Sequence analysis, pathogenicity determination and cytokine transcription profiles of a turkey coronavirus from North Carolina isolated in 2009

Wan-Jung Chen, Purdue University

Abstract

The present study was carried out to analyze the 3'-end genomic sequences of turkey coronavirus (TCoV) isolated from a turkey flock with acute enteritis in North Carolina (NC) in 2009 (NC20) and also to determine the pathogenicity and immune related cytokine transcription profiles of turkeys during infection with NC20. The 3'-end genomic sequences of NC20 were amplified by polymerase chain reaction (PCR), cloned, sequenced, and compared to those of TCoV isolate NC1440 from NC isolated in 1999 and TCoV isolate ATCC from Minnesota (MN) isolated in 1976. One-week-old turkeys were orally challenged with 10 5 egg-infective dose (EID)50/mL/turkey of NC20 and necropsied at 3, 7, and 21 days post infection (dpi) for evaluation of clinical signs, pathologic changes, and inflammatory and immune related cytokine mRNA expression levels. The nucleotide sequence homology of the 3'-end genomic sequences was 92.8% to 94.4% among NC20, NC1440 and ATCC. The nucleotide sequences of transcription-regulating sequence (TRS) were highly conserved among the three TCoV isolates. Diarrhea and significantly decreased body weight gains (P<0.05) were seen in turkey poults infected with NC20 at 3 and 7 dpi. The jejunum and ileum from NC20-infected turkey poults had shortened, blunted, and/or fused villi at 3 and 7 dpi. Ileum had the highest TCoV viral RNA load at 3 dpi, then decreased. mRNA expression levels of lipopolysaccharide induced tumor necrosis factor-α (LiTAF), interleukin (IL)-1β, IL-8 from the ileum and IL-6 from the cecal tonsil were significantly up-regulated ( P<0.05) in TCoV-infected turkeys at 3 dpi. mRNA expression levels of interferon (IFN)-γ and IL-10 from the ileum were up-regulated at 3, 7, and 21 dpi, respectively. The results indicated that NC20 from NC isolated in 2009 shares more than 90% of genomic sequence homology with NC1440 and ATCC. In addition, NC20 causes atrophic enteritis, decreases body weight gains, and up-regulates pro-inflammatory, inflammatory, anti-inflammatory and T helper 1 (Th1) related cytokines in infected turkeys.

Degree

M.S.

Advisors

Lin, Purdue University.

Subject Area

Pathology|Virology|Veterinary services|Immunology

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