Mc. Mullertrutwin et al., THE EVOLUTIONARY RATE OF NONPATHOGENIC SIMIAN IMMUNODEFICIENCY VIRUS (SIVAGM) IS IN AGREEMENT WITH A RAPID AND CONTINUOUS REPLICATION IN-VIVO, Virology, 223(1), 1996, pp. 89-102
African green monkeys (AGMs) are divided into four species (Cercopithe
cus aethiops, C. pygerythrus, C. sabaeus, C. tantalus), each harboring
a species-specific simian immunodeficiency virus (SIVagm). Little is
known about the host and/or viral factors that are responsible for the
apathogenicity oi SIVagm infections in their natural hosts. In order
to analyze the specific selective pressures exerted by the host on the
virus in vivo, we compared the genetic evolution of SIVagm.tan in its
natural host (C. tantalus) and in a foreign host species (Erythrocebu
s patas), in which we could obtain a reproducible and persistent infec
tion by SIVagm.tan, As in AGMs, patas monkeys do not develop any disea
se following SIVagm infection. Our longitudinal study in env (V3-C3-V4
-C4-V5) of SIVagm.tan from three AGMs and three patas monkeys revealed
a high ratio of synonymous to nonsynonymous mutation frequencies (1.5
-6.2). These data indicate that the selective pressures for stability
exerted by AGMs and patas monkeys on SIVagm override positive selectio
n for change reported in pathogenic HIV-1 infections. The rapid accumu
lation of mutations observed in AGMs and patas monkeys (0.4-7.2 x 10(-
2) nucleotide substitutions per site per year) suggests a continuous r
eplication of SIVagm viruses in vivo. We thus propose that nonpathogen
ic SIVagm infections are the result of a long-term selection of SIVagm
variants whose dissemination can be controlled in the host, rather th
an being explained by a low ability of the virus to replicate in vivo.
(C) 1996 Academic Press, Inc.