Novel autoantigens immunogenic in COPD patients - PubMed (original) (raw)

doi: 10.1186/1465-9921-10-20.

Andreas Keller, Sabrina Heisel, Nicole Ludwig, Stefanie Rheinheimer, Veronika Klein, Claudia Andres, Jürg Hamacher, Hanno Huwer, Bernhard Stephan, Ingo Stehle, Hans-Peter Lenhof, Eckart Meese

Affiliations

Novel autoantigens immunogenic in COPD patients

Petra Leidinger et al. Respir Res. 2009.

Abstract

Background: Chronic obstructive pulmonary disease (COPD) is a respiratory inflammatory condition with autoimmune features including IgG autoantibodies. In this study we analyze the complexity of the autoantibody response and reveal the nature of the antigens that are recognized by autoantibodies in COPD patients.

Methods: An array of 1827 gridded immunogenic peptide clones was established and screened with 17 sera of COPD patients and 60 healthy controls. Protein arrays were evaluated both by visual inspection and a recently developed computer aided image analysis technique. By this computer aided image analysis technique we computed the intensity values for each peptide clone and each serum and calculated the area under the receiver operator characteristics curve (AUC) for each clone and the separation COPD sera versus control sera.

Results: By visual evaluation we detected 381 peptide clones that reacted with autoantibodies of COPD patients including 17 clones that reacted with more than 60% of the COPD sera and seven clones that reacted with more than 90% of the COPD sera. The comparison of COPD sera and controls by the automated image analysis system identified 212 peptide clones with informative AUC values. By in silico sequence analysis we found an enrichment of sequence motives previously associated with immunogenicity.

Conclusion: The identification of a rather complex humoral immune response in COPD patients supports the idea of COPD as a disease with strong autoimmune features. The identification of novel immunogenic antigens is a first step towards a better understanding of the autoimmune component of COPD.

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Figures

Figure 1

Figure 1

The separation of intensity values of COPD and control sera is exemplarily shown for an arbitrary antigen A. A: Intensity values of each single COPD (1) and control (0) serum for antigen A are exemplarily shown. The position of the threshold (vertical green bar (2)) determines the number of true positives (TP), true negatives (TN), false positives (FP) and false negatives (FN). The vertical bars 1 and 3 indicate the minimal and maximal thresholds. B: The two curves represent density estimations of intensity values of COPD patients (red curve) and controls (black curve) for antigen A corresponding to Figure 1A. C: The specificity (TN/(TN+FP)) and sensitivity (TP/(TP+FN)) of a test are visualized by the receiver operator characteristics (ROC) curve. The performance of the test can be represented by the area under the ROC curve (AUC). Here, the threshold is represented by the green circle. The values for sensitivity and specificity can be modified by moving the threshold.

Figure 2

Figure 2

Example for a protein macroarray analyzed with serum. Since all clones are spotted in duplicate, any antigen – antibody reactivity is indicated by two signals.

Figure 3

Figure 3

Frequency of antigens according to their AUC value. AUC values of all antigens were calculated for the classification COPD sera versus control sera. The distribution demonstrates a large number of antigens with AUCs < 0.3 and > 0.7.

Figure 4

Figure 4

Intensity values of FAM36A shown for all COPD and control sera. A: FAM36A intensity values shown for each serum. Blue circles indicate sera of COPD patients and red circles indicate control sera. B: Distribution of seroreactivity signals according to their intensities. Seroreactivity signals that stem from controls are indicated in blue, and seroreactivity signals that stem from COPD sera are indicated in green. The overlaps are indicated in yellow. For this clone, signals with low intensities are mostly found with COPD sera and signals with higher intensities are mostly found with control sera.

Figure 5

Figure 5

Intensity values of MCM3 shown for all COPD and control sera. A: MCM3 intensity values shown for each serum. Sera of COPD patients are indicated by blue circles and control sera are indicated by red circles. For this clone, signals with low intensities are mostly found with control sera and signals with higher intensities are mostly found with COPD sera. B: Example of seroreactivity signals. The position of the analyzed clone is indicated by red rectangles. Each clone of the array is spotted in duplicate. By visual analysis, this clone was found positive with all shown COPD sera and negative with all shown normal sera.

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