Efficacy of feed-based adjuvant vaccine againstStreptococcus agalactiaeinOreochromisspp. in Malaysia

Abstract

This study was conducted to determine the systemic, mucosal immunity and protective capacity of the feed‐based adjuvant vaccine (FAV) of Streptococcus agalactiae following oral vaccination against streptococcosis in tilapias. Two hundred and sixteen red tilapia fish were divided into three major groups. Each major group consisted eight tilapia kept in nine 2000 L glass aquaria. At day 0, all fish from the FAV group were fed with feed that had been incorporated with an adjuvant, while fish in the feed‐based vaccine (FNV) group were fed with vaccine incorporated into the pellet without adjuvant. Fish in the control‐unvaccinated group, FC, were fed with normal commercial pellet. Booster dose was performed on day 14 post immunization. Fish from each group were sacrificed on a weekly basis for the entire 7 weeks. Serum, body mucus and gut lavage fluid were evaluated for antibody responses by indirect ELISA, while histological examination was carried out on the gut following intraperitoneal challenge. The FAV group had a significantly higher protection (P < 0.05) following challenge with 3.4 × 109 CFU mL−1 of live S. agalactiae than FNV group. This level of protection may be due to high antibody responses, increase in size of gut‐associated lymphoid tissue and high number of lymphocytes in the FAV group.

An Overview of Vaccination Strategies and Antigen Delivery Systems for Streptococcus agalactiae Vaccines in Nile Tilapia (Oreochromis niloticus)

“…Nur-Nazifah et al [13] compared the efficacy of a recombinant vaccine encoding the LPXT cell wall surface anchor family protein of S. agalactiae with an IWC-vaccine in which they showed that both vaccines produced high IgM levels in serum and mucus that corresponded with low post challenge infection and high RPS in vaccinated fish. Mohd et al [43] showed high protection in tilapia orally vaccinated using an IWC-vaccines while Huang et al [12] used a live recombinant S. typhimurium vector vaccine encoding the Sip protein and produced high protection levels against S. agalactie . These studies show that both live and inactivated vaccines can produce high protection levels when orally administered in tilapia.…”

Histological assessments of intestinal immuno-morphology of tiger grouper juvenile, Epinephelus fuscoguttatus

“…High concentrations of lymphoid cells were observed in the posterior intestine, and support the conclusion that posterior intestine plays a major role in immunity (Buddington and Diamond, 1987). Similarly, Ezeasor and Stokoe (1981) found high phagocytic activities in the posterior intestine compared to another regions while a study in red tilapia revealed accumulation of lymphoid cells in the lamina propria of posterior intestine following oral vaccination with adjuvanted feed-base vaccine against streptococcosis (Firdaus-Nawi et al, 2012). Due to the immunity functions but less nutrient absorptive capacity (Buddington and Diamond, 1987), posterior intestine requires large numbers of lymphoid cells and the lamina propria should be thick to provide enough space for the lymphoid cells.…”

“…Besides function as a lubricant for smooth movement of feed particles, mucus also provides innate host defense by acting as a first line of immunity against invasion of harmful pathogen (Kim and Samuel, 2010). Intestinal mucus secreted in fish contains antibody (Grabowski et al, 2004; Firdaus-Nawi et al, 2012), lysozyme (Lie et al, 1989), glycoprotein (Shephard, 1994), complement components, lectins and some antimicrobial agents (Ingram, 1980; Alexander and Ingram, 1992). In this study, goblet cells were found scattered among the epithelial lining in all three regions of the intestine, but showed no significant difference in numbers until 90 days old.…”

“…Prior to sampling, five fish from each age group were sacrificed and swab samples from the organs were collected for bacterial and parasitic examinations. This was to ensure that the fish were free from bacterial and parasitic diseases (Firdaus-Nawi et al, 2012). …”

“…Following 24 h fixation, the samples were prepared for histological examination according to Firdaus-Nawi et al (2012). The slides were examined under a light microscopy using Nikon NIS-Element D 3.2 Image Analyzer (Nikon Instruments Inc., USA).…”