Development of a Recombinant Protein-Based Immunoassay for Detection of Antibodies Against Karolinska Institute and Washington University Polyomaviruses.

To develop polyomavirus VP1 recombinant protein-based immunoassay, the expression of two polyomavirus (Karolinska Institute Polyomavirus; KIPyV, and Washington University Polyomavirus; WUPyV) VP1s in insect cells was investigated using an improved baculovirus system (BacMagic). The reliability of the purified VP1 to serve as antigens in serological tests was confirmed by the establishment of an enzyme-linked immunosorbent assay (ELISA). Two panels of serum samples were used, with Panel I comprising 60 sera (20 KIPyV-positive, 20 WUPyV-positive, and 20 negative) and Panel II consisting of 134 sera with unknown status. The seroprevalence of KIPyV and WUPyV in the study population was determined to be 62% and 50%, respectively. Antibody-negative sera exhibited low reactivities in both ELISAs, whereas antibody-positive sera displayed high reactivity with median optical density values of 1.37 and 1.47 in the KIPyV and WUPyV ELISAs, respectively. The differences in seroreactivities between antibody positive and negative for each virus were statistically significant (p < 0.0001; with 95% confidence interval). The study suggests that seroconversion for KIPyV and WUPyV occurs in childhood, with KIPyV seropositivity reaching 70% and WUPyV seropositivity reaching 60% after the age of 5 years. Adult seroprevalence for polyomaviruses was high, with more than 64% and 51% of the adult population being seropositive for KIPyV and WUPyV, respectively. The constant prevalence of KIPyV and WUPyV antibody in the age groups suggested that this antibody persists for life. The fact that antibody titers were generally stable over time revealed a persistent infection of polyomaviruses in the human population. The insect cell-derived recombinant VP1-based ELISA has been demonstrated to be valuable as a serological assay, offering a valid, reliable, fast, nonlaborious, and economical procedure.