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While the benefits of early antiretroviral therapy (ART) initiation in perinatally infected infants are well documented, early initiation is not always possible in postnatal pediatric HIV infections. The timing of ART initiation is likely to affect the size of the latent viral reservoir established, as well as the development of adaptive immune responses, such as the generation of neutralizing antibody responses against the virus. How these parameters impact the ability of infants to control viremia and the time to viral rebound after ART interruption is unclear and has never been modeled in infants. To investigate this question we used an infant nonhuman primate Simian/Human Immunodeficiency Virus (SHIV) infection model. Infant Rhesus macaques (RMs) were orally challenged with SHIV.C.CH505 375H dCT and either given ART at 4-7 days post-infection (early ART condition), at 2 weeks post-infection (intermediate ART condition), or at 8 weeks post-infection (late ART condition). These infants were then monitored for up to 60 months post-infection with serial viral load and immune measurements. To gain insight into early after analytic treatment interruption (ATI), we constructed mathematical models to investigate the effect of time of ART initiation in delaying viral rebound when treatment is interrupted, focusing on the relative contributions of latent reservoir size and autologous virus neutralizing antibody responses. We developed a stochastic mathematical model to investigate the joint effect of latent reservoir size, the autologous neutralizing antibody potency, and CD4+ T cell levels on the time to viral rebound for RMs rebounding up to 60 days post-ATI. We find that the latent reservoir size is an important determinant in explaining time to viral rebound in infant macaques by affecting the growth rate of the virus. The presence of neutralizing antibodies can also delay rebound, but we find this effect for high potency antibody responses only. Finally, we discuss the therapeutic implications of our findings.

Background: Cytomegalovirus (CMV) is the most common viral infection among lung transplant recipients and is associated with chronic lung allograft dysfunction. There is a need for better therapeutics as well as biomarkers to enable effective stratification of CMV seropositive patient risk for developing CMV DNAemia to inform prophylaxis duration. Methods: CMV-specific immunoglobulin G (IgG) binding and functional responses were evaluated in a discovery cohort of longitudinal plasma samples from 51 CMV seropositive human lung transplant recipients, collected as part of the clinical trials in organ transplantation (CTOT)-20 and CTOT-22 consortium studies. Pre-transplant plasma from an additional 43 CMV seropositive lung transplant recipients was evaluated as a validation cohort. Results: In the discovery cohort with longitudinal samples, pre-transplant plasma IgG binding to CMV surface glycoproteins glycoprotein H (gH)/glycoprotein L (gL), gH/gL/glycoprotein O (gO), and pentameric complex, as well as neutralization of CMV in epithelial cells, is associated with increased risk of CMV DNAemia post-prophylaxis. However, these results were not confirmed by the validation cohort. Conclusions: While quantification of pre-transplant CMV-specific antibody responses showed association with DNAemia in the discovery cohort, additional clinical variables and/or known risk factors for CMV, such as patient CMV-specific T-cell responses, may need to be considered in combination with humoral immunity to effectively stratify risk of CMV DNAemia.

Abstract Human cytomegalovirus (HCMV) remains the most common congenital infection and infectious complication in immunocompromised patients. The most successful HCMV vaccine to date, an HCMV glycoprotein B (gB) subunit vaccine adjuvanted with MF59, achieved 50% efficacy against primary HCMV infection. A previous study demonstrated that gB/MF59 vaccinees were less frequently infected with HCMV gB genotype strains most similar to the vaccine strain than strains encoding genetically distinct gB genotypes, suggesting strain-specific immunity accounted for the limited efficacy. To determine whether vaccination with multiple HCMV gB genotypes could increase the breadth of anti-HCMV gB humoral and cellular responses, we immunized 18 female rabbits with monovalent (gB-1), bivalent (gB-1+gB-3), or pentavalent (gB-1+gB-2+gB-3+gB-4+gB-5) gB lipid nanoparticle-encapsulated nucleoside-modified RNA (mRNA–LNP) vaccines. The multivalent vaccine groups did not demonstrate a higher magnitude or breadth of the IgG response to the gB ectodomain or cell-associated gB compared to that of the monovalent vaccine. Also, the multivalent vaccines did not show an increase in the breadth of neutralization activity and antibody-dependent cellular phagocytosis against HCMV strains encoding distinct gB genotypes. Interestingly, peripheral blood mononuclear cell-derived gB-2-specific T-cell responses elicited by multivalent vaccines were of a higher magnitude compared to that of monovalent vaccinated animals against a vaccine-mismatched gB genotype at peak immunogenicity. Yet, no statistical differences were observed in T cell response against gB-3 and gB-5 variable regions among the three vaccine groups. Our data suggests that the inclusion of multivalent gB antigens is not an effective strategy to increase the breadth of anti-HCMV gB antibody and T cell responses. Understanding how to increase the HCMV vaccine protection breadth will be essential to improve the vaccine efficacy.

Abstract An effective HIV-1 vaccine remains a critical unmet need for ending the AIDS epidemic. Vaccine trials conducted to date have suggested the need to increase the durability and functionality of vaccine-elicited antibodies to improve efficacy. We hypothesized that a conjugate vaccine based on the learned response to immunization with hepatitis B virus could be utilized to expand T cell help and improve antibody production against HIV-1. To test this, we developed an innovative conjugate vaccine regimen that used a modified vaccinia virus Ankara (MVA) co-expressing HIV-1 envelope (Env) and the hepatitis B virus surface antigen (HBsAg) as a prime, followed by two Env–HBsAg conjugate protein boosts. We compared the immunogenicity of this conjugate regimen to matched HIV-1 Env-only vaccines in two groups of 5 juvenile rhesus macaques previously immunized with hepatitis B vaccines in infancy. We found expansion of both HIV-1 and HBsAg-specific circulating T follicular helper cells and elevated serum levels of CXCL13, a marker for germinal center activity, after boosting with HBsAg–Env conjugate antigens in comparison to Env alone. The conjugate vaccine elicited higher levels of antibodies binding to select HIV Env antigens, but we did not observe significant improvement in antibody functionality, durability, maturation, or B cell clonal expansion. These data suggests that conjugate vaccination can engage both HIV-1 Env and HBsAg specific T cell help and modify antibody responses at early time points, but more research is needed to understand how to leverage this strategy to improve the durability and efficacy of next-generation HIV vaccines.

ABSTRACT Immunodominant and highly conserved flavivirus envelope proteins can trigger cross-reactive IgG antibodies against related flaviviruses, which shapes subsequent protection or disease severity. This study examined how prior dengue serotype 3 (DENV-3) infection affects subsequent Zika virus (ZIKV) plasmablast responses in rhesus macaques (n = 4). We found that prior DENV-3 infection was not associated with diminished ZIKV-neutralizing antibodies or magnitude of plasmablast activation. Rather, characterization of 363 plasmablasts and their derivative 177 monoclonal antibody supernatants from acute ZIKV infection revealed that prior DENV-3 infection was associated with a differential isotype distribution toward IgG, lower somatic hypermutation, and lesser B cell receptor variable gene diversity as compared with repeat ZIKV challenge. We did not find long-lasting DENV-3 cross-reactive IgG after a ZIKV infection but did find persistent ZIKV-binding cross-reactive IgG after a DENV-3 infection, suggesting non-reciprocal cross-reactive immunity. Infection with ZIKV after DENV-3 boosted pre-existing DENV-3-neutralizing antibodies by two- to threefold, demonstrating immune imprinting. These findings suggest that the order of DENV and ZIKV infections has impact on the quality of early B cell immunity which has implications for optimal immunization strategies.IMPORTANCEThe Zika virus epidemic of 2015–2016 in the Americas revealed that this mosquito-transmitted virus could be congenitally transmitted during pregnancy and cause birth defects in newborns. Currently, there are no interventions to mitigate this disease and Zika virus is likely to re-emerge. Understanding how protective antibody responses are generated against Zika virus can help in the development of a safe and effective vaccine. One main challenge is that Zika virus co-circulates with related viruses like dengue, such that prior exposure to one can generate cross-reactive antibodies against the other which may enhance infection and disease from the second virus. In this study, we sought to understand how prior dengue virus infection impacts subsequent immunity to Zika virus by single-cell sequencing of antibody producing cells in a second Zika virus infection. Identifying specific qualities of Zika virus immunity that are modulated by prior dengue virus immunity will enable optimal immunization strategies.

Abstract 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.

The leading cause of gastroenteritis in children under the age of five is rotavirus infection, accounting for 37% of diarrhoeal deaths in infants and young children globally. Oral rotavirus vaccines have been widely incorporated into national immunisation programs, but whilst these vaccines have excellent efficacy in high-income countries, they protect less than 50% of vaccinated individuals in low- and middle-income countries. In order to facilitate the development of improved vaccine strategies, a greater understanding of the immune response to existing vaccines is urgently needed. However, the use of mouse models to study immune responses to human rotavirus strains is currently limited as rotaviruses are highly species-specific and replication of human rotaviruses is minimal in mice. To enable characterisation of immune responses to human rotavirus in mice, we have generated chimeric viruses that combat the issue of rotavirus host range restriction. Using reverse genetics, the rotavirus outer capsid proteins (VP4 and VP7) from either human or murine rotavirus strains were encoded in a murine rotavirus backbone. Neonatal mice were infected with chimeric viruses and monitored daily for development of diarrhoea. Stool samples were collected to quantify viral shedding, and antibody responses were comprehensively evaluated. We demonstrated that chimeric rotaviruses were able to efficiently replicate in mice. Moreover, the chimeric rotavirus containing human rotavirus outer capsid proteins elicited a robust antibody response to human rotavirus antigens, whilst the control chimeric murine rotavirus did not. This chimeric human rotavirus therefore provides a new strategy for studying human-rotavirus-specific immunity to the outer capsid, and could be used to investigate factors causing variability in rotavirus vaccine efficacy. This small animal platform therefore has the potential to test the efficacy of new vaccines and antibody-based therapeutics.

The US biomedical research workforce suffers from systemic barriers causing insufficient diversity and perpetuating inequity. To inform programming enhancing graduate program access, we implemented a formative mixed-method study to identify needed supports for program applications and graduate program success. Overall, results indicate value in added supports for understanding application needs, network development, critical thinking, time management, and reading academic/scientific literature. We find selected differences for underrepresented minority (URM) students compared to others, including in the value of psychosocial supports. This work can inform broader efforts to enhance graduate school access and provides foundation for further understanding of URM students’ experiences.

IntroductionIt 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.MethodsWe 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.ResultsComposition 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.DiscussionOur 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.

Summary: Antibody-dependent cellular cytotoxicity (ADCC) is associated with protection against neonatal herpes. We hypothesized that placental transfer of ADCC-mediating herpes simplex virus (HSV) immunoglobulin G (IgG) is influenced by antigenic target, function, glycans, gestational age, and maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Maternal and cord blood were collected from HSV-seropositive (HSV+) mothers pre-COVID and HSV+/SARS-CoV-2+ mothers during the pandemic. Transfer of HSV neutralizing IgG was significantly lower in preterm versus term dyads (transfer ratio [TR] 0.84 vs. 2.44) whereas the TR of ADCC-mediating IgG was

Human cytomegalovirus (HCMV) is the most common vertically transmitted infection worldwide, yet there are no vaccines or therapeutics to prevent congenital HCMV (cCMV) infection. Emerging evidence indicates that antibody Fc effector functions may be a previously underappreciated component of maternal immunity against HCMV. We recently reported that antibody-dependent cellular phagocytosis (ADCP) and IgG activation of FcγRI/FcγRII were associated with protection against cCMV transmission, leading us to hypothesize that additional Fc-mediated antibody functions may be important. In this same cohort of HCMV-transmitting (n = 41) and nontransmitting (n = 40) mother-infant dyads, we report that higher maternal sera antibody–dependent cellular cytotoxicity (ADCC) activation is also associated with lower risk of cCMV transmission. We investigated the relationship between ADCC and IgG responses against 9 viral antigens and found that ADCC activation correlated most strongly with sera IgG binding to the HCMV immunoevasin protein UL16. Moreover, we determined that higher UL16-specific IgG binding and FcγRIII/CD16 engagement were associated with the greatest risk reduction in cCMV transmission. Our findings indicate that ADCC-activating antibodies against targets such as UL16 may represent an important protective maternal immune response against cCMV infection that can guide future HCMV correlates studies and vaccine or antibody-based therapeutic development.

Abstract 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.

Rhesus cytomegalovirus–based (RhCMV-based) vaccine vectors induce immune responses that protect ~60% of rhesus macaques (RMs) from SIVmac239 challenge. This efficacy depends on induction of effector memory–based (EM-biased) CD8+ T cells recognizing SIV peptides presented by major histocompatibility complex-E (MHC-E) instead of MHC-Ia. The phenotype, durability, and efficacy of RhCMV/SIV-elicited cellular immune responses were maintained when vector spread was severely reduced by deleting the antihost intrinsic immunity factor phosphoprotein 71 (pp71). Here, we examined the impact of an even more stringent attenuation strategy on vector-induced immune protection against SIV. Fusion of the FK506-binding protein (FKBP) degradation domain to Rh108, the orthologue of the essential human CMV (HCMV) late gene transcription factor UL79, generated RhCMV/SIV vectors that conditionally replicate only when the FK506 analog Shield-1 is present. Despite lacking in vivo dissemination and reduced innate and B cell responses to vaccination, Rh108-deficient 68-1 RhCMV/SIV vectors elicited high-frequency, durable, EM-biased, SIV-specific T cell responses in RhCMV-seropositive RMs at doses of ≥ 1 × 106 PFU. Strikingly, elicited CD8+ T cells exclusively targeted MHC-Ia–restricted epitopes and failed to protect against SIVmac239 challenge. Thus, Rh108-dependent late gene expression is required for both induction of MHC-E–restricted T cells and protection against SIV.

Summary Diacetyl (DA) is an α-diketone that is used to flavor microwave popcorn, coffee, and e-cigarettes. Occupational exposure to high levels of DA causes impaired lung function and obstructive airway disease. Additionally, lower levels of DA exposure dampen host defenses in vitro. Understanding DA’s impact on lung epithelium is important for delineating exposure risk on lung health. In this study, we assessed the impact of DA on normal human bronchial epithelial cell (NHBEC) morphology, transcriptional profiles, and susceptibility to SARS-CoV-2 infection. Transcriptomic analysis demonstrated cilia dysregulation, an increase in hypoxia and sterile inflammation associated pathways, and decreased expression of interferon-stimulated genes after DA exposure. Additionally, DA exposure resulted in cilia loss and increased hyaluronan production. After SARS-CoV-2 infection, both genomic and subgenomic SARS-CoV-2 RNA were increased in DA vapor- compared to vehicle-exposed NHBECs. This work suggests that transcriptomic and physiologic changes induced by DA vapor exposure damage cilia and increase host susceptibility to SARS-CoV-2.

Approximately 0.7% of infants are born with congenital cytomegalovirus (CMV), making it the most common congenital infection. About 1 in 5 congenitally infected babies will suffer long-term sequelae, including sensorineural deafness, intellectual disability, and epilepsy. CMV infection is highly species-dependent, and the rhesus CMV (RhCMV) infection of rhesus monkey fetuses is the only animal model that replicates essential features of congenital CMV (cCMV) infection in humans, including placental transmission, fetal disease, and fetal loss. Using experimental data from RhCMV seronegative rhesus macaques inoculated with RhCMV in the late first to early second trimesters of pregnancy, we built and calibrated a mathematical model for the placental transmission of CMV. The model was then used to study the effect of the timing of inoculation, maternal immune suppression, and hyper-immune globulin infusion on the risk of placental transmission in the context of primary and reactivated chronic maternal CMV infection.

Abstract Introduction Infant HIV prophylaxis with broadly neutralizing anti‐HIV antibodies (bNAbs) could provide long‐acting protection against vertical transmission. We sought to estimate the potential clinical impact and cost‐effectiveness of hypothetical bNAb prophylaxis programmes for children known to be HIV exposed at birth in three sub‐Saharan African settings. Methods We conducted a cost‐effectiveness analysis using the CEPAC‐Pediatric model, simulating cohorts of infants from birth through death in Côte d'Ivoire, South Africa and Zimbabwe. These settings were selected to reflect a broad range of HIV care cascade characteristics, antenatal HIV prevalence and budgetary constraints. We modelled strategies targeting bNAbs to only WHO‐designated “high‐risk” HIV‐exposed infants (HR‐HIVE) or to all HIV‐exposed infants (HIVE). We compared four prophylaxis approaches within each target population: standard of care oral antiretroviral prophylaxis (SOC), and SOC plus bNAbs at birth (1‐dose), at birth and 3 months (2‐doses), or every 3 months throughout breastfeeding (Extended). Base‐case model inputs included bNAb efficacy (60%/dose), effect duration (3 months/dose) and costs ($60/dose), based on published literature. Outcomes included paediatric HIV incidence and incremental cost‐effectiveness ratios (ICERs) calculated from discounted life expectancy and lifetime HIV‐related costs. Results The model projects that bNAbs would reduce absolute infant HIV incidence by 0.3–2.2% (9.6–34.9% relative reduction), varying by country, prophylaxis approach and target population. In all three settings, HR‐HIVE–1‐dose would be cost‐saving compared to SOC. Using a 50% GDP per capita ICER threshold, HIVE‐Extended would be cost‐effective in all three settings with ICERs of $497/YLS in Côte d'Ivoire, $464/YLS in South Africa and $455/YLS in Zimbabwe. In all three settings, bNAb strategies would remain cost‐effective at costs up to $200/dose if efficacy is ≥30%. If the bNAb effect duration were reduced to 1 month, the cost‐effective strategy would become HR‐HIVE–1‐dose in Côte d'Ivoire and Zimbabwe and HR‐HIVE–2‐doses in South Africa. Findings regarding the cost‐effectiveness of bNAb implementation strategies remained robust in sensitivity analyses regarding breastfeeding duration, maternal engagement in postpartum care, early infant diagnosis uptake and antiretroviral treatment costs. Conclusions At current efficacy and cost estimates, bNAb prophylaxis for HIV‐exposed children in sub‐Saharan African settings would be a cost‐effective intervention to reduce vertical HIV transmission.

Human cytomegalovirus (HCMV) is the most common congenital infection and a leading cause of stillbirth, neurodevelopmental impairment, and pediatric hearing loss worldwide. Development of a maternal vaccine or therapeutic to prevent congenital HCMV has been hindered by limited knowledge of the immune responses that protect against HCMV transmission in utero. To identify protective antibody responses, we measured HCMV-specific IgG binding and antiviral functions in paired maternal and cord blood sera from HCMV-seropositive transmitting (n = 41) and non-transmitting (n = 40) mother-infant dyads identified via a large, US-based, public cord blood bank. We found that high-avidity IgG binding to HCMV and antibody-dependent cellular phagocytosis (ADCP) were associated with reduced risk of congenital HCMV infection. We also determined that HCMV-specific IgG activation of FcγRI and FcγRII was enhanced in non-transmitting dyads and that increased ADCP responses were mediated through both FcγRI and FcγRIIA expressed on human monocytes. These findings suggest that engagement of FcγRI/FcγRIIA and Fc effector functions including ADCP may protect against congenital HCMV infection. Taken together, these data can guide future prospective studies on immune correlates against congenital HCMV transmission and inform HCMV vaccine and immunotherapeutic development.

Abstract 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.

Early initiation of antiretroviral therapy (ART) significantly improves clinical outcomes and reduces mortality of infants/children living with HIV. However, the ability of infected cells to establish latent viral reservoirs shortly after infection and to persist during long-term ART remains a major barrier to cure. In addition, while early ART treatment of infants living with HIV can limit the size of the virus reservoir, it can also blunt HIV-specific immune responses and does not mediate clearance of latently infected viral reservoirs. Thus, adjunctive immune-based therapies that are geared towards limiting the establishment of the virus reservoir and/or mediating the clearance of persistent reservoirs are of interest for their potential to achieve viral remission in the setting of pediatric HIV. Because of the differences between the early life and adult immune systems, these interventions may need to be tailored to the pediatric settings. Understanding the attributes and specificities of the early life immune milieu that are likely to impact the virus reservoir is important to guide the development of pediatric-specific immune-based interventions towards viral remission and cure. In this review, we compare the immune profiles of pediatric and adult HIV elite controllers, discuss the characteristics of cellular and anatomic HIV reservoirs in pediatric populations, and highlight the potential values of current cure strategies using immune-based therapies for long-term viral remission in the absence of ART in children living with HIV.

Pregnancy significantly elevates the risk of developing severe viral diseases, which can have a detrimental effect on fetal development and increases maternal mortality. In addition, certain viruses can be transmitted vertically from mother to babies, either in utero, during delivery, or postnatally during breastfeeding, resulting in congenital or neonatal diseases and associated sequelae. While neonates are highly susceptible to viral infections and severe disease outcomes, due to the immaturity of their developing immune system, virus-specific maternal antibodies transferred either trans-placentally or via breast milk provide protection to infants against intestinal, respiratory, or systemic infections, during the first months of life. Thus, maternal prenatal immunization is important not only to protect pregnant women from viral diseases, but also to prevent infection and/or improve disease outcomes for the fetuses and neonates via passively transferred antibodies. In this review, we discuss the protective role of maternal antibodies against three categories of viruses: (i) viruses that cause severe maternal disease outcomes with mainly indirect consequences to the fetus (e.g. SARS-CoV-2, influenza, DENV, filovirus), (ii) those that are vertically transmitted from mother to their infants and cause congenital diseases (e.g. HIV, ZIKV and CMV), and (iii) those that cause elevated disease severity among neonates and infants postnatally (e.g. RSV, Rotavirus, Norovirus, HSV and HBV). Furthermore, we review relevant pre-clinical animal models that can be employed to develop novel immunization strategies against these viruses to enhance protection of pregnant women and their babies.

A better understanding of the impact of early innate immune responses after vaccine priming on vaccine-elicited adaptive immune responses could inform rational design for effective HIV vaccines. The current study compared the whole blood molecular immune signatures of a 3M-052-SE adjuvanted HIV Env protein vaccine to a regimen combining the adjuvanted Env protein with simultaneous administration of a modified Vaccinia Ankara vector expressing HIV Env in infant rhesus macaques at days 0, 1, and 3 post vaccine prime. Both vaccines induced a rapid innate response, evident by elevated inflammatory plasma cytokines and altered gene expression. We identified 25 differentially-expressed genes (DEG) on day 1 compared to day 0 in the HIV protein vaccine group. In contrast, in the group that received both the Env protein and the MVA-Env vaccine only two DEG were identified, implying that the MVA-Env modified the innate response to the adjuvanted protein vaccine. By day 3, only three DEG maintained altered expression, indicative of the transient nature of the innate response. The DEG represented immune pathways associated with complement activation, type I interferon and interleukin signaling, pathogen sensing, and induction of adaptive immunity. DEG expression on day 1 was correlated to Env-specific antibody responses, in particular antibody-dependent cytotoxicity responses at week 34, and Env-specific follicular T helper cells. Results from network analysis supported the interaction of DEG and their proteins in B cell activation. These results emphasize that vaccine-induced HIV-specific antibody responses can be optimized through the modulation of the innate response to the vaccine prime.

ABSTRACT 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.

Understanding viral rebound in pediatric HIV-1 infection may inform the development of alternatives to lifelong antiretroviral therapy (ART) to achieve viral remission. We thus investigated viral rebound after analytical treatment interruption (ATI) in 10 infant macaques orally infected with SHIV.C.CH505 and treated with long-term ART. Rebound viremia was detected within 7 to 35 days of ATI in 9 of 10 animals, with posttreatment control of viremia seen in 5 of 5 Mamu-A*01+ macaques. Single-genome sequencing revealed that initial rebound virus was similar to viral DNA present in CD4+ T cells from blood, rectum, and lymph nodes before ATI. We assessed the earliest sites of viral reactivation immediately following ATI using ImmunoPET imaging. The largest increase in signal that preceded detectable viral RNA in plasma was found in the gastrointestinal (GI) tract, a site with relatively high SHIV RNA/DNA ratios in CD4+ T cells before ATI. Thus, the GI tract may be an initial source of rebound virus, but as ATI progresses, viral reactivation in other tissues likely contributes to the composition of plasma virus. Our study provides potentially novel insight into the features of viral rebound in pediatric infection and highlights the application of a noninvasive technique to monitor areas of HIV-1 expression in children.

Summary: Currently available SARS-CoV-2 therapeutics are targeted toward moderately to severely ill patients and require intravenous infusions, with limited options for exposed or infected patients with no or mild symptoms. Although vaccines have demonstrated protective efficacy, vaccine hesitancy and logistical distribution challenges will delay their ability to end the pandemic. Hence, there is a need for rapidly translatable, easy-to-administer-therapeutics that can prevent SARS-CoV-2 disease progression, when administered in the early stages of infection. We demonstrate that an orally bioavailable Hsp90 inhibitor, SNX-5422, currently in clinical trials as an anti-cancer therapeutic, inhibits SARS-CoV-2 replication in vitro at a high selectivity index. SNX-5422 treatment of human primary airway epithelial cells dampened expression of inflammatory pathways previously associated with poor SARS-CoV-2 disease outcomes. In addition, SNX-5422 interrupted expression of host factors demonstrated to be crucial for SARS-CoV-2 replication. Development of SNX-5422 as SARS-CoV-2-early-therapy will dampen disease severity, resulting in better clinical outcomes and reduced hospitalizations.

As SARS-CoV-2 continues to spread globally, questions have emerged regarding the strength and durability of immune responses in specific populations. In this study, we evaluated humoral immune responses in 69 children and adolescents with asymptomatic or mild symptomatic SARS-CoV-2 infection. We detected robust IgM, IgG, and IgA antibody responses to a broad array of SARS-CoV-2 antigens at the time of acute infection and 2 and 4 months after acute infection in all participants. Notably, these antibody responses were associated with virus-neutralizing activity that was still detectable 4 months after acute infection in 94% of children. Moreover, antibody responses and neutralizing activity in sera from children and adolescents were comparable or superior to those observed in sera from 24 adults with mild symptomatic infection. Taken together, these findings indicate that children and adolescents with mild or asymptomatic SARS-CoV-2 infection generate robust and durable humoral immune responses that can likely contribute to protection from reinfection.

A wide array of pathogens has the potential to injure the fetus and induce teratogenesis, the process by which mutations in fetal somatic cells lead to congenital malformations. Rubella virus was the first infectious disease to be linked to congenital malformations due to an infection in pregnancy, which can include congenital cataracts, microcephaly, hearing impairment and congenital heart disease. Currently, human cytomegalovirus (HCMV) is the leading infectious cause of congenital malformations globally, affecting 1 in every 200 infants. However, our knowledge of teratogenic viruses and pathogens is far from complete. New emerging infectious diseases may induce teratogenesis, similar to Zika virus (ZIKV) that caused a global pandemic in 2016–2017; thousands of neonates were born with congenital microcephaly due to ZIKV exposure in utero, which also included a spectrum of injuries to the brain, eyes and spinal cord. In addition to congenital anomalies, permanent injury to fetal and neonatal organs, preterm birth, stillbirth and spontaneous abortion are known consequences of a broader group of infectious diseases including group B streptococcus (GBS), Listeria monocytogenes, Influenza A virus (IAV), and Human Immunodeficiency Virus (HIV). Animal models are crucial for determining the mechanism of how these various infectious diseases induce teratogenesis or organ injury, as well as testing novel therapeutics for fetal or neonatal protection. Other mammalian models differ in many respects from human pregnancy including placentation, labor physiology, reproductive tract anatomy, timeline of fetal development and reproductive toxicology. In contrast, non-human primates (NHP) most closely resemble human pregnancy and exhibit key similarities that make them ideal for research to discover the mechanisms of injury and for testing vaccines and therapeutics to prevent teratogenesis, fetal and neonatal injury and adverse pregnancy outcomes (e.g., stillbirth or spontaneous abortion). In this review, we emphasize key contributions of the NHP model pre-clinical research for ZIKV, HCMV, HIV, IAV, L. monocytogenes, Ureaplasma species, and GBS. This work represents the foundation for development and testing of preventative and therapeutic strategies to inhibit infectious injury of human fetuses and neonates.

Abstract Introduction: Electronic health record (EHR) data have emerged as an important resource for population health and clinical research. There have been significant efforts to leverage EHR data for research; however, given data security concerns and the complexity of the data, EHR data are frequently difficult to access and use for clinical studies. We describe the development of a Clinical Research Datamart (CRDM) that was developed to provide well-curated and easily accessible EHR data to Duke University investigators. Methods: The CRDM was designed to (1) contain most of the patient-level data elements needed for research studies; (2) be directly accessible by individuals conducting statistical analyses (including Biostatistics, Epidemiology, and Research Design (BERD) core members); (3) be queried via a code-based system to promote reproducibility and consistency across studies; and (4) utilize a secure protected analytic workspace in which sensitive EHR data can be stored and analyzed. The CRDM utilizes data transformed for the PCORnet data network, and was augmented with additional data tables containing site-specific data elements to provide additional contextual information. Results: We provide descriptions of ideal use cases and discuss dissemination and evaluation methods, including future work to expand the user base and track the use and impact of this data resource. Conclusions: The CRDM utilizes resources developed as part of the Clinical and Translational Science Awards (CTSAs) program and could be replicated by other institutions with CTSAs.

Infants are capable of mounting adaptive immune responses, but their ability to develop long-lasting immunity is limited. Understanding the particularities of the neonatal adaptive immune system is therefore critical to guide the design of immune-based interventions, including vaccines, in early life. In this review, we present a thorough summary of T cell, B cell, and humoral immunity in early life and discuss infant adaptive immune responses to pathogens and vaccines. We focus on the differences between T and B cell responses in early life and adulthood, which hinder the generation of long-lasting adaptive immune responses in infancy. We discuss how knowledge of early life adaptive immunity can be applied when developing vaccine strategies for this unique period of immune development. In particular, we emphasize the use of novel vaccine adjuvants and optimization of infant vaccine schedules. We also propose integrating maternal and infant immunization strategies to ensure optimal neonatal protection through passive maternal antibody transfer while avoiding hindering infant vaccine responses. Our review highlights that the infant adaptive immune system is functionally distinct and uniquely regulated compared to later life and that these particularities should be considered when designing interventions to promote pediatric health.

Different HIV vaccine regimens elicit distinct plasma antibody responses in both human and nonhuman primate models. Previous studies in human and non-human primate infants showed that adjuvants influenced the quality of plasma antibody responses induced by pediatric HIV envelope vaccine regimens. We recently reported that use of the 3M052-SE adjuvant and longer intervals between vaccinations are associated with higher magnitude of antibody responses in infant rhesus macaques. However, the impact of different adjuvants in HIV vaccine regimens on the developing infant B cell receptor (BCR) repertoire has not been studied. This study evaluated whether pediatric HIV envelope vaccine regimens with different adjuvants induced distinct antigen-specific memory B cell repertoires and whether specific immunoglobulin (Ig) immunogenetic characteristics are associated with higher magnitude of plasma antibody responses in vaccinated infant rhesus macaques. We utilized archived preclinical pediatric HIV vaccine studies PBMCs and tissue samples from 19 infant rhesus macaques immunized either with (i) HIV Env protein with a squalene adjuvant, (ii) MVA-HIV and Env protein co-administered using a 3-week interval, (iii) MVA-HIV prime/ protein boost with an extended 6-week interval between immunizations, or (iv) with HIV Env administered with 3M-052-SE adjuvant. Frequencies of vaccine-elicited HIV Env-specific memory B cells from PBMCs and tissues were similar across vaccination groups (frequency range of 0.06–1.72%). There was no association between vaccine-elicited antigen-specific memory B cell frequencies and plasma antibody titer or avidity. Moreover, the epitope specificity and Ig immunogenetic features of vaccine-elicited monoclonal antibodies did not differ between the different vaccine regimens. These data suggest that pediatric HIV envelope vaccine candidates with different adjuvants that previously induced higher magnitude and quality of plasma antibody responses in infant rhesus macaques were not driven by distinct antigen-specific memory BCR repertoires.

Congenital and perinatal infections are transmitted from mother to infant during pregnancy across the placenta or during delivery. These infections not only cause pregnancy complications and still birth, but also result in an array of pediatric morbidities caused by physical deformities, neurodevelopmental delays, and impaired vision, mobility and hearing. Due to the burden of these conditions, congenital and perinatal infections may result in lifelong disability and profoundly impact an individual's ability to live to their fullest capacity. While there are vaccines to prevent congenital and perinatal rubella, varicella, and hepatitis B infections, many more are currently in development at various stages of progress. The spectrum of our efforts to understand and address these infections includes observational studies of natural history of disease, epidemiological evaluation of risk factors, immunogen design, preclinical research of protective immunity in animal models, and evaluation of promising candidates in vaccine trials. In this review we summarize this progress in vaccine development research for Cytomegalovirus, Group B Streptococcus, Herpes simplex virus, Human Immunodeficiency Virus, Toxoplasma, Syphilis, and Zika virus congenital and perinatal infections. We then synthesize this evidence to examine how close we are to developing a vaccine for these infections, and highlight areas where research is still needed.

ABSTRACT 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.

ABSTRACT Each year, >180,000 infants become infected via mother-to-child transmission (MTCT) of HIV despite the availability of effective maternal antiretroviral treatments, underlining the need for a maternal HIV vaccine. We characterized 224 maternal HIV envelope (Env)-specific IgG monoclonal antibodies (MAbs) from seven nontransmitting and transmitting HIV-infected U.S. and Malawian mothers and examined their neutralization activities against nontransmitted autologous circulating viruses and infant-transmitted founder (infant-T/F) viruses. Only a small subset of maternal viruses, 3 of 72 (4%), were weakly neutralized by maternal linear V3 epitope-specific IgG MAbs, whereas 6 out of 6 (100%) infant-T/F viruses were neutralization resistant to these V3-specific IgG MAbs. We also show that maternal-plasma broadly neutralizing antibody (bNAb) responses targeting the V3 glycan supersite in a transmitting woman may have selected for an N332 V3 glycan neutralization-resistant infant-T/F virus. These data have important implications for bNAb-eliciting vaccines and passively administered bNAbs in the setting of MTCT. IMPORTANCE Efforts to eliminate MTCT of HIV with antiretroviral therapy (ART) have met little success, with >180,000 infant infections each year worldwide. It is therefore likely that additional immunologic strategies that can synergize with ART will be required to eliminate MTCT of HIV. To this end, understanding the role of maternal HIV Env-specific IgG antibodies in the setting of MTCT is crucial. In this study, we found that maternal-plasma broadly neutralizing antibody (bNAb) responses can select for T/F viruses that initiate infection in infants. We propose that clinical trials testing the efficacy of single bNAb specificities should not include HIV-infected pregnant women, as a single bNAb might select for neutralization-resistant infant-T/F viruses.

Mother-to-child transmission of HIV-1 remains a major global health challenge. Currently, HIV-1-infected infants require strict lifelong adherence to antiretroviral therapy to prevent replication of virus from reservoirs of infected cells, and to halt progression of disease. There is a critical need for immune interventions that can be deployed shortly after infection to eliminate HIV-1-infected cells in order to promote long-term remission of viremia, or to potentially cure pediatric HIV-1-infection. Bispecific HIV × CD3 DART® molecules able to co-engage the HIV-1 envelope protein on the surface of infected cells and CD3 on cytolytic T cells have been previously shown to eliminate HIV-1 infected cells in vitro and are candidates for passive immunotherapy to reduce the virus reservoir. However, their potential utility as therapy for infant HIV-1 infection is unclear as the ability of these novel antibody-based molecules to work in concert with cells of the infant immune system had not been assessed. Here, we use human umbilical cord blood as a model of the naïve neonatal immune system to evaluate the ability of HIV x CD3 DART molecules to recruit and redirect neonatal effector cells for elimination of autologous CD4+ T cells infected with HIV-1 encoding an envelope gene sequenced from a mother-to-child transmission event. We found that HIV × CD3 DART molecules can redirect T cells present in cord blood for elimination of HIV-infected CD4+ T cells. However, we observed reduced killing by T cells isolated from cord blood when compared to cells isolated from adult peripheral blood—likely due to the absence of the memory and effector CD8+ T cells that are most cytolytic when redirected by bispecific DART molecules. We also found that newly developed HIV × CD16 DART molecules were able to recruit CD16-expressing natural killer cells from cord blood to eliminate HIV-infected cells, and the activity of cord blood natural killer cells could be substantially increased by priming with IL-15. Our results support continued development of HIV-specific DART molecules using relevant preclinical animal models to optimize strategies for effective use of this immune therapy to reduce HIV-1 infection in pediatric populations.

Summary: HIV-1-infected infants develop broadly neutralizing antibodies (bnAbs) more rapidly than adults, suggesting differences in the neonatal versus adult responses to the HIV-1 envelope (Env). Here, trimeric forms of HIV-1 Env immunogens elicit increased gp120- and gp41-specific antibodies more rapidly in neonatal macaques than adult macaques. Transcriptome analyses of neonatal versus adult immune cells after Env vaccination reveal that neonatal macaques have higher levels of the apoptosis regulator BCL2 in T cells and lower levels of the immunosuppressive interleukin-10 (IL-10) receptor alpha (IL10RA) mRNA transcripts in T cells, B cells, natural killer (NK) cells, and monocytes. In addition, immunized neonatal macaques exhibit increased frequencies of activated blood T follicular helper-like (Tfh) cells compared to adults. Thus, neonatal macaques have transcriptome signatures of decreased immunosuppression and apoptosis compared with adult macaques, providing an immune landscape conducive to early-life immunization prior to sexual debut. : Han et al. demonstrate that infant macaques are capable of responding to HIV vaccines currently studied in human clinical trials. The nature of the neonatal immune system following immunization also suggests a state permissive for generating HIV-1 antibodies. Thus, infant HIV-1 immunization remains a viable strategy to end this pandemic. Keywords: neonates, HIV-1 envelope, immunization, transcriptome, rhesus macaques, single-cell RNA sequencing

Abstract Background The initial envelope (Env)-specific antibody response in acutely HIV-1-infected individuals and simian immunodeficiency virus (SIV)-infected rhesus monkeys (RMs) is dominated by non-neutralizing antibodies targeting Env gp41. In contrast, natural primate SIV hosts, such as African green monkeys (AGMs), develop a predominant Env gp120-specific antibody response to SIV infection. However, the fine-epitope specificity and function of SIV Env-specific plasma IgG, and their potential role on autologous virus co-evolution in SIV-infected AGMs and RMs remain unclear. Results Unlike the dominant linear gp41-specific IgG responses in RMs, SIV-infected AGMs demonstrated a unique linear variable loop 2 (V2)-specific plasma IgG response that arose concurrently with high gp120-directed antibody-dependent cellular cytotoxicity (ADCC) activity, and SIVsab-infected cell binding responses during acute infection. Moreover, SIV variants isolated from SIV-infected AGMs exhibited high amino acid mutation frequencies within the Env V1V2 loop compared to those of RMs. Notably, the linear V2-specific IgG epitope in AGMs overlaps with an analogous region of the HIV V2 loop containing the K169 mutation epitope identified in breakthrough viruses from RV144 vaccinees. Conclusion Vaccine-elicited Env V2-specific IgG responses have been proposed as an immune correlate of reduced risk in HIV-1/SIV acquisition in humans and RMs. Yet the pathways to elicit these potentially-protective V2-specific IgG responses remain unclear. In this study, we demonstrate that SIV-infected AGMs, which are the natural hosts of SIV, exhibited high plasma linear V2-specific IgG binding responses that arose concurrently with SIV Env gp120-directed ADCC-mediating, and SIV-infected cell plasma IgG binding responses during acute SIV infection, which were not present in acutely SIV-infected RMs. The linear V2-specific antibody response in AGMs targets an overlapping epitope of the proposed site of vaccine-induced immune pressure defined in the moderately protective RV144 HIV-1 vaccine trial. Identifying host factors that control the early elicitation of Env V2-specific IgG and ADCC antibody responses in these natural SIV hosts could inform vaccination strategies aimed at rapidly inducing potentially-protective HIV-1 Env-specific responses in humans.

Human cytomegalovirus (HCMV), one of the most prevalent viruses across the globe, is a common cause of morbidity and mortality for immunocompromised individuals. Recent clinical observations have demonstrated that mixed strain infections are common and may lead to more severe disease progression. This clinical observation illustrates the complexity of the HCMV genome and emphasizes the importance of taking a population-level view of genotypic evolution. Here we review frequently sampled polymorphisms in the glycoproteins of HCMV, comparing the variable regions, and summarizing their corresponding geographic distributions observed to date. The related strain-specific immunity, including neutralization activity and antigen-specific cellular immunity, is also discussed. Given that these glycoproteins are common targets for vaccine design and anti-viral therapies, this observed genetic variation represents an important resource for future efforts to combat HCMV infections.

Abstract Background Threshold regression models are a diverse set of non-regular regression models that all depend on change points or thresholds. They provide a simple but elegant and interpretable way to model certain kinds of nonlinear relationships between the outcome and a predictor. Results The R package chngpt provides both estimation and hypothesis testing functionalities for four common variants of threshold regression models. All allow for adjustment of additional covariates not subjected to thresholding. We demonstrate the consistency of the estimating procedures and the type 1 error rates of the testing procedures by Monte Carlo studies, and illustrate their practical uses using an example from the study of immune response biomarkers in the context of Mother-To-Child-Transmission of HIV-1 viruses. Conclusion chngpt makes several unique contributions to the software for threshold regression models and will make these models more accessible to practitioners interested in modeling threshold effects.

ABSTRACT To design immune interventions that can synergize with antiretroviral therapy (ART) to reduce the rate of HIV mother-to-child transmission (MTCT), it is essential to characterize maternal immune responses in the setting of ART during pregnancy and breastfeeding and define their effect on MTCT. Prior studies reported an association between breast milk envelope (Env)-specific antibodies and antibody-dependent cell cytotoxicity (ADCC) activity with reduced postnatal transmission. In this study, we investigated whether these immune correlates were similarly associated with protection in a matched case-control study of mother-infant pairs receiving maternal ART or infant nevirapine prophylaxis during breastfeeding in the International Maternal-Pediatric-Adolescent AIDS Clinical Trials Network Promoting Maternal-Infant Survival Everywhere (PROMISE) trial, assessing postnatal transmission risk in 19 transmitting and 57 nontransmitting mothers using conditional logistic regression models adjusted for maternal plasma viral load. The odds ratios of postnatal MTCT for a 1-unit increase in an immune correlate were 3.61 (95% confidence interval [CI], 0.56, 23.14) for breast milk Env-specific secretory IgA (sIgA), 2.32 (95% CI, 0.43, 12.56) for breast milk and 2.16 (95% CI, 0.51, 9.14) for plasma Env-specific IgA, and 4.57 (95% CI, 0.68, 30.48) for breast milk and 0.96 (95% CI, 0.25, 3.67) for plasma ADCC activity, with all CIs spanning 1.0. Interestingly, although mucosal IgA responses are poor in untreated HIV-infected women, there was a strong correlation between the magnitudes of breast milk and plasma Env-specific IgA in this cohort. In this analysis of the small number of postnatal virus transmissions in the landmark PROMISE study, no single antibody response was associated with breast milk transmission risk. IMPORTANCE Each year, >150,000 infants become newly infected with HIV-1 through MTCT despite ART, with up to 42% of infections occurring during breastfeeding. Several factors contribute to continued pediatric infections, including ART nonadherence, the emergence of drug-resistant HIV strains, acute infection during breastfeeding, and poor access to ART in resource-limited areas. A better understanding of the maternal humoral immune responses that provide protection against postnatal transmission in the setting of ART is critical to guide the design of maternal vaccine strategies to further eliminate postnatal HIV transmission. In this study, we found that in women treated with antiretrovirals during pregnancy, there was a positive correlation between plasma viral load and breast milk and plasma IgA responses; however, conclusions regarding odds of MTCT risk were limited by the small sample size. These findings will inform future studies to investigate maternal immune interventions that can synergize with ART to eliminate MTCT during breastfeeding.

ABSTRACT To achieve long-term viral remission in human immunodeficiency virus (HIV)-infected children, novel strategies beyond early antiretroviral therapy (ART) will be necessary. Identifying clinical predictors of the time to viral rebound upon ART interruption will streamline the development of novel therapeutic strategies and accelerate their evaluation in clinical trials. However, identification of these biomarkers is logistically challenging in infants, due to sampling limitations and the potential risks of treatment interruption. To facilitate the identification of biomarkers predicting viral rebound, we have developed an infant rhesus macaque (RM) model of oral simian-human immunodeficiency virus (SHIV) SHIV.CH505.375H.dCT challenge and analytical treatment interruption (ATI) after short-term ART. We used this model to characterize SHIV replication kinetics and virus-specific immune responses during short-term ART or after ATI and demonstrated plasma viral rebound in 5 out of 6 (83%) infants. We observed a decline in humoral immune responses and partial dampening of systemic immune activation upon initiation of ART in these infants. Furthermore, we monitored SHIV replication and rebound kinetics in infant and adult RMs and found that both infants and adults demonstrated equally potent virus-specific humoral immune responses. Finally, we validated our models by confirming a well-established correlate of the time to viral rebound, namely, the pre-ART plasma viral load, as well as identified additional potential humoral immune correlates. Thus, this model of infant ART and viral rebound can be used and further optimized to define biomarkers of viral rebound following long-term ART as well as to preclinically assess novel therapies to achieve a pediatric HIV functional cure. IMPORTANCE Novel interventions that do not rely on daily adherence to ART are needed to achieve sustained viral remission for perinatally infected children, who currently rely on lifelong ART. Considering the risks and expense associated with ART interruption trials, the identification of biomarkers of viral rebound will prioritize promising therapeutic intervention strategies, including anti-HIV Env protein therapeutics. However, comprehensive studies to identify those biomarkers are logistically challenging in human infants, demanding the need for relevant nonhuman primate models of HIV rebound. In this study, we developed an infant RM model of oral infection with simian-human immunodeficiency virus expressing clade C HIV Env and short-term ART followed by ATI, longitudinally characterizing the immune responses to viral infection during ART and after ATI. Additionally, we compared this infant RM model to an analogous adult RM rebound model and identified virologic and immunologic correlates of the time to viral rebound after ATI.

Herpesvirus infections are a leading cause of neurodevelopmental delay in newborns and end-organ disease in immunocompromised patients. One leading strategy to reduce the disease burden of herpesvirus infections such as herpes simplex virus (HSV) and human cytomegalovirus (HCMV) is to prevent primary acquisition by vaccination, yet vaccine development remains hampered by limited understanding of immune correlates of protection against infection. Traditionally, vaccine development has aimed to increase antibody titers with neutralizing function, which involves the direct binding of antibodies to viral particles. However, recent research has explored the numerous other responses that can be mediated by engagement of the antibody constant region (Fc) with Fc receptors (FcR) present on immune cells or with complement molecules. These functions include antiviral responses such as antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). Uniquely, herpesviruses encode FcR that can act as distractor receptors for host antiviral IgG, thus enabling viral evasion of host defenses. This review focuses on the relative roles of neutralizing and non-neutralizing functions antibodies that target herpesvirus antigens for HSV and HCMV, as well as the roles of Fc-FcR interactions for both host defenses and viral escape.

Summary: Despite burgeoning evidence demonstrating the adaptive properties of natural killer (NK) cells, mechanistic data explaining these phenomena are lacking. Following antibody sensitization, NK cells lacking the Fc receptor (FcR) signaling chain (Δg) acquire adaptive features, including robust proliferation, multifunctionality, rapid killing, and mobilization to sites of virus exposure. Using the rhesus macaque model, we demonstrate the systemic distribution of Δg NK cells expressing memory features, including downregulated Helios and Eomes. Furthermore, we find that Δg NK cells abandon typical γ-chain/Syk in lieu of CD3ζ-Zap70 signaling. FCγRIIIa (CD16) density, mucosal homing, and function are all coupled to this alternate signaling, which in itself requires priming by rhesus cytomegalovirus (rhCMV). Simian immunodeficiency virus (SIV) infections further expand gut-homing adaptive NK cells but result in pathogenic suppression of CD3ζ-Zap70 signaling and function. Herein, we provide a mechanism of virus-dependent alternative signaling that may explain the acquisition of adaptive features by primate NK cells and could be targeted for future vaccine or curative therapies. : Gamma-chain-deficient adaptive NK cells are robust mediators of antiviral immunity via ADCC. Shah et al. demonstrate using macaque models that acquisition of these features requires previous priming with CMV infection and involves alternative signaling via CD3zeta but is actively suppressed by lentivirus infection. Keywords: natural killer cells, CMV, innate immunity, HIV, SIV

Infection of African green monkeys with simian immunodeficiency virus is a potential model for HIV vaccine development. Here, Zhang et al. catalogue the immunoglobulin loci present in the genome of these animals, and experimentally study their B-cell response to the viral envelope protein.

Animal models of infection with Zika virus (ZIKV) are urgently needed for a better understanding of pathogenesis and for testing potential therapies. Here, the authors describe infection of rhesus macaques with an Asian-lineage ZIKV strain as a relevant animal model for studying ZIKV pathogenesis.

ABSTRACT Mother-to-child transmission (MTCT) of human immunodeficiency virus type 1 (HIV-1) contributes to an estimated 150,000 new infections annually. Maternal vaccination has proven safe and effective at mitigating the impact of other neonatal pathogens and is one avenue toward generating the potentially protective immune responses necessary to inhibit HIV-1 infection of infants through breastfeeding. In the present study, we tested the efficacy of a maternal vaccine regimen consisting of a modified vaccinia virus Ankara (MVA) 1086.C gp120 prime-combined intramuscular-intranasal gp120 boost administered during pregnancy and postpartum to confer passive protection on infant rhesus macaques against weekly oral exposure to subtype C simian-human immunodeficiency virus 1157ipd3N4 (SHIV1157ipd3N4) starting 6 weeks after birth. Despite eliciting a robust systemic envelope (Env)-specific IgG response, as well as durable milk IgA responses, the maternal vaccine did not have a discernible impact on infant oral SHIV acquisition. This study revealed considerable variation in vaccine-elicited IgG placental transfer and a swift decline of both Env-specific antibodies (Abs) and functional Ab responses in the infants prior to the first challenge, illustrating the importance of pregnancy immunization timing to elicit optimal systemic Ab levels at birth. Interestingly, the strongest correlation to the number of challenges required to infect the infants was the percentage of activated CD4+ T cells in the infant peripheral blood at the time of the first challenge. These findings suggest that, in addition to maternal immunization, interventions that limit the activation of target cells that contribute to susceptibility to oral HIV-1 acquisition independently of vaccination may be required to reduce infant HIV-1 acquisition via breastfeeding. IMPORTANCE Without novel strategies to prevent mother-to-child HIV-1 transmission, more than 5% of HIV-1-exposed infants will continue to acquire HIV-1, most through breastfeeding. This study of rhesus macaque dam-and-infant pairs is the first preclinical study to investigate the protective role of transplacentally transferred HIV-1 vaccine-elicited antibodies and HIV-1 vaccine-elicited breast milk antibody responses in infant oral virus acquisition. It revealed highly variable placental transfer of potentially protective antibodies and emphasized the importance of pregnancy immunization timing to reach peak antibody levels prior to delivery. While there was no discernible impact of maternal immunization on late infant oral virus acquisition, we observed a strong correlation between the percentage of activated CD4+ T cells in infant peripheral blood and a reduced number of challenges to infection. This finding highlights an important consideration for future studies evaluating alternative strategies to further reduce the vertical HIV-1 transmission risk.

Despite the wide availability of antiretroviral therapy (ART) prophylaxis during pregnancy, >150,000 infants become infected through mother-to-child transmission (MTCT) of HIV worldwide. It is likely that additional intervention strategies, such as a maternal HIV vaccine, will be required to eliminate pediatric HIV infections. A deeper understanding of the fine specificity and function of maternal HIV envelope (Env)-specific responses that provide partial protection against MTCT will be critical to inform the design of immunologic strategies to curb the pediatric HIV epidemic. Recent studies have underlined a role of maternal HIV Env-specific neutralizing and non-neutralizing responses in reducing risk of MTCT of HIV and in prolonging survival rates in HIV-infected infants. However, critical gaps in our knowledge include (A) the specific role of maternal autologous-virus IgG-neutralizing responses in driving the selection of infant transmitted founder (T/F) viruses and (B) Env mechanisms of escape from maternal autologous virus-neutralizing antibodies (NAbs). A more refined understanding of the fine specificities of maternal autologous virus NAbs and ways that maternal circulating viruses escape from these antibodies will be crucial to inform maternal vaccination strategies that can block MTCT to help achieve an HIV-free generation.

Congenital cytomegalovirus (cCMV) is the leading non-genetic cause of sensorineural hearing loss (SNHL), and efforts are geared towards prevention through vaccine development. Transmission rates following primary maternal infection occur at rates of 30−40%, however reported placental rates upon non-primary maternal infection is reported to be less than 80%) areas or in developing regions that examined a cohort of at least 50 infants for congenital CMV acquisition. We identified 19 articles that met criteria and were further categorized based on pre-conception serology, maternal seroprevalence, or previously known seroprevalence. Birth prevalence rates ranged from 0.4% to 6% (median 1.1%), with the studies reporting on clinical outcome (16/19 studies) noting the majority of infected infants as asymptomatic. We also utilized a recent study that differentiated primary maternal infections from chronic infections in a highly seropositive population to calculate a placental transmission rate in women with pre-existing immunity compared to that of no pre-existing immunity. This work confirms a low cCMV birth prevalence in highly seropositive populations, indicates via a calculated placental transmission rate that the CMV placental transmission rate is lower in non-primary infection than that of primary infection, and reveals gaps in data for further research aiming to identify targets for vaccine development.

HIV-1 and CMV are important pathogens transmitted via breastfeeding. Furthermore, perinatal CMV transmission may impact growth and disease progression in HIV-exposed infants. Although maternal antiretroviral therapy reduces milk HIV-1 RNA load and postnatal transmission, its impact on milk CMV load is unclear. We examined the relationship between milk CMV and HIV-1 load (4–6 weeks postpartum) and the impact of antiretroviral treatment in 69 HIV-infected, lactating Malawian women and assessed the relationship between milk CMV load and postnatal growth in HIV-exposed, breastfed infants through six months of age. Despite an association between milk HIV-1 RNA and CMV DNA load (0.39 log10 rise CMV load per log10 rise HIV-1 RNA load, 95% CI 0.13–0.66), milk CMV load was similar in antiretroviral-treated and untreated women. Higher milk CMV load was associated with lower length-for-age (−0.53, 95% CI: −0.96, −0.10) and weight-for-age (−0.40, 95% CI: −0.67, −0.13) Z-score at six months in exposed, uninfected infants. As the impact of maternal antiretroviral therapy on the magnitude of postnatal CMV exposure may be limited, our findings of an inverse relationship between infant growth and milk CMV load highlight the importance of defining the role of perinatal CMV exposure on growth faltering of HIV-exposed infants.