Antigenic structure of the capsid protein of rabbit haemorrhagic disease virus

Rabbit haemorrhagic disease virus (RHDV) causes an important disease in rabbits. The virus capsid is composed of a single 60 kDa protein. The capsid protein gene was cloned in Escherichia coli using the pET3 system, and the antigenic structure of RHDV VP60 was dissected using 11 monoclonal antibodies (MAbs) and 12 overlapping fragments of the protein expressed in E. coli. Two antigenic regions were found. Ten out of the 11 MAbs recognized different discontinuous epitopes in the most immunodominant region of the viral capsid. This domain was located between residues 31 and 250 of the VP60 N terminus. The other MAb revealed the presence of an antigenic site within 102 aa of the C terminus. This MAb did not recognize the major cleavage product of the full-length 60 kDa protein. These results indicate that, in contrast to other caliciviruses such as Norwalk virus (NV), the 36 kDa cleavage product probably forms the N-terminal region of VP60. However, as in NV, the cleavage region appears to be the most immunodominant region.