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Background:  The use of HAART in severely immunodeficient HIV patients co-infected with cytomegalovirus (CMV) usually results in increased CMV-specific CD4 T-cell responses but it is unclear how long they persist. We have measured CMV-specific CD4 T-cell responses using 3 different assays over 5 years of HAART. In addition, CD8 T-cell responses to CMV peptides were measured after 4 to 5 years to determine if patients had CD8 T-cell responses to CMV.

Methods:  PBMC were collected over a 5-year period from 50 patients with a nadir CD4 T-cell count of <50/mL. Assays of lymphoproliferation and IFN-g production in cell culture detected by ELISA (IFN-g ELISA) were undertaken on fresh cells and INF-g ELISpot assays were performed on cryopreserved cells. Results were analyzed in 6 windows:  baseline and years 1, 2, 3, 4, and 5. Not all patients contributed to each window but there were no significant demographic differences between windows. CD8 T-cell responses to peptides of CMV IE-1 (VLEETSVML [VLE]) and pp65 (NLVPMVATV [NLV]) were measured by ELISpot and tetramer assays in HLA-A2⁺ patients with HIV RNA <50 copies/mL who had received HAART for a median time of 5.7 years (range 4.3 to 6.2; n = 13) and in CMV⁺ controls (n = 8).

Results:  By all 3 assays, median CMV-specific CD4 T-cell responses remained low in year 1 but increased thereafter to year 3 when they were higher than baseline (p <0.005 for lymphoproliferation and ELISpot assays) and not significantly different to CMV⁺ healthy controls (n = 21). However, by year 5 their was a marked decline in responses to values that were lower than controls (p <0.005 for IFN-g ELISpot and IFN-g ELISA) and not significantly different from baseline for the lymphoproliferation assay and IFN-g ELISA. Analysis of all IFN-g ELISpot values (n = 111) by piecewise regression models showed an increase from months 0 to 20 of HAART (p = 0.001) and a decrease from month 40 onward (p = 0.015). The decrease in CMV-specific CD4 T-cell responses was not associated with a decrease in CD4 T-cell counts or an increase in plasma HIV RNA. CD8 T-cell responses to VLE by ELISpot were higher in patients than controls (p = 0.038) and 8 patients had VLE/tetramer+CD8 T-cells compared with none of the controls (p = 0.0063). NLV-specific CD8 T-cells were not significantly different from controls.

Conclusions:  We conclude that severely immunodeficient HIV patients on HAART for 5 years do not maintain CMV-specific CD4 T-cell responses and that increased CD8 T-cell responses to IE-1 may be an early indicator of recurrent CMV replication.

Keywords: CMV; immune reconstitution; longterm HAART