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Background: Inactivated trivalent poliovirus vaccine (IPV) induces humoral immunity, which protects against paralytic poliomyelitis but does not induce sufficient mucosal immunity to block intestinal infection. We assessed the intestinal immunity in healthy adults in Belgium conferred by a co-formulation of IPV with the mucosal adjuvant double mutant Labile Toxin (dmLT) derived from Escherichia coli.Methods: Healthy fully IPV-vaccinated 18-45-year-olds were randomly allocated to three groups: on Day 1 two groups received one full dose of IPV (n = 30) or IPV + dmLT (n = 30) in a blinded manner, and the third received an open-label dose of bivalent live oral polio vaccine (bOPV types 1 and 3, n = 20). All groups received a challenge dose of bOPV on Day 29. Participants reported solicited and unsolicited adverse events (AE) using study diaries. Mucosal immune responses were measured by fecal neutralization and IgA on Days 29 and 43, with fecal shedding of challenge viruses measured for 28 days. Humoral responses were measured by serum neutralizing antibody (NAb).Results: Solicited and unsolicited AEs were mainly mild-to-moderate and transient in all groups, with no meaningful differences in rates between groups. Fecal shedding of challenge viruses in both IPV groups exceeded that of the bOPV group but was not different between IPV and IPV + dmLT groups. High serum NAb responses were observed in both IPV groups, alongside modest levels of fecal neutralization and IgA. Conclusions: Addition of dmLT to IPV administered intramuscularly neither affected humoral nor intestinal immunity nor decreased fecal virus shedding following bOPV challenge. The tolerability of the dose of dmLT used in this study may allow higher doses to be investigated for impact on mucosal immunity.Registered on ClinicalTrials.gov - NCT04232943.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

SARS-CoV-2 variants have continuously emerged even as highly effective vaccines have been widely deployed. Reduced neutralization observed against variants of concern (VOC) raises the question as to whether other antiviral antibody activities are similarly compromised, or if they might compensate for lost neutralization activity. In this study, the breadth and potency of antibody recognition and effector function was surveyed in both healthy individuals as well as immunologically vulnerable subjects following either natural infection or receipt of an mRNA vaccine. Considering pregnant women as a model cohort with higher risk of severe illness and death, we observed similar binding and functional breadth for healthy and immunologically vulnerable populations. In contrast, considerably greater functional antibody breadth and potency across VOC was associated with vaccination than prior infection. However, greater antibody functional activity targeting the endemic coronavirus OC43 was noted among convalescent individuals, illustrating a dichotomy in recognition between close and distant human coronavirus strains that was associated with exposure history. Probing the full-length spike and receptor binding domain (RBD) revealed that antibody-mediated Fc effector functions were better maintained against full-length spike as compared to RBD. This analysis of antibody functions in healthy and vulnerable populations across a panel of SARS-CoV-2 VOC and extending through endemic alphacoronavirus strains suggests the differential potential for antibody effector functions to contribute to protecting vaccinated and convalescent subjects as the pandemic progresses and novel variants continue to evolve.One Sentence SummaryAs compared to natural infection with SARS-CoV-2, vaccination drives superior functional antibody breadth raising hopes for candidate universal CoV vaccines.

Significance In this report we identify genetic susceptibility variants for periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome, the most common periodic fever syndrome in children. PFAPA shares risk loci at IL12A, STAT4, IL10, and CCR1-CCR3 with Behçet’s disease and recurrent aphthous stomatitis, defining a family of Behçet’s spectrum disorders. Differential HLA associations along this spectrum may determine where individual phenotypes fall among the Behçet’s spectrum disorders., Periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome is the most common periodic fever syndrome in children. The disease appears to cluster in families, but the pathogenesis is unknown. We queried two European–American cohorts and one Turkish cohort (total n = 231) of individuals with PFAPA for common variants previously associated with two other oropharyngeal ulcerative disorders, Behçet’s disease and recurrent aphthous stomatitis. In a metaanalysis, we found that a variant upstream of IL12A (rs17753641) is strongly associated with PFAPA (OR 2.13, P = 6 × 10−9). We demonstrated that monocytes from individuals who are heterozygous or homozygous for this risk allele produce significantly higher levels of IL-12p70 upon IFN-γ and LPS stimulation than those from individuals without the risk allele. We also found that variants near STAT4, IL10, and CCR1-CCR3 were significant susceptibility loci for PFAPA, suggesting that the pathogenesis of PFAPA involves abnormal antigen-presenting cell function and T cell activity and polarization, thereby implicating both innate and adaptive immune responses at the oropharyngeal mucosa. Our results illustrate genetic similarities among recurrent aphthous stomatitis, PFAPA, and Behçet’s disease, placing these disorders on a common spectrum, with recurrent aphthous stomatitis on the mild end, Behçet’s disease on the severe end, and PFAPA intermediate. We propose naming these disorders Behçet’s spectrum disorders to highlight their relationship. HLA alleles may be factors that influence phenotypes along this spectrum as we found new class I and II HLA associations for PFAPA distinct from Behçet’s disease and recurrent aphthous stomatitis.

Background While antibodies can provide significant protection from SARS-CoV-2 infection and disease sequelae, the specific attributes of the humoral response that contribute to immunity are incompletely defined. Methods We employ machine learning to relate characteristics of the polyclonal antibody response raised by natural infection to diverse antibody effector functions and neutralization potency with the goal of generating both accurate predictions of each activity based on antibody response profiles as well as insights into antibody mechanisms of action. Results To this end, antibody-mediated phagocytosis, cytotoxicity, complement deposition, and neutralization were accurately predicted from biophysical antibody profiles in both discovery and validation cohorts. These models identified SARS-CoV-2-specific IgM as a key predictor of neutralization activity whose mechanistic relevance was supported experimentally by depletion. Conclusions Validated models of how different aspects of the humoral response relate to antiviral antibody activities suggest desirable attributes to recapitulate by vaccination or other antibody-based interventions.

Eradication of poliomyelitis globally is constrained by fecal shedding of live polioviruses, both wild-type and vaccine-derived strains, into the environment. Although inactivated polio vaccines (IPV) effectively protect the recipient from clinical poliomyelitis, fecal shedding of live virus still occurs following infection with either wildtype or vaccine-derived strains of poliovirus. In the drive to eliminate the last cases of polio globally, improvements in both oral polio vaccines (OPV) (to prevent reversion to virulence) and injectable polio vaccines (to improve mucosal immunity and prevent viral shedding) are underway. The E. coli labile toxin with two or "double" attenuating mutations (dmLT) may boost immunologic responses to IPV, including at mucosal sites. We performed a double-blinded phase I controlled clinical trial to evaluate safety, tolerability, as well as systemic and mucosal immunogenicity of IPV adjuvanted with dmLT, given as a fractional (1/5th) dose intradermally (fIPV-dmLT). Twenty-nine volunteers with no past exposure to OPV were randomized to a single dose of fIPV-dmLT or fIPV alone. fIPV-dmLT was well tolerated, although three subjects had mild but persistent induration and hyperpigmentation at the injection site. A ≥ 4-fold rise in serotype-specific neutralizing antibody (SNA) titers to all three serotypes was seen in 84% of subjects receiving fIPV-dmLT vs. 50% of volunteers receiving IPV alone. SNA titers were higher in the dmLT-adjuvanted group, but only differences in serotype 1 were significant. Mucosal immune responses, as measured by polio serotype specific fecal IgA were minimal in both groups and differences were not seen. fIPV-dmLT may offer a benefit over IPV alone. Beyond NAB responses protecting the individual, studies demonstrating the ability of fIPV-dmLT to prevent viral shedding are necessary. Studies employing controlled human infection models, using monovalent OPV post-vaccine are ongoing. Studies specifically in children may also be necessary and additional biomarkers of mucosal immune responses in this population are needed. Clinicaltrials.gov Identifer: NCT03922061.

Background A longitudinal study was performed to determine the breadth, kinetics, and correlations of systemic and mucosal antibody responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Methods Twenty-six unvaccinated adults with confirmed coronavirus disease 2019 (COVID-19) were followed for 6 months with 3 collections of blood, nasal secretions, and stool. Control samples were obtained from 16 unvaccinated uninfected individuals. SARS-CoV-2 neutralizing and binding antibody responses were respectively evaluated by pseudovirus assays and multiplex bead arrays. Results Neutralizing antibody responses to SARS-CoV-2 were detected in serum and respiratory samples for 96% (25/26) and 54% (14/26), respectively, of infected participants. Robust binding antibody responses against SARS-CoV-2 spike protein and S1, S2, and receptor binding (RBD) domains occurred in serum and respiratory nasal secretions, but not in stool samples. Serum neutralization correlated with RBD-specific immunoglobulin (Ig)G, IgM, and IgA in serum (Spearman ρ = 0.74, 0.66, and 0.57, respectively), RBD-specific IgG in respiratory secretions (ρ = 0.52), disease severity (ρ = 0.59), and age (ρ = 0.40). Respiratory mucosal neutralization correlated with RBD-specific IgM (ρ = 0.42) and IgA (ρ = 0.63). Conclusions Sustained antibody responses occurred after SARS-CoV-2 infection. Notably, there was independent induction of IgM and IgA binding antibody and neutralizing responses in systemic and respiratory compartments. These observations have implications for current vaccine strategies and understanding SARS-CoV-2 reinfection and transmission.

Pre-existing antibodies to endemic coronaviruses (CoV) that cross-react with SARS-CoV-2 have the potential to influence the antibody response to COVID-19 vaccination and infection for better or worse. In this observational study of mucosal and systemic humoral immunity in acutely infected, convalescent, and vaccinated subjects, we tested for cross reactivity against endemic CoV spike (S) protein at subdomain resolution. Elevated responses, particularly to the β-CoV OC43, were observed in all natural infection cohorts tested and were correlated with the response to SARS-CoV-2. The kinetics of this response and isotypes involved suggest that infection boosts preexisting antibody lineages raised against prior endemic CoV exposure that cross react. While further research is needed to discern whether this recalled response is desirable or detrimental, the boosted antibodies principally targeted the better conserved S2 subdomain of the viral spike and were not associated with neutralization activity. In contrast, vaccination with a stabilized spike mRNA vaccine did not robustly boost cross-reactive antibodies, suggesting differing antigenicity and immunogenicity. In sum, this study provides evidence that antibodies targeting endemic CoV are robustly boosted in response to SARS-CoV-2 infection but not to vaccination with stabilized S, and that depending on conformation or other factors, the S2 subdomain of the spike protein triggers a rapidly recalled, IgG-dominated response that lacks neutralization activity., Graphical Abstract Antibody responses to SARS-CoV-2 and endemic CoV spike proteins were measured in diverse cohorts. While antibodies to SARS-CoV-2 were induced across all isotypes, only IgA and IgG responses to endemic CoV were robustly boosted, and only among naturally-infected but not vaccinated individuals. These recalled, cross-reactive responses to endemic CoV primarily recognized the better conserved S2 domain and were non-neutralizing. While other antiviral activities of broadly cross-reactive S2-specifc antibodies are not known, the differing antigenicity of natural infection and vaccination with stabilized pre-fusion spike has potential implications for the breadth and level of protection afforded by each.

A cornerstone of the global initiative to eradicate polio is the widespread use of live and inactivated poliovirus vaccines in extensive public health campaigns designed to prevent the development of paralytic disease and interrupt transmission of the virus. Central to these efforts is the goal of inducing mucosal immunity able to limit virus replication in the intestine. Recent clinical trials have evaluated new combined regimens of poliovirus vaccines, and demonstrated clear differences in their ability to restrict virus shedding in stool after oral challenge with live virus. Analyses of mucosal immunity accompanying these trials support a critical role for enteric neutralizing IgA in limiting the magnitude and duration of virus shedding. This review summarizes key findings in vaccine-induced intestinal immunity to poliovirus in infants, older children, and adults. The impact of immunization on development and maintenance of protective immunity to poliovirus and the implications for global eradication are discussed.

Convalescent plasma has been deployed globally as a treatment for COVID-19, but efficacy has been mixed. Better understanding of the antibody characteristics that may contribute to its antiviral effects is important for this intervention as well as offer insights into correlates of vaccine-mediated protection., Convalescent plasma is a promising therapy for coronavirus disease 2019 (COVID-19), but the antibody characteristics that contribute to efficacy remain poorly understood. This study analyzed plasma samples from 126 eligible convalescent blood donors in addition to 15 naive individuals, as well as an additional 20 convalescent individuals as a validation cohort. Multiplexed Fc Array binding assays and functional antibody response assays were utilized to evaluate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody composition and activity. Donor convalescent plasma samples contained a range of antibody cell- and complement-mediated effector functions, indicating the diverse antiviral activity of humoral responses observed among recovered individuals. In addition to viral neutralization, convalescent plasma samples contained antibodies capable of mediating such Fc-dependent functions as complement activation, phagocytosis, and antibody-dependent cellular cytotoxicity against SARS-CoV-2. Plasma samples from a fraction of eligible donors exhibited high activity across all activities evaluated. These polyfunctional plasma samples could be identified with high accuracy with even single Fc Array features, whose correlation with polyfunctional activity was confirmed in the validation cohort. Collectively, these results expand understanding of the diversity of antibody-mediated antiviral functions associated with convalescent plasma, and the polyfunctional antiviral functions suggest that it could retain activity even when its neutralizing capacity is reduced by mutations in variant SARS-CoV-2.

Although a growing number of studies suggest interactions between Schistosoma parasites and viral infections, the effects of schistosome infections on the host response to viruses have not been evaluated comprehensively. In this systematic review, we investigated how schistosomes impact incidence, virulence, and prevention of viral infections in humans and animals. We also evaluated immune effects of schistosomes in those coinfected with viruses. We screened 4,730 studies and included 103. Schistosomes may increase susceptibility to some viruses, including HIV and Kaposi’s sarcoma-associated herpesvirus, and virulence of hepatitis B and C viruses. In contrast, schistosome infection may be protective in chronic HIV, Human T-cell Lymphotropic Virus-Type 1, and respiratory viruses, though further research is needed. Schistosome infections were consistently reported to impair immune responses to hepatitis B and possibly measles vaccines. Understanding the interplay between schistosomes and viruses has ramifications for anti-viral vaccination strategies and global control of viral infections., Author summary Many studies have described the effects of parasitic Schistosoma worm infections on the way that humans and animals respond to a variety of viral infections. Our goal was to evaluate, in a systematic manner, how having a schistosome parasitic infection affects a host’s susceptibility to viral infections, the clinical disease course of viral infections, and prevention of viral infections by vaccines. We also assessed the effects of schistosome infection on the host immune response to viruses. We screened 4,730 studies for potential relevance and included 103 of them in this review. Overall, our analysis showed that schistosome infection impairs the host response to many viruses. This includes increasing host susceptibility to HIV and possibly Kaposi’s sarcoma-associated herpesvirus, worsening the severity of clinical disease in hepatitis B and C infections, and decreasing immune responses to vaccines for hepatitis B and possibly measles. The studies that we analyzed also suggested that schistosome infection may protect the host against poor clinical outcomes from some viral infections including Human T-cell Lymphotropic Virus-Type 1, respiratory viruses, and chronic HIV. We discuss how these findings might be interpreted, and the additional research needed, in order to improve anti-viral vaccination strategies and control of viral infections globally.

In a blinded phase 1 trial (EudraCT 2017-0000908-21; NCT03430349) in Belgium, healthy adults (aged 18-50 years) previously immunized exclusively with inactivated poliovirus vaccine were administered a single dose of 1 of 2 novel type 2 oral poliovirus vaccines (nOPV2-c1: S2/cre5/S15domV/rec1/hifi3 (n = 15); nOPV2-c2: S2/S15domV/CpG40 (n = 15)) and isolated for 28 days in a purpose-built containment facility. Using stool samples collected near days 0, 14, 21, and 28, we evaluated intestinal neutralization and immunoglobulin A responses to the nOPV2s and found that nOPV2-c1 and nOPV2-c2 induced detectable poliovirus type 2-specific intestinal neutralizing responses in 40.0% and 46.7% of participants, respectively. In a phase 1 trial, 2 novel type 2 oral poliovirus vaccine candidates induced detectable poliovirus type 2-specific intestinal neutralizing responses in 40.0% and 46.7% of participants, respectively, suggesting potential utility for reducing circulating vaccine-derived poliovirus transmission under outbreak scenarios.

Convalescent plasma has emerged as a promising COVID-19 treatment. However, the humoral factors that contribute to efficacy are poorly understood. This study functionally and phenotypically profiled plasma from eligible convalescent donors. In addition to viral neutralization, convalescent plasma contained antibodies capable of mediating such Fc-dependent functions as complement activation, phagocytosis and antibody-dependent cellular cytotoxicity against SARS-CoV-2. These activities expand the antiviral functions associated with convalescent plasma and together with neutralization efficacy, could be accurately and robustly from antibody phenotypes. These results suggest that high-throughput profiling could be used to screen donors and plasma may provide benefits beyond neutralization.

Background The rate of facility births in Haiti has doubled over the past two decades, but without comparable reductions in maternal or neonatal mortality. To care for newborns requiring hospitalization in Haiti, we worked with the public health leadership in the Haitian department of the South (Sud) to establish a ward for compromised neonates in a large public hospital with over 3000 annual deliveries but no neonatal care capacity. Methods Significant investments were made in establishing basic neonatal services, training nurses, installing and managing a supply chain, and strengthening infrastructure. We present outcomes for 1399 neonates admitted to the ward during the first two years of operation. Results Two-thirds of admissions were made from the hospital’s maternity ward after birth, while the remaining babies were born at home or at referring facilities. Inborn neonates had better rates of hospital survival than those born elsewhere; they were also more likely to be born via cesarean section and to be admitted immediately following birth. Babies born elsewhere were more likely to die during their hospital stay. There were no differences between the proportion of premature or low-birth-weight babies born at the hospital or elsewhere. Nursing care proved to be a critical part of the care delivery system. Conclusions To support maternal and newborn care, we conclude that integrated, high-frequency nursing training is necessary for both maternity and neonatal nurses. Resources are needed to address prematurity as an important outcome, especially as it is indicative of poor prenatal care, regardless of place of birth.

Maternal antiretroviral therapy (ART) has effectively reduced but not eliminated the burden of mother-to-child transmission of HIV across the globe, as an estimated 160,000 children were newly infected with HIV in 2018. Thus, additional preventive strategies beyond ART will be required to close the remaining gap and end the pediatric HIV epidemic. A maternal active immunization strategy that synergizes with maternal ART could further reduce infant HIV infections. In this study, we found that two historic HIV Env vaccines did not enhance the ability of HIV-infected pregnant women to neutralize autologous viruses. Therefore, next-generation maternal HIV vaccine candidates must employ alternate approaches to achieve potent neutralizing antibody and perhaps nonneutralizing antibody responses to effectively impede vertical virus transmission. Moreover, these approaches must reflect the broad diversity of HIV strains and widespread availability of ART worldwide., A maternal vaccine capable of boosting neutralizing antibody (NAb) responses directed against circulating viruses in HIV-infected pregnant women could effectively decrease mother-to-child transmission of HIV. However, it is not known if an HIV envelope (Env) vaccine administered to infected pregnant women could enhance autologous virus neutralization and thereby reduce this risk of vertical HIV transmission. Here, we assessed autologous virus NAb responses in maternal plasma samples obtained from AIDS Vaccine Evaluation Group (AVEG) protocols 104 and 102, representing historical phase I safety and immunogenicity trials of recombinant HIV Env subunit vaccines administered to HIV-infected pregnant women (ClinicalTrials registration no. NCT00001041). Maternal HIV Env-specific plasma binding and neutralizing antibody responses were characterized before and after vaccination in 15 AVEG 104 (n = 10 vaccine recipients, n = 5 placebo recipients) and 2 AVEG 102 (n = 1 vaccine recipient, n = 1 placebo recipient) participants. Single-genome amplification (SGA) was used to obtain HIV env gene sequences of autologous maternal viruses for pseudovirus production and neutralization sensitivity testing in pre- and postvaccination plasma of HIV-infected pregnant vaccine recipients (n = 6 gp120, n = 1 gp160) and placebo recipients (n = 3). We detected an increase in Env subunit MN gp120-specific IgG binding in the group of vaccine recipients between the first immunization visit and the last visit at delivery (P = 0.027, 2-sided Wilcoxon test). While no difference was observed in the levels of autologous virus neutralization potency between groups, in both groups maternal plasma collected at delivery more effectively neutralized autologous viruses from early pregnancy than late pregnancy. Immunization strategies capable of further enhancing these autologous virus NAb responses in pregnant women will be important to block vertical transmission of HIV. IMPORTANCE Maternal antiretroviral therapy (ART) has effectively reduced but not eliminated the burden of mother-to-child transmission of HIV across the globe, as an estimated 160,000 children were newly infected with HIV in 2018. Thus, additional preventive strategies beyond ART will be required to close the remaining gap and end the pediatric HIV epidemic. A maternal active immunization strategy that synergizes with maternal ART could further reduce infant HIV infections. In this study, we found that two historic HIV Env vaccines did not enhance the ability of HIV-infected pregnant women to neutralize autologous viruses. Therefore, next-generation maternal HIV vaccine candidates must employ alternate approaches to achieve potent neutralizing antibody and perhaps nonneutralizing antibody responses to effectively impede vertical virus transmission. Moreover, these approaches must reflect the broad diversity of HIV strains and widespread availability of ART worldwide.

Background Understanding immunogenicity and safety of monovalent type 2 oral poliovirus vaccine (mOPV2) in inactivated poliovirus vaccine (IPV)–immunized children is of major importance in informing global policy to control circulating vaccine-derived poliovirus outbreaks. Methods In this open-label, phase 4 study (NCT02582255) in 100 IPV-vaccinated Lithuanian 1–5-year-olds, we measured humoral and intestinal type 2 polio neutralizing antibodies before and 28 days after 1 or 2 mOPV2 doses given 28 days apart and measured stool viral shedding after each dose. Parents recorded solicited adverse events (AEs) for 7 days after each dose and unsolicited AEs for 6 weeks after vaccination. Results After 1 mOPV2 challenge, the type 2 seroprotection rate increased from 98% to 100%. Approximately 28 days after mOPV2 challenge 34 of 68 children (50%; 95% confidence interval, 38%–62%) were shedding virus; 9 of 37 (24%; 12%–41%) were shedding 28 days after a second challenge. Before challenge, type 2 intestinal immunity was undetectable in IPV-primed children, but 28 of 87 (32%) had intestinal neutralizing titers ≥32 after 1 mOPV2 dose. No vaccine-related serious or severe AEs were reported. Conclusions High viral excretion after mOPV2 among exclusively IPV-vaccinated children was substantially lower after a subsequent dose, indicating induction of intestinal immunity against type 2 poliovirus.

Background We evaluated a Russian-backbone, live, attenuated influenza vaccine (LAIV) for immunogenicity and viral shedding in a randomized, placebo-controlled trial among Bangladeshi children. Methods Healthy children received a single, intranasal dose of LAIV containing the 2011–2012 recommended formulation or placebo. Nasopharyngeal wash (NPW) specimens were collected on days 0, 2, 4, and 7. Reverse transcription polymerase chain reactions and sequencing identified the influenza virus (vaccine or wild-type). On days 0 and 21, blood specimens were collected to assess immunogenicity using hemagglutination inhibition, microneutralization, and immunoglobulin A (IgA) and G enzyme-linked immunosorbent assays (ELISAs); NPW specimens were also collected to assess mucosal immunogenicity using kinetic IgA ELISA. Results We enrolled 300 children aged 24 through 59 months in the immunogenicity and viral shedding analyses. Among children receiving LAIV, 45% and 67% shed A/H3N2 and B vaccine strains, respectively. No child shed A/H1N1 vaccine strain. There were significantly higher day 21 geometric mean titers (GMTs) for the LAIV, as compared to the placebo groups, in all immunoassays for A/H3N2 and B (log10 titer P < .0001; GMT Ratio >2.0). Among immunoassays for A/H1N1, only the mucosal IgA GMT was significantly higher than placebo at day 21 (log10 titer P = .0465). Conclusions Children vaccinated with LAIV had serum and mucosal antibody responses to A/H3N2 and B, but only a mucosal IgA response to A/H1N1. Many children shed A/H3N2 and B vaccine strains, but none shed A/H1N1. More research is needed to determine the reason for decreased LAIV A/H1N1 immunogenicity and virus shedding. Clinical Trials Registration NCT01625689., In this Phase II trial of live, attenuated influenza vaccine in Bangladeshi children, we detected post-vaccination antibody responses to A/H3N2 and B viruses and viral shedding. However, we detected a reduced post-vaccination antibody response to A/H1N1 and no viral shedding.

Preventive strategies beyond ART will be required to end the pediatric HIV epidemic. A maternal vaccine capable of boosting neutralizing antibody (nAb) responses against circulating viruses in HIV-infected pregnant women could effectively decrease mother-to-child transmission of HIV. However, it is not known if an HIV envelope (Env) vaccine administered to infected pregnant women can enhance autologous virus neutralization.Here, we assessed autologous virus nAb responses in maternal plasma samples obtained from AIDS Vaccine Evaluation Group (AVEG) Protocols 104 and 102, historical Phase I safety and immunogenicity trials of recombinant HIV Env subunit vaccines in HIV-infected pregnant women (NCT00001041). AVEG 104 participants were randomized to receive 300 µg Env subunit MN recombinant gp120 with alum adjuvant or alum alone. AVEG 102 participants were randomized to receive 640 µg Env subunit recombinant gp160 or placebo. HIV Env-specific maternal plasma binding and neutralizing responses were characterized before and after vaccination in 15 AVEG 104 (n=10 vaccinee, n=5 placebo) and 2 AVEG 102 (n=1 vaccinee, n=1 placebo) participants. Single genome amplification (SGA) was used to obtain HIV env gene sequences from autologous viruses for pseudovirus production in pre- and post-vaccination plasma of HIV-infected pregnant vaccinees (n=6 gp120, n=1 gp160) and placebo recipients (n=3).We detected an increase in MN gp120-specific IgG binding in the vaccinee group between the first immunization visit and the last visit at delivery (p=0.027, 2-sided Wilcoxon test). However, no difference was observed in the neutralization potency of maternal plasma collected at delivery against autologous viruses isolated from early or late pregnancy. Thus, maternal vaccination with gp120/160 did not boost maternal autologous virus nAb responses. Immunization strategies capable of more potent B cell stimulation will likely be required to effectively boost autologous virus nAb responses in pregnant women and synergize with ART to further reduce infant HIV infections.HighlightsPrior maternal HIV Env vaccine trial did not assess autologous virus neutralizationCirculating viruses isolated from mothers were tested against autologous plasmaMaternal vaccination with HIV Env gp120/160 increased MN gp120-specific IgG bindingMaternal HIV Env vaccine regimen did not boost autologous virus neutralizationMore potent B cell stimulation will be required to elicit autologous nAb responses

To assess the incidence of obstetric complications-eclampsia, dystocia, cesarean section, postpartum hemorrhage, and stillbirths-in hospitals in southern Haiti in 2013 - 2016 and to discuss implications for improvements to the surveillance of birth outcomes.This was a cross-sectional, retrospective study of data for 32 442 deliveries recorded in 2013 - 2016 by the Integrated Monitoring, Evaluation, and Surveillance System for facilities across three departments and one high-volume hospital in southern Haiti. Annual incidence rates of eclampsia, dystocia, cesarean section, postpartum hemorrhage, and stillbirths (both macerated and fresh) were calculated.The incidence of eclampsia in the study sample was 2% - 3% and of dystocia approximately 5%, comparable to elsewhere in Haiti and other low-income countries. Cesarean delivery rates averaged about 15% annually. Postpartum hemorrhage rates were lower than published data from similar settings. Stillbirth rates ranged from 30 - 62 per 1 000 births at all facilities, higher than previously recorded by the country's population surveys. The rates of macerated stillbirths were remarkably high, close to 50% of total stillbirths, indicating severe delays in seeking or receiving emergency obstetric care.This study provides important benchmarks for the current burden of preventable labor- and delivery-related complications in Haiti. Surveillance data suggest an urgent need for the management of hypertensive disorders during pregnancy, timely cesarean sections for dystocia, and management and treatment of postpartum hemorrhage in Haiti. Frequent data reviews may help address facility-specific bottlenecks.Evaluar la incidencia de las complicaciones obstétricas, como la eclampsia, la distocia, las cesáreas, la hemorragia posparto y la mortinatalidad, en los hospitales del sur de Haití en el período comprendido entre los años 2013 y 2016, y analizar las implicaciones para realizar mejoras en la vigilancia de los resultados perinatales.Se trata de un estudio transversal y retrospectivo de los datos de 32 442 partos registrados en el período 2013-2016 mediante el sistema integrado de seguimiento, evaluación y vigilancia para establecimientos en tres departamentos y un hospital de gran actividad en el sur de Haití. Se calcularon las tasas de incidencia anuales de eclampsia, distocia, cesáreas y hemorragia posparto, así como de mortinatalidad (mortinatos macerados y frescos).La incidencia de eclampsia en la muestra de estudio fue de entre 2% y 3% y de distocia, de aproximadamente 5%, equiparable a cualquier lugar en Haití y otros países de ingresos bajos. Las tasas promedio de parto por cesárea se aproximaron al 15% anual. Las tasas de hemorragia posparto fueron inferiores a los datos publicados sobre entornos similares. Las tasas de mortinatalidad comprendieron entre 30 y 62 por 1 000 nacimientos en la totalidad de establecimientos, un resultado mayor al que registrado con anterioridad en las encuestas de población del país. Las tasas de mortinatos macerados fueron notablemente elevadas, cerca de 50% de la mortinatalidad total, lo que pone de manifiesto retrasos graves a la hora de solicitar u obtener atención obstétrica de urgencia.Este estudio ofrece puntos de referencia relevantes para la carga actual de complicaciones prevenibles del embarazo y el parto en Haití. Los datos de vigilancia indican que existe una urgente necesidad de tratamiento de los trastornos hipertensivos durante el embarazo, de cesáreas por distocia a tiempo, y de atención y tratamiento de la hemorragia posparto en Haití. Para abordar los obstáculos propios de los establecimientos puede ser útil realizar análisis frecuentes de los datos.Avaliar a incidência de complicações obstétricas – eclâmpsias, distocias, cesarianas, hemorragias pós-parto e natimortos – em hospitais na região Sul do Haiti no período de 2013 a 2016 e discutir as implicações para melhorar a vigilância dos resultados dos partos.Este foi um estudo transversal, retrospectivo, com dados de 32 442 partos registrados pelo Sistema Integrado de Monitoramento, Avaliação e Vigilância para estabelecimentos de saúde situados em três divisões político-administrativas (denominadas de departamentos) e um hospital de alto volume, todos situados na região Sul do Haiti, no período de 2013 a 2016. Foram calculadas as taxas anuais de incidência de eclâmpsias, distocias, cesarianas, hemorragias pós-parto e natimortos (macerados e frescos).Na amostra do estudo, a taxa de incidência de eclâmpsias foi de 2 a 3%, e a de partos distócicos de aproximadamente 5%, comparáveis com as de outras localidades no Haiti e com outros países de baixa renda; as cesarianas apresentaram média anual de aproximadamente 15%; as taxas de hemorragia pós-parto foram menores que as publicadas sobre estabelecimentos similares. Em todos os estabelecimentos, as taxas de partos de natimortos variaram de 30 a 62 por 1 000 nascimentos, sendo mais altas que as anteriormente registradas pelos levantamentos populacionais do país. As taxas de natimortos macerados foram excepcionalmente altas, aproximadamente 50% do total de partos de natimortos, o que indica que há graves atrasos, seja na procura por atenção obstétrica de emergência ou no recebimento dessa atenção.Esse estudo fornece importantes parâmetros para determinar a atual carga de complicações passíveis de prevenção relacionadas com o trabalho de parto e com o parto propriamente dito no Haiti. Os dados de vigilância sugerem que, no Haiti, há uma necessidade urgente de manejar distúrbios hipertensivos durante a gestação, realizar cesarianas em tempo oportuno nos casos de distocias e manejar e tratar hemorragias pós-parto. Revisões frequentes dos dados podem ajudar a identificar os gargalos específicos de cada estabelecimento.

Background Acute flaccid myelitis (AFM) is a polio-like paralyzing illness of children. AFM incidence is increasing during every other year outbreaks that occur in the United States simultaneously with outbreaks of enterovirus D68 (EV-D68) infection. Demonstrating that EV-D68 directly causes AFM has been challenging due to rare detection of the virus in the cerebrospinal fluid (CSF) of patients despite frequent detection at nonsterile sites. Murine studies have shown that EV-D68 can infect spinal cord anterior horn motor neurons and cause paralysis, similar to poliovirus. However, a key outstanding question is whether EV-D68 causes AFM in humans by direct viral pathogenesis or by indirect host immunopathogenesis. Methods We investigated the pathogenesis of AFM using tissues from a previously reported case of a 5-year-old boy who presented in fall 2008 with four days of progressive limb and voice weakness followed by incontinence, apnea, and death. He had a CSF pleocytosis of 2094/µL with EV-D68 identified in the CSF by sequencing of the VP1 gene. We designed probes for in situ hybridization (ISH) based on this sequence to stain formalin fixed paraffin embedded tissues from his autopsy. For immunohistochemistry (IHC) we used both commercial polyclonal anti-EV-D68 antibodies and our own human monoclonal antibodies that stain virus infected cells in vitro. Immunophenotyping was done by IHC. To analyze gene transcription in the inflammatory transcriptome of these infected areas of spinal cord we used the GeoMx platform from Nanostring. Results We identified EV-D68 in the anterior horn of the patient’s spinal cord, corresponding to the location of motor neuron cell bodies. This area was highly inflamed, with an infiltrate of CD8 T cells and many macrophages. Viral RNA (see figure) and viral protein was visualized in motor neurons but not supporting cells using ISH and IHC, respectively. Viral RNA but not viral protein was detected rarely in the lungs in macrophages, which had extensive inflammatory infiltrate. The infiltrate was predominantly composed of macrophages with a CD8 T cell component as well. The transcriptome of cells in the inflamed tissue was enriched for genes involved in antigen presentation on MHC. Conclusions Deaths in AFM patients are rare and often distant from initial presentation, but this patient died four days after onset of weakness, allowing us to directly demonstrate that EV-D68 can infect the human spinal cord. Motor neurons but not neural support cells are directly infected by EV-D68 with a corresponding infiltrate of macrophages and CD8 T cells. Antigen presentation processes are upregulated in inflamed tissues. Therefore, both direct viral pathology and immune factors likely contribute to AFM disease in EV-D68 infection.

Background We aimed to determine whether the Xpert MTB/RIF (Xpert) assay is a useful adjunct to culture for the rapid diagnosis of tuberculosis (TB) using gastric lavage aspirates (GLAs) in children aged Methods We reviewed the yield from diagnostic modalities in children suspected of having TB followed at an infectious disease research and treatment center in Port-au-Prince, Haiti, from 2011 to 2016. Results In 187 children clinically diagnosed with TB, a microbiologic diagnosis could be established in 40 (21%). Cultures, Xpert, and smears were positive in 30 (19%), 28 (17%), and 3 (1.6%) children, respectively. Ten cases that would not have been diagnosed by culture alone were found by the use of the Xpert assay. Collecting 2 GLA samples optimized microbiologic yield. Conclusions In GLAs, Xpert increased the yield of microbiologically documented cases by 33%. Additionally, the rapidity of diagnosis potentially makes Xpert a valuable adjunct in initiating treatment for TB in children. Smear microscopy has low sensitivity in GLA and did not add to the documented cases. Our findings also highlight the low rate of microbiologic confirmation of clinically diagnosed TB.

Respiratory syncytial virus (RSV) is a leading cause of hospitalization in infants and young children. Although it is widely agreed that an RSV vaccine should induce both mucosal and systemic antibody responses, little is known about the B cell response to RSV in mucosa-associated lymphoid tissues. Here, we analyze this response by isolating 806 RSV F-specific antibodies from paired adenoid and peripheral blood samples from 4 young children. Overall, the adenoid-derived antibodies show higher binding affinities and neutralization potencies compared to antibodies isolated from peripheral blood. Approximately 25% of the neutralizing antibodies isolated from adenoids originate from a unique population of IgM+ and/or IgD+ memory B cells that contain a high load of somatic mutations but lack expression of classical memory B cell markers. Altogether, the results provide insight into the local B cell response to RSV and have implications for the development of vaccines that stimulate potent mucosal responses., Here, the authors isolate over 800 RSV F-specific antibodies from paired nasopharyngeal tonsil and peripheral blood samples from four young children undergoing adenoidectomy and find that adenoid derived antibodies have overall higher binding affinities and neutralization potencies.

Influenza viruses are a continuous threat to humans because of their ability to cross species barriers and adapt to new hosts. Data from murine studies, along with limited human data, suggest that CD8(+) cytotoxic T lymphocytes (CTL) that recognize conserved epitopes of structural influenza proteins are the main mediators of influenza virus clearance. Additionally, the fact that many CTLs recognize epitopes shared between different influenza strains offers the potential for broad cross-strain immunity. However, the mechanisms of cellular immunity against influenza viruses are poorly defined in humans, where the CTL response has been hard to measure and interpret. We developed a novel CTL assay that utilizes fully differentiated nasal human epithelial cells taken from volunteers as permissive targets for autologous peripheral blood-derived influenza virus-specific cytotoxic T lymphocytes. This in vitro system of human lymphocyte-epithelial cell co-cultures can be considered as the closest approximation to events in vivo and can be employed for studying the interactions between the pathogen and human host. Modeling of the natural interaction process between the primary cell type that supports the productive replication of influenza and immune cells may allow us to put in perspective CTLs as a correlate of immunity to influenza in humans.

Background. Preventing mother-to-child transmission of HIV relies on engagement in care during the prenatal, peripartum, and postpartum periods. Under PMTCT Option B, pregnant women with elevated CD4 counts are provided with antiretroviral prophylaxis until cessation of breastfeeding.Methods. Retrospective analysis of retention in care among HIV-infected pregnant women in Haiti was performed. Logistic regression was used to identify risk factors associated with loss to follow-up (LFU) defined as no medical visit for at least 6 months and Kaplan-Meier curves were created to show LFU timing.Results. Women in the cohort had 463 pregnancies between 2009 and 2012 with retention rates of 80% at delivery, 67% at one year, and 59% at 2 years. Among those who were LFU, the highest risk period was during pregnancy (60%) or shortly afterwards (24.4% by 12 months). Never starting on antiretroviral therapy (aRR 2.29, 95% CI 1.4–3.8) was associated with loss to follow-up.Conclusions. Loss to follow-up during and after pregnancy was common in HIV-infected women in Haiti under PMTCT Option B. Since sociodemographic factors and distance from home to facility did not predict LFU, future work should elicit and address barriers to retention at the initial prenatal care visit in all women. Better tracking systems to capture engagement in care in the wider network are needed.

Background Acute flaccid myelitis (AFM) is a polio-like paralyzing illness of children. AFM incidence is increasing during every other year outbreaks that occur in the United States simultaneously with outbreaks of enterovirus D68 (EV-D68) infection. Demonstrating that EV-D68 directly causes AFM has been challenging due to rare detection of the virus in the cerebrospinal fluid (CSF) of patients despite frequent detection at nonsterile sites. Murine studies have shown that EV-D68 can infect spinal cord anterior horn motor neurons and cause paralysis, similar to poliovirus. However, a key outstanding question is whether EV-D68 causes AFM in humans by direct viral pathogenesis or by indirect host immunopathogenesis. Methods We investigated the pathogenesis of AFM using tissues from a previously reported case of a 5-year-old boy who presented in fall 2008 with four days of progressive limb and voice weakness followed by incontinence, apnea, and death. He had a CSF pleocytosis of 2094/µL with EV-D68 identified in the CSF by sequencing of the VP1 gene. We designed probes for in situ hybridization (ISH) based on this sequence to stain formalin fixed paraffin embedded tissues from his autopsy. For immunohistochemistry (IHC) we used both commercial polyclonal anti-EV-D68 antibodies and our own human monoclonal antibodies that stain virus infected cells in vitro. Immunophenotyping was done by IHC. Results With ISH we identified EV-D68 RNA in the anterior horn of the patient’s spinal cord, corresponding to the location of motor neuron cell bodies. This area was highly inflamed, with an infiltrate of lymphocytes and macrophages. Viral RNA was in low abundance, and we could not detect viral surface proteins by IHC. Neither RNA nor viral antigen was detected in the lungs, which had extensive inflammatory infiltrate. Conclusion Deaths in AFM patients are rare and often distant from initial presentation, but this patient died four days after onset of weakness, allowing us to directly demonstrate that EV-D68 can infect the human spinal cord. Low abundance of virus suggests the virus either reached the spinal cord prior to weakness onset or was cleared rapidly by the immune response. Therefore, both direct viral pathology and immune factors likely contribute to AFM disease in EV-D68 infection. Disclosures James E. Crowe, Jr, MD, IDBiologics (Board Member, Consultant, Grant/Research Support)Vanderbilt University (Other Financial or Material Support, Inventor on patent related to this abstract)

Background Children are susceptible to severe influenza infections and facilitate community transmission. One potential strategy to improve vaccine immunogenicity in children against seasonal influenza involves a trivalent hemagglutinin DNA prime-trivalent inactivated influenza vaccine (IIV3) boost regimen. Methods Sites enrolled adolescents, followed by younger children, to receive DNA prime (1 mg or 4 mg) intramuscularly by needle-free jet injector (Biojector), followed by split virus 2012/13 seasonal IIV3 boost by needle and syringe approximately 18 weeks later. A comparator group received IIV3 prime and boost at similar intervals. Primary study objectives included evaluation of the safety and tolerability of the vaccine regimens, with secondary objectives of measuring antibody responses at four weeks post boost by hemagglutination inhibition (HAI) and neutralization assays. Results Seventy-five children ≥6 to ≤17 years old enrolled. Local reactogenicity was higher after DNA prime compared to IIV3 prime (p

Summary Respiratory syncytial virus (RSV) is a leading cause of infant mortality, and there are currently no licensed vaccines to protect this vulnerable population. A comprehensive understanding of infant antibody responses to natural RSV infection would facilitate vaccine development. Here, we isolated more than 450 RSV fusion glycoprotein (F)-specific antibodies from 7 RSV-infected infants and found that half of the antibodies recognized only two antigenic sites. Antibodies targeting both sites showed convergent sequence features, and structural studies revealed the molecular basis for their recognition of RSV F. A subset of antibodies targeting one of these sites displayed potent neutralizing activity despite lacking somatic mutations, and similar antibodies were detected in RSV-naive B cell repertoires, suggesting that expansion of these B cells in infants may be possible with suitably designed vaccine antigens. Collectively, our results provide fundamental insights into infant antibody responses and a framework for the rational design of age-specific RSV vaccines.

Background Identifying polio vaccine regimens that can elicit robust intestinal mucosal immunity and interrupt viral transmission is a key priority of the polio endgame. Methods In a 2013 Chilean clinical trial (NCT01841671) of trivalent inactivated polio vaccine (IPV) and bivalent oral polio vaccine (bOPV; targeting types 1 and 3), infants were randomized to receive IPV-bOPV-bOPV, IPV-IPV-bOPV, or IPV-IPV-IPV at 8, 16, and 24 weeks of age and challenged with monovalent oral polio vaccine type 2 (mOPV2) at 28 weeks. Using fecal samples collected from 152 participants, we investigated the extent to which IPV-bOPV and IPV-only immunization schedules induced intestinal neutralizing activity and immunoglobulin A against polio types 1 and 2. Results Overall, 37% of infants in the IPV-bOPV groups and 26% in the IPV-only arm had detectable type 2–specific stool neutralization after the primary vaccine series. In contrast, 1 challenge dose of mOPV2 induced brisk intestinal immune responses in all vaccine groups, and significant rises in type 2–specific stool neutralization titers (P < .0001) and immunoglobulin A concentrations (P < 0.0001) were measured 2 weeks after the challenge. In subsidiary analyses, duration of breastfeeding also appeared to be associated with the magnitude of polio-specific mucosal immune parameters measured in infant fecal samples. Conclusions Taken together, these results underscore the concept that mucosal and systemic immune responses to polio are separate in their induction, functionality, and potential impacts on transmission and, specifically, provide evidence that primary vaccine regimens lacking homologous live vaccine components are likely to induce only modest, type-specific intestinal immunity.

Untargeted metabolomics study of volatile organic compounds produced by different cell cultures is a field that has gained increasing attention over the years. Solid-phase microextraction has been the sampling technique of choice for most of the applications mainly due to its simplicity to implement. However, a careful optimization of the analytical conditions is necessary to obtain the best performances, which are highly matrix-dependent. In this work, five different solid-phase microextraction fibers were compared for the analysis of the volatiles produced by cell culture infected with the human respiratory syncytial virus. A central composite design was applied to determine the best time-temperature combination to maximize the extraction efficiency and the salting-out effect was evaluated as well. The linearity of the optimized method, along with limits of detection and quantification and repeatability was assessed. Finally, the effect of i) different normalization techniques (i.e. z-score and probabilistic quotient normalization), ii) data transformation (i.e. in logarithmic scale), and iii) different feature selection algorithms (i.e. Fisher ratio and random forest) on the capability of discriminating between infected and not-infected cell culture was evaluated.

Tuberculosis (TB) remains a global public health malady that claims almost 1.8 million lives annually. Diagnosis of TB represents perhaps one of the most challenging aspects of tuberculosis control. Gold standards for diagnosis of active TB (culture and nucleic acid amplification) are sputum-dependent, however, in up to a third of TB cases, an adequate biological sputum sample is not readily available. The analysis of exhaled breath, as an alternative to sputum-dependent tests, has the potential to provide a simple, fast, and non-invasive, and ready-available diagnostic service that could positively change TB detection. Human breath has been evaluated in the setting of active tuberculosis using thermal desorption-comprehensive two-dimensional gas chromatography–time of flight mass spectrometry methodology. From the entire spectrum of volatile metabolites in breath, three random forest machine learning models were applied leading to the generation of a panel of 46 breath features. The twenty-two common features within each random forest model used were selected as a set that could distinguish subjects with confirmed pulmonary M. tuberculosis infection and people with other pathologies than TB.

Background. Live attenuated influenza vaccine (LAIV) and inactivated influenza vaccine (IIV) are available for children. Local and systemic immunity induced by LAIV followed a month later by LAIV and IIV followed by LAIV were investigated with virus recovery after LAIV doses as surrogates for protection against influenza on natural exposure. Methods. Fifteen children received IIV followed by LAIV, 13 an initial dose of LAIV, and 11 a second dose of LAIV. The studies were done during autumn 2009 and autumn 2010 with the same seasonal vaccine (A/California/07/09 [H1N1], A/Perth/16/09 [H3N2], B/Brisbane/60/08). Results. Twenty-eight of 39 possible influenza viral strains were recovered after the initial dose of LAIV. When LAIV followed IIV, 21 of 45 viral strains were identified. When compared to primary LAIV infection, the decreased frequency of shedding with the IIV-LAIV schedule was significant (P = .023). With LAIV-LAIV, the fewest viral strains were recovered (3/33)—numbers significantly lower (P < .001) than shedding after initial LAIV and after IIV-LAIV (P < .001). Serum hemagglutination inhibition antibody responses were more frequent after IIV than LAIV (P = .02). In contrast, more mucosal immunoglobulin A responses were seen with LAIV. Conclusions. LAIV priming induces greater inhibition of virus recovery on LAIV challenge than IIV priming. The correlate(s) of protection are the subject of ongoing analysis. Clinical Trials Registration. {"type":"clinical-trial","attrs":{"text":"NCT01246999","term_id":"NCT01246999"}}NCT01246999.

BACKGROUND Response to challenge with live, attenuated, oral polio vaccine (OPV) is a measure of immunity induced by prior immunization. METHODS Using stool samples from a study from Oman in which an initial schedule of inactivated polio vaccine (IPV) was followed by an OPV type 1 challenge, we quantitated virus shed, sequenced capsid proteins of recovered virus, and developed assays for neutralization of poliovirus and mucosal immunoglobulin A (IgA) detection. RESULTS Neutralizing activity correlated with detection of polio-specific IgA in stool suspensions collected 7 days after OPV type 1 challenge. Both neutralization and IgA in stool were associated with cessation of virus shedding by day 7. Rapid development of an IgA response with cessation of shedding suggests that IPV primed for the early response to challenge. Correlation of neutralization activity and IgA detection provides evidence that polio-specific IgA intestinal antibody is a determinant of mucosal shedding/transmission and that IgA functions through neutralization of virus. In contrast, neither presence nor quantity of serum or intestinal antibody induced by IPV prior to challenge correlated with cessation of shedding. CONCLUSIONS These assays provide an opportunity to study other immunization schedules to gain a broader understanding of the appearance and duration of a protective mucosal response to polio vaccination.

Respiratory syncytial virus (RSV) causes substantial morbidity and mortality in young children and the elderly. There are currently no licensed RSV vaccines, and passive prophylaxis with the monoclonal antibody palivizumab is restricted to high-risk infants in part due to its modest efficacy. Although it is widely agreed that an effective RSV vaccine will require the induction of a potent neutralizing antibody response against the RSV fusion (F) glycoprotein, little is known about the specificities and functional activities of RSV F-specific antibodies induced by natural infection. Here, we have comprehensively profiled the human antibody response to RSV F by isolating and characterizing 364 RSV F-specific monoclonal antibodies from the memory B cells of three healthy adult donors. In all donors, the antibody response to RSV F is comprised of a broad diversity of clones that target several antigenic sites. Nearly half of the most potent antibodies target a previously undefined site of vulnerability near the apex of the prefusion conformation of RSV F (preF), providing strong support for the development of RSV vaccine candidates that preserve the membrane-distal hemisphere of the preF protein. Additionally, the antibodies targeting this new site display convergent sequence features, thus providing a future means to rapidly detect the presence of these antibodies in human vaccine samples. Many of the antibodies that bind preF-specific surfaces are over 100 times more potent than palivizumab, and several cross-neutralize human metapneumovirus (HMPV). Taken together, the results have implications for the design and evaluation of RSV vaccine candidates and offer new options for passive prophylaxis. We thank Tushar Jain for guidance on statistical analyses, Todd Boland for assistance with antibody sequence analysis, Emilie Shipman for assistance with protein expression, Wen Li for technical assistance, Cody Williams and S.M. Eagol for assistance with figure preparation, and Margaret Ackerman for use of the magnetic microplate washer (BioTek) and the FLEXMAP 3D flow cytometer (Luminex). PBMC processing was carried out in DartLab, the Immune Monitoring and Flow Cytometry Shared Resource, supported by a National Cancer Institute Cancer Center Support Grant to the Norris Cotton Cancer Center (P30CA023108-37) and an Immunology COBRE Grant (P30GM103415-15) from the National Institute of General Medical Sciences. All the IgGs were sequenced by Adimab's Molecular Core and produced by the High Throughput Expression group. Biolayer interferometry binding experiments were performed by Adimab's protein analytics group. Funding: Support for this work was provided by the National Institute of General Medical Sciences of the National Institutes of Health award T32GM008704 (M.S.A.G.) and P20GM113132 (J.S.M.) and intramural funding from the National Institute of Allergy and Infectious Diseases to support work at the Vaccine Research Center (B.S.G.). This work was partially supported by grant SAF2015-67033-R to J.A.M. from Plan Nacional I+D+i. Sí