The role of interleukin-10 (IL-10) in the regulation of innate immunity in the domestic chicken

Our research is focused on breeding birds that are intrinsically resistant or resilient in the face of infectious disease, to reduce the dependence upon antibiotics and other treatments in poultry production. Enhanced resistance or resilience can also improve chicken welfare in the face of environmental pathogen challenge. We are studying a circulating hormone-like molecule, called interleukin-10 (IL-10) that is produced in large amounts when a bird is infected with a parasite, Eimeria, which is a major cause of loss and suffering in both broiler and layer poultry production. Our hypothesis is that the level of IL-10 produced is under genetic control, and that this protein suppresses the immune system so that birds become susceptible to other pathogens as well, including Campylobacter and Clostridia that are also potentially transmitted to humans. To address our hypothesis, we will challenge broiler and layer birds with the parasites, and measure levels of IL-10 in the circulation, see whether they are correlated with the severity of the disease in the intestine and the impact on the growth and productivity of the birds. In these challenge studies, we will dissect the relationship between the genetics of the bird and the level of IL-10 they produce. We will also determine whether the severity of the disease caused by parasites is controlled directly by IL-10 by deliberately reducing the level, either using an antibody that blocks its actions, or genetic manipulations that abolish the production.

The challenge to the poultry industry in selective breeding for natural resistance is to identify quantitative markers that identify individuals with superior performance in the presence of infection. Our current BBSRC ARC funded work has revealed that circulating IL-10 could provide a biomarker to identify birds that are resilient when challenged with Eimeria spp. In this study we will explore the genetic control of IL-10 production, and the consequences of selection for low IL-10 production. We will assay circulating IL-10 in the response of large cohorts of commercial broiler and layer birds to Eimeria challenge, alone or in combination with other enteric pathogens (e.g. Campylobacter jejuni, Clostridium perfringens), and apply genome-wide association (GWA) using high density SNP chips and/or whole genome resequencing to identify cis and trans-acting variants that control circulating IL-10 and other indices of the response to challenge. To test the direct role of IL-10, we will breed variant IL-10 alleles to homozygosity, produce IL-10 knockouts by gene-editing, and examine the effect of neutralising IL-10 antibodies on the response to infection.

Sustainability of the UK and international poultry industries face numerous challenges including pathogen resistance to control and withdrawal of prophylactic/therapeutic antibiotics in an attempt to tighten biosecurity of food destined for human consumption. Our project seeks to provide an intellectual foundation, and possible tools, toward efforts to breed lines of genetically disease resistant and resilient birds. These will include a better understanding of host-pathogen interactions vital to the investigation of new and effective measures of disease control and determination of the implications of selecting for specific traits using newly identified biomarkers to ensure economic goals and animal welfare are not compromised. Outcomes will assist in increasing competitiveness in international markets for the supply of safe, healthy and comparatively cheap food to an ever-increasing world population.

1. The poultry production industry
Eimeria spp, (cause of coccidiosis), cost the international poultry industry approximately $3.5bn (£800M in the UK) per annum, chiefly through loss in production and the cost of prophylaxis. Clostridium perfringens can cause necrotic enteritis (in coinfection with Eimeria). Campylobacter jejuni is the leading cause of foodborne enteritis in the developed world, with poultry products a major source. Addressing 'animal health and welfare, and genetics and genomics for improved production and disease resistance', the work proposed is directly relevant to BBSRC's Strategic Research Priority 1.

2. The UK poultry breeding industry
The structure of the UK poultry industry is such that collaboration with the major breeding companies will provide a cascade of breeding developments, 'ensuring exchange of knowledge between the science base and industry through effective networking'. Understanding the relevance of IL-10 to enteric disease, and thus productivity and welfare, of chickens can provide a major new biomarker to inform breeding strategies.

3. The UK animal health industry
Understanding the impact of IL-10, and the consequences of Eimeria infection, on immune responses to enteric pathogens and vaccination can impact on current and future vaccine application ('Understanding variation in vaccine responsiveness, immuno-competence at different developmental stages and disease outcomes').

4. Animal welfare
The effective reduction of disease as a result of improved breeding supports the Five Freedoms implicit to animal welfare as set out by the Farm Animal Welfare Council.

5. General public and the environment
Increased efficiency in poultry production will raise poultry product availability at a lower cost for the consumer, contributing to improved food security. Consequences of improved disease resistance include a reduction in the requirement for prophylactic chemotherapy, reducing drug consumption and the risk of contamination to the food chain and the environment. While Eimeria is not transferrable to humans, in 2004, Campylobacter jejuni and Clostridium perfringens (together with Salmonella spp) were responsible for in excess of 350,000 reported cases of food poisoning in the UK.

6. Skills, knowledge and training
The multidisciplinary nature of this project will provide opportunities for broad training to all staff, in addition to other members and students of each host institution ('strengthen the research community in the areas of disease and pest resistance of farmed animals through interdisciplinary research and the provision of training'). Access to IL-10 deficient and knockout birds will be a major international resource through NARF.

7. International development
Eimerian parasites impose serious costs on animal production in developing counties. Translating 'high quality, innovative, strategic research within UK universities and institutes to improve the resistance of farmed animals to pest and disease organisms' can improve economic income and alleviate poverty.