Serological diagnosis of human polyomavirus infection

Measurement of antibody titres to the human polyomaviruses BK and JC has for many years had to rely on Hemagglutination inhibition. In recent years, viral serology based on virus-like particles (VLPs) in enzyme immunoassays (EIAs) has become widely used for a variety of viruses. We sought to establish a modern method for serological diagnosis of BK and JC viruses, by using purified VLPs containing the VP1 major capsid proteins. Antibody titres in assays based on VLPs of BKV (strain SB) showed no correlation to the titres in similar JCV assays. BKV (SB) seropositivity increases rapidly with increasing age of the children and reaches a 98 % seroprevalence at 7-9 years of age, whereas JCV seroprevalences increase more slowly with increasing age reaching 51 % positivity among children 9-11 years of age. The antibody levels are almost identical in serial samples taken up to 5 years apart, suggesting that both BKV and JCV VLP seropositivitities are usually stable over time and can be used to measure cumulative exposure to these viruses. Serology using SV40 VLPs showed strong cross-reactivity with human polyomaviruses, in particular with BKV strain AS, and establishing a specific VLP-based serology assay for SV40 required blocking with several hyperimmune sera to the human polyomaviruses. SV40-specific seropositivity also increased with increasing age of children, reaching 14% seroprevalence among children 7-9 years of age, but had limited stability over time in serial samples.