Evaluation of the virulence of RHDV (Rabbit Hemorragic Disease Virus) and mechanisms of host resistance

RHDV is thought to have originated from a pre-existing non-pathogenic rabbit calicivirus that has mutated and became pathogenic to rabbits. Antibodies specific to RHDV have been detected in sera collected before 1984 and in rabbits where RHD was never recorded provided the first indications of the pre-existence of non-pathogenic strains. Nowadays, several non-pathogenic strains have been isolated, but the switch to pathogenic forms has not yet been uncovered. In addition, MRCV, a new variant of the non-pathogenic group that was recently characterized, presented an intermediate virulence and several characteristics that may have been crucial for the acquisition of virulence. Regarding the mechanisms of resistance of the host, they include genetically determined absence or weak expression of attachment factors and humoral immunity. Nevertheless, studies have not yet been conclusive. This project aims at determining: i) how RHDV acquired virulence, ii) what are the determinants for the different grades of virulence, iii) which mechanisms of resistance the host developed to respond to the evolution of virulence and iv) what is the role of other species in the RHDV epidemiology.