Research Article Feline Coronavirus 3c Protein: A Candidate for a Virulence Marker? A. S. Hora,1,2 P. O. Tonietti,3 S. A. Taniwaki,2 K. M. Asano,1,2 P. Maiorka,3 L. J. Richtzenhain,1,2 and P. E. Brandão1,2 1Department of Preventive Veterinary Medicine and Animal Health, School of Veterinary Medicine, University of S˜ao Paulo, Avenida Professor Dr. Orlando Marques de Paiva 87, Cidade Universit´aria, 05508-270 S˜ao Paulo, SP, Brazil 2Coronavirus Research Group, School of Veterinary Medicine, University of S˜ao Paulo, Avenida Professor Dr. Orlando Marques de Paiva 87, Cidade Universit´aria, 05508-270 S˜ao Paulo, SP, Brazil 3Department of Pathology, School of Veterinary Medicine, University of S˜ao Paulo, Avenida Professor Dr. Orlando Marques de Paiva 87, Cidade Universit´aria, 05508-270 S˜ao Paulo, SP, Brazil Correspondence should be addressed to A. S. Hora;