Specific detection of reverse transcription-loop-mediated isothermal amplification amplicons for Taura syndrome virus by colorimetric dot-blot hybridization.

The goal of this study was to develop a field diagnosis system based on isothermal reverse transcription-loop-mediated amplification (RT-LAMP) for shrimp Taura syndrome virus (TSV), placing emphasis on specific and simple detection of the LAMP amplicons. After a single-tube RT-LAMP reaction for TSV was established, colorimetric dot-blot hybridization (DBH) was adopted to detect signals only from the target-derived amplicons. The results showed that the modified DBH offered unambiguous and sensitive detection of the TSV RT-LAMP amplicons without the UV cross-linking and denaturation steps. Together, TSV RT-LAMP-DBH assay reached the same dilution point as reverse transcription-nested polymerase chain reaction-agarose gel electrophoresis (RT-nPCR-AGE) for TSV detection. Specificity of the assay was demonstrated by the absence of DBH signal from yeast tRNA and various shrimp viruses. TSV RT-LAMP-DBH was applied to 125 Penaeus vannamei and demonstrated a very good concordance (kappa value, 0.823) with RT-nPCR-AGE assay in detection efficiency. Furthermore, a one-step guanidinium thiocyanate (GuSCN) homogenization method was established to provide RNA extraction efficiency comparable to that of the TRIzol Reagent for RT-LAMP. Requiring simply a heating apparatus, the GuSCN RNA extraction-isothermal RT-LAMP-DBH protocol has the potential for further development for diagnosis of diseases in the field.