Viral dynamics of acute HIV-1 infection

Viral dynamics were intensively investigated in eight patients with acute H IV infection to define the earliest rates of change in plasma HIV RNA befor e and after the start of antiretroviral therapy. We report the first estima tes of the basic reproductive number (R-0), the number of cells infected by the progeny of an infected cell. during its lifetime when target cells are not depleted. The mean initial viral doubling time was 10 h, and the peak of viremia occurred 21 d after reported HIV exposure. The spontaneous rate of decline (alpha) was highly variable among individuals. The phase 1 viral decay rate (delta(I) = 0.3/day) in subjects initiating potent antiretrovir al therapy during acute HIV infection was similar to estimates from treated subjects with chronic HIV infection. The doubling time in two subjects who discontinued antiretroviral therapy was almost five times slower than duri ng acute infection. The mean basic reproductive number (R-0) of 19.3 during the logarithmic growth phase of primary HIV infection suggested that a vac cine or postexposure prophylaxis of at least 95% efficacy would be needed t o extinguish productive viral infection in the absence of drug resistance o r viral latency. These measurements provide a basis for comparison of vacci ne and other strategies and support the validity of the simian immunodefici ency virus macaque model of acute HIV infection.