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The overwhelming increase of dengue virus (DENV) infections in recent years shows that current strategies to combat dengue do not work. The lack of a highly effective dengue vaccine and the limited effectivity of vector controls exacerbate this situation. To point the way to a novel method of creating DENV vaccine candidates, here we disrupted the codon usage in a DENV-2 reporter replicon to generate variants with different replication characteristics. Six different mutated constructs containing stretches of altered codon usage in the non-structural genes were generated. The mutated sequences were deoptimized to the least favorable codons for human cells. We studied the replication efficiency of these constructs by measuring luciferase reporter activity, relative RNA fold change, and NS1 secretion. Our findings showed that the level of virus attenuation is closely associated with the amount of codon deoptimization. Indeed, replication was completely abolished in extensively-deoptimized constructs D2Rep-6 and D2Rep-5, intermediate with constructs D2Rep-4 (771 bp silent mutations) and D2Rep-3 (756 bp silent mutations) and restored almost to wildtype levels with constructs D2Rep-2 (394 silent mutations) and D2Rep-1 (48 silent mutations). We also determined that the position of codon deoptimization within the genome is crucial to the degree of attenuation observed. Based on our analysis, we propose that the design for an ideal DENV vaccine candidate could include 700-1500 silent mutations within the NS2A and NS3 genes. Our results suggest that codon deoptimization is an ideal strategy that can readily be used to develop a DENV vaccine candidate with "fine-tuned" attenuation.

Original publication

DOI

10.1016/j.vaccine.2019.03.062

Type

Journal article

Journal

Vaccine

Publication Date

05/2019

Volume

37

Pages

2857 - 2863

Addresses

Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Parkville, Victoria, Australia; Institute of Vector Borne Disease, Monash University, Clayton, Victoria, Australia.