Association of viral hepatitis A with HLA-A9

HLA-A and B phenotyping was carried out, during a viral hepatitis A (VHA) epidemic in Brazil, on 47 unrelated patients with VHA and 53 unrelated healthy subjects of the same age, sex, social status, and ethnic origin. An increased frequency of HLA-A9 (44.7% vs. 15.1%) and a decrease of that of HLA-A3 (2.1% vs. 22.6%) were observed when compared with controls. After correction for the number of antigens tested, only the positive association with HLA-A9 was observed. It was found that the relative risk for an HLA-A9 carrier to develop VHA was 4.5.