Breast Milk from Tanzanian Women has Divergent Effects on Cell-Free and Cell-Associated HIV-1 Infection in Vitro.

Transmission of HIV-1 during breastfeeding is a significant source of new pediatric infections in sub-Saharan Africa. Breast milk from HIV-positive mothers contains both cell-free and cell-associated virus; however, the impact of breast milk on HIV-1 infectivity remains poorly understood. In the present study, breast milk was collected from HIV-positive and HIV-negative Tanzanian women attending antenatal clinics in Dar es Salaam. Milk was analyzed for activity in vitro against both cell-free and cell-associated HIV-1. Potent inhibition of cell-free R5 and X4 HIV-1 occurred in the presence of milk from all donors regardless of HIV-1 serostatus. Inhibition of cell-free HIV-1 infection positively correlated with milk levels of sialyl-Lewis(X) from HIV-positive donors. In contrast, milk from 8 of 16 subjects enhanced infection with cell-associated HIV-1 regardless of donor serostatus. Milk from two of these subjects contained high levels of multiple pro-inflammatory cytokines including TNFα, IL-1β, IL-6, IL-8, MIP-1α, MIP-1β, MCP-1 and IP-10, and enhanced cell-associated HIV-1 infection at dilutions as high as 1∶500. These findings indicate that breast milk contains innate factors with divergent activity against cell-free and cell-associated HIV-1 in vitro. Enhancement of cell-associated HIV-1 infection by breast milk may be associated with inflammatory conditions in the mother and may contribute to infant infection during breastfeeding

Characteristics of Tanzanian breast milk donors.

<p>Characteristics of Tanzanian breast milk donors.</p

Enhancement of cell-associated HIV-1 infection by breast milk.

<p>Breast milk from HIV-positive and HIV-negative donors was evaluated for activity against cell-associated HIV-1 infection in TZM-bl cell assays. Breast milk was tested at 5-fold serial dilutions (1∶4, 1∶20, 1∶100 and 1∶500). Percent inhibition or enhancement of cell-associated R5 HIV-1_BAL is shown for breast milk samples from individual HIV-positive (open circles) and HIV-negative (closed circles) donors.</p

Inhibition of cell-free HIV-1 by breast milk.

<p>Mature breast milk from HIV-positive (n = 8) and HIV-negative (n = 8) donors was evaluated for inhibition of cell-free HIV-1 in TZM-bl cell assays. Cells were infected with R5 HIV-1_BaL in the presence of five-fold serial dilutions of breast milk. Percent inhibition was calculated relative to control cultures infected with HIV-1_BaL in the absence of added breast milk. HIV-inhibitory activity of breast milk from HIV-positive (dotted line) and HIV-negative (solid line) donors is shown (mean ± SD).</p

Immune factors in breast milk from Tanzanian donors.

<p>The concentrations of multiple immune factors including cytokines, chemokines and growth factors were measured in breast milk samples using a multiplex panel. Data for each factor is expressed as concentration (pg/mL) and is presented for all donors irrespective of HIV serostatus.</p

Lewis^X and sialyl-Lewis^X in breast milk.

<p>Levels of Lewis^X and sialyl-Lewis^X were measured by ELISA in breast milk samples from both HIV-positive and HIV-negative donors. The results were then compared to cell-free HIV-inhibitory activity for the same samples. Data is expressed as the percent inhibition of cell-free R5 (□) and X4 (♦) HIV-1 relative to the levels of either Lewis^X or sialyl-Lewis^X measured for each sample.</p