Inflammatory response of young rabbits to calicivirus infection

Abstract

Caliciviruses cause rabbit haemorrhagic disease (RHD) that kills more than 90% of the infected adult animals within 1 a 3 days of infection. The virus replicates in the liver and causes a fulminant hepatitis in adult rabbits leading to RHD. A mystery of the calicivirus infection is that young rabbits (less than 8-weeks old) are resistant to the infection, in spite of undergoing viral replication in the liver and of expressing transient hepatitis. Heterophils were the predominant inflammatory cells seen in hepatic tissue of infected adult rabbits, whereas mononuclear cells dominated the inflammatory infiltrates of the infected young rabbits (4-weeks-old). In order to define the role of inflammation in the pathogenesis of the calicivirus infection, we have studied the cellular inflammatory response in young rabbits experimentally infected by calicivirus. For this, we have used transmission electron microscopy (TEM) and flow cytometry to identify the inflammatory cells that infiltrate the hepatic tissue of young rabbits at 48 hours of calicivirus infection. In same infected rabbits, lymphoid organs (spleen and thymus) were used to quantify by flow cytometry the total number of leukocytes seen inside these organs.