Abstract:
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-LewisX
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
TNFa, IL-1b, IL-6, IL-8, MIP-1a, MIP-1b, 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 cellassociated
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.
