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Uveitis is the most common extra-articular
manifestation of Juvenile Idiopathic Arthritis (JIA). It is commonly
asymptomatic and, if unrecognized and untreated, can lead to blindness. The
identification of new diagnostic and/or predictive biomarkers would improve the
identification of children who are at high risk for uveitis and also to monitor
disease activity. Autoantibodies directed to the Dense Fine Speckled antigen (DFS70),
also known as Lens Epithelium-Derived Growth Factor (LEDGF), have been
described in a number of conditions including eye-related pathologies such as
Vogt-Koyanagi-Harada syndrome. We present two cases of oligoarticular
JIA-associated uveitis (JIA-U) with high titer antinuclear antibodies (ANA)
that were identified as DFS70 autoantibodies at the time of active bilateral
uveitis. Anti-DFS70 titres normalized following treatment of uveitis with
methotrexate and/or etanercept while ANA targeting other intracellular antigens
remained positive. This report suggests that anti-DFS70 autoantibodies may be a
potential risk factor and useful indicator of disease activity for JIA-U.
Additional multi-center and longitudinal studies would be important to validate
these findings.
BACKGROUND
Juvenile Idiopathic
Arthritis (JIA) is complicated by a high frequency of uveitis (JIA-U) marked by
inflammation of the anterior uveal tract [1]. The prediction and detection of
uveitis is a diagnostic challenge because it is often asymptomatic and if
untreated can lead to blindness [1,2]. Antinuclear Antibodies (ANA), observed
in 65-66% of JIA-U, have been regarded as a biomarker associated with uveitis
but has limited specificity because a positive conventional ANA test is also
seen in 37-47% of JIA without uveitis [1]. Autoantibodies producing a Dense
Fine Speckled (DFS) immunofluorescence pattern often react with the 70 kDa
DFS70 antigen (also known as lens epithelium-derived growth factor) [3,4].
Anti-DFS70 was reported in a variety of conditions such as atopic dermatitis,
eye diseases, juvenile localized scleroderma, juvenile idiopathic arthritis,
juvenile localized scleroderma, juvenile dermatomyositis and prostate cancer
[3,5] and was shown to be of higher frequency in young females [4,6]. Although
some evidence indicates that anti-DFS70 antibodies are stable over time [4],
little is known if anti-DFS70 titers are influenced by disease activity or
certain therapeutic interventions. This consideration might have important
clinical implications providing clinicians with an additional sensitive
parameter of disease activity and facilitate evidence-based treatment
decisions.
We report two patients with ANA positive
oligoarticular JIA-U who tested highly positive for anti-DFS70 antibodies by a
Chemiluminescence Immunoassay (CIA) at the time of active uveitis. However, the
test became negative after the uveitis was in remission.
CASE REPORT
The first patient was a healthy male who was diagnosed at one year of age with an ANA positive, persistent oligoarticular JIA. Recurrent flares of knee arthritis were treated with Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), Intraarticular Glucocorticoids (IAS) and Methotrexate (MTX). At eight years of age, he was diagnosed with a chronic relapsing bilateral uveitis which was not controlled with prednisolone eye drops and MTX. At the time of active uveitis, the ANA was positive at a titer of 1:1280 with a DFS Indirect Immunofluorescence (IIF) pattern International Consensus on ANA Patterns (ICAP),AC-2, http://www.anapatterns.org/ on HEp2 cells (Immuno Concepts Inc., Sacramento), consistent with anti-DFS70 reactivity [5]. Anti-DFS70 autoantibody reactivity was confirmed by CIA (38.2 chemiluminescence units [CU]: normal range <20 CU) (CIA: Inova Diagnostics Inc., San Diego, CA, USA). The uveitis was successfully treated with a combination of MTX, Etanercept and topical prednisolone eye drops. At 11 years of age when both his arthritis and uveitis were in remission, his anti-DFS70 CIA test was negative (CU<5). Although ANA titers had markedly decreased, they remained positive at a titer of 1:160. Further testing using autoantibody arrays (Connective 13, TheraDiag, Paris, France) failed to disclose the remaining autoantibody.
The
second case was a previously healthy girl diagnosed at five years of age with
an ANA positive oligoarticular JIA, treated with NSAIDs and IAS. One year
later, she developed a flare of arthritis and asymptomatic bilateral uveitis.
The ANA was positive at a titer of 1:5120 with a DFS IIF pattern (AC-2) and the
anti-DFS70 CIA test was highly positive (131.5 CU). The arthritis remained in
remission after treatment with NSAIDs and IAS, but the uveitis was not
controlled with topical therapy, therefore MTX was started. Approximately one
year later when her arthritis and uveitis were in remission, the anti-DFS70 CIA
was below the normal cut-off (CU<5), although the ANA remained positive at a
titer of 1:5120 with a homogenous and speckled nuclear pattern (AC-1; AC-3).
Further testing using autoantibody arrays (Connective 13, TheraDiag, Paris,
France) found antibodies to histones as one of the remaining autoantibodies.
DISCUSSION
A
previous study reported anti-DFS70 as detected by CIA in 2.1% of healthy
children and in 4.5% of pediatric sera referred for ANA testing [5]. In this
study of small disease cohorts, the frequency of anti-DFS70 was highest in
juvenile dermatomyositis (18.2%) and juvenile localized scleroderma (13.8%),
but less common in childhood systemic lupus erythematosus (5.7%), diffuse
cutaneous systemic sclerosis (4.5%), celiac disease (4.1%) and JIA (2.5%). Of
note, anti-DFS70 antibodies were observed 11.5% of children with uveitis and
JIA-U. However, there have been no reported studies of pediatric disease
cohorts to determine the sustainability of the anti-DFS70 response over time.
DFS70
is a chromatin-associated protein that protects cells from stress-induced
apoptosis including heat shock, oxidative stress, UV damage and serum starvation
[3,7-9]. Of interest, anti-DFS70 has been shown to be toxic to lens epithelial
cells, keratinocytes and fibroblasts [9]. The importance of these findings is
supported by several reports that have found an association between anti-DFS70
and eye-related pathologies [10,11]. For example, a report indicated that sera
from chronic uveitis patients with Vogt-Koyangi-Harada disease had a
significantly higher prevalence of anti-DFS70 antibodies compared to healthy
controls (24/36 vs. 8/37, p<0.001) [10]. Interestingly, in patients with Behçets
disease and sarcoidosis associated panuveitis, the prevalence of anti-DFS70
antibodies (34% and 25%) was almost same as apparently healthy controls (22%),
suggesting that the autoimmunity against DFS70 is not a secondary phenomenon
caused by a B cell response to tissue damage [10]. Another group detected
autoantibodies to DFS70 using ELISA in 71.4% of 21 Japanese atopic dermatitis
patients and 8/8 of the patients who also had cataracts tested positive and
cytotoxic activity of the anti-DFS70 against lens epithelial cells was reported
[11]. It was suggested that binding of the autoantibodies to released DFS70
autoantigen has a pathogenic role by preventing its uptake by local tissue
cells [11], whereas anti-DFS70 autoantibodies may be protective [12]. Last,
although the hormonal status of pre-pubertal females is likely not a factor, a
more recent report indicated that the hormonal status of adult females may
influence anti-DFS70 titres [13].
Nevertheless,
the pathogenic role of DFS70 autoantibodies in various eye related inflammatory
conditions remains unclear. It is uncertain whether this autoimmunity is the
primary cause of disease or a secondary phenomenon by triggering the
elicitation of DFS70 autoantibodies in a pro-inflammatory context. In the
latter case, control of inflammation such as in our cases might then lead to a
decreased titer or disappearance of DFS70 autoantibodies. Accordingly, based on
our case reports, anti-DFS70 antibodies may serve as an indicator for
successful therapy and remission of uveitis in JIA. Further systematic
investigations are required to determine if certain therapeutics (i.e., MTX,
Etanercept) influence anti-DFS70 titers. In our patients, anti-DFS70 antibodies
became negative in one patient following treatment with MTX, and in the other
after starting Etanercept in combination with MTX.
In our
case reports, we noted that the IIF ANA remained positive despite a decrease of
anti-DFS70 to within normal range as detected by CIA. This observation cannot
be readily explained by autoantibody isotype differences because both the ANA
and CIA use anti-human IgG secondary antibodies. Neither can it be explained by
decreased sensitivity of CIA because earlier studies have shown that CIA is
both highly sensitive and specific for anti-DFS70 [14]. A plausible explanation
is that a second autoantibody such as a molecular ligand or ‘partner’ of DFS70,
such as methyl CpG binding protein 2 (MeCP2) [15], may be unaffected by therapeutic
intervention. Indeed, earlier studies in our lab have shown that some
anti-DFS70 sera when assayed by western immunoblot show reactivity to a second
protein of similar molecular mass (unpublished). In a recent published study of
sera that had the DFS70-IIF pattern, autoantibodies directed to MeCP2, a
molecular ‘partner’ of DFS70, were not detected [11]. However, since this study
did not focus on anti-MeCP2 in specific conditions, it would be important to
test uveitis sera for this reactivity.
If
these observations are validated, the identification of the anti-DFS70
autoantibody as an additional biomarker and risk factor for the development of
JIA-U will allow an earlier diagnosis and expedite the initiation of treatment
with the goal to prevent morbidity such as vision loss and/or blindness. In
addition, if anti-DFS70 continue to be positive during the disease course it
might indicate a higher risk for uveitis flares and might therefore, determine
and guide frequency of ophthalmologic examination and screening. Furthermore,
this is the first report of anti-DFS70 autoantibodies becoming negative after
treatment and/or disease remission which implies a pathogenic role of the
autoantibodies as well as serving as a useful indicator for disease activity.
Accordingly, the clinical use of anti-DFS has the potential to greatly impact
patient care and clinical outcomes in children with JIA-U.
CONCLUSION
Anti-DFS70
is a potential risk factor and changes in titers may be an indicator of disease
activity for JIA-associated uveitis.
ACKNOWLEDGMENT
The
authors wish to thank the patients and their family for allowing this paper to
be published and Haiyan Hou and Meifeng Zhang (Mitogen Advanced Diagnostics,
Calgary, AB Canada) for laboratory analyses.
CONSENT
Written consent
from patients and/or their legal guardians was obtained. In addition, this case
review was carried out in compliance with the Helsinki Declaration of 1975 for
human studies as revised in 2013.
CONFLICT OF INTEREST
Three authors
(HS, KC, MYC) have no conflicts of interests. MJF is a paid consultant, has
received honoraria or has received gifts in kind from Inova Diagnostics (San
Diego, CA).
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