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 global health and causes morbidity and mortality each year. Through the passages of a DENV2 in BHK-21 cells, we have isolated a mutant clone of DENV2 which reveals cytopathic effects (CPE) rapidly compared to the parent strain in BHK-21 cells. To investigate the relationship between amino acid mutations and proliferation activity of the isolated DENV2 clone, we performed full genome sequencing and identified three amino acid mutations in its coding region, the Envelope (Env) T120K, NS4A M85T and NS4B G124A, compared to that of the parent strain. 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 compared to wild-type (WT) rDENV2. Surprisingly, rDENV2 with mutations at NS4A M85T and NS4B G124A did not produce any plaques in C6/36 mosquito cell lines. Furthermore, rDENV2 possessing only the NS4B G124A mutation did not produce any plaques in C6/36 cells; however, it had higher viral titers in Vero and Huh-7 cells compared to WT rDENV2. Our results clearly showed that the DENV2 NS4B G124A mutation has opposing effects on viral proliferation in certain mammalian cells and mosquito cells.