Jan Walter

Effects of early, abrupt weaning on HIV-free survival of children in Zambia.

BACKGROUND In low-resource settings, many programs recommend that women who are infected with the human immunodeficiency virus (HIV) stop breast-feeding early. We conducted a randomized trial to evaluate whether abrupt weaning at 4 months as compared with the standard practice has a net benefit for HIV-free survival of children. METHODS We enrolled 958 HIV-infected women and their infants in Lusaka, Zambia. All the women planned to breast-feed exclusively to 4 months; 481 were randomly assigned to a counseling program that encouraged abrupt weaning at 4 months, and 477 to a program that encouraged continued breast-feeding for as long as the women chose. The primary outcome was either HIV infection or death of the child by 24 months. RESULTS In the intervention group, 69.0% of the mothers stopped breast-feeding at 5 months or earlier; 68.8% of these women reported the completion of weaning in less than 2 days. In the control group, the median duration of breast-feeding was 16 months. In the overall cohort, there was no significant difference between the groups in the rate of HIV-free survival among the children; 68.4% and 64.0% survived to 24 months without HIV infection in the intervention and control groups, respectively (P=0.13). Among infants who were still being breast-fed and were not infected with HIV at 4 months, there was no significant difference between the groups in HIV-free survival at 24 months (83.9% and 80.7% in the intervention and control groups, respectively; P=0.27). Children who were infected with HIV by 4 months had a higher mortality by 24 months if they had been assigned to the intervention group than if they had been assigned to the control group (73.6% vs. 54.8%, P=0.007). CONCLUSIONS Early, abrupt cessation of breast-feeding by HIV-infected women in a low-resource setting, such as Lusaka, Zambia, does not improve the rate of HIV-free survival among children born to HIV-infected mothers and is harmful to HIV-infected infants.(ClinicalTrials.gov number, NCT00310726.)

High uptake of exclusive breastfeeding and reduced early post-natal HIV transmission.

Background Empirical data showing the clear benefits of exclusive breastfeeding (EBF) for HIV prevention are needed to encourage implementation of lactation support programs for HIV-infected women in low resource settings among whom replacement feeding is unsafe. We conducted a prospective, observational study in Lusaka, Zambia, to test the hypothesis that EBF is associated with a lower risk of postnatal HIV transmission than non-EBF. Methods and Results As part of a randomized trial of early weaning, 958 HIV-infected women and their infants were recruited and all were encouraged to breastfeed exclusively to 4 months. Single-dose nevirapine was provided to prevent transmission. Regular samples were collected from infants to 24 months of age and tested by PCR. Detailed measurements of actual feeding behaviors were collected to examine, in an observational analysis, associations between feeding practices and postnatal HIV transmission. Uptake of EBF was high with 84% of women reporting only EBF cumulatively to 4 months. Post-natal HIV transmission before 4 months was significantly lower (p = 0.004) among EBF (0.040 95% CI: 0.024–0.055) than non-EBF infants (0.102 95% CI: 0.047–0.157); time-dependent Relative Hazard (RH) of transmission due to non-EBF = 3.48 (95% CI: 1.71–7.08). There were no significant differences in the severity of disease between EBF and non-EBF mothers and the association remained significant (RH = 2.68 95% CI: 1.28–5.62) after adjusting for maternal CD4 count, plasma viral load, syphilis screening results and low birth weight. Conclusions Non-EBF more than doubles the risk of early postnatal HIV transmission. Programs to support EBF should be expanded universally in low resource settings. EBF is an affordable, feasible, acceptable, safe and sustainable practice that also reduces HIV transmission providing HIV-infected women with a means to protect their childrens lives. Trial Registration ClinicalTrials.gov NCT00310726

Reduction in Preterm Delivery and Neonatal Mortality after the Introduction of Antenatal Cotrimoxazole Prophylaxis among HIV-Infected Women with Low CD4 Cell Counts

BACKGROUND Cotrimoxazole prophylaxis is recommended for subgroups of human immunodeficiency virus (HIV)-infected adults and children to reduce all-cause morbidity and mortality. We investigated whether antenatal cotrimoxazole prophylaxis begun during pregnancy for HIV-infected pregnant women with low CD4 cell counts would affect birth outcomes. METHODS Cotrimoxazole prophylaxis was introduced as a routine component of antenatal care for HIV-infected women with CD4 cell counts <200 cells/ micro L during the course of a trial of mother-to-child HIV transmission in Lusaka, Zambia. Rates of preterm delivery, low birth weight, and neonatal mortality were compared for women with low CD4 cell counts before and after its introduction. RESULTS Among 255 women with CD4 cell counts <200 cells/ micro L, the percentage of preterm births (< or =34 weeks of gestation) was lower (odds ratio [OR], 0.49 [95% confidence interval {CI}, 0.24-0.98]) after cotrimoxazole prophylaxis was introduced than before; there was a significant decrease in neonatal mortality (9% to 0%; P=.01) and a trend toward increased birth weight ( beta =114 g [95% CI, -42 to 271 g]). In contrast, there were no significant changes in these parameters over the same time interval among women with CD4 cell counts > or =200 cells/ micro L.Conclusion. Antenatal provision of cotrimoxazole for HIV-infected pregnant women with low CD4 cell counts may have indirect benefits for neonatal health.

High concentrations of interleukin 15 in breast milk are associated with protection against postnatal HIV transmission.

Given the central role that interleukin 15 (IL-15) plays in human immunodeficiency virus (HIV) immunity, we hypothesized that IL-15 in breast milk may protect against postnatal HIV transmission. In a nested case-control study, we compared breast milk IL-15 levels in 22 HIV-infected women who transmitted HIV to their infants to those in 72 nontransmitters. Samples were collected in the first month of life, prior to HIV infection. IL-15 concentrations were associated with a decreased risk of HIV transmission in unadjusted analysis and after adjusting for milk viral load, CD4 cell count, and other cytokines in breast milk. IL-15-mediated immunity may protect against HIV transmission during breast-feeding.

Antiretroviral exposure and lymphocyte mtDNA content among uninfected infants of HIV-1-infected women.

OBJECTIVE: Concern for potential adverse effects of antiretroviral (ARV) chemotherapy used to prevent mother-to-child HIV transmission has led the US Public Health Service to recommend long-term follow-up of ARV-exposed children. Nucleoside reverse transcriptase inhibitor ARV agents can inhibit DNA polymerase γ, impairing mitochondrial DNA (mtDNA) synthesis and resulting in depletion or dysfunction. METHODS: We measured the mtDNA content of stored peripheral blood mononuclear cells (PBMCs) of 411 healthy children who were born to HIV-uninfected women and 213 uninfected infants who were born to HIV-infected women with or without in utero and neonatal ARV exposure. Cryopreserved PBMC mtDNA was quantified by using the Primagen Retina Mitox assay. RESULTS: Geometric mean PBMC mtDNA levels were lower at birth in infants who were born to HIV-infected women. Among HIV-exposed children, mtDNA levels were lowest in those who were not exposed to ARVs, higher in those with exposure to zidovudine alone, and higher still in those with combination nucleoside reverse transcriptase inhibitor exposure. A similar pattern was observed in the corresponding women. Levels of mtDNA increased during the first 5 years of life in all HIV-exposed children but achieved normal levels only in those with ARV exposure. CONCLUSIONS: Levels of mtDNA are lower than normal in HIV-exposed children. Contrary to expectation, PBMC mtDNA levels are significantly higher in ARV-exposed, HIV-uninfected infants and their infected mothers compared with ARV-unexposed infants and women. By 5 years, levels of PBMC mtDNA rise to normal concentrations in ARV-exposed children but remain depressed in ARV-unexposed children.

Restriction of HIV-1 Genotypes in Breast Milk Does Not Account for the Population Transmission Genetic Bottleneck That Occurs following Transmission

Background Breast milk transmission of HIV-1 remains a major route of pediatric infection. Defining the characteristics of viral variants to which breastfeeding infants are exposed is important for understanding the genetic bottleneck that occurs in the majority of mother-to-child transmissions. The blood-milk epithelial barrier markedly restricts the quantity of HIV-1 in breast milk, even in the absence of antiretroviral drugs. The basis of this restriction and the genetic relationship between breast milk and blood variants are not well established. Methodology/Principal Findings We compared 356 HIV-1 subtype C gp160 envelope (env) gene sequences from the plasma and breast milk of 13 breastfeeding women. A trend towards lower viral population diversity and divergence in breast milk was observed, potentially indicative of clonal expansion within the breast. No differences in potential N-linked glycosylation site numbers or in gp160 variable loop amino acid lengths were identified. Genetic compartmentalization was evident in only one out of six subjects in whom contemporaneously obtained samples were studied. However, in samples that were collected 10 or more days apart, six of seven subjects were classified as having compartmentalized viral populations, highlighting the necessity of contemporaneous sampling for genetic compartmentalization studies. We found evidence of CXCR4 co-receptor using viruses in breast milk and blood in nine out of the thirteen subjects, but no evidence of preferential localization of these variants in either tissue. Conclusions/Significance Despite marked restriction of HIV-1 quantities in milk, our data indicate intermixing of virus between blood and breast milk. Thus, we found no evidence that a restriction in viral genotype diversity in breast milk accounts for the genetic bottleneck observed following transmission. In addition, our results highlight the rapidity of HIV-1 env evolution and the importance of sample timing in analyses of gene flow.

4E10-resistant HIV-1 isolated from four subjects with rare membrane-proximal external region polymorphisms.

Human antibody 4E10 targets the highly conserved membrane-proximal external region (MPER) of the HIV-1 transmembrane glycoprotein, gp41, and has extraordinarily broad neutralizing activity. It is considered by many to be a prototype for vaccine development. In this study, we describe four subjects infected with viruses carrying rare MPER polymorphisms associated with resistance to 4E10 neutralization. In one case resistant virus carrying a W680G substitution was transmitted from mother to infant. We used site-directed mutagenesis to demonstrate that the W680G substitution is necessary for conferring the 4E10-resistant phenotype, but that it is not sufficient to transfer the phenotype to a 4E10-sensitive Env. Our third subject carried Envs with a W680R substitution causing variable resistance to 4E10, indicating that residues outside the MPER are required to confer the phenotype. A fourth subject possessed a F673L substitution previously associated with 4E10 resistance. For all three subjects with W680 polymorphisms, we observed additional residues in the MPER that co-varied with position 680 and preserved charged distributions across this region. Our data provide important caveats for vaccine development targeting the MPER. Naturally occurring Env variants described in our study also represent unique tools for probing the structure-function of HIV-1 envelope.

Low and undetectable breast milk interleukin-7 concentrations are associated with reduced risk of postnatal HIV transmission.

Objective:To investigate if breast milk interleukin [IL]-7 concentrations are associated with postnatal HIV transmission. Design:A case-control study nested within a cohort of women recruited in Lusaka, Zambia. Methods:IL-7 breast milk concentrations were measured in samples from 24 HIV-infected breast-feeding women who transmitted HIV to their child after the neonatal period and from 47 women who did not transmit. Samples were frequency-matched by the time of sample collection (1 week and 1 month postpartum). Logistic regression was used to adjust for possible confounders. For comparison, samples from 18 HIV-uninfected women from the same community were included in the analysis, and plasma IL-7 was determined. Results:Breast milk IL-7 concentrations were significantly higher than plasma IL-7 concentrations in all 3 groups. In contrast to levels among transmitters and HIV-uninfected women, breast milk IL-7 concentrations exhibited a bimodal distribution among nontransmitters. Breast milk IL-7 concentrations undetectable or less than 30 pg/mL were significantly associated with less HIV transmission (odds ratio = 0.13, 95% confidence interval: 0.03 to 0.64). The association remained strong after adjustment for breast milk viral load and sodium, maternal CD4 cell counts, parity, and time of sample collection. Conclusion:Breast milk IL-7 may be necessary for effective HIV transmission.

Advances in basic science understanding of mother-to-child HIV-1 transmission.

Purpose of reviewThe present review summarizes and discusses studies on the mechanisms underlying mother-to-child HIV transmission published in 2006–2007. Recent findingsMany studies have focused on the pathogenesis of breast milk transmission. Recent analyses comparing cell-free and cell-associated virus in milk suggest that cell-associated virus may play a greater role in transmission than previously appreciated. Transmitted HIV variants appear to be resistant to neutralizing maternal antibodies and have enhanced replicative capacity suggesting greater fitness. Several adaptive and innate immune factors were identified that enhanced or impeded transmission. SummaryAdvances have been made in delineating the risk and protective factors mediating mother-to-child transmission. Many questions, however, still remain unanswered. Understanding the immune mechanisms that prevent most children from becoming infected with HIV and the properties of viruses that ‘pass through the gauntlet’ are central to prevention efforts.

HIV-1 Concentrations in Human Breast Milk Before and After Weaning

Reducing the frequency of breast-feeding during weaning and nonexclusive breast-feeding boosts HIV-1 RNA and DNA concentrations in the breast milk of HIV-infected women. Knowing When to Wean Breast-feeding is essential for infant survival and well-being in the low-resource settings in sub-Saharan Africa most affected by the HIV-1 epidemic. This necessitates breast-feeding by HIV-1–infected mothers despite the 10 to 15% risk of transmitting the infection to the infant via breast milk. Concentrations of HIV-1 in breast milk influence whether the breast-fed infant will acquire infection. Kuhn and colleagues conducted a clinical trial among 958 women in Lusaka, Zambia, to evaluate the safety and efficacy of exclusive breast-feeding followed by abrupt weaning at 4 months as a strategy to prevent postnatal HIV-1 transmission and promote healthy child survival. Women were randomized to wean abruptly at 4 months or to continue breast-feeding for a duration of their own choosing and were followed with their infants from delivery to 24 months postpartum. Infants were tested at regular intervals to determine their HIV-1 status, and concentrations of HIV-1 RNA and DNA were measured in breast milk at 4 and 4.5 months. Two weeks after weaning (4.5 months), HIV-1 concentrations in breast milk were substantially higher than if breast-feeding continued. Among those continuing to breast-feed at 4.5 months, HIV-1 concentrations in milk were lowest if breast-feeding was exclusive. The boost in milk HIV-1 concentrations during weaning counteracted any advantage of shortening the duration of breast-feeding on overall postnatal HIV-1 transmission risks. Breast milk is produced in response to infant suckling. The new data demonstrate that changes in the frequency of suckling as occurs with nonexclusive breast-feeding and at the time of weaning also influence HIV-1 concentrations in breast milk. The results support continuation and possible intensification of maternal antiretroviral drug treatment over the full duration of time when any breast milk exposures are likely to occur after planned weaning. Concentrations of HIV-1 RNA and DNA in mucosal compartments influence the risk of sexual transmission and mother-to-child transmission of HIV-1. Breast milk production is physiologically regulated such that supply is a function of infant demand, but whether demand also influences HIV-1 dynamics in breast milk is unknown. We tested whether minor and major changes in feeding frequency influence breast milk viral concentrations in 958 HIV-1–infected women and their infants followed, for 24 months during a trial in Lusaka, Zambia. Women were randomized to wean abruptly at 4 months or to continue breast-feeding for a duration of their own choosing. Two weeks after breast-feeding cessation (4.5 months), HIV-1 concentrations in breast milk were substantially higher (median RNA, 2708 copies/ml; DNA, 14 copies/ml) than if breast-feeding continued (median RNA, <50 copies/ml; DNA, <1 copy/ml; P < 0.0001). Among those continuing breast-feeding, HIV-1 concentrations in milk were higher if breast-feeding was nonexclusive (median RNA, 293 copies/ml; DNA, 2 copies/ml; P = 0.0006). Elevated milk viral concentrations after stopping breast-feeding explained higher than expected rates of late postnatal HIV transmission in those who weaned early. Changes in the frequency of breast-feeding peri-weaning and with nonexclusive breast-feeding influenced milk viral concentrations. This may explain the reduced risk of HIV-1 transmission associated with exclusive breast-feeding and why early weaning does not achieve the magnitude of HIV prevention predicted by models. Our results support continuation of maternal antiretroviral drug interventions over the full duration of time when any breast milk exposures may occur after planned weaning.