Background: It has been recognised that the haemagglutination–inhibition (HI) test is not sufficiently sensitive to detect human antibody to H5N1 influenza virus and alternative serological tests are needed. A modified single radial haemolysis (SRH) test is described. Methods: Sera from H5N1 human cases in Hong Kong SAR and from H5 vaccine trials were tested by an H5 SRH test which included a virus adsorption step to remove cross-reactive antibody. Test specificity was examined using reference animal antisera. Results: The SRH test recognised antibody in a specific antiserum to A/Hong Kong/489/97 (H5N1) virus, yet rabbit antibody to an A (H10N7) avian virus and human antibody to A (H1N1) or A (H3N2) viruses did not react. H5 SRH antibody induced by human H5N1 virus infection and A/Duck/Singapore/97 (H5N3) vaccination, correlated with antibody detected by microneutralisation techniques. Conclusion: The modified SRH test offers an alternative serological technique for detecting antibody to H5 haemagglutinins, which does not depend on use of live pathogenic H5N1 virus.
- H5 antibody