Development and evaluation of a whole virus-based enzyme-linked immunosorbent assay for the detection of human metapneumovirus antibodies in human sera

To apply serological testing for human metapneumovirus (hMPV) to large-scale sera samples, an enzyme-linked immunosorbent assay (ELISA) was developed in which purified virions were used as the antigen. The ELISA was evaluated using 102 human sera specimens from patients aged 0-59 years. There was a positive association between the ELISA results and neutralization test titers, with the correlation coefficients being greater in children <6 years old (ρ = 0.899, P < 0.0001), which is consistent with a primary infection, than in persons ≥6 years old (ρ = 0.523, P < 0.0001). Fifty sera samples were subjected to radioimmunoprecipitation to measure the quantity of antibodies to the fusion protein (RIP-F) and the nucleoprotein (RIP-N). The results showed significant associations between the ELISA titers and the amount of RIP-F as determined by radioimmunoprecipitation in children <6 years old (ρ = 0.804, P = 0.0083) and in persons ≥6 years old (ρ = 0.577, P = 0.0009). The correlation between the ELISA titer and the amount of RIP-N determined by radioimmunoprecipitation was not significant in persons ≥6 years old (ρ = 0.417, P = 0.0829), although this correlation was significant in children <6 years old (ρ = 0.764, P = 0.0137). The ELISA titer correlated with the amount of antibodies to the F protein, but not to the N protein. This whole virus-based ELISA will be useful for the diagnosis of hMPV infection in clinical laboratories and is also useful for the large-scale investigations, such as seroprevalence among residents of a particular region.