Construction and immunogenicity of a ∆apxIC/ompP2 mutant of <i>Actinobacillus pleuropneumoniae</i> and <i>Haemophilus parasuis</i>
2013
Qiong Liu | Yuheng Gong | Yuqin Cao | Xintian Wen | Xiaobo Huang | Qigui Yan | Yong Huang | Sanjie Cao
The apxIC genes of the <em>Actinobacillus pleuropneumoniae</em> serovar 5 (SC-1), encoding the ApxIactivating proteins, was deleted by a method involving sucrose counter-selection. In this study, a mutant strain of <em>A. pleuropneumoniae</em> (SC-1) was constructed and named DapxIC/ ompP2. The mutant strain contained foreign DNA in the deletion site of ompP2 gene of <em>Haemophilus parasuis</em>. It showed no haemolytic activity and lower virulence of cytotoxicity in mice compared with the parent strain, and its safety and immunogenicity were also evaluated in mice. The LD<sub>50</sub> data shown that the mutant strain was attenuated 30-fold, compared with the parent strain (LD<sub>50</sub> of the mutant strain and parent strain in mice were determined to be 1.0 × 10<sup>7</sup> CFU and 3.5 × 10<sup>5</sup> CFU respectively). The mutant strain that was attenuated could secrete inactivated ApxIA RTX toxins with complete antigenicity and could be used as a candidate live vaccine strain against infections of <em>A. pleuropneumoniae</em> and <em>H. parasuis.</em>
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