Attenuated Streptococcus equi ssp. zooepidemicus as a bacterial vector for expression of porcine circovirus type 2 capsid protein


Correspondence: Yaosheng Chen, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, North Third Road, Guangzhou Higher Education Mega Center, Guangzhou, Guangdong 510006, China. Tel.: +86 20 3933 2788; fax: +86 20 3933 2940; e-mail:


Porcine circovirus type 2 (PCV2) infection and other concurrent factors is associated with post-weaning multisystemic wasting syndrome, which is becoming a major problem for the swine industry worldwide. Coinfection of Streptococcus equi ssp. zooepidemicus (SEZ) and PCV2 in swine has necessitated demand for a recombinant vaccine against these two pathogens. A recombinant SEZ-Cap strain expressing the major immunogenic capsid protein of PCV2 in place of the szp gene of acapsular SEZ C55138 ΔhasB was constructed. Fluorescence-activated cell sorting and immunofluorescence microscopy analyses indicated that the capsid protein is expressed on the surface of the recombinant strain. Experiments in mice demonstrated that strain SEZ-Cap was less virulent than the parental strain and that it induced significant anti-PCV2 antibodies when administered intraperitoneally, which is worthy of further investigation in swine.