WHO collaborative studies on enterovirus reference antisera.

This paper summarizes the results of co-operative studies undertaken by the WHO International Reference Centre for Enteroviruses and a number of WHO Regional Reference Centres for viruses, WHO Virus Collaborating Laboratories, or 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 five representative prototype enteroviruses (poliovirus 1, coxsackieviruses A9 and B3, and echoviruses 4 and 11). Tests for neutralizing antibody were performed not only against the homologous viruses, but also against a battery of heterotypic picornaviruses, comprising 63 enteroviruses, several rhinoviruses, and three reoviruses. Each serum sample represented a pool of the individual bleedings taken from groups of five or six horses before and after immunization with each virus antigen (except echovirus 4, for which three animals were immunized). The results showed that, whereas the homologous titres of the antisera (poliovirus 1, coxsackieviruses A9 and B3, echoviruses 4 and 11) were found to be within a useful range (700-8000), heterotypic antibodies of significant titre were not detected. All corresponding pre-inoculation sera were negative. The specificity of the haemagglutination-inhibiting antibody of the coxsackievirus B3 and echovirus 11 antisera was also demonstrated. This accumulated information played a major role in a decision to prepare in horses antisera to the rest of the enterovirus group. Co-operative testing of the other enterovirus equine antisera is now in progress.