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Sci Transl Med. 2019 Jun 26;11(498). pii: eaat7726. doi: 10.1126/scitranslmed.aat7726.

A T164S mutation in the dengue virus NS1 protein is associated with greater disease severity in mice.

Author information

1
Program in Emerging Infectious Diseases, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore.
2
Department of Microbiology and Immunology, 5 Science Drive 2, Singapore 117545, Singapore.
3
MIVEGEC, UMR IRD 224-CNRS5290 Université de Montpellier, Montpellier, France.
4
Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, Victoria 3800, Australia.
5
Immunology Programme, Life Science Institute, National University of Singapore, Singapore 117456, Singapore.
6
Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, MD 20817, USA.
7
Bioinformatics Institute (A*STAR), 30 Biopolis St., Singapore 138671, Singapore.
8
Singapore Lipidomics Incubator (SLING), Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore.
9
Program in Emerging Infectious Diseases, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore. subhash.vasudevan@duke-nus.edu.sg.

Abstract

Dengue viruses cause severe and sudden human epidemics worldwide. The secreted form of the nonstructural protein 1 (sNS1) of dengue virus causes vascular leakage, a hallmark of severe dengue disease. Here, we reverse engineered the T164S mutation of NS1, associated with the severity of dengue epidemics in the Americas, into a dengue virus serotype 2 mildly infectious strain. The T164S mutant virus decreased infectious virus production and increased sNS1 production in mammalian cell lines and human peripheral blood mononuclear cells (PBMCs) without affecting viral RNA replication. Gene expression profiling of 268 inflammation-associated human genes revealed up-regulation of genes induced in response to vascular leakage. Infection of the mosquito vector Aedes aegypti with the T164S mutant virus resulted in increased viral load in the mosquito midgut and higher sNS1 production compared to wild-type virus infection. Infection of type 1 and 2 interferon receptor-deficient AG129 mice with the T164S mutant virus resulted in severe disease coupled with increased complement activation, tissue inflammation, and more rapid mortality compared to AG129 mice infected with wild-type virus. Molecular dynamics simulations predicted that mutant sNS1 formed stable dimers similar to the wild-type protein, whereas the hexameric mutant sNS1 was predicted to be unstable. Immunoaffinity-purified sNS1 from T164S mutant virus-infected mammalian cells was associated with different lipid classes compared to wild-type sNS1. Treatment of human PBMCs with sNS1 purified from T164S mutant virus resulted in a twofold higher production of proinflammatory cytokines, suggesting a mechanism for how mutant sNS1 may cause more severe dengue disease.

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