A single amino acid replacement of tyrosine with histidine at position 172 in BmNPV T3 GP64 decreases viral proliferation in silkworm larvae despite increasing membrane fusion activity with BmN cells

摘要

In the infection process of BmNPV, GP64, the major membrane protein of budded viruses, is required for binding to host cell receptors and for pH-dependent membrane fusion and is, therefore, essential for viral infection. Based on previous studies, we predicted that tyrosine at position 172 of T3 GP64 was an important amino acid residue for membrane fusion function. In this study, we examined the effects of replacement of the amino acid in GP64 on the proliferation of BmNPV T3 in BmN cells and silkworm larvae as well as its membrane fusion activity. Y172 T3 H increased both membrane fusion activity and early viral proliferation in BmN cells. On the other hand, viral proliferation in silkworm larvae was significantly decreased, and the survival time of infected larvae was longer by 24 h. These results show that Y172 T3 in GP64 is implicated in efficient BmNPV proliferation in the silkworm larvae, possibly through membrane fusion activity.