Differences in early virus loads with different phenotypic variants of HIV-1 and SIVcpz in chimpanzees

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Abstract
Objective A comparative study of the replication kinetics of different HIV-1 variants (including SIVcpz) 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 SIVcpz−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 SIVcpz isolates. Results Important differences between early kinetics in the human lentivirus isolates as well as compared with the chimpanzee isolate SIVcpz−ant were observed. R5-dependent non-syncytium-inducing (NSI) isolates (5016, Ba-L, SIVcpz) 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 104 RNA equivalents/ml) in contrast to transient viraemia observed after infection with SI X4-utilizing isolates.