of CTL epitopes as mechanisms of viral persistence.

The mechanisms involved in host clearance of symptomatic mucocutaneous herpes simplex virus (HSV) infection are unclear. We studied the functional properties of bulk cultures of skin-infiltrating lymphocytes from normal skin and serial biopsies of recurrent genital HSV-2 lesions, and compared HSV-specific and NK responses with viral clearance. HSV-specific CD4+ or CD8+ T cells were rarely detected in lymphocytes cultured from normal skin. The total lymphocyte count and HSV-specific and NK-like effector cell activities were markedly higher in cultures derived from lesional skin. HSV-specific CD4+ proliferative responses and NK-like cytotoxic responses were present at all stages of herpetic lesions, including biopsies early in the disease course. In contrast, cytotoxic T lymphocyte activity was generally low among cells derived from early culture-positive lesions, and increased during lesion evolution. Viral clearance from the lesion site was associated with a high level of local cytolytic activity towards HSV-infected cells. The phenotypes of cells with HSV-specific cytotoxic responses varied between patients, having CD4+ and CD8+ components. Immunotherapeutic approaches to HSV should be directed at improving in vivo cytolytic activity to HSV.

A 34-year-old healthy woman presented with a 15-month history of persistent, nonhealing vulvar ulcerations due to herpes simplex virus (HSV) type 2. Extensive dermatologic workup and serial skin biopsies failed to reveal an underlying vulvar dermatosis or autoimmune bullous disorder. Virologic studies revealed resistance to acyclovir in vitro due to deficiency in thymidine kinase activity. Serum antibody to human immunodeficiency virus was negative on two occasions, separated by 1 year. Immunologic evaluation showed normal HSV-specific proliferative and CD8 cytotoxic T lymphocyte responses as well as normal NK cell function. Vulvar lesions failed to heal in association with trials of topical trifluorothymidine and oral valacyclovir but resolved completely with the application of 1% foscarnet cream. No recurrence of HSV has been observed in 24 months of follow-up to date.

The specific mechanisms underlying the varied susceptibility of HIV-infected (HIV+) individuals to opportunistic infections (OI) are still incompletely understood. One hypothesis is that quantitative differences in specific T cell responses to a colonizing organism determine the development of an AIDS-defining OI. We evaluated this hypothesis for herpes simplex virus (HSV) infection, a common OI in HIV+ patients. Using limiting dilution analyses, the frequency of HSV-specific CD8+ cytotoxic T lymphocyte precursors (pCTL) and proliferative precursors were quantitated in peripheral blood mononuclear cells from 20 patients coinfected with HIV and HSV-2. The frequency of HSV-specific CD8+ pCTL in HSV+HIV+ individuals was significantly lower than in HSV+HIV- individuals (1 in 77,000 vs. 1 in 6,000, P = .0005) and was not different than in HSV-HIV- individuals (1 in 100,000, P = .24). HIV+ patients who suffered more severe genital herpes recurrences had significantly lower HSV-specific CD8+ pCTL frequencies than those patients with mild recurrences (1 in 170,000 vs. 1 in 26,000, P = .03). In contrast, no significant difference was seen in proliferative precursor frequencies between those patients with mild vs. severe genital herpes (1 in 3,800 vs. 1 in 6,600, P > .5). Quantitative differences in pCTL frequency to HSV appear to be the most important host factor influencing the frequency and severity of HSV reactivation in HIV+ patients. Studies to reconstitute such immunity, especially in people with acyclovir-resistant HSV, appear warranted.

Herpes simplex virus (HSV)-specific CD8+ cytotoxic T lymphocytes (CTL) have rarely been detected in humans, presumably because of virus-induced mechanisms that downregulate major histocompatibility complex class I expression. We have developed a method that has allowed us to consistently demonstrate HSV-specific CD8+ precursor CTL (pCTL) from HSV type 1- and 2-seropositive persons. Major histocompatibility complex-restricted HSV-specific CD8+ pCTL were found in 10 consecutively tested HSV type 1- and 2-seropositive subjects at frequencies ranging from 1 in 21,000 to 1 in 300 (median, 1 in 6,000) versus a pCTL frequency of 1 in 100,000 in HSV-seronegative donors. These results suggest that CD8+ CTL are important effector cells in resolving HSV lesions.

The effect of herpes simplex virus type 1 (HSV-1) infection on human cytotoxic T-lymphocyte (CTL) lytic function was assessed. All HSV-infected CTL populations tested were significantly inhibited in lysing target cells. The inhibition of CTL lytic function by infection with HSV-1 was independent of T-cell receptor-mediated antigen recognition and did not involve virus-induced shutoff of host protein synthesis, the expression of the HSV-1 transactivation protein, ICP4, or replicating virus. Understanding the functional impairment of CTL following infection with HSV may have important implications for HSV-induced immunosuppression and the mechanism of HSV persistence in immunocompetent hosts.

Previously, we demonstrated that human anti-HSV CTL and allo-antigen-specific CTL were inhibited in lysing their normally sensitive target cells when they were exposed to human fibroblasts (FB) infected with herpes simplex virus (HSV). In this study, the mechanism of inhibition of CTL lytic function by FB infected with HSV-1 (HSV-FB) was studied. CTL exposed to HSV-FB early (2 h) in the infection cycle were inhibited by a mechanism that appears to be distinct from the inhibition of lytic function mediated by HSV-FB at late times (20 h) during the infection cycle. The inhibition of CTL-mediated lysis by FB infected with HSV-1 for 2 h required the expression of ICP4, an immediate-early protein of HSV-1, but not the production of infectious virus or virus-induced shut-off of host protein synthesis. In contrast, the expression of HSV-specific glycoproteins essential for viral infectivity (glycoproteins B, D, H, K, and L), and thus, infectious virus, was required for inhibition of CTL lytic function by FB infected with HSV-1 for 20 h. Further, CTL exposed to FB infected with HSV-1 for 20 h expressed HSV-specific proteins indicating that they were infected with HSV-1. Cell-to-cell spread of HSV-1 appeared to be the major mode of transmission because 1) an insufficient level of HSV-1 was present in the supernatant of HSV-FB to inhibit CTL lytic function; and 2) paraformaldehyde-fixed HSV-FB did not inhibit CTL-mediated lysis. The inhibition of CTL lytic function by HSV-FB may be an important mechanism of HSV-induced immunosuppression, permitting the virus to spread and persist in immunocompetent hosts after primary infection or reactivation of latent HSV.

We examined the ability of human anti-herpes simplex virus (HSV) cytotoxic T lymphocytes (CTL) to lyse autologous human fibroblasts infected with HSV. In contrast to HSV-infected human Epstein-Barr virus-transformed B cells (LCL), which were lysed by HLA-restricted anti-HSV CTL, autologous fibroblasts infected with HSV were resistant to lysis. This resistance was not due to a lack of infectivity or production of HSV proteins since greater than 90% of the cells were infected and expressed abundant levels of viral proteins. HSV-infected human fibroblasts were also tested for susceptibility to lysis by alloantigen-specific CTL. Although allogeneic LCL and uninfected allogeneic fibroblasts were killed, human fibroblasts infected with HSV demonstrated a time-dependent resistance to lysis by alloantigen-specific CTL. HSV-infected human fibroblasts were not resistant to all forms of cell-mediated cytotoxicity since they were sensitive to antibody-dependent cellular cytotoxicity. Although one may suspect that the resistance of HSV-infected human fibroblasts to anti-HSV CTL and alloantigen-specific CTL-mediated lysis was due to a lack of major histocompatibility complex expression, Confer et al. (Proc. Natl. Acad. Sci. USA 87:3609-3613, 1990) previously demonstrated that incubation of human natural killer and lymphokine-activated killer cells with monolayers of human fibroblasts infected with HSV "disarmed" the killers in that they were unable to lyse sensitive target cells. We extend their results and show that incubation of anti-HSV CTL or alloantigen-specific CTL with uninfected fibroblasts did not affect their lytic activity, whereas CTL incubated with HSV-infected fibroblasts for 2 to 6 h rendered the CTL incapable of lysing their normally sensitive target cells. Indeed, human fibroblasts infected for merely 2 h with HSV were able to profoundly inhibit the cytotoxic activity of alloantigen-specific CTL. Thus, HSV-infected human fibroblasts are not inherently resistant to lysis by anti-HSV CTL or alloantigen-specific CTL, but rather contact of CTL with HSV-infected fibroblasts resulted in inactivation of the CTL. The inactivation of CTL appears to be HSV specific since incubation of alloantigen-specific CTL in sandwich assays with fibroblasts infected with HSV type 1 (HSV-1) or HSV-2 resulted in inactivation, whereas incubation of CTL with fibroblasts infected with adenovirus or vaccinia virus had no effect. Further, although incubation of alloantigen-specific CTL in sandwich assays with HSV-infected fibroblasts resulted in inhibition of CTL activity, exposure of CTL in Transwell cultures to cell-free supernatant from HSV-infected fibroblasts did not mediate this inhibitory effect.(ABSTRACT TRUNCATED AT 400 WORDS)