HIV‐1 group O integrase displays lower susceptibility to raltegravir and has a different mutational pathway for resistance than HIV‐1 group M

HIV‐1 group O (HIV‐O) is a rare HIV‐1 variant characterized by a high number of polymorphisms, especially in the integrase gene, e.g. positions L74I, S153A, G163Q and T206S. As HIV‐O integrase enzymes have not previously been studied, our aim was to assess the impact of HIV‐O integrase polymorphisms on susceptibility to integrase inhibitors and emergence of resistance associated mutations. Viruses and Methods We cloned and purified integrase proteins from each of HIV‐1 Group O clades A (HIV‐O/A) and B (HIV‐O/B), a HIV‐O divergent strain (HIV‐O/Div), and HIV‐1 group M (subtype B, HIV‐M/B) and characterized these enzymes for susceptibility to integrase strand transfer inhibitors (INSTIs) in cell‐free assays and in tissue culture, in the absence or presence of varying concentrations of several INSTIs. The inhibition constant (Ki) and IC50 were calculated and compared for HIV‐M and HIV‐O integrases. Selections for resistance‐related mutations were performed using cord blood mononuclear cells and increasing concentration of INSTIs. Results HIV‐O integrase and viruses were more susceptible to raltegravir (RAL) in competitive inhibition assays and in tissue culture than were HIV‐M enzymes and viruses, respectively. During selection, we observed different pathways of resistance depending on the drug and clade. Mutations selected in HIV‐O can be classified as follows: (1) mutations described for HIV‐M such as T97A, Q148R, V151A/I (RAL), T66I, E92Q, E157Q (EVG) and M50I, R263K (DTG) and (2) signature mutations for HIV‐O (i.e. not described in HIV‐M) F121C (HIV‐O/B for RAL), V75I (HIV‐O/A for RAL) and S153V (HIV‐O/A for DTG). Only the HIV‐O/Div selected the Q148R mutation for RAL and R263K+M50I for DTG, as previously described for HIV‐M. None of the HIV‐O viruses selected either N155H or Y143C. The selection of the specific S153V mutation could be explained at the nucleotide level: HIV‐O at this position contains an alanine and substitution of alanine to valine (153AGGC→153VGTC) is easier than substitution of alanine to tyrosine (153AGGC→153YTAC), with only a transversion needed instead of one transition plus one transversion. Conclusions This is the first report of susceptibility and resistance in vitro to INSTIs for HIV‐O. Our study confirmed the impact of HIV‐O polymorphism, on susceptibility to INSTIs and the emergence of resistance mutations.