A multicenter study for validation of biomarkers and observational study for immune regulatory mechanisms in Juvenile Dermatomyositis

Juvenile Dermatomyositis (JDM) is a rare but serious autoimmune disease in
children, mainly affecting proximal muscles and skin. The immunopathogenesis in
JDM is largely unknown, but both genetic and environmental factors appear to
play a role. For diagnosis of JDM, core set criteria have been developed.
However, evaluation of disease activity during follow up remains challenging,
as muscle enzymes do not correlate well to disease activity and inflammation.
Identification of inflammatory mediator signatures in disease (sub) types and
during disease course may provide new molecular diagnostic tools and will
facilitate tailor-made personalized medicine. In addition, a better
understanding of the inflammatory pathways involved in inflammatory myopathies
will help to design novel therapeutic strategies. In a pilot study we performed
a multiplex immunoassay for plasma levels of 45 proteins related to
inflammation in 25 JDM patients in four clinically well defined groups,
determined by clinical activity and treatment. We compared them with
age-matched healthy controls and children with non-autoimmune muscle disease
and we identified a signature panel of ten mediators for JDM, including IL-18,
CCL2, CCL4, CCL19, CCL27, CXCL10, CXCL13, TNFR1, TNFR2 and galectin-9. The
levels of CXCL10, TNFR2 and galectin-9 were most strongly correlated to
clinical scores. Based on these data we now hypothesize that the three
molecules CXCL10, TNFR2, and galectin-9 will be useful biomarkers for
monitoring JDM disease activity. We will therefore validate the correlation of
these markers with disease activity and their ability to predict disease
activity in JDM. In addition, we hypothesize that these proteins might also
play an important role in the inflammatory pathway in JDM. We therefore aim to
investigate these and other potential biomarkers in relation to disease
phenotype (e.g. disease severity and organ involvement). By comparing our
findings in JDM with related systemic autoimmune diseases - in which we now
know similar dominant pathways are active - we will gain insights into shared
and disease-specific immune mechanisms. This will contribute to our
understanding of JDM immune-pathogenesis in specific as well as the biological
(re)classification of juvenile systemic autoimmune disease in general.
The proposed research will identify markers that can improve molecular
diagnostics for disease monitoring for JDM and other inflammatory myopathies
and guide treatment. On the short term, this may lead to new treatment
strategies by either intensifying therapy in early disease course or to taper
more rapidly corticosteroids. Finally, data will give more insights into immune
mechanisms of JDM pathology and how this relates to other systemic autoimmune
diseases within the same spectrum.

Objective
1) Validate the biomarker potential of CXCL10, TNFR2, and galectin-9 in disease
activity monitoring of JDM and DM.
2) Determine the role of IL-18, CCL2, CCL4, CCL19, CCL27, CXCL10, CXCL13,
TNFR1, TNFR2, galectin-9 and other potential biomarkers in the
immunopathogenesis of JDM in relation to other systemic autoimmune diseases.

For the validation of CXCL10, TNFRII, and galectin-9 as biomarkers for disease
activity in JDM, and for our secondary objective, the following groups will be
analysed

- patients with JDM at disease onset and during follow-up
- patients (< 18 years old) with non-inflammatory muscle disease
- patients (< 18 years old) with systemic auto-immune disease
- healthy controls (<18 years old)
- Adult IIM patients at disease onset and during follow-up

Please also see Section 4. Study design in our study protocol (pages 18-24) for
a more detailed description of our study design.

- With a routine blood testing a maximum of 11 ml extra peripheral blood
sampling will be taken in children and 47 in adults. No extra venapunctures
will be done.
- In a subgroup of patients and controls an additional fingerprick will be done
(1 or 2 times, only in children of 12 years and older, with explicit consent).
In our S4S disease controls, extra capillary blood will be drawn in combination
with a routine fingerprick.
- Muscle biopsy for diagnostic procedure normally yields at least three biopsy
samples. Samples not being used for diagnostic procedures will be used for this
project. This also applies to other leftover body material that is obtained
through regular care/diagnostics (rest material).
- CMAS, MMT, DAS, CAT, CHAQ and other clinical data according to an
internationally agreed consensus core dataset for JDM (McCann et al. 2018) are
being routinely used in the clinic for follow-up of JDM patients.
- The MRC scale, adapted versions of the MDAAT and MDI, and SF-36 will be used
for assessment of disease activity in adult IIM patients.
- Clinical data of patients with other systemic autoimmune diseases are
recorded in the clinic as standard of care.

Juvenile dermatomyositis is a rare disease. With current treatment regimens,
children are at the moment exposed to at least 2 years of corticosteroids in
combination to methotrexate. About 50% of the patients respond well and under
this treatment remission is achieved within a few months after diagnosis. The
other 50% needs treatment changes, and up to date, no clear treatment plan is
yet established, but includes various immunosuppressive medications.
Identification of these subtypes of patients at time of diagnosis or during
early follow up may allow a different treatment approach and therefore a better
outcome. Good responders might benefit from early tapering of steroids,
non-responders from early treatment changes like introduction of biologics such
as rituximab and infliximab, or even from autologous stem cell transplantation.
Results of the biomarker study might lead to an interventional study where
treatment might be changed in an early phase of disease if there is no response
to the conventional therapy. Furthermore, the clinical phenotype of
dermatomyositis varies between adult and juvenile patients, like the higher
incidence of calcinosis, the lower incidence of interstitial lung disease and
the nearly absent correlation with malignancy in children. It will be also
interesting to determine if these three biomarkers are also elevated in adult
IIM patients, and therefore be also useful for our adult colleagues.
To optimize treatment protocols for children it is necessary to try to
understand more about the pathophysiological mechanisms. By comparing our
findings in JDM with other systemic autoimmune diseases we will gain insights
into shared and disease-specific immune mechanisms, which will contribute to
our understanding of JDM immunopathogenesis and help redefine the spectrum. The
reference group of systemic autoimmune diseases will thus primarily serve as a
comparison for JDM, but will additionally provide valuable data on the spectrum
of related diseases, as an additional benefit.