HLA B57

About HLA B57

HLA B57 is an allele group of the HLA B gene, an MHC class I gene in the major histocompatibility complex on chromosome 6p21.33. The subtype HLA B5701 is strongly associated with hypersensitivity to abacavir, an antiretroviral drug used to treat HIV. The reaction, which affects a minority of people who receive abacavir and most commonly carriers of HLA B5701, causes fever, rash, gastrointestinal and respiratory symptoms, and can be life threatening if the drug is restarted. Abacavir binds within the peptide binding groove of HLA B5701 and changes the repertoire of self peptides it presents, triggering a T cell response. The association was reported in 2002, and a large randomized trial published in 2008 showed that screening for HLA B5701 before treatment greatly reduces hypersensitivity reactions. Pre treatment screening became standard practice and is one of the clearest successes of pharmacogenomics. HLA B5701 is also associated with flucloxacillin induced liver injury. Separately, HLA B57 is associated with better natural control of HIV, found at higher frequency among elite controllers, likely because it presents conserved viral peptides. Other well known HLA drug associations include HLA B1502 with carbamazepine induced Stevens Johnson syndrome in some Asian populations and HLA B5801 with allopurinol reactions.