High virus loads in naturally and experimentally SIVagm-infected African green monkeys

A quantitative RT-PCR assay was developed for SIVagm and was used to measur e the levels of viral RNA in the plasma of experimentally and naturally inf ected African green monkeys. The number of productively infected PBMCs and the number of cells carrying integrated provirus were also measured. Plasma virus loads in experimentally infected animals peaked at e weeks postinfec tion, ranging from 2.9 x 10(5) to 4.2 X 10(7) RNA copies/ml plasma. Set poi nts of 2.1 x 10(3) to 2.8 x 10(6) RNA copies/ml plasma were maintained for one year. Similarly, the number of cells carrying integrated SIVagm proviru s remained relatively stable in individual animals for one year with set po ints ranging from 73 to 810 proviral copies per 10(8) PBMC. However, the nu mber of productively infected cells fluctuated considerably during this per iod. Virus loads in the 26 naturally infected AGMs ranged from 8.3 x 10(3) to 1.1 x 10(7) (mean 1.7 x 10(8)) RNA copies/ml plasma. These levels of vir emia are similar to those seen in pathogenic systems (HIV-1, SIVmac), indic ating that control of SIVagm replication is not the reason for the natural host's resistance to disease progression. (C) 2001 Academic Press.