An engineered anti-Oropouche virus human-murine chimeric immunoglobulin M is a viable substitute for positive human serum controls in diagnostic serology assays.

Oropouche virus (OROV) is an arbovirus of concern due to its recent geographical expansion and association with teratogenic outcomes. Serodiagnosis of OROV infection relies on methods such as the immunoglobulin M antibody-capture enzyme-linked immunosorbent assay (MAC-ELISA) and the plaque reduction neutralization test (PRNT). For re-emerging viruses such as OROV, sourcing large quantities of sera from acutely infected human donors for use as positive-control assay material is a significant challenge and hinders diagnostic capacity. To overcome this, we engineered and produced OROV119-chIgM, a human-murine chimeric IgM (chIgM) that expresses the variable regions of the murine monoclonal antibody OROV119, reactive to the Gc protein of OROV, on a human IgM backbone. OROV119-chIgM was evaluated in PRNT and MAC-ELISA to determine its suitability as a positive control in each assay. In PRNT, OROV119-chIgM achieved neutralization equivalent to an OROV polyclonal mouse hyperimmune ascitic fluid (MHIAF). Further, OROV119-chIgM exhibited superior performance compared with OROV-positive human donor sera in a MAC-ELISA. Overall, OROV119-chIgM is an attractive alternative to human donor sera assay control material because of its long-term sustainability and consistent batch-to-batch potency. OROV119-chIgM enhances diagnostic capacity by ensuring laboratories are poised to respond rapidly to future OROV outbreaks.