Genetic stability of foamy viruses: Long-term study in an African green monkey population

The genetic variability of the envelope surface domain (SU) of simian foamy virus (FV) of African green monkeys was studied. To assess the interindivi dual diversity of FV, isolates were obtained from 19 animals living togethe r in a monkey house. The monkeys had been imparted from Kenya prior to bein g placed in long-term housing in the research institute. In addition, a sim ian FV isolate and proviral DNA were obtained from an animal caretaker infe cted in this setting. DNA of the complete SU (1779 to 1793 bp) was analyzed by PCR and sequencing. The sequences revealed four clusters with high homo logies (>95%). Between the clusters, divergencies ranged from 3 to 25%. Obv iously, the clusters reflect four different strains or subtypes of simian F V type 3 that were prevalent in the colony. In contrast to lentiviruses, hy pervariable regions could not he detected in the FV SU. Furthermore, to ana lyze the intraindividual diversity of FV, we investigated the virus populat ion within an individual monkey at a given time point and its evolution ove r 13 years. For this purpose, 22 proviral SU clones generated by PCR from o ne oral swab and seven isolates obtained from the same animal between 1982 and 1995 were examined. These sequences revealed exceptionally high homolog y rates (99.5 to 100%), and only a minimal genetic drift was recognized wit hin the series of isolates. In conclusion, the low in vivo divergency of FV SU suggests that genetic variability is not important for the maintenance of FV persistence.