PRELIMINARY CHARACTERIZATION OF THE STRUCTURAL PROTEINS OF THE CORONAVIRUSES, SIALODACRYOADENITIS VIRUS AND PARKERS RAT CORONAVIRUS

A procedure was developed for the partial purification of the rat coro naviruses, sialodacryoadenitis virus (SDAV) and Parker's rat coronavir us (PRC). The SDAV and PRC were replicated in L-2 cell monolayer cultu res, precipitated with ammonium sulphate, and further concentrated usi ng sucrose density gradient centrifugation. The major SDAV and PRC pro teins were identified by immunoblotting and compared with those of the JHM strain of mouse hepatitis virus (MHV-JHM). Monoclonal antibodies (MAb) against the M protein of JHM recognized proteins interpreted to be slightly smaller in immunoblots of SDAV and PRC (22.8 vs 23K for JH M). Similarly, a monoclonal antibody against the JHM N protein reacted with proteins of 53K in SDAV and PRC (vs 56K for JHM). Polyclonal ant isera to all three viruses also crossreacted with the M and N proteins . Some cross-reactivity amongst the S proteins was observed. Based on these data, the structural proteins of the rat coronaviruses, SDAV and PRC are closely related to those of MHV-JHM.