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.