Optimality analysis of Th1/Th2 immune responses during microparasite- macroparasite co-infection, with epidemiological feedbacks

Andy Fenton, Tracey Lamb, Andrea L. Graham

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


Individuals are typically co-infected by a diverse community of microparasites (e.g. viruses or protozoa) and macroparasites (e.g. helminths). Vertebrates respond to these parasites differently, typically mounting T helper type 1 (Th1) responses against microparasites and Th2 responses against macroparasites. These two responses may be antagonistic such that hosts face a 'decision' of how to allocate potentially limiting resources. Such decisions at the individual host level will influence parasite abundance at the population level which, in turn, will feed back upon the individual level. We take a first step towards a complete theoretical framework by placing an analysis of optimal immune responses under microparasite-macroparasite co-infection within an epidemiological framework. We show that the optimal immune allocation is quantitatively sensitive to the shape of the trade-off curve and qualitatively sensitive to life-history traits of the host, microparasite and macroparasite. This model represents an important first step in placing optimality models of the immune response to co-infection into an epidemiological framework. Ultimately, however, a more complete framework is needed to bring together the optimal strategy at the individual level and the population-level consequences of those responses, before we can truly understand the evolution of host immune responses under parasite co-infection.

Original languageEnglish (US)
Pages (from-to)841-853
Number of pages13
Issue number7
StatePublished - Jun 2008
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Infectious Diseases
  • Animal Science and Zoology
  • Parasitology


  • Allocation decision
  • Bacteria
  • Epidemiology
  • Evolution
  • Mathematical model
  • Parasitic helminth
  • Trade-off
  • Virus


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