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Detection of HIV-1-Specific-CD4 T Cells by ELISPOT in Patients on Prolonged Highly Active Antiretroviral Therapy (HAART) A. CHARLES, C. WALLON, O. LAMBOTTE, J. F. DELFRAISSY, and Y. TAOUFIK.
Faculté de Médecine Paris Sud et Hôpital de Bicêtre, France Background: It has been suggested that CD4+ T cells play an important role in controlling chronic viral infection. HIV-1-specific CD4 T cells are characteristically not detected in chronically HIV infected patients by lymphoproliferative assays. Here we investigated the presence of HIV-1-specific CD4 T cells by using ELISPOT assay in a selected population of patients on HAART with long term undetectable viremia.
Patients and methods: CD8-depleted peripheral blood mononuclear cells (PBMC) were isolated from 13 patients on HAART with undetectable viral load for 56 to 108 weeks (< 50 copies/mL). Cells were activated for 6 days with various recall antigens, Tuberculin, Tetanus toxoid (TT) and Cytomegalovirus (CMV) or a combination of HIV-1 p24 and Nef. Corrected frequencies of IFN-g expressing cells were determined by ELISPOT. Lymphoproliferative responses (LPR) to recall antigens and HIV proteins were also measured.
Results: The median frequency of IFN-g expressing cells in response to HIV proteins in the 13 patients was 0.08% (range: 0% to 1.01%). Significant frequencies, defined as > 0.1%, was found in 6 patients (46%) (median 0.17%; range: 0.11-1.01%). No apparent relationship was observed between frequencies and the time of undetectable HIV plasma viral load. Significant frequencies of IFN-g expressing cells after activation with Tuberculin, TT or CMV were detected in 46% (median: 0.31%; range: 0.11-1.24%), 50% (median: 0.27%; range: 0.17-1.88%) and 37% patients (median: 0.18%; range: 0.11-0.98%), respectively. In contrast, no significant LPR (Stimulation Index > 3) to HIV antigens were detected; however, in the presence of exogenous IL-12, significant LPR were observed in 2 patients. Significant LPR to Tuberculin, TT and CMV in the presence or absence of exogenous IL-12 were found in 5/1, 1/1 and 1/1 patients, respectively.
Conclusion: HIV-1-specific CD4+ T cells were detected in several patients on prolonged HAART with undetectable viremia. Lymphoproliferative responses were observed only after addition of exogenous IL-12.
Key Words: ELISPOT, HIV specific cells, Proliferation
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