Genetic Enginerring Vaccines Against Toxigenic Pasteurella Multocida And Paratyphoid Of Swine

Progressive atrophic rhinitis (PAR) mainly caused by D-type toxigenic Pasteurella multocida (T+Pm) was a severe respiratory passage disease of pigs, and brougtt with heavy loss of husbandry industry.The principal way to control this disease is vaccine immunity. With the development of molecular biology, genetic engineering vaccine is widely used to prevent infectious diaeases. In view of this, this research used the low virulent genetical-engineered C501 Salmonella bacillus vaccine strain which was constructed by Dr. Xu Yindin as a vector, transformed the immunogenic fragment C end of toxA gene into the vector, and obtained a new genetical-engineered vaccine strain against PAR and pig paratyphoid. The main contents are as follows:1. Construction and biologicalproperty of recombination strain C501 (pYA-toxAc)The primers of immunogenic fragment of HN-13 were designed according to the C end, fragment of toxA gene (GenBank:AY864768), constructed the recombination plasmid pYA-toxAc which was non-resistant, then electro-transform pYA-toxAc plasmid into gene-deletion mutant strain C501, and got a new recombination strain. The recombination strain of Salmonella bacillus was inherited stably, no mutant and sustained secrete expression. The phenotype and the bio-characteristics research indicated that there was no difference between C501 (pYA-toxAc) and its parental strain, but the virulence of the recombination strain is about twice times lower than the parental strain.2. The immunity protection of recombinantion vaccine in miceThe mice were vaccinated with recombined vaccine through hypodermic injection or take orally, with a twice vaccinated 14 days later. Two weeks after the second immunization, the mice were challenged intraperitoneally with 5 x LD50 of toxigenic Pasteurella multocida and taken orally 10×LD50 of Salmonella bacillus. Mice were blooded at day 0,14 and 28, samples were detected antibody of serum IgG and intestines IgA against Salmonella bacillus and toxAc gene. The result showed that hypodermic injection could provide high level of IgG and low level of IgA, however, orally approach get an opposite result. Both hypodermic injection and orally approach have a protective efficiency of 100% against challenge of Salmonella bacillus, hypodermic injection has a protective efficiency of 80% against challenge of the strain HN-13, orally approach was 60%, the mortality of contraposition was 80%.3. The immunity of recombinantion strain in swine10 Piglets were randomly divided into two experimental groups. The immunity group was vaccinated twice through intramuscular injection in the neck with 3×109CFU recombinant strains, the control group was inoculated with 20% of aluminum hydroxide gel. Pigs were blooded at day 0,14 and 28 after first inoculation, detected antibody against Salmonella bacillus and rtoxAc. The result showed that there being the antibody of IgG against Salmonella bacillus and exogenous target fragment and their titer OD are 2.135 and 1.351.