Loop-mediated isothermal amplification for human influenza A viruses

Influenza diagnostic testing is a pivotal public health tool because this viral infection causes enormous morbidity, mortality and financial burden. Laboratory diagnosis of influenza infection also plays an important role in the individual patient management and outbreak control that all resulting in significant financial benefits (1). There are a number of molecular tests developed for rapid detection and typing of influenza virus. Reverse transcriptase PCR using specific primers recommended by WHO has been set up and used in diagnostic laboratories worldwide for rapid detection and typing of influenza viruses (2). In the last decades several modern molecular techniques have been innovated that provides the new alternatives for molecular diagnosis of infectious disease (3). In 2000 Notomi et al. reported a novel nucleic acid amplification method, loop-mediated isothermal amplification (LAMP) working based on selfrecurring strand-displacement DNA synthesis primed by a specially designed set of targetspecific primers (4). Soon after LAMP assay as a more rapid, accurate and cost-effective method has been taken into consideration in Influenza molecular detection. Several studies have been reported the successfully application of LAMP/RT-LAMP method for detection of different subtypes of influenza viruses such as H1N1, H3N2, H5N1, H9N2 (5, 6, 7). Here, we carried out LAMP approach for detection of the human influenza A viruses (H1 and H3) using primers introduced by Poon et al in 2005, as mentioned in table 1 (8). This set of primers is specific for M fragment but by designing degenerated nucleotides in their sequences, it just detects human H1, H2 and H3 isolates. Two standard seasonal influenza virus strains, H1N1 (New Caledonia 20/1999) and H3N2 (A/H3N2/Panama/2007/99) were obtained from Pasteur Institute, Influenza Research Lab. 150 microliter of infected culture supernatant of each virus sample, equivalent to 4×10 3