Development of blocking ELISA for detection of antibodies against avian influenza virus of the H7 subtype.

BACKGROUND AND PURPOSE: The conventional method used for subtyping of antibodies against avian influenza viruses is hemagglutination inhibition (HI) test. However, the HI test is laborious and requires preparation of antigen from viable viruses that might be hazardous. The aim of this study was to develop a blocking enzyme-linked immunosorbent assay (B-ELISA) for detection of antibody of avian influenza of the H7 subtype. The B-ELISA is fast and avoids the need to culture whole viruses. METHODS: The B-ELISA was based on the reaction between a monoclonal antibody and a recombinant hemagglutinin protein purified from Escherichia coli. The specificity of the B-ELISA was determined by testing H7-negative field sera and the sensitivity of the B-ELISA was determined by testing sera collected from experimentally immunized chickens. RESULTS: The specificity of the B-ELISA was found to be 97.7% when compared with the HI test. The sensitivity was found to vary with the HI titer of sera. A sensitivity of 100% was achieved when test sera had HI titers >or=2(7). The sensitivity dropped to 33% and 20% when test sera had HI titers of 2(6) and 2(5), respectively. Nearly all test sera with HI titers

Genetic and pathogenic characterization of H6N1 avian influenza viruses isolated in Taiwan between 1972 and 2005.

This article reports the genetic and pathogenic characteristics of 34 isolates of H6N1 avian influenza viruses isolated in Taiwan between 1972 and 2005. Genetic analyses showed that a unique lineage of H6N1 viruses has been established in domestic chickens in Taiwan since 1997, and this lineage of viruses differs from the H6N1 viruses circulating in Hong Kong and Southeastern China. Pathogenicity tests showed that all Taiwanese H6N1 viruses were of low pathogenicity but might lead to economic loss when associated with other diseases. Hemagglutination inhibition tests showed that antigenic drift has occurred in Taiwanese H6N1 viruses, and sequence comparison has identified a total of five possible antigenic sites on the hemagglutinin molecule of the H6N1 viruses. Some Taiwanese H6N 1 viruses could replicate in mice without preadaptation, indicating that these viruses have the potential to cause cross-species infection into mammals.