HIV-1 viral rebound dynamics after a single treatment interruption depends on time of initiation of highly active antiretroviral therapy.

OBJECTIVE: An important pending question is whether temporary highly active antiretroviral therapy during primary HIV infection can influence viral rebound dynamics and the subsequently established viral setpoint, through preservation and enhancement of HIV-1-specific immune responses, or through other mechanisms.
METHODS: We included all patients from two prospective studies who underwent a single treatment interruption while being well suppressed on highly active antiretroviral therapy. One group started highly active antiretroviral therapy during primary HIV infection, and the other group started it during chronic HIV infection with CD4 cell counts above 350 cells/microl. Data were collected up to 48 weeks from treatment interruption. The median time to viral rebound was analysed for three levels of viraemia: 50, 500 and 5000 copies HIV-RNA/ml plasma.
RESULTS: The median time to viral rebound was significantly longer in primary HIV infection patients (n = 24) than in chronic HIV infection patients (n = 46): 8 versus 4 weeks (P < 0.001 for all three endpoints). In two primary HIV infection patients, no rebound of plasma HIV-1 RNA over 50 copies/ml occurred. In the first 4 weeks after treatment interruption, CD4+ T-cell counts declined with a median of -5.0 cells/microl blood per week in the primary HIV infection group and -45 cells/microl blood per week in the chronic HIV infection group (P < 0.05). From week 4 to 48, the decline in CD4+ T-cell count was similar in both groups.
CONCLUSION: Plasma viral load and CD4 dynamics after a single interruption of highly active antiretroviral therapy were different for primary HIV infection and chronic HIV infection patients. Viral rebound is delayed or absent and early CD4 cell count decline after treatment interruption is less pronounced in primary HIV infection patients.