A novel DNA vaccine against Streptococcus bovis: study on multi-epitope DNA antigen based on RodA gene and its specific IgY antibody

Streptococcus bovis is one of the leading causes of infective endocarditis and is associated with colon cancer. It can also cause rumen acidosis in ruminants and cause pigeon sepsis. The prevalence of pathogens among susceptible animals not only poses a serious threat to human health but also causes losses to animal husbandry. Its harm cannot be ignored. Vaccination can effectively control and prevent infection. In this study, the T cell and B cell dominant epitope gene sequences screened from the Rod A gene of Streptococcus bovis were tandem with the mucosal immune adjuvant cholera toxin B subunit ( CTB ) gene. The codon was optimized as CTB-RodA-RodA ( CRR ) gene sequence. After artificial synthesis, the CRR gene was inserted into the eukaryotic expression vector pVAX1. The multi-epitope DNA vaccine pVAX1-CRR was successfully constructed. The pVAX1-CRR and immune adjuvant CTB were combined to immunize laying hens. The specific IgY in eggs was extracted by salting out method and named CRR-IgY. Preliminary exploration of pVAX1-CRR immunogenicity showed that the titer of CRR-IgY was as high as 1: 6400. The in vitro antibacterial effect of the CRR-IgY on Streptococcus bovis was detected. It was found that 10 mg/ml CRR-IgY could significantly inhibit the growth of Streptococcus bovis isolates. In summary, this study successfully screened, constructed and expressed the multi-epitope vaccine pVAX1-CRR of Streptococcus bovis. It produces a high level of antibodies and a good antibacterial effect.