Imbalance of naive and memory T lymphocytes with sustained high cellular activation during the first year of life from uninfected children born to HIV-1-infected mothers on HAART

Premature skewing of T cell receptor clonality and delayed memory expansion in HIV-exposed infants

While preventing vertical HIV transmission has been very successful, HIV-exposed uninfected infants (iHEU) experience an elevated risk to infections compared to HIV-unexposed and uninfected infants (iHUU). Here we present a longitudinal multimodal analysis of infant immune ontogeny that highlights the impact of HIV/ARV exposure. Using mass cytometry, we show alterations in T cell memory differentiation between iHEU and iHUU being significant from week 15 of life. The altered memory T cell differentiation in iHEU was preceded by lower TCR Vβ clonotypic diversity and linked to TCR clonal depletion within the naïve T cell compartment. Compared to iHUU, iHEU had elevated CD56loCD16loPerforin+CD38+CD45RA+FcεRIγ+ NK cells at 1 month postpartum and whose abundance pre-vaccination were predictive of vaccine-induced pertussis and rotavirus antibody responses post 3 months of life. Collectively, HIV/ARV exposure disrupted the trajectory of innate and adaptive immunity from birth which may underlie relative vulnerability to infections in iHEU.

Disrupted memory T cell expansion in HIV-exposed uninfected infants is preceded by premature skewing of T cell receptor clonality

While preventing vertical HIV transmission has been very successful, the increasing number of HIV-exposed uninfected infants (iHEU) experience an elevated risk to infections compared to HIV-unexposed and uninfected infants (iHUU). Immune developmental differences between iHEU and iHUU remains poorly understood and here we present a longitudinal multimodal analysis of infant immune ontogeny that highlights the impact of HIV/ARV exposure. Using mass cytometry, we show alterations and differences in the emergence of NK cell populations and T cell memory differentiation between iHEU and iHUU. Specific NK cells observed at birth were also predictive of acellular pertussis and rotavirus vaccine-induced IgG and IgA responses, respectively, at 3 and 9 months of life. T cell receptor Vβ clonotypic diversity was significantly and persistently lower in iHEU preceding the expansion of T cell memory. Our findings show that HIV/ARV exposure disrupts innate and adaptive immunity from birth which may underlie relative vulnerability to infections.

Preterm Birth in Women With HIV: The Role of the Placenta

Maternal HIV infection is associated with an increased risk of preterm birth (PTB). However, the mechanisms underlying this increased risk in women with HIV remain poorly understood. In this regard, it is well-established that labor is an inflammatory process and premature activation of the pro-inflammatory signals (associated with labor) can result in preterm labor which can subsequently lead to PTB. HIV infection is known to cause severe immune dysregulation within its host characterized by altered immune profiles, chronic inflammation and eventually, the progressive failure of the immune system. The human placenta comprises different immune cell subsets, some of which play an important role during pregnancy including participating in the inflammatory processes that accompany labor. It is therefore plausible that HIV/antiretroviral therapy (ART)-associated immune dysregulation within the placental microenvironment may underlie the increased risk of PTB reported in women with HIV. Here, we review evidence from studies that point toward the placental origin of spontaneous PTB and discuss possible ways maternal HIV infection and/or ART could increase this risk. We focus on key cellular players in the maternal decidua including natural killer cells, CD4+ T cells including CD4+ regulatory T cells, CD8+ T cells as well as macrophages.

T cell Homeostatic Imbalance in Placentae from Women with HIV in the absence of Vertical Transmission

BACKGROUND

Implementation of universal antiretroviral therapy (ART) has significantly lowered vertical transmission rates but has also increased numbers of HIV-exposed uninfected children (HEU), who remain vulnerable to morbidities. Here, we investigated whether T cell alterations in the placenta contribute to altered immune status in HEU.

METHODS

We analyzed T cells from term placentae decidua and villous tissue and paired cord blood from pregnant women with HIV (PWH) who initiated ART late in pregnancy (n=21) with pregnant women not living with HIV (PWNH) (n=9).

RESULTS

Placentae from PWH showed inverted CD4:CD8 ratios and higher proportions of tissue resident CD8+ T cells in villous tissue relative to control placentae. CD8+ T cells in the fetal capillaries, which were of fetal origin, positively correlated with maternal plasma viraemia prior to ART initiation, implying that imbalanced T cells persisted throughout pregnancy. Additionally, the expanded memory differentiation of CD8+ T cells was confined to the fetal placental compartment and cord blood but was not observed in the maternal decidua.

CONCLUSIONS

T cell homeostatic imbalance in the blood circulation of PWH is reflected in the placenta. The placenta may be a causal link between HIV-induced maternal immune changes during gestation and altered immunity in newborn infants in the absence of vertical transmission.

Altered Intestinal Permeability and Fungal Translocation in Ugandan Children With Human Immunodeficiency Virus

BACKGROUND

Children with perinatally acquired human immunodeficiency virus (HIV; PHIVs) face a lifelong cumulative exposure to HIV and antiretroviral therapy (ART). The relationship between gut integrity, microbial translocation, and inflammation in PHIV is poorly understood.

METHODS

This is a cross-sectional study in 57 PHIVs, 59 HIV-exposed but uninfected children, and 56 HIV-unexposed and -uninfected children aged 2-10 years old in Uganda. PHIVs were on stable ART with HIV-1 RNA <400 copies/mL. We measured markers of systemic inflammation, monocyte activation, and gut integrity. Kruskal-Wallis tests were used to compare markers by group and the Spearman correlation was used to assess correlations between biomarkers.

RESULTS

The mean age of all participants was 7 years and 55% were girls. Among PHIVs, the mean CD4 % was 34%, 93% had a viral load ≤20 copies/mL, and 79% were on a nonnucleoside reverse transcriptase inhibitor regimen. Soluble cluster of differentiation 14 (sCD14), beta-D-glucan (BDG), and zonulin were higher in the PHIV group (P ≤ .01). Intestinal fatty acid binding protein (I-FABP) and lipopolysaccharide binding protein (LBP) did not differ between groups (P > .05). Among PHIVs who were breastfed, levels of sCD163 and interleukin 6 (IL6) were higher than levels in PHIV who were not breastfed (P < .05). Additionally, in PHIVs with a history of breastfeeding, sCD14, BDG, LBP, zonulin, and I-FABP correlated with several markers of systemic inflammation, including high-sensitivity C-reactive protein, IL6, d-dimer, and systemic tumor necrosis factor receptors I and II (P ≤ .05).

CONCLUSIONS

Despite viral suppression, PHIVs have evidence of altered gut permeability and fungal translocation. Intestinal damage and the resultant bacterial and fungal translocations in PHIVs may play a role in the persistent inflammation that leads to many end-organ diseases in adults.Despite viral suppression, children with perinatally acquired human immunodeficiency virus (HIV) in Uganda have evidence of alterations in intestinal permeability and fungal translocation, compared to HIV-exposed but uninfected and HIV-unexposed children, which may play a role in HIV-associated chronic inflammation.

The University of Zimbabwe College of Health Sciences (UZ-CHS) BIRTH COHORT study: rationale, design and methods

BACKGROUND

Commencing lifelong antiretroviral therapy (ART) immediately following HIV diagnosis (Option B+), has greatly improved maternal-infant health. Thus, large and increasing numbers of HIV-infected women are on ART during pregnancy, a situation concurrently increasing numbers of HIV-exposed-uninfected (HEU) infants. Compared to their HIV-unexposed-uninfected (HUU) counterparts, HEU infants show higher rates of adverse birth outcomes, mortality, infectious/non-communicable diseases including impaired growth and neurocognitive development. There is an urgent need to understand the impact of HIV and early life ART exposures, immune-metabolic dysregulation, comorbidities and environmental confounders on adverse paediatric outcomes.

METHODS

Six hundred (600) HIV-infected and 600 HIV-uninfected pregnant women ≥20 weeks of gestation will be enrolled from four primary health centres in high density residential areas of Harare. Participants will be followed up as mother-infant-pairs at delivery, week(s) 1, 6, 10, 14, 24, 36, 48, 72 and 96 after birth. Clinical, socio-economic, nutritional and environmental data will be assessed for adverse birth outcomes, impaired growth, immune/neurodevelopment, vertical transmission of HIV, hepatitis-B/C viruses, cytomegalovirus and syphilis. Maternal urine, stool, plasma, cord blood, amniotic fluid, placenta and milk including infant plasma, dried blood spot and stool will be collected at enrolment and follow-up visits. The composite primary endpoint is stillbirth and infant mortality within the first two years of life in HEU versus HUU infants. Maternal mortality in HIV-infected versus -uninfected women is another primary outcome. Secondary endpoints include a range of maternal and infant outcomes. Sub-studies will address maternal stress and malnutrition, maternal-infant latent tuberculosis, Helicobacter pylori infections, immune-metabolomic dysregulation including gut, breast milk and amniotic fluid dysbiosis.

DISCUSSION

The University of Zimbabwe-College of Health-Sciences-Birth-Cohort study will provide a comprehensive assessment of risk factors and biomarkers for HEU infants' adverse outcomes. This will ultimately help developing strategies to mitigate effects of maternal HIV, early-life ART exposures and comorbidities on infants' mortality and morbidity.

TRIAL REGISTRATION

ClinicalTrial.gov Identifier: NCT04087239 . Registered 12 September 2019.

Rates of Hospitalization and Infection-Related Hospitalization Among Human Immunodeficiency Virus (HIV)-Exposed Uninfected Children Compared to HIV-Unexposed Uninfected Children in the United States, 2007-2016

BACKGROUND

Studies from multiple countries have suggested impaired immunity in perinatally human immunodeficiency virus (HIV)-exposed uninfected children (HEU), with elevated rates of all-cause hospitalization and infections. We estimated and compared the incidence of all-cause hospitalization and infection-related hospitalization in the first 2 years of life among HEU and HIV-unexposed uninfected children (HUU) in the United States. Among HEU, we evaluated associations of maternal HIV disease-related factors during pregnancy with risk of child hospitalization.

METHODS

HEU data from subjects enrolled in the Surveillance Monitoring for Antiretroviral Therapy Toxicities Study (SMARTT) cohort who were born during 2006-2017 were analyzed. HUU comparison data were obtained from the Medicaid Analytic Extract database, restricted to states participating in SMARTT. We compared rates of first hospitalization, total hospitalizations, first infection-related hospitalization, total infection-related hospitalizations, and mortality between HEU and HUU using Poisson regression. Among HEU, multivariable Poisson regression models were fitted to evaluate associations of maternal HIV factors with risk of hospitalization.

RESULTS

A total of 2404 HEU and 3 605 864 HUU were included in the analysis. HEU children had approximately 2 times greater rates of first hospitalization, total hospitalizations, first infection-related hospitalization, and total infection-related hospitalizations compared with HUUs. There was no significant difference in mortality. Maternal HIV disease factors were not associated with the risk of child infection or hospitalization.

CONCLUSIONS

Compared with HUU, HEU children in the United States have higher rates of hospitalization and infection-related hospitalization in the first 2 years of life, consistent with studies in other countries. Closer monitoring of HEU infants for infection and further elucidation of immune mechanisms is needed.

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.

S100A14 Is Increased in Activated NK Cells and Plasma of HIV-Exposed Seronegative People Who Inject Drugs and Promotes Monocyte-NK Crosstalk

BACKGROUND

HIV-exposed seronegative people who inject drugs (HESN-PWID) have been shown to have increased natural killer (NK) cell and myeloid activation when compared with control donors.

METHODS

We investigated potential mechanisms maintaining NK activation by conducting quantitative proteome comparisons of NK cells from HESN-PWID subjects and control donors. Proteins upregulated in NK cells were measured in the plasma of HESN-PWID subjects by ELISA and further investigated for their ability to induce innate immune activation in vitro.

RESULTS

The NK cell proteome comparison showed markedly higher levels of interferon-stimulated proteins and S100 proteins, including S100A14. Consistent with these results, we observed significantly higher levels of S100A14 in the plasma of HESN-PWID subjects compared with controls (P = 0.033, n = 25). In vitro, the addition of recombinant S100A14 protein significantly activated NK cells in a peripheral blood mononuclear cell mixture (P = 0.011, n = 9), but not purified NK cells alone. Treatment of purified monocytes with recombinant S100A14 protein induced secretion of TNF-alpha and led to significantly higher NK CD69 activation (P = 0.0156, n = 7) in a co-culture through a TLR4-dependent interaction.

CONCLUSIONS

Our study identified S100A14 as a novel protein increased within NK cells and plasma of HESN-PWID subjects with the capacity to sustain NK activation through TLR4-dependent activation of myeloid cells.

Potential Role of Regulatory T Cells in Mother-to-Child Transmission of HIV

Background:

Mother-to-child transmission of HIV-1 occurs in a minority of HIV-infected mother-infant pairs, even without any interventions. The mechanisms that protect the majority of HIV-exposed infants from infection are unclear. T regulatory cells (Treg) have important immunomodulato-ry functions, but their role in the fetus as well as in mother-to-child transmission of HIV is under-studied.

Methods:

We studied available cryopreserved peripheral blood mononuclear cells from HIV-exposed infants from the Breastfeeding, Antiretrovirals and Nutrition (BAN) Study cohort in Malawi: 64 in-fants were HIV-uninfected and 28 infants were HIV-infected at birth. We quantified the frequency of Treg cells (CD4+CD25+FoxP3+), and activated CD4+ and CD8+ T cells (CD38+ HLADR+) by flow cytometry at birth, 6 weeks and 6, 9 and 12 months of age. Descriptive statistics were performed to describe the distributions of these lymphocyte markers according to the HIV infection status; and Student’s t tests and Wilcoxon-Rank Sum tests were performed to compare HIV- infected and unin-fected infants.

Results:

T cell activation increased rapidly in the first 6 weeks of life, more pronounced on CD8+ T cells; a further increase in activation was observed at the time of weaning from breastfeeding at 6 months of age. In contrast, the frequency of Treg was stable over the first 6 weeks of life (median, 0.5%), slightly decreased between 6 weeks and 6 months (median at 6 months, 0.3%) and then slight-ly increased between 6 months (time of weaning) and 12 months of age (median, 0.45%). HIV-infected infants had significantly higher frequencies of activated T cells than uninfected infants (P < 0.01). At the time of birth, HIV-exposed uninfected infants had higher levels of Treg, compared to in-fants infected in utero, even though this did not reach statistical significance in this small sample size (P = 0.08).

Conclusion:

This study provides initial evidence that Treg may play a role in preventing mother-to-child transmission of HIV, likely by suppressing immune activation in the fetus and infant, and needs to be substantiated in a larger study. Better characterization of the role of Treg in fetal and neonatal immunity may provide a valuable complementary approach to achieve eradication of mother-to-child transmission of HIV.

HIV-exposed-uninfected infants have increased inflammation and monocyte activation

BACKGROUND

HIV-exposed-uninfected (HEU) infants have increased infectious morbidity and mortality; little is known about their levels of inflammation and monocyte activation.

METHODS

Plasma samples obtained at birth and 6 months from 86 HEU mother-infant pairs enrolled in the National Institute of Child Health and Human Development cohorts in Brazil were compared with 88 HIV-unexposed mother-infant pairs. HIV-infected mothers received antiretroviral therapy during pregnancy, their infants received zidovudine prophylaxis and were not breastfed. IL-6, soluble TNFα receptor I (sTNF-RI) and II, soluble CD14, soluble CD163, IFN-γ-induced protein 10 (IP-10), vascular cell adhesion molecule, oxidized LDL, D-dimer and high-sensitivity C-reactive protein were assayed by ELISA at birth and at 6 months. sTNF-RI and IL-6 were considered coprimary endpoints.

RESULTS

Among HIV-infected mothers, 79% had HIV-RNA less than 400 copies/ml prior to delivery. Compared with HIV-unexposed, HEU infants had a lower mean gestational age (38.7 vs. 39.3 weeks) and weight (3.1 vs. 3.3 kg); and reached lower weight (5.9 vs. 8.5 kg) and height (53.6 vs. 68.8 cm) at 6 months. With the exception of vascular cell adhesion molecule, inflammatory markers were generally higher (P ≤ 0.005) in HEU at birth, but at 6 months only sTNF-RI and IL-6 remained higher. For HEU pairs, only IP-10 was associated with maternal levels at birth (P < 0.001). In HEU, elevated levels of high-sensitivity C-reactive protein and IP-10 at birth were associated with lower weight at birth (P = 0.04) and at 6 months (P = 0.04).

CONCLUSION

HIV-exposed infants have heightened inflammation and monocyte activation at birth, which for some markers persisted to 6 months of life and was not related to maternal inflammatory status. Inflammation may contribute to the increased HEU infectious morbidity and poor growth.

HIV-Exposed Uninfected Infants Have Increased Regulatory T Cells That Correlate With Decreased T Cell Function

Background: HIV-exposed uninfected infants (HEU) are at higher risk of severe infections, hospitalizations and death compared with HIV-unexposed uninfected infants (HUU), but the immune deficit underlying it is not known. To address this gap, we investigated T cell functionality and its relationship to phenotypic profiles of T cells and antigen presenting cells (APC) in HEU and HUU.

Methods: Blood mononuclear cells from 55 HEU and 16 HUU were stimulated with Staphylococcal Enterotoxin B (SEB) or mock for 72 h, and tested by flow cytometry for proliferation and expression of Th1, Th2, and regulatory (Treg) markers. In parallel, cells were phenotypically assessed for differentiation profiles of Treg, conventional T cell (Tconv) and APC in unstimulated cells.

Results: HEU had lower CD4+ functional responses to SEB/mock and similar CD8+ responses compared with HUU. In the phenotypic T cell panel, HEU showed higher proportions of CD4+ and CD8+ Treg expressing IL10, FOXP3, and CD25; higher effector Tconv and Treg; and lower naïve and CD4+TGFβ+ Treg compared with HUU. In the phenotypic APC panel, HEU showed higher proportions of CD1c+ cDC2, CD123+ pDC, CD16+ inflammatory monocytes and cDC and higher expression of CD103 on CD1c-CD123-CD16-cDC1 compared with HUU. Regression analyses adjusted for HIV exposure and multiple comparisons showed that higher CD8+IL10+ and CD8+FOXP3+ Treg in unstimulated cells were associated with lower CD8+ T cell functional responses to SEB/mock. Functionality was not affected by Tconv differentiation, but higher APC activation in aggregate was associated with higher CD8+IL10+ Treg responses to SEB.

Conclusions: T cell functionality was decreased in HEU compared with HUU. High CD8+ Treg proportions were the most important predictors of decreased T cell functionality in HEU and HUU.

Impact of maternal HIV exposure, feeding status, and microbiome on infant cellular immunity

At least one-third of infants born in sub-Saharan Africa have been exposed to the effects of maternal HIV infection and antiretroviral treatment. Intrauterine HIV exposure is associated with increased rates of morbidity and mortality in children. Although the mechanisms responsible for poor infant health with HIV-1 exposure are likely to be multifactorial, we posit that the maternal environment during gestation and in the perinatal period results in altered infant immunity and is possibly the strongest contributing factor responsible for the disproportionally high infectious events among HIV-exposed infants who remain HIV uninfected. This review provides a synthesis of studies reporting the impact of intrauterine HIV exposure, feeding practices, and microbiota on immune ontogeny in the first year of life in HIV-exposed uninfected infants.

Beyond Passive Immunity: Is There Priming of the Fetal Immune System Following Vaccination in Pregnancy and What Are the Potential Clinical Implications?

Infection is responsible for over half a million neonatal deaths worldwide every year, and vaccination in pregnancy is becoming increasingly recognized as an important strategy for the protection of young infants. Increasing evidence suggests that exposure to maternal infection in utero may "prime" the developing immune system, even in the absence of infant infection. It is also possible that in utero priming may occur following maternal vaccination, with antigen-specific cellular immune responses detectable in utero and at birth. However, this remains a topic of some controversy. This review focuses on the evidence for in utero priming and the clinical implications for vaccination in pregnancy, considering whether in utero priming following vaccination could provide protection independent of antibody-mediated passive immunity, the possible effects of vaccination on subsequent infant vaccinations, their potential "non-specific" effects, and how the design and timing of vaccination might affect prenatal priming. Looking forward, we describe other possible options for quantifying antigen-specific cellular responses, including MHC tetramers, novel proliferation and cytokine-based assays, and animal models. Together, these may help us address future research questions and establish more robust evidence of fetal immune system priming.

B and T Cell Phenotypic Profiles of African HIV-Infected and HIV-Exposed Uninfected Infants: Associations with Antibody Responses to the Pentavalent Rotavirus Vaccine

We examined associations between B and T cell phenotypic profiles and antibody responses to the pentavalent rotavirus vaccine (RV5) in perinatally HIV-infected (PHIV) infants on antiretroviral therapy and in HIV-exposed uninfected (PHEU) infants enrolled in International Maternal Pediatric Adolescent AIDS Clinical Trials P1072 study (NCT00880698). Of 17 B and T cell subsets analyzed, PHIV and PHEU differed only in the number of CD4+ T cells and frequency of naive B cells, which were higher in PHEU than in PHIV. In contrast, the B and T cell phenotypic profiles of PHIV and PHEU markedly differed from those of geographically matched contemporary HIV-unexposed infants. The frequency of regulatory T and B cells (Treg, Breg) of PHIV and PHEU displayed two patterns of associations: FOXP3+ CD25+ Treg positively correlated with CD4+ T cell numbers; while TGFβ+ Treg and IL10+ Treg and Breg positively correlated with the frequencies of inflammatory and activated T cells. Moreover, the frequencies of activated and inflammatory T cells of PHIV and PHEU positively correlated with the frequency of immature B cells. Correlations were not affected by HIV status and persisted over time. PHIV and PHEU antibody responses to RV5 positively correlated with CD4+ T cell counts and negatively with the proportion of immature B cells, similarly to what has been previously described in chronic HIV infection. Unique to PHIV and PHEU, anti-RV5 antibodies positively correlated with CD4+/CD8+FOXP3+CD25+% and negatively with CD4+IL10+% Tregs. In conclusion, PHEU shared with PHIV abnormal B and T cell phenotypic profiles. PHIV and PHEU antibody responses to RV5 were modulated by typical HIV-associated immune response modifiers except for the association between CD4+/CD8+FOXP3+CD25+Treg and increased antibody production.

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.

Immune development in HIV-exposed uninfected children born to HIV-infected women

Immunological and clinical findings suggestive of some immune dysfunction have been reported among HIV-exposed uninfected (HEU) children and adolescents. Whether these defects are persistent or transitory is still unknown. HEU pediatric population at birth, 12 months, 6-12 years were evaluated in comparison to healthy age-matched HIV-unexposed controls. Plasma levels of LPS, sCD14, cytokines, lymphocyte immunophenotyping and T-cell receptor excision circles (TREC) were assessed. HEU and controls had similar LPS levels, which remained low from birth to 6-12 years; for plasma sCD14, IL-2, IL-6, IL-7, IL-10, IL-12p70, IL-13, IL-17, IFN-γ, TNF-α, G-CSF, GM-CSF and MCP-1, which increased from birth to 12 months and then decreased at 6-12 years; and for TREC/10⁶ PBMC at birth in HEU and controls. By contrast, plasma MIP-1β levels were lower in HEU than in controls (p=0.009) at 12 months, and IL-4 levels were higher in HEU than controls (p=0.04) at 6-12 years. Immune activation was higher in HEU at 12 months and at 6-12 years than controls based on frequencies of CD38+HLA-DR+CD8+T cells (p=0.05) and of CD38+HLA-DR+CD4+T cells (p=0.006). Resting memory and activated mature B cells increased from birth to 6-12 years in both groups. The development of the immune system in vertically HEU individuals is comparable to the general population in most parameters, but subtle or transient differences exist. Their role in influencing clinical incidences in HEU is unknown.

Altered Natural Killer Cell Function in HIV-Exposed Uninfected Infants

Objectives

HIV-exposed uninfected (HEU) infants have higher rates of severe and fatal infections compared with HIV-unexposed (HUU) infants, likely due to immune perturbations. We hypothesized that alterations in natural killer (NK) cell activity might occur in HEU infants and predispose them to severe infections.

Design

Case–control study using cryopreserved peripheral blood mononuclear cells (PBMCs) at birth and 6 months from HEU infants enrolled from 2002 to 2009 and HUU infants enrolled from 2011 to 2013.

Methods

NK cell phenotype and function were assessed by flow cytometry after 20-h incubation with and without K562 cells.

Results

The proportion of NK cells among PBMCs was lower at birth in 12 HEU vs. 22 HUU (1.68 vs. 10.30%, p < 0.0001) and at 6 months in 52 HEU vs. 72 HUU (3.09 vs. 4.65%, p = 0.0005). At birth, HEU NK cells demonstrated increased killing of K562 target cells (p < 0.0001) and increased expression of CD107a (21.65 vs. 12.70%, p = 0.047), but these differences resolved by 6 months. Stimulated HEU NK cells produced less interferon (IFN)γ at birth (0.77 vs. 2.64%, p = 0.008) and at 6 months (4.12 vs. 8.39%, p = 0.001), and showed reduced perforin staining at 6 months (66.95 vs. 77.30%, p = 0.0008). Analysis of cell culture supernatants indicated that lower NK cell activity in HEU was associated with reduced interleukin (IL)-12, IL-15, and IL-18. Addition of recombinant human IL-12 to stimulated HEU PBMCs restored IFNγ production to that seen in stimulated HUU cultures.

Conclusion

NK cell proportion, phenotype, and function are altered in HEU infants. NK cell cytotoxicity and degranulation are increased in HEU at birth, but HEU NK cells have reduced IFNγ and perforin production, suggesting an adequate initial response, but decreased functional reserve. NK cell function improved with addition of exogenous IL-12, implicating impaired production of IL-12 by accessory cells. Alterations in NK cell and accessory cell function may contribute to the increased susceptibility to infection in HEU infants.

Excess respiratory viral infections and low antibody responses among HIV-exposed, uninfected infants

OBJECTIVE

HIV-exposed uninfected (HEUs) infants have frequent severe infection, hospitalization, and death. We performed a serologic investigation to determine the role of common childhood respiratory pathogens in the excess incidence of infections in HEUs.

DESIGN

Prospective cohort study of mother-infant pairs.

METHODS

Among 247 HEUs and 88 HIV-unexposed uninfected (HUU) infant-mother pairs, we measured maternal antibodies to respiratory syncytial virus (RSV) and pneumococcus (PNC 1, 5, 6B, 14); infant antibodies to RSV, influenza A (flu), parainfluenza viruses (1, 2, 3), and PNC 1, 5, 6B, and 14 were measured at 0 and 6 months, and antitetanus antibodies at 6 months.

RESULTS

HIV-infected mothers had higher RSV and lower PNC antibody concentrations at delivery than uninfected mothers. Transplacental transfer of maternal antibodies, particularly for RSV, was lower in HEUs compared with HUUs. At birth, HEUs had higher concentrations of anti-RSV antibodies than HUUs, but lower antibodies to the other respiratory agents. At 6 months, HEUs had significantly higher proportions of seroconversions and higher antibody concentrations against parainfluenza viruses 1, 2, and 3. There were no significant differences in seroconversions to flu and RSV, but antibody concentrations to RSV were six-fold lower in HEUs versus HUUs at 6 months. Antibody responses to at least two doses of tetanus vaccine were also six-fold lower in HEUs compared with HUUs.

CONCLUSION

Six-month-old HEUs had a higher incidence of respiratory viral infections than HUUs. In addition to the low passive protection from maternal antibodies, low antibody responses of HEUs may contribute to increased morbidity and mortality.

Ontogeny of CD4+ T Lymphocytes With Phenotypic Susceptibility to HIV-1 During Exclusive and Nonexclusive Breastfeeding in HIV-1-Exposed Ugandan Infants

Background

Among infants exposed to human immunodeficiency virus (HIV) type 1, mixed breastfeeding is associated with higher postnatal HIV-1 transmission than exclusive breastfeeding, but the mechanisms of this differential risk are uncertain.

Methods

HIV-1-exposed Ugandan infants were prospectively assessed during the first year of life for feeding practices and T-cell maturation, intestinal homing (β7hi), activation, and HIV-1 coreceptor (CCR5) expression in peripheral blood. Infants receiving only breast milk and those with introduction of other foods before 6 months were categorized as exclusive and nonexclusive, respectively.

Results

Among CD4+ and CD8+ T cells, the expression of memory, activation, and CCR5 markers increased rapidly from birth to week 2, peaking at week 6, whereas cells expressing the intestinal homing marker increased steadily in the central memory (CM) and effector memory T cells over 48 weeks. At 24 weeks, when feeding practices had diverged, nonexclusively breastfed infants showed increased frequencies and absolute counts of β7hi CM CD4+ and CD8+ T cells, including the HIV-1-targeted cells with CD4+β7hi/CCR5+ coexpression, as well as increased activation.

Conclusions

The T-cell phenotype associated with susceptibility to HIV-1 infection (CCR5+, gut-homing, CM CD4+ T cells) was preferentially expressed in nonexclusively breastfed infants, a group of infants at increased risk for HIV-1 acquisition.

Maternal human immunodeficiency virus status and morbidity and mortality in very low birthweight infants

BACKGROUND

Human immunodeficiency virus (HIV) remains a common cause of infection in pregnant women. The effect of HIV exposure on growth, morbidity and mortality in very low-birthweight infants (VLBWI) is under-reported.

AIM

To determine anthropometry at birth, morbidity during hospital stay and mortality at hospital discharge of VLBWI stratified according to HIV-exposure in a tertiary public government hospital in Johannesburg, South Africa.

METHODS

Retrospective descriptive study. Records of VLBWI were reviewed for maternal HIV status, infant characteristics, diagnosis and outcome to hospital discharge. Anthropometry, morbidity and mortality were compared according to HIV-exposure.

RESULTS

Of 302 VLBWI,103 (34.1%)were HIV-exposed. Among the 103mothers, 38 (36.9%)were on combined anti-retroviral therapy (cART), 41 (39.8%) were on zidovudine (AZT) and 24 (23%) were not on either. More HIV-exposed VLBWI weighed v1000 g (41.2 vs 23.1%, Pv0.01). There were no differences in incidence or number of episodes of sepsis between HIV-exposed and -unexposed. More HIV-exposed VLBWI had severe intraventricular haemorrhage (IVH) (57.1 vs 11.4%, Pv0.01). The overall mortality rate was 27%, with HIV-exposed VLBWI having a mortality rate of 38.6% compared with 21% of the HIV-unexposed (Pv0.01). On multivariate analysis, the predictor of mortality was birthweight (Pv0.01).

CONCLUSION

HIV-exposed VLBWI are more likely to have extremely low birthweights. Morbidity in VLBWI is not affected by HIV-exposure, except for severe IVH. Birthweight is a predictor of mortality in VLBWI, irrespective of maternal HIV status.

Maternal HIV infection alters the immune balance in the mother and fetus; implications for pregnancy outcome and infant health

PURPOSE OF REVIEW

With the rapid roll-out of combination antiretroviral therapy to prevent mother-to-child transmission of HIV, there is an annual increase in the number of uninfected infants born to HIV-infected women. Although the introduction of combination antiretroviral therapy has vastly improved pregnancy outcome and the health of infants born to HIV-infected women, concerns remain regarding the impact the maternal HIV infection on the pregnancy outcome and the health of HIV-exposed uninfected infants.

RECENT FINDINGS

Maternal HIV infection is associated with negative pregnancy outcomes such as low birth weight. In addition, an increased susceptibility to infections is reported in HIV-exposed uninfected infants compared with infants born to uninfected women. Studies have shown that HIV-exposure affects the maternal/fetal unit, with increase of proinflammatory cytokine produced by placental cells, as well as altered infant immune responses. These changes could provide the underlying conditions for negative pregnancy outcomes and facilitate mother-to-child transmission of HIV in the infant. Further studies are required to understand the underlying mechanisms and investigate whether these altered infant immune responses persist and have clinical consequences beyond childhood.

SUMMARY

HIV infection in pregnant women is associated with altered immune responses in HIV-infected women and their offspring with clinical consequences for pregnancy outcome and the HIV-exposed uninfected infant. Further studies are required to address the origin and long-term consequences of prenatal HIV-exposure and subsequent immune activation for infant health.

A meta-analysis assessing all-cause mortality in HIV-exposed uninfected compared with HIV-unexposed uninfected infants and children

OBJECTIVE

Conduct a meta-analysis examining differential all-cause mortality rates between HIV-exposed uninfected (HEU) infants and children as compared with their HIV-unexposed uninfected (HUU) counterparts.

DESIGN

Meta-analysis summarizing the difference in mortality between HEU and HUU infants and children. Reviewed studies comparing children in the two groups for all-cause mortality, in any setting, from 1994 to 2016 from six databases.

METHODS

Meta-analyses were done estimating overall mortality comparing the two groups, stratified by duration of follow-up time from birth (0-12, 12-24 and >24 months) and by year enrollment ended in each study: less than 2002 compared with at least 2002, when single-dose nevirapine for prevention of mother-to-child transmission (PMTCT) commenced in low-income and middle-income countries.

RESULTS

Included 22 studies, for a total of 29 212 study participants [n = 8840 (30.3%) HEU; n = 20 372 (37.7%) HUU]. Random effects models showed HEU had a more than 70% increased risk of mortality vs. HUU. Stratifying by age showed that HEU vs. HUU had a significant 60-70% increased risk of death at every age strata. There was a significant 70% increase in the risk of mortality between groups before the implementation of PMTCT, which remained after 2002 [risk ratio: 1.46; 95% confidence interval (CI): 1.14-1.87], when the availability of PMTCT services was widespread, suggesting that prenatal antiretroviral therapy, and healthier mothers, does not fully eliminate this increased risk in mortality.

CONCLUSION

We show a consistent increase risk of mortality for HEU vs. HUU infants and children. Longitudinal research is needed to elucidate underlying mechanisms, such as maternal and infant health status and breast feeding practices, which may help explain these differences in mortality.

Linking Susceptibility to Infectious Diseases to Immune System Abnormalities among HIV-Exposed Uninfected Infants

HIV-exposed uninfected (HEU) infants experience increased overall mortality from infectious causes when compared to HIV-unexposed uninfected (HU) infants. This is the case in both the resource-rich and resource-limited settings. Here, we explore the concept that specific types of infectious diseases that are more common among HEU infants could provide clues as to the potential underlying immunological abnormalities. The most commonly reported infections in HEU vs. HU infants are caused by encapsulated bacteria, suggesting the existence of a less effective humoral (antibody, complement) immune response. Decreased transplacental transfer of protective maternal antibodies has consistently been observed among HEU newborns, suggesting that this may indeed be one of the key drivers of their susceptibility to infections with encapsulated bacteria. Reassuringly, HEU humoral response to vaccination appears to be well conserved. While there appears to be an increase in overall incidence of acute viral infections, no specific pattern of acute viral infections has emerged; and although there is evidence of increased chronic viral infection from perinatal transmission of hepatitis C and cytomegalovirus, no data exist to suggest an increase in adverse outcomes. Thus, no firm conclusions about antiviral effector mechanisms can be drawn. However, the most unusual of reported infections among the HEU have been opportunistic infections, suggesting the possibility of underlying defects in CD4 helper T cells and overall immune regulatory function. This may relate to the observation that the immunological profile of HEUs indicates a more activated T cell profile as well as a more inflammatory innate immune response. However, both of these observations appear transient, marked in early infancy, but no longer evident later in life. The causes of these early-life changes in immune profiles are likely multifactorial and may be related to in utero exposure to HIV, but also to increased environmental exposure to pathogens from sicker household contacts, in utero and postnatal antiretroviral drug exposure, and, in certain circumstances, differences in mode of feeding. The relative importance of each of these factors will be important to delineate in an attempt to identify those HEU at highest risk of adverse outcomes for targeted interventions.

Impact of HIV-1 infection on the feto-maternal crosstalk and consequences for pregnancy outcome and infant health

Adaptation of the maternal immune system to establish maternal/fetal equilibrium is required for a successful pregnancy. Viral infections, including HIV-1 infection, can alter this maternal/fetal equilibrium, with significant consequences for pregnancy outcome, including miscarriages, impaired fetal growth, and premature delivery. Furthermore, maternal HIV-1 infection has been shown to have a long-term impact on the developing fetal immune system also when the infant is not infected with the virus. In this review, we discuss the consequences of maternal HIV-1 infection and antiretroviral therapy on pregnancy outcome and the health of the uninfected HIV-1-exposed infant.

HIV-Exposed Uninfected Infants in Zimbabwe: Insights into Health Outcomes in the Pre-Antiretroviral Therapy Era

The ZVITAMBO trial recruited 14,110 mother-infant pairs to a randomized controlled trial of vitamin A between 1997 and 2000, before the availability of antiretroviral therapy for HIV prophylaxis or treatment in Zimbabwe. The HIV status of mothers and infants was well characterized through 1-2 years of follow-up, leading to the largest cohort to date of HIV-exposed uninfected (HEU) infants (n = 3135), with a suitable comparison group of HIV-unexposed infants (n = 9510). Here, we draw on 10 years of published findings from the ZVITAMBO trial. HEU infants had increased morbidity compared to HIV-unexposed infants, with 50% more hospitalizations in the neonatal period and 30% more sick clinic visits during infancy, particularly for skin infections, lower respiratory tract infections, and oral thrush. HEU children had 3.9-fold and 2.0-fold higher mortality than HIV-unexposed children during the first and second years of life, respectively, most commonly due to acute respiratory infections, diarrhea/dysentery, malnutrition, sepsis, and meningitis. Infant morbidity and mortality were strongly related to maternal HIV disease severity, and increased morbidity remained until maternal CD4 counts were >800 cells/μL. HEU infants were more likely to be premature and small-for-gestational age than HIV-unexposed infants, and had more postnatal growth failure. Here, we propose a conceptual framework to explain the increased risk of infectious morbidity, mortality, and growth failure among HEU infants, hypothesizing that immune activation and inflammation are key drivers of both infection susceptibility and growth failure. Future studies should further dissect the causes of infection susceptibility and growth failure and determine the impact of ART and cotrimoxazole on outcomes of this vulnerable group of infants in the current era.

Delayed acquisition of Plasmodium falciparum antigen-specific CD4(+) T cell responses in HIV-exposed uninfected Malawian children receiving daily cotrimoxazole prophylaxis

Background

Cotrimoxazole (CTX) prophylaxis, recommended in HIV-exposed uninfected (HEU) children primarily against HIV-related opportunistic infections, has been shown to have some efficacy against Plasmodium falciparum malaria. The effects of CTX prophylaxis on the acquisition of P. falciparum antigen specific CD4⁺ T cells-mediated immunity in HEU children is still not fully understood.

Methods

Peripheral blood was collected from HEU and HIV-unexposed uninfected (HUU) children at 6, 12 and 18 months of age. Proportion of CD4⁺ T cells subsets were determined by immunophenotyping. P. falciparum antigen-specific CD4⁺ T cells responses were measured by intracellular cytokine staining assay.

Results

There were no differences in the proportions of naïve, effector and memory CD4⁺ T cell subsets between HEU and HUU children at all ages. There was a trend showing acquisition of P. falciparum-specific IFN-γ and TNF-producing CD4⁺ T cells with age in both HUU and HEU children. There was, however, lower frequency of P. falciparum-specific IFN-γ-producing CD4⁺ T cells in HEU compared to HUU at 6 and 12 months, which normalized 6 months after stopping CTX prophylaxis.

Conclusion

The results demonstrate that there is delayed acquisition of P. falciparum-specific IFN-γ-producing CD4⁺ T cells in HEU children on daily cotrimoxazole prophylaxis, which is evident at 6 and 12 months of age in comparison to HUU age-matched controls. However, whether this delayed acquisition of P. falciparum-specific IFN-γ-producing CD4⁺ T cells leads to higher risk to malaria disease remains unknown and warrants further investigation.

HIV-exposed, uninfected infants: new global challenges in the era of paediatric HIV elimination

The number of infants infected with HIV is declining with the rise in interventions for the elimination of paediatric HIV infection, but the number of uninfected infants exposed to HIV through their HIV-infected mothers is increasing. Interest in the health outcomes of HIV-exposed, uninfected infants has grown in the past decade, with several studies suggesting that these infants have increased mortality rates, increased infectious morbidity, and impaired growth compared with HIV-unexposed infants. However, heterogeneous results might reflect the inherent challenges in studies of HIV-exposed, uninfected infants, which need large populations with appropriate, contemporaneous comparison groups and repeated HIV testing throughout the period of breastfeeding. We review the effects of HIV exposure on mortality, morbidity, and growth, discuss the immunological abnormalities identified so far, and provide an overview of interventions that could be effective in this susceptible population. As the number of infants infected with HIV declines, the health needs of HIV-exposed, uninfected infants should be prioritised further, to ensure that post-2015 Sustainable Development Goals are achieved.

Altered Memory T-Cell Responses to Bacillus Calmette-Guerin and Tetanus Toxoid Vaccination and Altered Cytokine Responses to Polyclonal Stimulation in HIV-Exposed Uninfected Kenyan Infants

Implementation of successful prevention of mother-to-child transmission of HIV strategies has resulted in an increased population of HIV-exposed uninfected (HEU) infants. HEU infants have higher rates of morbidity and mortality than HIV-unexposed (HU) infants. Numerous factors may contribute to poor health in HEU infants including immunological alterations. The present study assessed T-cell phenotype and function in HEU infants with a focus on memory Th1 responses to vaccination. We compared cross-sectionally selected parameters at 3 and 12 months of age in HIV-exposed (n = 42) and HU (n = 28) Kenyan infants. We measured ex vivo activated and bulk memory CD4 and CD8 T-cells and regulatory T-cells by flow cytometry. In addition, we measured the magnitude, quality and memory phenotype of antigen-specific T-cell responses to Bacillus Calmette-Guerin and Tetanus Toxoid vaccine antigens, and the magnitude and quality of the T cell response following polyclonal stimulation with staphylococcal enterotoxin B. Finally, the influence of maternal disease markers on the immunological parameters measured was assessed in HEU infants. Few perturbations were detected in ex vivo T-cell subsets, though amongst HEU infants maternal HIV viral load positively correlated with CD8 T cell immune activation at 12 months. Conversely, we observed age-dependent differences in the magnitude and polyfunctionality of IL-2 and TNF-α responses to vaccine antigens particularly in Th1 cells. These changes mirrored those seen following polyclonal stimulation, where at 3 months, cytokine responses were higher in HEU infants compared to HU infants, and at 12 months, HEU infant cytokine responses were consistently lower than those seen in HU infants. Finally, reduced effector memory Th1 responses to vaccine antigens were observed in HEU infants at 3 and 12 months and higher central memory Th1 responses to M. tuberculosis antigens were observed at 3 months only. Long-term monitoring of vaccine efficacy and T-cell immunity in this vulnerable population is warranted.

Proportions of CD4+, CD8+ and B cell subsets are not affected by exposure to HIV or to Cotrimoxazole prophylaxis in Malawian HIV-uninfected but exposed children

BACKGROUND

As a result of successful PMTCT programs, children born from HIV-infected mothers are now effectively protected from contracting the infection. However, it is not well known whether in utero exposure to the virus and the subsequent exposure to Cotrimoxazole (CTX) prophylaxis affect the cell mediated immune system of the children. This observational prospective study was aimed at determining how CD4(+) T, CD8(+) T and B cell subsets varied in HIV-exposed but uninfected (HEU) children at different ages.

METHODS

We recruited HEU and HIV-unexposed and uninfected (HUU) children from 6 months of age and followed them up until they were 18 months old. HEU children received daily CTX prophylaxis beginning at 6 weeks of age until when 12 months of age. Venous blood samples were collected 6 monthly and analysed for different subsets of CD8(+) T, B cells and totalCD4(+) T cells.

RESULTS

At 6 months of age, HEU children had a lower percentage of total CD4(+) T cells compared to HUU children and a lower proportion of naïve CD8(+) T cells but higher percentage of effector memory CD8(+) T cells compared to HUU children. HEU and HUU children had similar proportions of all B cell subsets at all ages.

CONCLUSIONS

The study showed that the subtle variations in CD4(+) and CD8(+) T cell subsets observed at 6 months do not last beyond 12 months of age, suggesting that HEU children have a robust cell-mediated immune system during first year of life.

TRIAL REGISTRATION

This article report is not based on results of a controlled health-care intervention.

Immunophenotypic profile and increased risk of hospital admission for infection in infants born to female kidney transplant recipients

Children born to female kidney recipients are exposed to immunosuppressive drugs during gestation. Little is known about their immune system at birth or in the long term. Twenty-eight children born to female kidney recipients and 40 full-term children born to healthy mothers were evaluated. T, B, NK, NKT, γδT cells were assessed by flow cytometry and functional evaluation of T and dendritic cells after in vitro activation was performed at birth and at 8 months of age. At birth, infants born to female kidney recipients showed lower numbers of CD4+ T, NKT and intense reduction of B cells (median cells/mm(3) , transplant: 153.7 X control: 512.4; p < 0.001). There was also a reduced percentage of activated CD8+ T and of CD4+ regulatory T cells. Activated memory and exhausted memory B cells showed higher percentages among children exposed to immunosuppressors when compared to control group. At 8 months, most immune alterations were no longer observed, but four children still had low numbers of some lymphocyte subsets at this age. Children born to female kidney recipients had 4.351 (95% CI: 1.026-15.225; p = 0.046) higher risk of hospital admission in the first months of life-some, with severe clinical manifestations-than those born to healthy women.

Changes in cellular immune activation and memory T-cell subsets in HIV-infected Zambian children receiving HAART

BACKGROUND

Increased exposure to a broad array of pathogens in children residing in sub-Saharan Africa may lead to heightened immune activation and increased proportions of memory T cells. Changes in the size of these cellular subsets have implications for restoration of normal immune function after treatment with highly active antiretroviral therapy (HAART) and are not well characterized in young sub-Saharan African children.

METHODS

CD4⁺ and CD8⁺ T-cell subsets were measured by flow cytometry in 157 HIV-infected Zambian children before and at 3-month intervals during HAART for up to 30 months and in 34 control children at a single study visit.

RESULTS

Before HAART, HIV-infected children had higher levels of activated and effector memory (EM) CD4⁺ and CD8⁺ T cells, and lower levels of naive T cells and CD8⁺ T cells expressing IL-7Rα, compared with control children. The median duration of follow-up was 14.9 months (interquartile range, 6.4-23.2) among 120 HIV-infected children with at least 1 study follow-up visit. Levels of immune activation and EM CD4⁺ T cells declined within 6 months of HAART, but the percentages of EM CD4 T cells and effector CD8⁺ T cells remained elevated through 30 months of HAART. IL-7Rα-expressing CD8⁺ T cells increased with HAART, suggesting expansion of memory capacity.

CONCLUSIONS

HAART significantly reduced levels of immune activation and EM CD4⁺ T cells, and promoted reconstitution of naive T cells and IL-7Rα-expressing CD8⁺ T cells. However, persistently high levels of EM CD4⁺ T cells in HIV-infected children may reflect chronic perturbations in T-cell subset composition.

Impact of elevated maternal HIV viral load at delivery on T-cell populations in HIV exposed uninfected infants in Mozambique

Background

HIV-uninfected infants born to HIV-infected mothers (HIV-exposed uninfected, HEU) have been described to have immune alterations as compared to unexposed infants. This study sought to characterize T-cell populations after birth in HEU infants and unexposed infants living in a semirural area in southern Mozambique.

Methods

Between August 2008 and June 2009 mother-infant pairs were enrolled at the Manhiça District Hospital at delivery into a prospective observational analysis of immunological and health outcomes in HEU infants. Infants were invited to return at one month of age for a clinical examination, HIV DNA-PCR, and immunophenotypic analyses. The primary analysis sought to assess immunological differences between HEU and unexposed groups, whereas the secondary analysis assessed the impact of maternal HIV RNA viral load in the HEU group. Infants who had a positive HIV DNA-PCR test were not included in the analysis.

Results

At one month of age, the 74 HEU and the 56 unexposed infants had similar median levels of naïve, memory and activated CD8 and CD4 T-cells. Infant naïve and activated CD8 T-cells were found to be associated with maternal HIV-RNA load at delivery. HEU infants born to women with HIV-RNA loads above 5 log₁₀ copies/mL had lower median levels of naïve CD8 T-cells (p = 0.04), and higher median levels of memory CD8 T-cells, (p = 0.014).

Conclusions

This study suggests that exposure to elevated maternal HIV-RNA puts the infant at higher risk of having early T-cell abnormalities. Improving prophylaxis of mother to child HIV programs such that more women have undetectable viral load is crucial to decrease vertical transmission of HIV, but may also be important to reduce the consequences of HIV virus exposure in HEU infants.

The impact of HIV exposure and maternal Mycobacterium tuberculosis infection on infant immune responses to bacille Calmette-Guérin vaccination

Objective:

The objective of this study is to assess the effect of maternal HIV and Mycobacterium tuberculosis (Mtb) infection on cellular responses to bacille Calmette-Guérin (BCG) immunization.

Design:

A mother–infant cohort study.

Methods:

Samples were collected from mother–infant pairs at delivery. Infants were BCG-vaccinated at 6 weeks of age and a repeat blood sample was collected from infants at 16 weeks of age. BCG-specific T-cell proliferation and intracellular cytokine expression were measured by flow cytometry. Secreted cytokines and chemokines in cell culture supernatants were analysed using a Multiplex assay.

Results:

One hundred and nine (47 HIV-exposed and 62 HIV-unexposed) mother–infants pairs were recruited after delivery and followed longitudinally. At birth, proportions of mycobacteria-specific proliferating T cells were not associated with either in-utero HIV exposure or maternal Mtb sensitization. However, in-utero HIV exposure affected infant-specific T-cell subsets [tumour necrosis factor-alpha (TNF-α) single positive proliferating CD4⁺ T cells and interferon-gamma (IFN-γ), TNF-α dual-positive CD4⁺ T cells]. Levels of TNF-α protein in cell culture supernatants were also significantly higher in HIV-exposed infants born to Mtb-sensitized mothers. In the presence of maternal Mtb sensitization, frequencies of maternal and newborn BCG-specific proliferating CD4⁺ T cells were positively correlated. Following BCG vaccination, there was no demonstrable effect of HIV exposure or maternal Mtb infection on infant BCG-specific T-cell proliferative responses or concentrations of secreted cytokines and chemokines.

Conclusion:

Effects of maternal HIV and Mtb infection on infant immune profiles at birth are transient only, and HIV-exposed, noninfected infants have the same potential to respond to and be protected by BCG vaccination as HIV-unexposed infants.

Impact of maternal HIV-1 viremia on lymphocyte subsets among HIV-exposed uninfected infants: protective mechanism or immunodeficiency

BACKGROUND

Reports of increased morbidity and mortality from infectious diseases among HIV Exposed Uninfected (HEU) infants have raised concern about a possible underlying immunodeficiency among them. The objective of this study was to assess the immunological profile of HEU infants born to mothers exhibiting different levels of HIV-1 viremia at the time of delivery.

METHODS

Study subjects were enrolled in the Centre maternel et infantile sur le SIDA (CMIS) mother-child cohort between 1997 and 2010 (n =585). Infant CD4+ T cell, CD8+ T cell and CD19+ B cell counts were assessed at 2 and 6 months of age, and compared among HEU infants in groups defined by maternal viral load (VL) at the time of delivery (VL < 50 copies/ml, VL 50-1000 copies/ml, and VL > 1000 copies/ml) in a multivariable analysis.

RESULTS

At 2 months of age, infants born to mothers with VL > 1000 copies/ml had lower CD4+ T cell counts compared to those born to mothers with VL < 50 copies/ml at the time of delivery (44.3% versus 48.3%, p = 0.007, and 2884 vs. 2432 cells/mm3, p = 0.02). These differences remained significant after adjusting for maternal and infant antiretroviral drug use, gender, race and gestational age, and persisted at 6 months of age. There were no differences in CD8+ T cell count or absolute CD19+ B cell count between groups, though higher CD19+ B cell percentage was seen among infants born to mothers with VL > 1000 copies/ml.

CONCLUSIONS

These results suggest that exposure to high levels of HIV-1 viremia in utero, even in the absence of perinatal transmission, may affect the infant's developing immune system. While further work needs to be done to confirm these findings, they reinforce the need for optimal treatment of HIV infected pregnant women, and careful follow-up of HEU infants.

HIV-exposed uninfected children: a growing population with a vulnerable immune system?

Through the successful implementation of policies to prevent mother-to-child-transmission (PMTCT) of HIV-1 infection, children born to HIV-1-infected mothers are now much less likely to acquire HIV-1 infection than previously. Nevertheless, HIV-1-exposed uninfected (HEU) children have substantially increased morbidity and mortality compared with children born to uninfected mothers (unexposed uninfected, UU), predominantly from infectious causes. Moreover, a range of phenotypical and functional immunological differences between HEU and UU children has been reported. As the number of HEU children continues to increase worldwide, two questions with clear public health importance need to be addressed: first, does exposure to HIV-1 and/or ART in utero or during infancy have direct immunological consequences, or are these poor outcomes simply attributable to the obvious disadvantages of being born into an HIV-affected household? Secondly, can we expect improved maternal care and ART regimens during and after pregnancy, together with optimized infant immunization schedules, to reduce the excess morbidity and mortality of HEU children?

Nutritional status and metabolic disorders in HIV-exposed uninfected prepubertal children

OBJECTIVE

The objective of the study was to assess the nutritional status and metabolic alterations in HIV-exposed uninfected (HIVe) children compared with HIV-unexposed (HIVn) children.

METHODS

A cross-sectional study was carried out with 76 children distributed into two groups: HIVe (n = 31) and HIVn (n = 45). Biochemical data (hematologic test, lipid profile, insulin resistance, hepatic profile, and C-reactive protein) were evaluated. Anthropometric parameters and body composition analyses were performed.

RESULTS

The groups were similar regarding body mass index-for-age z-scores (P = 0.297) and height-for-age z-scores (P = 0.666). HIVe had a higher dyslipidemia prevalence (38.7% versus 11.1%; P = 0.010), altered total cholesterol (TC) values (19.4% versus 2.2%; P = 0.016) higher LDL-C mean levels (97.8 mg/dl versus 86 mg/dl; P = 0.028), borderline low-density lipoprotein cholesterol (LDL-C) (40% versus 14%; P = 0.011) and TC (41.9% versus 20%; P = 0.038) compared with HIVn.

CONCLUSION

Despite the similar nutritional status between groups, our data clearly demonstrated a higher prevalence of dyslipidemia, altered TC, higher LDL-C levels and also LDL-C and TC borderline values in HIVe children.

Immunology of pediatric HIV infection

Most infants born to human immunodeficiency virus (HIV)-infected women escape HIV infection. Infants evade infection despite an immature immune system and, in the case of breastfeeding, prolonged repetitive exposure. If infants become infected, the course of their infection and response to treatment differs dramatically depending upon the timing (in utero, intrapartum, or during breastfeeding) and potentially the route of their infection. Perinatally acquired HIV infection occurs during a critical window of immune development. HIV's perturbation of this dynamic process may account for the striking age-dependent differences in HIV disease progression. HIV infection also profoundly disrupts the maternal immune system upon which infants rely for protection and immune instruction. Therefore, it is not surprising that infants who escape HIV infection still suffer adverse effects. In this review, we highlight the unique aspects of pediatric HIV transmission and pathogenesis with a focus on mechanisms by which HIV infection during immune ontogeny may allow discovery of key elements for protection and control from HIV.

The impact of maternal anti-retroviral therapy on cytokine profile in the uninfected neonates

The number of HIV-infected young women has been increasing since the beginning of the AIDS epidemic. The objective of the present study was to investigate the impact of anti-retroviral treatment (ART) of HIV-1-infected pregnant women (PW) on cytokine profile of uninfected neonates. Our results demonstrated that higher levels of IL-1β and TNF-α associated with lower IL-10 production were detected in the plasma obtained from neonates born from ART-treated PW. Furthermore, the production of TNF- α and IFN-γ was also significantly higher in polyclonally-activated T cells from those neonates. This elevated pro-inflammatory pattern detected by these activated-T cells was not associated to HIV-1 antigens sensitization. Finally, ART-exposed neonates showed to be born with lower weight, and it was inversely correlated with maternal peripheral TNF-a level. In summary, the data presented here suggest a significant disturbance in cytokine network of HIV-1-uninfected neonates exposed to potent anti-retroviral schemes during pregnancy.

Normal Thymic Size and Low Rate of Infections in Human Donor Milk Fed HIV-Exposed Uninfected Infants from Birth to 18 Months of Age

Objective. To evaluate the immune function in HIV-exposed uninfected (HIV-EU) infants fed human donor milk. Methods. Ultrasound-obtained thymic index (Ti), T-lymphocyte subsets, and the number of infections were examined from birth to 18 months of age in 18 HIV-EU infants. The infants were compared to a cohort of 47 term, HIV-unexposed breastfed or formula-fed infants. Results. The thymic size at 12 months of age was not significantly different between the HIV-EU group and the control infants (P = 0.56). At 4 months of age, the HIV-EU infants had significantly fewer infections than the control infants (P < 0.001). Furthermore, in the control group, the infants exclusively breastfed at 4 months of age had significantly fewer infections at 8 months when compared to age-matched formula-fed infants (P = 0.001). Conclusion. HIV-EU infants fed human donor milk have normal growth of thymus and contract fewer infections than other healthy infants. This finding along with fewer infections in exclusively breastfed infants compared to formula-fed infants supports the beneficial effect of human milk on the immune system. We suggest, when breastfeeding is not possible, that providing human donor milk to vulnerable groups of infants will be beneficial for their maturing immune system.

Impaired Bacillus Calmette-Guérin cellular immune response in HIV-exposed, uninfected infants

OBJECTIVE

To evaluate cell-mediated immune response to Bacillus Calmette-Guérin (BCG) vaccination in uninfected, HIV-1-exposed infants, comparing it with unexposed children.

DESIGN

It is designed as a cross-sectional study.

METHODS

BCG-specific lymphoproliferation and T-cell subsets (CD4(+), CD8(+) and TCR γδ(+)) by flow cytometry and interleukin-10, interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) concentration by ELISA were analyzed in HIV-exposed and unexposed infants. Whole blood lymphocyte immunophenotyping and blood counts were performed in exposed children. Nonparametric tests were used (P < 0.05).

RESULTS

Given the ontogeny of the immune system, exposed infants were separated into three groups according to age: exposed 1 (E1, aged 6.1-8.8 months), E2 (aged 9.1-17.1 months) and E3 (aged 18.1-26.3 months). Unexposed infants (UE group) and E1 were matched for age. Cell proliferation was not different among the three exposed groups, neither for BCG nor for phytohemagglutinin (PHA)-stimulated cultures. Furthermore, BCG-stimulated lymphoproliferation was reduced in the E1 group in comparison with the UE group. T-lymphocyte subpopulations also showed differences, with the youngest HIV-exposed groups (E1 and E2) showing a predominant proliferation of CD4(+) T cells in cultures with BCG, whereas E3 and UE groups had a robust γδ(+) T-cell expansion. There was lower IFN-γ concentration in the samples from E1 group in comparison with all of the other groups. The unexposed infants showed higher TNF-α concentration in cultures with BCG and PHA in comparison with E1 group.

CONCLUSION

BCG-specific T-cell proliferation was reduced in HIV-exposed uninfected infants and IFN-γ concentration was lower in younger exposed infants, showing a delay in immune system maturation of HIV-exposed infants.

Impaired humoral response to vaccines among HIV-exposed uninfected infants

Little is known about the vaccine protective response for infants born from HIV-infected mothers. We evaluated the antibody response to hepatitis B, tetanus, and diphtheria vaccine in vertically HIV-exposed uninfected infants and compared them to those of control infants not exposed to the virus. The quantitative determination of specific neutralizing antibodies against hepatitis B, diphtheria, and tetanus were performed blindly on serum samples. The results showed that 6.7% of the HIV-exposed uninfected individuals were nonresponders to hepatitis B vaccine (anti-HBs titer, <10 mIU/ml), and 64.4% were very good responders (anti-HBs titer, ≥1,000 mIU/ml), whereas only 3.6% of the nonexposed infants were nonresponders (χ(2)=10.93; 1 df). The HIV-exposed uninfected infants showed protective titers for diphtheria and tetanus but lower geometric mean anti-tetanus titers compared to those of the HIV-unexposed infants. Our data point to the necessity of evaluating vaccine immune responses in these children and reinforced that alterations in lymphocyte numbers and functions reported for newborns from HIV-infected mothers interfere with the vaccine response.

Characteristics of lymphocyte subsets in HIV-infected, long-term nonprogressor, and healthy Asian children through 12 years of age

BACKGROUND

There are limited data on the immune profiles of HIV-positive children compared with healthy controls, and no such data for Asian children.

OBJECTIVES

To immunophenotype HIV-positive Asian children, including long-term nonprogressors (LTNPs), compared with age-matched healthy controls.

METHODS

We used flow cytometry to analyze 13 lymphocyte and monocyte subsets from 222 untreated, HIV-positive children with 15% to 24% CD4(+) T cells and no AIDS-related illnesses and 142 healthy children (controls). Data were compared among age categories. Profiles from LTNPs (n = 50), defined as children ≥8 years old with CD4(+) T-cell counts ≥350 cells/mm(3), were compared with data from age-matched non-LTNPs (n = 17) and controls (n = 53).

RESULTS

Compared with controls, HIV-positive children had lower values (cell count per mm(3) and percent distribution) for T(H) cells and higher values for cytotoxic T cells, with reductions in populations of naive T(H) and cytotoxic T cells, B cells, and natural killer (NK) cells. HIV-positive children had high values for activated T(H) and cytotoxic T cells. Compared with non-LTNPs, LTNPs had higher values of T(H) and cytotoxic T cells, naive and memory T-cell subsets, and B and NK cells. Surprisingly, counts of activated T(H) and cytotoxic T cells were also higher among LTNPs. LNTPs were more frequently male.

CONCLUSION

Untreated, HIV-infected Asian children have immune profiles that differ from those of controls, characterized by low values for T(H) cells, naive T cells, B cells, and NK cells but high values for cytotoxic, activated T(H), and cytotoxic T cells. The higher values for activated T cells observed in LTNPs require confirmation in longitudinal studies.

Reduced thymic size but no evidence of impaired thymic function in uninfected children born to human immunodeficiency virus-infected mothers

BACKGROUND

HIV-exposed, uninfected (HIV-EU) infants present hematologic and immunologic abnormalities at birth, and it remains to be clarified whether these abnormalities persist beyond infancy, for instance, affecting vaccination responses.

METHODS

Thymic size and thymic output were evaluated in 20 HIV-EU children at 15 months of age and compared with 10 age- and gender-matched controls. Regulatory T-cells (Tregs) and immune activation as well as cytokine profiles were determined, and the antibody response to Haemophilus influenzae Type b (Hib) vaccination was evaluated.

RESULTS

Thymic size was significantly lower in HIV-EU children (P = 0.011). However, CD4 and CD8 counts did not differ between HIV-EU and control children. Likewise, thymic output estimated as CD4 cells expressing naive (CD45RA+CD62L+CD27+, P = 0.31) or recent thymic naive (CD45RA+CD27+CD31+, P = 0.13) phenotype, or CD4 cells containing T-cell receptor excision circles (P = 0.47) were comparable. HIV-EU children and controls had similar levels of activated cells (CD4+CD38+HLA-DR+, P = 0.87; CD8+CD38+HLA-DR+, P = 0.22), Tregs (CD4+CD25+CD127(low)FOXP3+, P = 0.53), and naive Tregs (CD4+CD25+CD127(low)FOXP3+CD45RA+CD27+, P = 0.65). Finally, comparable titers of Haemophilus influenzae Type b antibodies in the 2 groups were found (P = 0.43).

CONCLUSION

The study demonstrates reduced thymic size in HIV-EU children compared with children born to HIV-negative mothers, but no evidence of impaired thymic function, immune regulation, or antibody vaccination response was detected, suggesting that no qualitative immune deficits persist in HIV-EU children at 15 months of age.

Reference values of lymphocyte subsets in healthy, HIV-negative children in Cameroon

Lymphocyte subset reference values used to monitor infectious diseases, including HIV/AIDS, tuberculosis, malaria, or other immunological disorders in healthy children in Cameroon, are lacking. Values for Caucasian cohorts are already being utilized for clinical decisions but could be inappropriate for African populations. We report here the immunological profile for children aged from birth through 6 years in Cameroon and also compare our values to data from other African and Caucasian populations. In a cohort of 352 healthy children, aged 0 to 6 years, the relative and absolute numbers of T-cell subsets, B cells, and NK lymphocytes were determined from peripheral blood collected in EDTA tubes. Samples were stained with BD Multitest reagents in Trucount tubes and analyzed by using CellQuest-Pro and FlowJo software. We evaluated about 23 different lymphocyte subsets in which the absolute number and percentage values differed significantly (P < 0.05) with age and peaked between 6 and 12 months. B-cell values were higher compared to reported values from developed countries. Differences in activated and differentiated T cells were observed in subjects between 1 and 6 years of age. The absolute CD8(+) T-cell count and the CD4(+)/CD8(+) ratio seem to depend on gender. Normal lymphocyte subsets values among children from Cameroon differ from reported values in Caucasian and some African populations. The differences observed could be due to genetic and environmental factors coupled with the methodology used. These values could be used as initial national reference guidelines as more data are assembled.

The impact of maternal HIV infection on cord blood lymphocyte subsets and cytokine profile in exposed non-infected newborns

Background

Children born to HIV+ mothers are exposed intra-utero to several drugs and cytokines that can modify the developing immune system, and influence the newborn's immune response to infections and vaccines. We analyzed the relation between the distribution of cord blood lymphocyte subsets and cytokine profile in term newborns of HIV+ mothers using HAART during pregnancy and compared them to normal newborns.

Methods

In a prospective, controlled study, 36 mother-child pairs from HIV+ mothers and 15 HIV-uninfected mothers were studied. Hematological features and cytokine profiles of mothers at 35 weeks of pregnancy were examined. Maternal and cord lymphocyte subsets as well as B-cell maturation in cord blood were analyzed by flow cytometry. The non-stimulated, as well as BCG- and PHA-stimulated production of IL2, IL4, IL7, IL10, IL12, IFN-γ and TNF-alpha in mononuclear cell cultures from mothers and infants were quantified using ELISA.

Results

After one year follow-up none of the exposed infants became seropositive for HIV. An increase in B lymphocytes, especially the CD19/CD5+ ones, was observed in cord blood of HIV-exposed newborns. Children of HIV+ hard drug using mothers had also an increase of immature B-cells. Cord blood mononuclear cells of HIV-exposed newborns produced less IL-4 and IL-7 and more IL-10 and IFN-γ in culture than those of uninfected mothers. Cytokine values in supernatants were similar in infants and their mothers except for IFN-γ and TNF-alpha that were higher in HIV+ mothers, especially in drug abusing ones. Cord blood CD19/CD5+ lymphocytes showed a positive correlation with cord IL-7 and IL-10. A higher maternal age and smoking was associated with a decrease of cord blood CD4+ cells.

Conclusions

in uninfected infants born to HIV+ women, several immunological abnormalities were found, related to the residual maternal immune changes induced by the HIV infection and those associated with antiretroviral treatment. Maternal smoking was associated to changes in cord CD3/CD4 lymphocytes and maternal hard drug abuse was associated with more pronounced changes in the cord B cell line.

Immunologic basis for revaccination of HIV-infected children receiving HAART

With increasing access to antiretroviral therapy for children infected with HIV, especially in sub-Saharan Africa, better understanding of the development and maintenance of memory T- and B-cell responses to pathogens after immune reconstitution is needed to assess the risk of infection. Knowledge of long-term immune responses after starting HAART is of particular importance for policies on revaccination of HIV-infected children, who may lose protective immunity to prior infections and immunizations. We review normal development of T- and B-cell memory responses to viruses and vaccines against viral pathogens, and contrast the immunological effects of perinatal HIV transmission with HIV infection acquired later in life. We then explore the potential benefits of antiretroviral therapy and revaccination, using measles virus as a model.