THE POTENTIAL USE OF POLY(METHACRYLIC ACID) HYDROGELS FOR ORAL-ADMINISTRATION OF DRUGS AND VACCINES TO RUMINANTS

Poly(methacrylic acid) hydrogels were investigated for the delivery of a model antigen to the lower gastrointestinal tract of sheep; Hydroge ls were tested by incorporating a radiopaque material, administering t hem orally to a sheep, and then radiographing the sheep. The potential for loading high molecular weight proteins into hydrogels was determi ned by absorbing hydrogels with culture supernatants of the bacterium Pasteurella haemolytica. The hydrogels were dried, hydrated, and the c ulture supernatants eluted. The eluents were assayed for the presence of the 102 kDa proteinaceous exotoxin. The hydrogels readily bypassed the first stomach and swelled releasing a radiopaque dye into the lowe r gastrointestinal tract. Chromium-loaded hydrogels were then administ ered to a sheep and intestinal contents were collected for 5 days. Chr omium was detected in the intestinal contents of the sheep for 96 h wi th peak levels detected at 12-15 h after administration. Eluents of th e hydrogels loaded with culture supernatants contained readily detecta ble amounts of the proteinaceous exotoxin. PMA hydrogels were then abs orbed with a vaccine consisting of culture supernatants of a pulmonary bacterium P. haemolytica. Hydrogels containing vaccine were administe red orally to calves. Calves were challenged by an intrabronchial dose of bacteria. The length of time each calf survived was noted. All sur viving calves were killed 3 days post-challenge. A post-mortem examina tion was performed to evaluate the severity of the pneumonic lesions. Vaccinated calves had less pneumonia and lived longer than control cal ves. Results of this study indicate that poly(methacrylic acid) hydrog els could be used to administer drugs and proteinaceous vaccines orall y to ruminants.