Classification between Viable and Non-Viable Influenza A Virus and Differentiation of H1N1 and H3N2 Subtypes with a Propidium Monoazide xx (PMAxx) Based Loop-Mediated Isothermal Amplification (LAMP) Assay

Influenza A virus outbreaks pose a significant burden to global health. However, detecting and subtyping the virus is challenging due to its high mutation rate, and it is difficult to distinguish viable viruses that cause infection from clinical samples. Here is a novel PMAxx-LAMP assay for the classification of viable and non-viable Influenza A virus together with differentiation between H1N1 and H3N2 subtypes. Our loop-mediated isothermal amplification (LAMP) primers displayed limits of detection of 102 copies/mu L for both subtypes, high specificity, reproducibility, and good linearity with correlation coefficients of 0.9762 and 0.9901 for H1N1 and H3N2, respectively. PMAxx effectively distinguished between viable and non-viable viruses at an optimal concentration of 10 mu M. In the LAMP method, the clinical specificity and sensitivity for the H1N1 subtype were both 100%, while for the H3N2 subtype, they were 94.44 and 92.31%, respectively. With the PMAxx-LAMP assay, the clinical specificity and sensitivity were 68% and 65% for the H1N1 subtype, and 81% and 69% for the H3N2 subtype, respectively. The reduced clinical specificity and sensitivity observed in the PMAxx-LAMP assay can be attributed to the presence of non-viable viruses, which are labeled with PMAxx and subsequently eliminated from positive samples. The PMAxx-LAMP offers potential benefits in determining the stage of infection, enabling early screening of patients, and shortening the window period for virus detection. The simplicity and efficiency of this assay make it suitable for use in resource limited settings and point-of-care (POCT) applications.