Receptor-independent infection of mouse hepatitis virus: analysis by spinoculation.

摘要

1. INTRODUCTION Cell entry of mouse hepatitis virus (MHV) is mediated by the interaction of its spike (S) protein and cellular receptor carcinoembryonic antigen adhesion molecule 1 (CEACAM1, MHVR). However, a highly neurotropic MHV, wild-type (wt) JHMV is known to spread to receptor-negative BHK cells from firstly infected receptor-positive DBT cells (MHVR-independent infection).Although the mechanism of this infection is still unclear, it is hypothesized that the S protein attached on cell surface is activated for fusion by natural dissociation of SI from S2, which was revealed in wt JHMV but not mutants derived from it, with or without MHVR-independent infection activity, respectively. Wild-type JHMV fails to infect BHK cells by a standard infection procedure, because the virus is not able to attach cells without MHVR. However, the S protein expressed on cell surface infected with wt can attach onto MHVR-negative cells by overlaying these cells, which induces fusion/infection of MHVR deficient cells (infected-cell overlay test). If MHVR-independent infection occurs as expected above, then we will be able to make wt JHMV infect cells by attaching virions onto cells without MHVR. To test this possibility, we employed the spinoculation method, which has been shown to facilitate the binding of viruses onto cells.