EVALUATION OF INTERACTIONS OF SARS-COV-2 STRUCTURAL PROTEINS WITH SPECIFIC ANTIBODIES BY SPR ASSAY

Background: The World Health Organization admitted that the vaccination against Covid 19 limited the deaths, but not the spread of the disease. This requires a method allowing a specific, rapid and accurate diagnosis of the disease. We report a SPR assay that meets the requirements and can be applied no only for SARS Cov-2 diagnosis but as a tool for early diagnosis of otherinfections. Methods: Surface plasmon resonance (SPR) method was used to identify the binding of S/N protein to monoclonal antibodies. N-protein monoclonal antibody (NP mAb), S-protein monoclonal antibody (SP mAb), and receptor bind domain (RBD) antibody were used as recognition molecules. Ligands were deposited by the matrix-assisted laser evaporation (MAPLE) method, which guarantees maximum interaction specificity. Results: We registered S/N protein binding to the corresponding mAbs and S protein to RBD antibody with high sensitivity: the interactions were observed at protein concentration about 130 femtomoles (fM). A very good specificity was observed: the measured S protein binding activity to NP mAb was below the limit of detection (LOD). The same was noticed for N protein binding to SP mAb. Conclusions: The presented SPR assay possesses high sensitivity and selectivity and provides quantitative analysis. This makes it applicable for following the evolution of acute SARS-CoV-2 infection, especially at the early stages of viral replication which can be clinically useful

Detection of Helicobacter pylori in saliva based on surface plasmon resonance by binding of Lewis b (Leb) blood group antigen to specific adhesin BabA

Helicobacter pylori affects about half of the population around the world. Therefore, timely and reliable diagnosis of the disease is required. Non-invasive detection of H. pylori is the technique of choice for infection control. Sample collection from saliva is non-invasive, but the bacteria load in human saliva is lower than in samples collected from the stomach, blood or stool. Hence, a detection method of high specificity and sensitivity is required. The purpose of this study was to evaluate the applicability of the Surface Plasmon Resonance (SPR) biosensor, based on the binding of Lewis b (Leb) blood group antigen to the specific adhesin BabA, for H.pylori detection in saliva. Our studies on saliva artificially contaminated with H. pylori, demonstrated that the BabA - Leb binding reaction had high specificity. The results obtained indicated that there are two mechanisms that inhibit the viability of H. pylori. The first involves the direct interaction between H. pylori and the oral antagonistic bacteria, and the second involves the bactericidal effect of certain proteins produced by the oral background bacterial flora. Although the sensitivity of detection of the proposed method needs to be increased, the results obtained proved its applicability and feasibility for H. pylori detection in saliva and the good prospects it offers for both clinical application and as a rapid point-of-care test