Testing Novel Inactivation Methods and Adjuvants for Vaccines Against Streptococcus agalactiae in Nile Tilapia Oreochromis niloticus.

Inactivation by hydrogen peroxide and pH manipulation are two novel methods used recently in experimental vaccines against Streptococcus agalactiae in Nile tilapia. Here we describe in detail inactivation using novel methods as well as the classical method of inactivation. These vaccines showed similar moderate efficacy when compared to the conventional formaldehyde vaccine. In addition, we describe the inclusion of adjuvants in a hydrogen peroxide vaccine.

Efficacy of two adjuvants administrated with a novel hydrogen peroxide-inactivated vaccine against Streptococcus agalactiae in Nile tilapia fingerlings.

Streptococcus agalactiae is considered the main bacterial pathogen in cultured Nile tilapia. Formaldehyde-inactivated vaccines are the most accepted method for prevention and control of the disease. However, alternative inactivation methods for S. agalactiae vaccines have not been fully explored. Recently, we developed a hydrogen peroxide-inactivated vaccine against S. agalactiae with moderate efficacy, with the possibility to improve vaccine efficacy by adding adjuvants. The current study compared the efficacy of aluminum hydroxide and Freund's incomplete adjuvant (FIA) incorporated into a novel hydrogen peroxide-inactivated intraperitoneal vaccine against S. agalactiae for Nile tilapia fingerlings. The relative percentage survival (RPS) for aluminum hydroxide-adjuvanted vaccine (59.3%), and FIA-adjuvanted vaccine (77.8%) were higher than the vaccine without adjuvant (40.7%). In addition, fish immunized with aluminum hydroxide-adjuvanted vaccine had significantly higher levels of specific antibodies than control fish at 4 weeks post vaccination (wpv). Blood lymphocytes counts showed a decrease in vaccinated groups when compared to control fish, suggesting white cells migration to the tissues where antigen presentation is ongoing. Fish that received FIA-adjuvanted vaccine exhibited persistence of adjuvant deposits on intraperitoneal surfaces for at least 4 wpv that may be related to its superior performance compared to aluminum hydroxide adjuvanted vaccine, which did not evidence any type of deposit at any sampling times. The results observed in this study demonstrate that hydrogen peroxide-inactivated vaccine administered with either aluminum hydroxide or FIA induce optimal levels of protection, with a superior performance for FIA vaccine, which could be a good alternative to conventional formaldehyde-inactivated vaccines against S. agalactiae, due to its shorter manufacture time, and less toxicity.

Wound healing in Piaractus mesopotamicus supplemented with chromium carbochelate and Saccharomyces cerevisiae / Cicatrização cutânea em Piaractus mesopotamicus suplementados com carboquelato de cromo e Saccharomyces cerevisiae

Wound healing and tissue repair are necessary to ensure survival and health of any organism. The aim of this study was to investigate the impact of supplementation with chromium carbochelate (CC) and Saccharomyces cerevisiae (SC) on wound healing in tropical teleost fish Piaractus mesopotamicus. Thus, fish were distributed into four groups: a) control (without supplementation); b) supplemented with 18 mg/kg of chromium carbochelate; c) supplemented with 0.3% of S. cerevisiae and d) supplemented with an association of both supplements. After 105 days of feeding, full-thickness skin incisions (2.0 x 1.0 x 0.25 cm) were performed removing epidermis and dermis. Macroscopic and histologic observations were carried out at 1, 3, 7, 14, 21, 28, and 35 days after wounding to monitor the healing rate. Opposing fronts advanced gradually and faster each day demonstrating a progressive increase in the healing process over time. The inflammatory process was exacerbated and expansive, with an increase in mucous cells and chromatophores. Although no significant differences were observed between groups on wound retraction and microscopic parameters, fish supplemented with CC and SC showed faster re-epithelialization, greater degree of organization of collagen fibers, and higher neovascularization. We concluded that supplementation with S. cerevisiae and chromium carbochelate improves specific aspects of cutaneous healing process in pacu.(AU)

A cicatrização e reparação de tecidos são mecanismos essenciais para garantir a sobrevivência e saúde de qualquer indivíduo. O objetivo deste trabalho foi avaliar o impacto da suplementação com carboquelato de cromo (CC) e Saccharomyces cerevisiae (SC) sobre a cicatrização no peixe tropical Piaractus mesopotamicus. Para isto, os peixes foram distribuídos em quatro grupos: controle (sem tratamento), suplementados com 18 mg/kg de carboquelato de cromo, 0,3% de S. cerevisiae e associação de ambos os suplementos. Após 105 dias de alimentação, foram realizadas incisões na pele de espessura completa (2,0 x 1,0 x 0,25 cm) removendo epiderme e derme. Avaliações macroscópicas e microscópicas foram realizadas 1, 3, 7, 14, 21, 28 e 35 dias após a indução das feridas, para monitorar a taxa de cicatrização. As bordas opostas das feridas avançaram gradualmente a cada dia, demonstrando o aumento progressivo do processo de cicatrização ao longo do tempo. O processo inflamatório foi exacerbado e expansivo, com aumento no número de células mucosas e cromatóforos. Apesar deste processo, não foram observadas diferenças significativas na retração das feridas e nos parâmetros microscópicos entre os grupos. Peixes suplementados com CC ou Sc apresentaram rápida reepitelização, maior grau de organização de fibras colágenas e de neovascularização inicial. Concluiu-se que a suplementação com S. cerevisiae ou carboquelato de cromo melhora aspectos específicos do processo cicatricial no pacu.(AU)