MAJOR AND MINOR RECEPTOR GROUP HUMAN RHINOVIRUSES PENETRATE FROM ENDOSOMES BY DIFFERENT MECHANISMS

Intercellular adhesion molecule 1 and the low-density lipoprotein rece ptor are used for cell entry by major and minor receptor group human r hinoviruses (HRVs), respectively. Whereas minor-group viruses, exempli fied by HRV2, transfer their genomic RNA to the cytoplasm through a po re in the endosomal membrane (E. Prchla, C. Plank, E. Wagner, D. Blaas , and R. Fuchs, J. Cell Biol. 131:111-123, 1995), the mechanism of in vice uncoating of major-group HRVs has not been elucidated so far, Usi ng free-flow electrophoresis, we performed a comparative analysis of c ell entry by HRV2 and the major group rhinovirus HRV14. Here we demons trate that this technique allows the separation of free viral particle s from those associated with early endosomes, late endosomes, and plas ma membranes, Upon free-how electrophoretic separation of microsomes, HRV14 was recovered from endosomes under conditions which prevent unco ating, whereas the proportion of free viral particles increased with t ime under conditions which promote uncoating, The remaining virus elut ed within numerous fractions corresponding to membraneous material, wi th no clear endosomal peaks being discernible, This suggests that unco ating of HRV14 results in lysis of the endosomal membrane and release of subvirol 135S and 80S particles into the cytoplasm.