De ontwikkeling van toedieningsvormen voor orale vaccinatie

status: publishe

Development of a lag time coating for drug-layered fish feed pellets

The purpose of this work was to develop a release-delaying coat for drug-layered fish pellets, in order to prevent a premature release of the drug in the tank water but allowing a rapid release after uptake by the fish. Blank pellets were prepared in a rotary processor and drug layered in a Wurster coater with bovine serum albumin or riboflavin using hydroxypropyl methyl cellulose (HPMC) as a binder. On the drug-loaded pellets, different mixtures of ethyl cellulose (EC) and HPMC were applied as the release-delaying coat. The aim was to obtain less than 10% drug release during the first 10 min followed by a fast release after the "lag" period, resulting in a sigmoidal release profile. In order to prevent coat bursts it was necessary to increase the amount of plasticizer from 20 to 40% triethylcitrate. To have a complete coat around the pellets, the thickness of the coat (amount EC) was important up to a certain level. The EC/HPMC ratio had a decisive influence on optimizing the permeability of the coating and realizing a sigmoidal release profile. The release rate was studied as a function of several formulation variables and physicochemical parameters (salinity, pH, and temperature) of the dissolution medium as the coating system is intended for different fish species. Salinity of the water proved to be important as well as the temperature. The developed system seems to be promising for a lot of ichthyologic applications, although it has to be evaluated for each intended drug, keeping in mind the properties of the particles to be coated, the fish species, and the environment.status: publishe

Mucosal response in African catfish after administration of Vibrio anguillarum O2 antigens via different routes

The aim of this study was to investigate the possibility of mucosal vaccination in African catfish (Clarias gariepinus) with Vibrio anguillarum O2 bacterins. The antigen was administered via different routes: anal intubation, oral administration, intraperitoneal injection and immersion. To monitor the antigen uptake, a competitive ELISA was used. The antibody response was measured using an indirect ELISA. Increased antibody levels were found in bile and mucus upon anal intubation, which was not the case after intraperitoneal injection. The data indicate that oral vaccination of fish may be possible when antigens can reach the second gut segment in sufficient quantities and in the right form as confirmed by the recorded substantial induction of systemic and mucosal immunity. The results obtained are a strong indication for mucosal immune response and the two compartmental models for immune response in fish.status: publishe

Oral vaccination of African catfish with Vibrio anguillarum O2: effect on antigen uptake and immune response by absorption enhancers in lag time coated pellets

The impact on antigen uptake and antibody response by the addition of absorption enhancers to Vibrio anguillarum O2 antigen was studied in oral vaccination trials of African catfish (Clarias gariepinus). Oral vaccination was achieved by feeding lag time coated pellets. The lag time coat prevents premature release of the encapsulated vaccine in the tank, before ingestion of the pellets by the fish. To monitor the antigen uptake, a competitive ELISA was used. The antibody response was measured using an indirect ELISA. Feeding of bacterin-layered pellets without absorption enhancers resulted in a rather low antigen uptake and antibody levels. The addition of absorption enhancers such as sodium salicylate, sodium caprate and vitamin E TPGS increased the serum antigen levels and specific antibody levels in the systemic circulation. Skin mucus antibody levels were higher after oral vaccination compared to the IP and control group. The addition of absorption enhancers in the oral groups further increased the antibody levels obtained in the skin mucus.status: publishe

Vaccination of African catfish with Vibrio anguillarum O2: II. Oral intubation with vaccine-containing pellets

The aim of this study was to investigate the success of oral vaccination application in African catfish using Vibrio anguillarum O2 bacterins. The antigen uptake was followed by competitive enzyme-linked immunosorbent assay (ELISA). Serum antibody response was measured using an indirect ELISA. Several in vivo administration methods were investigated. Intraperitoneal injection gave the highest absorption rate, with high antibody levels in the systemic circulation. Oral intubation of bacterin-layered pellets resulted in low antigen uptake and low antibody levels. The addition of absorption enhancers increased the serum antigen levels. An enteric coating applied on the pellets containing vaccine did not improve the immune response.status: publishe

Vaccination of African catfish with Vibrio anguillarum O2: I. ELISA development and response to IP and immersion vaccination

The aim of this study was to investigate African catfish (Clarias gariepinus) vaccination with Vibrio anguillarum O2 bacterins. To monitor the antigen uptake, a competitive enzyme-linked immunosorbent assay (ELISA) was developed. Serum antibody response was measured using an indirect ELISA. Sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblot data that characterize the immunoglobulin molecule of the African catfish are presented. The impact of acid conditions on the antigen proved to be stable above pH 4. A partition coefficient was calculated to determine the ability of transepithelial uptake. Two in vivo administration methods were investigated in the study. Intraperitoneal injection gave the highest absorption rate with high antibody levels in the systemic circulation, whereas immersion did not induce significant serum antibody levels.status: publishe