Biological and virologic characteristics of primary HIV infection

Background: The clinical events surrounding acute HIV-1 infection have been well described, but little is known about whether the virologic course of acute HIV-1 infection influences the subsequent progression of disease. Objective: To define the virologic natural history of acute and very early HIV infection. Design: Prospective, longitudinal cohort study. Setting: University of Washington Research Clinic Participants: 74 adults enrolled soon after acquisition of HIV (mean, 69 days). Measurements: Plasma HIV-1 RNA levels; quantitative cell cultures; CD4 cell counts; and detailed clinical assessments done at study entry, biweekly for 1 month, monthly for 2 months, and quarterly thereafter. Results: In the first 30 days after acquisition of HIV, HIV-1 RNA levels varied greatly among participants (range, 27 200 to 1.6 x 10⁶ copies per mL of plasma). Levels of HIV-1 RNA decreased by a mean of 6.5% per week for the first 120 days and then increased by a mean of 0.15% per week. CD4 cell counts decreased by a mean of 5.2 cells/mm³ per week for the first 160 days and by a mean of 1.9 cells/mm³ per week thereafter (P< 0.01). Disease progressed faster in participants who sought medical care for their acute seroconversion syndrome (P = 0.01) and those who had high plasma HIV-1 RNA levels 120 to 365 days after acquisition (P < 0.01). Peak levels in the first 120 days were not predictive of disease progression. Conclusions: The variability in viral RNA levels associated with acute HIV-1 infection is greater than previously appreciated. Within 120 days of acquisition, plasma HIV RNA levels rapidly decrease to an inflection point, after which they gradually increase. Virus-host interactions soon after acquisition seem to have a major influence on the long-term outcome of HIV-1 disease.