Short communicationImproved specificity and reduced subtype cross-reactivity for antibody detection by ELISA using globular head domain recombinant hemagglutinin

- Age-related rise in subtype cross-reactive antibody in unexposed normal human population is observed.
- ELISA using GH HA shows significantly higher specificity and lower subtype cross-reactivity.
- The specificity using both unexposed and exposed persons is necessary.

The relative performance of ELISA using globular head domain (GH) and ectodomain hemagglutinins (HAs) as antigens to detect influenza A virus IgG antibody responses was assessed. Assay sensitivity and subtype cross-reactivity were evaluated using sera collected from recipients of monovalent H5N1 vaccine and A(H1N1)pdm09 virus-infected persons. Assay specificity was determined using collections of sera from either individuals unexposed to either H5N1 or A(H1N1)pdm09 viruses or exposed to H5N1 or A(H1N1)pdm09 viruses through vaccination or infection, respectively. ELISA using GH HA showed a similar degree of sensitivity, significantly higher specificity, and significantly lower subtype cross-reactivity compared to ELISA using ectodomain HA.