The Protective Efficacy Induced By Chimeric PCV1-2 Inactivated Vaccine And The Pilot-scale Test Of Chimeric PCV1-2 Live Vaccine

Porcine circovirus type 2 (PCV2) is the primary causative agent and recently recognized as the pathogen of postweaning multisystemic wasting syndrome (PMWS) and other associated diseases. PCV2 is also associated with some other swine diseases such as porcine dermatitis and nephropathy syndrome (PDNS), porcine respiratory disease complex (PRDC) and reproductive failure, now collectively referred as porcine circovirus diseases (PCVD). The most common clinical signs are unthrifty wasting, dyspnoea, enlarged lymphnodes, diarrhea, pallor and jaundice.The purpose of this study was to evaluate the protective efficacy of the inactivated chimeric PCVl-2 by subjecting conventional pigs with low maternal antibody to intramuscular immunization with this inactivated chimeric PCV1-2 followed by the challenge with wild-type PCV2 strain. On the other hand, the pilot-scale test of PCV1-2 inactivated vaccine and PCV1-2 live vaccine was performed to evaluate the protective efficacy of them in pig farms. 1. Chimeric inactivated PCV1-2 evaluated in conventional pigs for its protective efficacy against PCV2 infectionA chimeric PCV1-2 clone containing the PCV2 capsid gene cloned into the backbone of the nonpathogenic PCV1 genome was recently generated based on the PCV2 and PCV1 strains isolated in China. Furthermore, the protective efficacy of this available candidate inactivated vaccine was evaluated by subjecting conventional pigs to intramuscular immunization with this inactivated chimeric PCV1-2 followed by the challenge with wild-type PCV2 strain. By 35 days post-vaccination (DPV), all vaccinated pigs had seroconversion to antibody against PCV2 and developed high titer of the indirect immunofluorescent assay (IFA) antibody and neutralizing antibody. By 21 days post-challenge, gross and microscopic lesions of lymph nodes and lungs in non-vaccinated but challenged pigs were significantly more severe than those found in vaccinated groups. PCV2 viral copy loads detected in tracheobronchial lymph nodes or serum samples of vaccinated pigs were very lower than those in non-vaccinated but challenged pigs (P<0.05). The results illuminated that the inactivated chimeric PCV1-2 could induce protective immunity against PCV2 infection effectively.2. The pilot-scale test of Chimeric PCV1-2 inactivated vaccineAccording to Safety Evaluation and Management Measures of Agricultural Transgenosis issued by Ministry of Agriculture, the pilot-scale test of chimeric PCV1-2 inactivated vaccine was performed in Jiangsu province. Ten conventional pigs at 10-day-old were vaccinated with PCV1-2 inactivated vaccine. IFA was taken to detect the seroconvention to antibody against PCV2 at regular intervals. At the same time, the possibility of the PCV1-2 virus excretion and the pathogenicity to non-target animals next to the pig farm were evaluated. The results illuminated that chimeric inactivated PCV1-2 vaccine could induce obvious humoral immunity response and there was no significant change in growth weights between pigs vaccinated with inactivated PCV1-2 and those without vaccination. On the other hand, there were no pathogenicity and adverse reactions to non-target animals next to the pig farm.3. The pilot-scale test of Chimeric PCV1-2 live vaccineAccording to Safety Evaluation and Management Measures of Agricultural Transgenosis issued by Ministry of Agriculture, the pilot-scale test of PCV1-2 live vaccine was performed in Jiangsu province. Ten conventional pigs at 10-day-old were vaccinated with PCV1-2 live vaccine. IFA was taken to detect the seroconvention to antibody against PCV2 at regular intervals. At the same time, the possibility of the virus excretion and the pathogenicity to non-target animals next to the pig farm were evaluated. The results illuminated that chimeric PCV1-2 live vaccine could induce obvious humoral immunity response and there was no significant change in growth weights between pigs vaccinated with PCV1-2 live vaccine and those without vaccination. On the other hand, there were no pathogenicity and adverse reactions to non-target animals next to the pig farm.