Neutrophil anti-neutrophil cytoplasmic autoantibody proteins: bactericidal increasing protein, lactoferrin, cathepsin, and elastase as serological markers of inflammatory bowel and other diseases

Level and avidity of antineutrophil cytoplasmic antibodies specific to lactoferrin are useful biomarkers in systemic lupus erythematosus

OBJECTIVES

To evaluate specificity, level, and avidity of antineutrophil cytoplasmic antibodies (ANCA) in systemic lupus erythematosus (SLE). There are no studies of ANCA avidity in SLE.

METHODS

Level (ELISA) and avidity (ELISA) of myeloperoxidase (MPO-), proteinase 3 (PR3-), lactoferrin (LF-), cathepsin G, elastase (EL-), and bactericidal/permeability increasing protein (BPI)-ANCA in 142 SLE patients were studied. SLE activity was measured by SLEDAI-2 K. 25/40 ANCA-positive patients were immunoserologically followed (12 ± 2 months).

RESULTS

40/142 (28.2%) SLE patients were ANCA-positive: LF- (21/40), MPO- (19/40), EL- (6/40), PR3- (3/40), and BPI-ANCA (1/40). Only LF-ANCA were associated with renal manifestations (p < 0.05), and positive predictive value for renal involvement in ANCA-positive SLE was 76.2%. LF-ANCA-positive patients had higher SLEDAI-2 K (p < 0.05) and more frequently had anti-dsDNA (p < 0.05), low C3 (p < 0.001), and low C4 (p < 0.05) than LF-ANCA-negative patients. LF-ANCA level was in a positive correlation with SLEDAI-2 K, anti-dsDNA, and anti-C1q (p < 0.01) and in a negative correlation with C3 and C4 (p < 0.05). LF-ANCA avidity was higher than MPO-, EL-, PR3-, and BPI-ANCA avidity (p < 0.01). In LF-ANCA-positive patients, renal manifestations were associated with higher LF-ANCA level (p < 0.01) and avidity (p < 0.05). Based on LF-ANCA level and avidity, the receiver operating characteristic curves for discriminating patients with and without renal involvement had areas under the curves of 0.988 (95% CI: 0.949-1.00) and 0.813 (95% CI: 0.607-1.00), respectively. After the follow-up period, number of LF-ANCA-positive patients decreased (p < 0.01).

CONCLUSIONS

In contrast to other ANCAs, only LF-ANCA level correlated with activity and standard serological SLE markers. LF-ANCA level and avidity might be biomarkers of renal involvement in SLE. LF-ANCA are promising serological marker in SLE. Key Points • LF- and MPO-ANCA were most frequently found, while EL-, PR3-, and BPI-ANCA were rarely detected in SLE. • In contrast to other ANCAs, only LF-ANCA were associated with renal involvement, and their level correlated with the activity and standard serological markers of SLE. • LF-ANCA avidity was higher than other ANCAs' avidity; LF-ANCA level and avidity might be useful biomarkers of renal manifestations in SLE. • Detection of ANCA specificity, level, and avidity may help in the diagnosis of particular clinical SLE phenotypes.

Unclassifiable repeated antineutrophil cytoplasmic antibody (ANCA) positivity in diseases other than ANCA-associated vasculitis

BACKGROUND AND OBJECTIVE

Antineutrophil cytoplasmic antibody (ANCA) is a specific autoantibody for ANCA-associated vasculitis (AAV). However, ANCA can be detected in various diseases other than AAV. Hence, in this study, we investigated and provided the name of diseases with repeated ANCA positivity and the frequency of each disease other than AAV.

METHODS

We retrospectively screened the results of the tests of ANCA in 26,499 patients using the Clinical Data Repository System and included in this study only 173 patients with repeated ANCA positivity more than twice. 'Unclassifiable ANCA' was defined when ANCA was detected in patients with diseases other than AAV. 'Unclassifiable repeated ANCA' was also defined when unclassifiable ANCA was successively detected more than twice.

RESULTS

Among rheumatic and autoimmune diseases, the most common disease with unclassifiable repeated ANCA was vasculitis undetermined (21.0%). In terms of cardiovascular and cerebrovascular diseases, the most common disease with unclassifiable repeated ANCA was atherosclerotic heart disease (12.1%). In terms of disorders in liver, kidneys and lungs, the most common disease with unclassifiable repeated ANCA was chronic kidney disease (51 cases, 29.5%). In addition, among infections with confirmed infectious pathogens, the most common pathogen with unclassifiable repeated ANCA was varicella-zoster virus (6.9%) followed by Candida (4.6%).

CONCLUSION

Overall, regardless of category, the common diseases with unclassifiable repeated ANCA were chronic kidney disease followed by interstitial lung disease and vasculitis undetermined. Thus, we carefully suggest that physicians should pay more attention to the development of AAV or vasculitis other than AAV and, furthermore, kidneys and lungs should be monitored regularly and closely in patients with unclassifiable repeated ANCA.

MRP8/14 and neutrophil elastase for predicting treatment response and occurrence of flare in patients with juvenile idiopathic arthritis

Objective

To study two neutrophil activation markers, myeloid-related protein (MRP) 8/14 and neutrophil elastase (NE), for their ability to predict treatment response and flare in patients with JIA.

Methods

Using samples from two cohorts (I and II), we determined MRP8/14 and NE levels of 32 (I) and 81 (II) patients with new-onset, DMARD-naïve arthritis and compared patients who responded to treatment (defined as fulfilling ≥ adjusted ACRpedi50 response and/or inactive disease) with non-responders (defined as fulfilling < adjusted ACRpedi50 response and/or active disease) at 6 and 12 months. Secondly, we compared biomarker levels of 54 (I) and 34 (II) patients with clinically inactive disease who did or did not suffer from a flare of arthritis after 6 or 12 months. Receiver operating characteristic analyses were carried out to study the predictive value of MRP8/14 and NE for treatment response and flare.

Results

For both cohorts, baseline MRP8/14 and NE levels for patients who did or did not respond to treatment were not different. Also, MRP8/14 and NE levels were not different in patients who did or did not flare. Receiver operating characteristic analysis of MRP8/14 and NE demonstrated areas under the curve <0.7 in both cohorts.

Conclusion

In our cohorts, MRP8/14 and NE could not predict treatment response. Also, when patients had inactive disease, neither marker could predict flares.

Lack of elevated pre-ART elastase-ANCA levels in patients developing TB-IRIS

Background

Tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) in HIV-TB co-infected patients receiving antiretroviral therapy (ART) has been linked to neutrophil activation. Anti-neutrophil cytoplasmic antibodies (ANCAs) are also associated with neutrophil activation. Since ANCAs are reportedly skewed in TB and HIV infections, we investigated plasma levels of 7 ANCAs in TB-IRIS patients.

Methods

We retrospectively compared 17 HIV-TB patients who developed TB-IRIS with controls of similar CD4 count, age and gender who did not (HIV⁺TB⁺ n = 17), HIV-infected patients without TB (HIV⁺TB^-, n = 17) and 10 HIV-negative (HIV^-TB^-) controls. Frozen plasma was collected before ART, at 3 and 9 months of ART, and examined by ELISA for levels of 7 ANCAs directed against; Proteinase 3 (PR3), Myeloperoxidase (MPO), Permeability-increasing protein (BPI), Elastase, Cathepsin, Lysozyme, and Lactoferrin.

Results

Compared to HIV⁺TB⁺ controls, pre-ART anti-elastase levels were lower in TB-IRIS patients (p = 0.026) and HIV^-TB^- controls (p = 0.044), whereas other ANCAs did not show significant differences between groups at any time point. A significant decrease over time could be observed in TB-IRIS patients during ART for anti -PR3 (p = 0.027), -lysozyme (p = 0.011), and -lactoferrin (p = 0.019). Conversely, HIV⁺TB⁺ controls showed a significant decrease over time for anti -MPO (p = 0.002), -lyzosyme (p = 0.002) and -elastase (p < 0.001).

Conclusion

The lack of elevated anti-elastase levels in TB-IRIS patients as opposed to HIV⁺TB⁺ controls correspond to previous findings of lowered immune capacity in patients that will develop TB-IRIS. This may suggest a specific role for anti-elastase, elastase or even matrix-metalloproteinases in TB-IRIS. The precise dynamics of neutrophil activation in HIV-TB merits further investigation and could provide more insight in the early mechanisms leading up to TB-IRIS.

An international survey on anti-neutrophil cytoplasmic antibodies (ANCA) testing in daily clinical practice

Background:

Detection of anti-neutrophil cytoplasmic antibodies (ANCA) is important for the diagnosis of the ANCA-associated vasculitides (AAV). For AAV, especially ANCA directed against myeloperoxidase (MPO) and proteinase 3 (PR3) are most relevant. ANCA with less well-defined specificities may, however, also be detected in other inflammatory and non-inflammatory conditions.

Methods:

A questionnaire, initiated by the European Autoimmunity Standardisation Initiative (EASI), was used to gather information on methods and testing algorithms used for ANCA in clinical laboratories of 12 European countries (EASI survey).

Results:

Four hundred and twenty-nine responses were included in the EASI survey analysis which revealed differences within countries and between countries. Laboratories overall were poor in adherence to international consensus on ANCA testing. Substantial variation was observed with respect to the use of ANCA indirect immunofluorescence (IIF) in the algorithm, application of distinct methods for MPO- and PR3-ANCA, the daily availability of new ANCA results, and interpretation of test results.

Conclusions:

Awareness of these differences may stimulate further harmonization and standardization of ANCA testing. This may be promoted by an update of the international ANCA consensus and the introduction of international standards.

Use of a Granulocyte Immunofluorescence Assay Designed for Humans for Detection of Antineutrophil Cytoplasmic Antibodies in Dogs with Chronic Enteropathies

BACKGROUND

Perinuclear antineutrophil cytoplasmic antibodies (pANCA) previously have been shown to be serum markers in dogs with chronic enteropathies, with dogs that have food-responsive disease (FRD) having higher frequencies of seropositivity than dogs with steroid-responsive disease (SRD). The indirect immunofluorescence (IIF) assay used in previous publications is time-consuming to perform, with low interobserver agreement.

HYPOTHESIS/OBJECTIVES

We hypothesized that a commercially available granulocyte IIF assay designed for humans could be used to detect perinuclear antineutrophil cytoplasmic antibodies in dogs.

ANIMALS

Forty-four dogs with FRD, 20 dogs with SRD, 20 control dogs, and 38 soft-coated wheaten terrier (SCWT) or SCWT-cross dogs.

METHODS

A granulocyte assay designed for humans was used to detect pANCA, cANCA, and antinuclear antibodies (ANA), as well as antibodies against proteinase-3 protein (PR-3) and myeloperoxidase protein (MPO) in archived serum samples.

RESULTS

Sensitivity of the granulocyte assay to predict FRD in dogs was 0.61 (95% confidence interval (CI), 0.45, 0.75), and specificity was 1.00 (95% CI, 0.91, 1.00). A significant association was identified between positive pANCA or cANCA result and diagnosis of FRD (P < 0.0001). Agreement between the two assays to detect ANCA in the same serum samples from SCWT with protein-losing enteropathy/protein-losing nephropathy (PLE/PLN) was substantial (kappa, 0.77; 95% CI, 0.53, 1.00). Eight ANCA-positive cases were positive for MPO or PR-3 antibodies.

CONCLUSIONS AND CLINICAL IMPORTANCE

The granulocyte immunofluorescence assay used in our pilot study was easy and quick to perform. Agreement with the previously published method was good.