Oral Vaccines for Prevention of Bacterial Infections: Development Strategies and Prospects

Abstract

Oral vaccines are drawing more attention due to their ease of administration, lesser invasiveness, and greater safety in general. The review discusses the benefits of oral vaccination in stimulating humoral and cellular immune responses at the systemic and mucosal level to provide expanded and longer-lasting protection. Aspects related to the structure of the intestine and immunological recognition of the antigen during the transformation process after penetration into the intestine are analyzed. Approaches used to improve the effectiveness of oral vaccines are considered. Problems such as instability and lack of effectiveness of oral vaccines are discussed, as well as recent developments of adjuvants and delivery systems based on mineral salts, substances of microbial origin, saponins, polymers, micro- and nanoparticles, liposomes, which have the potential to increase the effectiveness of oral vaccines. A brief analysis of licensed oral vaccines is given and the data on the development of prototype vaccine preparations using modern methods of genetics, molecular biology and immunology, as well as the mechanisms of inducing an immune response are summarized.