Specific passage of simian immunodeficiency virus from end-stage disease results in accelerated progression to AIDS in rhesus macaques

To determine whether passage of late-stage variants of simian immunodeficie ncy virus (SIV) would lead to a more virulent infection and rapid disease p rogression, a study was designed to examine the effects of selective transm ission of SIV from late-stage cases of AIDS in Macaca mulatta, In a uniform group of 10 age-matched animals from the same genetic breeding stock infec ted with SIVB670, it took 7 months before one of the ten animals developed AIDS. Passage of virus taken from this animal immediately prior to death re sulted in death of the recipient due to AIDS within 4 months. Again, subseq uent passage of virus taken late in disease resulted in an accelerated dise ase course, with AIDS developing within 2.5 and 1.8 months in two recipient s. The fourth passage of virus taken late in disease from the most rapid pr ogressor (1.8 months) resulted in AIDS developing in this recipient within 1 month of infection. During each consecutive passage in vivo, the loss of memory T cells became more acute. Evidence that the virus became more virul ent with selective passage of late-stage variants was provided by the marke dly increased levels of both plasma antigen and viral RNA. Subsequent in vi vo passage from end-stage AIDS selected for a strain of SIV capable of caus ing the acute development of AIDS as rapidly as 1 month postinfection. The pathology of acute AIDS in these cases closely resembled that seen after a chronic disease course.