Abstract: ObjectiveTo test the immunoprophylaxis of ZnuA in Streptococcus suis 2(S.suis)and to provide experimental evidence for the study of sub-unit vaccine.MethodsBased on the sequence of ZnuA of the Chinese strain 05ZYH33 of S.suis 2,the primers were designed and the target DNA fragment was amplified using the genomic templates of different serotypes of S.suis.Western blot was performed to detect the expression of ZnuA of S.suis 2.An assay based on flow cytometry(FCM)was developed to detect the localization of ZnuA on the surface of S.suis 2.Anaimal test was done to study the immunoprotection of ZnuA.ResultsThe target DNA fragment was amplified in most serotypes of S.suis (except strains SS17,21,30 and isolated strain T15).Fluoreseence-activated cell sorting(FACS)analysis and western blot showed that ZnuA localized on the surface of S.suis.Immunization with purified ZnuA could protect BALB/c mice against the challenge with a highly virulent S.suis 2 strain 05ZYH33.ConclusionZnuA could protect BALB/c mice against the challenge of a highly virulent S.suis 2 strain 05ZYH33,which suggests that ZnuA may be a candidate for the development of antibacterial protein sub-unit vaccine.