In vitro cell-mediated immune responses of human immunodeficiency virus-infected and -uninfected individuals to whole cytomegalovirus antigens and their subunits

The aim of this study was to optimize the ability to detect cytomegalovirus (CMV)-specfic cell-mediated immunity (CMI) in human immunodeficiency virus (HIV)-infected individuals by comparing different assays (the lymphocyte proliferation assay [LPA] and assays for gamma interferon [IFN-7] and interleukin-2 [IL-2] production) and CMV antigenic preparations. Thresholds discriminating positive from negative CMI results were developed with specimens from 36 CMV-seropositive and 21 CMV-seronegative healthy individuals. The analysis showed that the CMI elicited by any of the four CMV whole lysates tested in this study tended to be more robust and sensitive than the responses to the subunit antigens gB and pp65. LPA and inducible IFN-7 but not IL-2 were highly sensitive measures of CMV-specific CMI in HIV-infected and -uninfected individuals. The ability to detect CMV-speciflc LPA or IFN-7 responses in HIV-infected individuals significantly increased with higher CD4 cell numbers. Nevertheless, the proportion of HIV-infected subjects with CD4 counts of ≥500 cells/μl who had a detectable CMV-specific CMI remained significantly lower than that of healthy adults. The ability to detect CMV-specific CMI in HIV-infected individuals decreased with higher levels of HIV replication, with discriminative thresholds of 10³ to 10⁴ HIV RNA copies/ml of plasma, for LPA or inducible IFN-γ production elicited by different antigens. The LPA responses obtained with CMV whole lysate and phytohem-agglutinin were significantly correlated in HIV-infected subjects but not uninfected controls, indicating a novel characteristic of the CMI defect caused by HIV. The intrasubject variabilities of the CMV-specific CMI were similar in HIV-infected and -uninfected individuals. These data show that LPA and the inducible IFN-7 production elicited by CMV whole lysates may be used to assess modifications of the immune competency of HIV-infected individuals.