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The role of immune-mediated apparent competition in genetically diverse malaria infections

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Author

  • Lars Råberg
  • J C de Roode
  • A S Bell
  • P Stamou
  • D Gray
  • A F Read

Summary, in English

Competitive interactions between coinfecting genotypes of the same pathogen can impose selection on virulence, but the direction of this selection depends on the mechanisms behind the interactions. Here, we investigate how host immune responses contribute to competition between clones in mixed infections of the rodent malaria parasite Plasmodium chabaudi. We studied single and mixed infections of a virulent and an avirulent clone and compared the extent of competition in immunodeficient and immunocompetent mice (nude mice and T cell-reconstituted nude mice, respectively). In immunocompetent mice, the avirulent clone suffered more from competition than did the virulent clone. The competitive suppression of the avirulent clone was alleviated in immunodeficient mice. Moreover, the relative density of the avirulent clone in mixed infections was higher in immunodeficient than in immunocompetent mice. We conclude that immune-mediated interactions contributed to competitive suppression of the avirulent clone, although other mechanisms, presumably competition for resources such as red blood cells, must also be important. Because only the avirulent clone suffered from immune-mediated competition, this mechanism should contribute to selection for increased virulence in mixed infections in this host-parasite system. As far as we are aware, this is the first direct experimental evidence of immune-mediated apparent competition in any host-parasite system.

Publishing year

2006

Language

English

Pages

41-53

Publication/Series

American Naturalist

Volume

168

Issue

1

Document type

Journal article

Publisher

University of Chicago Press

Topic

  • Biological Sciences

Keywords

  • within-host competition.
  • quantitative PCR
  • indirect effects
  • multiple infection

Status

Published

Research group

  • Molecular Ecology and Evolution Lab

ISBN/ISSN/Other

  • ISSN: 0003-0147