Influence of HLA-DR phenotype on the risk of hepatitis C virus-associated mixed cryoglobulinemia

Objective. Circumstances predisposing hepatitis C virus (HCV)-infected pati ents to develop mixed cryoglobulinemia (NIC), which may manifest as a small -vessel systemic vasculitis (NIC vasculitis), remain unclear. Previous stud ies have failed to demonstrate a clear role of either viral factors (genoty pe, viral load) or host factors (lymphocytes or immunoglobulin subsets). Th is study was undertaken to examine a possible role of HLA class II alleles in HCV-associated MC. Methods. One hundred fifty-eight HCV-infected patients, of whom 76 had MC ( 56 with type II MC and 20 with type III MC) and 82 did not have NIC, were s tudied prospectively. NIC vasculitis was noted in 35 HCV-infected patients with type II IgM kappa -containing cryoglobulins. HLA-DRB1 and HLA-DQB1 pol ymorphism was analyzed by hybridization using allele-specific oligonucleoti des, after gene amplification. The odds ratio (OR) was calculated with Wool f's method. Then, using multivariate analysis, demographic, biologic, immun ologic, virologic, and liver histologic factors associated with the presenc e of MC and MC vasculitis were investigated. Results. HLA-DR11 was significantly, more frequent in patients with type II MC than in those without MC (41.1% versus 17.1%, OR 3.4, corrected P [P-co rr] = 0.017), regardless of the presence of vasculitis accompanying the MC (37.1% of those with MC vasculitis, 34.1% of those with MC but no vasculiti s). HLA-DR7 was less frequent in HCV-infected patients with MC than in thos e without MC (13.2% versus 30.5%; OR 0.34, P = 0.012, P-corr not significan t), with a particularly lower frequency in those with type II MC and those with MC vasculitis (12.5% and 8.6%, respectively). There was no significant difference in HLA-DQB1 distribution between the different patient groups. By univariate and multivariate analysis, HLA-DR11 was the only positive pre dictive factor, besides female sex and advanced age, for the presence of MC and HCV-associated MC vasculitis (OR 2.58). Conclusion. Our results indicate that the presence of the DR11 phenotype is associated with a significantly increased risk for the development of type II MC in patients with chronic HCV infection. In contrast, HLA-DR7 appears to protect against the production of type II MC. These results suggest tha t the host's immune response genes may play a role in the pathogenesis of H CV-associated MC.