Studying the Earliest Stages of Autoimmunity to Determine What Goes Wrong

Alasdair Coles, M.D.

The University of Cambridge

Funded in June, 2004: $300000 for 3 years
LAY SUMMARY . ABSTRACT . BIOGRAPHY . HYPOTHESIS . FINDINGS . SELECTED PUBLICATIONS .

LAY SUMMARY

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Studying the Earliest Stages of Autoimmunity to Determine What Goes Wrong

This study will examine the earliest stages of autoimmunity, when the body's immune system first mistakes the body's own tissues as foreign and attacks them. The results may provide new insight into how immune cells malfunction in autoimmunity, using autoimmune thyroid disease as the "naturally occurring" experimental model.

Naturally occurring studies examine what happens as an event occurs. In this case, the event concerns patients with autoimmune multiple sclerosis (MS) who were participating in a clinical trial (supported by other funders) of a therapy that depletes immune cells. The investigators considered immunosuppressive therapy to be a potentially effective means to reduce the immune cells' mistaken attack against the fatty sheath, called myelin, that insulates brain and spinal cord cells and facilitates transmission of signals from one cell to another. The experimental therapy showed some positive effects in reducing immune attacks against myelin, especially when given early in the course of the disease. This prompted the investigators to test the immunosuppressive treatment in newly diagnosed MS patients.

After a year of treatment, however, the investigators found that one-third of the clinical trial patients developed a new autoimmune disease of the thyroid called Graves disease. Medication easily controls this autoimmune hyperthyroid condition, and newly diagnosed MS patients continue to elect to enroll in clinical trial of immunosuppressive treatment for MS, with full knowledge that they may develop treatable Graves disease.

With Dana support, the Cambridge researchers now will study consenting MS patients who have been participating in the MS clinical trial for less than a year. The study will include 50 patients receiving the experimental MS treatment, and 10 patients not receiving this experimental treatment. The investigators will study the patients' immune system actions and follow the patients. Based on the researchers' prior findings, an estimated one-third of the patients will subsequently develop Graves disease in a year. The investigators will determine, in those patients who develop Graves disease, whether there were any differences in the functioning of their immune systems compared to those who do not develop Grave's disease.

The researchers suspect that in autoimmune MS there is a genetically determined acceleration in the turnover of immune T cells. Similarly, in MS immunosuppressive therapy, there is a depletion of T cells followed by an accelerated turnover and generation of new T cells. There are several types of T cells. One type, called a "memory" T cell learns to identify an invader, remember it, and attack it when it is encountered. Another type of T cell is a "regulatory" T cell. These keep the memory T cells in check. The researchers hypothesize that far more memory T cells compared to regulatory T cells are produced during the frequent turnovers of T cells. A percentage of these "memory" T cells, however, incorrectly learn or fail to correctly remember the identity of an invader. As more memory T cells are produced, this increases the probability that a great number of the memory T cells will have this problem, and misidentify the body's own cells as invaders and attack them.

The investigators hypothesize that this is why a substantial number of MS patients undergoing immunosuppressive therapy develop autoimmune thyroid disease. Many of the memory T cells mistake thyroid tissue as foreign. In untreated MS patients, the same genetically-driven overproduction of memory T cells may occur, with some of the memory T cells mistakenly attacking myelin.

This excessive imbalance between memory and regulatory T cells, the researchers hypothesize, occurs in people who have a defect in the genes that promote T cell expansion. This genetic defect, they postulate, puts those who have it at greater risk of developing one of the many types of autoimmune diseases that exist. By studying the immune system before and during the onset of autoimmune thyroid disease, the investigators will try to determine if these hypotheses are correct.

ABSTRACT

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Studying the Earliest Stages of Autoimmunity to Determine What Goes Wrong

Multiple sclerosis is the leading cause of disability amongst young adults. Its cause is poorly understood, although it is widely accepted to be an autoimmune disease, and its treatment remains unsatisfactory.

From 1991 to 2002, we treated 58 patients with multiple sclerosis using the humanised monoclonal antibody, Campath-1H, which causes prolonged T lymphocyte depletion. Clinical and surrogate markers of inflammation were suppressed (Coles et al. 1999a). MRI scans on patients with secondary progressive disease showed no new lesion formation after seven years. In both the relapsing-remitting and secondary progressive stages of the illness, Campath-1H also reduced relapse rate (from 2.2 to 0.14 and from 0.7 to 0.02 respectively; both p < 0.001). Patients with relapsing-remitting, but not those with secondary progressive, multiple sclerosis showed a stabilisation or improvement in disability. We hypothesis that immunosuppressive treatment will only be effective if given early in the disease course and this idea is being tested in an international trial comparing Campath-1H and IFN-β in the treatment of 300 drug-nave patients with early, active relapsing-remitting multiple sclerosis.

An unexpected adverse effect of Campath-1H treatment of multiple sclerosis is the emergence, at roughly 12 months after treatment, of Graves' disease (autoimmune hyperthyroidism) in one third of patients (Coles et al. 1999b). Whilst Graves' disease is relatively easy to treat, its predictable appearance in this context provides a unique opportunity to study the earliest stages of human autoimmunity; for which the CAMMS223 trial provides ready serial patient samples.

In preliminary experiments, we have shown that untreated patients with multiple sclerosis have an increased lymphocyte turnover, even when unstimulated, using CFSE assays in PBMC cultures ex vivo. After T cell depletion with a single dose of Campath-1H it take years to repopulate the lymphocyte pool. This is associated with a rise in serum IL-7 which is the main promoter of lymphocyte proliferation besides TCR engagement. In these patients (but not in PBMC cultures depleted of T cells in vitro), lymphocyte subpopulations are differentially affected. Memory T cells are relatively over expressed in the depleted T cell pool after Campath-1H and pose a potential threat for autoimmunity. Initially their proliferation is reduced by an excess of regulatory (CD4+CD25hiFoxP3pos) T lymphocytes. However by 12 months, the proportion of regulatory T cells amongst the regenerated T cells returns to normal. It is at this time, with a lymphocyte pool enriched for autoreactive T cells but reduced regulation, that patients are at risk of autoimmunity.

Results from this study may inform mechanisms underlying autoimmunity in general.

INVESTIGATOR BIOGRAPHIES

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Alasdair Coles, M.D.

Dr. Alasdair Coles works as a neurologist and immunologist in the Department of Clinical Neuroscience in the University of Cambridge, UK. His medical degree is from the University of Oxford, and he did further training in Nottingham and at the National Hospital of Neurology & Neurosurgery at Queen Square, London. His Ph.D. is from Cambridge and concerned the immunological effects of treatment of multiple sclerosis using an experimental drug, Campath-1H. As well as organizing a multi-center trial of this drug in MS, he leads a research group focused on understanding the faults in the immune system of people with multiple sclerosis and how these might be combated with new therapies.

HYPOTHESIS

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The study hypotheses are that autoimmunity seen after Campath-1H depletion of T cells is due to homeostatic lymphocyte expansion and that, in untreated people with multiple sclerosis, a similar mechanism may cause an inappropriate drive to T cell proliferation and hence autoimmunity. The research approach is to systematically study lymphocyte subpopulations in people with multiple sclerosis, either untreated or after Campath-1H treatment. Within each subpopulation, candidate genes known to promote T cell expansion (especially IL-7, by real-time PCR) will be sought as well as non-prejudicial screening for differentially expressed genes (oligonucleotide arrays). These investigations will be performed under the auspices of the Cambridge-Hinxton Centre for Translational Research in Autoimmune Disease.

FINDINGS

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Lay Summary:
Multiple sclerosis is a serious disease. We have been developing a new treatment, which has shown encouraging results in early trials. This drug, called alemtuzumab (or Campath-1H), is an antibody that is given once a year. It kills off part of the immune system, called lymphocytes, which then gradually grow back. As they do, they sometimes get things wrong: in 30% of our patients we see the emergence of a new autoimmune disease, often thyroid disease. We have been trying to work out why this is. It turns out that a particular factor in the serum drives the lymphocytes to proliferate and die prematurely. Fascinatingly, this factor is raised in the blood of the people who develop autoimmune disease even before they have the alemtuzumab treatment. In other words, we have come across a blood test that tells us who is at risk of getting an autoimmune disease. We now need to see whether this can predict autoimmune disease in other situations where autoimmunity develops.

Scientific Summary:
We have studied patients with multiple sclerosis treated using the monoclonal antibody, alemtuzumab, a single dose of which (over 5 days) induces a prolonged T lymphopaenia. As the lymphocyte repertoire reconstitutes, 30% of patients develop autoimmune disease (typically against the thyroid or platelets). We have determined that this is not due to a differential depletion of regulatory T cells. But those patients who develop autoimmune disease have greater passive and fas-induced T lymphocyte apoptosis than those patients who do not develop autoimmunity. This correlates with a greater level of a particular serum cytokine in the autoimmune group. Importantly, this cytokine is raised in the serum of patients who go on to develop autoimmunity before alemtuzumab treatment. In other words, we have identified a biomarker which predicts the occurrence of autoimmunity after lymphopaenia. This has potential implications for those other clinical situations in which lymphopaenia and lymphocyte proliferation predispose to autoimmunity (HAART treatment of HIV, hematological stem cell transplantation, lups, CLL) as well as for generic mechanisms of autoimmunity

SELECTED PUBLICATIONS

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Cox A.L., Thompson S.A., Jones J.L., Robertson V.H., Hale G., Waldmann H., Compston D.A., and Coles A.J.  Lymphocyte homeostasis following therapeutic lymphocyte depletion in multiple sclerosis.  Eur J Immunol. 2005 Nov;35(11):3332-42.