In vivo effects of HIV-1 exposure in the presence and absence of single-dose nevirapine on cellular plasma activation markers of infants born to HIV-1-seropositive mothers

Reduced B cell frequencies in cord blood of HIV-exposed uninfected infants: an immunological and transcriptomic analysis

Introduction

In the course of immune development, HIV-exposed uninfected (HEU) infants exhibit abnormal immune function and increased infectious morbidity compared to HIV-unexposed uninfected (HUU) infants. Yet the specific functional phenotypes and regulatory mechanisms associated with in-utero HIV and/or ART exposure remain largely obscure.

Methods

We utilized flow cytometry and RNA-seq technologies to conduct the immunological and transcriptomic profiling in cord blood from 9 HEU mother-infant pairs and 24 HUU pairs. On top of that, we compared the cord blood dataset with the maternal venous blood dataset to characterize unique effects induced by in-utero HIV and/or ART exposure.

Results

Flow cytometry immunophenotyping revealed that the level of B lymphocyte subsets was significantly decreased in HEU cord blood as compared to HUU (P < 0.001). Expression profiling-based cell abundance assessment, includes CIBERSORT and ssGSEA algorithm, showed a significantly reduced abundance of naive B cells in HEU cord blood (both P < 0.05), supporting the altered composition of B lymphocyte subsets in HEU. Functional enrichment analysis demonstrated suppressed innate immune responses and impaired immune regulatory function of B cells in HEU cord blood. Furthermore, through differential expression analysis, co-expression network analysis using WGCNA, and feature selection analysis using LASSO, we identified a 4-gene signature associated with HEU status. This signature effectively assesses B cell levels in cord blood, enabling discrimination between HEU and HUU infants.

Discussion

Our study provides the first comprehensive immunological and transcriptomic characterization of HEU cord blood. Additionally, we establish a 4-gene-based classifier that holds potential for predict immunological abnormalities in HEU infants.

Growth Trajectories of HIV Exposed and HIV Unexposed Infants. A Prospective Study in Gweru, Zimbabwe

Background

With the increasing HIV seroprevalence among women of childbearing age in sub-Saharan Africa, limited data on growth outcomes of HIV exposed infants under current policies of universal maternal antiretroviral therapy exist.

Methods

The longitudinal growth patterns of 114 HIV exposed and unexposed infants were assessed and compared. The prevalence and factors associated with malnutrition were established. Infants under prevention of mother to child transmission care were recruited at 6 weeks post-delivery as were their HIV unexposed counterparts. Weight and length measurements were recorded at birth, 6 and 16 weeks postpartum.

Results

HIV vertical transmission rate was 8.8%. HIV exposed infants had significantly lower mean birth weights compared to HIV unexposed infants (2.9 ± 0.3; 3.2 ± 0.5; P < .001) respectively. Mean weight/length-for-age z-scores for HIV exposed, uninfected (HEU) infants were significantly below those of the HIV unexposed infants during follow up. By 6 weeks of age, 28.5% of HEU infants were malnourished while no malnutrition was evident in HIV unexposed infants. A gestational age <37 weeks (OR: 3.83; 95% CI: 1.03-14.30; P = .045) and HIV exposure (OR: 1.62; 95% CI: 0.17-15.73; P = .017) substantially increased the risk of stunting.

Conclusion

Growth deficits were witnessed in HIV exposed infants compared to HIV unexposed infants. There is need for early nutritional monitoring and support among HIV exposed infants.

Growth pattern in Ethiopian infants - the impact of exposure to maternal HIV infection in relation to socio-economic factors

Background: Infants exposed to maternal HIV infection who remain HIV-uninfected (HIV-exposed/uninfected; HIV-EU) may be at increased risk of growth retardation, which could be due both to directly HIV-related effects and to socio-economic factors overrepresented among HIV-positive women.

Objective: To investigate growth development at 9–12 months of age in HIV-EU infants participating in prevention of mother-to-child transmission (PMTCT) care compared to HIV unexposed (HIV-U) infants in relation to socio-economic conditions.

Methods: Anthropometric and socio-economic data were collected retrospectively from PMTCT registers (for HIV-EU infants), with HIV-U controls recruited at measles vaccination at public health facilities in Ethiopia. Growth was compared with regard to HIV exposure and socio-economic variables in multivariate regression analysis.

Results: The following growth measurements were found for 302 HIV-EU and 358 HIV-U infants at 9–12 months of age, respectively: mean weight-for-age z-score (WAZ) 0.04 and −0.21, p < 0.001 (proportion underweight 5.7% and 6.7%, p = 0.60); median length-for-age z-score (LAZ) −0.92 and −0.91, p = 0.53 (proportion stunted 25.1% and 20.5%, p = 0.17). In multivariate analysis, lower WAZ was associated with male sex (p = 0.021), lower maternal education (p < 0.001), presence of siblings (p < 0.01) and HIV-U (p < 0.01). Underweight was associated with male sex (p = 0.017) and absence of maternal education (p = 0.019). Lower LAZ was associated with male sex (p < 0.001), presence of siblings (p < 0.001) and poor maternal education (p < 0.01), while stunting was associated with male sex (p < 0.001), presence of siblings (p < 0.001), few rooms in the home (p < 0.01), access to running water (p = 0.026) and low level of maternal education (p = 0.014).

Conclusions: At 9–12 months of age, HIV-EU infants had non-inferior growth and higher mean WAZ than HIV-U controls. Poor growth development was associated with socio-economic factors. This suggests health benefits from PMTCT participation for infant growth. Similar interventions could be considered for Ethiopian infants, irrespective of HIV exposure, with a particular focus on children with poor socio-economic status.

The Effect of Human Immunodeficiency Virus and Cytomegalovirus Infection on Infant Responses to Vaccines: A Review

The success of prevention of mother to child transmission programs over the last two decades has led to an increasing number of infants who are exposed to human immunodeficiency virus (HIV), but who are not themselves infected (HIV-exposed, uninfected infants). Although the morbidity and mortality among HIV-exposed, uninfected infants is considerably lower than that among HIV-infected infants, they may remain at increased risk of infections in the first 2 years of life compared with their HIV-unexposed peers, especially in the absence of breastfeeding. There is some evidence of immunological differences in HIV-exposed, uninfected infants, which could play a role in susceptibility to infection. Cytomegalovirus (CMV) may contribute to the increased immune activation observed in HIV-exposed, uninfected infants. Infants born to HIV-infected women are at increased risk of congenital CMV infection, as well as early acquisition of postnatal CMV infection. In infants with HIV infection, CMV co-infection in early life is associated with higher morbidity and mortality. This review considers how HIV infection, HIV exposure, and CMV infection affect infant responses to vaccination, and explores possible immunological and other explanations for these findings. HIV-infected infants have lower vaccine-induced antibody concentrations following tetanus, diphtheria, pertussis, hepatitis B, and pneumococcal vaccination, although the clinical relevance of this difference is not known. Despite lower concentrations of maternal-specific antibody at birth, HIV-exposed, uninfected infants respond to vaccination at least as well as their HIV-unexposed uninfected peers. CMV infection leads to an increase in activation and differentiation of the whole T-cell population, but there is limited data on the effects of CMV infection on infant vaccine responses. In light of growing evidence of poor clinical outcomes associated with CMV infection in HIV-exposed, uninfected infants, further studies are particularly important in this group. A clearer understanding of the mechanisms by which maternal viral infections influence the developing infant immune system is critical to the success of maternal and infant vaccination strategies.

Breastfeeding Behaviors and the Innate Immune System of Human Milk: Working Together to Protect Infants against Inflammation, HIV-1, and Other Infections

The majority of infants’ breastfeeding from their HIV-infected mothers do not acquire HIV-1 infection despite exposure to cell-free virus and cell-associated virus in HIV-infected breast milk. Paradoxically, exclusive breastfeeding regardless of the HIV status of the mother has led to a significant decrease in mother-to-child transmission (MTCT) compared with non-exclusive breastfeeding. Although it remains unclear how these HIV-exposed infants remain uninfected despite repeated and prolonged exposure to HIV-1, the low rate of transmission is suggestive of a multitude of protective, short-lived bioactive innate immune factors in breast milk. Indeed, recent studies of soluble factors in breast milk shed new light on mechanisms of neonatal HIV-1 protection. This review highlights the role and significance of innate immune factors in HIV-1 susceptibility and infection. Prevention of MTCT of HIV-1 is likely due to multiple factors, including innate immune factors such as lactoferrin and elafin among many others. In pursuing this field, our lab was the first to show that soluble toll-like receptor 2 (sTLR2) directly inhibits HIV infection, integration, and inflammation. More recently, we demonstrated that sTLR2 directly binds to selective HIV-1 proteins, including p17, gp41, and p24, leading to significantly reduced NFκB activation, interleukin-8 production, CCR5 expression, and HIV infection in a dose-dependent manner. Thus, a clearer understanding of soluble milk-derived innate factors with known antiviral functions may provide new therapeutic insights to reduce vertical HIV-1 transmission and will have important implications for protection against HIV-1 infection at other mucosal sites. Furthermore, innate bioactive factors identified in human milk may serve not only in protecting infants against infections and inflammation but also the elderly; thus, opening the door for novel innate immune therapeutics to protect newborns, infants, adults, and the elderly.

Transfer of Maternal Antimicrobial Immunity to HIV-Exposed Uninfected Newborns

The transfer of maternal immune factors to the newborn is critical for protection from infectious disease in early life. Maternally acquired passive immunity provides protection until the infant is beyond early life's increased susceptibility to severe infections or until active immunity is achieved following infant's primary immunization. However, as reviewed here, human immunodeficiency virus (HIV) infection alters the transfer of immune factors from HIV-infected mothers to the HIV-exposed newborns and young infants. This may relate to the immune activation in HIV-infected pregnant women, associated with the production of inflammatory cytokines at the maternofetal interface associated with inflammatory responses in the newborn. We also summarize mother-targeting interventions to improve the health of infants born to HIV-infected women, such as immunization during pregnancy and reduction of maternal inflammation. Maternal immunization offers the potential to compensate for the decreased transplacentally transferred maternal antibodies observed in HIV-exposed infants. Current data suggest reduced immunogenicity of vaccines in HIV-infected pregnant women, possibly reducing the protective impact of maternal immunization for HIV-exposed infants. Fortunately, levels of antibodies appear preserved in the breast milk of HIV-infected women, which supports the recommendation to breast-feed during antiretroviral treatment to protect HIV-exposed infants.

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.

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.

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.

In-utero infection with HIV-1 associated with suppressed lymphoproliferative responses at birth

In-utero exposure to HIV-1 may affect the immune system of the developing child and may induce HIV-1-specific immune responses, even in the absence of HIV-1 infection. We evaluated lymphoproliferative capacity at birth among 40 HIV-1-uninfected infants born to HIV-1-infected mothers and 10 infants who had acquired HIV-1 in utero. Cord blood mononuclear cells were assayed using [(3) H]-thymidine incorporation for proliferation in response to HIV-1 p55-gag and the control stimuli phytohaemagglutinin (PHA), Staphylococcus enterotoxin B (SEB) and allogeneic cells. In response to HIV-1 p55-gag, eight (20%) HIV-1-exposed, uninfected (EU) infants had a stimulation index (SI) ≥ 2 and three (30%) in-utero HIV-1 infected infants had SI ≥2. The frequency and magnitude of responses to HIV-1 p55-gag were low overall, and did not differ statistically between groups. However, proliferative responses to control stimuli were significantly higher in EU infants than in infants infected in utero, with a median SI in response to PHA of 123 [interquartile range (IQR) 77-231] versus 18 (IQR 4-86) between EU and infected infants, respectively (P < 0·001). Among infected infants, gestational maturity was associated with the strength of HIV-1 p55-gag response (P < 0·001); neither maternal nor infant HIV-1 viral load was associated. In summary, EU and HIV-1-infected infants mounted HIV-1-specific lymphoproliferative responses at similar rates (20-30%), and although global immune function was preserved among EU infants, neonatal immune responses were significantly compromised by HIV-1 infection. Such early lymphoproliferative compromise may, in part, explain rapid progression to AIDS and death among HIV-1-infected infants.

Altered innate immune development in HIV-exposed uninfected infants

BACKGROUND

Early in life, HIV-exposed uninfected (HEU) infants are at an increased risk of morbidity and mortality from infectious disease compared with HIV-unexposed (UE) infants. To improve our understanding of the mechanisms underlying their increased risk, we contrasted innate immune development between HEU and UE infants in a developing world setting, where early life infectious disease risk is exceptionally high.

METHODS

A prospective longitudinal cohort of HEU and UE newborns was established, and the most detailed characterization to date of HEU infant immune development was performed. Single-cell cytokine production was analyzed by flow cytometry after stimulation of whole blood with pathogen-associated molecular patterns (PAMPs).

RESULTS

Monocyte, classical dendritic cell, and plasmacytoid dendritic cell composition was similar between HEU and UE infants throughout the first year of life. However, HEU mononuclear cells mounted an enhanced pro-inflammatory response to PAMP stimulation, both in quantity of cytokine produced per cell and in proportion of responder cells. Significant differences in cytokine production were detected on the single-cell level in a PAMP-specific pattern, but only at 2 and 6 weeks of age; all differences normalized by 12 months of age.

CONCLUSIONS

This time course of innate immune deviation early in life corresponds to the clinical window of vulnerability to infections in HEU infants and may be at least partially responsible for their increased morbidity and mortality from infectious disease.

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?

Naturally-occurring genetic variants in human DC-SIGN increase HIV-1 capture, cell-transfer and risk of mother-to-child transmission

BACKGROUND

Mother-to-child transmission (MTCT) is the main cause of HIV-1 infection in children worldwide. Dendritic cell-specific ICAM-3 grabbing-nonintegrin (DC-SIGN, also known as CD209) is an HIV-1 receptor that enhances its transmission to T cells and is expressed on placental macrophages.

METHODS AND FINDINGS

We have investigated the association between DC-SIGN genetic variants and risk of MTCT of HIV-1 among Zimbabwean infants and characterized the impact of the associated mutations on DC-SIGN expression and interaction with HIV-1. DC-SIGN promoter (p-336C and p-201A) and exon 4 (198Q and 242V) variants were all significantly associated with increased risk of intrauterine (IU) HIV-1 infection. Promoter variants decreased DC-SIGN expression both in vitro and in placental CD163(+) macrophages (Hofbauer cells) of HIV-1 unexposed infants but not of HIV-1 exposed infants. The exon 4 protein-modifying mutations increased HIV-1 capture and transmission to T cells in vitro.

CONCLUSION

This study provides compelling evidence to support an important role of DC-SIGN in IU HIV-1 infection.

KIR-HLA and maternal-infant HIV-1 transmission in sub-Saharan Africa

Numerous studies have suggested a role for natural killer (NK) cells in attenuation of HIV-1 disease progression via recognition by killer-cell immunoglobulin-like receptors (KIRs) of specific HLA class I molecules. The role of KIR and HLA class I has not been addressed in the context of maternal-infant HIV-1 transmission. KIR and HLA class I B and C genes from 224 HIV-1-infected mothers and 222 infants (72 infected and 150 uninfected) from South Africa were characterized. Although a number of significant associations were determined in both the total group and in the nevirapine (NVP) exposed group, the most significant findings involved KIR2DL2 and KIR2DL3 and HLA-C. KIR2DL2/KIR2DL3 was underrepresented in intrapartum (IP)-transmitting mothers compared to non-transmitting (NT) mothers (P = 0.008) and remained significant (P = 0.036) after correction for maternal viral load (MVL). Homozygosity for KIR2DL3 alone and in combination with HLA-C allotype heterozygosity (C1C2) was elevated in IP-transmitting mothers compared to NT mothers (P = 0.034 and P = 0.01 respectively), and after MVL correction (P = 0.033 and P = 0.027, respectively). In infants, KIR2DL3 in combination with its HLA-C1 ligand (C1) as well as homozygosity for KIR2DL3 with C1C2, were both found to be underrepresented in infected infants compared to exposed uninfected infants in the total group (P = 0.06 and P = 0.038, respectively) and in the sub-group of infants whose mothers received NVP (P = 0.007 and P = 0.03, respectively). These associations were stronger post MVL adjustment (total group: P = 0.02 and P = 0.009, respectively; NVP group: P = 0.004 and P = 0.02, respectively). Upon stratification according to low and high MVL, all significant associations fell within the low MVL group, suggesting that with low viral load, the effects of genotype can be more easily detected. In conclusion this study has identified a number of significant associations that suggest an important role for NK cells in maternal-to-infant HIV-1 transmission.

Effect of Maternal HIV-1 Status and Antiretroviral Drugs on Haematological Profiles of South African Infants in Early Life

Maternal HIV-1 status and antiretroviral drug exposure may influence the haematological profiles of infants. We recruited infants from 118 uninfected control women and from 483 HIV-1 infected women who received no antiretroviral drugs (n=28), or received single-dose Nevirapine (sdNVP) (n=424) or triple-drug combination therapy (n=31) to reduce HIV-1 transmission. Blood was drawn from infants within 24 hours of delivery or 6-12 weeks post-delivery and full blood counts performed using a fully automated AcT-5-diff haematology analyser and reference controls. Exposed uninfected (EU; no NVP) differed from control infants only in having lower basophil counts and percentages. In all infant groups, leukocyte profiles showed characteristic quantitative changes with age in the first 6 weeks of life. HIV-1 infected infants displayed by 6 weeks elevations in white blood cells, lymphocyte, monocyte and basophil counts, and monocyte and basophil percentages, when compared to EU infants. At birth EU NVP-treated infants exhibited elevated monocyte percentages and counts and basophil counts that did not persist at 6 weeks. Interestingly, EU newborns of mothers with high CD4 counts (> 500 cells/μl) that had taken sdNVP had significantly elevated white blood cell, monocyte and basophil counts when compared to newborn infants of mothers with similar CD4 counts that had not taken sdNVP; this was not evident in infants of mothers with CD4 counts <200 cells/μl. These previously undescribed features may affect immune response capability in early life and clinical consequences of such changes need to be further investigated.

Human immunodeficiency virus (HIV) infection during pregnancy induces CD4 T-cell differentiation and modulates responses to Bacille Calmette-Guérin (BCG) vaccine in HIV-uninfected infants

Human immunodeficiency virus (HIV)-negative infants born to HIV-positive mothers frequently exhibit a range of immunological abnormalities. We tested the hypothesis that HIV during pregnancy affects the ability of CD4 T cells of HIV-negative infants to respond to vaccine challenge by recruiting HIV-negative infants born to HIV-negative and HIV-positive mothers and measuring their responses to Bacille Calmette-Guérin (BCG) vaccine given at birth. At 2 weeks, maternal HIV status did not influence CD4 T-cell counts or differentiation, but by 10 weeks CD4 counts of infants born to HIV-positive mothers fell to a level characteristic of HIV-positive infants. Among the CD4 T-cell populations, markers of differentiation (CCR7⁻ CD45RA⁻ CD27⁻) and senescence (CD57, PD-1) were more common among infants born to HIV-positive mothers than among infants born to HIV-negative mothers. At 2 weeks of age, we assessed the effector response to heat-killed BCG and tuberculin purified protein derivative (PPD) by overnight interferon (IFN)-γ enzyme-linked immunosorbent spot-forming cell assay (ELISpot), but found no measurable effect of maternal HIV status. At 10 weeks, we assessed CD4 T-cell memory by measuring proliferation in response to the same antigens. We observed a bimodal response that allowed infants to be classified as high or low responders and found that fewer infants born to HIV-positive mothers were able to mount a robust proliferative response, suggesting that their reduced CD4 counts and increased differentiation indicated a deficiency in their ability to develop immunological memory.

Host genetic determinants of human immunodeficiency virus infection and disease progression in children

Increasing data support host genetic factors as an important determinants of human immunodeficiency virus type-1 (HIV-1) susceptibility, mother-to-child transmission (MTCT), and disease progression. Of these genetic mediators, those impacting innate and adaptive immune responses seem to play a critical role in viral infectivity and pathogenesis. During primary infection, CCR5 using virus is predominantly transmitted and polymorphisms that affect the expression of CCR5 alter the risk for MTCT and rate of disease. Chemokines that naturally bind to coreceptors alter infectivity and viral pathogenesis. Additional genes that affect innate immunity including those encoding for MBL2 and those modulating the adaptive immune response including CX3CR1 and human leukocyte antigen types can significantly modify susceptibility and response to HIV-1 infection. As young children develop, the dependence on certain arms of the immune system varies and can alter the effect of genetic variants. Additionally, host genetic factors may alter the response to antiretrovirals. Finally, because HIV-infected children progress more rapidly than adults and have fewer background cofactors, such as drug use and coinfections, the effects of host factors on HIV-1 disease may be more clearly identified. In this review, we summarize available data on the impact of host genetics on MTCT and disease progression of HIV-infected children.

The HIV-exposed, uninfected African child

The increasing success of prevention of mother-to-child HIV transmission programmes means that in Africa, very large numbers of HIV-exposed, uninfected (HIV-EU) children are being born. Any health problems that these children may have will thus be of enormous public health importance, but to date have been largely neglected. There is some evidence that HIV-EU African children are at increased risk of mortality, morbidity and slower early growth than their HIV-unexposed counterparts. A likely major cause of this impaired health is less exposure to breast milk as mothers are either less able to breastfeed or stop breastfeeding early to protect their infant from HIV infection. Other contributing factors are parental illness or death resulting in reduced care of the children, increased exposure to other infections and possibly exposure to antiretroviral drugs. A broad approach for psychosocial support of HIV-affected families is needed to improve health of HIV-EU children. High quality programmatic research is needed to determine how to deliver such care.

Associations of chemokine receptor polymorphisms With HIV-1 mother-to-child transmission in sub-Saharan Africa: possible modulation of genetic effects by antiretrovirals

BACKGROUND

HIV-1 mother-to-child transmission (MTCT) remains an important route of infection in sub-Saharan Africa.

METHODS

Genetic variants in CCR5 promoter, CCR2, CX3CR1, and Stromal cell-derived factor-1 (SDF-1) genes were determined in 980 infants from sub-Saharan Africa using real-time polymerase chain reaction to determine association with MTCT.

RESULTS

In antiretroviral-naive mother-infant pairs (n = 637), CCR5 promoter polymorphisms at positions 59029: A allele vs. G/G [odds ratio (OR): 1.61, 95% confidence interval (CI): 1.04 to 2.48; P = 0.032] and 59356: T allele vs. C/C (OR: 0.63, 95% CI: 0.41 to 0.96; P = 0.033) and CCR2-180: G allele vs. A/A (OR: 3.32, 95% CI: 1.13 to 9.73; P = 0.029) were associated with risk of MTCT. Treatment of HIV-1-infected mothers and infants with single-dose nevirapine or perinatal zidovudine altered but did not eliminate the association of genetic variants with MTCT.

CONCLUSIONS

CCR5 promoter, CCR2, and CX3CR1 polymorphisms were associated with risk of MTCT likely through their role as an HIV-1 coreceptor or by modulating the early immune response. Host genetics may continue to alter MTCT when short-course interventions that only partially suppress virus are used. These findings will need to be confirmed in validation cohorts with a large number of infected infants.

African infants' CCL3 gene copies influence perinatal HIV transmission in the absence of maternal nevirapine

BACKGROUND

Individuals with more copies of CCL3L1 (CCR5 ligand) than their population median have been found to be less susceptible to HIV infection. We investigated whether maternal or infant CCL3L1 gene copy numbers are associated with perinatal HIV transmission when single-dose nevirapine is given for prevention.

METHOD

A nested case-control study was undertaken combining data from four cohorts including 849 HIV-infected mothers and their infants followed prospectively in Johannesburg, South Africa. Access to antiretroviral drugs for the prevention of perinatal transmission differed across the cohorts. Maternal and infant CCL3L1 gene copy numbers per diploid genome (pdg) were determined by real-time polymerase chain reaction for 79 out of 83 transmitting pairs ( approximately 10% transmission rate) and 235 randomly selected non-transmitting pairs.

RESULTS

Higher numbers of infant, but not maternal, CCL3L1 gene copies were associated with reduced HIV transmission (P = 0.004) overall, but the association was attenuated if mothers took single-dose nevirapine or if the maternal viral load was low. Maternal nevirapine was also associated with reduced spontaneously released CCL3 (P = 0.007) and phytohemagglutinin-stimulated CCL3 (P = 0.005) production in cord blood mononuclear cells from uninfected infants.

CONCLUSION

We observed a strong association between higher infant CCL3L1 gene copies and reduced susceptibility to HIV in the absence of maternal nevirapine. We also observed a reduction in newborn CCL3 production with nevirapine exposure. Taken together, we hypothesize that nevirapine may have direct or indirect effects that partly modify the role of the CCR5 ligand CCL3 in HIV transmission, obscuring the relationship between this genetic marker and perinatal HIV transmission.

Low maternal viral loads and reduced granulocyte-macrophage colony-stimulating factor levels characterize exposed, uninfected infants who develop protective human immunodeficiency virus type 1-specific responses

Human immunodeficiency virus type 1 (HIV-1)-specific cellular immune responses are elicited in a proportion of infants born to HIV-1-infected mothers and are associated with protection against vertical transmission. To investigate correlates of these HIV-1-specific responses, we examined levels of the immune activation markers neopterin, beta(2)-microglobulin (beta(2)-m), and soluble l-selectin (sl-selectin); the immunomodulatory and hematopoietic factors interleukin-7 (IL-7), stromal-cell-derived factor 1 alpha (CXCL12), and granulocyte-macrophage colony-stimulating factor (GM-CSF); and the immunoregulatory cytokine IL-10 among a group of newborns born to HIV-1-positive mothers who did not receive any antiretroviral drugs for prevention of perinatal HIV-1 transmission. Cellular immune responses to HIV-1 envelope (Env) peptides were also measured. We aimed to determine whether newborns who elicit HIV-1-specific cellular immune responses (Env(+)) and those who lack these responses (Env(-)) exhibit unique immune features. Our data confirmed that no Env(+) infants acquired HIV-1 infection. Among exposed, uninfected infants, Env(+) infants had reduced immune activation (as measured by beta(2)-m and sl-selectin levels in cord blood plasma) compared to Env(-) infants as well as reduced GM-CSF levels in cord blood plasma. There was also a reduced ability of cord blood mononuclear cells to be induced to produce GM-CSF among Env(+) infants. Maternal viral load was lower in Env(+) infants, suggesting that exposure to low levels of antigen may be responsible for priming the protective responses. These findings suggest that infants who are able to develop apparently protective HIV-1-specific cellular immune responses have immunological features and viral exposure histories that distinguish them from their nonresponder counterparts, providing new insights into the development of HIV-1 protective immunity.