A sensitive colorimetric ELISA to measure allergen-specific salivary SIgA for monitoring sublingual immunity efficiency in pollinosis SLIT

Background Sublingual immunotherapy (SLIT) is safe and one of the most effective etiological treatment for pollinosis. Allergen-specific salivary secretory immunoglobulin A (SIgA) is a useful marker to objectively evaluate treatment efficacy. However, saliva samples usually exhibit high background noise because of non-specific binding in enzyme-linked immunosorbent assays (ELISAs). We therefore aimed to establish an amplified ELISA to measure allergen-specific salivary SIgA levels to assess the efficacy of SLIT for Japanese cedar pollinosis. Methods Biotinyl-tyramide (BT-Tyr) was used to amplify the signal in a colorimetric ELISA. The allergen of Japanese cedar pollen, Sugi basic protein (SBP), was biotinylated and used as a reporter to obtain sensitive and specific results with low background. To obtain preliminary observations, we applied this ELISA for measuring 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 with non-amplified conditions. It was also specific for antigens without background noise. The levels of SBP-specific SIgA in saliva increased in patients 9 months after SLIT initiation at the latest. Conclusions We developed a sensitive colorimetric ELISA to measure SBP-specific SIgA in saliva using BT-Tyr-based amplification and biotinylated antigen as a reporter. We successfully applied 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.