Inactivation of Streptococcus iniae in substitution of chemicals and drugs to develop vaccine for mono-sex Nile tilapia

Abstract

Streptococcus iniae is an important pathogen that can cause a broad range of disease in aquatic animals. To avoid the use of antibiotics and drugs, it is critical to identify protective antigens for developing highly effective vaccines against this pathogen. Vaccination is the most effective means of preventing infectious diseases; however, few vaccines are effective against Streptococcus iniae (S. iniae) in monosex Nile Tilapia. This work presents an efficacious and safe vaccine against S. iniae infections in monosex Nile tilapia (Oreochromis niloticus). The vaccine candidate S. iniae F-1 strain administered by intraperitoneal (i.p.) injection, and consisted of inactivated antigens; both the vaccinated and nonvaccinated fishes were challenged intraperitoneally with S. iniae (1 × 10 7 CFU ml −1 ) isolates and PBS (negative control). Peripheral blood samples were collected for SDS-PAGE, phagocytosis and agglutination assays. Present results indicated that immunoglobulin M (IgM) was maximally expressed in the low-amperage electric current inactivated (ECKC) vaccinated group at 3 months post-secondary vaccination (PSV). Phagocytic activity and index increased significantly in (ECKC) vaccinated group. Furthermore, fish in (ECKC) vaccinated group exhibited significantly elevated agglutination titers compared to fish in the control group, in which almost no agglutination reaction was detected. In the efficacy test, the vaccinated fishes had a significant increase in RPS (69 and 89, respectively); the percentage mortality declined from 83 ± 0.6 and 74 ± 0.7 in challenged and control fishes to 25% ± 0.8% and 8% ± 0.8% in vaccinated and challenged fish groups, respectively. Furthermore, the level of protection observed in the field trial closely resembled that achieved on a laboratory scale. Therefore, EC-killed showed the highest molecular weight 31 kDa in SDS-PAGE and Western blot and increased RPS (91%), suggested that the EC-killed cells of S. iniae could play an important role in immunizing mono-sex Nile tilapia. The EC-killed cells of S. iniae will may safe and long-lasting protection against streptococcosis.

Immune responses and immunoglobulin gene expression of Streptococcus agalactiae infected Nile Tilapia and the effective dose of inactivated Streptococcus agalactiae vaccine for Nile tilapia (chitralada 3 strain) in Thailand

“…The bacteria generate the streptolysin S and O for blood hydrolysis and adhesion of cell surfaces, protect lysozyme, and replicate in serum or blood into target organs [4,5,6]. An infected sh exhibits external signs through abnormal behavior (swirling behavior, lethargy, bent bodies, and disorientation) and eye lesions (endophthalmia or exophthalmia), abscesses, skin hemorrhages around the mouth or at the base of the n, and ascites [7]. The internal signs include septicemia, hemorrhages, and in ammation in the liver, spleen, kidney, heart, brain, eye, intestinal tract, and peritoneum.…”

Correlation of Streptococcus agalactiae concentration on immune system and effective dose of inactivated vaccine for Chitralada 3 strain Nile tilapia (Oreochromis niloticus) in Thailand

“…The bacteria generate the streptolysin S and O for blood hydrolysis and adhesion of cell surfaces, protect lysozyme, and replicate in serum or blood into target organs [ 4 – 6 ]. An infected fish exhibits external signs through abnormal behavior (swirling behavior, lethargy, bent bodies, and disorientation) and eye lesions (endophthalmia or exophthalmia), abscesses, skin hemorrhages around the mouth or at the base of the fin, and ascites [ 7 ]. The clinical signs and lesions effects of S. agalactiae infection include septicemia, hemorrhages, and inflammation in the liver, spleen, kidney, heart, brain, eye, intestinal tract, and peritoneum.…”