HIV patients on antiretroviral therapy have high frequencies of CD8 T cells specific for Immediate Early protein-1 of cytomegalovirus

OBJECTIVE: To assess the frequency and phenotype of cytomegalovirus (CMV)-specific CD8 T cells in previously immunocompromised HIV patients with stable undetectable HIV viremia due to highly active antiretroviral therapy (HAART). METHODS: Twenty-one CMV-seropositive HIV patients with nadir CD4 T-cell counts < 50 x 10(6) cells/l, at least 4 years on HAART and 6 months of complete viral suppression (< 50 HIV RNA copies/ml) and 12 CMV-seropositive, HIV-seronegative age/sex-matched controls were studied. CD4 and CD8 T-cell responses to whole CMV and two HLA-A*02 restricted CMV peptides [NLV from pp65 and VLE from Immediate Early 1 (IE1)] were measured by interferon (IFN)gamma ELISpot. Phenotypes of peptide-specific CD8 T cells were determined by tetramer staining. RESULTS: In the ELISpot assay, HIV patients had significantly more CD8 T cells producing IFN gamma in response to VLE than controls, whereas numbers of NLV-specific and CMV-specific IFN gamma spots were similar. Four HIV patients and one control had large VLE and/or NLV-specific CD8 T-cell populations despite the absence of CMV-specific CD4 T cells. The majority of peptide-specific CD8 T cells from HIV patients and controls were CD28-, CD45RO+ and CD45RA-. However, a significantly higher proportion of VLE-specific CD8 T cells expressed perforin compared to NLV-specific CD8 T cells in HIV patients. CONCLUSIONS: HIV patients had elevated numbers of IE1-specific, IFNgamma-producing perforin-positive CD8 T cells compared to controls. As IE1 is expressed early during CMV reactivation, these cells may be important for preventing CMV replication to pathogenic levels. In addition, CMV-specific CD4 T cells are not essential for maintenance of large populations of CMV-specific CD8 T cells in aviremic HIV patients on HAART.