Design and optimization of a novel reverse transcription linear-after-the-exponential PCR for the detection of foot-and-mouth disease virus.

AIMS A novel molecular assay for the detection of foot-and-mouth disease virus (FMDV) was developed using linear-after-the-exponential polymerase chain reaction (LATE-PCR). METHODS AND RESULTS Pilot experiments using synthetic DNA targets demonstrated the ability of LATE-PCR to quantify initial target concentration through endpoint detection. A two-step protocol involving reverse transcription (RT) followed by LATE-PCR was then used to confirm the ability of the assay to detect FMDV RNA. Finally, RT and LATE-PCR were combined in a one-step duplex assay for co-amplification of an FMDV RNA segment and an internal control comprised of an Armored RNA. In that form, each of the excess primers in the reaction mixture hybridize to their respective RNA targets during a short pre-incubation, then generate cDNA strands during a 3-min RT step at 60°C, and the resulting cDNA is amplified by LATE-PCR without intervening sample processing. CONCLUSIONS The RT-LATE-PCR assay generates fluorescent signals at endpoint that are proportional to the starting number of RNA targets and can detect a range of sequence variants using a single mismatch-tolerant probe. SIGNIFICANCE AND IMPACT OF THE STUDY In addition to offering improvements over current laboratory-based molecular diagnostic assays for FMDV, this new assay is compatible with a novel portable ('point-of-care') device, the BioSeeq II, designed for the rapid diagnosis of FMD in the field.