Link between the X4 phenotype in human immunodeficiency virus type 1-infected mothers and their children, despite the early presence of R5 in the child.

Coreceptor use was determined for human immunodeficiency virus type 1 (HIV-1) isolates of various subtypes from 11 women during pregnancy and their infected children. Isolates from peripheral blood mononuclear cells (n=79) and from plasma (n=59) were available. The clinical and immunological stages of HIV-1 infection were recorded. Coreceptor use was tested on human cell lines expressing CD4 and different chemokine receptors. The R5 virus predominated, and only 9 isolates from 2 mothers used CXC chemokine receptor 4. All children carried the R5 virus at the time of diagnosis of HIV-1 infection. In 2 children of mothers carrying the X4 virus, the virus switched from R5 to X4 or to R5X4 by age 18 months (child no. 9) and age 48 months (child no. 10), whereas no children followed up to a similar age whose mothers were carrying the R5 virus experienced such a switch (P=.048). This points to a link between the presence of X4 virus in the mother and the emergence of X4 virus in her child.