P06. Phenotypic co-receptor tropism and Maraviroc sensitivity in HIV-1 subtype C

Abu Bakar Siddik1, Alexandra Haas2, Wondwossen Amogne3, Soham Gupta1, Joelle Bader2, Thomas Klimkait2, Anders Sönnerborg1, Ujjwal Neogi1
Affiliates: 1Karolinska Institute, Stockholm, Sweden 2University of Basel, Basel, Switzerland 3Addis Ababa University, Ethiopia

Background
Genotypic tropism testing (GTT) for co-receptor usage is a recommended tool for clinical practice before administration of the CCR5-antagonist maraviroc. A replicative phenotypic tropism test (rPTT) revealed discordant results with GTT. Nearly all GTT tools have been developed with HIV-1B subtypes. However, the predictability in non-B subtypes have not been evaluated extensively. In this study we performed a comparative study between GTT and rPTT in HIV-1C and compared the data with HIV-1B and 01_AE. We also described the maraviroc susceptibility in the CCR5-tropic strains.

Method
Patient-derived gp120 of the respective HIV-1 env was cloned into a modified NL4-3 plasmid containing the luciferase gene inside the plasmid. One clone each from 31 HIV-1C infected patients and four strains from the EQAS panel with known phenotypes were dissected by rPhenotyping. Additionally, 68 clones from 18 patients (HIV-1B: 5, 01_AE: 6, HIV-1C: 7) were used to determine the PTT in the GHOST cell line expressing either CCR5 or CXCR4. The V3 sequences were obtained through Sanger Sequencing of the entire gp120 region and used for GTT. The PTT data were compared with several GTT tools. R5-tropic strains from HIV-1C (n=20) and non-C (HIV-1B and 01_AE; n=12) were used for maraviroc (obtained from NIH AIDS Reagent Program) sensitivity in the TZMbl cell line.

Results
Discordance was observed between GTT and PTT. The GTT falsely identified a higher proportion of X4-tropism in HIV-1C compared to PTT by both rPhenotyping and GHOST-cell assay. When multiple clones were tested in a subset of patients’ samples presence of both dual tropic and R5-tropic strains were observed in HIV-1C. Relatively higher EC50 values were observed for HIV-1C strains than for the non-C strains (p=0.002) indicating a reduced susceptibility against maraviroc.

Conclusion
The CXCR4 usage of HIV-1C seems to be generally overestimated when GTT tools based on HIV-1B are used. Also the sensitivity for maraviroc appears to be generally lower for HIV-1C than non-C viruses, which could possibly be explained by our earlier studies of a higher proportion of the maraviroc-relevant mutation A19T (>80%) in the envelope of HIV-1C. Further expanded knowledge about co-receptor usage in HIV-1C could be of value for better understanding the pathogenesis of HIV-1C, the most rapidly spreading subtype that dominates the global HIV-1 epidemic.

P6-Abu-bakar