Sensitive colorimetric ELISA measuring salivary SBP-specific secretory IgA, its application to pollinosis SLIT

Background Sublingual immunotherapy is safe and one of the most effective etiological treatments for pollinosis. Salivary allergen-specific secretory immunoglobulin A (SIgA) is a useful marker to objectively evaluate treatment effectiveness. However, saliva samples usually exhibit high background noise because of nonspecific binding in enzyme-linked immunosorbent assays (ELISAs). Objective We aimed to establish an amplified ELISA to measure allergen-specific salivary SIgA levels to assess the efficacy of sublingual immunotherapy (SLIT). Methods Biotinyl tyramide (BT-Tyr) was used to amplify the signal in a colorimetric ELISA. The allergen sugi basic protein (SBP) was biotinylated and used as a reporter to obtain sensitive and specific results with low background. This ELISA was used to measure anti-SBP SIgA levels in saliva samples from SLIT-treated patients with Japanese cedar pollinosis. Results The ELISA was highly sensitive and achieved more than 200-fold signal amplification compared to non-amplified conditions. It was also specific for antigens without background noise. The levels of SBP-specific SIgA in saliva increased in patients 3 months after SLIT initiation. Conclusion We established a sensitive colorimetric ELISA to measure SBP-specific SIgA in saliva using BT-Tyr-based amplification and biotinylated antigen as a reporter. We used this sensitive ELISA to monitor the levels of SBP-specific SIgA in saliva samples from patients with pollinosis receiving SLIT. Increased salivary SBP-specific SigA levels were observed in these patients.