アクティブボード・２０１４年１１月
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研究発表を行った学会；
・15th Kumamoto AIDS seminar
　２０１４年１０月２日〜４日（熊本）

タイトル；Naturally-isolated HIV-1 Nef differentially recognize the cytoplasmic tails of HLA-A and HLA-B molecules for down-regulation.
発表者；Macdonald Mahiti　氏
　　　（熊本大学　エイズ学研究センター　上野　研究室）
Abstract；
HLA class I-restricted T lymphocyte responses are important in immune control of HIV-1 infection. Nonetheless, an accessory protein Nef aids HIV-1 to evade from such host immunity by differentially recognizing cytoplasmic tails of HLA-A and HLA-B, but not HLA-C for down-regulation. However, these observations were made only with a limited number of prototypic laboratory strains. Considering highly variable nature of Nef proteins in vivo, we wanted to examine the down-regulation activity of HLA-A and HLA-B by more diverse clinically-isolated Nef variants. To test this, we recruited 46 treatment-naïve, subtype-B chronically HIV-infected subjects and constructed recombinant viruses expressing patient-derived Nef clones. Resultant viruses were used to infect HLA-deficient 721.221 cells engineered to stably express either HLA-A*24, HLA-B*35 or HLA-Cw*04, followed by analysis of cell surface expression levels of HLA class I molecules by flow cytometry. HLA-B showed more resistance to Nef-mediated down-regulation compared to HLA-A (p<0.001); whereas, no Nef clone observed to down-regulate HLA-C. The pairwise analysis revealed the Nef polymorphisms at positions 158 and 202 being associated with differential HLA-A/B recognition (p<0.001). In site-directed mutagenesis at NefSF2, amino acid variations at Nef-202, but not at 158, affect selective down-regulation activity of HLA-A and HLA-B. We further examined the effects of these mutations on other HLA-I allotypes; Nef-202 residues differentially recognise the cytoplasmic tail of the HLA-A allotype with less effect to HLA-B. Furthermore, the role of Nef-202 was also supported in the molecular modeling study. Together, our results indicate how Nef differentially recognizes cytoplasmic tails of HLA-A and HLA-B for down-regulation, providing us with further insights into importance of Nef-mediated HLA-I down-regulation on modulation of host cellular immune responses by HIV-1.