Immunization Procedure And Stability Of Mixed DNA Vaccine Against Chicken Coccidiosis

Avian coccodiosis is an econmomically important disease for the poultry industry throughout the world. E. tenella, E. necatrix, E. maxima, E. acervulina are jeopardize severely and mixed infection in the clinic. So it is urgent that research mixed multivalency DNA vaccine and multivalency epitope DNA vaccine to resist the Eimeria spp. The mixed DNA vaccine was already constructed in the laboratory and induced the effective protection against four species of Eimera spp. To compare the protective effect of DNA vaccine, chemical (diclazuril), live attenuated vaccine (COCVAC) against E. tenella, E. necatrix, E. maxima, E. acervulina and mixed eimeria; improve the more effective immunity protection further. The protective effect of DNA vaccine, chemical (diclazuril), live attenuated vaccine (COCVAC) against E. tenella, E. necatrix, E. maxima, E. acervulina and mixed eimeria was compared; the immunization procedure and stability of mixed DNA vaccine were optimized..The protective effect of DNA vaccine, chemical (diclazuril), live attenuated vaccine (COCVAC) against E. tenella, E. necatrix, E. maxima, E. acervulina and mixed eimeria was compared. The chickens of attenuated vaccine group were immunized at the age of6days follow the introduction. At the age of14days, chickens of DNA vaccine groups were intramuscularly immunized with the corresponding DNA vaccine. A booster immunization was given by the same method as the first immunization7days later. The chemical group was added diclazuril in the drink water follow the introduction. At the age of28days, the chickens were challenged with sporulated oocysts of the corresponding Eimeria spp. except the unimmunized-unchallenged control groups. Seven days post challenge, all the chickens were slaughtered. Body-weight gain, oocysts per gram feces (OPG), lesion score, and ACI of each group were calculated. The results illustrated that ACIs of DNA vaccines challenged with E. tenella, E. necatrix, E. maxima and mixed eimeria were higher than groups diclazuril and groups COCVAC. In the groups challenged with E. acervulina, the ACI of DNA vaccines were lower than COCVAC, but higher than diclazuril. In all, DNA vaccines achieved good effective protection against chicken coccidiosis. The immunization procedure and stability of the mixed DNA vaccine were analysised in the second part of the research.1Optimization of immunization doses of mixed DNA vaccine against chicken coccidiosisThe immunization dose of mixed DNA vaccine against E. tenella, E. necatrix, E. maxima and E. acervulina was optimized. Chickens were immunized with DNA vaccine of2μg,10μg,25μg,50μg,100μg and200μg, respectively. Then the animals immunized with each dose DNA vaccine were challenged with E. tenella, E. necatrix, E.maxima and E. acervulina respectively. Unimmunized-challenged and unimmunized-unchallenged control groups were also designed. There were29groups in all. The result illustrated that ACIs of groups10μg challenged with E. tenella were191.63, and ACIs of groups25μg challenged with E. necatrix, E. maxima and E. acervulina were177.31,168.84and165.49respectively. They achieved better effective protection against chicken coccidiosis than others.2Optimization of immunization routes of mixed DNA vaccine against chicken coccidiosisThe immunization routes of mixed DNA vaccine were optimized. Chickens were immunized with DNA vaccine by the routes of intramuscular injection, intravenous injection, subcutaneous injection, oral administration and intranasal administration. Then the immunized animals were challenged with E. tenella, E. necatrix, E. maxima and E.acervulina respectively. Unimmunized-challenged and unimmunized-unchallenged control groups were also designed. There were25groups in all. The results illustrated that ACIs of intramuscular injection challenged with E. tenella, E. necatrix, E. maxima and E. acervulina were162.89,179.54,174.94and167.10respectively, which were higher than the ACIs of other routes. The results also showed that intramuscular injection could provide effective protection against chicken coccidiosis, which was the best immunization route of the five immunization routes.3Optimization of primary immunization age and immunization times of mixed DNA vaccine against chicken coccidiosisThe primary immunization age and immunization times of mixed DNA vaccine was optimized. Chickens were immunized with DNA vaccine with different primary immunization age and immunization times including single immunization at7days and twice immunization at7and14days old respectively; single immunization at14days and twice immunization at14and21days old respectively. Then the animals immunized with different procedures were challenged with E. tenella, E. necatrix, E. maxima and E. acervulina, respectively. Unimmunized-challenged and unimmunized-unchallenged control groups were also designed. There were21groups in all. The result illustrated that the booster immunization groups were better than the non-booster immunization groups. The results also showed that older primary immunization age groups showed higher ACI than younger primary immunization age groups and twice immunization groups of at14and21days old were the best.4The stability of mixed DNA vaccine against chicken coccidiosisThe stability of mixed DNA vaccine was analysised. DNA vaccines were stored at-20℃,4℃and room temperature for1month,3months and6months respectively and were used to immunize chickens. Then the immunized chickens were challenged with E. tenella, E. necatrix, E. maxima and E. acervulina respectively. Unimmunized-challenged and unimmunized-unchallenged control groups were also designed. The result illustrated that most ACIs of immunized groups were beyond160, which showed effective protect against chicken coccidiosis. The results also indicated that preservation time and temperature had little effect on the immunizing efficacy of the DNA vaccine in6months.