A study of systems for delivering antigens and plasmid DNA for intranasal immunization against tick-borne encephalitis virus.

Our previous studies indicated the possibility for some neurotropic viruses to spread into the brain of immune animals through the olfactory pathway. Thus, nasal mucosa in the olfactory region is likely to be a promising target for mucosal immunization to protect the CNS from neurotropic viral infections. THE MAIN IDEA OF THE RESEARCH: Intranasal immunization inducing mucosal and systemic immune responses blocks the propagation of neurotropic virus into the brain via the olfactory pathway and neutralizes the multiplication of virus in visceral organs, allowing more effective protection against neurotropic infections transmitted by bloodsucking arthropods to be achieved. Thus, study of the efficiency of delivery systems for intranasal immunization against tick-borne encephalitis (TBE) virus is an urgent task in the development of anti-TBE mucosal vaccine. To study intranasal immunization against TBE virus, we have chosen four delivery systems (DSs), namely, (i) biodegradable microparticles, (ii) cationic liposomes, and live attenuated (iii) bacterial and (iv) viral vectors. The gene of TBE virus protein E was inserted into the pcDNA3 plasmid (designated as pcDNA3/E-TBE). Three types of delivery system for plasmid DNA were developed and studied in vitro. The first system, artificial virus-like microparticles (VLP), consists of polyglycan-spermidine complexes that cover pcDNA3/E-TBE DNA. The second system is cationic liposomes with DNA of the plasmid pcDNA3/E-TBE. The third system is an attenuated Salmonella strain containing pcDNA3/E-TBE. The fourth system is a recombinant vaccinia strain with inserted genes of TBE virus proteins C, prM, E, NS1, NS2a, NS2b, and NS3. The DSs were tested in COS-7 and CV-1 cell lines and macrophages by ELISA of cell lysate. The results obtained showed the expression of the E gene in transfected cells, thereby demonstrating that these DSs are suitable for mucosal immunization. High levels of immune response shifted to the Th1 type were detected in BALB/c mice following intranasal immunization with recombinant vaccinia-TBE strain and VLP-pcDNA3/E-TBE. The mice immunized intranasally with recombinant vaccinia-TBE strains were completely protected against intraperitoneal challenge with TBE virus strain Sofjin, whereas intranasal immunization with killed TBE vaccine failed to induce a significant level of protection.