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Identification of an infectious bronchitis coronavirus strain exhibiting a classical genotype but altered antigenicity, pathogenicity, and innate immunity profile

View Article: PubMed Central - PubMed

ABSTRACT

Avian coronavirus infectious bronchitis virus (IBV) poses economic threat to the poultry industry worldwide. Pathogenic IBV 3575/08 was isolated from broilers vaccinated with the attenuated viral vaccine derived from a Taiwan strain 2575/98. In this study, extensive investigations were conducted on the genome sequences, antigenicity, pathogenicity, and host immune responses of several IBV strains in specific-pathogen-free chickens. Sequence analyses revealed that 3575/08 and 2575/98 shared high homology in their structural genes, but not in non-structural accessory proteins such as 3a, 3b and 5b. Despite a high degree of homology in their spike protein genes, cross neutralization test showed low cross protection between 3575/08 and 2575/98, suggesting distinct antigenicity for the two strains. Animal challenge experiments exhibited strong respiratory and renal pathogenicity for 3575/08. In addition, early and prolonged viral shedding and rapid viral dissemination were observed. Immune gene expression profiling by PCR array showed chickens infected with 3575/08 had delayed expression of a subset of early innate immune genes, whereas chickens infected with the wild-type or attenuated-type 2575/08 revealed quick gene induction and efficient virus control. In summary, this study reveals a new IBV strain, which harbors a known local genotype but displays remarkably altered antigenicity, pathogenicity and host defenses.

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Pathological examination of trachea and kidney from IBV infected chickens.The pathological lesions of experimentally infected chickens were evaluated at 7 dpi, and representative pictures were shown. Panels D and H refer to control tissues. IBV 3575/08 infected chickens presented pathological lesions such as desquamation of ciliated cells, infiltration of heterophils, and lymphocytes and epithelial hyperplasia in the trachea (A, arrowed). The lesions in 2575 WT (B) and 2575 AT (C) groups were similar to the 3575/08 group but milder. For IBV 3575/08-infected chicken kidney, renal tubule dilation, necrotic tubular cells, and urate in the tubular cavity were observed (E, arrowed). Vesicular degeneration was found in renal tubular epithelial cells from the 2575 WT group (F, arrowed). For the 2575 AT group, the renal cells were normal as the control group (G).
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f3: Pathological examination of trachea and kidney from IBV infected chickens.The pathological lesions of experimentally infected chickens were evaluated at 7 dpi, and representative pictures were shown. Panels D and H refer to control tissues. IBV 3575/08 infected chickens presented pathological lesions such as desquamation of ciliated cells, infiltration of heterophils, and lymphocytes and epithelial hyperplasia in the trachea (A, arrowed). The lesions in 2575 WT (B) and 2575 AT (C) groups were similar to the 3575/08 group but milder. For IBV 3575/08-infected chicken kidney, renal tubule dilation, necrotic tubular cells, and urate in the tubular cavity were observed (E, arrowed). Vesicular degeneration was found in renal tubular epithelial cells from the 2575 WT group (F, arrowed). For the 2575 AT group, the renal cells were normal as the control group (G).

Mentions: The pathological lesions of experimentally infected chickens were further evaluated at 7 dpi, and representative pictures are shown in Fig. 3. In the trachea epithelium, normal goblet cells and ciliated cells were seen in the PBS control group (Fig. 3D). However, the IBV 3575/08 infected chickens presented pathological lesions such as desquamation of ciliated cells, infiltration of heterophils, and lymphocytes and epithelial hyperplasia in the trachea (Fig. 3A, arrowed). Lesions in the 2575 WT (Fig. 3B) and 2575 AT (Fig. 3C) groups were similar but less severe as compared to the 3575/08 group. Upon observing the kidneys, the control group showed normal renal tubular epithelial cell with homogeneous plasma and distinctive renal tubular cavities (Fig. 3H). In the kidneys of IBV 3575/08-infected chickens, however, renal tubule dilation, necrotic tubular cells, and urate in the tubular cavity were observed (Fig. 3E, arrowed). Vesicular degeneration was also observed in the renal tubular epithelial cells from the 2575 WT group (Fig. 3F, arrowed). On the other hand, the 2575 AT group showed normal kidney patterns similar to the control group (Fig. 3G). The pathological findings indicate that both IBV 3575/08 and 2575 WT are respiratory and nephropathogenic strains. IBV 3575/08 showed higher virulence as it inflicted more severe trachea and renal tissue damages in chickens than the 2575 WT strain. No virulence in the kidney was observed for IBV 2575 AT.


Identification of an infectious bronchitis coronavirus strain exhibiting a classical genotype but altered antigenicity, pathogenicity, and innate immunity profile
Pathological examination of trachea and kidney from IBV infected chickens.The pathological lesions of experimentally infected chickens were evaluated at 7 dpi, and representative pictures were shown. Panels D and H refer to control tissues. IBV 3575/08 infected chickens presented pathological lesions such as desquamation of ciliated cells, infiltration of heterophils, and lymphocytes and epithelial hyperplasia in the trachea (A, arrowed). The lesions in 2575 WT (B) and 2575 AT (C) groups were similar to the 3575/08 group but milder. For IBV 3575/08-infected chicken kidney, renal tubule dilation, necrotic tubular cells, and urate in the tubular cavity were observed (E, arrowed). Vesicular degeneration was found in renal tubular epithelial cells from the 2575 WT group (F, arrowed). For the 2575 AT group, the renal cells were normal as the control group (G).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120290&req=5

f3: Pathological examination of trachea and kidney from IBV infected chickens.The pathological lesions of experimentally infected chickens were evaluated at 7 dpi, and representative pictures were shown. Panels D and H refer to control tissues. IBV 3575/08 infected chickens presented pathological lesions such as desquamation of ciliated cells, infiltration of heterophils, and lymphocytes and epithelial hyperplasia in the trachea (A, arrowed). The lesions in 2575 WT (B) and 2575 AT (C) groups were similar to the 3575/08 group but milder. For IBV 3575/08-infected chicken kidney, renal tubule dilation, necrotic tubular cells, and urate in the tubular cavity were observed (E, arrowed). Vesicular degeneration was found in renal tubular epithelial cells from the 2575 WT group (F, arrowed). For the 2575 AT group, the renal cells were normal as the control group (G).
Mentions: The pathological lesions of experimentally infected chickens were further evaluated at 7 dpi, and representative pictures are shown in Fig. 3. In the trachea epithelium, normal goblet cells and ciliated cells were seen in the PBS control group (Fig. 3D). However, the IBV 3575/08 infected chickens presented pathological lesions such as desquamation of ciliated cells, infiltration of heterophils, and lymphocytes and epithelial hyperplasia in the trachea (Fig. 3A, arrowed). Lesions in the 2575 WT (Fig. 3B) and 2575 AT (Fig. 3C) groups were similar but less severe as compared to the 3575/08 group. Upon observing the kidneys, the control group showed normal renal tubular epithelial cell with homogeneous plasma and distinctive renal tubular cavities (Fig. 3H). In the kidneys of IBV 3575/08-infected chickens, however, renal tubule dilation, necrotic tubular cells, and urate in the tubular cavity were observed (Fig. 3E, arrowed). Vesicular degeneration was also observed in the renal tubular epithelial cells from the 2575 WT group (Fig. 3F, arrowed). On the other hand, the 2575 AT group showed normal kidney patterns similar to the control group (Fig. 3G). The pathological findings indicate that both IBV 3575/08 and 2575 WT are respiratory and nephropathogenic strains. IBV 3575/08 showed higher virulence as it inflicted more severe trachea and renal tissue damages in chickens than the 2575 WT strain. No virulence in the kidney was observed for IBV 2575 AT.

View Article: PubMed Central - PubMed

ABSTRACT

Avian coronavirus infectious bronchitis virus (IBV) poses economic threat to the poultry industry worldwide. Pathogenic IBV 3575/08 was isolated from broilers vaccinated with the attenuated viral vaccine derived from a Taiwan strain 2575/98. In this study, extensive investigations were conducted on the genome sequences, antigenicity, pathogenicity, and host immune responses of several IBV strains in specific-pathogen-free chickens. Sequence analyses revealed that 3575/08 and 2575/98 shared high homology in their structural genes, but not in non-structural accessory proteins such as 3a, 3b and 5b. Despite a high degree of homology in their spike protein genes, cross neutralization test showed low cross protection between 3575/08 and 2575/98, suggesting distinct antigenicity for the two strains. Animal challenge experiments exhibited strong respiratory and renal pathogenicity for 3575/08. In addition, early and prolonged viral shedding and rapid viral dissemination were observed. Immune gene expression profiling by PCR array showed chickens infected with 3575/08 had delayed expression of a subset of early innate immune genes, whereas chickens infected with the wild-type or attenuated-type 2575/08 revealed quick gene induction and efficient virus control. In summary, this study reveals a new IBV strain, which harbors a known local genotype but displays remarkably altered antigenicity, pathogenicity and host defenses.

No MeSH data available.


Related in: MedlinePlus