LAUSR

Identification of CD8+ T lymphocyte (CTL) escape mutations that compromise the pathogenic functions of the Nef protein may be relevant for an HIV‐1 attenuation‐based vaccine. Previously, HLA‐associated mutations 102H, 105R, 108D, and 199Y were individually statistically associated with decreased Nef‐mediated HLA‐I downregulation ability in a cohort of 298 HIV‐1 subtype C infected individuals. In the present study, these mutations were introduced by site‐directed mutagenesis into different patient‐derived Nef sequence backgrounds of high similarity to the consensus C Nef sequence, and their ability to downregulate HLA‐I was measured by flow cytometry in a CEM‐derived T cell line. A substantial negative effect of 199Y on HLA‐I downregulation and Nef expression was observed, while 102H and 105R displayed negative effects on HLA‐I downregulation ability and Nef expression to a lesser extent. The total magnitude of CTL responses in individuals harboring the 199Y mutation was lower than those without the mutation, although this was not statistically significant. Overall, a modest positive relationship between Nef‐mediated HLA‐I downregulation ability and total magnitude of CTL responses was observed, suggesting that there is a higher requirement for HLA‐I downregulation with increased CTL pressure. These results highlight a region of Nef that could be targeted by vaccine‐induced CTL to reduce HLA‐I downregulation and maximize CTL efficacy.