Comparative Genomics of Korean Infectious Bronchitis Viruses (IBVs) and an Animal Model to Evaluate Pathogenicity of IBVs to the Reproductive Organs

Abstract

The K-I and nephropathogenic K-II genotypes of infectious bronchitis virus (IBV) have been isolated since 1995 and 1990, respectively, in Korea and commercial inactivated oil-emulsion vaccines containing KM91 (K-II type) and Massachusetts 41 strains have been used in the field. To date, genomic analyses of Korean IBV strains and animal models to test the pathogenicity of Korean IBVs to the reproductive organs have been rare. In the present study, comparative genomics of SNU8067 (K-I type) and KM91 IBVs was performed, and an animal model to test the pathogenicity of SNU8067 was established and applied to vaccine efficacy test. The genome sizes of SNU8067 (27,708 nt) and KM91 (27,626 nt) were slightly different and the nucleotide and amino acid identities of the S1 (79%, 77%), 3a (65%, 52%), and 3b (81%, 72%) genes were lower than those of other genes (94%–97%, 92%–98%). A recombination analysis revealed that SNU8067 was a recombinant virus with a KM91-like backbone except S1, 3a, and 3b genes which might be from an unknown virus. An SNU8067 infection inhibited formation of hierarchal ovarian follicles (80%) and oviduct maturation (50%) in the control group, whereas 70% of vaccinated chickens were protected from lesions.

Gonadal pathogenicity of an infectious bronchitis virus strain from the Massachusetts genotype

“…This finding suggests that ovarian follicles may be more susceptible than the oviduct and, in turn, drops in egg production may be a consequence of irregular ovarian follicle development. Furthermore, the same authors observed that 30% of vaccinated chickens exhibited moderate to marked aplasia of the ovarian follicles and moderate atrophy of oviducts, possibly from the use of inactivated oil-emulsion vaccines in SPF chickens without priming [30]. According to the latest molecular epidemiological surveys, 16.80 to 33.71% of the Brazilian poultry flocks positive for IBV were comprised of breeders.…”

“…Afterwards, several other researchers focused on the IBV induction of false layers or abnormal oviducts [20,21,24,25,27,28], but only a few studies investigated IBV effects on the gonads [29]. Recently, Hong et al [ 30] noticed that infections with a Korean IBV strain (SNU8067) in unvaccinated 16-week-old SPF hens inhibited formation of hierarchal ovarian follicles (80% of individuals) and oviduct maturation (50% of individuals). This finding suggests that ovarian follicles may be more susceptible than the oviduct and, in turn, drops in egg production may be a consequence of irregular ovarian follicle development.…”

Genetic and biological characteristics of four novel recombinant avian infectious bronchitis viruses isolated in China

“…Vaccination is considered to be the most reliable approach for IBV control; however, existing vaccines have proved to be inadequate due to the constant emergence of new virus variants (De Wit, 2000;de Wit et al, 2011). In addition, co-infection of a chicken by different IBV types carry the risk of recombination, accounting for the emergence of novel IBV strains with different antigenic properties, tissue tropism, and pathogenicity; such strains have been identified in many parts of the world (Franzo et al, 2015;Hewson et al, 2014;Hong et al, 2012;Kottier et al, 1995;Lee and Jackwood, 2000;Mardani et al, 2010;Naguib et al, 2016;Quinteros et al, 2016;Pohuang et al, 2011;Thor et al, 2011;Zanaty et al, 2016;Zhang et al, 2015), and this presents a major challenge to current IBV prevention and control strategies.…”

Comparative transcriptome analysis reveals induction of apoptosis in chicken kidney cells associated with the virulence of nephropathogenic infectious bronchitis virus

“…1A). Hong SM et al reported that 3a, 3b and 5b of IBV might inhibit innate immunity and play a role in host adaptation and evasion of host immune response [6]. However, it is possible that these sequences also take part in the process of induction of apoptosis directly in kidney cells during virulent IBV infection.…”

“…The virus replicates at many epithelial surfaces of the chicken. IBV initially infects the upper respiratory tract and then spreads to kidney and oviduct, causing respiratory disease, nephritis and egg drop according the strain of the virus and the system involved [5][6][7]. The IBV genome is variable and variants of different genotypes have been reported worldwide [8].…”