SrR-Elegant studies using early, frequently sampled patients on nevirapine and protease inhibitors (ABT-538 and L-735.524) have now made it possible to calculate the rapid turnover of HIV-1 virions in infected patients1• 2: the rate of plasma retroviral decay revealed a half-time of about 2 days for free virus particles or virus-producing cells, indicating that about 30% of the plasma virus population in infected patients is replaced every day, These observations have important implications for our understanding of HIV pathogenesis, and here, using a similar analysis in our previously analysed cohort of 11 AZT-treated patients3-5, we confirm the earlier findings1• 2• Our patients were homosexual men with CDC group IV disease, who have

Hence the estimated half-time, being a function of the survival of virus particles in the serum and the decay of virus-producing cells, can represent only the upper limit of viral half-time, assuming immediate and absolute inhibition of viral synthesis, which would seem implausible. The table shows the analysis of our patients. For each patient the initial viral load (in copies per ml), the minimum virus load (and the day when it was reached), the rate of decline, the daily turnover, the half-life time and the data points used for the fit of the exponential decay curve are shown. The average rate of virus decline is 0.46±0.31 (days), the daily turnover is 35±17%, and the half-life time is 1.9±1.1 days.(For these averages we leave out patient 1, who never achieved a 50% decline in serum viral load and whose viral half-life time is about 9 standard deviations