RESUMO
Tilapia Lake Virus Disease (TiLVD) is caused by Tilapia Lake Virus (TiLV), and it has a cumulative mortality rate of up to 90% in Nile tilapia (Oreochromis niloticus). TiLV is a negative enveloped single-stranded RNA virus with 10 genomic segments. Segment 5 (S5) and segment 6 (S6) were predicted to include a signaling peptide, suggesting that the encoded proteins of these two segments may exist as part of the virus envelope. Based on bioinformatic predictions, the S5 and S6 proteins in this study were produced, including S527-343, S527-172, S5196-272, S630-317, S630-190, and S6200-317. All proteins were tested for their expression in Escherichia coli. Only S5196-272 and S6200-317 were expressed as soluble and insoluble proteins, respectively. The soluble protein was purified using affinity chromatography, whereas the insoluble protein was solubilized using 6 M urea lysis buffer before purification. Both proteins were further purified using gel filtration chromatography, and the results showed a symmetric peak of both proteins suggested a high degree of uniformity in the conformation of these proteins. Antigenicity results indicated that these proteins were recognized by serum from TiLV-infected fish. The immunization tests revealed that serum antibodies levels in Nile tilapia produced by S5196-272 and S6200-317 were significantly increased (p-value < 0.05) at 7 days post-immunization (dpi) compared to antibody levels on Day 0 (D0). All the results combined suggested a potential vaccine candidate of S5 and S6 for TiLV protection in Nile tilapia.
Assuntos
Ciclídeos/virologia , Proteínas Virais , Vacinas Virais , Vírus , Animais , Ciclídeos/imunologia , Doenças dos Peixes/imunologia , Doenças dos Peixes/prevenção & controle , Doenças dos Peixes/virologia , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Proteínas Virais/biossíntese , Proteínas Virais/química , Proteínas Virais/genética , Proteínas Virais/imunologia , Vacinas Virais/biossíntese , Vacinas Virais/química , Vacinas Virais/genética , Vacinas Virais/imunologia , Vírus/química , Vírus/genética , Vírus/imunologiaRESUMO
Diseases caused by motile aeromonads in freshwater fish have been generally assumed to be linked with mainly Aeromonas hydrophila while other species were probably overlooked. Here, we identified two isolates of non-A. hydrophila recovered from Nile tilapia exhibiting disease and mortality after exposed to transport-induced stress and subsequently confirmed their virulence in artificial infection. The bacterial isolates were identified as Aeromonas jandaei and Aeromonas veronii based on phenotypic features and homology of 16S rDNA. Experimental infection revealed that the high dose of A. jandaei (3.7 × 106 CFU fish-1 ) and A. veronii (8.9 × 106 CFU fish-1 ) killed 100% of experimental fish within 24 h, while a 10-fold reduction dose killed 70% and 50% of fish, respectively. When the challenge dose was reduced 100-fold, mortality of the fish exposed to A. jandaei and A. veronii decreased to 20% and 10%, respectively. The survivors from the latter dose administration were rechallenged with respective bacterial species. Lower mortality of rechallenged fish (0%-12.5%) compared to the control groups receiving a primary infection (37.5%) suggested that the survivors after primary infection were able to resist secondary infection. Fish exposed to either A. jandaei or A. veronii exhibited similar clinical signs and histological manifestation.
Assuntos
Aeromonas/fisiologia , Aeromonas/patogenicidade , Ciclídeos , Doenças dos Peixes/mortalidade , Infecções por Bactérias Gram-Negativas/veterinária , Aeromonas veronii/patogenicidade , Aeromonas veronii/fisiologia , Animais , DNA Bacteriano/genética , Doenças dos Peixes/microbiologia , Infecções por Bactérias Gram-Negativas/microbiologia , Infecções por Bactérias Gram-Negativas/mortalidade , Filogenia , RNA Ribossômico 16S/genética , Estresse Fisiológico , Tailândia/epidemiologia , Meios de Transporte , VirulênciaRESUMO
Spent brewer's yeast was autolysed and the insoluble yeast cell wall fraction obtained was used as a raw material for the preparation of brewer's yeast beta-glucan (BYG). A simple alkaline extraction was applied and optimized. The BYG with significantly (P=0.05) high carbohydrate and glucan contents of 92% and 51% (w/w), respectively and with a low protein content of 1.6% (w/w) was obtained by a single alkaline extraction using 5 volumes of 1.0 N NaOH at 90 degrees C for 1 h. In vitro, this glucan significantly (P=0.05) enhanced phenoloxidase (PO) activity of black tiger shrimp hemolymph as compared to controls without added glucan. Also in vivo, an oral administration of 0.2% (w/w) in diets for 3 days significantly (P=0.05) increased the PO-activity of the shrimp. The potential immunostimulating properties of a commercial and other yeast-derived products were also evaluated for comparative purposes.