A survey on achieving recombinant DNA vaccine (live delivery) against Streptococcusis in rainbow trout (Oncorhynchus mykiss) immunization

The main purpose of this study was to survey on achieving recombinant DNA vaccine (live delivery) against Streptococcusis for rainbow trout (Oncorhynchus mykiss) Immunization. Initially, a total of 515 samples were collected from the head kidney of diseased fish (weighing 50_200g) in 72 farms in 8 provinces. Approximately, 40% (206 samples) of specimens were infected with Streptococcus species. Then isolated 172 DNA samples were and consequently, five pathogenic species have been identified, including Streptococcus iniae, Streptococcus faecium, Streptococcus agalactiae, Streptococcus dysgalatiae, and Streptococcus uberis. The enzyme phosphoglucomutase (PGM) has recently been discovered to play an important role in polysaccharide capsule production and virulence in S. iniae. Therefore, S. iniae was initially isolated S. iniae and cloned the phosphoglucomutase gene. Then, the PGM gene was amplified successfully and cloned in the pTZ57R cloning vector. The recombinant plasmid was subcloned into the pETD uet-l expression vector by restriction enzymes and confirmed by PCR. Meanwhile, for amplifying simA and cpsD genes were used universal primers pNZ8148 and special for simA and cpsD genes. The recombinant bacteria Lactococcus lactis (NZ9000) was used to transform the plasmid into L. lactis. Vaccination was performed by bath and injection (peritoneal) methods. The efficiency of g2 was better than g1in these two methods and in all of the groups. The detection of anti S. iniae antibody and determination of IgM level was carried out by using ELISA. The results revealed that there was a significant (p<0.05) difference between the level of IgM in both two methods and experiment groups compared to the control group. The results of the challenge of vaccinating fish with S. iniae showed that fish RPS in all groups were more than 50 percent while in the control group was 21.43 percent. The highest fish RPS belonged to group 5(61.25 percent) and statistical analyses revealed a significant (p<0.05) difference between fish vaccinated RPS, compared to the control group.