title: Virulence and antigenicity of the szp-gene deleted Streptococcus equi ssp. zooepidemicus mutant in mice.
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.
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China. fhj@njau.edu.cn
authors.forename: Fan
authors.initials: F
authors.lastname: Hong-Jie
authors.forename: Tang
authors.initials: T
authors.lastname: Fu-yu
authors.forename: Mao
authors.initials: M
authors.lastname: Ying
authors.forename: Lu
authors.initials: L
authors.lastname: Cheng-ping
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D001428:Bacterial Vaccines / Q000276:immunology*; D007111:Immunity, Cellular / Q000276:immunology; D007114:Immunization; D007371:Interferon-gamma / Q000276:immunology; D015847:Interleukin-4 / Q000276:immunology; D007928:Lethal Dose 50; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D011897:Random Allocation; D013154:Spleen / Q000276:immunology; D013290:Streptococcal Infections / Q000276:immunology / Q000517:prevention & control*; D018502:Streptococcus equi / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*; D037521:Virulence Factors / Q000235:genetics / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; C107892:SzPSe protein, Streptococcus equi; D037521:Virulence Factors; D015847:Interleukin-4; D007371:Interferon-gamma