Correlation of loss of CD4 T cells with plasma levels of both soluble form Fas (CD95) Fas ligand (FasL) in HIV-infected infants.

Fas and Fas ligand (FasL), members of the TNFR and TNF families of molecules involved in apoptosis, respectively, are expressed in membrane-associated as well as soluble forms. Soluble Fas (sFas) and sFasL were evaluated in sequential samples from 16 HIV-infected and 11 HIV-exposed uninfected infants at ages 0-13 months. Regardless of the state of infection, age-dependent decreases in peripheral CD4 T cell counts and increases in sFas and sFasL were noted. However, decreases of the percentage CD4 T cells were more prominent in HIV-infected infants, and this was correlated significantly with increased plasma levels of sFas and sFasL (P = 0.002 and 0.004, respectively). Moreover, the levels of sFas in HIV-infected infants were found to be directly correlated with plasma HIV RNA (P = 0.03) and were significantly increased as early as age <1 month and prior to the onset of CD4 T cell decline. In uninfected infants, there was no such correlation between CD4 counts and the levels of sFas/sFasL. Plasma levels of sFas and sFasL may thus be important indicators of disease progression in perinatal HIV infection.