Tiantian Wu , Yulong Wang , Hui Li , Linjin Fan , Nan Jiang , Li Gao , Kai Li , Yulong Gao , Changjun Liu , Hongyu Cui , Qing Pan , Yanping Zhang , Xiaomei Wang, Xiaole Qi 

Vet Microbiol.2020Jun;245:108700.doi:10.1016/j.vetmic.2020.108700. Epub 2020 Apr 25. 

Abstract

Infectious bursal disease virus (IBDV) is the causative agent of infectious bursal disease (IBD), an important immunosuppressive disease seriously threatening poultry farming worldwide. Since the identification of the classic strain in 1957, variant IBDV, very virulent IBDV, and novel variant IBDV have successively emerged brought severe challenges. Over the years, attenuated, intermediate, and intermediate-plus live vaccines have been developed to control the disease. The coexistence of various strains in flocks increases the probability of homologous recombination, and in this study, a naturally occurring homologous recombination between a novel variant strain and an intermediate vaccine strain of IBDV was first identified. Sequence analyses demonstrated that the IBD16HeN01 strain was a recombinant IBDV incorporating the skeleton of the novel variant IBDV (SHG19-like strain), where the 3' region of segment A (nt 1539-3260) was replaced by an intermediate vaccine strain (W2512-like strain). Pathogenicity experiments indicated that IBD16HeN01 could cause severe bursal lesions and the recombination increased viral pathogenicity to chick embryos compared with the novel variant IBDV. Homologous recombination in IBDV has increased the complexity of disease prevention and control and reminds us that we should use live vaccines more scientifically and cautiously.

Keywords: Homologous recombination; Infectious bursal disease virus; Intermediate vaccine; Novel variant strain.

Copyright © 2020 Elsevier B.V. All rights reserved.