Experimental Intranasal Immunization against Respiratory Viruses

The most common method of influenza prevention is intramuscular administration of vaccines, which causes a higher antibody response than subcutaneous. However, such routes of antigens administration result in the predominant formation of serum IgG against influenza viruses, while intranasal administration promotes higher titers of both IgG and IgA than intramuscular vaccination. Based on the fact that this infectious agent enters the body through the mucous membranes of the respiratory tract, we developed the concept of local etiologically adequate vaccination, based on the statement that the vaccine should be administered in the same way as the infection, i.e. in cases of respiratory infections it should be intranasal or oral administration of vaccine material. So, the aim of this work was to demonstrate the benefits of local vaccination against respiratory viruses, as well as the use of nanocarriers in such vaccination and possible cross-antigen reactions by hemagglutinin between antigens of influenza virus and severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2). Methods. The study was performed using Wistar rats in 3 series of experiments. At first series we investigated the comparative immune response to influenza Influvac® vaccine (Abbott, The Netherlands) against A and B type influenza viruses, which was administered intranasally, per os and subcutaneously once at a dose of 1.5 μg of hemagglutinin. Animals from group 2were similarly administered with the same amount of vaccine with and without cerium dioxide nanoparticles (CeO2). Animals of group 3 intranasally received an identical volume of sodium chloride solution (placebo control). Rats were removed from the experiment by decapitation one week after the immunization. Tissue homogenates were prepared from the trachea of animals of all groups by homogenization at the rate of 100 mg/mL of 0.9% sodium chloride solution. The homogenates were kept at 2°C for 18 hours and then centrifuged at 120 g for 20 minutes (cold centrifuge NF800R, Turkey). The obtained extracts and sera were stored at a temperature of -20°C until the determination of antibodies titers to hemagglutinins of A and B influenza viruses in the reaction of hemagglutination inhibition and titers of interferons (IFN) -α and -γ and using enzyme-linked immunosorbent assay using Elabscience (USA) reagents and Stat Fax 2100 Microplate Reader (USA). In the 3rd series of experiments, the content of antihemagglutinins in the trachea and serum after immunization of animals with nucleocapsid antigen of SARS-Cov-2 coronavirus (recombinant antigen produced by PJSC SPC “Diaproph-Med”, Ukraine) at a dose of 2.5 μg in 0.2 mL of Hanks’ solution was determined. The antigen was administered intranasally or subcutaneously and then all other steps of the experiments were similar to those described below for the 1st series of experiments. Results. Conducted experimental studies aimed to develop new approaches and technologies for vaccination against respiratory viruses, which enter mainly through the upper respiratory tract, confirm the concept of the feasibility of local intranasal vaccination against influenza and other respiratory viruses. The data obtained during the research confirm more effective appearance of protective local immunity both in terms of humoral immune response and interferon protection of the respiratory tract during intranasal vaccination. The use of cerium dioxide nanoparticles in local vaccination may increase the effectiveness of this approach to stimulate the production of antibodies to influenza virus antigens in the upper respiratory tract. Finally, the advantages of local intranasal immunization with SARS-CoV-2 N-antigens over their systemic administration suggest that local intranasal vaccination against coronavirus antigens may also be more effective than systemic administration of antigens of this virus, which requires further research for clinical trials. Conclusions. Intranasal immunization of animals with influenza A and B virus antigens and N-antigen of SARS CoV-2 is more effective for creating local protective immunity in the respiratory system compared to parenteral administration of the antigen. The use of cerium dioxide nanoparticles together with the vaccine resulted in more effective local immune response to respiratory virus antigens.