SUBTYPE-SPECIFIC ELISA FOR THE DETECTION OF ANTIBODIES AGAINST INFLUENZA A H1N1 AND H3N2 IN SWINE

A subtype specific ELISA using purified hemagglutinin (HA) from influe nza A H1N1 and H3N2 was developed to detect antibodies present in swin e previously exposed to either H1N1 or H3N2 influenza viruses. The HA was extracted using the detergent octylglucoside followed by ion excha nge chromatography. All HA preparations were free of contaminating nuc leoprotein and matrix protein contamination. Monospecific swine anti-H 1N1 and swine anti-H3N2 sera were used to demonstrate the subtype spec ificity of the assay. Monospecific rabbit anti-H1N1 or H3N2 was used t o sterically block crossreacting determinants and thus enhance assay s pecificity. A linear relationship between single dilution point ELISA and the hemagglutination inhibition (HI) test was established. This en abled the accurate estimation of HI titer from ELISA. Further refineme nt of this ELISA based HI estimation system could allow it to replace the current HI procedures in instances where identification at the sub type level of specificity is acceptable. The substantial specificity r equirements associated with the detection of strain specific antibody would still necessitate the use of the HI procedure.