Effect of immunosuppression associated with point-of-lay on Salmonella infection and immunity in laying hens
Lead Research Organisation:
University of Liverpool
Department Name: Veterinary Pathology
Abstract
Salmonella enterica is one of main causes of bacterial food poisoning in the world. One type of Salmonella called Salmonella Enteritidis has the ability to infect the eggs of chickens that are infected with Salmonella bacteria. If infected eggs are eaten raw or poorly cooked, there is a chance that the person may become ill. In most cases this results in diarrheoa and a short term illness but in young children, the elderly or people with immune systems that do not work well, Salmonella infection can be very serious. In some case it may result in death. In recent years vaccination has been used as part of the control of Salmonella in chickens. However just before hens begin laying eggs (point-of-lay), their immune system becomes suppressed or less effective. This may mean that even vaccinated chickens are more likely to catch a Salmonella infection at this point. This research will find out which parts of the immune system do not work well at the point-of lay. We will then test Salmonella vaccines and measure how well they stimulate the immune system at point-of-lay and whether these vaccinated birds are more likely to get Salmonella at this time.The research will allow us to improve how and when we vaccinate chickens against Salmonella so they are protected when they start to lay eggs. It will also help us make better vaccines that protect chickens better and for longer than current vaccines.
Technical Summary
The project will investigate the mechanisms that underlie the observed suppression of adaptive, and in particular cell mediated immunity at the onset of sexual maturity of laying hens and the effect these changes have on immunity to Salmonella enterica serovar Enteritidis. Salmonella Enteritidis may be transmitted vertically through eggs and thereby poses a risk to public health through the consumption of poorly cooked contaminated eggs. Although vaccination is employed in the UK in the control of Salmonella in laying hens, the immune mechanisms that underpin protection are not known. It is also unclear whether there is a gap in immunity at point-of-lay in vaccinated animals that may compromise protection to salmonellosis. The first aim of the project is to characterise changes in the immune system in developing hens. Flow cytometry will be used to determine the levels of T and B lymphocytes in the spleens of hens. Further characterisation of CD4 and CD8 positive, along with T cell receptor type (TCR1, 2 or 3)will also be performed. Immunocytochemical staining will be performed on tissues, including the oviduct and ovaries which are the main sites of Salmonella infection. Whilst these assays will indicate changes in cell numbers and population distributions, analysis of T cell function will be determined by proliferation to stimulation with the mitogens ConA and PHA. Immunoglobulin levels will be determined by ELISA. In a second series of experiments, we will characterise the immune response to Salmonella infection and to vaccination with currently available live and killed vaccines. Cellular changes will be determined as outlined above. T cell proliferation to Salmonella antigens will be determined and specific antibody responses to Salmonella (IgM, IgG and IgA) determined by ELISA. Expression of key cytokines, IL-2, Il-4, IL-10, IL-12 and interferon-gamma will be performed on tissues by qRT-PCR. The use of magnetic cell sorting will be done to obtain specific cell populations. The expreession profile of these cells will also be determined by qRT-PCR to allow a more detailed analysis of the cell types involved in initiating and maintaining the immune response. These studies will also allow us to determine the relative role of Th1/Th2/Treg cells in the immune response. On the basis of the findings of the first two groups of experiments, we will conduct oral challenge experments to determine whether any reduction or gap in immunity in vaccinated birds around point-of-lay makes the chickens more susceptible to infection than in vaccinated birds prior to lay, or in birds where egg laying is well established. This will be assesed by qunatitative bacteriology of caecal contents, spleen, liver, oviduct, ovaries and developing or laid eggs. The final part of the project will determine whether changes in vaccine strategy can be employed that lead to more effective protection. We will determine whether non-specific stimulation of the immune system just prior to the onset of lay may be utilised to boost protection. We intend to achieve this through DNA vaccination of a plasmid vector containing the chicken interferon gene under control of an appropriate promoter, including immunostimulatory CpG motifs in the plasmid backbone. This should stimulate a Th1 dominated response and stimulate cell-mediated immunity. It is hoped such stimulation may be sufficent to increase protection to Salmonella, and potentially other pathogens, through the start of the egg laying period and reducing the risk of transmission of Salmonella to eggs.
People |
ORCID iD |
Paul Wigley (Principal Investigator) |
Publications
Wigley P
(2014)
Salmonella enterica in the Chicken: How it has Helped Our Understanding of Immunology in a Non-Biomedical Model Species.
in Frontiers in immunology
Wigley P
(2013)
Immunity to bacterial infection in the chicken.
in Developmental and comparative immunology
Langridge GC
(2015)
Patterns of genome evolution that have accompanied host adaptation in Salmonella.
in Proceedings of the National Academy of Sciences of the United States of America
Johnston C
(2009)
Cellular and functional changes in the reproductive tract associated with onset-of-lay in chickens
in Veterinary Immunology and Immunopathology
Hartley C
(2012)
CpG oligonucleotides and recombinant interferon-? in combination improve protection in chickens to Salmonella enterica serovar Enteritidis challenge as an adjuvant component, but have no effect in reducing Salmonella carriage in infected chickens.
in Avian pathology : journal of the W.V.P.A
Chappell L
(2009)
The immunobiology of avian systemic salmonellosis.
in Veterinary immunology and immunopathology
Description | Through this work we found: 1. Immunosuppression in laying hens is due to a drop in CD4 lymphocytes 2. There is an organised lymphocytic structure in the reproductive tract that changes over development 3. Birds show increased susceptibility to salmonellosis due to immunosuppression 4. Vaccine protection is significantly reduced due to immunosuppression 5. Adjuvants that drive cellular responses increase protection to salmonellosis |
Exploitation Route | 1. Understanding the nature of immunosuppression means that control strategies in egg production can be developed that take this into account either through biosecurity and/or modification of vaccination strategies 2. We have shown proof-of -principle that vaccines adjuvants can be used to modulate an appropriate vaccine response in the chicken |
Sectors | Agriculture Food and Drink Pharmaceuticals and Medical Biotechnology |
Description | Maintenance/enhancement of high biosecurity through point-of-lay in egg production Development of the laying hen as an infection model for invasive salmonellosis |
First Year Of Impact | 2011 |
Sector | Agriculture, Food and Drink,Pharmaceuticals and Medical Biotechnology |
Impact Types | Economic |
Description | Rapid diagnostics and control strategies for enteric bacterial pathogens in backyard and commercial poultry production in Thailand and the Philippines |
Amount | £916,765 (GBP) |
Funding ID | BB/R013136/1 |
Organisation | Biotechnology and Biological Sciences Research Council (BBSRC) |
Sector | Public |
Country | United Kingdom |
Start | 03/2018 |
End | 03/2021 |
Title | Avian Infection Models |
Description | Development and refinement of novel infection models to study infection, co-infection and transmission by food borne bacterial pathogens |
Type Of Material | Model of mechanisms or symptoms - non-mammalian in vivo |
Year Produced | 2013 |
Provided To Others? | Yes |
Impact | Publications and directly funded industrial research |
Description | Poultry Disease Group |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Contribution to Poultry Disease Group Forum through presentations and discussion. Excellent forum to link academia, industry and policymakers Frequent requests for information, links to industry |
Year(s) Of Engagement Activity | 2010,2011,2012,2013 |
Description | Presentation to CEVA Animal health |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Industry/Business |
Results and Impact | Meeting/visit to CEVA in Bordeaux to discuss development of poultry vaccines with their international poultry committee. This has become recurring activity with presentations made twice in 2016 and further made for July 2017 |
Year(s) Of Engagement Activity | 2015,2016 |
Description | Presentation to MSD Animal health |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | Good discussion with regard to future potential collaboration Sharing of information on immune response to Salmonella |
Year(s) Of Engagement Activity | 2012 |
Description | Primary School Toxteth |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | Excited children in the general area of science Gave exposure to biological science to children from underprivileged inner city area. Main impact was stimulating an awareness in natural science |
Year(s) Of Engagement Activity | 2010 |
Description | School Visit-Neston |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | Primary school visit explaining about animals using bones in a demonstration. Was enjoyed by children who understood more about the biology of current and extinct animal species None yet |
Year(s) Of Engagement Activity | 2014,2015,2016 |
Description | Talks on infectious disease to 6th form and parents & talk to 5th and 6th form on use of animals in science |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | General discussion afterwards. Specific interest from some individuals Students undertaking work experience in lab. Applications to our degree programmes |
Year(s) Of Engagement Activity | 2007,2009,2010 |
Description | Thai Poultry Industry Meeting |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Many questions but limited time Questions on what future contra strategies may be |
Year(s) Of Engagement Activity | 2013 |
Description | Workshop and visits to Corpoica, Pollo Fiesta, Colombian NIH and Biotech Institutes in Bogota, Colombia on foodborne pathogens and food safety |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | The key objective of our visit was to understand the structure and challenges faced by the Colombian poultry industry in controlling the foodborne pathogens, Campylobacter and Salmonella, and to disseminate our findings and the approaches that we have taken within the UK and ultimately to explore translation of work to improving food safety in Colombia. This was facilitated through meetings with academics and the poultry industry, as well as visiting poultry farms and slaughterhouses, which provoked discussion around biosecurity on the farms and how this could be improved as well as interventions within the slaughterhouse. These included the production company Pollo Fiesta, researchers from Corpoica, Universities and the National Institute for Health. Alex Royden a BBSRC DTP PhD student also spent time at Corpoica and helped train staff in some of our isolation procedures developed here which helped overcome some of the issues they had with contamination when trying to isolate Campylobacter. |
Year(s) Of Engagement Activity | 2017 |
Description | Workshops on Campylobacter and Salmonella Bangkok and Pattaya, Thailand |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | Workshops promoted discussion and development of Thai research programme Visiting Thai students |
Year(s) Of Engagement Activity | 2012,2013 |