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Wedekind C, Walker M, Little TJ. The separate and combined effects of MHC genotype, parasite clone, and host gender on the course of malaria in mice. BMC Genet 2006; 7:55. [PMID: 17118203 PMCID: PMC1664581 DOI: 10.1186/1471-2156-7-55] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2006] [Accepted: 11/21/2006] [Indexed: 11/25/2022] Open
Abstract
Background The link between host MHC (major histocompatibility complex) genotype and malaria is largely based on correlative data with little or no experimental control of potential confounding factors. We used an experimental mouse model to test for main effects of MHC-haplotypes, MHC heterozygosity, and MHC × parasite clone interactions. We experimentally infected MHC-congenic mice (F2 segregants, homo- and heterozygotes, males and females) with one of two clones of Plasmodium chabaudi and recorded disease progression. Results We found that MHC haplotype and parasite clone each have a significant influence on the course of the disease, but there was no significant host genotype by parasite genotype interaction. We found no evidence for overdominance nor any other sort of heterozygote advantage or disadvantage. Conclusion When tested under experimental conditions, variation in the MHC can significantly influence the course of malaria. However, MHC heterozygote advantage through overdominance or dominance of resistance cannot be assumed in the case of single-strain infections. Future studies might focus on the interaction between MHC heterozygosity and multiple-clone infections.
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Affiliation(s)
- Claus Wedekind
- Department of Ecology and Evolution, University of Lausanne, Biophore, 1015 Lausanne, Switzerland
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland, UK
| | - Mirjam Walker
- Institute of Zoo and Wildlife Biology, 10252 Berlin, Germany
- Natural History Museum Bern, 3005 Bern, Switzerland
- ZLB Behring AG, Wankdorfstr. 10, 3022 Bern, Switzerland
| | - Tom J Little
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland, UK
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Rülicke T, Guncz N, Wedekind C. Early maternal investment in mice: no evidence for compatible-genes sexual selection despite hybrid vigor. J Evol Biol 2006; 19:922-8. [PMID: 16674588 DOI: 10.1111/j.1420-9101.2005.01039.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Confronting a recently mated female with a strange male can induce a pregnancy block ('Bruce effect'). The physiology of this effect is well studied, but its functional significance is still not fully understood. The 'anticipated infanticide hypothesis' suggests that the pregnancy block serves to avoid the cost of embryogenesis and giving birth to offspring that are likely to be killed by a new territory holder. Some 'compatible-genes sexual selection hypotheses' suggest that the likelihood of a pregnancy block is also dependent on the female's perception of the stud's and the stimulus male's genetic quality. We used two inbred strains of mice (C57BL/6 and BALB/c) to test all possible combinations of female strain, stud strain, and stimulus strain under experimental conditions (N(total) = 241 mated females). As predicted from previous studies, we found increased rates of pregnancy blocks if stud and stimulus strains differed, and we found evidence for hybrid vigour in offspring of between-strain mating. Despite the observed heterosis, pregnancies of within-strain matings were not more likely to be blocked than pregnancies of between-strain matings. A power analysis revealed that if we missed an existing effect (type-II error), the effect must be very small. If a female gave birth, the number and weight of newborns were not significantly influenced by the stimulus males. In conclusion, we found no support for the 'compatible-genes sexual selection hypotheses'.
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Affiliation(s)
- T Rülicke
- Institute for Laboratory Animal Science, University of Zürich, Switzerland
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Wedekind C, Walker M, Little TJ. The course of malaria in mice: major histocompatibility complex (MHC) effects, but no general MHC heterozygote advantage in single-strain infections. Genetics 2005; 170:1427-30. [PMID: 15911576 PMCID: PMC1451180 DOI: 10.1534/genetics.105.040683] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A general MHC-heterozygote advantage in parasite-infected organisms is often assumed, although there is little experimental evidence for this. We tested the response of MHC-congenic mice (F2 segregants) to malaria and found the course of infection to be significantly influenced by MHC haplotype, parasite strain, and host gender. However, the MHC heterozygotes did worse than expected from the average response of the homozygotes.
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Affiliation(s)
- Claus Wedekind
- Zoological Institute, Division of Conservation Biology, University of Bern, 3012 Bern, Switzerland.
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McClelland EE, Adler FR, Granger DL, Potts WK. Major histocompatibility complex controls the trajectory but not host-specific adaptation during virulence evolution of the pathogenic fungus Cryptococcus neoformans. Proc Biol Sci 2004; 271:1557-64. [PMID: 15306300 PMCID: PMC1691764 DOI: 10.1098/rspb.2004.2736] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Genes of the major histocompatibility complex (MHC) play a critical role in immune recognition and are the most genetically diverse loci known. One hypothesis to explain this diversity postulates that pathogens adapt to common MHC haplotypes and thus favour selection of new or rare alleles. To determine whether the pathogenic yeast Cryptococcus neoformans adapts to MHC-dependent immune responses, it was serially passaged in two independent replicate lines of five B10 MHC-congenic strains and Balb/c mice. All passaged lines increased in virulence as measured by reduced host survival. MHC influenced the rate (trajectory) of virulence increase during passages as measured by significant differences in mortality rate (p < 0.001). However, when the post-passage strains were tested, no MHC differences in mortality rate remained and only minor differences in titres were observed. Also contrary to expectations, increased virulence in three lines passaged in B10 mice had a larger effect in Balb/c mice, and the evolution of virulence in lines passaged in alternating hosts was not retarded. To our knowledge, these data represent the first experimental test of MHC-specific adaptation in a non-viral pathogen. The failure to observe MHC effects despite dramatically increased virulence and host-genotype-specific adaptation to non-MHC genes suggests that escape of MHC-dependent immune recognition may be difficult for pathogens with unlimited epitopes or that other virulence factors can swamp MHC effects.
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Affiliation(s)
- Erin E McClelland
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA.
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McClelland EE, Damjanovich K, Gardner K, Groesbeck ZJ, Ma MS, Nibley M, Richardson KS, Wilkinson M, Morrison LC, Bernhardt P, Potts WK. Infection-dependent phenotypes in MHC-congenic mice are not due to MHC: can we trust congenic animals? BMC Immunol 2004; 5:14. [PMID: 15245582 PMCID: PMC481063 DOI: 10.1186/1471-2172-5-14] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2004] [Accepted: 07/09/2004] [Indexed: 11/23/2022] Open
Abstract
Background Congenic strains of mice are assumed to differ only at a single gene or region of the genome. These mice have great importance in evaluating the function of genes. However, their utility depends on the maintenance of this true congenic nature. Although, accumulating evidence suggests that congenic strains suffer genetic divergence that could compromise interpretation of experimental results, this problem is usually ignored. During coinfection studies with Salmonella typhimurium and Theiler's murine encephalomyelitis virus (TMEV) in major histocompatibility complex (MHC)-congenic mice, we conducted the proper F2 controls and discovered significant differences between these F2 animals and MHC-genotype-matched P0 and F1 animals in weight gain and pathogen load. To systematically evaluate the apparent non-MHC differences in these mice, we infected all three generations (P0, F1 and F2) for 5 MHC genotypes (b/b, b/q and q/q as well as d/d, d/q, and q/q) with Salmonella and TMEV. Results Infected P0 MHC q/q congenic homozygotes lost significantly more weight (p = 0.02) and had significantly higher Salmonella (p < 0.01) and TMEV (p = 0.02) titers than the infected F2 q/q homozygotes. Neither weight nor pathogen load differences were present in sham-infected controls. Conclusions These data suggest that these strains differ for genes other than those in the MHC congenic region. The most likely explanation is that deleterious recessive mutations affecting response to infection have accumulated in the more than 40 years that this B10.Q-H-2q MHC-congenic strain has been separated from its B10-H-2b parental strain. During typical experiments with congenic strains, the phenotypes of these accumulated mutations will be falsely ascribed to the congenic gene(s). This problem likely affects any strains separated for appreciable time and while usually ignored, can be avoided with the use of F2 segregants.
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Affiliation(s)
- Erin E McClelland
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
| | - Kristy Damjanovich
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
| | - Kyle Gardner
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
| | - Zack J Groesbeck
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
| | - Maggie S Ma
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
| | - Megan Nibley
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
| | - Kelly S Richardson
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
| | - Maureen Wilkinson
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
| | - Linda C Morrison
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
| | - Paul Bernhardt
- Department of Educational Psychology, University of Utah, 1705 East Central Campus Drive, Salt Lake City, UT 84112 USA
| | - Wayne K Potts
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112 USA
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McClelland EE, Granger DL, Potts WK. Major histocompatibility complex-dependent susceptibility to Cryptococcus neoformans in mice. Infect Immun 2003; 71:4815-7. [PMID: 12874366 PMCID: PMC166009 DOI: 10.1128/iai.71.8.4815-4817.2003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To evaluate the role of major histocompatibility complex (MHC) genes in the resistance to Cryptococcus neoformans, we conducted infection experiments in MHC-congenic strains of mice. Significant MHC-dependent susceptibility differences were found among homozygotes and heterozygotes. This study is the first experimental demonstration of MHC-dependent susceptibility to C. neoformans infections in mice and indicates that MHC genes can be important in host resistance.
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Affiliation(s)
- Erin E McClelland
- Biology Department, University of Utah, Salt Lake City, Utah 84112, USA.
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McClelland EE, Penn DJ, Potts WK. Major histocompatibility complex heterozygote superiority during coinfection. Infect Immun 2003; 71:2079-86. [PMID: 12654829 PMCID: PMC152037 DOI: 10.1128/iai.71.4.2079-2086.2003] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genes of the major histocompatibility complex (MHC) play a critical role in immune recognition, and many alleles confer susceptibility to infectious and autoimmune diseases. How these deleterious alleles persist in populations is controversial. One hypothesis postulates that MHC heterozygote superiority emerges over multiple infections because MHC-mediated resistance is generally dominant and many allele-specific susceptibilities to pathogens will be masked by the resistant allele in heterozygotes. We tested this hypothesis by using experimental coinfections with Salmonella enterica (serovar Typhimurium C5TS) and Theiler's murine encephalomyelitis virus (TMEV) in MHC-congenic mouse strains where one haplotype was resistant to Salmonella and the other was resistant to TMEV. MHC heterozygotes were superior to both homozygotes in 7 out of 8 comparisons (P = 0.0024), and the mean standardized pathogen load of heterozygotes was reduced by 41% over that of homozygotes (P = 0.01). In contrast, no heterozygote superiority was observed when the MHC haplotype combinations had similar susceptibility profiles to the two pathogens. This is the first experimental evidence for MHC heterozygote superiority against multiple pathogens, a mechanism that would contribute to the evolution of MHC diversity and explain the persistence of alleles conferring susceptibility to disease.
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Affiliation(s)
- Erin E McClelland
- Biology Department, University of Utah, Salt Lake City, UT 84112, USA
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Carroll LS, Penn DJ, Potts WK. Discrimination of MHC-derived odors by untrained mice is consistent with divergence in peptide-binding region residues. Proc Natl Acad Sci U S A 2002; 99:2187-92. [PMID: 11842193 PMCID: PMC122340 DOI: 10.1073/pnas.042244899] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Genes of the major histocompatibility complex (MHC) play a central role in immune recognition, yet they also influence the odor of individuals. Mice can be trained to distinguish odors mediated by classical MHC loci; however, training can introduce confounding behavioral artifacts. This study demonstrates that mice can distinguish some, but not all, naturally occurring allelic variants at classical MHC loci without prior training. This result suggests that MHC-disassortative mating preferences might operate by means of small MHC-based odor differences, and could therefore contribute to diversifying selection acting on MHC loci. Here we show that odors of two MHC mutant mouse strains (bm1 and bm3) can be distinguished, even after genetic background is controlled by intercrossing strains. These two strains differ by five amino acids, three of which are predicted to chemically contact peptides bound to the peptide-binding region (PBR), the site of antigen presentation for T cell recognition. However, the odors of neither bm1 nor bm3 were distinguished from their parental B6 haplotype after randomizing genomic background, despite discrimination of pure-bred B6 and bm1 strain odors. These combined results suggest that (i) there may be an MHC odor discrimination threshold based on divergence in PBR residues, providing a more logical pattern of MHC-based odor discrimination than found in previous training studies, where discrimination ability was not correlated with PBR divergence; and (ii) additional (non-MHC) mutations that influence odor have accumulated in these strains during the 100 generations of divergence between pure B6 and bm1 strains.
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Affiliation(s)
- Lara S Carroll
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112-0841, USA.
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