Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Final Activity Report Summary - GALTRAIN (Exposure to microorganisms and suppression of allergic diseases: A European research training scheme)

The aim of the GALTRAIN project was to train fellows in an array of techniques that allowed the hygiene hypothesis to be investigated. The epidemic of allergies that is being currently experienced in developed countries was hypothesised to be due to decreased exposure to microorganisms resulting in a dysregulated immune system.

This programme had a range of projects investigating the factors influencing the development of allergies in work programmes ranging from in vitro immunology, through investigations on the effects of parasite exposure in humans and animals models on the immune system to the testing and characterisation of substances that might be used for therapies. This was a multi centre project with six principal investigators (PIs) from four different host countries. A total of 19 fellows were trained, eight of which were awarded, or would be presenting shortly after its completion, their work for a PhD. The other 11 had short term fellowships from three months to a year where they were trained in specific techniques. The fellows all benefited enormously from the multi-cultural and multidisciplinary nature of the project with most experiencing a secondment to another laboratory.

One of the most important early findings in support of the hygiene hypothesis was that individuals from farming communities in rural Germany were protected from the development of allergies. Several of the projects were focussed on further investigating this observation. Two fellows were trained in the Galtrain project at Ludwig Maximilian University Munich (LMU). The focus for these two fellows was on the planning, conduct and analysis of epidemiological data obtained as part of very large epidemiological studies funded by the European Union such as GABRIEL and PAULA with a particular focus on environmental microbial exposures. Based on these epidemiological studies it was proved that cowshed environments were allergy-protective, thus a number of fellows were trained at the Research Centre Borstel to process extracts obtained with physiological saline from dusts of cowsheds and sheep-sheds, as a negative control, and of straw. The compositions of all extracts were characterised and it was shown that they contained a variety of sugars, and also protein, however in different amounts. These extracts were found to be as allergy protective in an animal model. A variety of polysaccharides were identified in the shed extracts, mostly originating from plant material, as proven by the composition of the straw extract which was planned to be investigated with respect to their allergy protective potential.

Several other projects focussed on mycobacterium vaccae, a harmless environmental microorganism common in mud and untreated water that was found to exert a beneficial regulatory effect on the immune system. In experimental animals m. vaccae decreased the type of immune response (Th2) that mediated allergic disorders such as asthma and atopy, probably by inducing a type of T cell that was regulatory (Treg) without downregulating the type of response (Th1) that protected against tuberculosis and most cancers. Indeed there was evidence that it was beneficial in the latter conditions and the results of a large phase III clinical trial in human immunodeficiency virus positive (HIV+) Tanzanians were published recently and confirmed that even in HIV+ individuals m. vaccae provided significant protection against tuberculosis (TB). M. vaccae was tested in clinical trials in at least 2 000 people with no reports of toxicity or detrimental side effects. By the time of the project completion m. vaccae was being re-manufactured to good manufacturing practice standard (GMP) by Aeras for clinical trials in TB and by Immodulon, for clinical trials in other disorders, including cancer. It was likely that it might also be used as a therapeutic agent for allergies. In a project at University College London (UCL) m. vaccae was shown to trigger to induce regulatory T cells in vitro which was compatible with previous animal work showing that m. vaccae downregulated allergic responses in mice via a mechanism that involved these cells. These studies were then extended to elucidate mechanisms whereby m. vaccae mediated these effects. Microarray analyses of m. Vaccae treated innate cells (DC) that were important in defining the type of T cell induced (Th1/Th2/Treg) revealed that the pattern of gene expression in m. vaccae-treated DC was quite different from that induced by other factors which triggered cells to make Th1 responses.

Bioinformatic analysis of this data led to the identification of a transcription factor, CREB1 as a key component of m. vaccae specific effects on DC. Further study of the CREB pathway in this model might provide novel insights into the molecular mechanisms of DC dependent T cell polarisation and increase our understanding of an agent that was rapidly entering human clinical studies. Investigations at Southampton (UoS) and LMU were also focussed on the role of DC and T cells as key players in initiating and driving immune responses allergic inflammation. Tregs had a pivotal role in suppressing Th2 responses against allergens but this was shown to be defective in blood of allergic individuals. One investigation aimed specifically to look at airway cells and another focussed on immune responses of the neonates as it might be that environmental factors influenced the development of the immune system at a very early age which was critical in inducing the regulatory networks required to protect against the development of allergies. It was likely that m. vaccae and other microbes might act via Tregs and DCs to regulate the way the immune system responds to aero-allergens.

An important finding was that differences in the phenotype of these cells were found in the airways of healthy and asthmatic individuals with their being an enrichment in the lungs of healthy individuals. M. vaccae was shown to potently inhibit ex vivo IL-5 and IL-13 cytokine production which was associated with Th2 responses and allergy. This immunomodulatory effect was independent of IL-10 and TGF cytokines which were produced by Tregs, although it was shown to induce a certain type of Tregs suggesting that the inhibitory effect on Th2 cells might be mediated by a non cytokine effect. Consistent with this was the observation that that Th2 cytokine production inversely depended on the potency of Treg induction. There were strong epidemiological data showing that allergies were less prevalent in developing countries and several studies indicated that there was a negative association between helminth infections and allergic disorders.

An aim of the GALTRAIN project was to understand the modulatory effects of helminths and molecules produced by them. In a birth cohort study in Indonesia, where children were exposed to helminth infection, the characteristics of a developing immune system were studied up to the age of four years in collaboration with Leiden University (LUMC). As most birth cohorts were conducted in high income countries where infection pressure was relatively low, the study provided unique insight into how the early immune system might be developing in areas where exposure to infections was high not only during infancy but even in utero. Similar studies from LUMC focussed on defining the mechanisms that might be involved in protecting helminth infected individuals from allergies and the existence of both B and T regulatory cells were increased in relation to helminth infection. Studies on human populations were beset with ethical and logistic problems so the University of Nottingham (UON) took the approach of investigating the immune responses of naturally infected wild rodents with the aim of examining the relationship of regulatory responses with parasitic infections. As with the human studies, regulatory responses were strongly associated with helminth infection but an unexpected observation highlighted ectoparasites, in particular blood feeding lice, as a novel factor in inducing such responses.

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United Kingdom