QX-like Infectious Bronchitis Research Articles

Efficacy of a plant-produced infectious bronchitis virus-like particle vaccine in specific pathogen-free chickens

Infectious bronchitis (IB) Gammacoronavirus causes a highly contagious respiratory disease in chickens that is listed by the World Organisation for Animal Health (WOAH). Its high mutation ability has resulted in numerous variants against which the commercially available live or recombinant vaccines singly offer limited protection. Agrobacterium-mediated transient expression in Nicotiana benthamiana (tobacco) plants was used here to produce a virus-like particle (VLP) vaccine expressing a modified full-length IBV spike (S) protein of a QX-like IB variant. In a challenge study with the homologous live IB QX-like virus, VLP-vaccinated birds produced S protein-specific antibodies comparable to those produced by live-vaccinated birds seroconverting with mean geometric titers of 6.8 and 7.2 log2, respectively. The VLP-vaccinated birds had reduced oropharyngeal and cloacal viral shedding compared to an unvaccinated challenged control and were more protected against tracheal ciliostasis than the live-vaccinated birds. While the results appeared similar, plant-produced IB VLPs are safer, more affordable, easier to produce and update to antigenically match any emerging IB variant, making them a more suitable alternative to IBV control than live-attenuated vaccines.

Optimization of infectious bronchitis virus-like particle expression in Nicotiana benthamiana as potential poultry vaccines.

Infectious bronchitis (IB) is a highly contagious, acute respiratory disease in chickens, with a severe economic impact on poultry production globally. The rapid emergence of regional variants of this Gammacoronavirus warrants new vaccine approaches that are more humane and rapid to produce than the current embryonated chicken egg-based method used for IB variant vaccine propagation (chemically-inactivated whole viruses). The production of virus-like particles (VLPs) expressing the Spike (S) glycoprotein, the major antigen which induces neutralizing antibodies, has not been achieved in planta up until now. In this study, using the Agrobacterium-mediated Nicotiana benthamiana (tobacco plant) transient expression system, the highest levels of VLPs displaying a modified S protein of a QX-like IB variant were obtained when the native transmembrane (TM) domain and cytoplasmic tail were substituted with that of the Newcastle disease virus (NDV) fusion glycoprotein, co-infiltrated with the NDV Matrix protein. In comparison, the native IB modified S co-infiltrated with IB virus membrane, envelope and nucleocapsid proteins, or substituted with the TM and CT of an H6-subtype influenza A virus hemagglutinin glycoprotein yielded lower VLP expression levels. Strong immunogenicity was confirmed in specific pathogen free chickens immunized intramuscularly with VLPs adjuvanted with Emulsigen®-P, where birds that received doses of 5 μg or 20 μg (S protein content) seroconverted after two weeks with mean hemaggluttination inhibition titres of 9.1 and 10 log2, respectively. Plant-produced IB VLP variant vaccines are safer, more rapid and cost effective to produce than VLPs produced in insect cell expression systems or the traditional egg-produced inactivated whole virus oil emulsion vaccines currently in use, with great potential for improved IB disease control in future.

Protection of chickens vaccinated with combinations of commercial live infectious bronchitis vaccines containing Massachusetts, Dutch and QX-like serotypes against challenge with virulent infectious bronchitis viruses 793B and IS/1494/06 Israel variant 2

ABSTRACTInfectious bronchitis virus (IBV) is a coronavirus which affects chickens of all ages. IBV mainly causes respiratory disease but can also result in reduced weight gain, reduced egg production, increased frequency of abnormal eggs and increased rates of mortality. Vaccination is the most important way to control the disease. Nevertheless, novel strains of infectious bronchitis (IB) continue to emerge in the field. In order to respond promptly, combinations of existing IB vaccines are frequently tested to see whether they can provide cross-protection. The efficacy of a combination of vaccines based on Massachusetts, Dutch and QX-like IB strains against emerging IB Israel variant 2 and IB 793B strains was assessed by means of four challenge studies. At least 80% of the birds vaccinated with IB H120 (Mass type) combined with IB D274 (Dutch type) followed by a QX-like IB vaccine booster or vaccinated with a combination of IB H120, IB D274 and QX-like IB were protected against a challenge with IB 793B. In addition, IB 1263 (Mass type) boosted by QX-like IB showed an 85% protection following challenge with IB 793B. A combination of IB H120 and IB D274 boosted by QX-like IB vaccine conferred 70% protection whilst H120 and IB D274 combination on its own showed 61.1% protection against Israel variant 2 challenge. IB 1263 boosted by a QX-like IB vaccine showed 50% protection against IB Israel variant 2. Therefore, it can be concluded that a combination of the IB H120, IB D274 and QX-like IB confers broad protection against different non-related virulent IB strains.