57 (Pt. 3) 303-312 (1979) PURIFICATION OF ANTIBODIES TO INFLUENZA A VIRUS STRUCTURAL PROTEINS BY AFFINITY CIIROMATOCRAPHY, AND THEIR PARTICIPATION IN HAEMACGLUTINATION- INHIBITION, NEUTRALIZATION AND ENZYME-LINKED IMMUNOSORBENT ASSAY by H. WATANABE, MARGARET POLLETT .AND J. S. MACKENZIE' (From the Department of Microbiology, Queen Elizabeth II Medieal Centre, Nedlands, Western Australia 6009.) (Accepted for publication May 7, 1979.) Summary. Affinity chronialography was used to purify rabbit antibodies to ciinmion and strain-specific antiyt-nelc detenninants of haeniaggliitiniii, to ncnraniinidase, and to a combination of the internal proteins of inilucnza A vinLses. The pnrity of the antibodies was assessed by hacinanRlutination- tnhibition, enzyme-linked imninnosorbent as.say (ELISA) and competition ELISA. The antibodies were examined for their participation in neutralization and baeniagglntination-inhibition assays, and in ELISA. ELISA was found to be the most seasitivp tt-chniciue fnr detecting antibodies. Antibodies to the common and strain-specific detenninants of haentagglatinin were shown to participate in nentralizatiun assays and ELISA, but only tho.sc antibodies to the coiinnoii determinants were detected by haemagglutination-inhibition, INTRODUCTION Influenza A virus particles contain .seven structural proteins; two external glycoproteins. haemagglutinin and neuraniinida.se, and five internal proteuis (reviewed by Wrigley, 1979). The haemagglutinin i.s responsible for virus attachment to susceptible cells and for the ability of the vims to agglutinate erytlirocytes. Humoral and local immnne reactions concerned with nentralization and proteetion arc mediated principally throngli antibodie.s to the haemagglu- tinin. The haemagglntinin contain.s mnltiplc antigenic determinants, .some of which are common to all vini.ses of the same antigenie drift series (HA-CM), whereas fithcrs arc specific to each individual strain (MA-ST) (Laver, Downie and Webster, 1974). All tlie determinants are located on the side of the " Reprint requests should be sent to Dr. Mackenzie.