Forty years after they were created, handwritten case notes helped an international group of researchers locate survivors of the world’s first recorded outbreak of Ebola virus disease. The team, led by Anne Rimoin, Ph.D., of the University of California, Los Angeles, travelled to remote villages in northwestern Democratic Republic of the Congo (DRC) and found 14 people who had confirmed or suspected Ebola virus infection during the 1976 outbreak. Tests on the survivors’ blood samples showed they had antibodies capable of recognizing and, in four cases, fully neutralizing Ebola virus. A new report on the findings, published in the Journal of Infectious Diseases on December 14, adds important data to knowledge about long-term Ebola survivors and may also provide a glimpse into the future for the more than 10,000 survivors of the 2014-2016 West African Ebola outbreak.
Records from the 1976 outbreak were not retained by Congolese or international health agencies, so Dr. Rimoin and her colleagues used notes and maps sketched by Peter Piot, M.D., and David Heymann, M.D., both of the London School of Tropical Medicine, and Jean Jacques Muyembe-Tamfum, Ph.D., of the Institut National de Recherche Biomedicale in Kinshasa, DRC. The men were among the investigators of the original outbreak, which caused 318 recorded illnesses, 280 of which were fatal. Following those handwritten clues, the scientists tracked down eight men and six women who agreed to participate in the current study. Six of the volunteers had confirmed Ebola virus infection in 1976, while eight were suspected cases. The region of DRC where the volunteers live is without electricity, running water or paved roads. To keep the blood samples cold until they reached labs in Kinshasa, San Francisco, and Frederick, Maryland, for analysis, the team in the DRC established a lab in an earthen-floored hut that was powered by solar panels, deep-cell batteries and generators.
An initial series of tests found that all volunteers had indeed been infected with Ebola virus. Cells from all the survivors made antibodies that reacted with one or more of three Ebola virus proteins, suggesting that the volunteers’ immune systems retained the ability to recognize—and perhaps be protected from—the virus. Further studies were performed under high-level biocontainment conditions at the NIAID Integrated Research Facility at Fort Detrick. There, a team led by Richard Bennett, Ph.D., and Lisa Hensley, Ph.D., tested the ability of the survivor samples to neutralize whole, live Ebola virus. Blood from four survivors could do so. Taken together, the results of the new study show that immune responses in Ebola survivors are both broad (against multiple viral proteins) and very long-lasting. Future studies to characterize the immune responses of these long-term survivors in more detail may inform efforts to develop Ebola therapeutics that can mimic these natural responses to infection and may also guide the development of vaccines that can elicit protective immune responses.
Reference: AW Rimoin, et al. Ebolavirus neutralizing antibodies detectable in survivors of the Yambuku, Zaire, outbreak 40 years after infection. Journal of Infectious Diseases DOI: 10.1093/infdis/jax584 (2017).