A pathogenic and recombinant infectious bronchitis virus variant (CK/CH/GX/202109) with multiorgan tropism

Abstract

Despite vaccine use, novel strains and variants of infectious bronchitis virus (IBV) have emerged continuously, leading to economic losses to the poultry industry worldwide. This study aimed to characterize the IBV isolate CK/CH/GX/202109 from three yellow broilers in Guangxi, China. Recombination was shown to have occurred in regions of the 1ab gene. Compared to the whole genome of ck/CH/LGX/130530, which is genotypically related to tl/CH/LDT3-03, the 202109 strain had 21 mutations. The pathological assessment showed that this variant caused 30% and 40% mortality in 1-day-old chicks infected with oral and ocular inoculum, respectively. Nephritis, enlarged proventriculus, inflammation of the gizzard, and atrophy of the bursa of Fabricius were also observed at both 7 and 14 days post-infection (dpi). Viral loads in the trachea, proventriculus, gizzard, kidney, bursa, and cloacal swabs were higher at 7 dpi than at 14 dpi. Clinicopathological and immunohistochemical analyses revealed that this virus exhibited multiple organ tropisms capable of infecting the trachea, proventriculus, gizzard, kidney, bursa, ileum, jejunum, and rectum. Almost none of the 1-day-old infected chicks seroconverted until 14 dpi. While the virus was found in the ileum, jejunum, and rectum in the 28-day-old ocular group, the majority of 28-day-old infected chickens seroconverted at 10 dpi. These study findings demonstrate that recombination events and mutations during the evolution of IBV may greatly alter tissue tropism and emphasize the need for the continued surveillance of novel strains and variants in order to control this infection.

Genes, inflammatory response, tolerance, and resistance to virus infections in migratory birds, bats, and rodents

“…Indeed, panvirome profiling of livers, spleens, kidneys, and recta revealed coinfection of chicken infectious anemia virus, avian leukemia, avian encephalomyelitis virus (AEV) and multiple fowl adenoviruses, with a higher abundance of the last two virus species in the liver ( 101 ). Many other virus infections with novel strains and variants caused economic losses to the poultry industry worldwide and these included infectious bronchitis virus ( 102 ), bursal disease virus ( 103 ), H5Nx avian influenza viruses in Europe, Africa and the Americas ( 104 – 106 ), H5N8 and H5N1 avian influenza viruses ( 107 – 111 ). Similarly, the host response to pigeon paramyxovirus type I (PPMV-1) infection (associated with New Castle disease, a great threat to the pigeon industry), induces strong innate immune responses and intense inflammatory responses at an early stage and this is associated with viral pathogenesis ( 112 ).…”

Avian infectious bronchitis virus (AIBV) review by continent

“…Moreover, the interaction between the S1 and S2 spike subunits of the virus may control the host range and attachment site of IBV. The host immune response and infection route are additional variables that may contribute to tissue tropism ( Wang and Hou, 2023 ).…”