Isolation of anti-haemagglutinin antibodies with an influenza A virus immunoadsorbent

The X-31 strain of influenza A (H3N2) virus has been covalently bound to CNBr activated agarose for the separation of anti-haemagglutinin antibodies. The virus immunoadsorbent was used repeatedly under high ionic strength alkali buffer and acid conditions without altering appreciably its antibody binding capacity. Sequential elution of bound anti-haemagglutinin antibodies with increasing concentrations of sodium iodide has enabled the physical separation of antibody populations with low and high avidity for the virus immunoadsorbent. In haemagglutination inhibition (h1) assays, the less avid population reacted only with the homologous X-31 virus, wheras the more avid antibody population reacted both with the homologous and the related cross-reactive A/England/42/72 (H3N2) strains. Sequential elution under acid conditions did not completely remove the bound anti-haemagglutinin antibodies and those eluted retained little of their anti-haemagglutinin activity. From a practical point of view, given a specific antiserum, it is feasible to use whole virus as an immunoadsorbent for the purpose of isolating populations of antibodies of different avidities and cross-reactivities. Furthermore, sodium iodide as an eluting agent has proved most effective in recovery of active and stable antibodies from the agarosebound virus.