PRODUCTIVE PENETRATION OF ROTAVIRUS IN CULTURED-CELLS INDUCES COENTRYOF THE TRANSLATION INHIBITOR ALPHA-SARCIN

Internalization of rotavirus in MA104 cells was found to induce coentr y of alpha-sarcin, a toxin that inhibits translation in cell-free syst ems and to which cells are normally impermeable. Entry of the toxin, m easured by inhibition of protein synthesis at early times after infect ion, correlated with virus penetration leading to expression of infect ivity, since toxin entry (1) was induced only by trypsin-treated tripl e-layered virions, to a degree dependent on the toxin and the virus co ncentration; (2) correlated with the degree of permissivity of differe nt cell lines to rotavirus infection; (3) was inhibited to a similar e xtent as infectivity by treatment of cells with neuraminidaae; and (4) was inhibited by pre-or postadsorption incubation of the virus with n eutralizing monoclonal antibodies to VP7 and VP4 (VP8). Neither the v irus infectivity nor the toxin coentry was significantly affected by t reatment of cells with bafilomycin Al, an inhibitor of the vacuolar pr oton ATPase, indicating that both events are independent of the endoso mal acid pH. Virus-like particles (VLP), composed of rotavirus protein s 2/6/7/4, but not 2/6/7 or 2/6, were able to induce toxin entry as ef ficiently as virions. Use of genetically modified VLP in combination w ith the toxin coentry assay, which measures entry through a productive pathway, should allow identification of the regions of the outer caps id proteins essential for rotavirus penetration. (C) 1997 Academic Pre ss.