Inactivated Type ‘O’ Foot and Mouth Disease Virus Encapsulated in Chitosan Nanoparticles Induced Protective Immune Response in Guinea Pigs

Foot and mouth disease is a contagious viral disease infecting ungulates, with great economic impact on farmers' income; it is primarily controlled using inactivated vaccines, which have certain limitations, such as short-lived immunity and a lack of mucosal immunity at the portals of virus entry. The present approach aims to exploit the efficiency of chitosan nanoparticle-encapsulated inactivated type 'O' FMDV antigen (FMDV-CS-NPs) to induce mucosal and systemic immune responses in a guinea pig animal model through intranasal and intramuscular administration in comparison with the conventional inactivated, mineral oil-adjuvanted vaccine that is administered systemically. In this study, the FMDV-CS-NPs were prepared by ionotropic gelation, followed by incubation; were characterized for their physical properties and in vitro antigen release; and were found to encapsulate a good amount of antigen. The prepared nanoparticles were assessed for their ability to induce humoral and cell-mediated immune responses by SNTs; indirect ELISAs for serum IgG, IgG1, and IgG2; and nasal washing sIgA and lymphocyte proliferation assays. The preparation induced comparatively more measurable sIgA and systemic immune responses with the intranasal and intramuscular routes of administration, respectively, which are attributable to a specific interaction between the positively charged chitosan and the negatively charged mucosal surface and cell membrane. The challenge infection protected 87.5% of the animals in the FMDV-CS-NP I/M group, followed by 77.7% in the FMDV-CS-NP I/N and inactivated vaccine groups. The outcomes of this study in guinea pigs highlight that chitosan nanoparticle-based vaccine formulations could be employed as a promising antigen delivery system for targeted delivery, devoid of any adverse effect, to induce protective immune responses.