Intrapatient evolution of HIV-1 in the context of coreceptor usage

Sammanfattning: The variable region 1 to 3 (V1-V3) of the HIV-1 envelope plays an important role in coreceptor usage. Early in infection HIV- 1 is using CCR5 as coreceptor to enter target cells (R5 viruses) whereas viruses using CXCR4 as coreceptor (X4 viruses) may appear later in infection. This broadening or switch in coreceptor usage is associated with progression to AIDS. In my thesis work, we have compared the molecular evolution of V1-V3 between virus populations that maintained CCR5 coreceptor usage (non-switch populations, nSP) with virus populations that used CXCR4 as coreceptor (switch populations, SP). We also developed a novel biological cloning system. We found an increase in the number of potential N-linked glycosylation sites in V1 -V3 over time in nSP, while SP showed no change. Since glycans are an important defense against neutralizing antibodies, we hypothesize that the antibody response differed between patients with SP and nSP. We found that V2 length and evolution of V3 charge differed between R5 viruses from SP and nSP, already before coreceptor switch in SP. Therefore, these molecular properties could prove important for understanding, and maybe even for predicting, the evolution of coreceptor usage in HIV-populations. Due to the presence of the X4 subpopulations, SP evolved faster compared to nSP. In addition, R5 and X4 from SP were subjected to different selective pressures. We showed that R5 and X4 viruses recombine frequently. We hypothesize that such rearrangements may affect antibody recognition of X4 and allow for antibody escape and expansion of X4 subpopulations.