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

Abstract

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. Author summary: Oropouche virus (OROV) is a human pathogen transmitted by biting midges. OROV-infected individuals can develop mild febrile illness or, less frequently, severe neurological dysfunction. OROV infection is associated with poor birth outcomes in some infected pregnant women. Diagnosis includes detecting anti-OROV antibodies in patient sera in the early convalescent phase of the disease. Conducting diagnostic tests requires appropriate controls to confirm accurate test performance. Diagnostic test availability is hindered by the need for serum from donors who have recently been exposed to OROV to serve as positive control material. We used standard molecular biology techniques to design a novel, sustainable reagent produced in vitro that can replace limited donor sera while providing equivalent or superior performance in diagnostic tests, improving serology assay standardization across laboratories. Our positive control reagent, OROV119-chIgM, supports the development and standardization of OROV diagnostic testing by providing a renewable source of positive control material. OROV119-chIgM enhances diagnostic capacity globally by ensuring laboratories are poised for rapid response to future OROV outbreaks.

Original publication: PLOS Neglected Tropical Diseases (2026-08-10). Source. Source DOI: 10.1371/journal.pntd.0014642.