Emerging infectious bronchitis virus (IBV) in Egypt: Evidence for an evolutionary advantage of a new S1 variant with a unique gene 3ab constellation.
Infect Genet Evol
; 85: 104433, 2020 Nov.
Article
en En
| MEDLINE
| ID: mdl-32622080
ABSTRACT
Infectious bronchitis virus (IBV), a gamma-coronavirus, causes infectious bronchitis (IB), a major respiratory disease of chicken. Its high mutation rate in conjunction with recombination of the RNA genome constantly creates IBV variants that are difficult to control by currently available vaccines. In this study, we addressed the question whether small-scale holdings might harbor IBV variants that serve as a reservoir for newly emerging variants. Egyptian IBV isolate EGY/NR725/2016 (NR725/16) from a small-scale broiler farm was assigned to genotype I, clade 23 (S1GI-23), based on partial S1 gene sequences and corroborated by full genome sequencing. Analysis of the S1 gene established three subclades for historical IBV strains (S1GI-23.1, S1GI-23.2.1 and S1GI-23.2.2) and confirmed NR725/16 as being part of a separate fourth subclade (S1GI-23.3). Samples from the years 2018 and 2019 revealed that the new subclade prevails in Egypt, carrying fixed mutations within the hypervariable regions (HVR) 1-3 of the S1 protein that affect two neutralization sensitive epitopes at sites 294F, 297S and 306Y (48.2) and 329R (62.1). In addition, recombination was recognized in isolate NR 725/16, with intra-subtype mixing for the entire genes 3ab and E and inter-subtype mixing for the entire gene 6b with a close match to QX like viruses of genotype GI-19. Further analysis of gene 3ab detected the homologous gene pool to NR725/16 in samples from 2013 (3abC) and closely related 3ab genotypes in IBV Egyptian isolates from 2016, 2018 and 2019. These data prove a flourishing exchange between poultry holdings with a common gene pool. The continued circulation of viruses harboring genes S1GI-23.3 and 3abC indicates an evolutionary advantage of this combination possibly by combining antigenic escape with modulated pathogenicity to facilitate IBV spread in the vaccinated poultry population in Egypt.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Enfermedades de las Aves de Corral
/
Infecciones por Coronavirus
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Virus de la Bronquitis Infecciosa
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Glicoproteína de la Espiga del Coronavirus
/
Secuenciación Completa del Genoma
Límite:
Animals
País/Región como asunto:
Africa
Idioma:
En
Revista:
Infect Genet Evol
Asunto de la revista:
BIOLOGIA
/
DOENCAS TRANSMISSIVEIS
/
GENETICA
Año:
2020
Tipo del documento:
Article
País de afiliación:
Egipto