A MURINE AND A PORCINE CORONAVIRUS ARE RELEASED FROM OPPOSITE SURFACES OF THE SAME EPITHELIAL-CELLS

Epithelial cells are important target cells for coronavirus infection. Earlier we have shown that transmissible gastroenteritis coronavirus (TGEV) and mouse hepatitis coronavirus (MHV) are released from differe nt sides of porcine and murine epithelial cells, respectively. To stud y the release of these viruses from the same cells, we constructed a p orcine LLC-PK1 cell line stably expressing the recombinant MHV recepto r cDNA (LMR cells). The MHV and TGEV receptor glycoproteins were shown by immunofluorescence to appear at the surface of the cells and to be functional so that the cells were susceptible to both Mi-iv and TGEV infection. Both coronaviruses entered polarized LMR cells only through the apical surface. Remarkably, while the cells remained susceptible to TGEV for long periods, infectability by MHV decreased with time aft er plating of the cells onto filters. This was not due to a lack of ex pression of the MHV receptor, since this glycoprotein was still abunda nt on the apical surface of these cells. TGEV and MHV appeared to exit LMR cells from opposite sides. Whereas TGEV was released preferential ly at the apical membrane, MHV was released preferentially at the baso lateral surface. These results show that vesicles containing the two c oronaviruses are targeted differently in LMR cells. We propose that th e viruses are sorted at the Golgi complex into different transport ves icles that carry information directing them to one of the two surface domains. The apical release of TGEV and the basolateral release of MHV might be factors contributing to the difference in virus spread found between TGEV and MHV in their respective natural hosts, the former ca using mainly a localized enteric infection, the latter spreading throu gh the body to other organs. (C) 1996 Academic Press, Inc.