WHO collaborative studies on enterovirus reference antisera: second report.

This paper summarizes the results of the second part of co-operative studies undertaken by the WHO International Reference Centre for Enteroviruses and a number of WHO Regional Virus Reference Centres, WHO Virus Collaborating Laboratories and other laboratories in a comprehensive testing programme of enterovirus equine antisera. The studies were designed to appraise the specificity of immune serum prepared in horses against 16 representative prototype enteroviruses (polioviruses 2 and 3, coxsackieviruses A7, B1, B2, B4, B5 and B6 and echoviruses 1, 2, 3, 5, 7, 9, 12 and 17). Tests for neutralizing antibody were performed not only against the homologous viruses but also against the homotypic strains available in each laboratory. Tests for heterotypic antibody were made against the entire group of enteroviruses, reoviruses 1-3 and adenoviruses 1-11, 13 and 17. Each serum sample represented a pool of the individual bleedings taken from a group of horses before and after immunization with each virus antigen. The results showed that the homologous geometric mean titres of the immune sera ranged from 7000 to 36 000, whereas the preinoculation sera were negative. Results of the homotypic tests showed the usefulness of the sera. The specificity of the haemagglutination-inhibiting antibody of the sera against coxsackieviruses A7, B1, B5, B6 and echoviruses 3, 7, 12 was demonstrated. The results of the tests performed in tissue culture and mice are discussed. Co-operative testing of other enterovirus equine antisera is now in progress.