Importance of 14-3-3eta, anti-CarP, and anti-Sa in the diagnosis of seronegative rheumatoid arthritis

Background/aim: Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial inflammation. The study aimed to assess serum 14-3-3eta, anti-CarP, and anti-Sa in seronegative RA (SNRA) patients who were treatment-naïve as well as in healthy subjects. This is the first study in the literature to examine these autoantibodies together in SNRA patients. Materials and methods: Forty-five treatment-naïve SNRA patients and 45 healthy subjects were recruited. Drugs change the levels of autoantibodies; therefore, patients who took any medication had been excluded from our study. Anti-carbamylated protein, anti-Sa, and 14-3-3eta were measured by using three different ELISA kits. Results: Median serum concentration of healthy controls in 14-3-3eta was 0.02 (0.02­0.27) ng/mL. Median serum concentration of SNRA patients in 14-3-3eta was 1.00 (0.48­1.28) ng/mL. Data were analyzed with Mann­Whitney U tests; the P-value was <0.001 in 14-3-3eta. Receiver operating characteristic (ROC) curve analysis showed that 14-3-3eta in SNR compared to healthy controls had a significant (P < 0.001) area under the curve (AUC) of 0.90 (95% confidence interval, 0.83­0.96). At a cutoff of ≥0.33 ng/mL, the ROC curve yielded a sensitivity of 88.9%, a specificity of 82.2%, a positive predictive value of 83.3%, and a negative predictive value of 88.1%. Conclusion: We found that 14-3-3eta can be used as a diagnostic marker in SNRA.

Gingival tissue, an extrasynovial source of malondialdehyde-acetaldehyde adducts, citrullinated and carbamylated proteins.

BACKGROUND AND OBJECTIVE: Postranslational modification of proteins can lead to the production of autoantibodies and loss of immune tolerance. This process has been hypothesised to be a critical factor in the pathogenesis of rheumatoid arthritis. The objective of this study was to demonstrate that inflamed human gingival tissue provides an extrasynovial source of malondialdehyde-acetaldehyde adducts, citrullinated and carbamylated proteins all of which are considered to be linked to the development of rheumatoid arthritis. Identification of such modified proteins in inflamed gingiva may explain, in part, how inflammation of the periodontal tissues may influence the development of rheumatoid arthritis. MATERIAL AND METHODS: Gingival biopsies of healthy, mild and moderate periodontitis were triple stained with antibodies against malondialdehyde-acetaldehyde adducts, citrullinated and carbamylated proteins. RESULTS: Assessment of healthy gingival tissue revealed negligible staining for carbamylated, malondialdehyde-acetaldehyde (MAA), or citrullinated proteins. Mild periodontitis was positive for all three modifications. Furthermore, there was an increase in staining intensity for carbamylated, citrullinated and MAA-modified proteins in moderate periodontitis. Negative staining results were observed for the isotype controls. CONCLUSION: This study provides evidence for the presence of citrullinated, carbamylated and MAA adduct modified proteins in inflamed periodontal tissues. The potential for these proteins to play a role in autoimmunity in a multi-system inflammatory syndromic disease model now needs to be determined.

The association between anti-carbamylated protein (anti-CarP) antibodies and radiographic progression in early rheumatoid arthritis: a study exploring replication and the added value to ACPA and rheumatoid factor.

OBJECTIVE: Anti-carbamylated protein (anti-CarP) antibodies are reported to associate with more radiographic progression within the total rheumatoid arthritis (RA) population and anti-citrullinated peptide antibody (ACPA)-negative subgroup. We explored the association of anti-CarP with radiographic progression in RA and aimed to replicate the association and evaluate the added value of anti-CarP antibodies in relation to ACPA and rheumatoid factor (RF). METHODS: 576 Swedish and 628 Dutch patients with RA (2394 and 3247 sets of radiographs, respectively) were longitudinally studied. Replication was restricted to the Swedish patients. In both cohorts, the association of anti-CarP with radiographic progression was determined in strata of patients with similar ACPA and RF status; results of both cohorts were combined in fixed-effect meta-analyses. The net percentage of patients for whom the radiographic progression in 5 years was additionally correctly classified when adding anti-CarP to a model including ACPA and RF was evaluated. RESULTS: Anti-CarP associated with radiographic progression in the total Swedish RA population (beta=1.11 per year, p=8.75×10-13) and in the ACPA-negative subgroup (beta=1.14 per year, p=0.034). Anti-CarP associated with more radiographic progression in the strata of ACPA-positive/RF-negative, ACPA-negative/RF-positive and ACPA-positive/RF-positive patients with RA (respective p values 0.014, 0.019 and 0.0056). A model including ACPA and RF correctly classified 54% and 57% of the patients; adding anti-CarP to this model did not increase these percentages (54% and 56% were correctly classified). CONCLUSIONS: Anti-CarP antibodies associated with more severe radiographic progression in the total and ACPA-negative RA population. Anti-CarP-positivity had a statistically significant additive value to ACPA and RF, but did not improve correct classification of patients.

Breach of autoreactive B cell tolerance by post-translationally modified proteins.

OBJECTIVES: Over 50% of patients with rheumatoid arthritis (RA) harbour a variety of anti-modified protein antibodies (AMPA) against different post-translationally modified (PTM) proteins, including anti-carbamylated protein (anti-CarP) antibodies. At present, it is unknown how AMPA are generated and how autoreactive B cell responses against PTM proteins are induced. Here we studied whether PTM foreign antigens can breach B cell tolerance towards PTM self-proteins. METHODS: Serum reactivity towards five carbamylated proteins was determined for 160 patients with RA and 40 healthy individuals. Antibody cross-reactivity was studied by inhibition experiments. Mass spectrometry was performed to identify carbamylated self-proteins in human rheumatic joint tissue. Mice were immunised with carbamylated or non-modified (auto)antigens and analysed for autoantibody responses. RESULTS: We show that anti-CarP antibodies in RA are highly cross-reactive towards multiple carbamylated proteins, including modified self-proteins and modified non-self-proteins. Studies in mice show that anti-CarP antibody responses recognising carbamylated self-proteins are induced by immunisation with carbamylated self-proteins and by immunisation with carbamylated proteins of non-self-origin. Similar to the data observed with sera from patients with RA, the murine anti-CarP antibody response was, both at the monoclonal level and the polyclonal level, highly cross-reactive towards multiple carbamylated proteins, including carbamylated self-proteins. CONCLUSIONS: Self-reactive AMPA responses can be induced by exposure to foreign proteins containing PTM. These data show how autoreactive B cell responses against PTM self-proteins can be induced by exposure to PTM foreign proteins and provide new insights on the breach of autoreactive B cell tolerance.

Antimodified protein antibody response pattern influences the risk for disease relapse in patients with rheumatoid arthritis tapering disease modifying antirheumatic drugs.

OBJECTIVE: To perform a detailed analysis of the autoantibody response against post-translationally modified proteins in patients with rheumatoid arthritis (RA) in sustained remission and to explore whether its composition influences the risk for disease relapse when tapering disease modifying antirheumatic drug (DMARD) therapy. METHODS: Immune responses against 10 citrullinated, homocitrullinated/carbamylated and acetylated peptides, as well as unmodified vimentin (control) and cyclic citrullinated peptide 2 (CCP2) were tested in baseline serum samples from 94 patients of the RETRO study. Patients were classified according to the number of autoantibody reactivities (0-1/10, 2-5/10 and >5/10) or specificity groups (citrullination, carbamylation and acetylation; 0-3) and tested for their risk to develop relapses after DMARD tapering. Demographic and disease-specific parameters were included in multivariate logistic regression analysis for defining the role of autoantibodies in predicting relapse. RESULTS: Patients varied in their antimodified protein antibody response with the extremes from recognition of no (0/10) to all antigens (10/10). Antibodies against citrullinated vimentin (51%), acetylated ornithine (46%) and acetylated lysine (37%) were the most frequently observed subspecificities. Relapse risk significantly (p=0.011) increased from 18% (0-1/10 reactivities) to 34% (2-5/10) and 55% (>5/10). With respect to specificity groups (0-3), relapse risk significantly (p=0.021) increased from 18% (no reactivity) to 28%, 36% and finally to 52% with one, two or three antibody specificity groups, respectively. CONCLUSIONS: The data suggest that the pattern of antimodified protein antibody response determines the risk of disease relapse in patients with RA tapering DMARD therapy. TRIAL REGISTRATION NUMBER: 2009-015740-42; Results.

Carbamylation of vimentin is inducible by smoking and represents an independent autoantigen in rheumatoid arthritis.

OBJECTIVES: Smoking has been connected to citrullination of antigens and formation of anti-citrullinated peptide antibodies (ACPAs) in rheumatoid arthritis (RA). Since smoking can modify proteins by carbamylation (formation of homocitrulline), this study was conducted to investigate these effects on vimentin in animal models and RA. METHODS: The efficiency of enzymatic carbamylation of vimentin was characterised. B-cell response was investigated after immunisation of rabbits with different vimentin isoforms. Effects of tobacco smoke exposure on carbamylation of vimentin and formation of autoantibodies were analysed in mice. The antibody responses against isoforms of vimentin were characterised with respect to disease duration and smoking status of patients with RA. RESULTS: Enzymatic carbamylation of vimentin was efficiently achieved. Subsequent citrullination of vimentin was not disturbed by homocitrullination. Sera from rabbits immunised with carbamylated vimentin (carbVim), in addition to carbVim also recognised human IgG-Fc showing rheumatoid factor-like reactivity. Smoke-exposed mice contained detectable amounts of carbVim and developed a broad immune response against carbamylated antigens. Although the prevalence of anti-carbamylated antibodies in smokers and non-smokers was similar, the titres of carbamylated antibodies were significantly increased in sera of smoking compared with non-smoking RA. CarbVim antibodies were observed independently of ACPAs in early phases of disease and double-positive patients for anti-mutated citrullinated vimentin (MCV) and anti-carbVim antibodies showed an extended epitope recognition pattern towards MCV. CONCLUSIONS: Carbamylation of vimentin is inducible by cigarette smoke exposure. The polyclonal immune response against modified antigens in patients with RA is not exclusively citrulline-specific and carbamylation of antigens could be involved in the pathogenesis of disease. TRIAL REGISTRATION NUMBER: ISRCTN36745608; EudraCT Number: 2006-003146-41.

Carbamylated albumin is one of the target antigens of anti-carbamylated protein antibodies.

Objectives: Anti-carbamylated protein (anti-CarP) antibodies are detected in RA patients. Fetal calf serum is used as an antigen source in anti-CarP ELISA, and the precise target antigens have not been found. We aimed to identify the target antigens of anti-CarP antibodies. Methods: Western blotting of anti-CarP antibodies was conducted. Anti-carbamylated human albumin (CarALB) antibody was detected by in-house ELISA for 493 RA patients and 144 healthy controls (HCs). An inhibition ELISA of anti-CarP antibodies by CarALB and citrullinated albumin (citALB) was performed using eight RA patients' sera. Serum CarALB was detected by liquid chromatography-tandem mass spectroscopy (LC/MS/MS), and the serum MPO concentration was measured by ELISA. Results: We focused on carbamylated albumin because it corresponded to the size of the thickest band detected by western blotting of anti-CarP antibodies. Anti-CarALB antibody was detected in 31.4% of RA patients, and the correlation of the titres between anti-CarALB and anti-CarP was much closer than that between anti-citALB and anti-CCP antibodies (ρ = 0.59 and ρ = 0.16, respectively). The inhibition ELISA showed that anti-CarP antibodies were inhibited by CarALB, but not by citALB. CarALB was detected in sera from RA patients by LC/MS/MS. The serum MPO concentration was correlated with disease activity and was higher in RA patients with anti-CarALB antibody than in those without. Conclusion: We found that carbamylated albumin is a novel target antigen of anti-CarP antibodies, and it is the first reported target antigen that has not been reported as the target of ACPA.

Effects of type II collagen epitope carbamylation and citrullination in human leucocyte antigen (HLA)-DR4(+) monozygotic twins discordant for rheumatoid arthritis.

The aim of this study is to investigate the effect of the native, citrullinated or carbamylated type II human collagen T cell- and B cell-epitopes on the adaptive immune response in rheumatoid arthritis (RA). Peripheral blood T and B cells obtained from a human leucocyte D4-related (antigen DR4(-) HLA-DR4)(+) woman with early RA, her healthy monozygotic twin and an unrelated HLA-DR3(+) woman with early RA were analysed for activation (CD154/CD69), apoptosis (annexin/7-aminoactinomycin), cytokine production [interferon (IFN)γ/interleukin (IL)-17/IL-4/IL-10/IL-6] and functional phenotype (CD45Ra/CCR7) after stimulation with the collagen native T cell epitope (T261-273), the K264 carbamylated T cell epitope (carT261-273), the native B cell epitope (B359-369) or the R360 citrullinated B cell epitope (citB359-369), and the combinations of these. The T cell memory compartment was activated by T cell epitopes in both discordant DR4(+) twins, but not in the DR3(+) RA. The collagen-specific activation of CD4(+) T cells was induced with both the native and carbamylated T cell epitopes only in the RA twin. Both T cell epitopes also induced IL-17 production in the RA twin, but a greater IL-4 and IL-10 response in the healthy twin. The citrullinated B cell epitope, particularly when combined with the carbamylated T cell epitope, induced B cell activation and an increased IL-6/IL-10 ratio in the RA twin compared to a greater IL-10 production in the healthy twin. Our data suggest that circulating collagen-specific T and B cells are found in HLA-DR4(+) subjects, but only RA activated cells express co-stimulatory molecules and produce proinflammatory cytokines. Carbamylation and citrullination further modulate the activation and cytokine polarization of T and B cells.

Anticarbamylated protein antibodies are associated with long-term disability and increased disease activity in patients with early inflammatory arthritis: results from the Norfolk Arthritis Register.

OBJECTIVES: Anticarbamylated protein (anti-CarP) antibodies are a novel family of autoantibodies recently identified in patients with inflammatory arthritis. The aim of this study was to investigate their association with long-term outcomes of disability and disease activity over 20 years' follow-up in a cohort of patients with inflammatory polyarthritis (IP). METHODS: Norfolk Arthritis Register recruited adults with recent-onset swelling of ≥2 joints for ≥4 weeks from 1990 to 2009. At baseline, Health Assessment Questionnaire (HAQ) and 28 joint disease activity scores (DAS28) were obtained, and C reactive protein, rheumatoid factor (RF), anticitrullinated protein antibodies (ACPA) and anti-CarP antibodies were measured. Further HAQ scores and DAS28 were obtained at regular intervals over 20 years. Generalised estimating equations were used to test the association between anti-CarP antibody status and longitudinal HAQ and DAS28 scores; adjusting for age, gender, smoking status, year of inclusion and ACPA status. Analyses were repeated in subgroups stratified by ACPA status. The relative association of RF, ACPA and anti-CarP antibodies with HAQ and DAS28 scores was investigated using a random effects model. RESULTS: 1995 patients were included; 1310 (66%) were female. Anti-CarP antibodies were significantly associated with more disability and higher disease activity, HAQ multivariate ß-coefficient (95% CI) 0.12 (0.02 to 0.21), and these associations remained significant in the ACPA-negative subgroups. The associations of RF, ACPA and anti-CarP antibodies were found to be additive in the random effects model. CONCLUSIONS: Anti-CarP antibodies are associated with increased disability and higher disease activity in patients with IP. Our results suggest that measurement of anti-CarP antibodies may be useful in identifying ACPA-negative patients with worse long-term outcomes. Further, anti-CarP antibody status provided additional information about RF and ACPA.

Antibodies against carbamylated proteins are present in primary Sjögren's syndrome and are associated with disease severity.

OBJECTIVES: Herein, we investigate the presence and prognostic value of autoantibodies against carbamylated proteins (anti-CarP) in the serum of patients with primary Sjögren's syndrome (pSS). PATIENTS AND METHODS: Serum levels of anti-CarP antibodies were measured in Norwegian patients with pSS (n=78) and corresponding controls (n=74) using ELISA and analysed in relation with exocrine gland function, degree of salivary gland inflammation, signs of ectopic germinal centre (GC) formation and immunological markers. For univariate comparisons, the Mann-Whitney U test and χ(2) or Fisher's exact tests were used. Correlations were assessed with Spearman's rank testing. Multivariate regression analyses were used to assess the effect of anti-CarP positivity on clinical manifestations. RESULTS: Of the patients with pSS, 27% were positive for anti-CarP IgG antibodies. Levels of anti-CarP correlated positively with total IgG, IgM, rheumatoid factor and ß2-microglobulin. Importantly, after adjusting for confounding factors, patients positive for anti-CarP had significantly higher focus score. Furthermore, positive anti-CarP status coincided with 9.2-fold higher odds of having developed GC-like structures in the minor salivary glands. As a patient group considered having worse disease outcome, individuals with ectopic GC-like structures also presented with significantly higher levels of anti-CarP antibodies. CONCLUSIONS: Presence of anti-CarP in patients with pSS is strongly associated with increased focal lymphocytic infiltration, formation of ectopic GC-like structures in minor salivary glands, and diminished salivary gland function. Even taking into consideration our relatively small cohort we believe that anti-CarP antibodies offer new possibilities for identifying patients with more active disease and at risk of developing additional comorbidity.

Anti-carbamylated protein antibodies in unaffected first-degree relatives of rheumatoid arthritis patients: lack of correlation with anti-cyclic citrullinated protein antibodies and rheumatoid factor.

OBJECTIVES: To investigate the prevalence of anti-carbamylated protein antibodies (anti-CarP) in the healthy first-degree relatives (HFDRs) of patients with rheumatoid arthritis (RA). METHODS: We enrolled 141 HFDRs of 63 patients with RA diagnosed accordingly to the 2010 ACR/EULAR criteria. Fifty-six normal healthy subjects (NHS), sex- and age-matched, served as controls. Anti-CarP IgG, anti-cyclic citrullinated peptide antibody (anti-CCP) IgG and rheumatoid factors (RF) isotypes (IgG, IgA, IgM) were assessed by solid-phase ELISA. RESULTS: Anti-CarP were detectable in 13 HFDRs (9.2%), anti-CCP in 9 (6.3%), IgG-RF in 10 (7%), IgA-RF in 17 (12%), and IgM-RF in 13 (9.2%) HFDRs. Twenty-nine (46%) RA patients were positive for anti-CarP, 31 (49.2%) for anti-CCP, and 34 (53.9%) for RF. One NHS (1.7%) resulted positive for anti-CarP, none for anti-CCP and RF. Anti-CarP showed significantly higher serum levels in RA and HFDRs than in NHS (p<0.0001 and p=0.0012, respectively). A significant correlation between anti-CCP and RF were found among RA patients (p=0.0002), whereas no correlations were reported between autoantibodies tested in the HFDRs. CONCLUSIONS: Anti-CarP can be found in the sera of HFDRs of RA patients and their prevalence is significantly higher than in NHS. No correlation of anti-CarP with anti-CCP and RF antibodies in RA HFDRs was found.

Anti-carbamylated protein (anti-CarP) antibodies precede the onset of rheumatoid arthritis.

OBJECTIVE: The presence of anti-citrullinated protein antibodies (ACPA) and IgM-rheumatoid factor (IgM-RF) years before the clinical diagnosis of rheumatoid arthritis (RA) suggests they are possibly involved in the pathogenic process underlying RA. In this study, we analysed whether anti-carbamylated protein (anti-CarP) antibodies, a novel autoantibody system against carbamylated proteins, can also be detected in healthy individuals before they developed RA. METHODS: Multiple sera from asymptomatic blood donors prior to the onset of their RA symptoms and sera from age-matched and sex-matched controls were tested for the presence of antibodies directed against carbamylated-fetal calf serum (Ca-FCS), carbamylated-fibrinogen (Ca-Fib), cyclic citrullinated-peptide 2 and IgM-RF. RESULTS: Anti-Ca-FCS and anti-Ca-Fib antibodies were each present in 27% and 38% of the last serum samples of blood donors prior to the diagnosis of RA. Both anti-Ca-FCS and anti-Ca-Fib antibodies could be detected many years before the onset of RA. Anti-CarP antibodies as well as ACPA are, on average, detected earlier than IgM-RF. CONCLUSIONS: In addition to ACPA and IgM-RF, also the newly identified anti-CarP antibodies appear many years before the diagnosis of RA.

Anti-carbamylated protein antibodies are present in arthralgia patients and predict the development of rheumatoid arthritis.

OBJECTIVE: Recently, we discovered a new autoantibody system in rheumatoid arthritis (RA): anti-carbamylated protein (anti-CarP) antibodies. These antibodies have value in predicting joint destruction; however, it is not clear whether they are present before the diagnosis of RA and whether they have value as predictors of RA development. Therefore, we studied whether anti-CarP antibodies are present in patients with arthralgia and whether their presence is associated with the development of RA. METHODS: Sera from 340 arthralgia patients who did not have clinical signs of arthritis but who were positive for IgM rheumatoid factor (IgM-RF) and/or anti-cyclic citrullinated peptide 2 (anti-CCP-2) and 32 healthy controls were tested for anti-CarP IgG antibodies. Of the patients with arthralgia, 111 were IgM-RF positive/anti-CCP-2 antibody negative and 229 were anti-CCP-2 antibody positive. Patients were observed for the development of RA (based on the 2010 American College of Rheumatology/European League Against Rheumatism classification criteria) during a median followup period of 36 months. Cox proportional hazards regression analysis was performed to compare the risk of developing RA between arthralgia patients who were positive for anti-CarP antibodies and those who were negative for anti-CarP antibodies during followup. RESULTS: Anti-CarP antibodies were present in the sera of 39% of the patients. One hundred twenty patients developed RA, after a median of 12 months (interquartile range [IQR] 6-24). The presence of anti-CarP antibodies was associated with the development of RA in the entire arthralgia cohort after correction for RF and anti-CCP-2 antibody status (hazard ratio 1.56 [95% confidence interval 1.06-2.29], P=0.023), as well as in the anti-CCP-2 antibody-positive subgroup (odds ratio 2.231 [95% confidence interval 1.31-3.79], P=0.003). CONCLUSION: Anti-CarP antibodies are present in patients with arthralgia, and their presence predicts the development of RA independent of anti-CCP-2 antibodies.

Direct surface plasmon resonance immunosensing of pyraclostrobin residues in untreated fruit juices.

A surface plasmon resonance (SPR) immunoassay for on-line detection of the strobilurin fungicide pyraclostrobin in untreated fruit juices is presented. The analysis of pyraclostrobin residues is accomplished in apple, grape, and cranberry samples by monitoring the recognition events occurring separately in a two-channel home-made SPR biosensor. Covalent coupling of the analyte derivative results in a reversible method, enabling more than 80 measurements on the same sensor surface. Optimization of the immunoassay conditions provides limits of detection as low as 0.16 µg L(-1). The selectivity and reproducibility of the analysis is ensured by studying both non-specific interactions with unrelated compounds and inter-assay coefficients of variation. Excellent recovery ranging from 98 to 103% was achieved by a simple 1:5 dilution of fruit juice with assay buffer before the analysis. The lack of previous cleaning and homogenization procedures reduces the analysis time of a single food sample to only 25 min, including the regeneration cycle.

Synthesis of site-heterologous haptens for high-affinity anti-pyraclostrobin antibody generation.

The design and synthesis of functional chemical derivatives of small organic molecules is usually a key step for the intricate production of a variety of bioconjugates. In this respect, the derivatization site at which the spacer arm is introduced in immunizing conjugates constitutes a highly critical parameter for the generation of high-affinity and selective antibodies. However, due to the usual complexity of the required synthetic procedures, the appropriate comparison of alternative tethering positions has often been neglected. In the present study, meticulous strategies were followed to prepare synthetic derivatives of pyraclostrobin with the same linkers located at diverse rationally-chosen sites. Activity appraisal of antibodies and bioconjugates was carried out by bidimensional competitive direct and indirect immunoassays, and a superior performance of two of the three synthesized haptens was found. Finally, a detailed analysis of the conformations of the target molecule and the synthesized haptens in aqueous solution was done using computer assisted molecular modeling techniques. This study suggested that the lower titers and affinities of one set of antibodies are most probably due to conformational effects of the spacer arm in the immunizing bioconjugate.

Hypersensitivity to repaglinide.

Meglitinides (repaglinide and nateglinide) are insulin secretagogues used to treat diabetes mellitus. We present a case of hypersensitivity reaction to repaglinide in a 61-year-old man who developed a maculopapular rash 5 days after treatment. Skin prick tests including repaglinide (0.5 g/mL) and patch tests (0.05% in pet and saline) were performed, and the results were negative. A blind oral challenge test with repaglinide was performed and the therapeutic dose was subsequently taken at home every 24 hours for 7 days. The result was positive with a delayed reaction at day 3. A punch biopsy of the skin lesions revealed drug-induced exanthema. The clinical manifestations, the latency period, the reappearance of cutaneous lesions after rechallenge, and the histopathology report of the skin biopsy suggest a type IV mechanism.