Objective: A comparative study of the replication kinetics of different HIV-1 variants (including SIV(cpz)) was undertaken to determine which viral characteristics were associated with sustained plasma viraemia in chimpanzees.
Design: Plasma samples from chimpanzees infected with six different HIV-1 clade B isolates were compared with plasma samples from SIV(cpz-ant)-infected chimpanzees.
Methods: A pan-clade quantitative competitive reverse transcriptase-polymerase chain reaction assay was developed based on conserved primer sequences recognizing M, N and O human lentiviruses as well as different SIV(cpz) isolates.
Results: Important differences between early kinetics in the human lentivirus isolates as well as compared with the chimpanzee isolate SIV(cpz-ant) were observed. R5-dependent non-syncytium-inducing (NSI) isolates (5016, Ba-L, SIV(cpz)) were found to have relatively higher viral loads than the syncytium-inducing (SI), X4-dependent primary (SF2), T cell-adapted (IIIB) or X4/R5 (Han2, DH12) SI primary isolates.
Conclusion: Infection of chimpanzees with NSI R5-utilizing isolates correlated with persistent viraemia (approximately 10(4) RNA equivalents/ml) in contrast to transient viraemia observed after infection with SI X4-utilizing isolates.