271 Use of CCR5/CXCR4 Chimeric Receptors Reveal Evolution of HIV-1 R5 Phenotype in Relation to Pathogenesis E. M. Fenyö*1, I. Karlsson1, L. Antonsson1, Y. Shi2, A. Karlsson3, J. Albert2, B. Olde1, C. Owman1 1Lund Univ, Lund, Sweden; 2Karolinska Inst, Stockholm, Sweden; and 3South Hosp, Stockholm, Sweden
Background: Co-receptor use of HIV-1 may influence the type of cells infected and the signal pathways activated. To understand the linkage between co-receptor use and the severity of the pathogenic process following HIV-1 infection, we tested 278 HIV-1 isolates from 23 individuals with varying severity of HIV-1 infection, for co-receptor use.
Methods: Co-receptor use was tested by infection of human cell lines (U87.CD4 and GHOST[3]) engineered to express CD4 and the chemokine receptors CCR1, CCR2b, CCR3, CCR5, CXCR4, CXCR6 (formerly Bonzo/strl33) and the orphan receptor BOB. In addition, chimeric receptors, where successively larger parts of CCR5 have been systematically exchanged for CXCR4, were constructed and expressed in U87.CD4 cells.
Results: Three (3) patterns were distinguished: no evolution, evolution to CXCR4 use, and fluctuation. No evolution with stable CCR5 use (R5 phenotype) was linked to slow progression. Virus isolations from single individuals as frequent as 1 month or less yielded viruses with diverse biological phenotypes. Differences were further dissected by testing a series of CCR5/CXCR4 chimeric receptors. Mono-tropic R5 or X4 viruses were more selective in use of the chimeric receptors than R5X4 or multi-tropic viruses. Most importantly, the efficiency of chimeric receptor use by sequential isolates increased over time. In particular, increase in the capacity of R5 viruses to use chimeric receptors preceded switch to CXCR4 use.
Conclusions: The increase in efficiency of chimeric receptor use allows a new interpretation of evolution of HIV-1 co-receptor use, such that evolution appears to be a continuous process that may lead to changes in the mode of co-receptor use, with the potential of profound alteration in signaling at that receptor.
