Susceptibility of rodent cell lines to rat coronaviruses and differential enhancement by trypsin or DEAE-dextran

Cell lines of rodent origin were tested for susceptibility to infection with rat coronavirus (RCV), including sialodacryoadenitis virus (SDAV) and Parker's rat coronavirus (PRCV). LBC rat mammary adenocarcinoma cells were susceptible only if the cells were treated with diethylaminoethyl-dextran (DEAE-D). A recent report that RCVs grow well in L2 mouse fibroblast cells was confirmed and expanded. RCV infection of L2 cells was substantially enhanced by treatment of cells with trypsin but not by treatment with DEAE-D. Primary isolation of SDAV from experimentally infected rats was accomplished using trypsin-treated L2 cells. One of 13 additional cell lines tested (rat urinary bladder epithelium, RBL-02) supported growth of RCVs, and growth was slightly enhanced by DEAE-D, but not by trypsin. These refinements of in vitro growth conditions for RCVs should facilitate further studies of their basic biology and improve options for primary isolation.