A Zika virus-specific IgM elicited in pregnancy exhibits ultrapotent neutralization.

Congenital Zika virus (ZIKV) infection results in neurodevelopmental deficits in up to 14% of infants born to ZIKV-infected mothers. Neutralizing antibodies are a critical component of protective immunity. Here, we demonstrate that plasma IgM contributes to ZIKV immunity in pregnancy, mediating neutralization up to 3 months post-symptoms. From a ZIKV-infected pregnant woman, we isolated a pentameric ZIKV-specific IgM (DH1017.IgM) that exhibited ultrapotent ZIKV neutralization dependent on the IgM isotype. DH1017.IgM targets an envelope dimer epitope within domain II. The epitope arrangement on the virion is compatible with concurrent engagement of all ten antigen-binding sites of DH1017.IgM, a solution not available to IgG. DH1017.IgM protected mice against viremia upon lethal ZIKV challenge more efficiently than when expressed as an IgG. Our findings identify a role for antibodies of the IgM isotype in protection against ZIKV and posit DH1017.IgM as a safe and effective candidate immunotherapeutic, particularly during pregnancy.

Characterization of Plasma Immunoglobulin G Responses in Elite Neutralizers of Human Cytomegalovirus.

BACKGROUND: Human cytomegalovirus (HCMV) is the most common infectious complication of organ transplantation and cause of birth defects worldwide. There are limited therapeutic options and no licensed vaccine to prevent HCMV infection or disease. To inform development of HCMV antibody-based interventions, a previous study identified individuals with potent and broad plasma HCMV-neutralizing activity, termed elite neutralizers (ENs), from a cohort of HCMV-seropositive (SP) blood donors. However, the specificities and functions of plasma antibodies associated with EN status remained undefined. METHODS: We sought to determine the plasma antibody specificities, breadth, and Fc-mediated antibody effector functions associated with the most potent HCMV-neutralizing responses in plasma from ENs (n = 25) relative to that from SP donors (n = 19). We measured antibody binding against various HCMV strains and glycoprotein targets and evaluated Fc-mediated effector functions, antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP). RESULTS: We demonstrate that ENs have elevated immunoglobulin G binding responses against multiple viral glycoproteins, relative to SP donors. Our study also revealed potent HCMV-specific antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis activity of plasma from ENs. CONCLUSIONS: We conclude that antibody responses against multiple glycoprotein specificities may be needed to achieve potent plasma neutralization and that potently HCMV elite-neutralizing plasma antibodies can also mediate polyfunctional responses.

Frequent Development of Broadly Neutralizing Antibodies in Early Life in a Large Cohort of Children With Human Immunodeficiency Virus.

BACKGROUND: Recent studies have indicated that broadly neutralizing antibodies (bnAbs) in children may develop earlier after human immunodeficiency virus (HIV) infection compared to adults. METHODS: We evaluated plasma from 212 antiretroviral therapy-naive children with HIV (1-3 years old). Neutralization breadth and potency was assessed using a panel of 10 viruses and compared to adults with chronic HIV. The magnitude, epitope specificity, and immunoglobulin (Ig)G subclass distribution of Env-specific antibodies were assessed using a binding antibody multiplex assay. RESULTS: One-year-old children demonstrated neutralization breadth comparable to chronically infected adults, whereas 2- and 3-year-olds exhibited significantly greater neutralization breadth (P = .014). Likewise, binding antibody responses increased with age, with levels in 2- and 3-year-old children comparable to adults. Overall, there was no significant difference in antibody specificities or IgG subclass distribution between the pediatric and adult cohorts. It is interesting to note that the neutralization activity was mapped to a single epitope (CD4 binding site, V2 or V3 glycans) in only 5 of 38 pediatric broadly neutralizing samples, which suggests that most children may develop a polyclonal neutralization response. CONCLUSIONS: These results contribute to a growing body of evidence suggesting that initiating HIV immunization early in life may present advantages for the development of broadly neutralizing antibody responses.

Bridging Vaccine-Induced HIV-1 Neutralizing and Effector Antibody Responses in Rabbit and Rhesus Macaque Animal Models.

Studies in animal models are essential prerequisites for clinical trials of candidate HIV vaccines. Small animals, such as rabbits, are used to evaluate promising strategies prior to further immunogenicity and efficacy testing in nonhuman primates. Our goal was to determine how HIV-specific vaccine-elicited antibody responses, epitope specificity, and Fc-mediated functions in the rabbit model can predict those in the rhesus macaque (RM) model. Detailed comparisons of the HIV-1-specific IgG response were performed on serum from rabbits and RM given identical modified vaccinia virus Ankara-prime/gp120-boost immunization regimens. We found that vaccine-induced neutralizing antibody, gp120-binding antibody levels and immunodominant specificities, antibody-dependent cellular phagocytosis of HIV-1 virions, and antibody-dependent cellular cytotoxicity (ADCC) responses against gp120-coated target cells were similar in rabbits and RM. However, we also identified characteristics of humoral immunity that differed across species. ADCC against HIV-infected target cells was elicited in rabbits but not in RM, and we observed differences among subdominantly targeted epitopes. Human Fc receptor binding assays and analysis of antibody-cell interactions indicated that rabbit vaccine-induced antibodies effectively recruited and activated human natural killer cells, while vaccine-elicited RM antibodies were unable to activate either human or RM NK cells. Thus, our data demonstrate that both Fc-independent and Fc-dependent functions of rabbit antibodies can be measured with commonly used in vitro assays; however, the ability of immunogenicity studies performed in rabbits to predict responses in RM will vary depending on the particular immune parameter of interest.IMPORTANCE Nonneutralizing antibody functions have been associated with reduced infection risk, or control of virus replication, for HIV-1 and related viruses. It is therefore critical to evaluate development of these responses throughout all stages of preclinical testing. Rabbits are conventionally used to evaluate the ability of vaccine candidates to safely elicit antibodies that bind and neutralize HIV-1. However, it remained unexplored how effectively rabbits model the development of nonneutralizing antibody responses in primates. We administered identical HIV-1 vaccine regimens to rabbits and rhesus macaques and performed detailed comparisons of vaccine-induced antibody responses. We demonstrated that nonneutralizing HIV-specific antibody responses can be studied in the rabbit model and have identified aspects of these responses that are common, and those that are unique, to rabbits and rhesus macaques. Our findings will help determine how to best utilize preclinical rabbit and rhesus macaque models to accelerate HIV vaccine candidate testing in human trials.

Simian-Human Immunodeficiency Virus SHIV.CH505-Infected Infant and Adult Rhesus Macaques Exhibit Similar Env-Specific Antibody Kinetics, despite Distinct T-Follicular Helper and Germinal Center B Cell Landscapes.

Global elimination of pediatric human immunodeficiency virus (HIV) infections will require the development of novel immune-based approaches, and understanding infant immunity to HIV is critical to guide the rational design of these intervention strategies. Despite their immunological immaturity, chronically HIV-infected children develop broadly neutralizing antibodies (bnAbs) more frequently and earlier than adults do. However, the ontogeny of humoral responses during acute HIV infection is poorly defined in infants and challenging to study in human cohorts due to the presence of maternal antibodies. To further our understanding of age-related differences in the development of HIV-specific immunity during acute infection, we evaluated the generation of virus-specific humoral immune responses in infant (n = 6) and adult (n = 12) rhesus macaques (RMs) infected with a transmitted/founder (T/F) simian-human immunodeficiency virus (SHIV) (SHIV.C.CH505 [CH505]). The plasma HIV envelope-specific IgG antibody kinetics were similar in SHIV-infected infant and adult RMs, with no significant differences in the magnitude or breadth of these responses. Interestingly, autologous tier 2 virus neutralization responses also developed with similar frequencies and kinetics in infant and adult RMs, despite infants exhibiting significantly higher follicular T helper cell (Tfh) and germinal center B cell frequencies than adults. Finally, we show that plasma viral load was the strongest predictor of the development of autologous virus neutralization in both age groups. Our results indicate that the humoral immune response to SHIV infection develops with similar kinetics among infant and adult RMs, suggesting that the early-life immune system is equipped to respond to HIV-1 and promote the production of neutralizing HIV antibodies.IMPORTANCE There is a lack of understanding of how the maturation of the infant immune system influences immunity to HIV infection or how these responses differ from those of adults. Improving our knowledge of infant HIV immunity will help guide antiviral intervention strategies that take advantage of the unique infant immune environment to successfully elicit protective immune responses. We utilized a rhesus macaque model of SHIV infection as a tool to distinguish the differences in HIV humoral immunity in infants versus adults. Here, we demonstrate that the kinetics and quality of the infant humoral immune response to HIV are highly comparable to those of adults during the early phase of infection, despite distinct differences in their Tfh responses, indicating that slightly different mechanisms may drive infant and adult humoral immunity.

Coadministration of CH31 Broadly Neutralizing Antibody Does Not Affect Development of Vaccine-Induced Anti-HIV-1 Envelope Antibody Responses in Infant Rhesus Macaques.

Prevention of mother-to-child transmission (MTCT) is an indispensable component in combatting the global AIDS epidemic. A combination of passive broadly neutralizing antibody (bnAb) infusion and active vaccination promises to provide protection of infants against MTCT from birth through the breastfeeding period and could prime the immune system for lifelong immunity. In this study, we investigate the impact of a single infusion of CD4 binding site (CD4bs) bnAb administered at birth on de novo antibody responses elicited by concurrent active HIV envelope vaccination. Four groups of infant macaques received active immunizations with subunit Env protein or modified vaccinia Ankara (MVA)-vectored Env and subunit Env protein, with or without a single intravenous coadministration of CH31 bnAb at birth. Vaccinated animals were monitored to evaluate binding and functional antibody responses elicited by the active vaccinations. Despite achieving plasma concentrations that were able to neutralize tier 2 viruses, coadministration of CH31 did not have a large impact on the kinetics, magnitude, specificity, or avidity of vaccine-elicited binding or functional antibody responses, including epitope specificity, the development of CD4bs antibodies, neutralization, binding to infected cells, or antibody-dependent cell-mediated cytotoxicity (ADCC). We conclude that infusion of CD4bs bnAb CH31 at birth does not interfere with de novo antibody responses to active vaccination and that a combination of passive bnAb infusion and active HIV-1 Env vaccination is a viable strategy for immediate and prolonged protection against MTCT.IMPORTANCE Our study is the first to evaluate the impact of passive infusion of a broadly neutralizing antibody in newborns on the de novo development of antibody responses following active vaccinations in infancy. We demonstrated the safety and the feasibility of bnAb administration to achieve biologically relevant levels of the antibody and showed that the passive infusion did not impair the de novo antibody production following HIV-1 Env vaccination. Our study paves the way for further investigations of the combination strategy using passive plus active immunization to provide protection of infants born to HIV-1-positive mothers over the entire period of risk for mother-to-child transmission.

Adjuvant-Dependent Enhancement of HIV Env-Specific Antibody Responses in Infant Rhesus Macaques.

Toward the goal of developing an effective HIV vaccine that can be administered in infancy to protect against postnatal and lifelong sexual HIV transmission risks, the current pilot study was designed to compare the effect of novel adjuvants on the induction of HIV Env-specific antibody responses in infant macaques. Aligning our studies with the adjuvanted proteins evaluated in a prime-boost schedule with ALVAC in the ongoing HVTN (HIV Vaccine Trials Network) 702 efficacy trial, we selected the bivalent clade C Env immunogens gp120 C.1086 and gp120 TV1 in combination with the MF59 adjuvant. However, we hypothesized that the adjuvant system AS01, that is included in the pediatric RTS,S malaria vaccine, would promote Env-specific antibody responses superior to those of the oil-in-water MF59 emulsion adjuvant. In a second study arm, we compared two emulsions, glucopyranosyl lipid adjuvant formulated in a stable emulsion (GLA-SE) and 3M-052-SE, containing Toll-like receptor 4 (TLR4) and TLR7/TLR8 (TLR7/8) ligand, respectively. The latter adjuvant had been previously demonstrated to be especially effective in activating neonatal antigen-presenting cells. Our results demonstrate that different adjuvants drive quantitatively or qualitatively distinct responses to the bivalent Env vaccine. AS01 induced higher Env-specific plasma IgG antibody levels than the antigen in MF59 and promoted improved antibody function in infants, and 3M-052-SE outperformed GLA-SE by inducing the highest breadth and functionality of antibody responses. Thus, distinct adjuvants are likely to be required for maximizing vaccine-elicited immune responses in infants, particularly when immunization in infancy aims to elicit both perinatal and lifelong immunity against challenging pathogens such as HIV.IMPORTANCE Alum remains the adjuvant of choice for pediatric vaccines. Yet the distinct nature of the developing immune system in infants likely requires novel adjuvants targeted specifically at the pediatric population to reach maximal vaccine efficacy with an acceptable safety profile. The current study supports the idea that additional adjuvants for pediatric vaccines should be, and need to be, tested in infants for their potential to enhance immune responses. Using an infant macaque model, our results suggest that both AS01 and 3M-052-SE can significantly improve and better sustain HIV Env-specific antibody responses than alum. Despite the limited number of animals, the results revealed interesting differences that warrant further testing of promising novel adjuvant candidates in larger preclinical and clinical studies to define the mechanisms leading to adjuvant-improved antibody responses and to identify targets for adjuvant and vaccine optimization.

Immunization with germ line-targeting SOSIP trimers elicits broadly neutralizing antibody precursors in infant macaques.

Adolescents are a growing population of people living with HIV. The period between weaning and sexual debut presents a low-risk window for HIV acquisition, making early childhood an ideal time for implementing an immunization regimen. Because the elicitation of broadly neutralizing antibodies (bnAbs) is critical for an effective HIV vaccine, our goal was to assess the ability of a bnAb B cell lineage-designed HIV envelope SOSIP (protein stabilized by a disulfide bond between gp120-gp41-named "SOS"-and an isoleucine-to-proline point mutation-named "IP"-at residue 559) to induce precursor CD4 binding site (CD4bs)-targeting bnAbs in early life. Infant rhesus macaques received either a BG505 SOSIP, based on the infant BG505 transmitted/founder virus, or the CD4bs germ line-targeting BG505 SOSIP GT1.1 (n = 5 per group). Although both strategies induced durable, high-magnitude plasma autologous virus neutralization responses, only GT1.1-immunized infants (n = 3 of 5) exhibited VRC01-like CD4bs bnAb precursor development. Thus, a multidose immunization regimen with bnAb lineage-designed SOSIPs shows promise for inducing early B cell responses with the potential to mature into protective HIV bnAbs before sexual debut.

Vaccination with a replication-defective cytomegalovirus vaccine elicits a glycoprotein B-specific monoclonal antibody repertoire distinct from natural infection.

Human Cytomegalovirus (HCMV) is the leading infectious congenital infection globally and the most common viral infection in transplant recipients, therefore identifying a vaccine for HCMV is a top priority. Humoral immunity is a correlate of protection for HCMV infection. The most effective vaccine tested to date, which achieved 50% reduction in acquisition of HCMV, was comprised of the glycoprotein B protein given with an oil-in-water emulsion adjuvant MF59. We characterize gB-specific monoclonal antibodies isolated from individuals vaccinated with a disabled infectious single cycle (DISC) CMV vaccine, V160, and compare these to the gB-specific monoclonal antibody repertoire isolated from naturally-infected individuals. We find that vaccination with V160 resulted in gB-specific antibodies that bound homogenously to gB expressed on the surface of a cell in contrast to antibodies isolated from natural infection which variably bound to cell-associated gB. Vaccination resulted in a similar breadth of gB-specific antibodies, with binding profile to gB genotypes 1-5 comparable to that of natural infection. Few gB-specific neutralizing antibodies were isolated from V160 vaccinees and fewer antibodies had identifiable gB antigenic domain specificity compared to that of naturally-infected individuals. We also show that glycosylation of gB residue N73 may shield binding of gB-specific antibodies.

Sutterella and its metabolic pathways positively correlate with vaccine-elicited antibody responses in infant rhesus macaques.

Introduction: It is becoming clearer that the microbiota helps drive responses to vaccines; however, little is known about the underlying mechanism. In this study, we aimed to identify microbial features that are associated with vaccine immunogenicity in infant rhesus macaques. Methods: We analyzed 16S rRNA gene sequencing data of 215 fecal samples collected at multiple timepoints from 64 nursery-reared infant macaques that received various HIV vaccine regimens. PERMANOVA tests were performed to determine factors affecting composition of the gut microbiota throughout the first eight months of life in these monkeys. We used DESeq2 to identify differentially abundant bacterial taxa, PICRUSt2 to impute metagenomic information, and mass spectrophotometry to determine levels of fecal short-chain fatty acids and bile acids. Results: Composition of the early-life gut microbial communities in nursery-reared rhesus macaques from the same animal care facility was driven by age, birth year, and vaccination status. We identified a Sutterella and a Rodentibacter species that positively correlated with vaccine-elicited antibody responses, with the Sutterella species exhibiting more robust findings. Analysis of Sutterella-related metagenomic data revealed five metabolic pathways that significantly correlated with improved antibody responses following HIV vaccination. Given these pathways have been associated with short-chain fatty acids and bile acids, we quantified the fecal concentration of these metabolites and found several that correlated with higher levels of HIV immunogen-elicited plasma IgG. Discussion: Our findings highlight an intricate bidirectional relationship between the microbiota and vaccines, where multiple aspects of the vaccination regimen modulate the microbiota and specific microbial features facilitate vaccine responses. An improved understanding of this microbiota-vaccine interplay will help develop more effective vaccines, particularly those that are tailored for early life.

Germline-targeting SOSIP trimer immunization elicits precursor CD4 binding-site targeting broadly neutralizing antibodies in infant macaques.

A vaccine that can achieve protective immunity prior to sexual debut is critical to prevent the estimated 410,000 new HIV infections that occur yearly in adolescents. As children living with HIV can make broadly neutralizing antibody (bnAb) responses in plasma at a faster rate than adults, early childhood is an opportune window for implementation of a multi-dose HIV immunization strategy to elicit protective immunity prior to adolescence. Therefore, the goal of our study was to assess the ability of a B cell lineage-designed HIV envelope SOSIP to induce bnAbs in early life. Infant rhesus macaques (RMs) received either BG505 SOSIP or the germline-targeting BG505 GT1.1 SOSIP (n=5/group) with the 3M-052-SE adjuvant at 0, 6, and 12 weeks of age. All infant RMs were then boosted with the BG505 SOSIP at weeks 26, 52 and 78, mimicking a pediatric immunization schedule of multiple vaccine boosts within the first two years of life. Both immunization strategies induced durable, high magnitude binding antibodies and plasma autologous virus neutralization that primarily targeted the CD4-binding site (CD4bs) or C3/465 epitope. Notably, three BG505 GT1.1-immunized infants exhibited a plasma HIV neutralization signature reflective of VRC01-like CD4bs bnAb precursor development and heterologous virus neutralization. Finally, infant RMs developed precursor bnAb responses at a similar frequency to that of adult RMs receiving a similar immunization strategy. Thus, a multi-dose immunization regimen with bnAb lineage designed SOSIPs is a promising strategy for inducing protective HIV bnAb responses in childhood prior to adolescence when sexual HIV exposure risk begins.

Vaccine-Induced, High-Magnitude HIV Env-Specific Antibodies with Fc-Mediated Effector Functions Are Insufficient to Protect Infant Rhesus Macaques against Oral SHIV Infection.

Improved access to antiretroviral therapy (ART) and antenatal care has significantly reduced in utero and peripartum mother-to-child human immunodeficiency virus (HIV) transmission. However, as breast milk transmission of HIV still occurs at an unacceptable rate, there remains a need to develop an effective vaccine for the pediatric population. Previously, we compared different HIV vaccine strategies, intervals, and adjuvants in infant rhesus macaques to optimize the induction of HIV envelope (Env)-specific antibodies with Fc-mediated effector function. In this study, we tested the efficacy of an optimized vaccine regimen against oral simian-human immunodeficiency virus (SHIV) acquisition in infant macaques. Twelve animals were immunized with 1086.c gp120 protein adjuvanted with 3M-052 in stable emulsion and modified vaccinia Ankara (MVA) virus expressing 1086.c HIV Env. Twelve control animals were immunized with empty MVA. The vaccine prime was given within 10 days of birth, with booster doses being administered at weeks 6 and 12. The vaccine regimen induced Env-specific plasma IgG antibodies capable of antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP). Beginning at week 15, infants were exposed orally to escalating doses of heterologous SHIV-1157(QNE)Y173H once a week until infected. Despite the induction of strong Fc-mediated antibody responses, the vaccine regimen did not reduce the risk of infection or time to acquisition compared to controls. However, among vaccinated animals, ADCC postvaccination and postinfection was associated with reduced peak viremia. Thus, nonneutralizing Env-specific antibodies with Fc effector function elicited by this vaccine regimen were insufficient for protection against heterologous oral SHIV infection shortly after the final immunization but may have contributed to control of viremia. IMPORTANCE Women of childbearing age are three times more likely to contract HIV infection than their male counterparts. Poor HIV testing rates coupled with low adherence to antiretroviral therapy (ART) result in a high risk of mother-to-infant HIV transmission, especially during the breastfeeding period. A preventative vaccine could curb pediatric HIV infections, reduce potential health sequalae, and prevent the need for lifelong ART in this population. The results of the current study imply that the HIV Env-specific IgG antibodies elicited by this candidate vaccine regimen, despite a high magnitude of Fc-mediated effector function but a lack of neutralizing antibodies and polyfunctional T cell responses, were insufficient to protect infant rhesus macaques against oral virus acquisition.

Leveraging antigenic seniority for maternal vaccination to prevent mother-to-child transmission of HIV-1.

The development of a maternal HIV vaccine to synergize with current antiretroviral drug prophylaxis can overcome implementation challenges and further reduce mother-to-child transmission (MTCT) of HIV. Both the epitope-specificity and autologous neutralization capacity of maternal HIV envelope (Env)-specific antibodies have been implicated in decreased risk of MTCT of HIV. Our goal was to determine if heterologous HIV Env immunization of SHIV.C.CH505-infected, ART-suppressed female rhesus macaques (RMs) could boost autologous Env-specific antibodies. SHIV.C.CH505-infected female RMs (n = 12), began a daily ART regimen at 12 weeks post-infection (wpi), which was continued for 12 weeks. Starting 2 weeks after ART initiation, RMs received 3 monthly immunizations with HIV b.63521/1086.C gp120 or placebo (n = 6/group) vaccine with adjuvant STR8S-C. Compared to the placebo-immunized animals, Env-vaccinated, SHIV-infected RMs exhibited enhanced IgG binding, avidity, and ADCC responses against the vaccine immunogens and the autologous SHIV.C.CH505 Env. Notably, the Env-specific memory B cells elicited by heterologous vaccination were dominated by cells that recognized the SHIV.C.CH505 Env, the antigen of primary exposure. Thus, vaccination of SHIV-infected, ART-suppressed RMs with heterologous HIV Envs can augment multiple components of the antibody response against the Env antigen of primary exposure, suggesting antigenic seniority. Our results suggest that a universal maternal HIV vaccination regimen can be developed to leverage antigenic seniority in targeting the maternal autologous virus pool.

Human immune globulin treatment controls Zika viremia in pregnant rhesus macaques.

There are currently no approved drugs to treat Zika virus (ZIKV) infection during pregnancy. Hyperimmune globulin products such as VARIZIG and WinRho are FDA-approved to treat conditions during pregnancy such as Varicella Zoster virus infection and Rh-incompatibility. We administered ZIKV-specific human immune globulin as a treatment in pregnant rhesus macaques one day after subcutaneous ZIKV infection. All animals controlled ZIKV viremia following the treatment and generated robust levels of anti-Zika virus antibodies in their blood. No adverse fetal or infant outcomes were identified in the treated animals, yet the placebo control treated animals also did not have signs related to congenital Zika syndrome (CZS). Human immune globulin may be a viable prophylaxis and treatment option for ZIKV infection during pregnancy, however, more studies are required to fully assess the impact of this treatment to prevent CZS.

Pre-existing immunity to cytomegalovirus in macaques influences human CMV vaccine responses in preclinical models.

Development of a human cytomegalovirus (HCMV) vaccine is a Tier 1 priority by the National Institutes of Medicine, as HCMV is the most common congenital infection globally and most frequent infectious complication in transplant patients. Relevant preclinical non-human primate models used for testing HCMV vaccine immunogenicity are rhesus and cynomolgous monkeys. However, a complication in using these models is that species-specific CMV variants are endemic in non-human primate breeding colonies. We hypothesize that natural immunity to species-specific CMV in rhesus and cynomolgous monkeys impacts HCMV vaccine immunogenicity and may interfere with our ability to fully interpret vaccine immunogenicity. A modified mRNA vaccine encoding HCMV glycoprotein (gB) and the pentameric complex (PC) packaged in lipid nanoparticles (LNP) was delivered intramuscularly to groups of cynomolgous (n = 16, CyCMV-seropositive) and rhesus macaques (n = 24, RhCMV-seropositive). High pre-vaccination IgG binding responses to HCMV gB were present in both species, but pre-vaccination binding responses to PC were mostly present in rhesus macaques. Yet, at least a log increase in both PC and gB-specific plasma IgG levels was detected post-second HCMV mRNA vaccination in both species. Both species responded with high epithelial cell neutralizing antibody responses at 4 weeks post second HCMV mRNA vaccination, but limited fibroblast neutralizing antibodies. HCMV gB + PC mRNA/LNP vaccine also elicited IgG binding responses to cell-associated gB, an identified immune correlate of protection, in both species after the second vaccination, and there was a moderately strong direct correlation between this pre- and post-vaccination response in rhesus macaques. Based on the correlation between pre-existing and post-vaccine gB-specific binding responses in rhesus macaques, we conclude that species-specific CMV variant-specific antibody responses contribute to antibody responses to HCMV vaccination in primate models, indicating that pre-existing immunity must be taken into account in non-human primate preclinical models and will impact immunogenicity of HCMV vaccines seropositive human vaccinees.

HIV envelope antigen valency on peptide nanofibers modulates antibody magnitude and binding breadth.

A major challenge in developing an effective vaccine against HIV-1 is the genetic diversity of its viral envelope. Because of the broad range of sequences exhibited by HIV-1 strains, protective antibodies must be able to bind and neutralize a widely mutated viral envelope protein. No vaccine has yet been designed which induces broadly neutralizing or protective immune responses against HIV in humans. Nanomaterial-based vaccines have shown the ability to generate antibody and cellular immune responses of increased breadth and neutralization potency. Thus, we have developed supramolecular nanofiber-based immunogens bearing the HIV gp120 envelope glycoprotein. These immunogens generated antibody responses that had increased magnitude and binding breadth compared to soluble gp120. By varying gp120 density on nanofibers, we determined that increased antigen valency was associated with increased antibody magnitude and germinal center responses. This study presents a proof-of-concept for a nanofiber vaccine platform generating broad, high binding antibody responses against the HIV-1 envelope glycoprotein.

SARS-CoV-2 Vaccines Elicit Durable Immune Responses in Infant Rhesus Macaques.

Early life SARS-CoV-2 vaccination has the potential to provide lifelong protection and achieve herd immunity. To evaluate SARS-CoV-2 infant vaccination, we immunized two groups of 8 infant rhesus macaques (RMs) at weeks 0 and 4 with stabilized prefusion SARS-CoV-2 S-2P spike (S) protein, either encoded by mRNA encapsulated in lipid nanoparticles (mRNA-LNP) or mixed with 3M-052-SE, a TLR7/8 agonist in a squalene emulsion (Protein+3M-052-SE). Neither vaccine induced adverse effects. High magnitude S-binding IgG and neutralizing infectious dose 50 (ID 50 ) >10 3 were elicited by both vaccines. S-specific T cell responses were dominated by IL-17, IFN- γ , or TNF- α . Antibody and cellular responses were stable through week 22. The S-2P mRNA-LNP and Protein-3M-052-SE vaccines are promising pediatric SARS-CoV-2 vaccine candidates to achieve durable protective immunity. ONE-SENTENCE SUMMARY: SARS-CoV-2 vaccines are well-tolerated and highly immunogenic in infant rhesus macaques.

SARS-CoV-2 vaccines elicit durable immune responses in infant rhesus macaques.

The inclusion of infants in the SARS-CoV-2 vaccine roll-out is important to prevent severe complications of pediatric SARS-CoV-2 infections and to limit transmission and could possibly be implemented via the global pediatric vaccine schedule. However, age-dependent differences in immune function require careful evaluation of novel vaccines in the pediatric population. Toward this goal, we assessed the safety and immunogenicity of two SARS-CoV-2 vaccines. Two groups of 8 infant rhesus macaques (RMs) were immunized intramuscularly at weeks 0 and 4 with stabilized prefusion SARS-CoV-2 S-2P spike (S) protein encoded by mRNA encapsulated in lipid nanoparticles (mRNA-LNP) or the purified S protein mixed with 3M-052, a synthetic TLR7/8 agonist in a squalene emulsion (Protein+3M-052-SE). Neither vaccine induced adverse effects. Both vaccines elicited high magnitude IgG binding to RBD, N terminus domain, S1, and S2, ACE2 blocking activity, and high neutralizing antibody titers, all peaking at week 6. S-specific memory B cells were detected by week 4 and S-specific T cell responses were dominated by the production of IL-17, IFN-γ, or TNF-α. Antibody and cellular responses were stable through week 22. The immune responses for the mRNA-LNP vaccine were of a similar magnitude to those elicited by the Moderna mRNA-1273 vaccine in adults. The S-2P mRNA-LNP and Protein-3M-052-SE vaccines were well-tolerated and highly immunogenic in infant RMs, providing proof-of concept for a pediatric SARS-CoV-2 vaccine with the potential for durable immunity that might decrease the transmission of SARS-CoV-2 and mitigate the ongoing health and socioeconomic impacts of COVID-19.

HIV Env-Specific IgG Antibodies Induced by Vaccination of Neonatal Rhesus Macaques Persist and Can Be Augmented by a Late Booster Immunization in Infancy.

The HIV epidemics in infants and adolescent women are linked. Young women of childbearing age are at high risk for HIV infection and, due to poor HIV testing rates and low adherence to antiretroviral therapy, are at high risk for mother-to-infant transmission. We hypothesize that HIV vaccine regimens initiated in early life would provide the necessary time frame to induce mature and highly functional Env-specific antibody responses that could potentially also protect against HIV acquisition later in life. The present study was designed to test two vaccine regimens, a clade C HIV Env protein vaccine (Env only) alone or combined with a modified vaccinia Ankara (MVA) vector expressing HIV Env (MVA/Env) for the induction and persistence of Env-specific antibody responses in an infant nonhuman primate model. Vaccination was initiated within the first week of life, with booster immunizations at weeks 6, 12, and 32. We demonstrate that both vaccine strategies were able to elicit durable Env-specific antibody responses that were enhanced by a late boost in infancy. Furthermore, we confirmed earlier data that intramuscular administration of the Env protein with the Toll-like receptor 7/8 (TLR7/8)-based adjuvant 3M-052 in stable emulsion (3M-052-SE) induced higher Env-specific antibody responses than vaccination with Env adjuvanted in Span85-Tween 80-squalene (STS) tested in a previous study. These results support the concept of early vaccination as a means to induce durable immune responses that may prevent HIV infection in adolescence at the onset of sexual debut.IMPORTANCE The majority of new HIV-1 infections occur in young adults, with adolescent women being 3 times more likely to acquire HIV than young men. Implementation of HIV prevention strategies has been less successful in this age group; thus, a vaccine given prior to adolescence remains a high priority. We propose that instead of starting HIV vaccination during adolescence, an HIV vaccine regimen initiated in early infancy, aligned with the well-accepted pediatric vaccine schedule and followed with booster immunizations, will provide an alternative means to reduce HIV acquisition in adolescence. Importantly, the long window of time between the first infant vaccine dose and the adolescence vaccine dose will allow for the maturation of highly functional HIV Env-specific antibody responses. Our study provides evidence that early life vaccination induces durable Env-specific plasma IgG responses that can be boosted to further improve the quality of the antibody response.

Quantitative definition of neurobehavior, vision, hearing and brain volumes in macaques congenitally exposed to Zika virus.

Congenital Zika virus (ZIKV) exposure results in a spectrum of disease ranging from severe birth defects to delayed onset neurodevelopmental deficits. ZIKV-related neuropathogenesis, predictors of birth defects, and neurodevelopmental deficits are not well defined in people. Here we assess the methodological and statistical feasibility of a congenital ZIKV exposure macaque model for identifying infant neurobehavior and brain abnormalities that may underlie neurodevelopmental deficits. We inoculated five pregnant macaques with ZIKV and mock-inoculated one macaque in the first trimester. Following birth, growth, ocular structure/function, brain structure, hearing, histopathology, and neurobehavior were quantitatively assessed during the first week of life. We identified the typical pregnancy outcomes of congenital ZIKV infection, with fetal demise and placental abnormalities. We estimated sample sizes needed to define differences between groups and demonstrated that future studies quantifying brain region volumes, retinal structure, hearing, and visual pathway function require a sample size of 14 animals per group (14 ZIKV, 14 control) to detect statistically significant differences in at least half of the infant exam parameters. Establishing the parameters for future studies of neurodevelopmental outcomes following congenital ZIKV exposure in macaques is essential for robust and rigorous experimental design.