Control of HIV during a structured treatment interruption in chronically infected individuals with vigorous T cell responses

Abstract

Purpose: To study whether and under what circumstances HIV can be controlled in chronically infected patients. Method: Nine patients treated with hydroxyurea and didanosine (PANDAs) were compared with 7 patients on highly active antiretroviral therapy (HAART) during an 8-week treatment interruption. Both groups had similar baseline viral load, CD4 count, and length of treatment. Treatment was resumed if viral rebound > 10,000 copies/mL (virological failure) or CD4 count decrease below 200 cells/mm3 (immunological failure) occurred in two consecutive measurements. Results: None of the PANDAs failed. Viral rebound was spontaneously contained, and CD4 count remained stable. Four out of 7 patients in the HAART group failed to control HIV by week 6 and had to restart therapy due to either viremia rebound or CD4 decrease. Before therapy interruption, the PANDAs had a vigorous HIV-specific T cell immune response (median CD4VIR 1.2%), while the HAART-treated patients did not (median CD4VIR 0.2%) (CD4VIR represents the percentage of HIV-specific CD4 subpopulation expressing IFN-γ within the total CD4 population [CD3+, CD4+, IFN-γ+]). This difference was statistically significant (p = .002). Conclusion: This study shows that HIV can be controlled during therapy interruption in patients with established infection, and that control of viral replication correlates with vigorous anti-HIV specific immune responses.