AMINO-ACID CHANGES IN THE SINDBIS VIRUS E2 GLYCOPROTEIN THAT INCREASENEUROVIRULENCE IMPROVE ENTRY INTO NEUROBLASTOMA-CELLS

Sindbis virus (SV) is an alphavirus that causes encephalitis in mice a nd results in age-dependent mortality, The outcome is dependent on the virus strain, Residues at 55 and 172 in the E2 glycoprotein determine the neurovirulence for mice of different ages and the efficiency of r eplication in the nervous system and neuronal cells, To determine the effects of these two residues on the initial steps in replication, we studied viruses with a histidine or glutamine at E2 position 55 and a glycine or an arginine at position 172, E2[H(55)G(172)], E2 [Q(55)G(17 2)], E2[H55R172], and E2[Q(55)R(172)], The production of virus, was de tected earlier for viruses with a histidine at E2 position 55 in BHK-2 1 cells (4 to 6 versus 6 to 8 h) and for E2[H(55)G(172)] in N18 cells (6 versus 8 to 10 h), As shown previously, viruses with a glycine at E 2 position 172 bound more efficiently to N18 cells and a histidine at E2 position 55 further improved binding only slightly, Viruses with E2 [H-55] exhibited more rapid internalization and degradation of viral p roteins in both BHK-21 and N18 cell, Incubation of E2[H(55)G(172)] and E2[Q(55)G(172)] at various pHs and temperatures did not reveal differ ences in virion stability. These data suggest that the amino acids at E2 positions 172 and 55 affect both adsorption and penetration of SV a nd that these early steps in the replicative pathway contribute to inc reased neurovirulence.