Rapid detection of H5N1 subtype influenza viruses by antigen capture enzyme-linked immunosorbent assay using H5- and N1-specific monoclonal antibodies.

Highly pathogenic avian influenza (HPAI) virus of the H5N1 subtype has caused devastating damage to poultry flocks and sporadic human H5N1 infections. There is concern that this virus subtype may gain transmissibility and become pandemic. Rapid diagnosis and surveillance for H5N1 subtype viruses are critical for the control of H5N1 infection. In this study, we report a robust antigen-capture enzyme-linked immunosorbent assay (AC-ELISA) based on H5- and N1-specific monoclonal antibodies (MAbs) for the rapid detection of H5N1 subtype viruses. The H5 hemagglutinin (HA)-specific MAb (2D9) targets a conformational epitope which recognized multiple clades of H5N1 viruses, including clades 0, 1, 2.1, 2.2, 2.3, 4, 7, and 8. The N1 neuraminidase (NA)-specific MAb (8H12) recognized a linear epitope comprising the sequence AELPF. This epitope was 99% conserved in the NA of 708 analyzed H5N1 viruses, while the epitope was absent in NAs of subtypes N2 through N9. The specificity of the AC-ELISA was examined by using 41 H5N1 HPAI strains from multiple clades, 36 non-H5N1 viruses, and 4 influenza B viruses. No cross-reactivity was observed for any of the non-H5N1 viruses tested. The estimated detection limit was 1 to 2 HA titers. It is concluded that this H5N1 AC-ELISA can simultaneously detect H5 and N1 subtype antigens, eliminating the need for secondary testing for the NA subtype. Implementation of this assay in ELISA-like formats suitable for field use, such as dot ELISA, immunofiltration, or electrochemical biosensor technologies, would provide dual on-site detection of H5 and N1 in clinical or environmental specimens.