Hong-Jie F, Fu-yu T, Ying M, Cheng-ping L. Virulence and antigenicity of the szp-gene deleted Streptococcus equi ssp. zooepidemicus mutant in mice.
Vaccine 2008;
27:56-61. [PMID:
18983882 DOI:
10.1016/j.vaccine.2008.10.037]
[Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2008] [Revised: 10/03/2008] [Accepted: 10/12/2008] [Indexed: 11/16/2022]
Abstract
Streptococcus equi ssp. zooepidemicus (SEZ) causes serious disease in pigs. M-like protein (SzP) of SEZ is a virulence factor with opsonin function. To fabricate better vaccine against SEZ, We have generated a szp-knockout strain by homologous recombination. Two fragments, upstream and downstream of the szp gene, were obtained by genome walking. The vector was then used to delete a 1090 bp segment of szp gene from a strain of SEZ (ATCC35246). The mutant strain had 1000-fold decrease in LD50 as compared with wild type, and provided 85% protection against challenge with a virulent strain when administered as a live vaccine. Semi-quantitative RT-PCR analysis showed a marked increased in levels of IL-4 and IFN-gamma mRNA in immunized mice. These data demonstrate that szp-knockout strain is a better candidate for vaccine development.
Collapse