| In decades, with rapid development of aquaculture industry with the high-density and the production on a large scale, the diseases of cultured fish took place frequently, especially the bacteriosis, with high variety, morbidity and mortality, caused huge economic loss to aquaculture. A frequent use of chemical and antibiotic resulted in occurrence of drug- resistant pathogenic strains, simultaneously brought about severe public health and sanitation problems, such as drug residue and food security, to which our human being have to faced and challenged with. In modern aquaculture industry, vaccination will offer a good alternative to strategy of fish disease provention in the highly qualitative fishery cultivation. So developing highly effective vaccine for cultured fish have been an urgent matter in aquaculture industry. In present studies, we mainly focused on Streptococcus iniae, as one of important pathogens in cultured freshwater fish and seawater fish, which caused severe economic losses to the aquaculture industries, developing a vaacine to prevent streptococcosis of fish. The efficacy of S. iniae inactivated vaccine in the freshwater fish tilapia (Oreochromis niloticus) and the sea water Japanese sea perch (Lateolabrax japonicus) were evaluated, the best inoculated doses of antigen were balanced and the best immune adjuvant were choosed. Simultaneously the use of immunostimulants in fish was discussed preliminarily. Our experimental results formed a good scientific basic for the preparation and application of Streptococcus iniae inactivated vaccine in cultured fish.Formalin killed whole-cell vaccines were prepared with sea water strain HD-1, HD-4 and freshwater strain TBY-1, TBY-5 of S. iniae respectively. Tilapia were vaccinated with vaccine (1×1010 colony-forming units of bacterial per fish) mixed with equal doses in volume of Freund's ajuvant by intraperitoneal (i.p.) injection, through twice immunization to fish, the protective efficacies of four kinds of vaccines were compared by challenge of fish with the corresponding strain on the 35th day after the first vaccination. The number of fish died in each group was recorded in 14 days, the relative percent survivl (RPS) of each immune group was statisticsed and the titer of serum antibody in each group fish was detected by bacterial agglutination assays to be determined the efficacy of vaccine on fish. The results showed that the Freund's ajuvant vaccine of S. iniae sea water strain HD-1 could present 93.6% RPS for vaccinated fish and the serum antibody titer of immunized fish reached 1:64; TBY-1 strain vaccine had a 100% RPS with high serum antibody titer by 1:64. As a result, we suggested that HD-1 and TBY-1 strain could be used as the candidate strains to prepare vaccine of cultured fish.To detect the sensitivity of mariculture fish to S. iniae, Epinephelus coioides, Sciaenops ocellatus, Lutjanus erythopterus, Trachinotus ovatus and Lateolabrax japonicus, as main mariculture species in Guangdong, were infected with HD-1 strain. The result showed that Lateolabrax japonicus were most sensitive to S. iniae seawater HD-1 strain, which would be as animal model for inactivated S. iniae vaccine experiment.Three types of inactivated S.iniae HD-1 strain vaccine in bacterial concentration of 1×1010 CFU×rnL-1,1×109 CFU×mL-1 and 1×108 CFU×mL-1 mixed with equal volume of white oil adjuvant were prepared. After immunized Japanese sea perch (L. japonicus) had been challenged with corresponding virulent strain, the fish vaccinated with 1010 CFU×mL-1, 109 CFU×mL-1, 108 CFU×mL-1 doses showed high immune protection with RPS of 100%, 92.5%, 85% and high antibody titer with 1:16, 1:64, and 1:32 respectively, while all fish in non-immnized control group died. Antigen dose of 109 CFU×mL-1 concentrations was most suitable for S.iniae HD-1 strain vacine to immunize: maricultured fish.To detect immunoprotection of S.iniae HD-1 strain vacine to Japanese seap erch (L. japonicus), two type of vacine with a dose of 1×109 CFUxmL-1 killed HD-1 strain mixed with equal volume of white oil and alhydrogel adjuvant respectively were prepared and used to vacinate 40 tail fish. After experimenal fish were challenged with corresponding virulent stains, the group immunized with white oil and alhydrogel adjuvant vaccine had high immuoprotection with RPS of 92.5% and 82.5%, and high antibody titers with 1:64 and 1:32 respectively, while all fish in non-immnized control group died. So we thought that white oil adjuvant vaccine could elicit good immune effect and protect Japanese sea perch from streptococcicosis.Respectively added the Levamisole and the aloe polysaccharide of traditional Chinese medicine by a certain quantity into the S.iniae HD-1 strain vacine with a dose of 1×109 CFU×mL-1 killed HD-1 strain mixed with equal volume of white oil, simultaneously the aloe polysaccharide alone injection group in white oil adjuvant vaccine foundation, the vaccine with white oil adjuvant group and one non-immunized control group. After experimenal fish were challenged with corresponding virulent stains, it was not significant (p＞0.05) difference with RPS in experimental groups. The antibody titer of the aloe polysaccharide alone injection group were higher than the other groups (p＜0.05); the antibody titer of Levamisole group was lower than the white oil adjuvant group (p＜0.05), the other gorups were not significant differently. Measurese the changing tendency of antalzyme in each group's serum showed that the immunoenhancer of aloe polysaccharides alone injection group obviously higher than the other groups (p＜0.05). our experiments proved that the immunoenhancer of aloe polysaccharides can stimulate fish to produce nonspecific immune response.
|
PDF Full Text Request