NEW HEPATITIS-B VIRUS MUTANT FORM IN A BLOOD-DONOR THAT IS UNDETECTABLE IN SEVERAL HEPATITIS-B SURFACE-ANTIGEN SCREENING ASSAYS

BACKGROUND: Envelope mutant forms of hepatitis B virus (HBV), impairin g HBV antibody recognition, have been reported with mutations in singl e or multiple sites of the hepatitis B surface antigen (HBsAg) group-s pecific ''a'' determinant. Blood donors infected with such an HBsAg mu tant form of HBV may escape detection by HBsAg screening assays and th erefore may affect the safety of the blood supply. CASE REPORT: A repe at blood donor became HBsAg-reactive in an enzyme immunoassay. Confirm atory testing yielded negative results for HBsAg in a radioimmunoassay and in four enzyme immunoassays used in blood donor screening. The sp ecificity of the HBsAg reactivity in the first enzyme immunoassay was confirmed by HBsAg neutralization with antibody to HBsAg. Additional H BV confirmatory test results were positive for antibody to hepatitis B core antigen and antibody to hepatitis B e antigen; negative for anti body to HBsAg and for hepatitis B e antigen; and positive for HBV DNA. DNA sequence analysis of the ''a'' determinant region of HBsAg reveal ed amino acid substitutions from Q (Gin) to R (Arg) at codon 129 and f rom M (Met) to T (Thr) at codon 133. CONCLUSION: This case illustrates the presence of HBsAg mutant forms of HBV in a West European blood do nor population that were undetected by several HBsAg screening assays. Adaptation of HBsAg screening is indicated to overcome deficiencies i n sensitivity in detecting HBsAg mutant forms of HBV. Screening for an tibody to hepatitis B core antigen or HBV DNA may also detect blood do nors infected with HBsAg mutant forms of HBV.