Comparison of 3'-end encoding regions of turkey coronavirus isolates from Indiana, North Carolina, and Minnesota with chicken infectious bronchitis coronavirus strains

Abstract

Objective: To analyze the 3'-end structural protein-encoding region of turkey coronavirus (TCoV) isolates associated with outbreaks of acute enteritis in Indiana, North Carolina, or Minnesota.

Methods: Four isolates of TCoV were sequenced over the entire 3'-end structural protein-encoding region and compared phylogenetically along with the corresponding sequences of infectious bronchitis virus (IBV) strains.

Results: The sequence similarity between TCoV and IBV was lower than that among TCoV isolates or that among IBV strains. The variation of sequences between TCoV and IBV was mainly contributed by the S protein gene. The sequence similarity of S gene between TCoV and IBV was lower than that among TCoV isolates or that among IBV strains. The phylogenetic tree based on the S protein region was similar to that based on the entire 3'-end structural protein-encoding region with TCoV isolates and IBV strains grouped in two separate clusters. The phylogenetic tree based on other genes had a very different topology with TCoV isolates randomly forming groups with different IBV strains.

Conclusions: These results suggested that TCoV probably shared the same origin with that of IBV and acquired sequences of S gene for turkey intestine tropism during the process of evolution in a separate environment.

Fig. 1

Phylogenetic analyses within the entire 3′-end structural protein-encoding region (a) and the deduced amino acid sequence of spike (S) protein gene (b), membrane (M) protein gene (c), nucleocapsid (N) protein gene (d), ORF 3a (e), 3b (f), 3c (g), 5a (h), and 5b (i) demonstrating relationships among TCoV isolates and IBV strains. The similarity scores were calculated by the Lasergene program using the unweighted pair group method with arithmetic averages. The horizontal distances are proportional to the number of nucleotide differences. The GenBank accession numbers for each coronavirus were described in the Materials and Methods.