Prof Matthew Brown

We are grateful to the Australian Rheumatology Association and the Estate of the Late Marion Alice Simpson for support of our project “.

The immune system protects us from harmful infections and tumours but, in some instances, also attacks healthy tissues in our own bodies resulting in autoimmune diseases. Ankylosing spondylitis (AS) is one such disease. It is a chronic inflammatory disorder that mainly affects the spine and pelvis. It is a severely disabling disease that normally first presents in the second decade of life. There is no cure for AS but powerful anti-inflammatory drugs relieve some of the symptoms of disease telling us that inflammation is an important part of the disease process. AS is an inherited disease and our group has led large genetic studies in the last decade to define genes that increase the likelihood of developing AS. We have now discovered over one hundred of these so called AS-associated genes, many of which are involved in control of the immune system. Our ongoing research program aims to understand how these change functions of immune system in AS patients. Our ultimate goal is to identify specific parts of the immune response in AS patients that may be useful targets for novel drug development.

Our studies have shown that a protein called T-bet plays an important role in the immune system of AS patients and contributes to some of the inflammation seen in patients. In mouse models of AS, mice that lack the T-bet gene do not develop disease. T-bet is a protein that is capable of controlling many different types of immune responses. Of importance to AS, one of the immune responses it controls involves one of the critical proteins in AS inflammation, IL-17. Immune cells in AS patients make a lot more IL-17 than immune cells in healthy people. In turn, this increased amount of IL-17 plays a big part in the inflammation and subsequent pain experienced by AS patients. In clinical trials, patients who receive drugs that block the effects of IL-17 have their inflammation significantly reduced and experience reduced levels of pain. Since T-bet plays an important part in controlling how much IL-17 is made by immune cells understanding more about T-bet in AS patients provides an opportunity to know more about the immunological basis disease and may highlight new drug targets.

T-bet controls the function of other genes by directly attaching to parts of those genes. A lot is known about what genes T-bet controls in mice and mouse models of disease but very little is known about its function in humans. Almost nothing is known about its function in human diseases. The goal of our studies was to determine precisely what aspects of the immune response T-bet controls in AS patients. We planned to do this in two ways: (i) by purifying T-bet from cells and studying what genes were attached to T-bet which would give us a precise list of genes that T-bet controls in humans; (ii) by studying in detail the function of immune cells in which T-bet is found compared with cells in which there is little or no T-bet.

This was a challenging and ambitious project and we have had to develop new methods to purify T-bet from cells. This method development has taken considerable effort and time. As of July 2018 we are very close to finalising the method development and will be able to study T-bet in great detail before the end of 2018. Analysis of cells is part of a larger study and has also taken considerable time to complete. The challenge here has been recruitment of patients and healthy controls that carry the necessary set of genes (known as a genotype). This has taken longer than anticipated because finding healthy controls carrying the main AS-associated genes has required recruiting and screening a large number of people. In this regard we have collaborated widely to access biobanks and blood collections in order to expedite our recruitment.

 This work is ongoing and remains a priority within our group. To date, we have developed methods for reliable isolation of T-bet (and attached genes) from human immune cells called CD8 T cells and NK cells. While methods for T-bet isolation have been described in the scientific literature none of these worked reliably for CD8 T cells or NK cells. The methods we have now optimised work reliably and reproducibly. Furthermore, we have generated the raw materials to perform next-generation sequencing on CD8 T cells and NK cells from AS patients and healthy controls and will commence sequencing these samples before the end of 2018.

The real strength of our study will be realised towards the end of 2018 as we perform ‘next generation sequencing’ of T-bet associated genes and of the immune cell subsets in which T-bet is found. This sequencing effort will generate very large and complex datasets that will be require specialist analysis. We have in house experts in this type of analysis ready to go once the data is generated. At a simple level we will be able to define what genes T-bet controls and how T-bet changes the function of particular immune cells. However, based on our experiences with similar projects the datasets generated will provide new and important knowledge for many years as our ways of interrogating the data becomes more refined and sophisticated.

No, but the long term potential of the data we are generating is great. We are producing very large datasets containing a lot of complex data that will be analysed for many years to come. This dataset will be a rich resource for our lab in the first instance but will also be made publicly available to the wider AS research community in time and will therefore provide a resource beyond the scope of our own studies.

In mouse models of AS we have demonstrated that deletion of the T-bet gene prevents disease developing. Such as strategy is not possible in humans but by defining what genes T-bet controls in AS we have the opportunity to identify new drug targets in the future. The large datasets we are generating will inform basic knowledge of T-bet function in human immune cells. This is fundamental science and will lead to new knowledge of immune function.

Yes, this research is ongoing and a very important focus of our group currently. The data generated from this study will be thoroughly interrogated for many years by us and the wider research community.