Increased replication capacity following evolution of PYxE insertion in Gag-p6 is associated with enhanced virulence in HIV-1 subtype C from East Africa

Background: A lower virulence of HIV-1 subtype C (HIV-1C) is suggested to be related to the global dominance of HIV-1C. In this observational study, combining in vivo (clinical monitoring) and in vitro (genotypic, biochemical, and phenotypic assays), we explored whether HIV-1C from East Africa (HIV-1C(EA)) is more pathogenic due to the evolution of a PYxE-insertion (C-PYxEi) in the gag-p6 that also could affect the therapy response. Methods: HIV-1B (n=112) and HIV-1C(EA) (n=128)-infected individuals residing in Sweden were analyzed with regard to Gag-p6 genotype and clinically monitored. Based on the Gag-p6 characteristics, three HIV-1C(EA) and one HIV-1B patient-derived p2-INT-recombinant virus (gag-p2/NCp7/p1/p6/pol-PR/RT/IN) were constructed to analyze viral growth kinetics (VGKs) and drug sensitivity assays. Reverse transcriptase (RT) from the same samples was cloned into the heterodimer expression plasmid (pRT6H-PROT) to analyze catalytic efficiency of RT. Results: A higher viral failure rate and lower pre-therapy CD4(+) T-cell counts were observed in HIV-1C(EA)-infected patients compared to HIV-1B-infected patients. In Gag-p6, PTAP-duplication was more common in HIV-1C. HIV-1C(EA)-infected patients with signature C-PYxEi,C- evidenced very low pre-therapy CD4(+) T-cell counts and suboptimal gain in CD4(+) T-cells following therapy, as compared to the non-C-PYxEi-strains indicating higher virulence. VGKs showed a statistically significant higher replication capacity (RC) for the C-PYxEi viruses than the other two non-C-PYxEi strains. No statistically significant difference was observed in the catalytic efficiency among HIV-1C RTs. Conclusions: This is the first evidence of polymerase independent increased virulence and RC in HIV-1C(EA) following PYxE-insertion that is associated with suboptimal CD4(+) T-cell gain following therapy initiation. J. Med. Virol. 89:106-111, 2017. (c) 2016 Wiley Periodicals, Inc.