Oral vaccination of animals with antigens encapsulated in alginate microspheres

Most infectious diseases begin at a mucosal surface. Prevention of infectio n must therefore consider ways to enhance local immunity to prevent the att achment and invasion of microbes. Despite this understanding, most vaccines depend on parenterally administered vaccines that induce a circulating imm une response that often does not cross to mucosal sites. Administration of vaccines to mucosal sites induces local immunity. To be effective requires that antigen be administered often. This is not always practical depending on the site where protection is needed, nor comfortable to the patient. Not all mucosal sites have inductive lymphoid tissue present as well. Oral adm inistration is easy to do, is well accepted by humans and animals and targe ts the largest inductive lymphoid tissue in the body in the intestine. Oral administration of antigen requires protection of antigen from the enzymes and pH of the stomach. Polymeric delivery systems are under investigation t o deliver vaccines to the intestine while protecting them from adverse cond itions that could adversely affect the antigens. They also can enhance deli very of antigen specifically to the inductive lymphoid tissue. Sodium algin ate is a readily available, inexpensive polymer that can be used to encapsu late a wide variety of antigens under mild conditions. Orally administered alginate microspheres containing antigen have successfully induced immunity in mice to enteric (rotavirus) pathogens and in the respiratory tract in c attle with a model antigen (ovalbumin). This delivery system offers a safe, effective means of orally vaccinating large numbers of animals land perhap s humans) to a variety of infectious agents. (C) 1999 Elsevier Science Ltd. All rights reserved.