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Identification of intertypic recombinant infectious bronchitis viruses from slaughtered chickens.

ABSTRACT: Avian coronavirus infectious bronchitis virus (IBV) poses a major threat to the global poultry industry. New IBV geno- and serotypes are continually reported. However, information on IBV prevalence is not frequently addressed in these reports. This study reports on a viral surveillance program in Taiwan from 2005 to 2006 with sampling conducted in poultry slaughterhouses. The genetic features of the obtained field isolates were investigated using sequence analysis and SimPlot analysis. A 1-directional neutralization test was performed to examine the antigenic variations among the collected viruses. The selection pressures that may contribute to the evolution of Taiwan IBV during recent decades were assessed. The surveillance program revealed that 8 out of 47 flocks (17%) were IBV-infected, from which 13 IBV isolates were recovered. Based on the phylogenetic analysis of the S1 gene, 11 of 13 isolates (84.6%) clustered with Taiwan group I. One IBV isolate showed evidence of frequent recombination events with China-like IBV in the spike glycoprotein (S) gene. Another isolate demonstrated the incorporation of China-like and H120-like genome fragments within the S2 gene and the membrane protein (M) gene region, respectively. Some antigenic changes were found in the 1-directional neutralization test. However, no positive selection pressures were related to those variations in the S1 genes among Taiwan IBV. Based on our work, we suggest that sampling chickens in poultry slaughterhouses is an effective and valuable means of compiling viral prevalence data, particularly in situations where there is subclinical infection. Infectious bronchitis viruses from slaughtered chickens revealed intertypic genetic recombination and antigenic diversity.

SUBMITTER: Chen HW

PROVIDER: S-EPMC7107050 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Gammacoronavirus infectious bronchitis virus (IBV) causes an economically important respiratory disease of poultry. Protective immunity is associated with the major structural protein, spike (S) glycoprotein, which induces neutralising antibodies and defines the serotype. Cross-protective immunity between serotypes is limited and can be difficult to predict. In this study, the ability of two recombinant IBV vaccine candidates, BeauR-M41(S) and BeauR-4/91(S), to induce cross-protection against a third serotype, QX, was assessed. Both rIBVs are genetically based on the Beaudette genome with only the S gene derived from either M41 or 4/91, two unrelated serotypes. The use of these rIBVs allowed for the assessment of the potential of M41 and 4/91 S glycoproteins to induce cross-protective immunity against a heterologous QX challenge. The impact of the order of vaccination was also assessed. Homologous primary and secondary vaccination with BeauR-M41(S) or BeauR-4/91(S) resulted in a significant reduction of infectious QX load in the trachea at four days post-challenge, whereas heterologous primary and secondary vaccination with BeauR-M41(S) and BeauR-4/91(S) reduced viral RNA load in the conjunctiva-associated lymphoid tissue (CALT). Both homologous and heterologous vaccination regimes reduced clinical signs and birds recovered more rapidly as compared with an unvaccinated/challenge control group. Despite both rIBV BeauR-M41(S) and BeauR-4/91(S) displaying limited replication in vivo, serum titres in these vaccinated groups were higher as compared with the unvaccinated/challenge control group. This suggests that vaccination with rIBV primed the birds for a boosted humoral response to heterologous QX challenge. Collectively, vaccination with the rIBV elicited limited protection against challenge, with failure to protect against tracheal ciliostasis, clinical manifestations, and viral replication. The use of a less attenuated recombinant vector that replicates throughout the respiratory tract could be required to elicit a stronger and prolonged protective immune response.

Project description:Infectious 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.

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Identification of intertypic recombinant infectious bronchitis viruses from slaughtered chickens.

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