A Single Mutation in the E2 Glycoprotein Important for Neurovirulence Influences Binding of Sindbis Virus to Neuroblastoma Cells
2002
The amino acid at position 55 of the E2 glycoprotein (E255) of Sindbis virus (SV) is a critical determinant of SV neurovirulence in mice. Recombinant virus strain TE (E255 histidine) differs only at this position from virus strain 633 (E255 glutamine), yet TE is considerably more neurovirulent than 633. TE replicates better than 633 in a neuroblastoma cell line (N18), but similarly in BHK cells. Immunofluorescence staining showed that most N18 cells were infected by TE at a multiplicity of infection (MOI) of 50 to 500 and by 633 only at an MOI of 5,000, while both viruses infected essentially 100% of BHK cells at an MOI of 5. When exposed to pH 5, TE and 633 viruses fused to similar extents with liposomes derived from BHK or N18 cell lipids, but fusion with N18-derived liposomes was less extensive (15 to 20%) than fusion with BHK-derived liposomes (50%). Binding of TE and 633 to N18, but not BHK, cells was dependent on the medium used for virus binding. Differences between TE and 633 binding to N18 cells were evident in Dulbecco’s modified Eagle medium (DMEM), but not in RPMI. In DMEM, the binding efficiency of 633 decreased significantly as the pH was raised from 6.5 to 8.0, while that of TE did not change. The same pattern was observed with RPMI when the ionic strength of RPMI was increased to that of DMEM. TE bound better to heparin-Sepharose than 633, but this difference was not pH dependent. Growth of N18 and BHK cells in sodium chlorate to eliminate all sulfation decreased virus-cell binding, suggesting the involvement of sulfated molecules on the cell surface. Taken together, the presence of glutamine at E255 impairs SV binding to neural cells under conditions characteristic of interstitial fluid. We conclude that mutation to histidine participates in or stabilizes the interaction between the virus and the surface of neural cells, contributing to greater neurovirulence. Sindbis virus (SV), the prototype member of the genus Alphavirus in the family Togaviridae, causes age-dependent mortality in mice (23). In newborn mice, the AR339 strain of SV causes acute fatal encephalomyeliitis while in older mice the disease is mild and nonfatal. A neuroadapted strain of SV isolated after serial intracerebral passages of SV causes high mortality in older mice associated with severe encephalomyelitis resulting in kyphoscoliosis and hindlimb paralysis (24). Fatal infection correlates with the induction of neuronal death, the primary target cells of SV infection in the nervous system (34). SV is a plus-strand RNA virus with a cell-derived lipid bilayer membrane containing heterodimers of the two viral envelope glycoproteins, E1 and E2 (51). Entry of SV into host cells involves association of the virus with the cell surface, interaction with specific receptors, clathrin-mediated endocytosis, and acid-induced fusion of SV with the endosomal membrane to release the nucleocapsid into the cytoplasm (29). Coordinated association and dissociation of the E1 and E2 glycoproteins during interaction with the cellular membrane and exposure to acidic pH are required for alphaviruses to deliver genomic RNA into the cytoplasm (19). The E2 glyco
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
61
References
37
Citations
NaN
KQI