title: The evolution of costly acquired immune memory.
abstract: A key feature of the vertebrate adaptive immune system is acquired immune memory, whereby hosts launch a faster and heightened response when challenged by previously encountered pathogens, preventing full infection. Here, we use a mathematical model to explore the role of ecological and epidemiological processes in shaping selection for costly acquired immune memory. Applying the framework of adaptive dynamics to the classic SIR (Susceptible-Infected-Recovered) epidemiological model, we focus on the conditions that may lead hosts to evolve high levels of immunity. Linking our work to previous theory, we show how investment in immune memory may be greatest at long or intermediate host lifespans depending on whether immunity is long lasting. High initial costs to gain immunity are also found to be essential for a highly effective immune memory. We also find that high disease infectivity and sterility, but intermediate virulence and immune period, increase selection for immunity. Diversity in host populations through evolutionary branching is found to be possible but only for a limited range of parameter space. Our model suggests that specific ecological and epidemiological conditions have to be met for acquired immune memory to evolve.
authors.affiliation: Mathematics and Statistics, University of Sheffield Sheffield, S3 7RH, U.K ; Biosciences, University of Exeter, Cornwall Campus Penryn, TR10 9EZ.
authors.forename: Alex
authors.initials: A
authors.lastname: Best
authors.forename: Andy
authors.initials: A
authors.lastname: Hoyle
keywords: Acquired immunity; SIR; host-parasite; immune memory
references.citation: J R Soc Interface. 2010 Apr 6;7(45):561-71
references.pmid: 19955121
references.citation: Adv Immunol. 2011;109:125-57
references.pmid: 21569914
references.citation: Bull Math Biol. 1991;53(1-2):33-55
references.pmid: 2059741
references.citation: Annu Rev Entomol. 2005;50:529-51
references.pmid: 15471530
references.citation: Cell. 1997 Oct 31;91(3):295-8
references.pmid: 9363937
references.citation: Trends Ecol Evol. 2004 Feb;19(2):58-60
references.pmid: 16701227
references.citation: Proc Biol Sci. 1998 Feb 22;265(1393):317-25
references.pmid: 9523434
references.citation: J Math Biol. 1989;27(3):233-58
references.pmid: 2746140
references.citation: Evolution. 2012 Oct;66(10):3067-78
references.pmid: 23025598
references.citation: J Allergy Clin Immunol. 2010 Feb;125(2 Suppl 2):S33-40
references.pmid: 20061006
references.citation: J Theor Biol. 2012 Sep 21;309:176-84
references.pmid: 22721993
references.citation: Proc Biol Sci. 2004 Apr 7;271(1540):715-23
references.pmid: 15209105
references.citation: J Theor Biol. 1999 Nov 7;201(1):13-23
references.pmid: 10534432
references.citation: Nature. 1979 Aug 2;280(5721):361-7
references.pmid: 460412
references.citation: Nat Rev Immunol. 2010 Aug;10(8):543-53
references.pmid: 20651744
references.citation: J R Soc Interface. 2012 Dec 26;10(80):20120887
references.pmid: 23269850
references.citation: Am Nat. 2004 Feb;163(2):277-94
references.pmid: 14970928
references.citation: Nat Rev Immunol. 2012 Jan 25;12(2):89-100
references.pmid: 22273771
references.citation: BMC Evol Biol. 2010 Dec 08;10:380
references.pmid: 21143840
references.citation: Proc Biol Sci. 1994 Jun 22;256(1347):231-8
references.pmid: 7914705
references.citation: Cell. 2006 Feb 24;124(4):815-22
references.pmid: 16497590
references.citation: J Theor Biol. 1997 Apr 7;185(3):333-43
references.pmid: 9156083
references.citation: Curr Biol. 2003 Sep 16;13(18):1648-52
references.pmid: 13678598
references.citation: Science. 2000 Nov 10;290(5494):1166-8
references.pmid: 11073456
references.citation: Scand J Immunol. 1999 Nov;50(5):456-60
references.pmid: 10564546
references.citation: Evolution. 2007 Jan;61(1):2-14
references.pmid: 17300423
references.citation: J Math Biol. 1997 Aug;35(7):825-42
references.pmid: 9269738