Rapid clearance of simian immunodeficiency virus particles from plasma of rhesus macaques

Perturbation of the equilibrium between human immunodeficiency virus type 1 (HIV-1) and the infected host by administering antiretroviral agents has r evealed the rapid turnover of both viral particles and productively infecte d cells. In this study, we used the infusion of simian immunodeficiency vir us (SIV) particles into rhesus macaques to obtain a more accurate estimate of viral clearance in vivo. Consistently, exogenously infused virions were cleared from plasma with an extremely short half-life, on the order of minu tes (a mean of 3.3 min). This new estimate is similar to 100-fold lower tha n the upper bound of 6 h previously reported for HIV-1 in infected humans. In select animals, multiple tissues were collected at the completion of eac h experiment to track the potential sites of virion clearance. Detectable l evels of SIV RNA were found in lymph nodes, spleen, lungs, and liver, but n ot in other tissues examined. However, only similar to 1 to 10% or less of the infused virions were accounted for by the thorough tissue sampling, ind icating that the vast majority of the infused particles must have been degr aded over a short period of time. Should the rapid clearance of virions des cribed here be applicable to infected patients, then HIV-I production and t hus the number of productively infected CD4(+) T lymphocytes or the viral b urst size must be proportionally higher than previous minimal estimates.