ABSTRACT
By expression of foreign antigens in attenuated strains derived from bacterial pathogens and in non-pathogenic commensal bacteria, recombinant vaccines are being developed that aim to stimulate mucosal immunity. Recent advances in the pathogenesis and molecular biology of these bacteria have allowed rational development of new and improved bacterial carriers and more effective gene expression systems. These advances have improved the performance and versatility of these delivery systems to induce mucosal immunity to recombinant antigens in animal models. Application of these (improved) technologies for development of human vaccines is still limited and awaits further exploration.
Subject(s)
Immunity, Mucosal , Vaccines, Synthetic/administration & dosage , Animals , BCG Vaccine/administration & dosage , Bacteria/genetics , Bacteria/immunology , Drug Delivery Systems , Genetic Vectors , Humans , Lactobacillus/genetics , Lactobacillus/immunology , Lactococcus lactis/genetics , Lactococcus lactis/immunology , Salmonella/genetics , Salmonella/immunology , Staphylococcus/genetics , Staphylococcus/immunology , Streptococcus/genetics , Streptococcus/immunology , Vaccines, Attenuated/administration & dosage , Vaccines, Attenuated/genetics , Vaccines, Synthetic/genetics , Vibrio cholerae/genetics , Vibrio cholerae/immunologyABSTRACT
Induction of oral tolerance against ferritin, recombinant surface glycoprotein of viral haemorrhagic septicemia virus (KLG18) and ovalbumin (OVA) was studied in carp. Feeding of ferritin or KLG18 resulted in lower Ab titres compared to unprimed controls when animals were intramuscularly (i.m.) injected with protein 10 weeks later and sampled 21 days after this injection. After administration of OVA by different routes (oral, anal, i.m.) and i.m. injection with OVA + Freund's incomplete adjuvant 2 months later, only a few fish responded to OVA as measured by serum Ab titres. Responsiveness to OVA appeared to be carp strain dependent. When an isogenic carp strain was selected for an optimal response to i.m. injection with OVA, this carp strain did not develop oral tolerance after feeding. In contrast, 6 x feeding high doses of OVA on subsequent days, resulted in immunological memory formation. Oral tolerance can be induced in carp, but differences in tolerance induction may depend on the protein used. A possible role of genetic factors in the induction of oral tolerance in fish is discussed.