Immunity safety and protection of an Adenovirus-Prime:MVA-Boost vaccine against Mycobacterium avium subspecies paratuberculosis infection in calves

Mycobacterium avium subspecies paratuberculosis (MAP) is the bacterium that causes a chronic inflammation of the gut known as Johne's disease (JD) in many animals. JD is of significant economic importance to the management of cattle, sheep and goats due to loss in milk production and the need for premature culling when the disease becomes advanced; the cost has been estimated to be $1.5billion pa. in the USA and £13million pa. in the UK. Current measures to control the spread of JD have been shown to be inadequate and at present more than half of cattle herds in the UK are infected and nearly all herds in some other developed countries, including the USA. MAP is excreted in very large amounts in later stages of infection but can also be excreted even when current vaccines are used. This has led to the spread of MAP into wildlife reservoirs and contamination of environmental reservoirs such as rivers and lakes. MAP is excreted by infected dairy cattle in their milk and is present in supermarket milk as it survives pasteurization. There is an increasingly convincing link between MAP infection and Crohn's disease in humans, MAP has been detected in up to half of normal human intestinal samples and nearly all of Crohn's Disease samples. Currently, commercially available whole cell vaccines do not provide complete protection against JD. They may relieve clinical symptoms but do not significantly reduce the number of animals that are infected or stop excretion of MAP into milk and faeces. By allowing the induction of sub-clinical infection, these vaccines may hide the problem of MAP infection and consequently be counterproductive. Therefore, there is an urgent need to develop a better vaccine to treat this disease and to understand the way that MAP affects the animal's immune system to cause JD. This project will study a new type of vaccine that has been shown to work in mice. It uses two viruses that will not grow in animals or the environment, to deliver a cocktail of MAP antigens called HAV. Although vaccination trials in mice do not always transfer successfully to other animal species, results from preliminary experiments have shown that the prime-boost vaccination method we are proposing to use has been beneficial in conferring a degree of protection against other mycobacterial infections. We will look at the ability of the HAV vaccine to prevent an experimental infection of calves with MAP and measure in detail the cattle's immune system with the aim of understanding how this new type of vaccine might be working. This work will improve our knowledge of mycobacterial disease processes and could therefore also benefit other related research such as vaccines for tuberculosis for example. If the study does show that the new vaccine may be protective it could be a first step in improving the control of this increasingly spreading disease.

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne's disease (JD) in many animals and is of significant economic importance to the management of cattle, sheep and goats. Current control measures are inadequate and prevalence in dairy herds has increased to 57% in the UK. MAP is excreted in milk and survives pasteurisation and is spread to wildlife and environmental reservoirs from faeces. MAP has recently been detected in up to 47% of normal human intestinal samples and 90% of Crohn's Disease samples. There is mounting evidence of a link between MAP infection and Crohn's disease in humans, which places MAP as a possible zoonotic agent. Previous MAP vaccines have been shown to have some efficacy in decreasing clinical disease in animals but do not significantly reduce herd prevalence or excretion and interfere with the current diagnostic test for bovine tuberculosis. We have recently shown that priming with non-replicative Adenovirus 5 followed by boosting with Modified Vaccinia Ankara expressing intracellular phase MAP antigens confers protection against MA in mice. In this work we will test the hypothesis that a prime boost vaccination strategy focusing the response to defined intracellular MAP antigens, HAV, will provide protection from subsequent MAP challenge in calves and eliminate cross reactivity with tuberculin testing. We will determine immunological profiles arising as a consequence of MAP challenge after vaccination or sham vaccination of calves with HAV vaccine and analyse these for possible correlates of protection against MAP. Besides the inherent possibility of providing a vaccine that may contribute to the control of JD, findings from this project will contribute to a our understanding of immune responses elicited by prime boost vaccination strategies in cattle and inform on the development of vaccines against other mycobacterial diseases, such as tuberculosis.

This project will impact in the short term as a proof of principle study with high profile interest to the academic paratuberculosis research community and benefiting the BBSRC by fulfilling BBSRC Strategic Objective 1 and BBSRC calls for co-ordination of sustainable agricultural research within the UK by using innovative tools. The potential for a successful development of a novel vaccination strategy however would further provide benefit for workers and policy holders involved in animal disease prevention, sustainable agriculture and potentially the public health sector with considerable commercial potential both in the UK and worldwide. The work will benefit DEFRA animal health and welfare strategy in its commitment to reduce the spread of Johne's Disease (JD) with the aims of raising beef and milk production efficiency and bring benefit to the export of cattle. Development of an effective vaccination strategy would provide economic benefit to farmers and the dairy industry by improving animal welfare, decreasing animal loss, increasing milk yields and promoting confidence in food safety. Current vaccine preparations are ineffective in controlling JD and cannot be used in the UK because of interference with bovine tuberculosis testing and this proposal could overcome these difficulties. High prevalence of MAP in cattle herds and co-infection of MAP and bovine tuberculosis with significantly lower responses in the bovine Tuberculin test suggest that MAP infection is influencing the already problematic control programme or bovine tuberculosis. Expensive test and cull strategies would result in the destruction of large numbers of infected animals and need to be sustained over many years. This project therefore has the potential for substantial benefit to governmental and private stakeholders involved in both JD and bovine TB disease prevention strategies. MAP dissemination in the environment and dairy products has implications for studies of Crohn's disease (CD) in humans, By investigating correlates of protection in cattle, this project could provide a basis for the development of a vaccine for human use. CD is already linked with a genetic predisposition so the possibility that 'susceptible' disease free relatives of CD patients might be treated prophylaxically with a 'human vaccine' may thus offer potential for future public health and commercial development. More immediately, the known presence of MAP in the food chain has led to calls from public health agencies, such as the UK Food Standards Agency (FSA), for a precautionary principle to be taken to eliminate MAP from human food stuffs and water supplies. This projects directly addresses the FSA long term (5yr plus) recommended action plan to 'develop a better vaccine against MAP for use in cattle' An additional benefit would include the prevention of possible loss-claims to the British milk producing industry from CD patients. The project will provide communication and outreach of relevant discoveries to research and academic stakeholders by oral and poster presentations at scientific meetings, peer reviewed publications and institutional internet webpages. Non-Research and non-academic stakeholders such as farmers, government policy makers, commercial partner opportunities, links to paratuberculosis health awareness groups will also be informed through release of information at International Mycobacterial Disease forums and workshops such as VENOMYC network and Paratuberculosis Colloquia. Public awareness is an important issue, particularly in the respect to links to Crohn's disease. Release of project data will be made accessible to the public through contributions to the PARA organization (http://www.crohns.org/index.htm) which aims to promote dissemination of paratuberculosis research and awareness to the general public through web-based interaction and lobbying for political awareness of public issues concerning paratuberculosis and Crohn's disease.