Lymphocyte subset analyses were performed to establish mormative data for comparison with HIV-infected infants to provide insights into unique features of early pediatric HIV infection.

Methods: Samples were analyzed from 20 uninfected adults and from the following infant groups (0-12 months of age): 36 HIV seroreverters, 11 HIV-infected, 4 HIV-unexposed. Three and four color flow cytometry was performed detecting: CD4, 8, 28, 38; RO and RA; FAS and Ki67 antigens. Apoptosis was quantified, following overnight culture with and without heat shock, by detection of annexin expression and 7AAD nuclear binding.

Results: As previously documented, infants had higher levels of RA-expressing (naive) and CD38 positive lymphocytes. While both CD4 and CD8 lymphocytes from infected infants had higher numbers expressing Ki67(proliferation), FAS, and RO (memory), this effect was more prominent among the CD8 fraction as were lower levels of CD8CD28 (activation) lymphocytes. Aberrantly high expression of FAS and Ki67 were concentrated in the CD8RO subset compared with smaller elevations within the RA subset of CD4 lymphocytes. While apoptosis was similar for mononuclear cell populations from all study groups, specific increases were noted for CD8 lymphocytes from infected infants.

Conclusions: Quantitatively, the most aberrant cellular subset among infected infants regarding proliferation(Ki67), FAS expression, activation (CD28), and apoptosis was the CD8 memory fraction compared with a lower variance from normal for the CD4 naive subset. This data supports the concept that CD8 dysregulation is a key feature of early pediatric HIV infection.