ABSTRACT
INTRODUCTION: Outbreaks of infectious diseases seriously hinder the preservation and increase of the number of small ruminants. Such infections include sheep pox virus (SPPV). According to the OIE data of 2021, SPP outbreaks were registered in countries such as Turkey, Israel, China, Maldives, Mongolia, Thailand, Russia, Algeria, Kenya, and in 2019 in Mangistau and Atyrau regions. In Kazakhstan annually conducts routine immunization of sheep at risk with a live attenuated vaccine produced by RIBSP. MATERIALS AND METHODS: The object of the study was the vaccine strain of NISHI and the virulent strain A of the sheep pox virus. The virus was propagated in Vero cells. To determine the harmlessness and immunogenicity, sheep of the Kazakh fine-wool breed aged from 6 to 12 months were used. Virological, serological and immunobiological methods were used in the study. RESULTS: The results of the adaptation of the NISHI strain of SPPV to the Vero cell line are presented. Five passages in Vero cells resulted to the adaptation of the NISHI strain with the manifestation of a cytopathogenic effect specific to SPPV with a titer of 6.50 lg TCD50/ml. Following immunization, the formation of immunity was observed in animals on day 7 with an average protective titer 1.8 log2, which increased by day 21 to 4.33 log2. CONCLUSION: It has been established that the NISHI strain of SPPV retains its virological and immunobiological properties during reproduction in a Vero cell line.