Serotype, antigenicity, and pathogenicity of a naturally recombinant TW I genotype infectious bronchitis coronavirus in China

Abstract

Since 2009, strains of the naturally recombinant TW I genotype of infectious bronchitis virus (IBV) have caused considerable damage to the Chinese poultry industry. To better understand the antigenicity and pathogenesis of this genotype, the characteristics of the ck/CH/LDL/140520 strain were compared to those of four commercial IB vaccine strains that are used commonly in China, as well as four attenuated viruses that represent two types of IBV strains, which are believed to have originated in China and are the predominant IBV types circulating in chicken flocks in China and many other parts of the world. The results showed that all eight strains were genetically and serotypically different from the strain ck/CH/LDL/140520. Furthermore, neither the vaccine strains nor the attenuated viruses could provide complete respiratory protection of chickens against a challenge with the ck/CH/LDL/140520 strain, indicating that it is necessary to develop new live vaccines or to evaluate the use of established vaccines in combination to control naturally recombinant TW I-type IBV strains in the future. Our results showed that strain ck/CH/LDL/140520 is very pathogenic, and that it is able to cause cystic oviducts in a high percentage of birds, as well as mortality due to nephritis and respiratory distress with complete tracheal ciliostasis, especially in chickens infected at 1day of age.

Genome characterization, antigenicity and pathogenicity of a novel infectious bronchitis virus type isolated from south China

“…It is possible that isolate γCoV/ck/China/I0111/14 cannot induce cystic oviducts in layer hens, or alternatively, that the virus can induce cystic oviducts but the small numbers of the chickens experimentally infected in this study were responsible for the differences in virus tropism. However, cystic oviducts were observed in 2 out of the 3, and 4 out of 6 surviving SPF chickens challenged with ck/CH/LGX/111119 and ck/CH/LDL/140520 (Gao et al, 2016), respectively, at 1-day-old. This requires further investigation.…”

“…In addition, six IBV strains, including ck/CH/LDL/091022 , ck/CH/LGX/111119 , ck/CH/LDL/97I (Liu et al, 2007), ck/CH/LDL/140520 (Xu et al, 2016), 4/91 and H120 were used in this study. Strains ck/CH/LDL/091022, ck/CH/LGX/ 111119, ck/CH/LDL/97I and ck/CH/LDL/140520 represent the four major IBV serotypes circulating in chicken flocks in China.…”

“…IBV was recorded in China for the first time in the 1980s (Han et al, 2011). Surveillance studies have reported widespread IBV infections in China since the late 1990s with associated multiple types; LX4 (QX-like) is the predominant type circulating in chicken flocks and first emerged in 1995 and at least five other serotypes Gao et al, 2016;Han et al, 2011;Liu et al, 2007) and variants Liu et al, 2013Liu et al, , 2014Ma et al, 2012) have been circulating in China over recent years.…”

Identification and molecular characterization of a novel serotype infectious bronchitis virus (GI-28) in China

“…The median embryo infectious dose (EID 50 ) was calculated using the method of Reed and Muench (1938). The antisera used for this test included anti-4/91, anti-H120, anti-ck/CH/LDL/140520, anti-ck/ CH/LDL/97I, anti-ck/CH/LDL/091022 , and anti-ck/ CH/LGX/111119, which were prepared as described by Gao et al (2016).…”

“…Then, tissues of the tracheal, lungs, kidneys, and cecal tonsils were collected, fixed in 10% neutral buffered formalin, embedded in paraffin, sectioned at a thickness of 4 mm, and mounted on glass slides, which were stained with hematoxylin and eosin. Immunohistochemical (IHC) analysis was performed to detect the IBV antigen using monoclonal antibody 6D10 against the N protein as described by Han et al (2016) and Gao et al (2016). Blood samples were collected on day 4 from 10 birds and on days 8, 12, 16, 20, and 24 post-challenge from all birds to confirm the presence of antibodies against IBV using a commercial enzymelinked immunosorbent assay kit (IDEXX Laboratories, Inc., Westbrook, ME, USA) in accordance with the manufacturer's instructions.…”