The virological and immunological consequences of structured treatment interruptions in chronic HIV-1 infection

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Abstract
Some individuals with chronic HIV-1 infection have discontinued their drug therapy with consequent plasma virus rebound. In a small number of patients, a delayed or absent rebound in plasma virus load has been noted after drug cessation, apparently associated with prior drug interruptions and autologous boosting of HIV-1 specific immune responses. We hypothesized that cyclic structured treatment interruptions structured treatment interruptions (STI) could augment HIV-1 specific immune responses in chronic HIV-1 infection, which might help to control HIV-1 replication off therapy. We initiated an STI pilot study in 10 antiretroviral treatment-naive HIV-1 chronically infected subjects with baseline CD4 T-cell counts > 500 × 106 cells/l and plasma viral load > 5000 copies/ml who received highly active antiretroviral therapy (HAART) for 1 year with good response (plasma viral load In all of the patients viral load rebounded, but doubling times increased significantly between the first and third stops (P = 0.008), and by the third stop, six out of nine subjects had a virological set-point after a median 12 months off therapy that was lower than baseline before starting HAART (ranging from 0.6 log10 to 1.3 log10 lower than baseline) and in four it remained stable below 5000 copies/ml. Those subjects who controlled viral replication developed significantly stronger HIV-1 specific cellular immune responses than subjects lacking spontaneous decline (P 6 Our findings suggest that STI in chronic HIV-1 infection might augment HIV-1-specific cellular immune responses associated with a spontaneous and sustained drop in plasma viral load in some subjects but at the potential cost of lower CD4 T-cell counts.