Production of polyclonal antibody against surface antigen One (SAO) protein of Streptococus suis for optimization of an indirect ELISA

Abstract

Surface antigen one (SAO) is a protein from the major important zoonotic pathogen, Streptococcus suis. In this study, recombinant SAO-M protein was produced in E. coli BL21(DE3)pLys cells and was purified by using His-tag; and the purified SAO-M then is used as the antigen for the immunization on rabbits for specific antibody production. We successfully developed the indirect EILSA tests, consisting of SAO-M antigen and anti-rabbit – HPR conjugate to detect the anti-SAO-M antibody containing rabbit sera. The results showed that SAO-M shows protein potentially its possessing a high antigenicity nature since it could enhanced the specific immune responses against SAO-M through evidently via the increasing of titer of antibody against SAO-M during the immunization process. Our other preliminary results suggested that rabbit sera contain antibody. The primary indirect EILSA test was developed consisting of SAO-M antigen coating concentration 0.2 _ g/well, and 1/10000 anti-rabbit – HPR conjugate to detect the anti-SAO-M antibody in rabbit sera. The specificity of recombinant SAO-M antigen to the protein of other common pathogens was tested by cross-reaction test; however it is necessary to perform some further tests before using this ELISA assay in sero-surveillance to better evaluate this current finding. Key words: Streptococcus suis, recombinant SAO-M protein, immunization, ELISA.