PHARMACOGENETICS TESTING FOR HLA-B*57:01 ALLELE BY SCREENING ASSAYS AND HIGH RESOLUTION HLA-TYPING: RESULTS FROM A COMPLETE NATIONAL HIV COHORT, CROATIA

The HLA-B*57:01 allele is associated with hypersensitivity to the antiretroviral drug abacavir. Current HIV treatment guidelines recommend screening for HLA-B*57:01 before initiation of abacavir-containing regimen. The aim of this study was to determine the prevalence of HLA-B*57:01 in the Croatian HIV cohort. The study included all HIV-infected individuals receiving clinical care at the Croatian Reference center for HIV/AIDS, University Hospital for Infectious Diseases, Zagreb, Croatia in the period 2009-2017, 1288 in total. HLA-B*57:01 typing was performed by using PCR:SSO reverse hybridization method and PCR-SSP high resolution typing only for ambiguous HLA-B*57:01/*57:06 samples in the period 2009-2012, while starting from January 2013 the typing method was switched to Real-Time PCR. HLA-B*57:01 allele was detected in 65 of 1288 (5.1%) HIV-infected individuals, revealing the HLA-B*57:01 allele frequency of 2.5%. The HLA B*57:01 frequency in positive HIV infected  male individuals (2.6%) was concordant with the frequency in the general Croatian population, as well as with the frequency in the entire group of HIV-positive individuals from Croatia, while HIV infected women showed somehow lower frequency of HLA B*57:01 allele (1.5%). No clinical events associated with abacavir hypersensitivity have been observed since the introduction of the prospective HLA-B*57:01 screening, while two non-fatal cases of hypersensitivity were observed prior to introduction of the screening.