HIV-Exposed Uninfected Infants Show Robust Memory B-Cell Responses in Spite of a Delayed Accumulation of Memory B Cells: an Observational Study in the First 2 Years of Life

Breadth of Fc-mediated effector function correlates with clinical immunity following human malaria challenge

Malaria is a life-threatening disease of global health importance, particularly in sub-Saharan Africa. The growth inhibition assay (GIA) is routinely used to evaluate, prioritize, and quantify the efficacy of malaria blood-stage vaccine candidates but does not reliably predict either naturally acquired or vaccine-induced protection. Controlled human malaria challenge studies in semi-immune volunteers provide an unparalleled opportunity to robustly identify mechanistic correlates of protection. We leveraged this platform to undertake a head-to-head comparison of seven functional antibody assays that are relevant to immunity against the erythrocytic merozoite stage of Plasmodium falciparum. Fc-mediated effector functions were strongly associated with protection from clinical symptoms of malaria and exponential parasite multiplication, while the gold standard GIA was not. The breadth of Fc-mediated effector function discriminated clinical immunity following the challenge. These findings present a shift in the understanding of the mechanisms that underpin immunity to malaria and have important implications for vaccine development.

Defective Monocyte Enzymatic Function and an Inhibitory Immune Phenotype in Human Immunodeficiency Virus-Exposed Uninfected African Infants in the Era of Antiretroviral Therapy

BACKGROUND

Human immunodeficiency virus-exposed uninfected (HEU) infants are a rapidly expanding population in sub-Saharan Africa and are highly susceptible to encapsulated bacterial disease in the first year of life. The mechanism of this increased risk is still poorly understood. We investigated whether human immunodeficiency virus (HIV)-exposure dysregulates HEU immunity, vaccine-antibody production, and human herpes virus amplify this effect.

METHODS

Thirty-four HIV-infected and 44 HIV-uninfected pregnant women were recruited into the birth cohort and observed up to 6 weeks of age; and then a subsequent 43 HIV-infected and 61 HIV-uninfected mother-infant pairs were recruited into a longitudinal infant cohort at either: 5-7 to 14-15; or 14-15 to 18-23 weeks of age. We compared monocyte function, innate and adaptive immune cell phenotype, and vaccine-induced antibody responses between HEU and HIV-unexposed uninfected (HU) infants.

RESULTS

We demonstrate (1) altered monocyte phagosomal function and B-cell subset homeostasis and (2) lower vaccine-induced anti-Haemophilus influenzae type b (Hib) and anti-tetanus toxoid immunoglobulin G titers in HEU compared with HU infants. Human herpes virus infection was similar between HEU and HU infants.

CONCLUSIONS

In the era of antiretroviral therapy-mediated viral suppression, HIV exposure may dysregulate monocyte and B-cell function, during the vulnerable period of immune maturation. This may contribute to the high rates of invasive bacterial disease and pneumonia in HEU infants.

Normalization of B Cell Subsets but Not T Follicular Helper Phenotypes in Infants With Very Early Antiretroviral Treatment

Introduction: Infant HIV-1-infection is associated with high morbidity and mortality if antiretroviral treatment (ART) is not initiated promptly. We characterized development of circulating T follicular helper cells (cTfh) and their relationship to naïve/memory B cell subsets in a cohort of neonates initiating ART within the first week of life. Methods: Infants were diagnosed within 48 hours of birth and started ART as soon as possible. The frequency and phenotype of cTfh and B cells were analyzed at enrollment (birth -19 days) and at 4, 12, and 72 weeks of age in blood of 27 HIV-1-intrauterine-infected and 25 HIV-1 exposed uninfected (HEU) infants as part of a study in Johannesburg, South Africa. cTfh cells were divided into Tfh1, Tfh2, and Tfh17 subsets. B cell phenotypes were defined as naïve, resting memory, activated memory and tissue-like memory cells. Results: HIV-1-infected infants had higher frequencies of cTfh cells than HEU infants up to 12 weeks of age and these cTfh cells were polarized toward the Tfh1 subset. Higher frequencies of Tfh1 and lower frequencies of Tfh2 and Tfh17 correlated with lower CD4+ T cell percentages. Lower frequencies of resting memory, with corresponding higher frequencies of activated memory B cells, were observed with HIV-1 infection. Importantly, dysregulations in B cell, but not cTfh cell, subsets were normalized by 72 weeks. Conclusion: Very early ART initiation in HIV-1-infected infants normalizes B cell subsets but does not fully normalize perturbations in cTfh cell subsets which remain Tfh1 polarized at 72 weeks. It remains to be determined if very early ART improves vaccine antibody responses despite the cTfh and B cell perturbations observed over the time course of this study.

Peripheral blood mononuclear cell transcriptomes reveal an over-representation of down-regulated genes associated with immunity in HIV-exposed uninfected infants

HIV-exposed uninfected (HEU) infants are disproportionately at a higher risk of morbidity and mortality, as compared to HIV-unexposed uninfected (HUU) infants. Here, we used transcriptional profiling of peripheral blood mononuclear cells to determine immunological signatures of in utero HIV exposure. We identified 262 differentially expressed genes (DEGs) in HEU compared to HUU infants. Weighted gene co-expression network analysis (WGCNA) identified six modules that had significant associations with clinical traits. Functional enrichment analysis on both DEGs and the six significantly associated modules revealed an enrichment of G-protein coupled receptors and the immune system, specifically affecting neutrophil function and antibacterial responses. Additionally, malaria pathogenicity genes (thrombospondin 1-(THBS 1), interleukin 6 (IL6), and arginine decarboxylase 2 (ADC2)) were down-regulated. Of interest, the down-regulated immunity genes were positively correlated to the expression of epigenetic factors of the histone family and high-mobility group protein B2 (HMGB2), suggesting their role in the dysregulation of the HEU transcriptional landscape. Overall, we show that genes primarily associated with neutrophil mediated immunity were repressed in the HEU infants. Our results suggest that this could be a contributing factor to the increased susceptibility to bacterial infections associated with higher morbidity and mortality commonly reported in HEU infants.

Measles Immunity at 4.5 Years of Age Following Vaccination at 9 and 15-18 Months of Age Among Human Immunodeficiency Virus (HIV)-infected, HIV-exposed-uninfected, and HIV-unexposed Children

BACKGROUND

Human immunodeficiency virus (HIV)-infected and HIV-exposed-uninfected (HEU) children may be at increased risk of measles infection due to waning of immunity following vaccination. We evaluated persistence of antibodies to measles vaccination at 4.5 years of age in HIV-unexposed, HEU, and HIV-infected children with CD4+ ≥25% previously randomized to immediate antiretroviral therapy (ART) interrupted at 12 months (HIV/Immed-ART-12), 24 months (HIV/Immed-ART-24), or when clinically/immunologically indicated (HIV/Def-ART). The HIV/Def-ART group initiated ART by median 5.8 (interquartile range, 4.4-10.3) months of age.

METHODS

In this study, HIV-unexposed (n = 95), HEU (n = 84), HIV/Immed-ART-12 (n = 70), HIV/Immed-ART-24 (n = 70), and HIV/Def-ART (n = 62) children were scheduled to receive measles vaccination at age 9 and 15-18 months. Antimeasles serum immunoglobulin G titers were quantified using enzyme-linked immunosorbent assay at 4.5 years.

RESULTS

Compared with HIV-unexposed children (2860 mIU/mL), measles antibody geometric mean titers (GMTs) were significantly lower in both HIV/Immed-ART-12 (571; P < .001) and HIV/Immed-ART-24 (1136; P < .001) but similar in the HIV/Def-ART (2777) and HEU (3242) groups. Furthermore, compared with HIV-unexposed, antibody titers ≥330 mIU/mL (ie, presumed serocorrelate for protection; 99%) were also significantly lower in HIV/Immed-ART-12 (70%; P < .001) and HIV/Immed-ART-24 (83%; P < .001) but similar in the HIV/Def-ART (90%) and HEU (98%) groups.

CONCLUSIONS

HIV-infected children in whom ART was interrupted at either 12 or 24 months had lower GMTs and lower proportions with seroprotective titers than HIV-unexposed children, indicating a potential downside of ART treatment interruption.

CLINICAL TRIALS REGISTRATION

NCT00099658 and NCT00102960.

Detecting Vertical Zika Transmission: Emerging Diagnostic Approaches for an Emerged Flavivirus

Zika virus (Zika) was recently responsible for a massive epidemic that spread throughout Latin America and beyond. Though Zika is typically asymptomatic or self-limiting, the sheer numbers of Zika infections led to the identification of unexpected phenotypes including sexual transmission, Guillain-Barré syndrome, and teratogenicity. Thousands of infants in South, Central, and North America have now been born with microcephaly or one of a number of fetal anomalies constituting the congenital Zika syndrome (CZS). Diagnosing CZS is based on a combination of clinical risk assessment and laboratory testing (which includes determining whether the mother has experienced a possible Zika infection during her pregnancy). A newborn suspected of having congenital Zika infection (due to maternal Zika infection or a birth defect described in association with congenital Zika infection) is then specifically tested for presence of Zika virus in neonatal tissue or anti-Zika IgM in the blood or cerebrospinal fluid. Though the guidelines are clear, there is room for considerable practice variation to emerge from individualized patient-provider encounters, largely due to limitations in diagnostic testing for Zika. The natural history of Zika further obscures our ability to know who, when, and how to test. Molecular diagnostics are highly specific but may not serve well those with asymptomatic infection. Serologic assays expand the diagnostic window but are complicated by cross-reactivity among related flaviviruses and passive immunity transferred from mother to baby. Furthermore, existing and emerging diagnostic tools may not be widely available due to limitations in resources and infrastructure of health systems in affected areas. Improvements in assay parameters as well as advances in platforms and deployability hold promise for optimizing diagnostic approaches for congenital Zika infection. The diagnostic tools and technologies under development must be integrated with forthcoming clinical knowledge of congenital Zika infection to fully realize the value that laboratory testing holds for diagnosing in utero mother to child transmission but also for understanding, predicting, and managing the health outcomes due to congenital Zika infection.

Safety and Immunogenicity of Measles Vaccination in HIV-Infected and HIV-Exposed Uninfected Children: A Systematic Review and Meta-Analysis

BACKGROUND

HIV-infected and HIV-exposed uninfected (HEU) children have an increased risk of measles that may be due to altered immune responses or suboptimal timing of measles vaccination. We aimed to evaluate the safety and immunogenicity of measles vaccination in HIV-infected and HEU children.

METHODS

For this systematic review and meta-analysis, we searched PubMed, Embase, Cochrane Library, CINAHL, Global Health Library and IndMED on May 9, 2018. Studies were included if they reported on safety or seroresponse (either seroprotection/seropositivity/seroconversion) after measles vaccination in HIV-infected or HEU children. We calculated pooled estimates to compare immunogenicity outcomes between HIV-infected, HEU and HIV-unexposed children, using risk ratios [RRs] (with 95%CIs). PROSPERO registration number: CRD42017057411.

FINDINGS

Seventy-one studies met the inclusion criteria (15,363 children). Twenty-eight studies reported on safety; vaccine-associated adverse events and deaths were uncommon. Sixty-two studies reported on immunogenicity, 27 were included in the meta-analysis. HIV-infected children had lower seroresponse rates after primary vaccination compared with HIV-unexposed (RR 0.74; 95%CI: 0.61-0.90, I 2  = 85.9%) and HEU children (0.78; 0.69-0.88, I 2  = 77.1%), which was mitigated by antiretroviral therapy and time interval between vaccination and serology. HEU and HIV-unexposed children had similar seroresponses. Vaccination at 6-months resulted in similar proportions of HIV-infected children having seroresponse compared with HIV-unexposed (0.96; 0.77-1.19) and HEU children (1.00; 0.73-1.37, I 2  = 63.7%).

INTERPRETATION

Primary measles vaccination at 6-months of age may provide protection against measles during early infancy in settings with high prevalence of maternal HIV-infection, however, further studies are needed to evaluate this strategy in HEU children and HIV-infected children receiving antiretroviral therapy.

FUNDING

South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation in Vaccine Preventable Diseases; Medical Research Council: Respiratory and Meningeal Pathogens Research Unit.

Cytomegalovirus viraemia is associated with poor growth and T-cell activation with an increased burden in HIV-exposed uninfected infants

Objective:

Factors associated with poor health in HIV-exposed-uninfected (HEU) infants are poorly defined. We describe the prevalence and correlates of cytomegalovirus (CMV) viraemia in HEU and HIV-unexposed-uninfected (HUU) infants, and quantify associations with anthropometric, haematological, and immunological outcomes.

Design:

Cross-sectional, including HEU and HUU infants from rural coastal Kenya.

Methods:

Infants aged 2–8 months were studied. The primary outcome was CMV viraemia and viral load, determined by quantitative PCR. Correlates were tested by logistic and linear regression; coefficients were used to describe associations between CMV viraemia and clinical/immunological parameters.

Results:

In total, 42 of 65 (64.6%) infants had CMV viraemia [median viral load, 3.0 (interquartile ranges: 2.7–3.5) log₁₀ IU/ml]. Compared to community controls, HEU infants had six-fold increased odds of being viraemic (adjusted odds ratio 5.95 [95% confidence interval: 1.82–19.36], P = 0.003). Age, but not HEU/HUU status, was a strong correlate of CMV viral load (coefficient = −0.15, P = 0.009). CMV viral load associated negatively with weight-for-age (WAZ) Z-score (coefficient =  −1.06, P = 0.008) and head circumference-for-age Z-score (coefficient =  −1.47, P = 0.012) and positively with CD8⁺ T-cell coexpression of CD38/human leucocyte antigen DR (coefficient = 15.05, P = 0.003).

Conclusion:

The odds of having CMV viraemia was six-fold greater in HEU than HUU infants when adjusted for age. CMV viral load was associated with adverse growth and heightened CD8⁺ T-cell immune activation. Longitudinal assessments of the clinical effects of primary CMV infection and associated immunomodulation in early life in HEU and HUU populations are warranted.

Immunisation of two rodent species with new live-attenuated mutants of Yersinia pestis CO92 induces protective long-term humoral- and cell-mediated immunity against pneumonic plague

We showed recently that the live-attenuated Δlpp ΔmsbB Δail and Δlpp ΔmsbB::ailL2 mutants of Yersinia pestis CO92 provided short-term protection to mice against developing subsequent lethal pneumonic plague. These mutants were either deleted for genes encoding Braun lipoprotein (Lpp), an acetyltransferase (MsbB) and the attachment invasion locus (Ail) (Δlpp ΔmsbB Δail) or contained a modified version of the ail gene with diminished virulence (Δlpp ΔmsbB::ailL2). Here, long-term immune responses were first examined after intramuscular immunisation of mice with the above-mentioned mutants, as well as the newly constructed Δlpp ΔmsbB Δpla mutant, deleted for the plasminogen-activator protease (pla) gene instead of ail. Y. pestis-specific IgG levels peaked between day 35 and 56 in the mutant-immunised mice and were sustained until the last tested day 112. Splenic memory B cells peaked earlier (day 42) before declining in the Δlpp ΔmsbB::ailL2 mutant-immunised mice while being sustained for 63 days in the Δlpp ΔmsbB Δail and Δlpp ΔmsbB Δpla mutant-immunised mice. Splenic CD4⁺ T cells increased in all immunised mice by day 42 with differential cytokine production among the immunised groups. On day 120, immunised mice were exposed intranasally to wild-type (WT) CO92, and 80–100% survived pneumonic challenge. Mice immunised with the above-mentioned three mutants had increased innate as well as CD4⁺ responses immediately after WT CO92 exposure, and coupled with sustained antibody production, indicated the role of both arms of the immune response in protection. Likewise, rats vaccinated with either Δlpp ΔmsbB Δail or the Δlpp ΔmsbB Δpla mutant also developed long-term humoral and cell-mediated immune responses to provide 100% protection against developing pneumonic plague. On the basis of the attenuated phenotype, the Δlpp ΔmsbB Δail mutant was recently excluded from the Centers for Disease Control and Prevention select agent list.