Control of the safety of intranasal vaccine against respiratory syncytial infection of cattle

Due to the widespread prevalence of respiratory viral diseases, particularly respiratory syncytial infection (RSI), among young cattle, the development of vaccines for immunizing young calves is extremely important. One of the most promising areas is the development of intranasal vaccines, as they, along with general immunobiological protection, promote the development of local immunity in the mucous membranes. This method, in turn, allows for immunization without the risk of maternal blockade. At the same time, the safety of such vaccines should be given special attention, as the first days of life are the most critical period for any external influences. The aim of this study was to evaluate the safety of a candidate intranasal RSI vaccine, being developed at the Federal Center for Toxicological, Radiation and Biological Safety, using a laboratory animal model (rabbits). Safety testing was conducted in accordance with GOST 31926-2013 on Chinchilla rabbits (three animals per group). The lyophilized monovalent vaccine was presuspended in sterile saline. Intranasal, intraperitoneal, intramuscular, and subcutaneous administration routes were used for safety testing. Animals were observed for 14 days. The volume of vaccine administered was 1,0 cm3 intranasally, 10,0 cm3 intramuscularly, 10,0 cm3 subcutaneously, and 10,0 cm3 intraperitoneally per animal. The vaccine was considered safe if no deterioration in the general condition, visible tissue changes at the injection site, illness, or death of the animals was observed during this period. In addition, after 14 days, a postmortem autopsy of the rabbits was performed to determine the absence of a systemic negative effect of the vaccine on tissues and internal organs. Autopsy was performed using the Virchow method, with measurement of the weight of internal organs and opening of the nasal cavity to examine the labyrinth mucosa. The monovalent vaccine against RSI did not cause clinical signs of the disease or mortality in rabbits. Visual inspection and comparison of organ weights revealed no differences between the experimental and control groups. These results demonstrate the safety of the vaccine being developed.

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