Molecular cloning and expression of a spike protein of neurovirulent murine coronavirus JHMV variant cl-2

A cDNA encoding the spike (S) protein of the neurovirulent murine coronavirus JHMV variant cl-2 was isolated and sequenced. Analysis of the cDNA revealed that the S protein consists of 1376 amino acids, as does the S protein of mouse hepatitis virus 4. We inserted the cDNA into the genome of vaccinia virus to obtain a recombinant vaccinia virus (rVV). The S protein expressed in RK13 cells infected by the rVV was shown to be electrophoretically and immunologically indistinguishable from the S protein produced in DBT cells infected with cl-2 virus. RVV infection of rats and mice induced S protein-specific antibody production detectable by immunofluorescence and neutralization. Moreover, the S protein expressed by the rVV induced syncytium formation not only in mouse DBT and L cells, which are susceptible to cl-2 virus infection, but also in rabbit RK13 cells, which are not susceptible to cl-2 virus infection. This result suggests the possibility that RK13 cells have binding sites for the cl-2 virus S protein.