Retargeting of coronavirus by substitution of the spike glycoprotein ectodomain: Crossing the host cell species barrier

Coronaviruses generally have a narrow host range, infecting one or just a f ew species. Using targeted RNA recombination, we constructed a mutant of th e coronavirus mouse hepatitis virus (MHV) in which the ectodomain of the sp ike glycoprotein (S) was replaced with the highly divergent ectodomain of t he S protein of feline infectious peritonitis virus. The resulting chimeric virus, designated fMHV, acquired the ability to infect feline cells and si multaneously lost the ability to infect murine cells in tissue culture. Thi s reciprocal switch of species specificity strongly supports the notion tha t coronavirus host cell range is determined primarily at the level of inter actions between the S protein and the virus receptor. The isolation of fMHV allowed the localization of the region responsible for S protein incorpora tion into virions to the carboxy-terminal 64 of the 1,324 residues of this protein. This establishes a basis for further definition of elements involv ed in virion assembly. In addition, fMHV is potentially the ideal recipient virus for carrying out reverse genetics of MHV by targeted RNA recombinati on, since it presents the possibility of selecting recombinants, no matter how defective, that have regained the ability to replicate in murine cells.