Defining the Drivers of Immune Variation

Lead Research Organisation: University of Manchester
Department Name: School of Biological Sciences

Abstract

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Technical Summary

The heterogeneity between individuals in their immune systems is vast. Understanding the key drivers of immune variation is important as immune trait variability underpins our understanding of disease susceptibility and effectiveness of vaccines. Surprisingly therefore the main drivers of immune variation are poorly defined.
Studies in laboratory mice have contributed to our understanding of the immune system. However they cannot answer questions relating to the relative contribution of heritable and non-heritable factors in shaping the immune system, as they are conducted in controlled conditions with usually just one variable (eg genetics, infection or age).
Using our highly tractable wild mouse population on the Isle of May, where longitudinal analyses of immune responsiveness is possible, we will define the key drivers of immune variation by quantifying functional units of the immune system: cytokines, cell populations and antibody responses, in the context of age, genetics and infection. Specifically we will conduct a cross-sectional study, with groups of mice vaccinated with the model antigen ovalbumin, or sham vaccinated, in the presence or absence of specific infections, and a longitudinal study where we will track immune responses in blood samples over time using a mark, release, recapture protocol. To dissect the contribution of infection to immune variation we will remove key parasite species from a proportion of animals. To dissect the contribution of age to immune variation we will quantify panels of immune markers in blood over time. To understand the contribution of genetics to immune variation we will SNP genotype animals to estimate their relatedness and trait heritability.
By analysing many components of the immune system in the context of heritability, infection and age we will identify how the immune system is shaped. Thus we will define whether the many contributors to immune variability have their basis in heritable or non-heritable factors

Planned Impact

Individuals vary in their immune response to infectious disease. Outside of the laboratory, heritable and non-heritable influences combine to impinge on the "decision" as to what sort of immune response ultimately occurs. We do not know how the degree of variability changes as an animal ages and exposures to infectious diseases accumulate. Such variation will have profound effects on the outcome of infectious exposure, to vaccination, and transmission of pathogens.

We do not know the extent of immune variation in wild population of animals; our research will define the main drivers of immune variation in wild mouse populations.

There will thus be a number of impacts as detailed below:

1. Academic community: A wide range of scientists will benefit from our work. Our data will be of interest to immunologists and infectious-disease biologists researching the underlying mechanisms that regulate immunity during health and disease. Epidemiologists and vaccinologists will also benefit from our proposed research as understanding the main drivers of immune variation will inform treatment strategies.

We will ensure our work reaches these varied scientific audiences by publishing our work in both immunology and ecology journals, and by attending national and international conferences, presenting our work orally or via poster. We will also seek to organise Wildlife Immunology focussed sessions at both the British Society for Parasitology and the British Society for Immunology national meetings. (Time frame 1-3 years)

2. General public: Engaging with the public represents our most immediate tangible impact. Our data will be used as a basis for a range of public engagement events achieving educational benefits to the general public. We will develop new activities including a game identifying how immune responses vary with age, infection and genetic makeup. This will increase awareness of the importance of immune responses in the maintenance of health, and the ways scientists carry out basic research with a view to better understanding complex systems.

We will also explain our research project through an exhibit on display in the Visitors centre on the Isle of May. The exhibit will cover not only the concepts behind our research project, focussing on the consequences of immune responses for survival and fitness, but also will tell the story of the Isle of May mice and their unique heritage. The Isle of May is a popular destination for birdwatchers, naturalists and photographers during the Summer months and thus we expect to reach a different group of the general public to the groups who frequently visit for example museums.
 
Description Please Note: The BBSRC research project grant awarded to the University of Manchester (BB/P018157/1) is part of a joint grant application with the University of Nottingham (BB/P017827/1). The University of Nottingham is the lead Institute. Both Universities received no-income extensions. The University of Manchester (BB/P018157/1) grant ended 31st January 2022; however the lead institute (Nottingham University) had a revised end date of December 2022.

The overall aim of the project was to examine the genetic and environmental (infections, season, diet) influences on immune responses. Immune responses vary between individuals. By measuring characteristics, or features, of these immune responses, which we refer to here as "immune-traits", in the context of other variables, we can begin to work out why immune responses vary. We have quantified variation in immune-trait expression under natural conditions and we are working towards establishing the major causes of this variation. We quantified the variation in several compartments of the immune response (innate, adaptive) and to vaccinations in 272 wild mice on the Isle of May over two years (2018 and 2019) and 4 distinct months (September, October, November, December). This is in the context of antigen specific antibody responses, cellular cytokine production and immune cell phenotypes. We have also recorded morphometric data as detailed in the grant proposal including for example age (using an age metric), sex, and infections (species and abundance). During the course of the project we established a collaboration with Dr Frank Chan at the Max Planck Institute, Tubingen to undertake full genomic sequencing by the more affordable method of haplotagging. We thus have the full genome sequence for each of our 272 mice. We used haplotagging instead of genotyping by SNP analysis (as we had originally proposed in the grant) as it adds value to the project. This represents one of the largest datasets from nature on immune phenotypes combined with full genomic sequence. We also assessed the vaccination against an innocuous antigen to assess how age (accumulated life experience) and relatedness of the animals (genetic influence) affected this response.

No strong genetic contributions to variation in immune response have so far been found. Relatedness analysis was performed which can tell how closely related individuals are (parents, siblings, etc) . Unexpectedly, few mice caught in this study were very closely related, and as such, similarity in immunophenotypes within family groups could not be thoroughly explored. and no significant associations between relatedness families and immune state were observed. Genome-wide association studies were performed to look for associations between specific genomic regions and various measures of immunity. There are immune measures showing significant associations with regions of the genome which require further investigation and validation but this is beyond the scope of this project. Work with collaborators has shown that the Isle of May mice have relatively high levels of inbreeding, which may be expected of isolated populations and a comparison of this population to comparable populations from other islands has shown areas of the genome with high levels of differentiation, though the ecological and evolutionary significance of these regions is unclear.

We also assessed in more detail the immune response to Trichuris, a highly prevalent parasitic helminth in this population, and a major health and economic burden in humans, wildlife and livestock. Wild mice harboured predominantly chronic, low-level infections and produced lower levels of cytokines in response to Trichuris antigen compared to laboratory-housed C57BL/6 mice, given either a low dose or high dose infection. The balance between local, mesenteric lymph node Th1 and Th2 immune responses was associated with worm burden (higher Th1 responses) and age (higher Th2 responses). Variability of immune response to Trichuris increased with age. Further, the abundance of effector/memory CD4+ T cells as well as their expression of master transcription factors GATA3 and T-bet reflected the antigen-specific cytokine response. Collectively, the fundamental immunological relationships between the quality of the CD4+ T helper cell response and resistance to T. muris infection described in laboratory mice are also seen in wild M. m. domesticus. However, by exploring immunity to T. muris infection in wild mice living in a natural environment enabled important quantitative differences to emerge and identified age-specific effects reminiscent of those seen in humans infected with soil transmitted helminths. As such, our interdisciplinary, ecoimmunological approach provides an opportunity to tease apart the context-dependent function of the immune system in a natural model system. These findings will be submitted soon as a manuscript to a relevant journal.

In 24 out of 26 measures of immune state, the older contingent of the population showed a higher coefficient of variation between individuals than the younger contingent. This highlights a general higher level of variability in immune function as the mice age, across measures of cytokine expression from different tissues. Variation was on average 3.8 times greater in older mice than in younger mice. This pattern was not however, observed in antibody levels, with the younger contingent showing greater variability in antibody responses to administered KLH vaccinations. This is likely to reflect the variation in exposure to infections when they are young. Younger mice also showed greater variability in their antibodies to naturally occurring Trichuris infections, both in change in levels over time, and in absolute levels at cull.

One published finding is that a particular cell of the immune system, the eosinophil - is far more abundant in wild mice than in laboratory mice and exists in a very active state. This is important as it means that eosinophil functions defined in laboratory-based studies may not fully recapitulate what is seen in a real life context (wild animals, humans) and goes some way towards rationalising why eosinophil function has been so hard to define.

Overall we have accrued considerable data towards exploring our overall aim to examine the genetic and environmental (infections, season, diet) influences on immune responses and we have undertaken work to address our three driving hypotheses. Firstly, we tested if variability in the expression of immune traits among individuals is driven less by heritable than by environmental factors. With our dataset we had no indication that genetic factors were influential in increasing variability although we cannot say they have no influence with a high degree of confidence as more work is required. The second and third hypotheses were that the predominant environmental factor driving variability in expression of immune traits among individuals is infection and that immunological trait variability will increase with age. We have indications that these hypotheses are correct and complex data analyses are ongoing to validate this.
Exploitation Route The programme of work supported by the BBSRC in the project grant has generated a number of new hypotheses, which can be pursued through further grant funding. For example our unexpected observations surrounding the eosinophil provide a novel opportunity to identify eosinophil function in a complex and variable setting. This will be led by the University of Manchester. The breadth and depth of our genetics data will provide a springboard for understanding (immune) gene selection over time. Data generated from our wild house mouse research project will inform other researchers working with different species of wild mammal populations (e.g. Soay sheep, wood mice, voles). As a blue skies project there has so far been no significant impact beyond informing further academic research. However our work is raising awareness within the more pure immunology fields of the importance of context and of understanding immune responses within an ecologically framework. This has been evidenced by team members being invited to speak at international Immunology conferences and the agreement by the Discovery Immunology journal to publishing a special collection focussing on Ecoimmunology curated by two of our team members
Sectors Education,Healthcare

 
Description Responsive mode
Amount £851,457 (GBP)
Funding ID BB/P017827/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 01/2018 
End 12/2021
 
Description Genetic analyses of Isle of May mice 
Organisation Max Planck Society
Department Max Planck Institute for Infection Biology
Country Germany 
Sector Charity/Non Profit 
PI Contribution We have been working with Frank Chan at Max Planck Institute in Tubingen who undertook the full genome sequencing using haplo-tagging techniques
Collaborator Contribution Full genome sequence of 272 mice obtained
Impact Full genome sequence of 272 mice obtained
Start Year 2020
 
Description Microbiome analyses with Cardiff University 
Organisation Cardiff University
Country United Kingdom 
Sector Academic/University 
PI Contribution To maximise outputs and gain of knowledge from the current grant we collected faecal samples from the Isle of May mouse study population.
Collaborator Contribution Working with Sarah Perkins and Sophie Watson at the University of Cardiff we are analysing the Isle of May mouse microbiome for integration in to our larger data sets.
Impact analyses are in progress
Start Year 2021
 
Description Article for the Isle of May Bird Observatory Newsletter (Summer 2022); 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Article for the Isle of May Bird Observatory Newsletter (Summer 2022); Title: 'The early history of Isle of May mouse research'
The purpose was to raise awareness amongst bird watchers about the other research being being conducted on the Isle of May.
Year(s) Of Engagement Activity 2022
 
Description Biological Sciences Review article 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Article for Biological Sciences Review: - 'The shag's dark tale' for Biological Sciences Review which describes the ecology part of our field site on the Isle of May
Year(s) Of Engagement Activity 2021
 
Description Blog feature 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact There is a regular Blog on the Isle of May and our work has featured in these
Year(s) Of Engagement Activity 2018
URL https://isleofmaynnr.wordpress.com/2018/05/18/may-mice/
 
Description From man to Mouse 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Linnean Society Irene Manton Lecture Irene -Manchester 5/12/2019. Public lecture to ~200 people. Increased awareness of Women in Science and contribution of basic research in infectious diseases. Other invitations to speak have arisen
Year(s) Of Engagement Activity 2019
 
Description How parasites have evolved with thier hosts 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Invited speaker in the "grand hall" series at Scarisbrick school where children from the region were invited. I talked about my Career in Science and on how pareasites influence immune responses
Year(s) Of Engagement Activity 2020
 
Description Interview with BBC radio Scotland 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Media (as a channel to the public)
Results and Impact The PI Jan Bradley was interviewed for BBC Radio Scotland on the work we are undertaking on The Isle of May
Year(s) Of Engagement Activity 2018
 
Description Poster exhibit in the visitor centre on the Isle of May: "Ecoimmunology Research on the Isle of May" 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact We have created an island exhibit entitled 'Ecoimmunology Research on the Isle of May'
This is in thr form of a poster exhibit in the visitor centre on the Isle of May, reaching >10,000 tourists a year.
Year(s) Of Engagement Activity 2019,2020
 
Description What is Ecoimmunology 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Article in Biological Sciences Review (Feb 2021 issue)
Year(s) Of Engagement Activity 2021
 
Description school visit 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Talk to a local school on the hygiene hypothesis
Year(s) Of Engagement Activity 2022