Sandwich enzyme-linked aptamer-based assay for the detection of Trichomonas vaginalis

Trichomoniasis is the most prevalent curable, non-viral sexually transmitted infection (STI), with an estimated 156 million new infections in 2020. It can potentially result in adverse birth outcomes as well as infertility in men, whilst it also increases the risk of acquiring HIV and contracting other vaginal infections. It is mostly prevalent among women in low-income countries and especially in Africa and the Americas. This STI is caused by Trichomonas vaginalis (TV) and a robust, cost-effective, sensitive, specific and rapid diagnostic test is urgently required. We report the screening of 6 full-length and 4 truncated aptamers previously selected in our group for use in a microplate-based sandwich assay. The combination of dual aptamers comprising a short 14-mer truncated capture aptamer (termed A1_14mer) and a full-length non-truncated reporter aptamer (A6) was elucidated to be the optimum pair for a sensitive sandwich enzyme-linked aptamer assay (ELAA) for the detection of TV achieving a detection limit of 3.02 × 10⁴ TV cells/mL. The results obtained with the A1_14mer-A6 ELAA correlate excellently with wet-mount microscopy for the detection of TV in clinical specimens, cervicovaginal lavages and vaginal swabs, highlighting the potential clinical application of this assay for cost-effective population screening and subsequent prevention of the onset of complications associated with undiagnosed and untreated TV.