BACKGROUND: The role of certain gut microbes in the development of colorectal cancer has recently been understood. In our previous work, we have reported the reactivity of serum collected from CRC patients to peptide mimotopes of bacterial antigens associated with the development of CRC, hence, their potential in its detection. Here, we evaluate the diagnostic parameters of an anti- Clostridioides difficile toxin B (tcdB) peptide mimotope IgG and IgA antibody-capture enzyme-linked immunosorbent assay (ELISA) in the detection of CRC.
METHODS: Prediction of the immunogenic epitopes of tcdB was made using the in silico B-cell epitope mapping tools available at the Immune Epitope Database and Analysis Resources (IEDB). Synthetic peptide analogs of the predicted epitopes which were used in the immunoassays were synthesized and purchased from Genscript (New Jersey, USA). Presence of anti-peptide IgG and IgA from serum collected from patients diagnosed with colorectal cancer were detected by a peptide antibody-capture indirect ELISA protocol developed in this study. Diagnostic parameters were computed.
RESULTS: The amino acid position 1465 to 1474 of the reported sequence of tcdB (PDB Accession No. AGG91641.1) was predicted to be immunogenic. The peptide antibody-capture ELISA developed in this study gave diagnostic specificities of 94.9% and 97.4%, positive predictive values (PPV) of 86.6% and 93.3%, and likelihood ratios of 6.5 and 14.0 for IgG and IgA, respectively. Our results show the potential of the immunoassay designed in ruling in possibility of CRC during diagnosis.