Single Amino Acid Mutation in Dengue Virus NS4B Protein Has Opposing Effects on Viral Proliferation in Mammalian and Mosquito Cells

Abstract

Dengue virus (DENV) has a considerable impact on the global health and is known to cause morbidity and mortality every year. By passaging DENV2 in baby hamster kidney (BHK)-21 cells, we isolated a mutant clone of DENV2 that shows rapid cytopathic effects in BHK-21 cells as compared with that showed by the parent strain. To investigate the relationship between amino acid mutations and proliferation activity of the isolated DENV2 clone, we performed full genome sequencing and identified 3 amino acid mutations in the coding region, the envelope T120K, NS4A M85T, and NS4B G124A. Genetically modified recombinant DENV2 (rDENV2) carrying the NS4A M85T and NS4B G124A mutations produced higher titers of progeny virus in BHK-21, Vero, and Huh-7 cells than in the wild-type (WT) rDENV2. rDENV2 with mutations at NS4A M85T and NS4B G124A failed to produce any plaques in C6/36 mosquito cell lines. Furthermore, rDENV2 possessing only the NS4B G124A mutation showed no plaque production in C6/36 cells but had higher viral titers in Vero and Huh-7 cells than the WT rDENV2 had. Our results clearly showed that the DENV2 NS4B G124A mutation has opposing effects on the virus proliferation in mosquito and certain mammalian cell lines.