Cross-Protective Immune Responses Elicited by a Korean Variant of Infectious Bronchitis Virus

Abstract

Infectious bronchitis virus (IBV) infections cause great economic losses to the poultry industry worldwide. IBVs continuously evolve by developing mutations in antigenic sites; therefore, an IBV vaccine that provides broad cross-protection can be a highly relevant and practical method in IBV control strategies. Although some IBV vaccine strains are known to provide protection against multiple IBV serotypes, in general commercially available IBV vaccine strains provide protection against antigenically related viruses but not distinct heterologous viruses. In the present study we characterized the Korean variant IBV K40/09 strain with regard to its immunogenicity and protective efficacy against seven currently circulating IBV serotypes. Three-week-old specific-pathogen-free chickens were intraocularly immunized with the IBV K40/09 strain at 10(3.5) 50% egg infective dose (EID50). Three weeks after immunization all the birds were challenged with seven different strains at 10(4.5) EID50. Chickens immunized with the IBV K40/09 strain showed significantly high levels of protection against all challenge viruses at the trachea and kidney levels. Our results suggest that IBV K40/09 could be useful to ensure IBV vaccine effectiveness owing to its cross-protective ability. Therefore, the IBV K40/09 strain merits consideration as a vaccine candidate to prevent infection as well as the spread of new IBV strains and many IBV variants that have been reported worldwide.

Comparison between dot-immunoblotting assay and clinical sign determination method for quantifying avian infectious bronchitis virus vaccine by titration in embryonated eggs

“…To prevent the economic losses caused by IBV, live attenuated vaccines and inactivated oil-emulsion vaccines containing both the KM91 and Massachusetts 41 (M41) strains are widely used in Korea. More recently, vaccine strains providing broad cross-protection have been developed, including the K2 and K40/09 strains (Kim et al, 2013;Lim et al, 2012Lim et al, , 2015. In Korea, the viral content of a vaccine preparation is quantified by IBV titration according to standard procedure approved by the Animal and Plant Quarantine Agency.…”

“…A respiratory strain belonging to the Mass group (M41), a nephropathogenic strain belonging to the KM91-like subgroup (KM91), and a recombinant nephropathogenic strain belonging to Korean new cluster 1 (K40/09) were used to evaluate the titer of IBVs used in killed vaccines as described by Kim et al (2013). Two nephropathogenic strains that were attenuated by 170 serial passages (K2p170) or heat-adapted passages (K40/09HP40) in chicken embryos were used to evaluate the live-attenuated vaccine strains (Lee et al, 2010).…”

Successful cross-protective efficacy induced by heat-adapted live attenuated nephropathogenic infectious bronchitis virus derived from a natural recombinant strain

“…The IBV strain K40/09, which was used for vaccine development, was isolated from a broiler farm in Korea. This variant strain belonged to the Korean new cluster 1, which originated from natural recombination between KM91 and QXIBV and showed a high level of cross-immunogenicity in a previous study [11]. Two challenge strains belonging to the KM91-like subgroup (KM91) and QX-like subgroup (K1277/03) were used to evaluate the crossprotective ability in chickens immunized with the heat-adapted IBV K40/09 strain ( Table 1).…”

“…This new cluster, represented by the K40/09 strain, is a natural recombinant strain between the Korean nephropathogenic strain KM91 and the QXIBV strain. In a previous challenge study, we characterized the Korean variant IBV K40/09 strain with regard to its immunogenicity and crossprotective efficacy against heterotype strains and its potential as a vaccine candidate [11]. http://dx.doi.org/10.1016/j.vaccine.2015.07.043 0264-410X/© 2015 Elsevier Ltd. All rights reserved.…”

Correlations in the results of virus neutralization test, hemagglutination inhibition test, and enzyme-linked immunosorbent assay to determine infectious bronchitis virus vaccine potency

“…Briefly, each of the ten-fold dilutions of IBV was mixed with test sera of an equal volume, and the virus/ serum mixture was incubated at 37 o C for 1 h. After incubation, 200 µL of the mixture was inoculated into 5 SPF ECEs via the allantoic cavity, and the eggs were then incubated for 7 days at 37 o C. IBV alone was titrated in parallel as a virus control. Embryos were examined for clinical signs such as dwarfing and death on the final day, and virus titers (EID 50 ) were calculated using the Reed and Muench method [12]. The virus neutralization index (VI) test was expressed by log10 difference in the titers of virus between virus/test serum mixture and virus/SPF serum mixture.…”