Extraction And Analysis Of Avibacterium Paragallinarum Capsular Polysaccharide And Study On Immunogenicity

Infectious coryza of chicken is caused by Avibacterium paragallinarum (Apg),which main symptoms are swelling of the cockscomb and eyelid. It is an acuterespiratory infectious disease, which could lead to the breeding chickens blocked ingrowth and improve rejection rate. It could also results in a loss of laying rate, hugelosses to poultry industry in our countryIn December2012, a widespread disease suspected as infectious coryza of layinghen outbreak in some commercial layer farms in the south of China. A series ofbacteriologic studies on the submitted samples were carried out. Four isolates of Apgwere identified by bacterial isolation, PCR test and the plate agglutination test. Clinicalsigns similar to field chickens were showed on SPF chickens after injected with theseisolates. Serological typing was carried out using the HA and HI test. It is a conclusionthat the pathogens are Apg of serovar B.In order to explore the feasibility of developing a new vaccine using thecomposition of capsular polysaccharide （CPS） from Avibacterium paragallinarum(Apg), Apg CPS was extracted in culture supernatantand with the ethanol precipitation.Its contents were detected using phenol-sulfuric methods, and polysaccharideconstituents and molecular weight were analysized whih high performance liquidchromatography （HPLC）The results showed that85mg capsular polysaccharide isextracted from every liter bacterium solution, the rate of content is62%, which arecomposed of L-rhamnose、D-xylose、D-glucose and an unknown monosaccharide. Itsmolecular weight is about209Ku.Furthermore, the protective immunity was tested by vaccination with capsularpolysaccharide and hemagglutinin （HA） component separate or mixed. The SPFchickens were immunized with HA, CPS and CPS plus HA respectively, following bytoxicity attack test. Blood samples were collected after the first immunization and thesecond one. Using the method of ELISA, the antibody tite of serum was detected andthe immune protective rates of all experimental groups were calculated. The resultsshowed that the antibody level of CPS plus HA immunization group is higher than HAor CPS group separately. As far as the immune pathway is concered, intranasal immunization can significantly improve the level of serum antibody and protection,compared to intramuscular injection. It indicatess that the CPS of serovar B Apg hascertain immunogenicity, and its immune protection rate has improved significantlywhen it is combined with HA.