Development of VP1 based indirect ELISAs for BK and JC polyomaviruses with seroprevalence assessment and cross reactivity evaluation

BK virus (BKV) and JC virus (JCV) are widespread human polyomaviruses with significant clinical relevance, especially in immunocompromised populations. Reliable serological assays play a key role in epidemiological surveillance and clinical diagnostics. In this study, indirect ELISAs based on recombinant VP1 capsid proteins of BKV and JCV—expressed and purified using insect cell-based systems—were developed and optimized. A serological analysis of 67 human serum samples revealed an overall seroprevalence of 77.6% for BKV and 34.3% for JCV, with antibody prevalence increasing progressively with age. Importantly, competitive inhibition ELISAs demonstrated no significant cross-reactivity between antibodies against BKV and JCV VP1 antigens, confirming the high specificity of the assays. Comparative evaluation indicated that baculovirus-expressed VP1 antigens yielded higher quality proteins yielding stronger and more reliable assay signals, endorsing their use for large-scale seroepidemiological studies. These findings provide robust serological tools for accurate assessment of polyomavirus exposure and have potential clinical utility in monitoring populations at risk of polyomavirus-associated diseases, such as transplant recipients.