Development of a rapid chromatographic immunoassay for detection of human metapneumovirus using monoclonal antibodies against nucleoprotein of hMPV.

Human metapneumovirus (hMPV) nucleocapsid (N) protein is a major structural protein that encapsidates the RNA genome and is essential for replication and transcription of the hMPV genome. We developed two mouse monoclonal antibodies (MAbs), designated 3D1 and 5B10, against N protein of hMPV and characterized them by an immunofluorescence assay and an immunoprecipitation assay using Trichoplusia ni (Tn5) insect cells infected with a recombinant baculovirus-expressing hMPV N protein. Both MAbs were found to be reactive to two groups of hMPV by an immunofluorescence assay using two groups of hMPV-infected cells. A chromatographic immunoassay (lateral flow assay) was developed using the MAbs. The assay is a sandwich immunoassay that uses a paper membrane with a gold colloid-conjugated MAb (5B10) in a liquid phase and an MAb (3D1) in a solid phase. We preliminarily examined the sensitivity and specificity using hMPV-infected cells, Tn5 insect cells infected with a recombinant baculovirus-expressing hMPV N protein, hMPV, and purified N protein. The assay had good specificity and sufficient sensitivity to detect hMPV. Therefore, the assay may be a rapid and useful test for diagnosis of hMPV infections.