Compartmentalization of HIV-1 between breast milk and blood of HIV-infected mothers.

HIV-1 variants in breast milk and peripheral blood have been compared in three HIV-1 infected mothers. Analysis of DNA and RNA env C2-V3 sequences showed a differential distribution of HIV variants between the two compartments. The major provirus variant found in breast milk corresponds to a minor variant in the blood of two mothers. In the third mother, the predominant proviral variant detected in breast milk was not represented in the HIV-1 blood population. The major RNA variant in breast milk was not represented in the blood of two mothers. The predominant RNA variant in breast milk and blood was however the same for the third mother. Unexpectedly, the pattern of free virus variants in breast milk of three mothers did not correspond to that of the proviral form, suggesting that free viruses do not derive from infected cells in breast milk. The observation of a compartmentalization of HIV-1 between peripheral blood and breast milk emphasizes that postnatal transmission of HIV occurs with variants that may not be predicted from the analysis of circulating viral populations.