2014 Origin and characteristics of the recombinant novel avian infectious bronchitis coronavirus isolate ck_CH_LJL_11105

7 Pages·2014·1.09 MB·English

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Origin and characteristics of the recombinant novel avian infectious

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bronchitis coronavirus isolate ck/CH/LJL/111054

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Shengwang Liu ⇑
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, Qianqian Xu, Zongxi Han, Xiaoli Liu, Huixin Li, Hongbo Guo, Nana Sun, Yuhao Shao,

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Xiangang Kong

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Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences,
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Harbin 150001, People’s Republic of China

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a r t i c l e
i n f o

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Article history:
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Received 4 September 2013
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Received in revised form 12 February 2014
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Accepted 14 February 2014
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Available online xxxx

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Keywords:
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Avian infectious bronchitis virus
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Recombinant event
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Connecticut serotype
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Massachusetts serotype
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a b s t r a c t

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Recombination among infectious bronchitis viruses (IBVs), coupled with point mutations, insertions, and
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deletions that occur in the genome, is thought to contribute to the emergence of new IBV variants. In this
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study an IBV, ck/CH/LJL/111054, was isolated from a H120-vaccinated chicken, which presented with a
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suspected IBV infection. Phylogenetic analysis of the S1 subunit sequence confirmed that strain ck/CH/
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LJL/111054 is of the Connecticut-type; however, further extensive full-length genomic analysis identified
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the occurrence of recombination events. Therefore, strain ck/CH/LJL/111054 may have originated from
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recombination events between Conn- and Mass-like strains at three recombination breakpoints: two
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located within the nsp3 gene sequence and one in the nsp12 gene sequence. Further, the uptake of the
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50 untranslated regions, nsp2, parts of nsp3, nsp4–11, and parts of nsp 12 from Mass-like virus by ck/
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CH/LJL/111054 might have resulted in changes in viral replication efficiency rather than antigenic
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changes, via cross-neutralization analysis with the H120 strain. Recombination events coupled with
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the accumulation of mutations in the ck/CH/LJL/111054 genome may account for its increased virulence
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in specific-pathogen free chickens.
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� 2014 Elsevier B.V. All rights reserved.
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1. Introduction

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Avian infectious bronchitis virus (IBV), a gamma-coronavirus in

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the Coronaviridae family (Carstens, 2010), is an enveloped, posi-

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tive-sense, single-stranded, RNA virus with a genome size of approx

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imately 27 kb and causes a highly contagious upper-respiratory

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tract disease in domestic chickens, which is characterized by cough-

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ing, sneezing and tracheal rales. The 50 two-thirds of the IBV genome

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encodes two polyproteins (1a and 1ab) that contain proteins neces-

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sary for RNA replication, whereas the 30 one-third encodes several

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structural proteins: the surface spike glycoprotein (S), and small

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envelope (E), membrane (M), and nucleocapsid (N) proteins. It is

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generally believed that the S1 subunit of S glycoprotein contains

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hypervariable regions that play a role in attachment to host recep-

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tors, membrane fusion, and entry into the host cell. The S1 subunit

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of S glycoprotein carries conformationally dependent virus-neutral-

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izing and serotype-specific determinants, and is a determinant of

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cell tropism. Additional accessory protein genes are located in the

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30 region of the genome in an IBV species-specific position.

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Since first described in 1936, IBV had undergone a high rate of

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genetic change that has contributed to the appearance of diverse

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subpopulations of the virus that continually emerge to form new

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variants of existing strains as well as completely new types. The

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Massachusetts (Mass) and Connecticut (Conn) strains are two of

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the most well characterized and important IBV types and were first

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isolated in the 1930s and 1956, respectively, in the United States of

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America (Cavanagh and Gelb, 2008). In addition, Mass-type

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viruses, which cause heavy economic losses to the poultry indus-

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try, have also been detected up to the present time in several

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European and Asian countries, including China, although at differ-

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ent frequencies (Jackwood, 2012). In contrast, Conn-type viruses,

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which show only 95.4% of nucleotides homology in the S1 subunit

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sequence with Mass-type viruses and are in different serotypes

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from the Mass-type viruses, circulate mainly in the United States

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of America and Central America (Jackwood, 2012).

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Generally, point mutations, insertions, and deletions that occur

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in the S1 subunit of the spike protein in IBV strains contribute to

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the existence of many serotypes and the emergence of variants

http://dx.doi.org/10.1016/j.meegid.2014.02.015
1567-1348/� 2014 Elsevier B.V. All rights reserved.

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