MEASUREMENT OF ANTIBODY AVIDITY FOR HEPATITIS-C VIRUS DISTINGUISHES PRIMARY ANTIBODY-RESPONSES FROM PASSIVELY ACQUIRED ANTIBODY

A new IgG antibody avidity test for hepatitis C virus (HCV) has been d eveloped and was validated using sera from 12 renal dialysis patients infected with HCV. In primary HCV infection low avidity antibody (mean avidity index 24%) was detected within 50 days of seroconversion wher eas in long-term infection (at least 300 days after seroconversion), t he mean avidity index was high (88%); in five patients, the avidity in dex was shown to increase rapidly as time elapsed after primary infect ion, whereas immunosuppressive therapy was found to delay maturation o f the immune reponse in two further patients. The assay was then emplo yed to confirm that a spurious outbreak of primary HCV infection in ei ght bone marrow transplant patients was explicable by passive acquisit ion of high avidity anti-HCV after intravenous immunoglobulin therapy. It is concluded that this avidity test will have an important role in the investigation of HCV infection in patients. (C) 1994 Wiley-Liss, Inc.