Analyses of turkey coronavirus (TCoV), an enteric disease virus that is highly similar to infectious bronchitis virus (IBV) an upper-respiratory tract disease virus in chickens, were conducted to determine the adaptive potential, and genetic changes associated with emergence of this group 3 coronavirus. Strains of TCoV that were pathogenic in poults and nonpathogenic in chickens did not adapt to cause disease in chickens. Comparative genomics revealed two recombination sites that replaced the spike gene in IBV with an unidentified sequence likely from another coronavirus, resulting in cross-species transmission and a pathogenicity shift. Following emergence in turkeys, TCoV diverged to different serotypes through the accumulation of mutations within spike. This is the first evidence that recombination can directly lead to the emergence of new coronaviruses and new coronaviral diseases, emphasizing the importance of limiting exposure to reservoirs of coronaviruses that can serve as a source of genetic material for emerging viruses.
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