CMV Primes Functional Alternative Signaling in Adaptive Δg NK Cells but Is Subverted by Lentivirus Infection in Rhesus Macaques

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, multi-functionality, 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.

2772. HCMV gB Ectodomain Subunit and gB mRNA Vaccines Reduce AD-3 Immunodominance and Elicit More Durable Antibody Responses Than gB/MF59 Immunization

Background

A vaccine to prevent maternal acquisition of human cytomegalovirus (HCMV) during pregnancy is one potential strategy to reduce the incidence of congenital disease. The MF59-adjuvanted glycoprotein B (gB/MF59) protein subunit vaccine is the most efficacious tested to-date, though achieved only 50% efficacy in phase 2 trial. We previously identified that gB/MF59 vaccination elicited poor heterologous virus neutralization and an immunodominant response against non-neutralizing/cytosolic antigenic domain 3 (AD-3) (Figure 1). Thus, we sought novel gB vaccination strategies to improve functional antibody responses and reduce AD-3 immunodominance.

Methods

Groups of juvenile New Zealand White rabbits (n = 6) were administered 3 sequential doses of gB protein with an MF59-like squalene adjuvant IM, gB ectodomain protein (lacking AD-3) + squalene adjuvant IM, or lipid nanoparticle (LNP)-packaged nucleoside-modified mRNA encoding gB ID.

Results

The AD-3 immunodominant IgG response seen in human vaccinees was closely mimicked in rabbits, with 78% of binding antibodies directed against this region in the gB protein group compared with 1% and 46% in the ectodomain and mRNA-LNP-vaccinated groups respectively (Figure 2). All vaccines were highly immunogenic with similar kinetics and comparable peak gB-binding/functional antibody responses. However, both ectodomain and mRNA-LNP-immunized rabbits exhibited enhanced durability of IgG binding to gB protein (P = 0.04 and 0.02, respectively), and the mRNA-LNP group had more durable binding of cell membrane-associated gB (P < 0.001) (Figure 3). Additionally, ectodomain and mRNA-LNP-vaccinated rabbits had increased durability of antibodies targeting neutralizing epitopes AD-4 and AD-5 (P < 0.01). Finally, low-magnitude gB-specific T-cell activity was observed in the gB protein and mRNA-LNP groups, though not in ectodomain-vaccinated rabbits.

Conclusion

Altogether these data suggest that gB ectodomain subunit and gB mRNA-LNP vaccine formulations reduced targeting of non-neutralizing epitope AD-3 and elicited more durable IgG responses than gB protein vaccination. These next-generation HCMV vaccine candidates aiming to improve upon the partial efficacy of gB/MF59 vaccination should be further evaluated in preclinical models.

Disclosures

All authors: No reported disclosures.

2651. Protection Against Human Cytomegalovirus Acquisition Is Associated with IgG Binding to Cell-Associated CMV glycoprotein B in Two Historical gB/MF59 Vaccine Cohorts

Background

Human cytomegalovirus (CMV) is the most common congenital infection worldwide. A CMV glycoprotein B (gB) subunit vaccine with MF59 adjuvant achieved ~50% protection in phase II clinical trials in postpartum and adolescent women. Interestingly, postpartum vaccinees showed poor virus neutralization but robust antibody-dependent cellular phagocytosis (ADCP). In this study, we performed a combined humoral immune correlate of risk analysis in vaccinees to define vaccine-elicited immune responses associated with protection and targets for vaccine candidate immunogenicity.

Methods

gB/MF59 vaccinees who became infected and those who remained uninfected were 2:1 matched on race and number of vaccine doses. This study included 42 women from the adolescent (14 infected, 28 uninfected) and 33 from the postpartum cohorts (11 infected, 22 uninfected). IgG binding to whole gB, gB-neutralizing epitopes, FCRs, and whole virions were assessed by standard or multiplex ELISA. IgG binding to gB mRNA-transfected HEK293Ts was measured by flow cytometry. Neutralization of Towne, TB40/E, and AD169-repaired-GFP strains were measured in MRC-5, BJ5Ta, and/or ARPE-19 cells. Phagocytosis was assessed by THP-1 uptake of fluorescently conjugated TB40/E and AD169-repaired-GFP virions. Multiple linear regression controlling for cohort was performed for the combined log-transformed group data (apriori significance cut-off of P < 0.05, Benjamin–Hochberg FDR < 0.2).

Results

Vaccine-elicited antibodies in adolescent and postpartum cohorts exhibited similar magnitude IgG binding to soluble HCMV gB protein, gB-neutralizing domains, and gB-transfected cells. Autologous Towne strain neutralization was observed in both cohorts, but heterologous strain neutralization was observed only in adolescent vaccinees (P = 0.001). Both cohorts exhibited robust phagocytosis of HCMV virions. Regression analyses revealed that risk of HCMV acquisition in vaccinees was associated with magnitude IgG binding to gB-transfected cells (P = 0.006, FDR = 0.15), not neutralization or phagocytosis responses.

Conclusion

Protection against primary HCMV infection was significantly associated with vaccine-elicited IgG binding to gB-transfected cells, suggesting the importance of a native, cell-associated gB conformation in future vaccine candidates.

Disclosures

All authors: No reported disclosures.

Impact of Maternal Immunity on Congenital Cytomegalovirus Birth Prevalence and Infant Outcomes: A Systematic Review

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 <4%. There is significant debate about whether this reduction in transmission rate is due to pre-existing maternal immunity, which could identify possible immunologic targets for vaccines. To address this question, we performed a systemic review of the literature using Preferred Reporting Items for Systematic Review and Analysis (PRISMA) guidelines. We identified cohort studies in high CMV seroprevalent (>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.

The Roles of Host and Viral Antibody Fc Receptors in Herpes Simplex Virus (HSV) and Human Cytomegalovirus (HCMV) Infections and Immunity

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.

Analytical Treatment Interruption after Short-Term Antiretroviral Therapy in a Postnatally Simian-Human Immunodeficiency Virus-Infected Infant Rhesus Macaque Model

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.

Postnatal Zika virus infection of nonhuman primate infants born to mothers infected with homologous Brazilian Zika virus

Recent data in a nonhuman primate model showed that infants postnatally infected with Zika virus (ZIKV) were acutely susceptible to high viremia and neurological damage, suggesting the window of vulnerability extends beyond gestation. In this pilot study, we addressed the susceptibility of two infant rhesus macaques born healthy to dams infected with Zika virus during pregnancy. Passively acquired neutralizing antibody titers dropped below detection limits between 2 and 3 months of age, while binding antibodies remained detectable until viral infection at 5 months. Acute serum viremia was comparatively lower than adults infected with the same Brazilian isolate of ZIKV (n = 11 pregnant females, 4 males, and 4 non-pregnant females). Virus was never detected in cerebrospinal fluid nor in neural tissues at necropsy two weeks after infection. However, viral RNA was detected in lymph nodes, confirming some tissue dissemination. Though protection was not absolute and our study lacks an important comparison with postnatally infected infants born to naïve dams, our data suggest infants born healthy to infected mothers may harbor a modest but important level of protection from postnatally acquired ZIKV for several months after birth, an encouraging result given the potentially severe infection outcomes of this population.

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.

Cultivating Research Skills During Clinical Training to Promote Pediatric-Scientist Development

Physician-scientists represent a critical component of the biomedical and health research workforce. However, the proportion of physicians who spend a significant amount of effort on scientific research has declined over the past 40 years. This trend has been particularly noticeable in pediatrics despite recent scientific work revealing that early life influences, exposures, and health status play a significant role in lifelong health and disease. To address this problem, the Duke University Department of Pediatrics developed the Duke Pediatric Research Scholars Program for Physician-Scientist Development (DPRS). The DPRS is focused on research training during pediatric residency and fellowship. We aim to provide sufficient research exposure and support to help scholars develop a research niche and scholarly products as well as identify the career pathways that will enable them to achieve their research goals. Herein, we describe the DPRS's organizational structure, core components, recruitment strategies, and initial results, and we discuss implementation challenges and solutions. Additionally, we detail the program's integration with the department's residency and fellowship training programs (with particular reference to the challenges of integrating research into small- to medium-sized residency programs) and describe the development and integration of related initiatives across Duke University School of Medicine. The program served as the basis for 2 successful National Institutes of Health Stimulating Access to Research in Residency (R38) applications, and we hope it will serve as a model to integrate formalized research training for residents and fellows who wish to pursue research careers in academic medicine.

Primary infection with dengue or Zika virus does not affect the severity of heterologous secondary infection in macaques

Zika virus (ZIKV) and dengue virus (DENV) are genetically and antigenically related flaviviruses that now co-circulate in much of the tropical and subtropical world. The rapid emergence of ZIKV in the Americas in 2015 and 2016, and its recent associations with Guillain-Barré syndrome, birth defects, and fetal loss have led to the hypothesis that DENV infection induces cross-reactive antibodies that influence the severity of secondary ZIKV infections. It has also been proposed that pre-existing ZIKV immunity could affect DENV pathogenesis. We examined outcomes of secondary ZIKV infections in three rhesus and fifteen cynomolgus macaques, as well as secondary DENV-2 infections in three additional rhesus macaques up to a year post-primary ZIKV infection. Although cross-binding antibodies were detected prior to secondary infection for all animals and cross-neutralizing antibodies were detected for some animals, previous DENV or ZIKV infection had no apparent effect on the clinical course of heterotypic secondary infections in these animals. All animals had asymptomatic infections and, when compared to controls, did not have significantly perturbed hematological parameters. Rhesus macaques infected with DENV-2 approximately one year after primary ZIKV infection had higher vRNA loads in plasma when compared with serum vRNA loads from ZIKV-naive animals infected with DENV-2, but a differential effect of sample type could not be ruled out. In cynomolgus macaques, the serotype of primary DENV infection did not affect the outcome of secondary ZIKV infection.

Pre-existing immunity to one of the four DENV serotypes is known to increase the risk of severe disease upon secondary infection with a different serotype. Due to the antigenic similarities between ZIKV and DENV, it has been proposed that these viruses could interact in a similar fashion. Data from in vitro experiments and murine models suggests that pre-existing immunity to one virus could either enhance or protect against infection with the other. These somewhat contradictory findings highlight the need for immune competent animal models for understanding the role of cross-reactive antibodies in flavivirus pathogenesis. We examined secondary ZIKV or DENV infections in rhesus and cynomolgus macaques that had previously been infected with the other virus. We assessed the outcomes of secondary ZIKV or DENV infections by quantifying vRNA loads, clinical and laboratory parameters, body temperature, and weight for each cohort of animals and compared them with control animals. These comparisons demonstrated that within a year of primary infection, secondary infections with either ZIKV or DENV were similar to primary infections and were not associated with enhancement or reduction in severity of disease based on the outcomes that we assessed.

Determinants of Tenascin-C and HIV-1 envelope binding and neutralization

Interactions between innate antiviral factors at mucosal surfaces and HIV-1 virions contribute to the natural inefficiency of HIV-1 transmission and are a platform to inform the development of vaccine and nonvaccine strategies to block mucosal HIV-1 transmission. Tenascin-C (TNC) is a large, hexameric extracellular matrix glycoprotein identified in breast milk and genital fluids that broadly neutralizes HIV-1 via interaction with the HIV-1 Envelope (Env) variable 3 (V3) loop. In this report, we characterize the specific determinants of the interaction between TNC and the HIV-1 Env. We observed that TNC binding and neutralization of HIV-1 is dependent on the TNC fibrinogen-like globe (fbg) and fibronectin-type III (fn) domains, oligomerization, and its newly-mapped glycan structure. Moreover, we observed that TNC-mediated neutralization is also dependent on Env V3 residues 321/322 and 326/327, which surround the IGDIR motif of the V3 loop, as well the N332 glycan, which is critical to the broadly neutralizing activity of glycan-dependent V3-specific antibodies such as PGT128. Our results demonstrate a striking parallel between innate and adaptive immune mechanisms of broad HIV neutralization and provide further insight into the host protein-virus interactions responsible for the natural inefficiency of mucosal HIV-1 transmission.

Fc Characteristics Mediate Selective Placental Transfer of IgG in HIV-Infected Women

The placental transfer of maternal IgG is critical for infant protection against infectious pathogens. However, factors that modulate the placental transfer of IgG remain largely undefined. HIV-infected women have impaired placental IgG transfer, presenting a unique "disruption model" to define factors that modulate placental IgG transfer. We measured the placental transfer efficiency of maternal HIV and pathogen-specific IgG in US and Malawian HIV-infected mothers and their HIV-exposed uninfected and infected infants. We examined the role of maternal HIV disease progression, infant factors, placental Fc receptor expression, IgG subclass, and glycan signatures and their association with placental IgG transfer efficiency. Maternal IgG characteristics, such as binding to placentally expressed Fc receptors FcγRIIa and FcγRIIIa, and Fc region glycan profiles were associated with placental IgG transfer efficiency. Our findings suggest that Fc region characteristics modulate the selective placental transfer of IgG, with implications for maternal vaccine design and infant health.

Pediatric HIV-1 Acquisition and Lifelong Consequences of Infant Infection

Increased availability of antiretroviral therapy to pregnant and breastfeeding women in resource-limited areas has proven remarkably successful at reducing HIV vertical transmission rates over the past several decades. Yet, still more than 170,000 children are infected annually due to failures in therapy implementation, monitoring, and adherence. Mother-to-child transmission (MTCT) of HIV-1 can occur at one of several distinct stages of infant development - intrauterine, intrapartum, and postpartum. The heterogeneity of the maternal-fetal interface at each of these modes of transmission poses a challenge for the implementation of immune interventions to prevent all modes of HIV MTCT. However, using mother-infant human cohorts and nonhuman primate models of infant simian immunodeficiency virus (SIV) acquisition, investigators have made important observation about the biology of pediatric HIV infection and have identified unique protective immune factors for each mode of transmission. Knowledge of immune factors protective against HIV MTCT will be critical to the development of targeted immune therapies to prevent infant HIV acquisition and to bring an end to the pediatric AIDS epidemic.

Recent progress in immune-based interventions to prevent HIV-1 transmission to children

Globally, 150,000 new paediatric human immunodeficiency virus type 1 (HIV‐1) infections occurred in 2015. There remain complex challenges to the global elimination of paediatric HIV‐1 infection. Thus, for the global community to achieve elimination of new paediatric HIV‐1 infections, innovative approaches need to be explored. Immune‐based approaches to prevention of mother‐to‐child transmission (MTCT) may help fill some of the remaining gaps and provide new opportunities to achieve an AIDS‐free generation. Immune‐based interventions to prevent MTCT of HIV‐1 may include paediatric HIV vaccines and passive immunization approaches. Recent discoveries providing evidence of robust immune responses to HIV in infants open new and exciting prospects for paediatric HIV vaccines. Moreover, successful vaccination of infants has a different set of requirements than vaccination of adults and may be easier to achieve. Proof‐of‐concept has been established over the last two decades that passively administered HIV‐1 Env‐specific monoclonal antibody (mAbs) can prevent chimeric simian human immunodeficiency virus (SHIV) transmission to newborn nonhuman primates. There has been tremendous progress in isolating and characterizing broadly neutralizing antibodies to HIV, and clinical testing of these antibodies for treatment and prevention in both infants and adults is a major effort in the field. Immune‐based interventions need to be actively explored as they can provide critically important tools to address persistent challenges in MTCT prevention. It is a pivotal time for the field with active discussions on the best strategy to further reduce HIV infection of infants and accomplish the World Health Organization Fast‐Track 2030 goals to eliminate new paediatric HIV infections.

Geographic and Racial Disparities in Infant Hearing Loss

OBJECTIVE

Approximately 1 to 2 of every 1000 American newborns has hearing loss identified by newborn screening. This study was designed to determine if infant hearing loss is more common in socioeconomically disadvantaged communities.

STUDY DESIGN

In this retrospective study, we analyzed electronic medical record data using geostatistical models.

SETTING

Infants were residents of Durham County, North Carolina, born in 2 hospitals of the Duke University Health System. This county includes the city of Durham and surrounding suburban and rural communities.

SUBJECTS AND METHODS

Subjects were hearing-screened newborns, born between 2005 and 2016, whose residential address was in Durham County, North Carolina. This was a retrospective study using medical record data. We used Bayesian regression models with smoothing of coordinate date to identify both spatial and nonspatial predictors of infant hearing loss.

RESULTS

We identified 19,348 infants from Durham County, of whom 675 had failed initial hearing screening and 191 had hearing loss confirmed on follow-up. Hearing loss was significantly associated with minority race (odds ratio [OR], 2.45; 95% confidence interval, 1.97-3.06), as well as lower gestational age and maternal sexually transmitted infections. We identified significant geographic heterogeneity, with a higher probability of hearing loss in poorer urban neighborhoods (local OR range, 0.59-1.39). Neighborhood disadvantage was a significant predictor of hearing loss, as was high local seroprevalence of cytomegalovirus (CMV) among pregnant women.

CONCLUSIONS

Urban, low-income neighborhoods have a high prevalence of infant hearing loss compared with more affluent surrounding communities, particularly among minorities. This distribution may be attributable to congenital CMV infection.

Natural history of postnatal rhesus cytomegalovirus shedding by dams and acquisition by infant rhesus monkeys

BACKGROUND

Human infants frequently acquire human cytomegalovirus (HCMV) through breastfeeding, resulting in persistent high-level viral shedding in saliva and urine and infectivity to others, including pregnant women. Thus, vaccination to interrupt postnatal HCMV transmission is an attractive strategy to prevent HCMV spread and congenital infection. Rhesus CMV (RhCMV) in nonhuman primates is a valuable model for the study of immune strategies to prevent CMV transmission. Although rhesus monkeys typically acquire RhCMV before 1 year of age, the timing and mode of natural infant RhCMV transmission remain unknown.

METHODS

We followed 5 RhCMV-seropositive dams and their infants from birth until weaning, approximately 6 months later. RhCMV DNA levels in plasma, breast milk, saliva, and urine were measured every 2 weeks by quantitative PCR. RhCMV-specific T cell responses in peripheral blood and breast milk were measured by interferon gamma ELISpot assays. Serum IgG antibody levels were measured by ELISA.

RESULTS

Four of five postpartum RhCMV-seropositive mothers had intermittent, low-level RhCMV shedding in breast milk, whereas all had high-magnitude RhCMV shedding in saliva and urine. The kinetics of maternal blood RhCMV-specific T cell responses and viral shedding in urine and saliva did not strongly associate, though dams with consistently high systemic RhCMV-specific T cell responses tended to have undetectable RhCMV shedding in breast milk. All RhCMV-exposed infants had intermittent, low-level RhCMV shedding in saliva during the lactation period, with minimal systemic RhCMV-specific T cell responses.

CONCLUSIONS

Despite exposure to RhCMV shedding in breast milk and other maternal fluids, postnatal mother-to-child RhCMV transmission appears to be less efficient than that of HCMV. A greater understanding of the determinants of RhCMV transmission and its usefulness as a model of HCMV mucosal acquisition may provide insight into strategies to prevent HCMV infections in humans.

A new era in cytomegalovirus vaccinology: considerations for rational design of next-generation vaccines to prevent congenital cytomegalovirus infection

Human cytomegalovirus (HCMV), a member of the beta-herpesvirus family, is the most common cause of congenital infection worldwide as well as an important cause of morbidity in transplant recipients and immunosuppressed individuals. An estimated 1 in 150 infants are infected with HCMV at birth, which can result in lifelong, debilitating neurologic sequelae including microcephaly, sensorineural hearing loss, and cognitive impairment. Natural maternal immunity to HCMV decreases the frequency of reinfection and reduces risk of congenital transmission but does not completely protect against neonatal disease. Thus, a vaccine to reduce the incidence and severity of infant infection is a public health priority. A variety of candidate HCMV vaccine approaches have been tried previously, including live-attenuated viruses, glycoprotein subunit formulations, viral vectors, and single/bivalent DNA plasmids, but all have failed to reach target endpoints in clinical trials. Nevertheless, there is a great deal to be learned from the successes and failures of the HCMV vaccine field (both congenital and transplant-associated), as well as from vaccine development efforts for other herpesvirus pathogens including herpes simplex virus 1 and 2, varicella zoster virus, and Epstein-Barr virus. Here, we review those successes and failures, evaluating recent cutting-edge discoveries that have shaped the HCMV vaccine field and identifying topics of critical importance for future investigation. These considerations will inform rational design and evaluation of next-generation vaccines to prevent HCMV-associated congenital infection and disease.

Development and application of a multiplex assay for the simultaneous measurement of antibody responses elicited by common childhood vaccines

Because vaccine co-administration can affect elicited immune responses, it is important to evaluate new vaccines in the context of pre-existing vaccination schedules. This is particularly necessary for new pediatric vaccines, as the World Health Organization's infant immunization program already schedules several vaccines to be administered during the first months of life. To facilitate the assessment of inter-vaccine interference, we developed a pediatric vaccine multiplex assay (PVMA) to simultaneously measure antibodies against vaccines commonly administered to infants, including hepatitis B, Haemophilus influenzae type B, diphtheria, tetanus, pertussis, rubella, and respiratory syncytial virus (RSV). Comparison of antibody concentrations determined by enzyme-linked immunosorbent assays (ELISAs) and the PVMA demonstrated that the PVMA is highly sensitive, specific, reproducible, and accurate. Moreover, the PVMA requires half the time to assess a cohort compared to ELISAs, and only costs marginally more. Demonstrating the utility of the assay, we employed the PVMA to assess vaccine interference in the setting of a candidate vaccine, using the infant HIV vaccines from the completed Pediatric AIDS Clinical Trials Group (PACTG) protocols 230 and 326 as examples. There was no substantial difference in antibody concentrations between vaccine and placebo recipients, which suggests that HIV vaccination did not disrupt antibody responses elicited by routine pediatric vaccines. Thus, the PVMA is a reliable, high-throughput technique that requires minimal sample volume to measure multiple antibody concentrations concurrently, and is an efficient alternative to ELISAs for the measurement of vaccine-elicited antibody responses in large cohorts.

Tracking KLRC2 (NKG2C)+ memory-like NK cells in SIV+ and rhCMV+ rhesus macaques

Natural killer (NK) cells classically typify the nonspecific effector arm of the innate immune system, but have recently been shown to possess memory-like properties against multiple viral infections, most notably CMV. Expression of the activating receptor NKG2C is elevated on human NK cells in response to infection with CMV as well as HIV, and may delineate cells with memory and memory-like functions. A better understanding of how NKG2C+ NK cells specifically respond to these pathogens could be significantly advanced using nonhuman primate (NHP) models but, to date, it has not been possible to distinguish NKG2C from its inhibitory counterpart, NKG2A, in NHP because of unfaithful antibody cross-reactivity. Using novel RNA-based flow cytometry, we identify for the first time true memory NKG2C+ NK cells in NHP by gene expression (KLRC2), and show that these cells have elevated frequencies and diversify their functional repertoire specifically in response to rhCMV and SIV infections.

Infant transmitted/founder HIV-1 viruses from peripartum transmission are neutralization resistant to paired maternal plasma

Despite extensive genetic diversity of HIV-1 in chronic infection, a single or few maternal virus variants become the founders of an infant’s infection. These transmitted/founder (T/F) variants are of particular interest, as a maternal or infant HIV vaccine should raise envelope (Env) specific IgG responses capable of blocking this group of viruses. However, the maternal or infant factors that contribute to selection of infant T/F viruses are not well understood. In this study, we amplified HIV-1 env genes by single genome amplification from 16 mother-infant transmitting pairs from the U.S. pre-antiretroviral era Women Infant Transmission Study (WITS). Infant T/F and representative maternal non-transmitted Env variants from plasma were identified and used to generate pseudoviruses for paired maternal plasma neutralization sensitivity analysis. Eighteen out of 21 (85%) infant T/F Env pseudoviruses were neutralization resistant to paired maternal plasma. Yet, all infant T/F viruses were neutralization sensitive to a panel of HIV-1 broadly neutralizing antibodies and variably sensitive to heterologous plasma neutralizing antibodies. Also, these infant T/F pseudoviruses were overall more neutralization resistant to paired maternal plasma in comparison to pseudoviruses from maternal non-transmitted variants (p = 0.012). Altogether, our findings suggest that autologous neutralization of circulating viruses by maternal plasma antibodies select for neutralization-resistant viruses that initiate peripartum transmission, raising the speculation that enhancement of this response at the end of pregnancy could further reduce infant HIV-1 infection risk.

Mother to child transmission (MTCT) of HIV-1 can occur during pregnancy (in utero), at the time of delivery (peripartum) or by breastfeeding (postpartum). With the availability of anti-retroviral therapy (ART), rate of MTCT of HIV-1 have been significantly lowered. However, significant implementation challenges remain in resource-poor areas, making it difficult to eliminate pediatric HIV. An improved understanding of the viral population (escape variants from autologous neutralizing antibodies) that lead to infection of infants at time of transmission will help in designing immune interventions to reduce perinatal HIV-1 transmission. Here, we selected 16 HIV-1-infected mother-infant pairs from WITS cohort (from pre anti-retroviral era), where infants became infected peripartum. HIV-1 env gene sequences were obtained by the single genome amplification (SGA) method. The sensitivity of these infant Env pseudoviruses against paired maternal plasma and a panel of broadly neutralizing monoclonal antibodies (bNAbs) was analyzed. We demonstrated that the infant T/F viruses were more resistant against maternal plasma than non-transmitted maternal variants, but sensitive to most (bNAbs). Signature sequence analysis of infant T/F and non-transmitted maternal variants revealed the potential importance of V3 and MPER region for resistance against paired maternal plasma. These findings provide insights for the design of maternal immunization strategies to enhance neutralizing antibodies that target V3 region of autologous virus populations, which could work synergistically with maternal ARVs to further reduce the rate of peripartum HIV-1 transmission.

Predominant envelope variable loop 2-specific and gp120-specific antibody-dependent cellular cytotoxicity antibody responses in acutely SIV-infected African green monkeys

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.

Electronic supplementary material

The online version of this article (10.1186/s12977-018-0406-5) contains supplementary material, which is available to authorized users.

The Impact of IgG transplacental transfer on early life immunity

Pediatric vaccines have significantly reduced infectious disease-related infant mortality, but as protective immunity often require several infant vaccine doses; maternally-acquired antibodies are critical to protect infants during the first months of life. Consequently, immunization of pregnant women is an important strategy not only to protect mothers from infection, but also to provide immunity to young infants. Nevertheless, maternal immunization can also negatively impact early life immunity. In fact, maternal antibodies can interfere with the development of infant immune responses, though it is unclear if such interference is clinically significant. Moreover, the transplacental transfer of maternal immunoglobulin therapeutics can be harmful to the fetus. Thus, the risk/benefit of maternal immunization for both the mother and the fetus should be carefully weighed. In addition, it is critical to fully understand the mechanisms by which IgG is transferred across the placenta in order to develop optimal maternal and infant immunization strategies.

Progress toward Development of a Vaccine against Congenital Cytomegalovirus Infection

A vaccine against congenital human cytomegalovirus (CMV) infection is a major public health priority. Congenital CMV causes substantial long-term morbidity, particularly sensorineural hearing loss (SNHL), in newborns, and the public health impact of this infection on maternal and child health is underrecognized. Although progress toward development of a vaccine has been limited by an incomplete understanding of the correlates of protective immunity for the fetus, knowledge about some of the key components of the maternal immune response necessary for preventing transplacental transmission is accumulating. Moreover, although there have been concerns raised about observations indicating that maternal seropositivity does not fully prevent recurrent maternal CMV infections during pregnancy, it is becoming increasing clear that preconception immunity does confer some measure of protection against both CMV transmission and CMV disease (if transmission occurs) in the newborn infant. Although the immunity to CMV conferred by both infection and vaccination is imperfect, there are encouraging data emerging from clinical trials demonstrating the immunogenicity and potential efficacy of candidate CMV vaccines. In the face of the knowledge that between 20,000 and 30,000 infants are born with congenital CMV in the United States every year, there is an urgent and compelling need to accelerate the pace of vaccine trials. In this minireview, we summarize the status of CMV vaccines in clinical trials and provide a perspective on what would be required for a CMV immunization program to become incorporated into clinical practice.

Maternal immune correlates of protection against placental transmission of cytomegalovirus

Human cytomegalovirus (HCMV) is the most common congenitally transmitted pathogen worldwide, impacting an estimated 1 million newborns annually. In a subset of infected infants, congenital HCMV causes severe, long-lasting sequelae, including deafness, microcephaly, neurodevelopmental delay, and even death. Accordingly, a maternal vaccine to prevent congenital HCMV infection continues to be a top public health priority. Nevertheless, all vaccines tested to date have failed to meet clinical trial endpoints. Maternal immunity provides partial protection against congenital HCMV transmission, as vertical transmission from seropositive mothers is relatively rare. Therefore, an understanding of the maternal immune correlates of protection against HCMV congenital infection will be critical to inform design of an efficacious maternal vaccine. This review summarizes our understanding of the innate and adaptive immune correlates of protection against congenital transmission of HCMV, and discusses the advantages and applications of a novel nonhuman primate model of congenital CMV transmission to aid in rational vaccine design and evaluation.

chngpt: threshold regression model estimation and inference

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-017-1863-x) contains supplementary material, which is available to authorized users.

Rhesus monkeys for a nonhuman primate model of cytomegalovirus infections

Human cytomegalovirus (HCMV) is the leading opportunistic viral infection in solid organ transplant patients and is the most common congenitally transmitted pathogen worldwide. Despite the significant burden of disease HCMV causes in immunosuppressed patients and infected newborns, there are no licensed preventative vaccines or effective immunotherapeutic treatments for HCMV, largely due to our incomplete understanding of the immune correlates of protection against HCMV infection and disease. Though CMV species-specificity imposes an additional challenge in defining a suitable animal model for HCMV, nonhuman primate (NHP) CMVs are the most genetically related to HCMV. In this review, we discuss the advantages and applicability of rhesus monkey models for studying HCMV infections and pathogenesis and ultimately informing vaccine development.

The Role of Maternal HIV Envelope-Specific Antibodies and Mother-to-Child 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.

Geographic Disparities in Cytomegalovirus Infection During Pregnancy

BACKGROUND

Cytomegalovirus (CMV) is the most common infectious cause of fetal malformations and childhood hearing loss. CMV is more common among socially disadvantaged groups, and it clusters geographically in poor communities. We conducted a geospatial analysis of chronic and primary CMV infection among pregnant women around Durham, NC.

METHODS

We performed a geospatial analysis of subjects from an ongoing study of CMV infection among pregnant women using geographic information systems and spatial statistics. Subjects were categorized on the basis of results of their CMV immunoglobulin G avidity testing as seronegative, seropositive, or primary infection. We used generalized additive models to analyze the spatial distributions of individuals who fell into each category and to control for confounders such as race and age. We used a generalized estimating equation to correlate community-level variables with CMV status.

RESULTS

Of 3527 pregnant women aged 15 to 59 years, 93.4% were either white or black. CMV seropositivity was significantly more common among non-Hispanic white subjects than among minority subjects (odds ratio, 3.76 [95% confidence interval, 3.25-4.34]). We identified a cluster in which women had elevated odds of CMV seropositivity in the urban neighborhoods of Durham. Cases of primary CMV infection were more common in areas with higher-than-average CMV seroprevalence. Neighborhood median family income was associated inversely with the prevalence of chronic CMV.

CONCLUSIONS

We found a high prevalence of CMV seropositivity in urban low-income neighborhoods among pregnant women, particularly among racial and ethnic minorities. Seronegative pregnant women from these communities might be at heightened risk for primary CMV infection.

Neighborhood Disadvantage is Associated with High Cytomegalovirus Seroprevalence in Pregnancy

BACKGROUND

Cytomegalovirus (CMV) is the most common infectious cause of fetal malformations and childhood hearing loss. CMV is more common among socially disadvantaged groups, and geographically clusters in poor communities. The Area Deprivation Index (ADI) is a neighborhood-level index derived from census data that reflects material disadvantage.

METHODS

We performed a geospatial analysis to determine if ADI predicts the local odds of CMV seropositivity. We analyzed a dataset of 3527 women who had been tested for CMV antibodies during pregnancy. We used generalized additive models to analyze the spatial distribution of CMV seropositivity. Adjusted models included individual-level age and race and neighborhood-level ADI.

RESULTS

Our dataset included 1955 CMV seropositive women, 1549 who were seronegative, and 23 with recent CMV infection based on low avidity CMV antibodies. High ADI percentiles, representing greater neighborhood poverty, were significantly associated with the nonwhite race (48 vs. 22, p < 0.001) and CMV seropositivity (39 vs. 28, p < 0.001). Our unadjusted spatial models identified clustering of high CMV odds in poor, urban neighborhoods and clustering of low CMV odds in more affluent suburbs (local odds ratio 0.41 to 1.90). Adjustment for both individual race and neighborhood ADI largely eliminated this spatial variability. ADI remained a significant predictor of local CMV seroprevalence even after adjusting for individual race.

CONCLUSIONS

Neighborhood-level poverty as measured by the ADI is a race-independent predictor of local CMV seroprevalence among pregnant women.

Preexisting antibodies can protect against congenital cytomegalovirus infection in monkeys

Human cytomegalovirus (HCMV) is the most common congenital infection and a known cause of microcephaly, sensorineural hearing loss, and cognitive impairment among newborns worldwide. Natural maternal HCMV immunity reduces the incidence of congenital infection, but does not prevent the disease altogether. We employed a nonhuman primate model of congenital CMV infection to investigate the ability of preexisting antibodies to protect against placental CMV transmission in the setting of primary maternal infection and subsequent viremia, which is required for placental virus exposure. Pregnant, CD4+ T cell-depleted, rhesus CMV-seronegative (RhCMV-seronegative) rhesus monkeys were treated with either standardly produced hyperimmune globulin (HIG) from RhCMV-seropositive macaques or dose-optimized, potently RhCMV-neutralizing HIG prior to intravenous challenge with an RhCMV mixture. HIG passive infusion provided complete protection against fetal loss in both groups. The dose-optimized, RhCMV-neutralizing HIG additionally inhibited placental transmission of RhCMV and reduced viral replication and diversity. Our findings suggest that the presence of durable and potently neutralizing antibodies at the time of primary infection can prevent transmission of systemically replicating maternal RhCMV to the developing fetus, and therefore should be a primary target of vaccines to eliminate this neonatal infection.

Highly efficient maternal-fetal Zika virus transmission in pregnant rhesus macaques

Infection with Zika virus (ZIKV) is associated with human congenital fetal anomalies. To model fetal outcomes in nonhuman primates, we administered Asian-lineage ZIKV subcutaneously to four pregnant rhesus macaques. While non-pregnant animals in a previous study contemporary with the current report clear viremia within 10-12 days, maternal viremia was prolonged in 3 of 4 pregnancies. Fetal head growth velocity in the last month of gestation determined by ultrasound assessment of head circumference was decreased in comparison with biparietal diameter and femur length within each fetus, both within normal range. ZIKV RNA was detected in tissues from all four fetuses at term cesarean section. In all pregnancies, neutrophilic infiltration was present at the maternal-fetal interface (decidua, placenta, fetal membranes), in various fetal tissues, and in fetal retina, choroid, and optic nerve (first trimester infection only). Consistent vertical transmission in this primate model may provide a platform to assess risk factors and test therapeutic interventions for interruption of fetal infection. The results may also suggest that maternal-fetal ZIKV transmission in human pregnancy may be more frequent than currently appreciated.

Innate Immune Factors in Mothers' Breast Milk and Their Lack of Association With Rotavirus Vaccine Immunogenicity in Nicaraguan Infants

To better understand underlying causes of lower rotavirus vaccine effectiveness in low-middle income countries (LMICs), we measured innate antiviral factors in Nicaraguan mothers' milk and immune response to the first dose of the pentavalent rotavirus vaccine in corresponding infants. No relationship was found between concentrations of innate factors and rotavirus vaccine response.

Heterologous Protection against Asian Zika Virus Challenge in Rhesus Macaques

BACKGROUND

Zika virus (ZIKV; Flaviviridae, Flavivirus) was declared a public health emergency of international concern by the World Health Organization (WHO) in February 2016, because of the evidence linking infection with ZIKV to neurological complications, such as Guillain-Barre Syndrome in adults and congenital birth defects including microcephaly in the developing fetus. Because development of a ZIKV vaccine is a top research priority and because the genetic and antigenic variability of many RNA viruses limits the effectiveness of vaccines, assessing whether immunity elicited against one ZIKV strain is sufficient to confer broad protection against all ZIKV strains is critical. Recently, in vitro studies demonstrated that ZIKV likely circulates as a single serotype. Here, we demonstrate that immunity elicited by African lineage ZIKV protects rhesus macaques against subsequent infection with Asian lineage ZIKV.

METHODOLOGY/PRINCIPAL FINDINGS

Using our recently developed rhesus macaque model of ZIKV infection, we report that the prototypical ZIKV strain MR766 productively infects macaques, and that immunity elicited by MR766 protects macaques against heterologous Asian ZIKV. Furthermore, using next generation deep sequencing, we found in vivo restoration of a putative N-linked glycosylation site upon replication in macaques that is absent in numerous MR766 strains that are widely being used by the research community. This reversion highlights the importance of carefully examining the sequence composition of all viral stocks as well as understanding how passage history may alter a virus from its original form.

CONCLUSIONS/SIGNIFICANCE

An effective ZIKV vaccine is needed to prevent infection-associated fetal abnormalities. Macaques whose immune responses were primed by infection with East African ZIKV were completely protected from detectable viremia when subsequently rechallenged with heterologous Asian ZIKV. Therefore, these data suggest that immunogen selection is unlikely to adversely affect the breadth of vaccine protection, i.e., any Asian ZIKV immunogen that protects against homologous challenge will likely confer protection against all other Asian ZIKV strains.

Maternal Antibody Responses and Nonprimary Congenital Cytomegalovirus Infection of HIV-1-Exposed Infants

Risk of congenital cytomegalovirus (cCMV) transmission is highly dependent on the presence of preexisting maternal immunity, with the lowest rates observed in CMV-seroimmune populations. Among infants of CMV-seroimmune women, those who are exposed to human immunodeficiency virus (HIV) have an increased risk of acquiring cCMV infection as compared to HIV-unexposed infants. To better understand the risk factors of nonprimary cCMV transmission in HIV-infected women, we performed a case-control study in which CMV-specific plasma antibody responses from 19 CMV-transmitting and 57 CMV-nontransmitting women with chronic CMV/HIV coinfection were evaluated for the ability to predict the risk of cCMV infection. Primary multivariable conditional logistic regression analysis revealed an association between epithelial-tropic CMV neutralizing titers and a reduced risk of cCMV transmission (odds ratio [OR], 0.18; 95% confidence interval [CI], .03-.93; P = .04), although this effect was not significant following correction for multiple comparisons (false-discovery rate, 0.12). Exploratory analysis of the CMV specificity of plasma antibodies revealed that immunoglobulin G (IgG) responses against the glycoprotein B (gB) neutralizing epitope AD-2 had a borderline association with low risk of transmission (OR, 0.72; 95% CI, .51-1.00; P = .05), although this was not confirmed in a post hoc plasma anti-AD-2 IgG blocking assay. Our data suggest that maternal neutralizing antibody responses may play a role in protection against cCMV in HIV/CMV-coinfected populations.

Symptomatic Postnatal Cytomegalovirus Testing among Very Low-Birth-Weight Infants: Indications and Outcomes

Objective The objective of this study was to describe the indications for postnatal cytomegalovirus (CMV) testing among very low-birth-weight (VLBW, birth weight [BW] < 1,500 g) infants, clinical characteristics of infected infants, and adverse outcomes associated with CMV infection. Study Design This is a single-center, retrospective study of 2,132 VLBW infants from 1999 to 2013. Results In this study, 145 (6.8%) infants out of 2,132 were evaluated for postnatal CMV infection and 27 (18.6%) infants out of 145 were infected. CMV-tested infants were of significantly lower gestational age and BW compared with untested VLBW infants (p < 0.001). Respiratory decompensation and thrombocytopenia were the findings most commonly associated with infection. CMV-infected infants had significantly more exposure to mechanical ventilation and longer duration of hospitalization. Adjusting for multiple predictors of respiratory morbidity, the incidence of bronchopulmonary dysplasia (BPD) was significantly elevated among infants diagnosed with postnatal CMV infection (odds ratio, 4.0 [95% confidence interval, 1.3-12.4); p, 0.02.) Conclusion Symptomatic postnatal CMV infection was diagnosed in 1.3% of VLBW infants, most commonly among infants with BW < 1,000 g with respiratory instability and thrombocytopenia. Similar to late-onset bacterial infection, symptomatic postnatal CMV infection may be an independent contributor to the development of BPD. This possibility should be addressed in a prospective study of extremely low BW infants.

A rhesus macaque model of Asian-lineage Zika virus infection

Infection with Asian-lineage Zika virus (ZIKV) has been associated with Guillain–Barré syndrome and fetal abnormalities, but the underlying mechanisms remain poorly understood. Animal models of infection are thus urgently needed. Here we show that rhesus macaques are susceptible to infection by an Asian-lineage ZIKV closely related to strains currently circulating in the Americas. Following subcutaneous inoculation, ZIKV RNA is detected in plasma 1 day post infection (d.p.i.) in all animals (N=8, including 2 pregnant animals), and is also present in saliva, urine and cerebrospinal fluid. Non-pregnant and pregnant animals remain viremic for 21 days and for up to at least 57 days, respectively. Neutralizing antibodies are detected by 21 d.p.i. Rechallenge 10 weeks after the initial challenge results in no detectable virus replication, indicating protective immunity against homologous strains. Therefore, Asian-lineage ZIKV infection of rhesus macaques provides a relevant animal model for studying pathogenesis and evaluating potential interventions against human infection, including during pregnancy.

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.

The Presence and Anti-HIV-1 Function of Tenascin C in Breast Milk and Genital Fluids

Tenascin-C (TNC) is a newly identified innate HIV-1-neutralizing protein present in breast milk, yet its presence and potential HIV-inhibitory function in other mucosal fluids is unknown. In this study, we identified TNC as a component of semen and cervical fluid of HIV-1-infected and uninfected individuals, although it is present at a significantly lower concentration and frequency compared to that of colostrum and mature breast milk, potentially due to genital fluid protease degradation. However, TNC was able to neutralize HIV-1 after exposure to low pH, suggesting that TNC could be active at low pH in the vaginal compartment. As mucosal fluids are complex and contain a number of proteins known to interact with the HIV-1 envelope, we further studied the relationship between the concentration of TNC and neutralizing activity in breast milk. The amount of TNC correlated only weakly with the overall innate HIV-1-neutralizing activity of breast milk of uninfected women and negatively correlated with neutralizing activity in milk of HIV-1 infected women, indicating that the amount of TNC in mucosal fluids is not adequate to impede HIV-1 transmission. Moreover, the presence of polyclonal IgG from milk of HIV-1 infected women, but not other HIV-1 envelope-binding milk proteins or monoclonal antibodies, blocked the neutralizing activity of TNC. Finally, as exogenous administration of TNC would be necessary for it to mediate measurable HIV-1 neutralizing activity in mucosal compartments, we established that recombinantly produced TNC has neutralizing activity against transmitted/founder HIV-1 strains that mimic that of purified TNC. Thus, we conclude that endogenous TNC concentration in mucosal fluids is likely inadequate to block HIV-1 transmission to uninfected individuals.

Postnatal Cytomegalovirus Infection and the Risk for Bronchopulmonary Dysplasia

IMPORTANCE

Postnatally acquired cytomegalovirus (CMV) is typically benign in term infants but in very low-birth-weight (VLBW) infants can cause pneumonitis and sepsislike illness. Whether postnatal CMV infection results in long-term pulmonary sequelae in these infants is unknown.

OBJECTIVE

To investigate the association between postnatal CMV infection and bronchopulmonary dysplasia (BPD) and mortality in a large multicenter cohort of VLBW infants.

DESIGN, SETTING, AND PARTICIPANTS

Conducted between October 2014 and June 2015, this propensity-matched retrospective cohort study involved 101,111 hospitalized VLBW (<1500 g) infants at 348 neonatal intensive care units in the United States from 1997 to 2012. We matched infants with postnatal CMV infection 1:1 to comparison infants using propensity scores, and we used Poisson regression to examine the effect of postnatal CMV on the combined risk for death or BPD at 36 weeks' postmenstrual age. To describe features of postnatal CMV infection, we extracted clinical and laboratory data from 7 days before until 7 days after infants met criteria for postnatal CMV.

EXPOSURES

Postnatal CMV infection was defined as a diagnosis of CMV or detection of CMV from blood, urine, cerebrospinal fluid, or respiratory secretions on or after day of life 21. Infants with a CMV diagnosis or virologic detection of CMV prior to day of life 21 were not considered to have postnatal infection.

MAIN OUTCOMES AND MEASURES

The primary outcome was death or BPD at 36 weeks' postmenstrual age.

RESULTS

Of 101,111 infants, 328 (0.3%) had postnatal CMV infection. We matched a comparison infant to 303 CMV-infected infants (92%) for a final cohort of 606 infants. The median gestational age and birth weight of this cohort were 25 weeks and 730 g, respectively. Postnatal CMV infection was associated with an increased risk for death or BPD at 36 weeks' postmenstrual age (risk ratio, 1.21; 95% CI, 1.10-1.32) and BPD (risk ratio, 1.33; 95% CI, 1.19-1.50). Changes in cardiorespiratory status associated with postnatal CMV infection included a new requirement for vasopressor medications (9%; n = 29), intubation for mechanical ventilation (15%; n = 49), a new oxygen requirement (28%; n = 91), and death (1.2%; n = 4).

CONCLUSIONS AND RELEVANCE

In VLBW infants, postnatal CMV infection was associated with increased risk for BPD. Further studies are needed to determine the role of preventive measures against CMV in this population.

The Excess Burden of Cytomegalovirus in African American Communities: A Geospatial Analysis

CMV seroprevalence is much higher in African-Americans than Caucasians. CMV seropositivity is geographically clustered, largely due to racial segregation. African-American communities may suffer a disproportionate public health burden due to CMV

Background. Cytomegalovirus (CMV) is a common cause of birth defects and hearing loss in infants and opportunistic infections in the immunocompromised. Previous studies have found higher CMV seroprevalence rates among minorities and among persons with lower socioeconomic status. No studies have investigated the geographic distribution of CMV and its relationship to age, race, and poverty in the community.

Methods. We identified patients from 6 North Carolina counties who were tested in the Duke University Health System for CMV immunoglobulin G. We performed spatial statistical analyses to analyze the distributions of seropositive and seronegative individuals.

Results. Of 1884 subjects, 90% were either white or African American. Cytomegalovirus seropositivity was significantly more common among African Americans (73% vs 42%; odds ratio, 3.31; 95% confidence interval, 2.7–4.1), and this disparity persisted across the life span. We identified clusters of high and low CMV odds, both of which were largely explained by race. Clusters of high CMV odds were found in communities with high proportions of African Americans.

Conclusions. Cytomegalovirus seropositivity is geographically clustered, and its distribution is strongly determined by a community's racial composition. African American communities have high prevalence rates of CMV infection, and there may be a disparate burden of CMV-associated morbidity in these communities.

Breast Milk of HIV-Positive Mothers Has Potent and Species-Specific In Vivo HIV-Inhibitory Activity

Despite the nutritional and health benefits of breast milk, breast milk can serve as a vector for mother-to-child HIV transmission. Most HIV-infected infants acquire HIV through breastfeeding. Paradoxically, most infants breastfed by HIV-positive women do not become infected. This is potentially attributed to anti-HIV factors in breast milk. Breast milk of HIV-negative women can inhibit HIV infection. However, the HIV-inhibitory activity of breast milk from HIV-positive mothers has not been evaluated. In addition, while significant differences in breast milk composition between transmitting and nontransmitting HIV-positive mothers have been correlated with transmission risk, the HIV-inhibitory activity of their breast milk has not been compared. This knowledge may significantly impact the design of prevention approaches in resource-limited settings that do not deny infants of HIV-positive women the health benefits of breast milk. Here, we utilized bone marrow/liver/thymus humanized mice to evaluate the in vivo HIV-inhibitory activity of breast milk obtained from HIV-positive transmitting and nontransmitting mothers. We also assessed the species specificity and biochemical characteristics of milk's in vivo HIV-inhibitory activity and its ability to inhibit other modes of HIV infection. Our results demonstrate that breast milk of HIV-positive mothers has potent HIV-inhibitory activity and indicate that breast milk can prevent multiple routes of infection. Most importantly, this activity is unique to human milk. Our results also suggest multiple factors in breast milk may contribute to its HIV-inhibitory activity. Collectively, our results support current recommendations that HIV-positive mothers in resource-limited settings exclusively breastfeed in combination with antiretroviral therapy.

IMPORTANCE

Approximately 240,000 children become infected with HIV annually, the majority via breastfeeding. Despite daily exposure to virus in breast milk, most infants breastfed by HIV-positive women do not acquire HIV. The low risk of breastfeeding-associated HIV transmission is likely due to antiviral factors in breast milk. It is well documented that breast milk of HIV-negative women can inhibit HIV infection. Here, we demonstrate, for the first time, that breast milk of HIV-positive mothers (nontransmitters and transmitters) inhibits HIV transmission. We also demonstrate that breast milk can prevent multiple routes of HIV acquisition and that this activity is unique to human milk. Collectively, our results support current guidelines which recommend that HIV-positive women in resource-limited settings exclusively breastfeed in combination with infant or maternal antiretroviral therapy.

Maternal HIV-1 envelope-specific antibody responses and reduced risk of perinatal transmission

Despite the wide availability of antiretroviral drugs, more than 250,000 infants are vertically infected with HIV-1 annually, emphasizing the need for additional interventions to eliminate pediatric HIV-1 infections. Here, we aimed to define humoral immune correlates of risk of mother-to-child transmission (MTCT) of HIV-1, including responses associated with protection in the RV144 vaccine trial. Eighty-three untreated, HIV-1-transmitting mothers and 165 propensity score-matched nontransmitting mothers were selected from the Women and Infants Transmission Study (WITS) of US nonbreastfeeding, HIV-1-infected mothers. In a multivariable logistic regression model, the magnitude of the maternal IgG responses specific for the third variable loop (V3) of the HIV-1 envelope was predictive of a reduced risk of MTCT. Neutralizing Ab responses against easy-to-neutralize (tier 1) HIV-1 strains also predicted a reduced risk of peripartum transmission in secondary analyses. Moreover, recombinant maternal V3-specific IgG mAbs mediated neutralization of autologous HIV-1 isolates. Thus, common V3-specific Ab responses in maternal plasma predicted a reduced risk of MTCT and mediated autologous virus neutralization, suggesting that boosting these maternal Ab responses may further reduce HIV-1 MTCT.

Immune-based interventions to prevent postnatal HIV-1 transmission

Despite global scale-up in antiretroviral-based prevention of mother-to-child transmission services, more than 250 000 infants become infected with HIV-1 each year. Breast milk transmission is responsible for almost half of these infections. The development of alternative strategies to prevent postnatal HIV-1 transmission is imperative to achieve a generation free of HIV-1.

Perinatal cytomegalovirus and varicella zoster virus infections: epidemiology, prevention, and treatment

Mother-to-child transmission of cytomegalovirus (CMV) and varicella zoster virus (VZV) can lead to severe birth defects and neurologic impairment of infants. Congenital CMV complicates up to 1% of all pregnancies globally. Although antiviral treatment of infants congenitally infected with CMV can ameliorate the CMV-associated hearing loss and developmental delay, interventions to prevent congenital CMV infection and the associated neurologic impairments are still being evaluated. Congenital VZV infection is rare. Active and passive immunization strategies to prevent perinatal CMV infection with similar efficacy to those established to prevent perinatal VZV infections are critically needed in pediatric health.

Refinement of a protocol for the induction of lactation in nonpregnant nonhuman primates by using exogenous hormone treatment

Obtaining sufficient quantities of milk from NHP is necessary for pharmacologic and immunologic studies required for the development and safety assessment of drugs and vaccines to be used in the maternal-infant setting. We previously induced lactation in nonpregnant female rhesus macaques (RM, Macaca mulatta) and African green monkeys (AGM, Chlorocebus sabaeus) for studies of immune responses in milk, but the volume collected was variable. To improve lactation induction protocols for nonbreeding nonhuman primates, we investigated serum hormone levels and collection protocols in AGM and RM. Here, we correlated milk volume with serum levels of endogenous and administered hormones: estradiol, prolactin, progesterone, and medroxyprogesterone in RM and AGM. We also investigated whether age, parity or the timing of milk collections were associated with the volume of milk collected from the AGM and RM in which lactation was induced by using exogenous hormones. We found an inverse correlation with serum estradiol and milk volume in the RM but no significant correlation between milk volumes and the remaining serum hormone levels in the induced RM or AGM. In addition, HIL AGM had higher peak estradiol levels than did naturally lactating AGM. A revised estradiol-sparing protocol increased milk volumes in the AGM. In addition, milk volume in RM was greater in the morning than the afternoon. In conclusion, we have refined a lactation induction protocol in nonpregnant primates, which is a needed alternative to using nursing primates for the assessment of drug levels and immune responses in milk.

Infant HIV type 1 gp120 vaccination elicits robust and durable anti-V1V2 immunoglobulin G responses and only rare envelope-specific immunoglobulin A responses

BACKGROUND

Infant responses to vaccines can be impeded by maternal antibodies and immune system immaturity. It is therefore unclear whether human immunodeficiency virus type 1 (HIV-1) vaccination would elicit similar responses in adults and infants.

METHOD

HIV-1 Env-specific antibody responses were evaluated in 2 completed pediatric vaccine trials. In the Pediatric AIDS Clinical Trials Group (PACTG) 230 protocol, infants were vaccinated with 4 doses of Chiron rgp120 with MF59 (n=48), VaxGen rgp120 with aluminum hydroxide (alum; n=49), or placebo (n=19) between 0 and 20 weeks of age. In PACTG 326, infants received 4 doses of ALVAC-HIV-1/AIDSVAX B/B with alum (n=9) or placebo (n=13) between 0 and 12 weeks of age.

RESULTS

By 52 weeks of age, the majority of maternally acquired antibodies had waned and vaccine Env-specific immunoglobulin G (IgG) responses in vaccinees were higher than in placebo recipients. Chiron vaccine recipients had higher and more-durable IgG responses than VaxGen vaccine recipients or ALVAC/AIDSVAX vaccinees, with vaccine-elicited IgG responses still detectable in 56% of recipients at 2 years of age. Remarkably, at peak immunogenicity, the concentration of anti-V1V2 IgG, a response associated with a reduced risk of HIV-1 acquisition in the RV144 adult vaccine trial, was 22-fold higher in Chiron vaccine recipients, compared with RV144 vaccinees.

CONCLUSION

As exemplified by the Chiron vaccine regimen, vaccination of infants against HIV-1 can induce robust, durable Env-specific IgG responses, including anti-V1V2 IgG.