The results of a multicenter study, involving Japanese researchers at the University of Kumamoto directed by Professors Yuka Kawashima and Masafumi Takiguchi, and on how HIV adapts to the human leukocyte antigen (HLA) class I have recently been published. Researchers found a correlation between the prevalence of certain HLA alleles in a population and the frequency of certain mutations exhaust. HLA genes, located on chromosome 6, encode proteins whose role is to bind to peptide fragments and present them to immune cells. If they identify the fragments as foreign to the organism, the specific immune response (i.e. antibody production, the proliferation

of killer cells ...) is triggered. A mutation exhaust the virus not be detected by this system. This study confirms, if needed, the importance of multicenter studies within the framework of international cooperation. In fact, it covers 9 cohorts spread over 8 countries, including Japan, involving about 2900 patients with HIV, mostly in chronic phase of infection. For each of them, the viral RNA and HLA genes have been sequenced. The analysis focused on 14 mutations of the virus well documented. The results revealed a positive correlation between prevalence of HLA alleles in a population and frequency of the mutation associated exhaust. The study, however, that these links can be more complex. Among other things, several alleles may be associated with a single mutation. This study has important implications not only in the field of therapy, but also in the prevention, highlighting the difficulties of developing an effective vaccine. In addition, past work had shown that the presence of certain HLA alleles in a patient corresponded to a slower progress of the disease. According to the study, resistance to the progression of infection conferred by the possession of these alleles may diminish as the pandemic continues and that the escape mutations become more frequent in a given population.