Glycosylation of the dengue 2 virus E protein at N67 is critical for virus growth in vitro but not for growth in intrathoracically inoculated Aedes aegypti mosquitoes.

To determine the importance of dengue 2 virus (DEN2V) envelope (E) protein glycosylation, virus mutants in one or both of the N-linked glycosylation motifs were prepared. We found that while the E2 mutant virus (N153Q) replicated in mammalian and mosquito cells, the E1 (N67Q) and E1/2 (N67Q and N153Q) mutant viruses were unable to grow in mammalian cells. Infection of C6/36 mosquito cells with either the E1 or E1/2 mutants resulted in the introduction of a compensatory mutation, K64N, restoring glycosylation in the area. All mutants replicated similarly in inoculated Aedes aegypti mosquitoes, with no change in their mutations. These results suggest that N-linked glycosylation of the E protein is not necessary for DEN2V replication in mosquitoes, however N-linked glycosylation at amino acid N67 (or nearby N64) is critical for the survival of the virus in either mammalian or insect cell culture.