Study of in vitro reproduction of infectious pancreatic necrosis virus (IPNV)

Abstract

The aim of the work was to study the in vitro reproduction of new emergent isolates of infectious pancreatic necrosis virus (IPNV) in purpose to determine virulence properties. The new strains of IPNV isolated from trout farms in Ukraine during 2021-2022 were investigated. For this purpose, RTG-2 cell line was used, on which the infectious titer of the virus and the manifestation of CPE signs were determined. The infectious titer of selected isolates in RTG-2 cell line ranged from 1.1x103 to 1.0x107 TCID50/ml Isolated IPNV strains caused low (≤25 %), moderate (≤50 %) and high (≥70 %) mortality rates in trout fry. Based on biological properties and indicators of infectious titer, the investigated isolates VN11, VN18 and VN29 were determined as with low virulence, and isolates VN20, VN30, VN32 and VN39 were classified as highly virulent. Among the highly virulent isolates, VN32 had the highest titer of 1.0x107 TCID50/ml and caused mortality in rainbow trout with an average weight of 100 g. The IPNV strain isolated from the brook trout had an infectious titer of 1.58x106 TCID50/ml and caused fry mortality ranged from 15 to 25 %. The number of detected isolates and their cultural properties testify to the biodiversity of strains for the Infectious pancreatic necrosis virus in Ukraine. How many newly discovered isolates of the IPNV belong to one or another genotype remains to be determined. For this, a study of the nucleotide sequence of the gene encoding the capsid protein VP2 will be conducted, on the basis of which it will also be possible to determine virulence by changes in amino acids sequences