Antigenic Activity of Canine Enteric Coronavirus Strain "Rich" in Experiments with Rabbits, Ferrets and Guinea Pigs

Abstract

Introduction. Canine enteric coronavirus is a widespread infection, especially dangerous for the puppies of up to 12 weeks old kept in shelters and breeding kennels. The causative agent Alphacoronavirus 1 has a high mutational variability. Foreign sources have repeatedly reported on the isolation and study of the new strains of canine coronavirus infection, including the pantropic ones, causing systemic pathology and death of animals. In this regard, the currently produced vaccines are not effective enough. The present research is intended to substantiate one of the solutions to the problem. The aim of the work is to evaluate the antigenic potential of the canine enteric coronavirus strain “Rich” in terms of its reliability for being included in the combined vaccines against canine viral diseases.Materials and Methods. A purified suspension culture of the canine enteric coronavirus strain “Rich” with the infectivity titers 4.0±0.25 lg TCID50/cm3 (TCID — Tissue Culture Infectious Dose) was used in the work. Antigenic properties were studied in laboratory animals: rabbits, ferrets and guinea pigs. The virus neutralising antibody titers for the canine enteric coronavirus in the blood serum of the experimental animals was determined by a neutralisation test using the “standard” viral dose of 100 TCID50/cm3 in the feline kidney cell culture. The material for the test was obtained from the Cell Culture Bank of the Federal Centre for Animal Health.Results. In animals initially seronegative to the virus, an increase in the CCoV virus-neutralising antibodies (VNA) titers has been recorded 7 days after a single injection of the suspension of the canine enteric coronavirus strain “Rich”. Over the time, the level has been increasing and has reached its maximum value on the 21st day. The mean value in the group of rabbits has been 4.08±0.36 log2 SN50, ferrets — 3.72±0.35 log2 SN50 and 3.77±0.63 log2 SN50, guinea pigs — 4.12±0.34 log2 SN50. Then the values of the virus neutralising antibody titers have decreased, but remained at a fairly high level for 35 days (observation time). At the same time, the physiological state of the animals has not changed.Discussion and Conclusion. In general, the results of the experiments are consistent with the conclusions of the other authors. New data has been obtained by studying the antigenic properties of the strain in ferrets. The strain injected into them has demonstrated the clearly expressed antigenic activity and did not cause a general or local pathological response of the body. The “Rich” is promising for further study and can be included in the combined vaccines against canine and other animal viral diseases.