Mouse Hepatitis Virus Receptor as a Determinant of the Mouse Susceptibility to MHV Infection

Taguchi, Fumihiro; Hirai-Yuki, Asuka

There are at least four different types of CEACAM1 isoforms derived by alternative splicing (Beauchemin et al., 1999) . CEA-CAM1 belongs to an immunoglobulin (Ig) superfamily and is composed of an ectodomain, transmembrane domain (TM), and cytoplasmic tail (Cy). The ectodomain consists of four Ig constant region-like domains, i.e., the N, A1, B, and A2 domains from the N terminus of the molecule (Dveksler et al., 1991; Beauchemin et al., 1999) . Alternative splicing generates the molecules with two ectodomains, composed of N and A2, while those four-and twodomain forms have either long or short Cy, which results in the four different forms of CEACAM1 (Beauchemin et al., 1999) . Also as described above, there are two allelic forms in CEACAM1, 1a, and 1b, and, thus, at least eight totally different MHV receptor molecules exist (Beauchemin et al., 1999) . Recently, some CEA-CAM1 molecules deleting TM and Cy were found in intestinal epithelium and intestinal secretions, and those neutralize MHV (Terahara et al., 2009) .