Development Of Avian Escherichia Coli Ghosts And Its Immune Efficacy

Avian Escherichia coli disease is a local or systemic infection disease and causes by avian pathogenic Escherichia coli. This disease is not effectively controlled because of the complex antigen and various serotypes. Currently, the inactivated vaccines can not totally control the epidemic of the disease, thus,novel efficient vaccines are urgently needed.In this study, PhiX174 phage lysis gene E and S. aureus nuclease A gene(SN) were inserted into the MCS of expression vector pFBDM. To avoid the presence of antibiotic resistance genes in the bacterial-ghost vaccine preparation, the DNA is degraded by a nuclease in combination with the protein E-mediated lysis system. The nuclease of Staphylococcus aureus cleaves either single- or double-stranded DNA or RNA into nucleotides less than 100 bases. This study successfully constructed recombinant plasmid pFBDM-E-SN. Escherichia coli with the recombinant plasmids were grown in a shaker at 28℃ under aerobic conditions until middle log-phase. Then the culture was transferred to a 42℃ water-bath shaker in order to make it cleavage. Using plate count method for calculating the rate of bacterial lysis, and the cleavage efficiency was 99.9%.Preparation of bacterial ghost vaccine and nactivated vaccine,the 7-days-old chicken were immunized in following groups: GroupⅠ(ghost), GroupⅡ(inactivated vaccine), GroupⅢ(PBS). Chicken in each group were immunized 2 times with 14 days intervals. The serum antibody titers were determined by using indirect enzyme-linked immunosorbent assay(ELISA) every week. And survival rates, internal organs pathological changes, the immune protection efficacy of vaccine were assessed.The results showed that ghost vaccine manifested higher protective efficacy to chicken. challenged with Escherichia coli through activating humoral-mediated immunity. In summary, Escherichia coli ghost vacinne have the higher protective efficacy to chickens challenged with Escherichia coli. So it has the potential to become a new type of Escherichia coli candidate vaccines.