Breast milk CD4+ T cells express high levels of C chemokine receptor 5 and CXC chemokine receptor 4 and are preserved in HIV-infected mothers receiving highly active antiretroviral therapy.

Background: Transmission of human immunodeficiency virus (HIV) to the infant through breast-feeding is a major problem worldwide; however, the biological circumstances of such transmission remain unclear. Little characterization of breast milk CD4(+) T lymphocytes has been done so far.

Methods: We performed a detailed immunophenotypic analysis of T lymphocytes in the breast milk, compared with the blood, of HIV-uninfected (n=9) and HIV-infected (n=10) women receiving highly active antiretroviral therapy, by use of multiparameter flow cytometry. Descriptive statistics and nonparametric comparisons were performed using SAS software (version 9.1; SAS Institute).

Results: In uninfected women, 44%-78% of breast milk CD4(+) T cells expressed the C chemokine receptor 5 (CCR5), whereas 26%-73% of cells coexpressed CCR5 and CXC chemokine receptor 4 (CXCR4). In contrast, only 7%-20% of peripheral blood CD4(+) T cells expressed CCR5 and 1%-20% coexpressed CCR5 and CXCR4. The level of CCR5 expression in CD4(+) T cells in breast milk was higher than in blood. In HIV-infected women, the high frequency of CD4(+)CCR5(+) T cells in breast milk was preserved.

Conclusions: A majority of CD4(+) T cells in breast milk express high levels of CCR5 and CXCR4. Unlike other mucosal immune sites, in which CD4(+)CCR5(+) T cells are rapidly eliminated by HIV, these cells are preserved in breast milk during HIV infection.