Development of a Protein-Free Nucleic Acid Lateral Flow Assay for Trichomonas vaginalis

In line with the global research priorities on sexually transmitted infections (STIs), we developed a molecular point-of-care test (POCT) for the parasite Trichomonas vaginalis that causes the STI trichomoniasis. Trichomoniasis remains the most common curable nonviral STI. We report on the use of specific T. vaginalis single-stranded-tailed DNA primers in combination with recombinase polymerase amplification (RPA) in a protein-free nucleic acid lateral flow (NALF) device for use at the point of care. The use of aminated DNA probes eliminates the need for proteins (such as streptavidin or hapten-specific antibodies) for detection of the DNA amplicons, simplifying the manufacturing process and improving reproducibility and cost-effectiveness. The estimated shelf life of the NALF devices is at least 6.6 months at 22 °C, and the devices exhibited high reproducibility. The RPA-NALF requires three simple operator steps with minimal instrumentation and takes approximately 30 min from sample preparation to interpretation of the result. It is specific to T. vaginalis and can detect 1.3 × 10³ cells/mL with visual readout or 282 cells/mL with the aid of a portable LFA reader. Analysis of the two sets of clinical genomic DNA extracts showed that RPA-NALF is positive for all samples positive by culture assay and for samples with Cq ≤ 23 with the S-DiaMGTV qPCR. Finally, RPA-NALF is positive on biobanked vaginal swabs with T. vaginalis Cq ≤ 25 with the Allplex qPCR assays. These results demonstrate that RPA-NALF can specifically detect a moderate load of T. vaginalis even in the presence of other microbial DNA and cells and other components of clinical samples.