Novel acellular vaccines against brucellosis based on particle immunomodulators

Zusammenfassung

Ovine brucellosis is a very contagious zoonotic disease distributed geographically worldwide and constitutes a very important zoosanitary and economic problem. The control of the disease includes animal vaccination and slaughter of infected flocks. However, the commercially available vaccine in most countries is based on the attenuated strain Brucella melitensis Rev 1 which present important safety drawbacks. Subcellular vaccines exhibit important advantages to face these handicaps. In this context, the hot saline (HS) subcellular antigenic extract from B. ovis has been proved to be highly immunogenic. However, due to its non-replicant nature, adequate adjuvants have to be associated. The need of an adequate adjuvant capable of increasing the immune response and protection, lead us to suggest the use of poly(å-caprolactone) microparticles and poly(anhydride) nanoparticles. To exploit the potential of these systems for mucosal immunization, nanoparticles were also surface decorated with mannosamine in order to specifically target mannose receptors highly expressed on the immune system cells. To achieve our purpose we designed and studied the biopharmaceutical properties of mannosylated (MAN-NP-HS) and conventional (NP-HS) poly(anhydride) nanoparticles (chapter 3 and 4), with further in vivo protective evaluation after subcutaneous administration in rams (chapter 5) and mice. In mice, the immunological effect of the naparticulate vaccines was also evaluated after administration by different routes: ocular, nasal, oral, and intradermal (chapter 7). MAN-NP-HS revealed excellent characteristics as antigenic delivery systems and immunomodulators throughout the ocular mucosa, by improving mucosal delivery and enhancing immune response. In this course, biodistribution studies were also performed with fluorescent and radiolabelled nanosystems after its ocular immunization (chapter 8). The in vivo biodistribution revealed that MAN-NP-HS were mainly located in the gastrointestinal tract (GALT), nasal (NALT) and ocular mucosa (EALT), probably due to their specific target and strong bioadhesive performance, thus enhancing the antigen delivery to the mucosal associated lymphoid tissue (MALT). Since the ophthalmic route requires accomplishing the pharmacopoeia sterility requirements, the influence of ã-irradiation on the nanosystems was also evaluated (chapter 6). Their effective protection and intrisinc avirulence, make them a promising anti-Brucella acellular vaccine candidate.