Antibody response in silver catfish (Rhamdia quelen) immunized with a model antigen associated with different adjuvants

Adjuvants are essential to boost the immune response to inoculated antigen and play a central role in vaccine development. In this study, we investigated the efficacy of several adjuvants in the production of anti-bovine serum albumin (BSA) antibodies in silver catfish. Two hundred and seventy juvenile silver catfish (60–80 g) of both sexes were intraperitoneally vaccinated with BSA (200 µg/fish) alone or mixed to the following adjuvants: Freund’s complete adjuvant (FCA), Freund’s incomplete adjuvant (FIA), aluminum hydroxide (AlOH), Montanide, four types of cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs) and three concentrations of β-glucan, and the immune enhancing property was evaluated by measuring anti-BSA antibodies in blood samples at biweekly intervals. Our results demonstrated that CpGs ODNs and β-glucan were as effective as classical adjuvants (FCA, FIA, AlOH and Montanide) in promoting anti-BSA antibodies and that the kinetics of antibody production induced by all adjuvants used in our study had a similar trend to that observed in other fish species, with a peak at 28 days post-vaccination. These results may be useful for the selection of adjuvants for vaccine formulation intended for silver catfish and for the development of vaccine and vaccination strategies to other fish species.

Aluminum phosphate shows more adjuvanticity than Aluminum hydroxide in recombinant hepatitis-B vaccine formulation

Although a number of investigation have been carried out to find alternative adjuvants to aluminum salts in vaccine formulations, they are still extensively used due to their good track record of safety, low cost and proper adjuvanticity with a variety of antigens. Adsorption of antigens onto aluminum compounds depends heavily on electrostatic forces between adjuvant and antigen. Commercial recombinant protein hepatitis B vaccines containing aluminum hydroxide as adjuvant is facing low induction of immunity in some sections of the vaccinated population. To follow the current global efforts in finding more potent hepatitis B vaccine formulation, adjuvanticity of aluminum phosphate has been compared to aluminum hydroxide. The adjuvant properties of aluminum hydroxide and aluminum phosphate in a vaccine formulation containing a locally manufactured hepatitis B [HBs] surface antigen was evaluated in Balb/C mice. The formulations were administered intra peritoneally [i.p.] and the titers of antibody which was induced after 28 days were determined using ELISA technique. The geometric mean of antibody titer [GMT], seroconversion and seroprotection rates, ED50 and relative potency of different formulations were determined. All the adjuvanicity markers obtained in aluminum phosphate formulation were significantly higher than aluminum hydroxide. The geometric mean of antibody titer of aluminum phosphate was approximately three folds more than aluminum hydroxide. Aluminum phosphate showed more adjuvanticity than aluminum hydroxide in hepatitis B vaccine. Therefore the use of aluminum phosphate as adjuvant in this vaccine may lead to higher immunity with longer duration of effects in vaccinated groups