Positive association of DRB1 04 and DRB1 15 alleles with Fya immunization in a Southern European population.

BACKGROUND: Anti-Fy(a) has been implicated in hemolytic transfusion reactions. However, not all Fy(a-) patients develop anti-Fy(a) after transfusion with 1 unit of blood [Fy(a+)]. This study was designed to identify HLA-DRB1 alleles associated with a predisposition to Fy(a) immunization after blood transfusion. STUDY DESIGN AND METHODS: To identify HLA-DRB1 alleles prone to immunization after blood transfusion or pregnancy, HLA-DRB1 genotyping using polymerase chain reaction with sequence-specific oligonucleotide nonradioactive probe/sequence-specific priming methods was performed on blood samples from 67 immunized patients and 200 unrelated controls from the same southern European population in a case-control retrospective study. RESULTS: Ninety-six percent of patients with anti-Fy(a) had at least one HLA-DRB1 04 or HLA-DRB1 15 allele compared to 34% of controls (p(c) < 0.001). Furthermore HLA-DRB1 04 and HLA-DRB1 1501 frequencies were significantly increased in Fy(a)-immunized patients (35% vs. 12%, p(c) < 0.001; and 30% vs. 19%, p(c) < 0.001, respectively). Among HLA-DRB1 04 allelic subtypes, DRB1 0401 and DRB1 0403 alleles were more strongly correlated with Fy(a) immunization (51% vs. 24% and 19% vs. 9%; p(c) < 0.001, respectively). CONCLUSIONS: This study indicated that HLA-DRB1 04 and DRB1 1501 are overrepresented in Fy(a)-immunized patients. The correlation between these alleles and Fy(a) immunization could be due to a particular presentation of the Fy(a) peptide in HLA-DRB1 molecules.

A new HCV core antigen assay based on disassociation of immune complexes: an alternative to molecular biology in the diagnosis of early HCV infection.

BACKGROUND: An EIA based on immune complex disassociation of nucleocapsid proteins of HCV has been developed to detect and quantify HCV core antigen. STUDY DESIGN AND METHODS: To evaluate whether this new assay (trak-C, Ortho Clinical Diagnostics) could be an alternative to NAT during the window period, its sensitivity in this context was assessed, and its performance was compared with that of a first-generation HCV core antigen assay dedicated to the blood screening (HCV core antigen ELISA). Studied populations included nine HCV RNA-positive, HCV antibody-negative blood donors and 23 hemodialysis patients who underwent an HCV seroconversion. From these individuals, 81 samples (23 HCV RNA-negative and 58 HCV RNA-positive) sequentially collected during the phase before seroconversion were tested. RESULTS: The nine blood donor samples were positive for the presence of HCV core antigen by the trak-C, and 6 of 8 tested were positive for the presence of HCV core antigen by blood screening ELISA. In the hemodialysis cohort, the 23 HCV RNA-negative samples were negative with the two HCV core antigen assays. Among the 58 HCV RNA-positive samples, 46 of 57 (80.7%) tested were positive for the presence of HCV core antigen with the blood screening assay, and 57 of 58 (98.2%) were positive for the presence of HCV core antigen with the trak-C. The mean delays in detecting HCV infection between trak-C and the appearance of HCV antibodies, between HCV RNA testing and trak-C, and between trak-C and HCV core antigen ELISA were 58.2, 0.24, and 3.33 days, respectively. CONCLUSION: Trak-C was more sensitive than the blood screening assay and had similar performance to HCV RNA assay in the window period. Trak-C could constitute an alternative to NAT for the diagnosis of HCV infection during the window period, especially when molecular biology procedures cannot be implemented.