Characterization of a novel live attenuated infectious bronchitis virus vaccine candidate derived from a Korean nephropathogenic strain.
A nephropathogenic K2/01 strain of infectious bronchitis virus (IBV) was attenuated by 170 serial passages in embryonated chicken eggs for possible use as a future IBV vaccine strain. High-growth properties and narrow tissue tropisms (limited replication in respiratory tracts) were achieved by the adaptation process. Unlike the parent strain, the attenuated strain (K2p170) was safe in day-old specific-pathogen-free chicks since replication of the virus did not induce mortality and nephritis, and rarely induced histological changes in the trachea and kidney after intraocular administration. In day-old broilers, even though coarse spray administration of K2p170 induced clinical signs, ciliostasis, and histopathological lesions in the trachea and the kidney, they were all comparable to birds vaccinated with commercial H120 vaccine. Despite restriction of viral replication in the respiratory tract, K2p170 elicited the production of antiserum with a neutralization index of 4.5. K2p170 provided almost complete protection against both two distinct subgroups of Korean nephropathogenic strain (KM91-like and QX-like subgroup). Furthermore, K2p170 provided significantly greater cross-protection against two heterologous strains (Massachusetts and Korean respiratory strain) than those conferred by the commercial H120 vaccine. K2p170 also had no virulence reversion after five back passages in chickens. In conclusion, K2p170 exhibits a fine balance between attenuation and immunogenicity, possesses cross-protective efficacy, and merits further investigation as a potential live vaccine as an alternative means of protection against the recently emergent nephropathogenic IBV infection in many Eurasian countries.
Avian Disease Laboratory, College of Veterinary Medicine, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul 143-701, Republic of Korea.
Hyun Jeong
HJ
Lee
Ha Na
HN
Youn
Ji Sun
JS
Kwon
Youn Jeong
YJ
Lee
Jae Hong
JH
Kim
Joong Bok
JB
Lee
Seung Yong
SY
Park
In Soo
IS
Choi
Chang Seon
CS
Song
D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D002642:Chick Embryo; D002645:Chickens; D018352:Coronavirus Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D056738:Cross Protection; D004252:DNA Mutational Analysis; D001351:Infectious bronchitis virus / Q000276:immunology* / Q000302:isolation & purification; D007668:Kidney / Q000473:pathology; D008969:Molecular Sequence Data; D011201:Poultry Diseases / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D012367:RNA, Viral / Q000235:genetics; D056910:Republic of Korea; D017422:Sequence Analysis, DNA; D012692:Serial Passage; D014132:Trachea / Q000473:pathology; D014613:Vaccines, Attenuated / Q000009:adverse effects / Q000276:immunology; D014765:Viral Vaccines / Q000009:adverse effects / Q000276:immunology*; D014774:Virulence
D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D012367:RNA, Viral; D014613:Vaccines, Attenuated; D014765:Viral Vaccines