Development of the RTX-toxin as the vaccine against Avibacterium paragallinarum

• Main Authors: Mu-Han Kuo, 郭慕涵
• Other Authors: 張伯俊
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/84770629281646683096

碩士 === 國立中興大學 === 微生物暨公共衛生學研究所 === 104 === Avibacterium paragallinarum is a Gram-negative bacterium that causes infectioun coryza (IC), an important acute respiratory disease of chickens. Although the whole-cell inactivated vaccine is available, the disease still causes significant economic loss worldwide. RTX (Repeat in Toxin) is a pore-forming exotoxin produced by many Gram-negative bacteria. It may induce calcium flux in host cells and lead to cell lysis. The rtx gene from A. paragallinarum is composed of CABD genes. AvxA is the main structural protein toxin, which is activated by AvxC. AvxB and AvxD are type I secretion proteins that secrete AvxA into extracellular medium. Many studies showed that RTX toxin is an important virulence factor of pathogenic bacteria. The purpose of this study is to develope a vaccine based on AvxA. In this study, AvxA mutant is constructed by using Targetron gene knockout system to determine the role of RTX toxin in the pathogenesis of A. paragallinarum. Furthermore, AvxCA complement was constructed in A. paragallinarum to restore the function of the AvxA. Moreover, a recombinant protein containing the C-terminal half of AvxA was produced in Escherichia coli. Immunization of chickens with this recombinant protein confers chickens protection against challenge infection with A. paragallinarum. This is the first report showing that the recombinant RTX toxin could be a vaccine antigen against A. paragallinarum.