The uptake of human gamma globulin incorporated into poly (D,L-lactide-co-glycolide) microparticles following oral intubation in Atlantic salmon, Salmo salar L

The use of biodegradable poly (D,L-lactide-co-glycolide) microparticles containing antigen (PLGA) as oral antigen delivery vehicles in pre-smolt Atlantic salmon (Salmo salar L.) was investigated. Test antigen, human gamma globulin (HGG), was dispersed within the copolymer matrix of the PLGA microparticles at a theoretical loading of 24% (w/w). Two polymer ratios were used (85:15 and 50:50 lactide:glycolide) to make microparticles which were mixed in equal amounts for delivery. Atlantic salmon were orally intubated with a known concentration of free or PLGA-encapsulated HGG and sampled at selected post-intubation time intervals ranging from 15 min to 12 weeks. Localisation of HGG in the body tissues and serum was subsequently monitored. Orally delivered free HGG was detected in serum from 15 min to three days post-intubation, in the posterior intestinal epithelium for up to two days and in the kidney for up to seven days. Oral delivery of PLGA/HGG microparticles resulted in HGG being detectable in serum from 15 min to two days with two higher peaks appearing after six days and five weeks. HGG was detected in the posterior intestinal epithelium for up to three days and in the kidney for up to five weeks. In vitro experiments were undertaken to determine the rate of release of HGG from the PLGA suspended in PBS/azide at 15 degrees C over a period of 29 weeks. No HGG release was detected from the 85:15 polymer over the entire period. The 50:50 polymer ratio microparticles released about 50% of the antigen by two weeks and the remaining 50% was released between eight and 11 weeks. No further release was detected by week 29. (C) 1996 Academic Press Limited