Evaluation And Comparison Of Immune Efficacy Of Eight PCV2 VLPs Vaccines

Porcine circovirus disease is a chronic infectious disease of pigs,especially in weaned piglets,caused by porcine circovirus type 2.Owing to its high infection rate and low mortality rate,host immune suppression,PCVD caused huge economic losses to the pig industry.Vaccine immunization is the most important and effective method to control PCV2 infection and prevent PCVD.At present,there are various commercial vaccines on the market,and their safety and effectiveness vary widely.The urgent problem that pig farms(and households)are currently facing are: how to choose a safe and efficient vaccine against porcine circovirus correctly and scientifically? How to carry out effective prevention and control of porcine circovirus? Therefore,establishing a scientific and reasonable evaluation system to evaluate the safety and efficacy of commercial PCV2 vaccine and to compare vaccines safety and efficacy effects of different adjuvants are of great significance for the selection of high efficient vaccines and the development of new vaccines.In this study,eight commercial PCV2 VLPs vaccines covering the baculovirus expression vector VLP vaccines and the E.coli expression VLP vaccines,which also combined with different adjuvants,such as water-based adjuvant,propolis-VSP compound adjuvant,propolis-VCG compound adjuvant and immunopotentiator respectively,were selected to evaluate the safety and efficacy on Kunming mice and piglets were evaluated in parallel.Safety index including relative weight gain,body temperature,diet,mental state,vaccination site,and histopathological differences as well were used to score the safety of vaccines.The mRNA transcription levels of IL-10,IL-17 A,IFN-γ in tissues and peripheral blood lymphocytes was detected by real-time fluorescent PCR.IL-2 and IL-4 protein levels in peripheral blood were detected by ELISA.PCV2 antibody titer and,the immune protection rate and tissue nucleic acid loads were used to evaluate the immune efficacy of the vaccine.In this paper,six SYBR Green I RT-PCR methods for detecting IFN-γ,IL-17 A and IL-10 in mice and piglets were established,which can be used to quantify the expression levels of IFN-γ,IL-17 A and IL-10 in clinical practice.Compared the result of safety test,it indicated that the scores of safety index in mice and piglets in PCV2 vaccinated group C,E and F were significantly higher than others,of which group E was the highest.Mice in group H showed fewer pathological changes and less stimulation to the immune muscles,followed by group Aand group F.The results of potency test comparison showed that vaccines in group G and group H had higher efficacy in mice and piglets than those in other groups,which induced more humoral immunity.Group G showed an increase of IFN-γ and IL-17 A mRNA expression in piglets,indicating that higher specific immunity was induced.In this paper,a “five in one” gold standard including the safety index,antibody titer,cellular immune factor,immunosuppressive factor,and viral load were successfully established for vaccine evaluation.With this standard,the safety and efficacy of 8 PCV2 vaccines with different adjuvants were analyzed and compared,showing that vaccine G and vaccine H from company D have the best immune effecacy and good safety which significantly enhanced the specific immunity and nonspecific immunity of pigs,and reduced the local stimulation response of the immune site.The study provide data supports for the safety and efficacy test of PCV2 vaccine and clinical popularization application.