The wMel Wolbachia strain blocks dengue and invades caged Aedes aegypti populations

Journal name:
Nature
Volume:
476,
Pages:
450–453
Date published:
DOI:
doi:10.1038/nature10355
Received
Accepted
Published online

Dengue fever is the most important mosquito-borne viral disease of humans with more than 50 million cases estimated annually in more than 100 countries1, 2. Disturbingly, the geographic range of dengue is currently expanding and the severity of outbreaks is increasing2, 3, 4. Control options for dengue are very limited and currently focus on reducing population abundance of the major mosquito vector, Aedes aegypti5, 6. These strategies are failing to reduce dengue incidence in tropical communities and there is an urgent need for effective alternatives. It has been proposed that endosymbiotic bacterial Wolbachia infections of insects might be used in novel strategies for dengue control7, 8, 9. For example, the wMelPop-CLA Wolbachia strain reduces the lifespan of adult A. aegypti mosquitoes in stably transinfected lines8. This life-shortening phenotype was predicted to reduce the potential for dengue transmission. The recent discovery that several Wolbachia infections, including wMelPop-CLA, can also directly influence the susceptibility of insects to infection with a range of insect and human pathogens9, 10, 11 has markedly changed the potential for Wolbachia infections to control human diseases. Here we describe the successful transinfection of A. aegypti with the avirulent wMel strain of Wolbachia, which induces the reproductive phenotype cytoplasmic incompatibility with minimal apparent fitness costs and high maternal transmission, providing optimal phenotypic effects for invasion. Under semi-field conditions, the wMel strain increased from an initial starting frequency of 0.65 to near fixation within a few generations, invading A. aegypti populations at an accelerated rate relative to trials with the wMelPop-CLA strain. We also show that wMel and wMelPop-CLA strains block transmission of dengue serotype 2 (DENV-2) in A. aegypti, forming the basis of a practical approach to dengue suppression12.

At a glance

Figures

  1. Tissue distribution of the wMel strain in transinfected A. aegypti female mosquitoes.
    Figure 1: Tissue distribution of the wMel strain in transinfected A. aegypti female mosquitoes.

    Fluorescence in situ hybridization (FISH) of paraffin sections showing the localization of Wolbachia (red) in tissues of 7-day-old female A. aegypti mosquitoes. Sections were hybridized with two Wolbachia-specific 16S rRNA probes labelled with rhodamine. DNA is stained with DAPI (blue). A green GFP filter was used to enhance contrast. sg, salivary gland; c, cardia.

  2. Predicted and observed invasion dynamics under semi-field conditions.
    Figure 2: Predicted and observed invasion dynamics under semi-field conditions.

    a, b, wMel strain (a) and wMelPop-CLA strain (b) infection frequencies in larvae in cages A (red curves and symbols) and B (black curves and symbols). Curves indicate model-based predictions, as explained in the supplementary information. Symbols denote frequencies observed in the cages with error bars indicating binomial standard errors. Infected pupae initially comprised 65% of the released population in each cage. Eggs were collected from the cage in ovitraps and pupae developing from these eggs were released back into the cage at 3-day intervals. To simulate field releases involving repeated releases of infected mosquitoes, additional infected pupae were released into the cage, comprising a third of the total pupae released.

  3. Dengue infection levels in mosquitoes.
    Figure 3: Dengue infection levels in mosquitoes.

    Mosquitoes were fed DENV-2-infected blood orally (DENV-2 titre 1.5×107 plaque-forming units per ml) and titre determined at 14days after infection. a, qPCR of total dengue virus in whole female mosquitoes (n = 19–30). Bars represent overall means±s.e.m. across three independent replicate experiments. White bar, Wolbachia-uninfected wild-type control mosquitoes; blue bar, wMel-infected MGYP2.OUT; red bar, wMelPop-CLA-infected PGYP1.OUT. b, qPCR of disseminated dengue virus in the legs of individual Wolbachia-uninfected MGYP2.tet (black circles), wMel-infected MGYP2 (blue triangles) and wMelPop-CLA infected PGYP1 (red squares) mosquitoes (n = 23–30).

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Author information

  1. These authors contributed equally to this work.

    • T. Walker &
    • P. H. Johnson

Affiliations

  1. School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia

    • T. Walker,
    • L. A. Moreira,
    • I. Iturbe-Ormaetxe,
    • F. D. Frentiu,
    • C. J. McMeniman,
    • Y. S. Leong,
    • Y. Dong &
    • S. L. O’Neill
  2. Bio21 Institute, Department of Genetics, The University of Melbourne, Victoria 3010, Australia

    • J. Axford,
    • P. Kriesner &
    • A. A. Hoffmann
  3. School of Public Health and Tropical Medicine and Rehabilitative Sciences, James Cook University, Cairns, Queensland 4870, Australia

    • P. H. Johnson &
    • S. A. Ritchie
  4. Biomathematics Graduate Program and Department of Mathematics, North Carolina State University, Raleigh, North Carolina 27695, USA

    • A. L. Lloyd
  5. Fogarty International Center, National Institutes of Health, Bethesda, Maryland 20892, USA

    • A. L. Lloyd
  6. School of Biological Sciences, Monash University, Victoria 3800, Australia

    • S. L. O’Neill
  7. Present addresses: Centro de Pesquisas René Rachou-Fiocruz, Belo Horizonte, MG 30190, Brasil (L.A.M.); Laboratory of Neurogenetics and Behavior, The Rockefeller University, 1230 York Avenue, Campus Box 63, New York, New York10065, USA (C.J.M.).

    • L. A. Moreira &
    • C. J. McMeniman

Contributions

T.W. performed transinfection and initial phenotypic characterization of the infection. P.H.J., Y.S.L., Y.D. and S.A.R. performed cage invasion experiments and fecundity assays on outbred mosquito lines. T.W., L.A.M. and F.D.F. carried out vector competence assays. I.I.-O. performed FISH. C.J.M. established cell lines for transinfection. J.A. and P.K. performed cytoplasmic incompatibility and lifespan assays on outbred mosquito lines. A.L.L. undertook modelling studies. T.W. and A.A.H. performed data analysis. T.W., P.H.J., S.L.O. and A.A.H. wrote the paper. S.L.O., A.A.H. and S.A.R. provided oversight of the design and direction of the work.

Competing financial interests

The authors declare no competing financial interests.

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Supplementary information

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  1. Supplementary Information (4.9M)

    The file contains Supplementary Figures 1- 8 with legends, Supplementary Tables 1- 2, Supplementary Text and Data and additional references.

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