Genetic and biological characteristics of four novel recombinant avian infectious bronchitis viruses isolated in China

Abstract

A B S T R A C TInfectious bronchitis viruses (IBVs) of GI-13 (793/B) and GI-19 (QX/LX4) lineages have been frequently detected in China in recent years. Naturally recombinant IBVs originating from the GI-13 and GI-19 lineages have also been isolated from chicken flocks with respiratory and renal problems in China. Thorough genetic and biological investigations of these recombinant viruses have led to speculation regarding their origin, evolution, and control. In order to confirm the previous results and further extend our understanding about the characteristics of the four recombinant IBV strains we had previously identified (I0718/17, I0722/17, I0724/17, and I0737/17), we conducted phylogenetic analysis by comparing their complete S1 gene sequences with those of 71 reference strains of different genotypes and lineages. We identified a close relationship between the S1 sequences of the four strains and those of GI-13 strains. The results of complete genome sequence analysis confirmed the previously identified recombination events in the four IBV strains and revealed additional recombination events in different genomic regions of strains I0718/17 and I0724/17, suggesting that the two strains originated from multiple recombination events between 4/91-like and YX10-like viruses. We comparatively evaluated the antigenicity, pathogenicity, and affinity of the four recombinant viruses and their deduced parental strains in the trachea and kidneys. Some of the strains showed comparable antigenic relatedness, pathogenicity, and affinity for the trachea and kidneys among each other and with their parental viruses; however, some of them showed varying biological characteristics. Point mutations observed in the receptor-binding domain and hypervariable region of the S1 subunit of the spike protein likely have an effect on these differences in biological characteristics, although the influence of other factors-such as host innate-immune responses and changes in genomic regions beyond the S1 protein-might also be responsible for such changes.

Genetic Analysis of Avian Coronavirus Infectious Bronchitis Virus in Yellow Chickens in Southern China over the Past Decade: Revealing the Changes of Genetic Diversity, Dominant Genotypes, and Selection Pressure

“…Surprisingly, majorities of the New-type 1 strains from other studies were isolated from south China [2,5,15,55]. Recently, another novel genotype VII (GVII-1) was reported [17]. Both these two New-type viruses were identified in our study and the total number of their strains showed New-type was the third most dominant genotype.…”

“…To increase our insight into the comprehensive epidemiological situation and evolutionary trend of IBV in southern China, 27 IBV isolates from 1985 to 2008 in southern China were also used to analyze together. The 43 representative reference strains included the live vaccine strains commonly used and the prevalent strains in China and other countries worldwide, which represented the main well-established lineages and genotypes in recent years in China [17]. Our results indicated that there was a remarkable change in genetic diversity, dominant genotypes, and selection pressure of IBV strains in southern China over the past decade compared with the previous period of 1985–2007.…”

“…A variety of IBV genotypes and variants are distributed globally. So far, a total of seven genotypes comprising 35 distinct viral lineages have been defined worldwide based on the complete S1 gene sequences [17]. IBV strains within a certain country or region are unique even though many countries share some common antigenic types.…”

Evolutionary Analysis of Infectious Bronchitis Virus Reveals Marked Genetic Diversity and Recombination Events

“…A potential issue attributed to the recombination is that changes occurring during recombination in the S1 subunit might alter the neutralizing epitopes and result in the appearance of novel IBV serotypes. In addition, recombination events between vaccine and field strains may lead to reversal of virulence and genesis of highly virulent strains [ 44 ]. Therefore, further studies are required to clearly determine the clinicopathobiological features of these viruses in a chicken model.…”

Infectious Bronchitis Virus Evolution, Diagnosis and Control

“…The strategy adopted by coronaviruses in gene expression regulation facilitates this phenomenon since it depends on discontinuous transcription, which relies entirely on the viral RdRp template-switching property [ 13 , 38 ]. IBV makes no exception: several studies reported recombination events which occurred in field conditions, involving both field and vaccine strains [ 39 , 40 , 41 ]. This evidence has risen some concerns on the potential risk of new recombinant strain emergence, especially when multiple vaccines are administered and/or vaccine strains circulate for a long time.…”