Charite – Berlin University Medicine

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Researchers from Charité – Universitätsmedizin Berlin and the University of Cologne have gained new insights into post-exposure prophylaxis (PEP) for Bundibugyo Ebola virus. PEP is given proactively to block the potentially severe consequences of an infection. In a first, Charité administered the still-experimental antibody drug MBP134 as PEP. Here, the scientists answer questions about their findings.

Bundibugyo virus is one of the Ebola viruses and can cause particularly severe, often fatal infections in children. There is currently no approved prophylaxis for persons who have had a high‑risk exposure to an infected individual. Five family members of the U.S. Ebola patient we treated in our specialized isolation unit were also transferred to Charité: his wife (a physician) and their four children, ages 1 – 7 years. All five had close, high‑risk contact with the patient; the mother also had direct exposure to a woman later identified as the most likely source of her husband’s infection. In addition to providing close monitoring and optimal care, we wanted to see whether an experimental antibody preparation could lower the risk of Ebola disease in these five contacts and, at the same time, gather safety and tolerability data for this PEP approach.

Each of the five individuals received a single dose of the experimental antibody preparation MBP134. The product combines two broadly neutralizing monoclonal antibodies that have shown efficacy against Bundibugyo virus in laboratory and animal studies. We administered the treatment under a carefully weighed compassionate‑use protocol, given the exceptionally high mortality of Ebola in young children. After dosing, all five family members were monitored closely for 21 days and tested repeatedly for viral RNA. In addition to safety and tolerability assessments, we performed an in‑depth analysis of their immune responses.

None of the five contacts developed any clinical symptoms, and all four children remained completely healthy. The infusions were very well tolerated; no adverse events were observed in this case series. Four days after administration, we detected antibodies in the blood of every participant that neutralized a range of Ebola viruses, including Bundibugyo. This confirmed that the administered antibodies were circulating and functional in the recipients.

In the mother—who had not only been in contact with her infected husband but also with an Ebola patient—we detected, in addition to the administered IgG antibodies, her own IgM and IgA antibodies against Bundibugyo virus. Despite intensive testing, we never detected viral RNA in her samples, and she remained asymptomatic. This pattern suggests a “silent” exposure that primed her immune system without producing a detectable infection.

Post‑exposure prophylaxis with MBP134 was well tolerated by the mother and her four children, with no measurable side effects and no development of disease. While this small case series cannot establish efficacy, it provides crucial safety and immunogenicity data that will inform the systematic evaluation of MBP134 and similar antibody‑based products as PEP for high‑risk exposures in future clinical trials.