Parallel decline of CD8+/CD38++ T cells and viraemia in response to quadruple highly active antiretroviral therapy in primary HIV infection.

Objectives: To monitor changes in the numbers of CD8 lymphocytes expressing the activated CD38++ phenotype in peripheral blood samples from patients with primary HIV infection (PHI) treated with highly active antiretroviral therapy (HAART).

Methods: Zidovudine, lamivudine, abacavir and amprenavir were initiated during PHI as part of the Quest study. Absolute numbers of CD8+/CD38++ T cells were determined using three-colour flow cytometry, and plasma viral load (VL) was measured using the Roche Amplicor method.

Results: The median, pre-therapy CD8+/CD38++ T cell count was 461/mm(3)(interquartile range 216, 974) in 131 patients compared with normal control values of less than 20 cells/mm(3). Levels fell markedly in parallel with VL within the first 2 weeks of HAART initiation, to a median of 47 cells/mm(3) at 28 weeks (median 436 cell decline; P < 0.001). At that time, 80% of patients had a VL less than 50 copies/ml, and 16.3% of all patients had less than 20 CD8+/CD38++ T cells/mm(3). A continued decrease in CD8+/CD38++ T cell count occurred in 67.2% of patients whose VL was maintained below 50 copies/ml (median change from first to last value -18 cells/mm(3); P < 0.001).

Conclusion: After the initiation of HAART in PHI, CD8+/CD38++ lymphocytes declined rapidly in parallel with VL, and allowed for a normalization of CD8+/CD38++ T cell numbers in a subset of patients at week 28. Cell numbers continued to decline in patients who maintained VL below 50 copies/ml, indicating that the CD8+/CD38++ T cell count may represent a marker of residual viral replication when VL falls below detectable levels after HAART intervention.