Genetic and biological characterization of alphacoronavirus feline infectious peritonitis virus and gammacoronavirus infectious bronchitis virus

Abstract

The rapid evolution of RNA viruses makes it difficult to control newly emerging infections. The genomes of RNA viruses evolve by mutations, recombination events, and natural selection. Coronaviruses (CoV) are +ssRNA viruses that are found worldwide, they are highly infectious, and are extremely difficult to control because they have a short generation time and a high mutation rate. They can cause respiratory, enteric, and in certain cases hepatic and neurological diseases, in a wide variety of animals and humans. In the following studies, we found that gamacoronaviruses may have proofreading capabilities similar to other CoVs, which is important for understanding how CoVs can replicate below their error threshold while still maintaining a large genome. In addition, we found that feline coronavirus was surprisingly stable following passage in cell culture, but different selection pressures in vivo may play a role in the pathobiology of that virus. Finally, we found that 10 transmissions of a gammacoronavirus in the natural host resulted in a decreased time to infection but a shorter infectious period. No changes were observed in the S1 gene indicating that mutations may have occurred elsewhere in the viral genome and that age and the maturity of the immune system in the host should be taken into consideration when calculating values for the reproduction ratio R0. These data will aid in our understanding of the mechanisms behind cross-species transmission, emergence of new CoVs, and viral evolution resulting in drug resistance and vaccine failures.