Differential effects of the G118R, H51Y, and E138K resistance substitutions in different subtypes of HIV integrase.

UNLABELLED: Dolutegravir (DTG) is the latest antiretroviral (ARV) approved for the treatment of human immunodeficiency virus (HIV) infection. The G118R substitution, previously identified with MK-2048 and raltegravir, may represent the initial substitution in a dolutegravir resistance pathway. We have found that subtype C integrase proteins have a low enzymatic cost associated with the G118R substitution, mostly at the strand transfer step of integration, compared to either subtype B or recombinant CRF02_AG proteins. Subtype B and circulating recombinant form AG (CRF02_AG) clonal viruses encoding G118R-bearing integrases were severely restricted in their viral replication capacity, and G118R/E138K-bearing viruses had various levels of resistance to dolutegravir, raltegravir, and elvitegravir. In cell-free experiments, the impacts of the H51Y and E138K substitutions on resistance and enzyme efficiency, when present with G118R, were highly dependent on viral subtype. Sequence alignment and homology modeling showed that the subtype-specific effects of these mutations were likely due to differential amino acid residue networks in the different integrase proteins, caused by polymorphic residues, which significantly affect native protein activity, structure, or function and are important for drug-mediated inhibition of enzyme activity. This preemptive study will aid in the interpretation of resistance patterns in dolutegravir-treated patients. IMPORTANCE: Recognized drug resistance mutations have never been reported for naive patients treated with dolutegravir. Additionally, in integrase inhibitor-experienced patients, only R263K and other previously known integrase resistance substitutions have been reported. Here we suggest that alternate resistance pathways may develop in non-B HIV-1 subtypes and explain how "minor" polymorphisms and substitutions in HIV integrase that are associated with these subtypes can influence resistance against dolutegravir. This work also highlights the importance of phenotyping versus genotyping when a strong inhibitor such as dolutegravir is being used. By characterizing the G118R substitution, this work also preemptively defines parameters for a potentially important pathway in some non-B HIV subtype viruses treated with dolutegravir and will aid in the inhibition of such a virus, if detected. The general inability of strand transfer-related substitutions to diminish 3' processing indicates the importance of the 3' processing step and highlights a therapeutic angle that needs to be better exploited.

Exposure to entry inhibitors alters HIV infectiousness and sensitivity to broadly neutralizing monoclonal antibodies.

BACKGROUND: The development of envelope-specific neutralizing antibodies that can interfere with viral entry into target cells is important for the development of an HIV-1 vaccine. Another means of blocking viral entry is through the use of entry inhibitors such as the CCR5 inhibitor maraviroc (MVC), which can also repel cell-free virus particles from the cell surface. For this reason, we hypothesized that exposure to entry inhibitors might alter viral infectiousness and sensitivity to antibody-mediated neutralization. METHODS: The CCR5-tropic HIV-1 variants BaL, AD8, and CC 1/85 were used to infect PM-1 cells in the presence of 2 entry inhibitors, enfuvirtide and MVC. After 4 hours, culture fluids were ultrafiltered and the infectiousness and susceptibility to broadly neutralizing antibodies (2F5, 4E10, 2G12, b12, VRC01, PG9) of viruses exposed to these entry inhibitors were assessed using TZM-bl cells. RESULTS: Viruses exposed to the entry inhibitor MVC exhibited lower infectiousness than controls. Enfuvirtide exposure increased AD8 sensitivity to 2F5, 4E10, VRC01, and b12 and increased BaL sensitivity to 4E10 while lowering BaL sensitivity to b12 and VRC01. MVC-exposed BaL became less susceptible to the gp120-specific antibodies b12, 2G12, and VRC01. CONCLUSIONS: Exposure to entry inhibitors altered HIV-1 infectiousness and sensitivity to gp120-specific neutralizing antibodies. This alteration of entry inhibitor-exposed virus has implications for the development of future entry inhibitors and for vaccine development.