Rapid and specific detection of H3 swine influenza virus using reverse transcription loop-mediated isothermal amplification method

Aim: The main objective of our study is to develop a reverse transcriptase loop-mediated isothermal amplification (RT-LAMP)-based system for rapid and specific detection of H3 swine influenza virus (SIV). Methods and Results: The system, H3 RT-LAMP, contained a set of six novel primers that targeted eight distinct regions of the viral haemagglutinin (HA) gene that are highly conserved among H3 influenza A viruses but not between H3 and other subtypes. H3 RT-LAMP accurately and specifically detected H3 SIV of different isolates from culture and from swine lung samples. The system is at least 10-fold more sensitive than the conventional RT-PCR assay and even comparable to the real-time RT-PCR method, with the detection limit of about one plaque-forming unit per reaction. Of 27 swine lung samples tested, 11 samples were positive in reactions with the RT-LAMP and real-time RT-PCR methods, while only 7 were positive with the conventional RT-PCR assay. Importantly, the assay can be completed within 45 min and is faster than the conventional RT-PCR and real-time RT-PCR approaches. Conclusions: Our results provide the first direct evidence that RT-LAMP is highly specific and sensitive for detecting H3 SIV. Significance and Impact of the Study: These results suggest that LAMP offers a promising alternative tool for rapid, inexpensive and specific diagnosis of influenza virus infection of swine and other animals in frontline settings.