Adaptation of Contagious Ecthyma vaccine strain to MDBK cell culture and immunity-stability studies in lambs

Abstract

Contagious ecthyma (CE) is a common viral infection in lambs and kids, and still maintains its importance in sheep and goat breeding. Attenuated, live and lyophilized CE vaccines adapted to cell culture are widely used in the fight against CE. The aim of this project was to adapt the CE vaccine strain to Madin Darby Bovine Kidney (MDBK) cell culture and to produce the vaccine, as well as determining the shelf life, stability, innocuity, and immune response in lambs. The titer of the vaccine virus adapted to the MDBK cell culture was determined to be TCID50 106.5/ml. In the innocuity study on mice and guinea pigs, no local or general reactions were observed. . Body temperature of 10 lambs vaccinated by scarification was found to be between normal values (38.2-39.1°C). Neutralizing antibodies belonging to CE virus with VNT could not be detected in blood sera taken on 30th day following the vaccination. As a result of challenge performed with pathogen (E(P)CK5) CE virus, the protection was observed against CE infection in vaccinated lambs. In the stability study, the titers of lyophilized CE vaccine were found to be TCID50 106.5/ml from 1 to 15 months and 106.0/ml at 18, 21 and 24 months during the 24-month storage period at + 4/+8°C. It was determined that the vaccine virus remained as stable at TCID50 106.5/ml titer for 12 hours at 30, 33, 37 and 40˚C and after 12 hours, the virus titer regressed to TCID50 105.75/ml. at 42°C and 45˚C. This study concluded that CE vaccines could be produced in MDBK cell cultures by adapting CE virus to MDBK cell culture.