Effect of HIV-1 Integrase Resistance Mutations When Introduced into SIVmac239 on Susceptibility to Integrase Strand Transfer Inhibitors

Abstract

Studies on the in vitro susceptibility of SIV to integrase strand transfer inhibitors (INSTIs) have been rare. In order to determine the susceptibility of SIVmac239 to INSTIs and characterize the genetic pathways that might lead to drug resistance, we inserted various integrase (IN) mutations that had been selected with HIV under drug pressure with raltegravir (RAL), elvitegravir (EVG), and dolutegravir (DTG) into the IN gene of SIV. We evaluated the effects of these mutations on SIV susceptibility to INSTIs and on viral infectivity. Sequence alignments of SIVmac239 IN with various HIV-1 isolates showed a high degree of homology and conservation of each of the catalytic triad and the key residues involved in drug resistance. Each of the G118R, Y143R, Q148R, R263K, and G140S/Q148R mutations, when introduced into SIV, impaired infectiousness and replication fitness compared to wild-type virus. Using TZM-bl cells, we demonstrated that the Q148R and N155H mutational pathways conferred resistance to EVG (36-and 62-fold, respectively), whereas R263K also displayed moderate resistance to EVG (12-fold). In contrast, Y143R, Q148R, and N155H all yielded low levels of resistance to RAL. The combination of G140S/Q148R conferred highlevel resistance to both RAL and EVG (>300-and 286-fold, respectively). DTG remained fully effective against all site-directed mutants except G118R and R263K. Thus, HIV INSTI mutations, when inserted into SIV, resulted in a similar phenotype. These findings suggest that SIV and HIV may share similar resistance pathways profiles and that SIVmac239 could be a useful nonhuman primate model for studies of HIV resistance to INSTIs. IMPORTANCEThe goal of our project was to establish whether drug resistance against integrase inhibitors in SIV are likely to be the same as those responsible for drug resistance in HIV. Our data answer this question in the affirmative and show that SIV can probably serve as a good animal model for studies of INSTIs and as an early indicator for possible emergent mutations that may cause treatment failure. An SIV-primate model remains an invaluable tool for investigating questions related to the potential role of INSTIs in HIV therapy, transmission, and pathogenesis, and the present study will facilitate each of the above.

Characterization of the Drug Resistance Profiles of Integrase Strand Transfer Inhibitors in Simian Immunodeficiency Virus SIVmac239

“…Previous reports by our group and others have shown that INSTIs are capable of inhibiting SIV/simian-tropic HIV (stHIV) replication and infectivity in tissue culture (12)(13)(14). We and others have also shown that INSTIs exhibit potent antiviral activity against SIV in tissue culture studies and in vivo with inhibitory concentrations in the nanomolar range; moreover, SIV that was mutated in IN displayed resistance profiles similar to those of HIV (12)(13)(14).…”

“…The latter substitution has been shown to increase the solubility of recombinant integrase without changing its activity in vitro (18,19). The primer pairs used for site-directed mutagenesis to produce the G118R, G140S, Y143R, Q148R, N155H, and R263K mutations have been described previously (12). The primer pairs for other desired mutations in this study (i.e., E92Q, T97A, and F185H) are described in Table 1.…”

“…Rhesus macaque peripheral blood mononuclear cells (PBMCs) were isolated using Ficoll-Hypaque (GE Healthcare) and stimulated with 10 g/ml phytohemagglutinin A (Invitrogen) and 20 U/ml of human interleukin-2 (IL-2) (Roche). PBMCs were cultured as previously described (12). Merck & Co., Inc., Gilead Sciences, Inc., and ViiV Healthcare, Ltd., kindly supplied raltegravir (RAL), elvitegravir (EVG), and dolutegravir (DTG), respectively.…”

“…We and others have also shown that INSTIs exhibit potent antiviral activity against SIV in tissue culture studies and in vivo with inhibitory concentrations in the nanomolar range; moreover, SIV that was mutated in IN displayed resistance profiles similar to those of HIV (12)(13)(14).…”

Differential Effects of the G118R, H51Y, and E138K Resistance Substitutions in Different Subtypes of HIV Integrase

“…Thus, it is more difficult to develop resistance to DTG. There is growing evidence that G118R and R263K are two mutations that can engender resistance to DTG (16-19, 37, 41, 46), and both substitutions have also been shown to engender INSTI resistance in simian immunodeficiency virus (47). In this context, minor polymorphisms that vary among subtypes may be able to play a major role in the development of drug resistance.…”