Evaluation of CD4(+) T cell function in vivo in HIV-infected patients as measured by bacteriophage phiX174 immunization

Bacteriophage phiX174 immunization was used to measure CD4(+) T cell functi on in vivo in human immunodeficiency virus (HIV)-infected patients across a ll disease stages. Function was evaluated by measuring the ability of T cel ls to provide help to B cells in antibody production, amplification, and is otype switching. A total of 33 patients and 10 controls received 3 bacterio phage phiX174 immunizations 6 weeks apart. The patients' responses regardin g bacteriophage-specific total antibody titers and IgG titers were quantita tively and qualitatively inferior to the controls' responses. Overall, 7 of 33 patients had normal T cell function. Baseline CD4 counts provided the s trongest correlation with total antibody and IgG titers. HIV RNA had a weak er association with responses but had some predictive power among patients with a CD4 count >200 cells/mu L. Bacteriophage phiX174 immunization seems to be a useful tool for measuring immune function in vivo, which suggests t hat most HIV-infected patients may have abnormal CD4(+) T cell function des pite adequate antiretroviral treatment.