In utero position matters for littermate cell transfer in mice: an additional and confounding source with maternal microchimerism

Introduction

Feto-maternal cell transfer during pregnancy is called microchimerism (Mc). Its persistence in respective hosts is increasingly studied as to its potential role in immune tolerance, autoimmunity, cancer, and degenerative diseases. Murine models with transgenic reporter genes, heterozygously carried by the mother, allow maternal Mc tracking in wild-type (WT) offspring. However, as gestation in mice is multi-embryonic, an exchange of cells between fetuses carrying the same reporter gene as their mother and negative WT littermate, named littermate Mc (LMc), can occur and be confounded with the maternal source. We propose here to evaluate LMc contribution in mice.

Methods

To avoid the maternal confounding source of Mc, transgenic males, heterozygous for a reporter gene, here, the human leukocyte antigen DRB1*04 (DR4+/-), were crossed with WT females (DR4-/-). DR4+/- LMc was specifically quantified by HLA-DR4 quantitative PCR, i) in utero in main organs from 15 DR4-/- fetuses from three litters of 11, nine, and five; and ii) after birth in two litters of eight pups: in two DR4-/- stillborns and four DR4-/- adult mice.

Results

At embryonic stages, DR4-/- fetuses having one or two nearby DR4+/- littermates in the same uterine horn were almost seven times more frequently positive for DR4- microchimerism in their organs (p = 0.01) and had quantitatively more LMc (p = 0.009) than those without nearby DR4+/- littermates. Furthermore, LMc persists at birth and into adulthood with interindividual heterogeneity.

Conclusions

This study identifies heterogeneity for LMc acquisition according to in utero position and different interpretation of previously published results on maternal Mc in mice.

Very Early Diagnosis and Management of Congenital Erythropoietic Porphyria

Congenital erythropoietic porphyria (CEP), a rare form of porphyria, is caused by a defect in the heme biosynthesis pathway of the enzyme uroporphyrinogen III synthase (UROS). Uroporphyrinogen III synthase deficiency leads to an accumulation of nonphysiological porphyrins in bone marrow, red blood cells, skin, bones, teeth, and spleen. Consequently, the exposure to sunlight causes severe photosensitivity, long-term intravascular hemolysis, and eventually, irreversible mutilating deformities. Several supportive therapies such as strict sun avoidance, physical sunblocks, red blood cells transfusions, hydroxyurea, and splenectomy are commonly used in the management of CEP. Currently, the only available curative treatment of CEP is hematopoietic stem cell transplantation (HSCT). In this article, we present a young girl in which precocious genetic testing enabled early diagnosis and allowed curative treatment with HSCT for CEP at the age of 3 months of age, that is, the youngest reported case thus far.

Upscaling xylem phenology: sample size matters

BACKGROUND AND AIMS

Upscaling carbon allocation requires knowledge of the variability at the scales at which data are collected and applied. Trees exhibit different growth rates and timings of wood formation. However, the factors explaining these differences remain undetermined, making samplings and estimations of the growth dynamics a complicated task, habitually based on technical rather than statistical reasons. This study explored the variability in xylem phenology among 159 balsam firs [Abies balsamea (L.) Mill.].

METHODS

Wood microcores were collected weekly from April to October 2018 in a natural stand in Quebec, Canada, to detect cambial activity and wood formation timings. We tested spatial autocorrelation, tree size and cell production rates as explanatory variables of xylem phenology. We assessed sample size and margin of error for wood phenology assessment at different confidence levels.

KEY RESULTS

Xylem formation lasted between 40 and 110 d, producing between 12 and 93 cells. No effect of spatial proximity or size of individuals was detected on the timings of xylem phenology. Trees with larger cell production rates showed a longer growing season, starting xylem differentiation earlier and ending later. A sample size of 23 trees produced estimates of xylem phenology at a confidence level of 95 % with a margin of error of 1 week.

CONCLUSIONS

This study highlighted the high variability in the timings of wood formation among trees within an area of 1 km2. The correlation between the number of new xylem cells and the growing season length suggests a close connection between the processes of wood formation and carbon sequestration. However, the causes of the observed differences in xylem phenology remain partially unresolved. We point out the need to carefully consider sample size when assessing xylem phenology to explore the reasons underlying this variability and to allow reliable upscaling of carbon allocation in forests.

PAD2 immunization induces ACPA in wild-type and HLA-DR4 humanized mice

Rheumatoid arthritis (RA) is associated with HLA‐DRB1 alleles expressing the "shared epitope." RA is usually preceded by the emergence of anti‐citrullinated protein autoantibodies (ACPAs). ACPAs recognize citrulline residues on numerous proteins. Conversion of arginine into citrulline is performed by enzymes called peptidyl arginine deiminases (PADs). We have previously demonstrated that C3H mice immunized with PADs can produce ACPAs by a hapten‐carrier mechanism.

Here, we address the influence of HLA‐DR alleles in this model in mice expressing RA‐associated HLA‐DRB1*04:01 (KO/KI*04:01), HLA‐DRB1*04:04 (KO/KI*04:04), or non‐RA‐associated HLA‐DRB1*04:02 (KO/KI*04:02) after murine PAD2 immunization.

Immunization with mPAD2 triggers production of ACPAs in wild‐type (WT) and HLA‐DR4 C57BL/6 mice. Both I‐A^b and HLA‐DR are involved in the activation of mPAD2‐specific T lymphocytes. Among HLA‐DR4 mice, mice expressing RA‐associated HLA‐DRB1*04:01 are the best responders to mPAD2 and the best anti‐citrullinated peptide antibody producers.

How RA Associated HLA-DR Molecules Contribute to the Development of Antibodies to Citrullinated Proteins: The Hapten Carrier Model

The risk to develop ACPA positive rheumatoid arthritis (RA), the most destructive type of autoimmune arthritis, is carried by HLA-DRB1 alleles containing a 5 amino acid motif: the shared epitope (SE). RA is preceded by the emergence of disease specific anti citrullinated protein antibodies (ACPA). SE positive HLA-DRB1 alleles are associated with ACPA and ACPA positive RA, not with ACPA negative RA, suggesting that ACPA contribute to the pathogenesis of RA. Understanding how HLA-DRB1 genotypes influence ACPA could lead to a curative or preventive treatment of RA. The “Shared epitope binds citrullinated peptides “ hypothesis suggests that RA associated HLA-DR alleles present citrullinated peptides to T cells that help ACPA producing B cells. The “Hapten carrier model” suggests that PAD4 is the target of the T cells which help ACPA specific B cells through a hapten carrier mechanism in which PAD4 is the carrier and citrullinated peptides are the haptens. Direct binding assay of citrullinated peptides to purified HLA-DR molecules does not support the “shared epitope binds citrullinated peptides” hypothesis. The Odds Ratios to develop ACPA positive RA associated with each of 12 common HLA-DRB1 genotypes match the probability that the two HLA-DR molecules they encode can bind at least one peptide from PAD4, not from citrullinated fibrinogen. Thus, PAD4 tolerization might stop the carrier effect and switch off production of ACPA.

PAD4 Immunization Triggers Anti-Citrullinated Peptide Antibodies in Normal Mice: Analysis With Peptide Arrays

The critical immunological event in rheumatoid arthritis (RA) is the production of antibodies to citrullinated proteins (ACPAs), ie proteins on which arginines have been transformed into citrullines by peptidyl arginine deiminases (PAD). In C3H mice, immunization with PAD4 triggers the production of ACPAs. Here, we developed a peptide array to analyze the fine specificity of anti-citrullinated peptide antibodies and used it to characterize the ACPA response after hPAD4 immunization in mice expressing different H-2 haplotypes. Sera from C3H, DBA/2, BALB/c and C57BL/6 mice immunized with human PAD4 (hPAD4) or control-matched mice immunized with phosphate buffered saline (PBS) were used to screen peptide arrays containing 169 peptides from collagen, filaggrin, EBNA, proteoglycan, enolase, alpha and beta fibrinogen, histon and vimentin. Human PAD4 immunization induced antibodies directed against numerous citrullinated peptides from fibrinogen, histon 4 and vimentin. Most peptides were recognized under their arginine and citrullinated forms. DBA/2 and BALB/c mice (H-2d) had the lowest anti-citrullinated peptide IgG responses. C3H (H-2k) and BL6 mice (H-2b) had the highest anti-citrullinated peptide IgG responses. The newly developed peptide array allows us to characterize the ACPA production after hPAD4 immunization in mice on the H-2d, H-2k or H-2b backgrounds. This sensitive tool will be useful for further studies on mice for prevention of ACPA production by PAD tolerization.

In Rheumatoid Arthritis Patients, HLA-DRB1*04:01 and Rheumatoid Nodules Are Associated With ACPA to a Particular Fibrin Epitope

Objectives

Rheumatoid arthritis (RA) is associated with HLA-DRB1 genes encoding the shared epitope (SE), a 5-amino acid motive. RA is usually preceded by the emergence of anti-citrullinated protein/peptide antibodies (ACPAs). Citrulline is a neutral amino acid resulting from post-translational modification of arginine involved in peptidic bounds (arginyl residue) by PeptidylArginine Deiminases (PADs). ACPAs recognize epitopes from citrullinated human fibrin(ogen) (hFib) and can be specifically detected by the AhFibA assay. Five citrullinated peptides derived from hFib together represent almost all of the epitopes recognized by patients with ACPA-positive RA, namely: α36-50cit, α171-185cit, α501-515cit, α621-635cit, and β60-74cit. The use of antibody fine specificities as markers of clinical phenotypes has become a major challenge. Our objective was to study whether RA clinical characteristics and HLA-DRB1 genetic background were associated with a specific reactivity against the epitopes borne by the five peptides.

Methods

184 ACPA-positive RA patients fulfilling the 2010 ACR/EULAR criteria were studied. Patient characteristics including HLA-DRB1 genotype, were collected from their medical files. Anti-CCP2 antibodies, AhFibA, and antibodies against the five citrullinated hFib (hFib-cit) peptides were analyzed by ELISA.

Results

Anti-α505-515cit antibodies were associated with HLA-DRB1*04:01 (OR = 5.52 [2.00 - 13.64]; p = 0.0003). High level anti-α505-515cit antibodies were associated with rheumatoid nodules (OR = 2.71 [1.00 - 7.16], p= 0.044).

Conclusion

Immune complexes containing anti-α501-515cit antibodies and rheumatoid factors might be involved in the development of rheumatoid nodules on the HLA-DRB1*04:01 background. Apheresis of these epitope-specific antibodies might be a new therapeutic opportunity for patients with rheumatoid nodules.

AB0058 ASSOCIATION BETWEEN HLA-DRB1*04:01, RHEUMATOID NODULES AND PARTICULAR EPITOPES OF CITRULLINATED FIBRIN IN PATIENTS WITH RHEUMATOID ARTHRITIS

Background:

Rheumatoid arthritis (RA) is associated with HLA-DRB1 genes encoding the shared epitope (SE), a 5 amino acid motive. RA is usually preceded by the emergence of anti-citrullinated protein antibodies (ACPAs) detected by anti-CCP2 tests. Citrullin is a neutral amino acid resulting from post translational modification of arginin by Peptidyl Arginyl Deiminases (PADs). ACPAs recognize epitopes from citrullinated human fibrinogen (Fib-cit) and can be specifically detected by the AhFibA assay. Five peptides derived from Fib-cit together represent almost all of the epitopes recognized by patients with ACPA-positive RA: β60–74cit, α36–50cit, α621–635cit, α501–515cit and α171–185cit. As RA is a pleiomorphic disease, whose evolution is difficult to predict, the use of antibody fine specificity as a marker of clinical phenotypes has become a major challenge.

Objectives:

Our objective was to study whether clinical characteristics and HLA-DRB1 genetic background were associated with a specific reactivity against these epitopes.

Methods:

184 ACPA positive RA patients fulfilling the 2010 ACR/EULAR criteria were studied. Patients characteristics, including HLA-DRB1 genotype, were collected from their medical files. Anti-CCP2, AhFibA, Rheumatoid Factors (RF), and antibodies against the five major Fib-cit peptides were analyzed using ELISA assays.

Results:

Anti-CCP2 and AhFibA titres were strongly correlated (rs: 0.7037; p = 5.69x10-29, Pearson’s). Anti-α505-515cit antibodies were associated with HLA-DRB1*04:01 (OR = 5.52 [2.00 – 13.64]; p = 0.0003). High level anti-α505-515cit antibodies were significantly associated with rheumatoid nodules (OR = 2.71 [1.00 – 7.16], p= 0.044). Anti α501–515cit antibodies were associated with RF (OR=2.31 [1.10 – 4.78], p= 0.026).

Conclusion:

Immune complexes containing anti-α501–515cit antibodies and rheumatoid factors might be involved in the development of rheumatoid nodules on the HLA-DRB1*04:01 background. These findings highlight the role played by the HLA-DRB1*04:01 molecule and its rapid intracellular route into the lysosomes, enabling original antigen processing. Finally, purifying these epitope specific antibodies might be a new therapeutic opportunity for rheumatoid nodules.

Disclosure of Interests:

None declared

Comparison of nine heart rate-based models to predict work metabolism of Forest workers

Predicted work metabolism (WM) from 9 heart rate (HR)-based models were compared to measured WM obtained during work in 39 forest workers. Using measured (i.e. raw) HR in these models can overestimate actual WM since the HR increase associated with body heat accumulation is non-metabolic. Hence, accuracy of WM prediction was assessed on all possible combinations of models using raw HR and corrected HR (thermal component removed) and with five different estimates of maximum work capacity (MWC) for the models that require it as an input. The 50 model combinations produced a wide range of WM estimates. Three models using individual calibration produced the lowest RMSE and narrowest LoA with corrected HR (rRMSE ≤13%; LoA [rBias <5% ± 25%]). One of the models that requires neither determination of the thermal component nor individual calibration performed very well (rRMSE = 18%; LoA [rBias = 1% ± 36%]). Practitioner Summary: These results provide a better understanding of the accuracy of various HR-based work metabolism (WM) estimation models. This information should prove particularly useful to ergonomics professionals wishing to select a method that provides accurate estimation of WM from HR measurements during work in varied thermal environments. Abbreviations: BMI: body mass index; HR: heart rate (beats per min); HR99: HR value exceeded during 99% of the duration of the HR recording period; HRcorr: heart rate without thermal pulses; HRraw: measured heart rate; HRres: heart rate reserve; HRrest: heart rate at rest; LoA: limits of agreement; Mrest: resting metabolism; MWC: maximum work capacity; RMSE: root mean square error; VO2: oxygen consumption; VO2 max: maximum oxygen consumption; WM: work metabolism.

Do RA associated HLA-DR molecules bind citrullinated peptides or peptides from PAD4 to help the development of RA specific antibodies to citrullinated proteins?

PURPOSE

Rheumatoid arthritis (RA) is associated with HLA-DRB1 genes encoding a five amino acid basic motive, the shared epitope SE). Each HLA-DRB1 genotype defines a genotype specific risk of developing RA. RA is preceded by the emergence of anti citrullinated protein antibodies (ACPAs). Citrullin is a neutral version of arginin, a basic amino acid, formed after post translational modification by Peptidyl Arginyl Deiminases (PADs). HLA-DRB1 genes associated with RA are also associated with ACPAs. Two models might explain this association. Here we tested both models for prediction of HLA-DRB1 genotypic risks of developing RA.

METHODS

We calculated the likelihoods for the 2 HLA-DR molecules encoded by 12 common HLA-DRB1 genotypes to bind at least one randomly chosen peptide from PAD4 or fibrinogen(native or citrullinatd) and compared them with the 12 respective HLA-DRB1genotypic risks of developing RA.

RESULTS

HLA-DRB1 Genotypic risks of developing RA correlate with likelihoods of binding PAD4 peptides, not citrullinated Fibrinogen peptides. Thus, the molecular basis for the association of HLA-DR and ACPA positive RA is most likely the capability for RA associated HLA-DR molecules to bind peptides(s) from PAD4.

Peptidylarginine Deiminase Autoimmunity and the Development of Anti-Citrullinated Protein Antibody in Rheumatoid Arthritis: The Hapten-Carrier Model

Objective

The presence of autoantibodies to citrullinated proteins (ACPAs) often precedes the development of rheumatoid arthritis (RA). Citrullines are arginine residues that have been modified by peptidylarginine deiminases (PADs). PAD4 is the target of autoantibodies in RA. ACPAs could arise because PAD4 is recognized by T cells, which facilitate the production of autoantibodies to proteins bound by PAD4. We previously found evidence for this hapten–carrier model in mice. This study was undertaken to investigate whether there is evidence for this model in humans.

Methods

We analyzed antibody response to PAD4 and T cell proliferation in response to PAD4 in 41 RA patients and 36 controls. We tested binding of 65 PAD4 peptides to 5 HLA–DR alleles (DRB1*04:01, *04:02, *04:04, *01:01, and *07:01) and selected 11 PAD4 peptides for proliferation studies using samples from 22 RA patients and 27 controls. Peripheral blood lymphocytes from an additional 10 RA patients and 7 healthy controls were analyzed by flow cytometry for CD3, CD4, CD154, and tumor necrosis factor expression after PAD4 stimulation.

Results

Only patients with RA had both antibodies and T cell responses to PAD4. T cell response to peptide 8, a PAD4 peptide, was associated with RA (P = 0.02), anti‐PAD4 antibodies (P = 0.057), and the shared epitope (P = 0.05).

Conclusion

ACPA immunity is associated with antibodies to PAD4 and T cell responses to PAD4 and PAD4 peptides. These findings are consistent with a hapten–carrier model in which PAD4 is the carrier and citrullinated proteins are the haptens.

Mosaicism of XX and XXY cells accounts for high copy number of Toll like Receptor 7 and 8 genes in peripheral blood of men with Rheumatoid Arthritis

The X chromosome, hemizygous in males, contains numerous genes important to immunological and hormonal function. Alterations in X-linked gene dosage are suspected to contribute to female predominance in autoimmunity. A powerful example of X-linked dosage involvement comes from the BXSB murine lupus model, where the duplication of the X-linked Toll-Like Receptor 7 (Tlr7) gene aggravates autoimmunity in male mice. Such alterations are possible in men with autoimmune diseases. Here we showed that a quarter to a third of men with rheumatoid arthritis (RA) had significantly increased copy numbers (CN) of TLR7 gene and its paralog TLR8. Patients with high CN had an upregulated pro-inflammatory JNK/p38 signaling pathway. By fluorescence in situ hybridization, we further demonstrated that the increase in X-linked genes CN was due to the presence of an extra X chromosome in some cells. Men with RA had a significant cellular mosaicism of female (46,XX) and/or Klinefelter (47,XXY) cells among male (46,XY) cells, reaching up to 1.4% in peripheral blood. Our results present a new potential trigger for RA in men and opens a new field of investigation particularly relevant for gender-biased autoimmune diseases.

Worker heat stress prevention and work metabolism estimation: comparing two assessment methods of the heart rate thermal component

The heart rate thermal component ( ΔHRT ) can increase with body heat accumulation and lead to work metabolism (WM) overestimation. We used two methods (VOGT and KAMP) to assess ΔHRT of 35 forest workers throughout their work shifts, then compared ΔHRT at work and at rest using limits of agreement (LoA). Next, for a subsample of 20 forest workers, we produced corrected WM estimates from ΔHRT and compared them to measured WM. Although both methods produced significantly different ΔHRT time-related profiles, they yielded comparable average thermal cardiac reactivity (VOGT: 24.8 bpm °C^-1; KAMP: 24.5 bpm °C^-1), average ΔHRT (LoA: 0.7 ± 11.2 bpm) and average WM estimates (LoA: 0.2 ± 3.4 ml O₂ kg^-1min^-1 for VOGT, and 0.0 ± 5.4 ml O₂ kg^-1min^-1 for KAMP). Both methods are suitable to assess heat stress through ΔHRT and improve WM estimation. Practitioner summary: We compared two methods for assessing the heart rate thermal component ( ΔHRT ), which is needed to produce a corrected HR profile for estimating work metabolism (WM). Both methods yielded similar ΔHRT estimates that allowed accurate estimations of heat stress and WM at the group level, but they were imprecise at the individual level. Abbreviations: AIC: akaike information criterion; bpm: beats per minute; CI: confidence intervals; CV: coefficient of variation in %; CV drift: cardiovascular drift; ΔHR_T: the heart rate thermal component in bpm; ΔHR_T: the heart rate thermal component in bpm; ΔΔHR_T: variation in the heart rate thermal component in bpm; ΔT_C: variation in core body temperature in °C; HR: heart rate in bpm; HRmax: maximal heart rate in bpm; Icl: cloting insulation in clo; KAMP: Kampmann et al. (2001) method to determe ΔHR_T; LoA: Limits of Agreement; PMV-PPD: the Predicted Mean Vote and Predicted Percentage Dissatisfied; PHS: Predicted Heat Strain model; RCM: random coefficients model; SD: standard deviation; TC: core body temperature in °C; TCR: thermal cardiac reactivity in bpm °C^-1; τ_ΔHRT: rate of change in the heart rate thermal component in bpm min^-1; τ_TC: rate of change in core body temperature in °C min^-1; t_α,n-1: Student's t statistic with level of confidence alpha and n^-1 degrees of freedom; TWL: Thermal Work Limit model; V̇O2 : oxygen consumption in ml O₂ kg^-1 min^-1; V̇O2 max: maximal oxygen consumption in ml O₂ kg^-1 min^-1; VOGT: Vogt et al. (1973) method to determine ΔHR_T; WBGT: Wet-Bulb Globe Temperature in °C; WM: work metabolism.

Porphyromonas gingivalis experimentally induces periodontis and an anti-CCP2-associated arthritis in the rat

OBJECTIVES

Association between periodontal disease (PD) and rheumatoid arthritis (RA) has been extensively described, but direct evidence of causal involvement of PD in RA is missing. We investigated the priming role of oral Porphyromonas gingivalis (P. gingivalis) in PD and subsequent RA and we assessed biomarkers of bone resorption and arthritis development in rats.

METHODS

Lewis rats were orally exposed to either P. gingivalis, Prevotella intermedia or control gel for 1 month and then followed for 8 months. The onset and development of PD was assessed by serology, gingivitis severity and micro-CT (µCT). We investigated arthritis development using circulating proinflammatory markers, anticyclic citrullinated peptide (CCP), anticitrullinated protein antibody (ACPA), ankle histology and µCT.

RESULTS

PD was only observed in the P. gingivalis treated rats, as early as 1 month postexposure. Joint and systemic inflammation were detected only in the P. gingivalis group after 4 and 8 months. At 8 months, inflammatory cell infiltrate was observed in ankle joints and paralleled cortical erosions and overall cortical bone reduction. Furthermore, anti-CCP2 correlated with local and systemic bone loss.

CONCLUSIONS

In our long-term study, PD induced by oral exposure to P. gingivalis triggered seropositive arthritis, with systemic inflammation and bone erosions. This is the first in vivo demonstration of arthritis induced by oral priming with P. gingivalis.

A case of congenital lipomatous overgrowth, vascular malformations, epidermal nevi, spinal/skeletal anomalies and/or scoliosis syndrome with lipoatrophy as an important clinical manifestation

Congenital lipomatous overgrowth, vascular malformations, epidermal nevi, spinal/skeletal anomalies and/or scoliosis syndrome is a PIK3CA-related overgrowth spectrum presenting with congenital, asymmetric, disproportionate overgrowth associated with dysregulated adipose tissue, enlarged bony structures, and mixed primarily truncal vascular malformations. We present this case to raise awareness that very thin body habitus (lipoatrophy) contrasting with areas of overgrowth can be an important clinical feature of this syndrome and, if not recognized, can lead to unnecessary investigations.

How microchimerism can impart HLA susceptibility in patients with rheumatoid arthritis

Rheumatoid arthritis, a chronic inflammatory joint disease, is strongly associated with HLA-DRB1*01 and *04 alleles that have in common similar 5-amino acid motifs in the third hypervariable region of DRB1 (QKRAA, QRRAA, RRRAA), the so called shared epitope (SE). Most patients with RA carry 1 or 2 doses of the SE, with particular genetic combinations at higher risk. In recent work we provided evidence that patients who lack HLA-DRB1*01 and/or *04 alleles can acquire RA susceptibility through fetal, maternal or iatrogenic microchimerism. We also discuss how Mc carrying HLA-DRB1*04 alleles is more likely to be present in the peripheral blood of RA patients compared to Mc carrying HLA-DRB1*01 alleles. We further analyze our results in light of the hierarchy for RA risk with different combinations of the SE. How Mc could contribute to RA susceptibility and whether it also contributes to the hierarchy of risk observed with particular combinations of SE-containing alleles is certainly the beginning of an intriguing story and may offer hope for future therapeutic and/or preventative interventions.

Newly Identified BRAF Mutation in Rheumatoid Arthritis

OBJECTIVE

Rheumatoid arthritis (RA)-associated autoantibodies include those directed at the kinase site of BRAF (v-Raf murine sarcoma viral oncogene homolog B1), a serine-threonine kinase involved in the MAPK signaling pathway. To understand anti-BRAF immunization, we sought to identify BRAF mutations in the peripheral blood lymphocytes (PBLs) of patients with RA.

METHODS

We first cloned the major BRAF region known for mutations in the pCR2.1 vector, using genomic DNA from the PBLs of 8 RA patients. For each patient, 100 clones were sequenced. In 5 of 8 patients, we detected a new BRAF mutation in 1 clone. The frequency of this new mutation was evaluated by droplet digital polymerase chain reaction in PBLs from RA patients and controls. To test whether p.Val600Ala influences the kinase activity of BRAF, we developed an in vitro assay based on phosphorylation of MEK-1, a major BRAF substrate.

RESULTS

A BRAF mutation, p.Val600Ala, was identified in 1 of 8,000 PBLs and 1 of 6,000 T lymphocytes from RA patients and in 1 of 12,500 PBLs and 1 of 12,500 T lymphocytes from controls. The BRAF p.Val600Ala mutation was not correlated with the presence of anti-BRAF autoantibodies. The p.Val600Ala mutation activated phosphorylation of MEK-1 in vitro.

CONCLUSION

Most RA patients have a p.Val600Ala mutation in the BRAF gene. This mutation activates the kinase activity of BRAF. The p.Val600Ala mutation could activate the MAPK pathway, leading to the activation of T lymphocytes.

Acquired Immune Deficiency Syndrome-Associated Kaposi Sarcoma in a Child Presenting as a Solitary Plantar Hyperkeratotic Plaque

BACKGROUND AND OBJECTIVE

Acquired immune deficiency syndrome (AIDS)-associated Kaposi sarcoma (KS) among the pediatric population is a rare entity in North America and Europe, and its cutaneous manifestations are not well defined in the literature. The investigators report the case of a boy with an AIDS-associated KS presenting as an infiltrated hyperkeratotic plaque of the plantar arch.

METHODS AND RESULTS

An 11-year-old African boy with congenital human immunodeficiency virus (HIV) had a skin biopsy of the plantar lesion that was consistent with a KS. The patient also presented intestinal and pulmonary symptoms; combined chemotherapy regimen and highly active antiretroviral therapy were given in the presence of systemic involvement.

CONCLUSION

AIDS-associated KS poses a particular challenge to clinical diagnosis, since it can manifest with a variety of lesions. Dermatologists should have a low threshold for performing a skin biopsy in patients with HIV.

Long term treatment with abatacept or tocilizumab does not increase Epstein-Barr virus load in patients with rheumatoid arthritis - A three years retrospective study

BACKGROUND

Epstein-Barr Virus (EBV) is a widely disseminated lymphotropic herpes virus implicated in benign and malignant disorders. In transplant patients, immunosuppressive drugs (cyclosporine) diminish control of EBV replication, potentially leading to lymphoproliferative disorders (LPD). Rheumatoid arthritis (RA) patients have impaired control of EBV infection and have EBV load ten times higher than controls. As post transplant patients, patients with RA have increased risk of developing lymphomas. Immunosuppressive drugs used to treat RA (conventional disease modifying drugs cDMARDs or biologics bDMARDs) could enhance the risk of developing LPD in RA patients. We have previously shown that long term treatment with Methotrexate and/or TNF alpha antagonists does not increase EBV load in RA. Our objective was to monitor the Epstein-Barr Virus load in RA patients treated with Abatacept (CTLA4 Ig), a T cell coactivation inhibitor, and Tocilizumab, an anti IL6 receptor antibody.

METHODS

EBV load in the peripheral blood mononuclear cells (PBMCs) of 55 patients under Abatacept (in 34% associated with Methotrexate) and 35 patients under Tocilizumab (in 37% associated with Methotrexate) was monitored for durations ranging from 6 months to 3 years by real time PCR. The influences of treatment duration and disease activity score 28 (DAS28) index on EBV load were analyzed.

RESULTS

Abatacept did not significantly modify EBV load over time. Tocilizumab significantly diminished EBV load over time. No patient (of 90) developed EBV associated lymphoma.

CONCLUSION

Long term treatment with Abatacept or Tocilizumab does not increase EBV load in the PBMNCs of patients with RA.

Anti-Ephrin Type-B Receptor 2 (EphB2) and Anti-Three Prime Histone mRNA EXonuclease 1 (THEX1) Autoantibodies in Scleroderma and Lupus

In a pilot ProtoArray analysis, we identified 6 proteins out of 9483 recognized by autoantibodies (AAb) from patients with systemic sclerosis (SSc). We further investigated the 6 candidates by ELISA on hundreds of controls and patients, including patients with Systemic Lupus Erythematosus (SLE), known for high sera reactivity and overlapping AAb with SSc. Only 2 of the 6 candidates, Ephrin type-B receptor 2 (EphB2) and Three prime Histone mRNA EXonuclease 1 (THEX1), remained significantly recognized by sera samples from SSc compared to controls (healthy or with rheumatic diseases) with, respectively, 34% versus 14% (P = 2.10⁻⁴) and 60% versus 28% (P = 3.10⁻⁸). Above all, EphB2 and THEX1 revealed to be mainly recognized by SLE sera samples with respectively 56%, (P = 2.10⁻¹⁰) and 82% (P = 5.10⁻¹³). As anti-EphB2 and anti-THEX1 AAb were found in both diseases, an epitope mapping was realized on each protein to refine SSc and SLE diagnosis. A 15-mer peptide from EphB2 allowed to identify 35% of SLE sera samples (N = 48) versus only 5% of any other sera samples (N = 157), including SSc sera samples. AAb titers were significantly higher in SLE sera (P<0.0001) and correlated with disease activity (p<0.02). We could not find an epitope on EphB2 protein for SSc neither on THEX1 for SSc or SLE. We showed that patients with SSc or SLE have AAb against EphB2, a protein involved in angiogenesis, and THEX1, a 3’-5’ exoribonuclease involved in histone mRNA degradation. We have further identified a peptide from EphB2 as a specific and sensitive tool for SLE diagnosis.

Evaluation of X Chromosome Inactivation with Respect to HLA Genetic Susceptibility in Rheumatoid Arthritis and Systemic Sclerosis

Background

Autoimmune diseases, including rheumatoid arthritis (RA) and systemic sclerosis (SSc) are characterized by a strong genetic susceptibility from the Human Leucocyte Antigen (HLA) locus. Additionally, disorders of epigenetic processes, in particular non-random X chromosome inactivation (XCI), have been reported in many female-predominant autoimmune diseases. Here we test the hypothesis that women with RA or SSc who are strongly genetically predisposed are less susceptible to XCI bias.

Methods

Using methylation sensitive genotyping of the androgen receptor (AR) gene, XCI profiles were performed in peripheral blood mononuclear cells from 161 women with RA, 96 women with SSc and 100 healthy women. HLA-DRB1 and DQB1 were genotyped. Presence of specific autoantibodies was documented for patients. XCI skewing was defined as having a ratio ≥ 80:20 of cells inactivating the same X chromosome.

Results

110 women with RA, 68 women with SSc, and 69 controls were informative for the AR polymorphism. Among them 40.9% of RA patients and 36.8% of SSc patients had skewed XCI compared to 17.4% of healthy women (P = 0.002 and 0.018, respectively). Presence of RA-susceptibility alleles coding for the “shared epitope” correlated with higher skewing among RA patients (P = 0.002) and such correlation was not observed in other women, healthy or with SSc. Presence of SSc-susceptibility alleles did not correlate with XCI patterns among SSc patients.

Conclusion

Data demonstrate XCI skewing in both RA and SSc compared to healthy women. Unexpectedly, skewed XCI occurs more often in women with RA carrying the shared epitope, which usually reflects severe disease. This reinforces the view that loss of mosaicism in peripheral blood may be a consequence of chronic autoimmunity.

Prediction of work metabolism from heart rate measurements in forest work: some practical methodological issues

Individual heart rate (HR) to workload relationships were determined using 93 submaximal step-tests administered to 26 healthy participants attending physical activities in a university training centre (laboratory study) and 41 experienced forest workers (field study). Predicted maximum aerobic capacity (MAC) was compared to measured MAC from a maximal treadmill test (laboratory study) to test the effect of two age-predicted maximum HR Equations (220-age and 207-0.7 × age) and two clothing insulation levels (0.4 and 0.91 clo) during the step-test. Work metabolism (WM) estimated from forest work HR was compared against concurrent work V̇O2 measurements while taking into account the HR thermal component. Results show that MAC and WM can be accurately predicted from work HR measurements and simple regression models developed in this study (1% group mean prediction bias and up to 25% expected prediction bias for a single individual). Clothing insulation had no impact on predicted MAC nor age-predicted maximum HR equations. Practitioner summary: This study sheds light on four practical methodological issues faced by practitioners regarding the use of HR methodology to assess WM in actual work environments. More specifically, the effect of wearing work clothes and the use of two different maximum HR prediction equations on the ability of a submaximal step-test to assess MAC are examined, as well as the accuracy of using an individual's step-test HR to workload relationship to predict WM from HR data collected during actual work in the presence of thermal stress.

Felty's syndrome and hypofibrinogenemia: an unusual target for anti-cyclic citrullinated peptide antibodies?

BACKGROUND

Rheumatoid arthritis (RA) is a risk factor for the development of Felty's syndrome and large granular lymphocyte (LGL) leukemia. Anti-cyclic citrullinated peptide (CCP) antibodies are considered highly specific for RA and are directed against various citrullinated antigens, including citrullinated fibrinogen. Anti-CCP antibodies may interfere with the detection of citrullinated proteins and their function. In this article, we describe the possible inhibition of fibrinogen by anti-CCP antibodies with clinical consequences which have never been reported in the literature to our best knowledge.

CASE REPORT

We present the case of a 79-year-old Caucasian woman with a longstanding history of untreated seropositive RA and who had been investigated for severe neutropenia since several months. The association of splenomegaly led to suspicion of Felty's syndrome. Flux cytometry was compatible with T-cell LGL leukemia. In addition, severe hypofibrinogenemia was detected. The later finding has not been consistently associated with the former clinical entities. Further investigations demonstrated that the anti-CCP antibodies of the patient also recognized the P41 peptide of citrullinated fibrinogen. The patient deceased of intracranial hemorrhage.

CONCLUSION

It is likely, yet not definite, that high anti-citrullinated fibrinogen titers may contribute to low fibrinogen levels and could have contributed to the fatal hemorrhagic event.

New autoantibodies in early rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease causing articular cartilage and bone destruction. Since irreversible joint destruction can be prevented by intervention at the early stages of disease, early diagnosis of RA is important. In this study, we identified new autoantibodies in the sera of patients with early (less than one year) RA.

METHODS

We screened the sera of 20 RA patients with disease duration less than one year, 19 RA patients with disease duration more than five years and 23 controls on 8,268 human protein arrays. We confirmed the validity of protein array detection by ELISA assays. We then performed epitope mapping with overlapping 15-mers to analyze RA sera reactivity.

RESULTS

WIBG (within BGCN homolog (Drosophila)), GABARAPL2 (GABA(A) receptor associated protein like 2) and ZNF706 (zinc finger protein 706) proteins are preferentially recognized by autoantibodies from early RA patients. Of interest, autoantibodies to WIBG are very specific for early RA. Indeed, 33% of early RA patients' sera recognize WIBG versus 5% of RA patients with disease duration more than 5 years and 2% of controls. We identified three linear peptides on WIBG GABARAPL2 and ZNF706 that are preferentially recognized by sera of early RA patients.

CONCLUSIONS

We identified new autoantibodies associated with RA with disease duration less than one year. These autoantibodies could be used as diagnosis markers in RA patients.

HLA-DRB1 genotypes and the risk of developing anti citrullinated protein antibody (ACPA) positive rheumatoid arthritis

OBJECTIVE

To provide a table indicating the risk for developing anti citrullinated protein antibody (ACPA) positive rheumatoid arthritis (RA) according to one's HLA-DRB1 genotype.

METHODS

We HLA-DRB1 genotyped 857 patients with ACPA positive RA and 2178 controls from South Eastern and Eastern France and calculated Odds Ratios (OR) for developing RA for 106 of 132 possible genotypes accounting for 97% of subjects.

RESULTS

HLA-DRB1 genotypic ORs for developing ACPA positive RA range from 28 to 0.19. HLA-DRB1 genotypes with HLA-DRB1*04SE (HLA-DRB1*0404, HLA-DRB1*0405, HLA-DRB1*0408), HLA-DRB1*04∶01, HLA-DRB1*01 are usually associated with high risk for developing RA. The second HLA-DRB1 allele in genotype somewhat modulates shared epitope associated risk. We did not identify any absolutely protective allele. Neither the Reviron, nor the du Montcel models accurately explains our data which are compatible with the shared epitope hypothesis and suggest a dosage effect among shared epitope positive HLA-DRB1 alleles, double dose genotypes carrying higher ORs than single dose genotypes.

CONCLUSION

HLA-DRB1 genotypic risk for developing ACPA positive RA is influenced by both HLA-DRB1 alleles in genotype. We provide an HLA-DRB1 genotypic risk table for ACPA positive RA.

Autoantibodies to PAD4 and BRAF in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes cartilage and bone destruction. The mechanisms leading to RA are unknown. There is currently no reliable cure for RA. Early treatment can reduce inflammation, joint damage and bone destruction. Thus, early diagnosis of RA is critical. However, definitive diagnosis of RA can be difficult. Immunologic tests that can be performed for the diagnosis of RA include detection of anti citrullinated protein antibodies (ACPAs). However, one third of RA patients have no ACPAs. To identify new autoantibodies in RA, we used the sera of RA patients to screen protein arrays containing 8000 human proteins. We found and validated two major autoantigens: PAD4 (peptidyl arginine deiminase 4) and BRAF (v raf murine sarcoma viral oncogene homolog B1) catalytic domain. We identified peptide targets of anti PAD4 and BRAF autoantibodies. We observed that anti PAD4 are inhibitory whereas anti BRAF stimulate BRAF activity. Anti PAD4 and anti BRAF antibodies may be used to diagnose RA, particularly in the absence of anti citrullinated protein antibodies.

Autoantibodies to BRAF, a new family of autoantibodies associated with rheumatoid arthritis

Introduction

BRAF (v raf murine sarcoma viral oncogene homologue B1) is a serine-threonine kinase involved in the mitogen-activated protein kinase (MAPK) signalling pathway, known to be implicated in the production of pro-inflammatory cytokines.

We have observed that sera from rheumatoid arthritis (RA) patients recognize the BRAF's catalytic domain, which encompasses amino acids 416 to 766. Here, we identify peptide targets of anti-BRAF autoantibodies and test whether anti-BRAF autoantibodies may interfere with BRAF kinase activity.

Methods

Anti-BRAF autoantibodies were detected by ELISA (enzyme-linked immunosorbent assay) in the serum of RA patients and controls, using 40 overlapping 20mer peptides encompassing the catalytic domain of BRAF as immunosorbents. To test whether autoantibodies to BRAF influence BRAF kinase activity, we developed an in vitro phosphorylation assay of MEK1 (mitogen extracellular regulated kinase), a major BRAF substrate. MEK1 phosphorylation by BRAF was tested in the presence of purified anti-BRAF autoantibodies from RA patients or control antibody.

Results

We found that one BRAF peptide, P25 (656 to 675), is specifically recognized by autoantibodies from RA patients. Of interest, anti-P25 autoantibodies are detected in 21% of anti-CCP (cyclic citrullinated peptides) negative RA patients. Anti-BRAF autoantibodies activate the in vitro phosphorylation of MEK1 mediated by BRAF.

Conclusions

Anti-BRAF autoantibodies from RA patients preferentially recognize one BRAF peptide: P25. Autoantibody responses to P25 are detected in 21% of anti-CCP negative RA patients. Most anti-BRAF autoantibodies activate BRAF kinase activity.

Rheumatoid arthritis-specific autoantibodies to peptidyl arginine deiminase type 4 inhibit citrullination of fibrinogen

OBJECTIVE

Autoantibodies to citrullinated proteins are specific for rheumatoid arthritis (RA) and recognize epitopes centered by citrulline, a posttranslationally modified form of arginine. Peptidyl arginine deiminase type 4 (PAD-4), the enzyme that converts arginine into citrulline, is in itself a target for RA-specific autoantibodies. This study was undertaken to assess whether anti-PAD-4 autoantibodies interfere with citrullination in vitro in patients with RA, and to identify peptide targets of anti-PAD-4 antibodies that can activate or inhibit citrullination.

METHODS

To test whether autoantibodies to PAD-4 influence citrullination, an in-house citrullination assay was developed using purified autoantibodies to PAD-4. To map B cell epitopes on PAD-4, 65 overlapping 20-mer peptides encompassing the entire PAD-4 were analyzed for their reactivity in RA sera.

RESULTS

Autoantibodies to PAD-4 inhibited PAD-4-mediated citrullination. Three linear peptides on PAD-4 were recognized almost uniquely by PAD-4 autoantibodies in the sera of patients with RA. One peptide was located in the N-terminal, calcium-binding domain of PAD-4, while 2 other peptides were located in the C-terminal, substrate-binding domain of PAD-4.

CONCLUSION

Autoantibodies to PAD-4 inhibit in vitro citrullination of fibrinogen by PAD-4. Most anti-PAD-4-positive sera recognize peptides located both in the N-terminal domain (211-290) and the C-terminal domain (601-650) of PAD-4.

Transfer of the shared epitope through microchimerism in women with rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is an autoimmune disease that affects mostly women and is associated with HLA-DRB1 genes having in common a shared epitope sequence. In parallel, cells and/or DNA originating from pregnancy (microchimerism) persist for decades and could contribute to autoimmunity. The aim of this study was to examine whether microchimerism may be a source of the shared epitope among women with RA.

METHODS

Women with RA and healthy women who lacked RA-associated genes such as HLA-DRB1*01 (n=33 and n=46, respectively) and/or HLA-DRB1*04 (n=48 and n=64, respectively), were tested for DRB1*01 or DRB1*04 microchimerism by HLA-specific quantitative polymerase chain reaction assays. As controls, alleles not associated with RA (DQB1*02 and DRB1*15/16) were also analyzed.

RESULTS

Compared with healthy women, women (42% with RA had a higher frequency and higher levels of DRB1*04 microchimerism versus 8%; P=0.00002) as well as DRB1*01 microchimerism (30% versus 4%; P=0.0015). Moreover, no difference in microchimerism was observed for alleles not associated with RA.

CONCLUSION

Women with RA had microchimerism with RA-associated HLA alleles, but not with non-RA-associated HLA alleles, more often and at higher levels compared with healthy women. These observations are the first to indicate that microchimerism can contribute to the risk of an autoimmune disease by providing HLA susceptibility alleles.

A phase II, open-label study of the efficacy and safety of imiquimod in the treatment of superficial and mixed infantile hemangioma

OBJECTIVES

To explore the efficacy and safety of imiquimod 5% cream as a treatment for infantile hemangioma.

DESIGN

Phase II, open-label, noncomparative study of imiquimod applied during 16 weeks, with posttherapy follow-up 16 weeks later (8 months total).

SETTING

Outpatient pediatric tertiary care referral center in Quebec, Canada.

PARTICIPANTS

Healthy infants up to 8.8 months of age with previously untreated, nonulcerated, proliferative superficial or mixed infantile hemangioma, excluding periorbital, or perineal localization, > or =100 cm2 in size.

INTERVENTION

Topical imiquimod applied three to seven times per week for 16 weeks to infantile hemangioma.

MAIN OUTCOME MEASURES

Lesion area, volume, depth (Doppler ultrasound), and color (erythema), serum drug, and interferon-alpha levels.

RESULTS

Sixteen infants (11 girls, 5 boys) with a mean age at entry of 4.1 months and mean lesion area of 32.89 cm2, and volume of 39.98 cm3 were enrolled. Two participants discontinued treatment early, one for an adverse event (crying upon application), the other because of the lack of compliance. Local skin reactions were consistent with those reported in adults. Two cases had a decrease and three had an increase in lesion parameters; otherwise no meaningful changes in lesion area, volume, or depth were observed. At the 4-month posttreatment visit, 11 of 14 subjects had improvement in erythema (marginal homogeneity test = 2.668, p = 0.008). Measured serum drug and interferon-alpha levels were low or undetectable.

CONCLUSIONS

Treatment of infants with infantile hemangioma with imiquimod up to seven times per week for 16 weeks was generally well tolerated with low systemic exposure. Improvement was observed in hemangioma coloration, but not lesion size, suggesting effects were limited to the superficial component.

New autoantigens in rheumatoid arthritis (RA): screening 8268 protein arrays with sera from patients with RA

OBJECTIVE

To identify new IgG autoantibodies in sera from patients with rheumatoid arthritis (RA).

METHODS

We tested serum samples from 19 patients with RA with given human leukocyte antigen (HLA)-DR genotypes, from 7 patients with spondylarthropathy, 2 patients with lupus, 4 patients with systemic sclerosis and 10 healthy individuals on 8268 human protein arrays.

RESULTS

We identified four antigens (peptidyl arginine deiminase 4 (PAD4), protein kinase Cbeta1 (PKCbeta1), phosphatylinositol 4 phosphate 5 kinase type II gamma (PIP4K2C) and v raf murine sarcoma viral oncogene homologue B1 catalytic domain (BRAF)) that were recognised almost uniquely by sera from patients with RA on protein arrays. Using purified proteins, we confirmed that PAD4 and BRAF are recognised almost uniquely by patients with RA.

CONCLUSION

We identified PAD4 and BRAF as RA specific autoantigens.

HLA-DRB1*0404 is strongly associated with high titers of anti-cyclic citrullinated peptide antibodies in rheumatoid arthritis

OBJECTIVE

To test whether the presence of RA associated HLA-DRB1*0101, HLA-DRB1*0401 and HLA-DRB1*0404 alleles individually influences anti-cyclic citrullinated peptide antibodies (anti-CCP) production.

METHODS

The frequency of anti-CCP antibodies was calculated in the sera of 260 RA patients expressing either two (double dose genotypes SE+/SE+), one (single dose genotypes SE+/SE-) or no RA associated HLA-DR alleles (SE-/SE-). Anti-CCP antibodies titers were also determined.

RESULTS

RA associated HLA-DR alleles are not mandatory for production of anti-CCP. We found that 68% of SE-/SE- patients were anti-CCP positive. There was no significant difference in anti-CCP between SE negative patient (SE-/SE-) and patients expressing at least one SE (SE+/SE+ and SE+/SE-) (p=0.140). We observed no statistical difference in anti-CCP between RA patients expressing one or two SE (82% vs. 77%, p=0.577). Among SE+/SE-patients, HLA-DRB1*0404 was associated with anti-CCP with a statistically significant difference compared with SE negative patients (90% anti-CCP positive, p=0.02). HLA-DRB1*0404 was also associated with high titers of anti CCP with a statistically significant difference compared with HLA-DRB1*0401 and HLA-DRB1*0101 patients (p=0.025).

CONCLUSIONS

The RA-associated HLA-DRB1*0404 allele was the most strongly associated with the presence of anti-CCP in RA sera. Moreover, HLA-DRB1*0404 patients had higher titers of anti CCP than patients with other RA associated HLA-DR alleles.

Influence of -308 A/G polymorphism in the tumor necrosis factor alpha gene on etanercept treatment in rheumatoid arthritis

OBJECTIVE

To determine whether the -308 A/G tumor necrosis factor alpha (TNFalpha) gene polymorphism can predict the outcome of etanercept therapy in 86 patients with rheumatoid arthritis (RA), as already observed in patients treated with infliximab.

METHODS

Eighty-six RA patients treated with etanercept were genotyped for -308 A/G TNFalpha gene polymorphism by polymerase chain reaction and melting curve analysis, using specific gene primers and probes. Patients were subdivided into group A (G/A genotype) and group G (G/G genotype). We compared clinical responses to etanercept between groups A and G after 6 months, using the Disease Activity Score in 28 joints (DAS28). After 12-month treatment, 48 of 86 patients were evaluated again.

RESULTS

Of 86 patients, 18 (21%) belonged in group A and 68 (79%) belonged in group G. After 6-month treatment, 55.6% of patients in group A and 82.4% of patients in group G had DAS28 improvement >1.2 (P = 0.027 by chi-square). The mean +/- SD DAS28 improvement was 1.69 +/- 1.31 in group A and 2.23 +/- 1.19 in group G (P = 0.098 by t-test). After 1-year treatment 48 patients were tested again: 10 (21%) belonged in group A and 38 (79%) belonged in group G. Forty percent of patients in group A and 87% in group G had DAS28 improvement >1.2 (P = 0.005 by chi-square). The mean +/- SD DAS28 improvement was 1.334 +/- 1.37 in group A and 2.29 +/- 1.47 in group G (Mann-Whitney U test = 115, P = 0.0057).

CONCLUSION

RA patients with a -308 G/G TNFalpha genotype respond to etanercept better than patients with a -308 A/G genotype.

Long-term treatment with methotrexate or tumor necrosis factor alpha inhibitors does not increase epstein-barr virus load in patients with rheumatoid arthritis

OBJECTIVE

We previously demonstrated that patients with rheumatoid arthritis (RA) have a 10-fold systemic Epstein-Barr virus (EBV) overload, very similar to that observed in healthy organ transplant recipients. Our objective was to monitor EBV load over time in patients with RA receiving methotrexate, infliximab, or etanercept to detect possible immunosuppression-associated EBV dysregulation, as described in posttransplant lymphoproliferative disease.

METHODS

The EBV load in the peripheral blood mononuclear cells (PBMCs) from 19 patients receiving methotrexate, 68 patients receiving infliximab, and 48 patients receiving etanercept was monitored for durations ranging from 6 months to 5 years using a real-time polymerase chain reaction assay previously developed for that purpose. The effect of treatment duration on EBV load and the link between the Disease Activity Score in 28 joints and EBV load were analyzed by generalized estimating equations.

RESULTS

Methotrexate tended to decrease EBV load over time, but this did not reach significance. Tumor necrosis factor alpha (TNFalpha) inhibitors did not significantly modify EBV load over time. Finally, high disease activity was significantly associated with high EBV load.

CONCLUSION

Long-term usage of methotrexate or TNFalpha inhibitors in patients with RA does not significantly influence EBV load in PBMCs.

HLA-DRB1*0404 is strongly associated with anticalpastatin antibodies in rheumatoid arthritis

OBJECTIVE

To test whether HLA-DR alleles influence the production of particular autoantibodies in rheumatoid arthritis (RA) patients, we screened synovial proteins with sera of RA patients homozygous for different HLA-DR alleles by using 2D blots. We found that sera of RA patients homozygous for HLA-DRB1*0404 recognised a 100-kDa synovial protein identified as calpastatin. We studied B and T cell epitopes on calpastatin and their association with HLA-DRB1*0404.

METHODS

The frequency of positive sera in patients expressing different RA-associated HLA-DR allele combinations was calculated by inhouse ELISA using purified synovial calpastatin or calpastatin peptides encompassing the entire calpastatin protein as immunosorbent. Interaction between calpastatin peptides and HLA-DR alleles was tested by a direct binding assay. T cell responses to calpastatin were measured in RA patients and controls.

RESULTS

We found that RA-associated HLA-DR alleles are associated with presence of autoantibodies to synovial calpastatin in RA patients' sera. HLA-DRB1*0404 is strongly associated with antisynovial calpastatin in RA sera. One linear B cell epitope is preferentially associated with HLA-DRB1*0404. Multiple peptides from calpastatin bind every tested HLA-DR allele associated or not with RA. Peptides from domain 1 and 4 of calpastatin are the best HLA-DR allele binders. The T cell response to calpastatin is frequent in RA patients and independent of the HLA-DR background.

CONCLUSIONS

HLA-DRB1*0404 is strongly associated with anticalpastatin antibodies in rheumatoid arthritis.

Epitopes of human fibrin recognized by the rheumatoid arthritis-specific autoantibodies to citrullinated proteins

Formation of the epitopes recognized by the rheumatoid arthritis (RA)-specific autoantibodies to citrullinated proteins (ACPA) on filaggrin and on the alpha- and beta-chains of fibrin, their synovial target, requires conversion of their arginyl residues into citrullyl residues, but is also affected by their amino-acyl environment. Using competition with five citrullinated filaggrin-derived peptides bearing major ACPA epitopes, we confirmed the close cross-reactivity between filaggrin and citrullinated fibrin. To identify the sequential epitopes recognized on fibrin by ACPA, 71 citrullinated 15-mer peptides derived from all the sites of the alpha- and beta-chains of fibrin harboring arginyl residues were tested by ELISA using ACPA-positive RA sera exhibiting different reactivity profiles to the five filaggrin peptides. We identified 18 fibrin-derived peptides bearing ACPA epitopes. Regarding the ability of fibrinogen arginyl residues to be citrullinated in vitro, 11 of the peptides likely correspond to in vivo targeted epitopes. Two out of them bear major epitopes and are located in the central globular domain of the protein. In the synovial tissue, fibrin citrullination and ACPA binding could impair fibrin degradation by plasmin. The immunological conflict between ACPA and fibrin could therefore sustain synovial inflammation not only via pro-inflammatory effector mechanisms but also via impairment of fibrinolysis.