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Respiratory syncytial virus (RSV) belongs to the family Paramyxoviridae and is the single most important cause of serious lower respiratory tract infections in young children, yet no highly effective treatment or vaccine is available. Through a CX3C chemokine motif (182CWAIC186) in the G protein, RSV binds to the corresponding chemokine receptor, CX3CR1. Since RSV binding to CX3CR1 contributes to disease pathogenesis, we investigated whether a mutation in the CX3C motif by insertion of an alanine, A186, within the CX3C motif, mutating it to CX4C (182CWAIAC187), which is known to block binding to CX3CR1, might decrease disease. We studied the effect of the CX4C mutation in two strains of RSV (A2 and r19F) in a mouse challenge model. We included RSV r19F because it induces mucus production and airway resistance, two manifestations of RSV infection in humans, in mice. Compared to wild-type (wt) virus, mice infected with CX4C had a 0.7 to 1.2 log10-fold lower virus titer in the lung at 5 days postinfection (p.i.) and had markedly reduced weight loss, pulmonary inflammatory cell infiltration, mucus production, and airway resistance after challenge. This decrease in disease was not dependent on decrease in virus replication but did correspond to a decrease in pulmonary Th2 and inflammatory cytokines. Mice infected with CX4C viruses also had higher antibody titers and a Th1-biased T cell memory response at 75 days p.i. These results suggest that the CX4C mutation in the G protein could improve the safety and efficacy of a live attenuated RSV vaccine. [ABSTRACT FROM AUTHOR]

Background: Vaccines to prevent coronavirus disease 2019 (Covid-19) are urgently needed. The effect of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines on viral replication in both upper and lower airways is important to evaluate in nonhuman primates.Methods: Nonhuman primates received 10 or 100 μg of mRNA-1273, a vaccine encoding the prefusion-stabilized spike protein of SARS-CoV-2, or no vaccine. Antibody and T-cell responses were assessed before upper- and lower-airway challenge with SARS-CoV-2. Active viral replication and viral genomes in bronchoalveolar-lavage (BAL) fluid and nasal swab specimens were assessed by polymerase chain reaction, and histopathological analysis and viral quantification were performed on lung-tissue specimens.Results: The mRNA-1273 vaccine candidate induced antibody levels exceeding those in human convalescent-phase serum, with live-virus reciprocal 50% inhibitory dilution (ID50) geometric mean titers of 501 in the 10-μg dose group and 3481 in the 100-μg dose group. Vaccination induced type 1 helper T-cell (Th1)-biased CD4 T-cell responses and low or undetectable Th2 or CD8 T-cell responses. Viral replication was not detectable in BAL fluid by day 2 after challenge in seven of eight animals in both vaccinated groups. No viral replication was detectable in the nose of any of the eight animals in the 100-μg dose group by day 2 after challenge, and limited inflammation or detectable viral genome or antigen was noted in lungs of animals in either vaccine group.Conclusions: Vaccination of nonhuman primates with mRNA-1273 induced robust SARS-CoV-2 neutralizing activity, rapid protection in the upper and lower airways, and no pathologic changes in the lung. (Funded by the National Institutes of Health and others.). [ABSTRACT FROM AUTHOR]

Antibodies targeting epitopes through germline-encoded motifs can be found in different individuals. While these public antibodies are often beneficial, they also pose hurdles for subdominant antibodies to emerge. Here, we use transgenic mice that reproduce the human IGHV1-69 ∗ 01 germline-encoded antibody response to the conserved stem epitope on group 1 hemagglutinin (HA) of influenza A virus to show that this germline-endowed response can be overridden by a subdominant yet cross-group reactive public antibody response. Immunization with a non-cognate group 2 HA stem enriched B cells harboring the IGHD3-9 gene, thereby switching from IGHV1-69- to IGHD3-9-encoded motif-dependent epitope recognition. These IGHD3-9 antibodies bound, neutralized, and conferred cross-group protection in mice against influenza A viruses. A cryoelectron microscopy (cryo-EM) structure of an IGHD3-9 antibody resembled the human broadly neutralizing antibody FI6v3, which uses IGHD3-9. Together, our findings offer insights into vaccine regimens that engage an immunoglobulin repertoire with broader cross-reactivity to influenza A viruses., Competing Interests: Declaration of interests S.M.M., B.S.G., and M.K. are listed as inventors of patents and patent applications on vaccine immunogens used in this study filed by the NIH, US Department of Health and Human Services., (Published by Elsevier Inc.)

Immunogen design approaches aim to control the specificity and quality of antibody responses elicited by next-generation vaccines. Here, we use computational protein design to generate a nanoparticle vaccine platform based on the receptor-binding domain (RBD) of influenza hemagglutinin (HA) that enables precise control of antigen conformation and spacing. HA RBDs are presented as either monomers or native-like closed trimers that are connected to the underlying nanoparticle by a rigid linker that is modularly extended to precisely control antigen spacing. Nanoparticle immunogens with decreased spacing between trimeric RBDs elicit antibodies with improved hemagglutination inhibition and neutralization potency as well as binding breadth across diverse H1 HAs. Our "trihead" nanoparticle immunogen platform provides insights into anti-HA immunity, establishes antigen spacing as an important parameter in structure-based vaccine design, and embodies several design features that could be used in next-generation vaccines against influenza and other viruses., Competing Interests: Declaration of interests N.P.K. is a co-founder, shareholder, paid consultant, and chair of the scientific advisory board of Icosavax, Inc. The King lab has received unrelated sponsored research agreements from Pfizer and GSK. D.E. is a shareholder of Icosavax, Inc. A.D., D.E., M.K., and N.P.K. are listed as co-inventors on patent applications filed by the University of Washington related to this work., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

The receptor-binding domain (RBD) of influenza virus hemagglutinin (HA) elicits potently neutralizing yet mostly strain-specific antibodies. Here, we evaluate the ability of several immunofocusing techniques to enhance the functional breadth of vaccine-elicited immune responses against the HA RBD. We present a series of "trihead" nanoparticle immunogens that display native-like closed trimeric RBDs from the HAs of several H1N1 influenza viruses. The series includes hyperglycosylated and hypervariable variants that incorporate natural and designed sequence diversity at key positions in the receptor-binding site periphery. Nanoparticle immunogens displaying triheads or hyperglycosylated triheads elicit higher hemagglutination inhibition (HAI) and neutralizing activity than the corresponding immunogens lacking either trimer-stabilizing mutations or hyperglycosylation. By contrast, mosaic nanoparticle display and antigen hypervariation do not significantly alter the magnitude or breadth of vaccine-elicited antibodies. Our results yield important insights into antibody responses against the RBD and the ability of several structure-based immunofocusing techniques to influence vaccine-elicited antibody responses., Competing Interests: Declaration of interests N.P.K. is a co-founder, shareholder, paid consultant, and chair of the scientific advisory board of Icosavax, Inc. The King lab has received unrelated sponsored research agreements from Pfizer and GSK. D.E. is a shareholder of Icosavax, Inc. A.D., D.E., M.K., and N.P.K. are listed as co-inventors on patent applications filed by the University of Washington related to this work., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Multivalent antigen display is a fast-growing area of interest toward broadly protective vaccines. Current nanoparticle-based vaccine candidates demonstrate the ability to confer antibody-mediated immunity against divergent strains of notably mutable viruses. In coronaviruses, this work is predominantly aimed at targeting conserved epitopes of the receptor binding domain. However, targeting conserved non-RBD epitopes could limit the potential for antigenic escape. To explore new potential targets, we engineered protein nanoparticles displaying coronavirus prefusion-stabilized spike (CoV_S-2P) trimers derived from MERS-CoV, SARS-CoV-1, SARS-CoV-2, hCoV-HKU1, and hCoV-OC43 and assessed their immunogenicity in female mice. Monotypic SARS-1 nanoparticles elicit cross-neutralizing antibodies against MERS-CoV and protect against MERS-CoV challenge. MERS and SARS nanoparticles elicit S1-focused antibodies, revealing a conserved site on the S N-terminal domain. Moreover, mosaic nanoparticles co-displaying distinct CoV_S-2P trimers elicit antibody responses to distant cross-group antigens and protect male and female mice against MERS-CoV challenge. Our findings will inform further efforts toward the development of pan-coronavirus vaccines., (© 2023. Springer Nature Limited.)

Despite the availability of seasonal vaccines and antiviral medications, influenza virus continues to be a major health concern and pandemic threat due to the continually changing antigenic regions of the major surface glycoprotein, hemagglutinin (HA). One emerging strategy for the development of more efficacious seasonal and universal influenza vaccines is structure-guided design of nanoparticles that display conserved regions of HA, such as the stem. Using the H1 HA subtype to establish proof of concept, we found that tandem copies of an alpha-helical fragment from the conserved stem region (helix-A) can be displayed on the protruding spikes structures of a capsid scaffold. The stem region of HA on these designed chimeric nanoparticles is immunogenic and the nanoparticles are biochemically robust in that heat exposure did not destroy the particles and immunogenicity was retained. Furthermore, mice vaccinated with H1-nanoparticles were protected from lethal challenge with H1N1 influenza virus. By using a nanoparticle library approach with this helix-A nanoparticle design, we show that this vaccine nanoparticle construct design could be applicable to different influenza HA subtypes. Importantly, antibodies elicited by H1, H5, and H7 nanoparticles demonstrated homosubtypic and heterosubtypic cross-reactivity binding to different HA subtypes. Also, helix-A nanoparticle immunizations were used to isolate mouse monoclonal antibodies that demonstrated heterosubtypic cross-reactivity and provided protection to mice from viral challenge via passive-transfer. This tandem helix-A nanoparticle construct represents a novel design to display several hundred copies of non-trimeric conserved HA stem epitopes on vaccine nanoparticles. This design concept provides a new approach to universal influenza vaccine development strategies and opens opportunities for the development of nanoparticles with broad coverage over many antigenically diverse influenza HA subtypes., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

The head domain of influenza hemagglutinin (HA) elicits potently neutralizing yet mostly strain-specific antibodies during infection and vaccination. Here we evaluated a series of immunogens that combined several immunofocusing techniques for their ability to enhance the functional breadth of vaccine-elicited immune responses. We designed a series of "trihead" nanoparticle immunogens that display native-like closed trimeric heads from the HAs of several H1N1 influenza viruses, including hyperglycosylated variants and hypervariable variants that incorporate natural and designed sequence diversity at key positions in the periphery of the receptor binding site (RBS). Nanoparticle immunogens displaying triheads or hyperglycosylated triheads elicited higher HAI and neutralizing activity against vaccine-matched and -mismatched H1 viruses than corresponding immunogens lacking either trimer-stabilizing mutations or hyperglycosylation, indicating that both of these engineering strategies contributed to improved immunogenicity. By contrast, mosaic nanoparticle display and antigen hypervariation did not significantly alter the magnitude or breadth of vaccine-elicited antibodies. Serum competition assays and electron microscopy polyclonal epitope mapping revealed that the trihead immunogens, especially when hyperglycosylated, elicited a high proportion of antibodies targeting the RBS, as well as cross-reactive antibodies targeting a conserved epitope on the side of the head. Our results yield important insights into antibody responses against the HA head and the ability of several structure-based immunofocusing techniques to influence vaccine-elicited antibody responses., Competing Interests: Declaration of Interests N.P.K. is a cofounder, shareholder, paid consultant, and chair of the scientific advisory board of Icosavax, Inc. The King lab has received unrelated sponsored research agreements from Pfizer and GSK. D.E. is a shareholder of Icosavax, Inc. A.D., D.E., M.K., and N.P.K. are listed as co-inventors on patent applications filed by the University of Washington related to this work.

Current influenza vaccines predominantly induce immunity to the hypervariable hemagglutinin (HA) head, requiring frequent vaccine reformulation. Conversely, the immunosubdominant yet conserved HA stem harbors a supersite that is targeted by broadly neutralizing antibodies (bnAbs), representing a prime target for universal vaccines. Here, we showed that the co-immunization of two HA stem immunogens derived from group 1 and 2 influenza A viruses elicits cross-group protective immunity and neutralizing antibody responses in mice, ferrets, and nonhuman primates (NHPs). Immunized mice were protected from multiple group 1 and 2 viruses, and all animal models showed broad serum-neutralizing activity. A bnAb isolated from an immunized NHP broadly neutralized and protected against diverse viruses, including H5N1 and H7N9. Genetic and structural analyses revealed strong homology between macaque and human bnAbs, illustrating common biophysical constraints for acquiring cross-group specificity. Vaccine elicitation of stem-directed cross-group-protective immunity represents a step toward the development of broadly protective influenza vaccines., Competing Interests: Declaration of interests S.M.M., J.C.B., P.D.K., J.R.M., B.S.G., and M.K. are named inventors of US patents 9,441,019, 10,137,190, 10,363,301, and 11,338,033 on influenza HA nanoparticle vaccines and stabilized HA stem trimers and of several pending applications on related technologies filed by the US Department of Health and Human Services (NIH)., (Published by Elsevier Inc.)

Multivalent antigen display is a fast-growing area of interest towards broadly protective vaccines. Current nanoparticle-based vaccine candidates demonstrate the ability to confer antibody-mediated immunity against divergent strains of notably mutable viruses. In coronaviruses, this work is predominantly aimed at targeting conserved epitopes of the receptor-binding domain. However, targeting other conserved non-RBD epitopes could further limit the potential for antigenic escape. To further explore new potential targets, we engineered protein nanoparticles displaying CoV_S-2P trimers derived from MERS-CoV, SARS-CoV-1, SARS-CoV-2, hCoV-HKU1, and hCoV-OC43 and assessed their immunogenicity in mice. Monotypic SARS-1_S-2P nanoparticles elicited cross-neutralizing antibodies against MERS_S and protected against MERS-CoV challenge. MERS and SARS-I53_dn5 nanoparticles elicited S1-focused antibodies, revealing a conserved site on the NTD. Moreover, mosaic nanoparticles co-displaying distinct CoV_S-2P trimers elicited antibody responses to distant cross-group antigens while protecting against MERS challenge despite diminished valency of MERS_S-2P. Our findings will inform further efforts towards the development of pan-coronavirus vaccines., Competing Interests: Competing Interests The authors declare the existence of financial and non-financial competing interest.

Protein nanoparticle scaffolds are increasingly used in next-generation vaccine designs, and several have established records of clinical safety and efficacy. Yet the rules for how immune responses specific to nanoparticle scaffolds affect the immunogenicity of displayed antigens have not been established. Here we define relationships between anti-scaffold and antigen-specific antibody responses elicited by protein nanoparticle immunogens. We report that dampening anti-scaffold responses by physical masking does not enhance antigen-specific antibody responses. In a series of immunogens that all use the same nanoparticle scaffold but display four different antigens, only HIV-1 envelope glycoprotein (Env) is subdominant to the scaffold. However, we also demonstrate that scaffold-specific antibody responses can competitively inhibit antigen-specific responses when the scaffold is provided in excess. Overall, our results suggest that anti-scaffold antibody responses are unlikely to suppress antigen-specific antibody responses for protein nanoparticle immunogens in which the antigen is immunodominant over the scaffold., Competing Interests: Declaration of interests J.C.K. and N.P.K. are named as inventors on a patent application filed by the University of Washington based on the glycosylated protein nanoparticles presented in this paper. N.P.K. is a co-founder, shareholder, paid consultant, and chair of the scientific advisory board of Icosavax, Inc. The King lab has received unrelated sponsored research agreements from Pfizer and GSK. The Veesler lab has received an unrelated sponsored research agreement from Vir Biotechnology., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

As new vaccine technologies and platforms, such as nanoparticles and novel adjuvants, are developed to aid in the establishment of a universal influenza vaccine, studying traditional influenza split/subunit vaccines should not be overlooked. Commercially available vaccines are typically studied in terms of influenza A H1 and H3 viruses but influenza B viruses need to be examined as well. Thus, there is a need to both understand the limitations of split/subunit vaccines and develop strategies to overcome those limitations, particularly their ability to elicit cross-reactive antibodies to the co-circulating Victoria (B-V) and Yamagata (B-Y) lineages of human influenza B viruses. In this study, we compared three commercial influenza hemagglutinin (HA) split/subunit vaccines, one quadrivalent (H1, H3, B-V, B-Y HAs) and two trivalent (H1, H3, B-V HAs), to characterize potential differences in their antibody responses and protection against a B-Y challenge. We found that the trivalent adjuvanted vaccine Fluad, formulated without B-Y HA, was able to produce antibodies to B-Y (cross-lineage) on a similar level to those elicited from a quadrivalent vaccine (Flucelvax) containing both B-V and B-Y HAs. Interestingly, Fluad protected mice from a lethal cross-lineage B-Y viral challenge, while another trivalent vaccine, Fluzone HD, failed to elicit antibodies or full protection following challenge. Fluad immunization also diminished viral burden in the lungs compared to Fluzone and saline groups. The success of a trivalent vaccine to provide protection from a cross-lineage influenza B challenge, similar to a quadrivalent vaccine, suggests that further analysis of different split/subunit vaccine formulations could identify mechanisms for vaccines to target antigenically different viruses. Understanding how to increase the breadth of the immune response following immunization will be needed for universal influenza vaccine development., Competing Interests: The 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 Myers, Gallagher, Woolfork, Stradtmann-Carvalho, Maldonado-Puga, Bock, Boyoglu-Barnum, Syeda, Creanga, Alves, Kanekiyo and Harris.)

Human broadly neutralizing antibodies (bnAbs) targeting the hemagglutinin stalk of group 1 influenza A viruses (IAVs) are biased for IGHV1-69 alleles that use phenylalanine (F54) but not leucine (L54) within their CDRH2 loops. Despite this, we demonstrated that both alleles encode for human IAV bnAbs that employ structurally convergent modes of contact to the same epitope. To resolve differences in lineage expandability, we compared F54 versus L54 as substrate within humanized mice, where antibodies develop with human-like CDRH3 diversity but are restricted to single V H genes. While both alleles encoded for bnAb precursors, only F54 IGHV1-69 supported elicitation of heterosubtypic serum bnAbs following immunization with a stalk-only nanoparticle vaccine. L54 IGHV1-69 was unproductive, co-encoding for anergic B cells and autoreactive stalk antibodies that were cleared from B cell memory. Moreover, human stalk antibodies also demonstrated L54-dependent autoreactivity. Therefore, IGHV1-69 polymorphism, which is skewed ethnically, gates tolerance and vaccine expandability of influenza bnAbs., Competing Interests: Declaration of interests M.K. is listed as inventor of patents and patent applications on vaccine immunogens used in this study filed by the U.S. Department of Health and Human Services., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Knowledge about the impact of prior severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection of the elderly on mRNA vaccination response is needed to appropriately address the demand for additional vaccinations in this vulnerable population. Here, we show that octogenarians, a high-risk population, mount a sustained SARS-CoV-2 spike-specific immunoglobulin G (IgG) antibody response for 15 months following infection. This response boosts antibody levels 35-fold upon receiving a single dose of BNT162b2 mRNA vaccine 15 months after recovery from coronavirus disease 2019 (COVID-19). In contrast, antibody responses in naive individuals boost only 6-fold after a second vaccine. Spike-specific angiotensin-converting enzyme 2 (ACE2) antibody binding responses in the previously infected octogenarians following two vaccine doses exceed those found in a naive cohort after two doses. RNA sequencing (RNA-seq) demonstrates activation of interferon-induced genetic programs, which persist only in the previously infected. A preferential increase of specific immunoglobulin G heavy chain variable (IGHV) clonal transcripts that are the basis of neutralizing antibodies is observed only in the previously infected nuns., Competing Interests: Declaration of interests The authors declare no competing interests., (Published by Elsevier Inc.)

mRNA-1273 vaccine efficacy against SARS-CoV-2 Delta wanes over time; however, there are limited data on the impact of durability of immune responses on protection. Here, we immunized rhesus macaques and assessed immune responses over 1 year in blood and upper and lower airways. Serum neutralizing titers to Delta were 280 and 34 reciprocal ID 50 at weeks 6 (peak) and 48 (challenge), respectively. Antibody-binding titers also decreased in bronchoalveolar lavage (BAL). Four days after Delta challenge, the virus was unculturable in BAL, and subgenomic RNA declined by ∼3-log 10 compared with control animals. In nasal swabs, sgRNA was reduced by 1-log 10 , and the virus remained culturable. Anamnestic antibodies (590-fold increased titer) but not T cell responses were detected in BAL by day 4 post-challenge. mRNA-1273-mediated protection in the lungs is durable but delayed and potentially dependent on anamnestic antibody responses. Rapid and sustained protection in upper and lower airways may eventually require a boost., Competing Interests: Declaration of interests K.S.C. and B.S.G. are inventors on US patent no. 10,960,070 B2 and International patent application no. WO/2018/081318 entitled “Prefusion Coronavirus Spike Proteins and Their Use”. K.S.C. and B.S.G. are inventors on US patent application no. 62/972,886 entitled “2019-nCoV Vaccine”. L.W., E.S.Y., W.S., J.R.M., M.R., N.J.S. and D.C.D are inventors on US patent application no. 63/147,419 entitled “Antibodies Targeting the Spike Protein of Coronaviruses”. L.P., A. Cook, A.D., A.G., S.K., H.A., and M.G.L. are employees of Bioqual. K.S.C., L.W., W.S., and B.S.G are inventors on multiple US patent applications entitled “Anti-Coronavirus Antibodies and Methods of Use”. A. Carfi and D.K.E. are employees of Moderna. M.S.S. serves on the scientific board of advisors for Moderna. The other authors declare no competing interests., (Copyright © 2021. Published by Elsevier Inc.)

Neutralizing antibody responses gradually wane against several variants of concern (VOCs) after vaccination with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine messenger RNA-1273 (mRNA-1273). We evaluated the immune responses in nonhuman primates that received a primary vaccination series of mRNA-1273 and were boosted about 6 months later with either homologous mRNA-1273 or heterologous mRNA-1273.β, which encompasses the spike sequence of the B.1.351 Beta variant. After boost, animals had increased neutralizing antibody responses across all VOCs, which was sustained for at least 8 weeks after boost. Nine weeks after boost, animals were challenged with the SARS-CoV-2 Beta variant. Viral replication was low to undetectable in bronchoalveolar lavage and significantly reduced in nasal swabs in all boosted animals, suggesting that booster vaccinations may be required to sustain immunity and protection.

mRNA-1273 vaccine efficacy against SARS-CoV-2 Delta wanes over time; however, there are limited data on the impact of durability of immune responses on protection. We immunized rhesus macaques at weeks 0 and 4 and assessed immune responses over one year in blood, upper and lower airways. Serum neutralizing titers to Delta were 280 and 34 reciprocal ID 50 at weeks 6 (peak) and 48 (challenge), respectively. Antibody binding titers also decreased in bronchoalveolar lavage (BAL). Four days after challenge, virus was unculturable in BAL and subgenomic RNA declined ∼3-log 10 compared to control animals. In nasal swabs, sgRNA declined 1-log 10 and virus remained culturable. Anamnestic antibody responses (590-fold increase) but not T cell responses were detected in BAL by day 4 post-challenge. mRNA-1273-mediated protection in the lungs is durable but delayed and potentially dependent on anamnestic antibody responses. Rapid and sustained protection in upper and lower airways may eventually require a boost.

B.1.351 is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant most resistant to antibody neutralization. We demonstrate how the dose and number of immunizations influence protection. Nonhuman primates received two doses of 30 or 100 µg of Moderna's mRNA-1273 vaccine, a single immunization of 30 µg, or no vaccine. Two doses of 100 µg of mRNA-1273 induced 50% inhibitory reciprocal serum dilution neutralizing antibody titers against live SARS-CoV-2 p.Asp614Gly and B.1.351 of 3,300 and 240, respectively. Higher neutralizing responses against B.1.617.2 were also observed after two doses compared to a single dose. After challenge with B.1.351, there was ~4- to 5-log 10 reduction of viral subgenomic RNA and low to undetectable replication in bronchoalveolar lavages in the two-dose vaccine groups, with a 1-log 10 reduction in nasal swabs in the 100-µg group. These data establish that a two-dose regimen of mRNA-1273 will be critical for providing upper and lower airway protection against major variants of concern., (© 2021. This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.)

Immune correlates of protection can be used as surrogate endpoints for vaccine efficacy. Here, nonhuman primates (NHPs) received either no vaccine or doses ranging from 0.3 to 100 μg of the mRNA-1273 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. mRNA-1273 vaccination elicited circulating and mucosal antibody responses in a dose-dependent manner. Viral replication was significantly reduced in bronchoalveolar lavages and nasal swabs after SARS-CoV-2 challenge in vaccinated animals and most strongly correlated with levels of anti–S antibody and neutralizing activity. Lower antibody levels were needed for reduction of viral replication in the lower airway than in the upper airway. Passive transfer of mRNA-1273–induced immunoglobulin G to naïve hamsters was sufficient to mediate protection. Thus, mRNA-1273 vaccine–induced humoral immune responses are a mechanistic correlate of protection against SARS-CoV-2 in NHPs.

Adjuvanted soluble protein vaccines have been used extensively in humans for protection against various viral infections based on their robust induction of antibody responses. Here, soluble prefusion-stabilized spike protein trimers (preS dTM) from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were formulated with the adjuvant AS03 and administered twice to nonhuman primates (NHPs). Binding and functional neutralization assays and systems serology revealed that the vaccinated NHP developed AS03-dependent multifunctional humoral responses that targeted distinct domains of the spike protein and bound to a variety of Fc receptors mediating immune cell effector functions in vitro. The neutralizing 50% inhibitory concentration titers for pseudovirus and live SARS-CoV-2 were higher than titers for a panel of human convalescent serum samples. NHPs were challenged intranasally and intratracheally with a high dose (3 × 10 6 plaque forming units) of SARS-CoV-2 (USA-WA1/2020 isolate). Two days after challenge, vaccinated NHPs showed rapid control of viral replication in both the upper and lower airways. Vaccinated NHPs also had increased spike protein-specific immunoglobulin G (IgG) antibody responses in the lung as early as 2 days after challenge. Moreover, passive transfer of vaccine-induced IgG to hamsters mediated protection from subsequent SARS-CoV-2 challenge. These data show that antibodies induced by the AS03-adjuvanted preS dTM vaccine were sufficient to mediate protection against SARS-CoV-2 in NHPs and that rapid anamnestic antibody responses in the lung may be a key mechanism for protection., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).)

Neutralizing antibody responses gradually wane after vaccination with mRNA-1273 against several variants of concern (VOC), and additional boost vaccinations may be required to sustain immunity and protection. Here, we evaluated the immune responses in nonhuman primates that received 100 µg of mRNA-1273 vaccine at 0 and 4 weeks and were boosted at week 29 with mRNA-1273 (homologous) or mRNA-1273.β (heterologous), which encompasses the spike sequence of the B.1.351 (beta or β) variant. Reciprocal ID 50 pseudovirus neutralizing antibody geometric mean titers (GMT) against live SARS-CoV-2 D614G and the β variant, were 4700 and 765, respectively, at week 6, the peak of primary response, and 644 and 553, respectively, at a 5-month post-vaccination memory time point. Two weeks following homologous or heterologous boost β-specific reciprocal ID 50 GMT were 5000 and 3000, respectively. At week 38, animals were challenged in the upper and lower airway with the β variant. Two days post-challenge, viral replication was low to undetectable in both BAL and nasal swabs in most of the boosted animals. These data show that boosting with the homologous mRNA-1273 vaccine six months after primary immunization provides up to a 20-fold increase in neutralizing antibody responses across all VOC, which may be required to sustain high-level protection against severe disease, especially for at-risk populations., One-Sentence Summary: mRNA-1273 boosted nonhuman primates have increased immune responses and are protected against SARS-CoV-2 beta infection.

Vaccine-associated enhanced respiratory disease (VAERD) was previously observed in some preclinical models of severe acute respiratory syndrome (SARS) and MERS coronavirus vaccines. We used the SARS coronavirus 2 (SARS-CoV-2) mouse-adapted, passage 10, lethal challenge virus (MA10) mouse model of acute lung injury to evaluate the immune response and potential for immunopathology in animals vaccinated with research-grade mRNA-1273. Whole-inactivated virus or heat-denatured spike protein subunit vaccines with alum designed to elicit low-potency antibodies and Th2-skewed CD4 + T cells resulted in reduced viral titers and weight loss post challenge but more severe pathological changes in the lung compared to saline-immunized animals. In contrast, a protective dose of mRNA-1273 induced favorable humoral and cellular immune responses that protected from viral replication in the upper and lower respiratory tract upon challenge. A subprotective dose of mRNA-1273 reduced viral replication and limited histopathological manifestations compared to animals given saline. Overall, our findings demonstrate an immunological signature associated with antiviral protection without disease enhancement following vaccination with mRNA-1273., Competing Interests: Declaration of interests O.M.A., K.S.C., and B.S.G. are inventors on pending patent applications related to coronavirus vaccines. S.R.L. and R.S.B. have pending patents on recombinant viruses used in this study. A.T.D., D.K.E., and A.C. are current employees and shareholders of Moderna, Inc. Other authors declare no competing interests., (Published by Elsevier Inc.)

Background: Vaccine efficacy against the B.1.351 variant following mRNA-1273 vaccination in humans has not been determined. Nonhuman primates (NHP) are a useful model for demonstrating whether mRNA-1273 mediates protection against B.1.351., Methods: Nonhuman primates received 30 or 100 µg of mRNA-1273 as a prime-boost vaccine at 0 and 4 weeks, a single immunization of 30 µg at week 0, or no vaccine. Antibody and T cell responses were assessed in blood, bronchioalveolar lavages (BAL), and nasal washes. Viral replication in BAL and nasal swabs were determined by qRT-PCR for sgRNA, and histopathology and viral antigen quantification were performed on lung tissue post-challenge., Results: Eight weeks post-boost, 100 µg x2 of mRNA-1273 induced reciprocal ID 50 neutralizing geometric mean titers against live SARS-CoV-2 D614G and B.1.351 of 3300 and 240, respectively, and 430 and 84 for the 30 µg x2 group. There were no detectable neutralizing antibodies against B.1351 after the single immunization of 30 µg. On day 2 following B.1.351 challenge, sgRNA in BAL was undetectable in 6 of 8 NHP that received 100 µg x2 of mRNA-1273, and there was a ∼2-log reduction in sgRNA in NHP that received two doses of 30 µg compared to controls. In nasal swabs, there was a 1-log 10 reduction observed in the 100 µg x2 group. There was limited inflammation or viral antigen in lungs of vaccinated NHP post-challenge., Conclusions: Immunization with two doses of mRNA-1273 achieves effective immunity that rapidly controls lower and upper airway viral replication against the B.1.351 variant in NHP.

Immune correlates of protection can be used as surrogate endpoints for vaccine efficacy. The nonhuman primate (NHP) model of SARS-CoV-2 infection replicates key features of human infection and may be used to define immune correlates of protection following vaccination. Here, NHP received either no vaccine or doses ranging from 0.3 - 100 μg of mRNA-1273, a mRNA vaccine encoding the prefusion-stabilized SARS-CoV-2 spike (S-2P) protein encapsulated in a lipid nanoparticle. mRNA-1273 vaccination elicited robust circulating and mucosal antibody responses in a dose-dependent manner. Viral replication was significantly reduced in bronchoalveolar lavages and nasal swabs following SARS-CoV-2 challenge in vaccinated animals and was most strongly correlated with levels of anti-S antibody binding and neutralizing activity. Consistent with antibodies being a correlate of protection, passive transfer of vaccine-induced IgG to naïve hamsters was sufficient to mediate protection. Taken together, these data show that mRNA-1273 vaccine-induced humoral immune responses are a mechanistic correlate of protection against SARS-CoV-2 infection in NHP., One-Sentence Summary: mRNA-1273 vaccine-induced antibody responses are a mechanistic correlate of protection against SARS-CoV-2 infection in NHP.

Influenza vaccines that confer broad and durable protection against diverse viral strains would have a major effect on global health, as they would lessen the need for annual vaccine reformulation and immunization 1 . Here we show that computationally designed, two-component nanoparticle immunogens 2 induce potently neutralizing and broadly protective antibody responses against a wide variety of influenza viruses. The nanoparticle immunogens contain 20 haemagglutinin glycoprotein trimers in an ordered array, and their assembly in vitro enables the precisely controlled co-display of multiple distinct haemagglutinin proteins in defined ratios. Nanoparticle immunogens that co-display the four haemagglutinins of licensed quadrivalent influenza vaccines elicited antibody responses in several animal models against vaccine-matched strains that were equivalent to or better than commercial quadrivalent influenza vaccines, and simultaneously induced broadly protective antibody responses to heterologous viruses by targeting the subdominant yet conserved haemagglutinin stem. The combination of potent receptor-blocking and cross-reactive stem-directed antibodies induced by the nanoparticle immunogens makes them attractive candidates for a supraseasonal influenza vaccine candidate with the potential to replace conventional seasonal vaccines 3 .

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative infection of a global pandemic that has led to more than 2 million deaths worldwide. The Moderna mRNA-1273 vaccine has demonstrated ~94% efficacy in a Phase 3 study and has been approved under Emergency Use Authorization. The emergence of SARS-CoV-2 variants with mutations in the spike protein, most recently circulating isolates from the United Kingdom (B.1.1.7) and Republic of South Africa (B.1.351), has led to lower neutralization from convalescent serum by pseudovirus neutralization (PsVN) assays and resistance to certain monoclonal antibodies. Here, using two orthogonal VSV and lentivirus PsVN assays expressing spike variants of 20E (EU1), 20A.EU2, D614G-N439, mink cluster 5, B.1.1.7, and B.1.351 variants, we assessed the neutralizing capacity of sera from human subjects or non-human primates (NHPs) that received mRNA-1273. No significant impact on neutralization against the B.1.1.7 variant was detected in either case, however reduced neutralization was measured against the mutations present in B.1.351. Geometric mean titer (GMT) of human sera from clinical trial participants in VSV PsVN assay using D614G spike was 1/1852. VSV pseudoviruses with spike containing K417N-E484K-N501Y-D614G and full B.1.351 mutations resulted in 2.7 and 6.4-fold GMT reduction, respectively, when compared to the D614G VSV pseudovirus. Importantly, the VSV PsVN GMT of these human sera to the full B.1.351 spike variant was still 1/290, with all evaluated sera able to fully neutralize. Similarly, sera from NHPs immunized with 30 or 100μg of mRNA-1273 had VSV PsVN GMTs of ~ 1/323 or 1/404, respectively, against the full B.1.351 spike variant with a ~ 5 to 10-fold reduction compared to D614G. Individual mutations that are characteristic of the B.1.1.7 and B.1.351 variants had a similar impact on neutralization when tested in VSV or in lentivirus PsVN assays. Despite the observed decreases, the GMT of VSV PsVN titers in human vaccinee sera against the B.1.351 variant remained at ~1/300. Taken together these data demonstrate reduced but still significant neutralization against the full B.1.351 variant following mRNA-1273 vaccination.

A vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is needed to control the coronavirus disease 2019 (COVID-19) global pandemic. Structural studies have led to the development of mutations that stabilize Betacoronavirus spike proteins in the prefusion state, improving their expression and increasing immunogenicity 1 . This principle has been applied to design mRNA-1273, an mRNA vaccine that encodes a SARS-CoV-2 spike protein that is stabilized in the prefusion conformation. Here we show that mRNA-1273 induces potent neutralizing antibody responses to both wild-type (D614) and D614G mutant 2 SARS-CoV-2 as well as CD8 + T cell responses, and protects against SARS-CoV-2 infection in the lungs and noses of mice without evidence of immunopathology. mRNA-1273 is currently in a phase III trial to evaluate its efficacy.

Introduction: Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract disease in young children and a substantial contributor to respiratory tract disease throughout life. Despite RSV being a high priority for vaccine development, there is currently no safe and effective vaccine available. There are many challenges to developing an RSV vaccine and there are limited antiviral drugs or biologics available for the management of infection. In this article, we review the antiviral treatments, vaccination strategies along with alternative therapies for RSV., Areas Covered: This review is a summary of the current antiviral and RSV vaccination approaches noting strategies and alternative therapies that may prevent or decrease the disease severity in RSV susceptible populations., Expert Opinion: This review discusses anti-RSV strategies given that no safe and efficacious vaccines are available, and therapeutic treatments are limited. Various biologicals that target for RSV are considered for disease intervention, as it is likely that it may be necessary to develop separate vaccines or therapeutics for each at-risk population.

The conserved hemagglutinin (HA) stem has been a focus of universal influenza vaccine efforts. Influenza A group 1 HA stem-nanoparticles have been demonstrated to confer heterosubtypic protection in animals; however, the protection does not extend to group 2 viruses, due in part to differences in glycosylation between group 1 and 2 stems. Here, we show that introducing the group 2 glycan at Asn38 HA1 to a group 1 stem-nanoparticle (gN38 variant) based on A/New Caledonia/20/99 (H1N1) broadens antibody responses to cross-react with group 2 HAs. Immunoglobulins elicited by the gN38 variant provide complete protection against group 2 H7N9 virus infection, while the variant loses protection against a group 1 H5N1 virus. The N38 HA1 glycan thus is pivotal in directing antibody responses by controlling access to group-determining stem epitopes. Precise targeting of stem-directed antibody responses to the site of vulnerability by glycan repositioning may be a step towards achieving cross-group influenza protection.

Antibody paratopes are formed by hypervariable complementarity-determining regions (CDRH3s) and variable gene-encoded CDRs. The latter show biased usage in human broadly neutralizing antibodies (bnAbs) against both HIV and influenza virus, suggesting the existence of gene-endowed targeting solutions that may be amenable to pathway amplification. To test this, we generated transgenic mice with human CDRH3 diversity but simultaneously constrained to individual user-defined human immunoglobulin variable heavy-chain (V H ) genes, including IGHV1-69, which shows biased usage in human bnAbs targeting the hemagglutinin stalk of group 1 influenza A viruses. Sequential immunization with a stalk-only hemagglutinin nanoparticle elicited group 1 bnAbs, but only in IGHV1-69 mice. This V H -endowed response required minimal affinity maturation, was elicited alongside pre-existing influenza immunity, and when IGHV1-69 B cells were diluted to match the frequency measured in humans. These results indicate that the human repertoire could, in principle, support germline-encoded bnAb elicitation using a single recombinant hemagglutinin immunogen., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract disease in young children and a substantial contributor to respiratory tract disease throughout life and as such a high priority for vaccine development. However, after nearly 60 years of research no vaccine is yet available. The challenges to developing an RSV vaccine include the young age, 2-4 months of age, for the peak of disease, the enhanced RSV disease associated with the first RSV vaccine, formalin-inactivated RSV with an alum adjuvant (FI-RSV), and difficulty achieving protection as illustrated by repeat infections with disease that occur throughout life. Understanding the biology of infection and disease pathogenesis has and will continue to guide vaccine development. In this paper, we review the roles that RSV proteins play in the biology of infection and disease pathogenesis and the corresponding contribution to live attenuated and subunit RSV vaccines. Each of RSV's 11 proteins are in the design of one or more vaccines. The G protein's contribution to disease pathogenesis through altering host immune responses as well as its role in the biology of infection suggest it can make a unique contribution to an RSV vaccine, both live attenuated and subunit vaccines. One of G's potential unique contributions to a vaccine is the potential for anti-G immunity to have an anti-inflammatory effect independent of virus replication. Though an anti-viral effect is essential to an effective RSV vaccine, it is important to remember that the goal of a vaccine is to prevent disease. Thus, other effects of the infection, such as G's alteration of the host immune response may provide opportunities to induce responses that block this effect and improve an RSV vaccine. Keeping in mind the goal of a vaccine is to prevent disease and not virus replication may help identify new strategies for other vaccine challenges, such as improving influenza vaccines and developing HIV vaccines.

The present vaccine against influenza virus has the inevitable risk of antigenic discordance between the vaccine and the circulating strains, which diminishes vaccine efficacy. This necessitates new approaches that provide broader protection against influenza. Here we designed a vaccine using the hypervariable receptor-binding domain (RBD) of viral hemagglutinin displayed on a nanoparticle (np) able to elicit antibody responses that neutralize H1N1 influenza viruses spanning over 90 years. Co-display of RBDs from multiple strains across time, so that the adjacent RBDs are heterotypic, provides an avidity advantage to cross-reactive B cells. Immunization with the mosaic RBD-np elicited broader antibody responses than those induced by an admixture of nanoparticles encompassing the same set of RBDs as separate homotypic arrays. Furthermore, we identified a broadly neutralizing monoclonal antibody in a mouse immunized with mosaic RBD-np. The mosaic antigen array signifies a unique approach that subverts monotypic immunodominance and allows otherwise subdominant cross-reactive B cell responses to emerge.

Influenza vaccines targeting the highly conserved stem of the hemagglutinin (HA) surface glycoprotein have the potential to protect against pandemic and drifted seasonal influenza viruses not covered by current vaccines. While HA stem-based immunogens derived from group 1 influenza A viruses have been shown to induce intragroup heterosubtypic protection, HA stem-specific antibody lineages originating from group 2 may be more likely to possess broad cross-group reactivity. We report the structure-guided development of mammalian-cell-expressed candidate vaccine immunogens based on influenza A virus group 2 H3 and H7 HA stem trimers displayed on self-assembling ferritin nanoparticles using an iterative, multipronged approach involving helix stabilization, loop optimization, disulfide bond addition, and side-chain repacking. These immunogens were thermostable, formed uniform and symmetric nanoparticles, were recognized by cross-group-reactive broadly neutralizing antibodies (bNAbs) with nanomolar affinity, and elicited protective, homosubtypic antibodies in mice. Importantly, several immunogens were able to activate B cells expressing inferred unmutated common ancestor (UCA) versions of cross-group-reactive human bNAbs from two multidonor classes, suggesting they could initiate elicitation of these bNAbs in humans. IMPORTANCE Current influenza vaccines are primarily strain specific, requiring annual updates, and offer minimal protection against drifted seasonal or pandemic strains. The highly conserved stem region of hemagglutinin (HA) of group 2 influenza A virus subtypes is a promising target for vaccine elicitation of broad cross-group protection against divergent strains. We used structure-guided protein engineering employing multiple protein stabilization methods simultaneously to develop group 2 HA stem-based candidate influenza A virus immunogens displayed as trimers on self-assembling nanoparticles. Characterization of antigenicity, thermostability, and particle formation confirmed structural integrity. Group 2 HA stem antigen designs were identified that, when displayed on ferritin nanoparticles, activated B cells expressing inferred unmutated common ancestor (UCA) versions of human antibody lineages associated with cross-group-reactive, broadly neutralizing antibodies (bNAbs). Immunization of mice led to protection against a lethal homosubtypic influenza virus challenge. These candidate vaccines are now being manufactured for clinical evaluation.

RSV is a major cause of severe lower respiratory infection in infants and young children. With no vaccine yet available, it is important to clarify mechanisms of disease pathogenesis. Since indoleamine-2,3-dioxygenase (IDO) is an immunomodulatory enzyme and is upregulated with RSV infection, we studied it in vivo during infection of BALB/c mice and in vitro in A549 cells. RSV infection upregulated IDO transcripts in vivo and in vitro. IDO siRNA decreased IDO transcripts ~2 fold compared to control siRNA after RSV infection but this decrease did not affect RSV replication. In the presence of IFN-γ, siRNA-induced a decrease in IDO expression that was associated with an increase in virus replication and increased levels of IL-6, IL-8, CXCL10 and CCL4. Thus, our results show IDO is upregulated with RSV infection and this upregulation likely participates with IFN-γ in inhibition of virus replication and suppression of some host cell responses to infection., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Respiratory syncytial virus (RSV) belongs to the family Paramyxoviridae and is the single most important cause of serious lower respiratory tract infections in young children, yet no highly effective treatment or vaccine is available. To clarify the potential for an anti-G mAb, 131-2G which has both anti-viral and anti-inflammatory effects, to effectively treat RSV disease, we determined the kinetics of its effect compared to the effect of the anti-F mAb, 143-6C on disease in mice. Treatment administered three days after RSV rA2-line19F (r19F) infection showed 131-2G decreased breathing effort, pulmonary mucin levels, weight loss, and pulmonary inflammation earlier and more effectively than treatment with mAb 143-6C. Both mAbs stopped lung virus replication at day 5 post-infection. These data show that, in mice, anti-G protein mAb is superior to treating disease during RSV infection than an anti-F protein mAb similar to Palivizumab. This combination of anti-viral and anti-inflammatory activity makes 131-2G a promising candidate for treating for active human RSV infection., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Respiratory syncytial virus (RSV) is a major cause of severe pneumonia and bronchiolitis in infants and young children, and causes disease throughout life. Understanding the biology of infection, including virus binding to the cell surface, should help develop antiviral drugs or vaccines. The RSV F and G glycoproteins bind cell surface heparin sulfate proteoglycans (HSPGs) through heparin-binding domains. The G protein also has a CX3C chemokine motif which binds to the fractalkine receptor CX3CR1. G protein binding to CX3CR1 is not important for infection of immortalized cell lines, but reportedly is so for primary human airway epithelial cells (HAECs), the primary site for human infection. We studied the role of CX3CR1 in RSV infection with CX3CR1-transfected cell lines and HAECs with variable percentages of CX3CR1-expressing cells, and the effect of anti-CX3CR1 antibodies or a mutation in the RSV CX3C motif. Immortalized cells lacking HSPGs had low RSV binding and infection, which was increased markedly by CX3CR1 transfection. CX3CR1 was expressed primarily on ciliated cells, and ∼50 % of RSV-infected cells in HAECs were CX3CR1+. HAECs with more CX3CR1-expressing cells had a proportional increase in RSV infection. Blocking G binding to CX3CR1 with anti-CX3CR1 antibody or a mutation in the CX3C motif significantly decreased RSV infection in HAECs. The kinetics of cytokine production suggested that the RSV/CX3CR1 interaction induced RANTES (regulated on activation normal T-cell expressed and secreted protein), IL-8 and fractalkine production, whilst it downregulated IL-15, IL1-RA and monocyte chemotactic protein-1. Thus, the RSV G protein/CX3CR1 interaction is likely important in infection and infection-induced responses of the airway epithelium, the primary site of human infection.

Unlabelled: Respiratory syncytial virus (RSV) is the single most important cause of serious lower respiratory tract infections in young children, yet no highly effective treatment or vaccine is available. In the present study, we investigated the effect of prophylactic treatment with the intact and F(ab')2 forms of an anti-G protein monoclonal antibody (MAb), 131-2G, on the humoral and cellular adaptive immune responses to RSV rA2-line19F (r19F) challenge in BALB/c mice. The F(ab')2 form of 131-2G does not decrease virus replication, but intact 131-2G does. The serum specimens for antibodies and spleen cells for memory T cell responses to RSV antigens were analyzed at 30, 45, 75, and 95 days postinfection (p.i.) with or without prior treatment with 131-2G. The ratios of Th2 to Th1 antibody isotypes at each time p.i indicated that both forms of MAb 131-2G shifted the subclass response from a Th2 (IgG1 and IgG2b) to a Th1 (IgG2A) bias. The ratio of IgG1 to IgG2A antibody titer was 3-fold to 10-fold higher for untreated than MAb-treated mice. There was also some increase in IgG (22% ± 13% increase) and neutralization (32% increase) in antibodies with MAb 131-2G prophylaxis at 75 days p.i. Treatment with 131-2G significantly (P ≤ 0.001) decreased the percentage of interleukin-4 (IL-4)-positive CD4 and CD8 cells in RSV-stimulated spleen cells at all times p.i., while the percentage of interferon gamma (IFN-γ) T cells significantly (P ≤ 0.001) increased ≥ 75 days p.i. The shift from a Th2- to a Th1-biased T cell response in treated compared to untreated mice likely was directed by the much higher levels of T-box transcription factor (T-bet) (≥ 45% versus <10%) in CD4 and CD8 T cells and lower levels of Gata-3 (≤ 2% versus ≥ 6%) in CD4 T cells in peptide-stimulated, day 75 p.i. spleen cells. These data show that the RSV G protein affects both humoral and cellular adaptive immune responses, and induction of 131-2G-like antibodies might improve the safety and long-term efficacy of an RSV vaccine., Importance: The data in this report suggest that the RSV G protein not only contributes to disease but also dampens the host immune response to infection. Both effects of G likely contribute to difficulties in achieving an effective vaccine. The ability of MAb 131-2G to block these effects of G suggests that inducing antibodies similar to 131-2G should prevent disease and enhance the adaptive immune response with later RSV infection. The fact that 131-2G binds to the 13-amino-acid region conserved among all strains and that flanking sequences are conserved within group A or group B strains simplifies the task of developing a vaccine to induce 131-2G-like antibodies. If our findings in mice apply to humans, then including the 131-2G binding region of G in a vaccine should improve its safety and efficacy., (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)

Respiratory syncytial virus (RSV) is a major cause of severe lower respiratory infection in infants and young children and causes disease in the elderly and persons with compromised cardiac, pulmonary, or immune systems. Despite the high morbidity rates of RSV infection, no highly effective treatment or vaccine is yet available. The RSV G protein is an important contributor to the disease process. A conserved CX3C chemokine-like motif in G likely contributes to the pathogenesis of disease. Through this motif, G protein binds to CX3CR1 present on various immune cells and affects immune responses to RSV, as has been shown in the mouse model of RSV infection. However, very little is known of the role of RSV CX3C-CX3CR1 interactions in human disease. In this study, we use an in vitro model of human RSV infection comprised of human peripheral blood mononuclear cells (PBMCs) separated by a permeable membrane from human airway epithelial cells (A549) infected with RSV with either an intact CX3C motif (CX3C) or a mutated motif (CX4C). We show that the CX4C virus induces higher levels of type I/III interferon (IFN) in A549 cells, increased IFN-α and tumor necrosis factor alpha (TNF-α) production by human plasmacytoid dendritic cells (pDCs) and monocytes, and increased IFN-γ production in effector/memory T cell subpopulations. Treatment of CX3C virus-infected cells with the F(ab')2 form of an anti-G monoclonal antibody (MAb) that blocks binding to CX3CR1 gave results similar to those with the CX4C virus. Our data suggest that the RSV G protein CX3C motif impairs innate and adaptive human immune responses and may be important to vaccine and antiviral drug development.

Respiratory syncytial virus (RSV) belongs to the family Paramyxoviridae and is the single most important cause of serious lower respiratory tract infections in young children, yet no highly effective treatment or vaccine is available. Increased airway resistance and increased airway mucin production are two manifestations of RSV infection in children. RSV rA2-line19F infection induces pulmonary mucous production and increased breathing effort in BALB/c mice and provides a way to assess these manifestations of RSV disease in an animal model. In the present study, we investigated the effect of prophylactic treatment with the F(ab')2 form of the anti-G protein monoclonal antibody (MAb) 131-2G on disease in RSV rA2-line19F-challenged mice. F(ab')2 131-2G does not affect virus replication. It and the intact form that does decrease virus replication prevented increased breathing effort and airway mucin production, as well as weight loss, pulmonary inflammatory-cell infiltration, and the pulmonary substance P and pulmonary Th2 cytokine levels that occur in mice challenged with this virus. These data suggest that the RSV G protein contributes to prominent manifestations of RSV disease and that MAb 131-2G can prevent these manifestations of RSV disease without inhibiting virus infection.