Inclusion of an Arg-Gly-Asp receptor-recognition motif into the capsid protein of rabbit hemorrhagic disease virus enables culture of the virus in vitro

The fact that rabbit hemorrhagic disease virus (RHDV), an important member of the Caliciviridae family, cannot be propagated in vitro has greatly impeded the progress of investigations into the mechanisms of pathogenesis, translation, and replication of this and related viruses. In this study, we have successfully bypassed this obstacle by constructing a mutant RHDV (mRHDV) by using a reverse genetics technique. By changing two amino acids (S305R,N307D), we produced a specific receptor-recognition motif (Arg-Gly-Asp; called RGD) on the surface of the RHDV capsid protein. mRHDV was recognized by the intrinsic membrane receptor (integrin) of the RK-13 cells, which then gained entry and proliferated as well as imparted apparent cytopathic effects. After 20 passages, the titers of RHDV reached 1 x 10(4.3) 50% tissue culture infectious dose (TCID50)/ml at 72 h. Furthermore, mRHDV-infected rabbits showed typical rabbit plague symptoms and died within 48-72 h. After immunization with inactivated mRHDV, the rabbits survived wild-type RHDV infection, indicating that mRHDV could be a candidate virus strain for producing a vaccine against RHDV infection. In summary, this study offers a novel strategy for overcoming the challenges of proliferating RHDV in vitro. Because virus uptake via specific membrane receptors, several of which specifically bind to the RGD peptide motif, is a common feature of host cells, we believe that this the strategy could also be applied to other RNA viruses that currently lack suitable cell lines for propagation such as hepatitis E virus and norovirus.