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A single dose of an HIV-specific, vaginally-applied microbicide, PSC-RANTES (PSC) can select for a drug resistant SHIV in a macaque model
Presented by Eric Arts, United States.
Moore D.1, Veazey R.2, Arts E.1
1Case Western Reserve University, Medicine, Cleveland, United States, 2Tulane National Primate Research Center, Division of Comparative Pathology, New Orleans, United States
Objectives: PSC binds to CCR5 and is a potent inhibitor of HIV-1 entry. In a vaginal treatment/exposure model, high dose PSC (1 mM) prevents infection by SHIV_SF162P3 in macaques. Incomplete protection was observed with reduced PSC concentrations. In this study, we analyzed drug sensitivity and fitness of SHIVs establishing macaque infections in presence of PSC.
Methods: Viral RNA was extracted from at least five longitudinal plasma samples of twelve infected rhesus macaques treated ± PSC. Env cDNA was PCR amplified, sequenced, and aligned to env sequence of the inoculating SHIVP3. Identification of any mutation, not found in untreated control animals, led to clonal sequencing analyses. Frequency of selected mutations was estimated in the inoculating population of SHIVP3 by an radiolabeled oligonucleotide ligation assay. Env genes with selected mutations were then cloned into NL4-3 to examine sensitivity of NL4-3/SHIVenv chimeric viruses to entry inhibitors. Finally, replicative fitness of these SHIVenv chimeric viruses was measured ± selected mutations in competition assays.
Results: Few amino acid substitutions were observed in the SHIVenv gene of these infected, PSC-treated macaques. One macaque (100 uM PSC) was infected with a variant harboring K311R in the V3 crown and N631D in gp41; mutations found at less than 0.4% in the inoculating SHIVP3. This M584 SHIVenv gene (K311R/N631D) as compared to SHIVP3env in NL4-3 displayed a >10-fold resistance to PSC in a cell line expressing either human or rhesus CCR5. These PSC resistance mutations did not result in virus with reduced replicative fitness.
Conclusions: This is the first identification and characterization of a resistant virus selected with anti-HIV microbicide in a macaque model. Given the low SHIVP3 genetic diversity as compared to inoculating HIV-1 in human transmissions, this >1000-fold selection may be problematic for future microbicide trials. In addition, the infecting SHIVenv did not suffer a fitness loss associated with PSC-resistant mutations.
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