Utility of serum ERAP1 and ERAP2 as novel biomarkers in the management of recalcitrant warts: A cross-sectional study

Introduction

Warts are benign epidermal cell proliferations generated by human papillomaviruses (HPVs), which are DNA viruses with a particular affinity for keratinocytes.¹ About 5% of human malignancies are caused by persistent infections with oncogenic HPVs.²

Although most warts disappear on their own in months or years, there are instances of resistant warts continuing to grow despite numerous treatment attempts. Although the precise process is unknown, cellular immunity is essential for the clearance of HPV infections. Individuals with large, enduring, or treatment-resistant warts may have immune system deficiencies that contribute to their vulnerability to HPV.³

One-third of non-genital warts are resistant to immunotherapy and the majority of conventional therapies. It seems that the prevalence of resistance is rising due to the increasing immunosuppressant use.⁴

Antigens on MHC are monitored by the immune system in order to distinguish the infections. Endoplasmic reticulum amino-peptidases (ERAP1 and ERAP2) trim antigenic peptides broken down in proteasomes to the proper lengths for presentation on MHC-I molecules and subsequent activation of T-cells or NK-cells. Accordingly, ERAP1 and ERAP2 may be targets for viral infections and autoimmune disorders.⁵

This study aimed to assess serum concentrations of ERAP1 and ERAP2 in patients with recalcitrant warts.

Methods

Data collection and Laboratory investigations

Each participant gave a full medical history, focusing on the duration of warts, previous treatments, and a number of recurrences. Cutaneous examination was done to determine the type, site, number, and sizes of warts. Commercial human ELISA kits were used to measure serum levels of ERAP1 (Catalogue number: SRB-T-83718, Sensitivity:0.045ng//mL, Range: 0.05-15ng/mL) and ERAP2 (Catalogue number: 201-12-8104, Sensitivity:10.25ng//L, Range: 15-3500ng/L), Shanghai SunRed Biological Technology Co., Ltd., China.

Results

The mean age of group (I) was 25.52 ± 10.65 years and group (II) was 27.91 ± 7.77 years, with no significant difference (p = 0.07). Both groups were sex matched (p = 0.4). The ERAP1 level was significantly lower in group (I) (2.21 ± 1.22 ng/mL) than in group (II) (11.1 ± 4.1 ng/mL) (p < 0.001). The ERAP2 level in group (I) (1.21 ± 0.7ng/mL) was significantly lower than in group (II) (6.2 ± 2.5ng/mL) (p < 0.001) [Table 1, Figure 1].

Close

Figure 1:

Serum levels of ERAP1 and ERAP2 in the study groups.

Export to PPT

ERAP1 and ERAP2 levels did not differ significantly for gender (p = 0.1, 0.3, respectively) and family history of recurrent warts (p = 0.5, 0.6, respectively) [Table 2].

There was a significant difference in ERAP1 levels (p = 0.04) according to the site of warts but not in ERAP2 (p = 0.4 ) [Table 3].

Significant positive correlation was detected between ERAP1 and ERAP2 (r = 0.8, p < 0.001). ERAP1 and 2 were negatively correlated with the number of warts and the number of recurrences with statistical significance (p <0.001 for both). However, ERAP1 and 2 had no significant correlation with other variables, including the age of the patient, duration of the disease, and size of warts (p > 0.05 for all) [Table 4, Figure 2].

Close

Figure 2:

Correlation between serum ERAP1 and ERAP2.

Export to PPT

Optimal cutoff points of serum ERAP1 and ERAP2 levels significantly distinguish between patients with recalcitrant warts and those with non-recurrent warts where the area under the curve (AUC) equals 0.88 and 0.84, respectively, and a significant p-value <0.001 [Table 5, Figure 3].

Close

Figure 3:

ROC curves for serum ERAP1 and ERAP2 in the prediction of recalcitrant warts

Export to PPT

Discussion

ERAPs can be released into the extracellular environment and undertake a number of pathogenic activities in addition to their role as antigen-processing enzymes.^7-9 To our knowledge, this is the first study to assess serum levels of ERAP1 and ERAP2 in patients with recalcitrant warts. The present study found that patients with resistant warts had considerably lower ERAP1 and ERAP2 levels than those with no recurrence. Moreover, ERAP1 and ERAP2 showed an evident negative correlation with the number of warts and recurrence rate.

ERAP1, a zinc metallopeptidase, trims peptides and cleaves proinflammatory cytokine receptors like TNF-α, IL-6, IL-1 α, and IL-1 β to modulate signal intensity on the cell surface.¹⁰ These cytokines, produced by CD4+ and CD8+ T-cells, are linked to wart regression.¹¹ Disruption or absence of ERAP function can change the antigens presented by MHC I molecules, influencing the activation of NK cells and CD8+ T cells. This can result in a weakened immune response and illness development.¹²

Previous studies have described the dysregulation of ERAP1 in many conditions, such as HIV, lymphocytic choriomeningitis virus (LCMV), human cytomegalovirus (HCMV), hepatitis B virus (HBV), and hepatitis C virus (HCV) infection.^13-17

The results of this research showed a strong positive association between ERAP1 and ERAP2. The previously published studies demonstrated that ERAP1 and ERAP2 work together to produce complete epitopes that bind to MHC I. It was discovered that ERAP2 physically associates with ERAP1 and exhibits unique specificity for the N-terminal of the peptides. It is anticipated that this complex handles the many precursor peptides more effectively than individual enzymes.¹⁸

In line with the positive correlation between ERAP1 and ERAP2, Kemming et al. found that variation in one ERAP-coding gene influences the function of the other, modifying the immune reaction to HCV.¹⁹

However, ERAP’s role may be context dependent. In mice with HLA-B27, the deletion of ERAP resulted in a substantial reduction in CD8+ T response to influenza epitopes. In contrast, ERAP was not required for peptide processing in the presence of HLA-B7.²⁰

Limitations

Limitations of this study include the small sample size, the lack of measurements of ERAP1 and ERAP2 before and after treatment, and the exclusion of medical conditions such as diabetes mellitus and hypertension. Further prospective studies with analysis of ERAP1 and ERAP2 coding gene polymorphisms are necessary to validate the current findings and elucidate the underlying mechanisms. Correlations between tissue expression and serum levels of ERAP1 and ERAP2 will help clarify their role in the pathogenesis of warts. The correlation of ERAPs with HPV viral load and different HPV serotypes needs to be assessed in future studies.

Conclusion

ERAP1 and ERAP2 play critical roles in the immunity against HPV infections. Dysregulation of these amino-peptidases may contribute to the persistence and aggression of warts. Incorporating such markers into clinical practice may aid in early detection, risk stratification, and individualised treatment options for patients with resistant warts.