The surface antigens of orthopoxviruses detected by cross-neutralization tests on cross-absorbed antisera

Abstract

Cross-neutralization tests were done on accepted species and recently isolated members of the genus Orthopoxvirus using antisera which had been separately absorbed with the various viruses. The results provided evidence for the involvement of four neutralizing antigens, and their distribution among 13 virus strains was determined. Monkeypox (Congo-8-Lombe), camelpox (Gorgan), ectromelia (Mill Hill), 'Lenny' and elephant poxviruses had distinctive antigenic formulae. Lister and Wyeth vaccines were indistinguishable but different from Copenhagen and EM63 vaccines which were themselves distinct. Cowpox (Brighton), buffalopox (BP4), MK 10, and Moscow poxviruses were indistinguishable. Examples were found where viruses shared surface antigens but were not all neutralized by antibody to them. this reduced the practical value of the technique for virus identification. Evidence was also obtained for the existence in some viruses of a fifth antigen, antibody to which could block neutralization by antibody to one particular antigen.