Development of a LAMP assay for the rapid visual detection of the emerging tick-borne Songling virus.

BACKGROUND

Songling virus (SGLV) within the genus Orthonairovirus, family Nairoviridae, is an emerging tick-borne virus associated with human febrile illness. However, no rapid detection method for SGLV has been established.

METHODS

In this study, four primer sets targeting the nucleocapsid protein gene of SGLV were designed for use in the LAMP assay and evaluated to identify the optimal primer set. Recombinant plasmids were constructed and utilized for assessing the sensitivity of the assay. Tacheng tick virus 1 (TcTV-1)-, Beiji nairovirus (BJNV)-, Yezo virus (YEZV)-, severe fever with thrombocytopenia syndrome virus (SFTSV)-, and tick-borne encephalitis virus (TBEV)-positive tick samples were utilized to assess the specificity. Field-collected ticks were also evaluated as biological specimens to validate the assay.

RESULTS

A SGLV-specific LAMP assay was established with a detection limit of 1 × 10-2 copies/μl and could be visually confirmed by a color change from purple to blue in SGLV-positive samples. No cross-reactivity was observed in the detection of TcTV-1, BJNV, YEZV, SFTSV, and TBEV using the LAMP assay. In addition to the detection of the same seven high-copy numbers of SGLV as the SYBR Green quantitative RT-PCR assay within a reduced timeframe, the developed LAMP method also effectively identified an additional sample with a low copy number in the field-collected tick samples.

CONCLUSIONS

We successfully developed a sensitive, specific, and cost-effective visual method for the rapid detection of SGLV using the LAMP assay, which can be applied in pathogenesis and epidemiological surveillance studies of SGLV.