When faced with an infection, the immune system can produce pathogen-specific antibodies and immune cells called T cells. Both immune responses can help prevent infection in the event of a future exposure to the pathogen. New research from NIAID-funded scientists reveals that most individuals in a sample of West African Ebola survivors produced a unique subset of T cells called CD8+ T cells—also known as killer T cells. These cells recognize viral proteins that appear on the surface of infected cells, which they subsequently destroy. The novel analysis brings new insight into the natural course of infection in those that survive the often-fatal hemorrhagic disease, according to a report published on July 23 in PNAS.
EBOV is a major global health concern; however, scientists face many difficulties in conducting basic scientific research to learn more about how the human immune system reacts to infection. For example, until the most recent outbreaks, Ebola outbreaks involved too few individuals living in remote, inaccessible areas to collect diverse tissue samples from survivors.
In this study, researchers from Scripps Research, the Broad Institute of MIT and Harvard University and their collaborators partnered with the Sierra Leone Association of Ebola Survivors to analyze blood samples from 30 volunteers with confirmed diagnoses of Ebola virus disease. All volunteers were from Sierra Leone and survived the 2013-2016 Ebola outbreak, which led to more than 28,000 documented infections and 12,000 deaths in West Africa.
Researchers found that among these 30 survivors, 26 had strong CD8+ T cell responses to at least one EBOV protein—indicating that so-called cell-mediated immunity, in addition to the production of EBOV-specific antibodies, may play a key role in surviving Ebola virus disease. Twenty-five of the survivors had strong CD8+ T cell responses to nucleoprotein (NP), a viral protein located inside the virus, while only 10 survivors produced CD8+ T cells that responded to a protein on the surface of EBOV called glycoprotein (GP). This observation surprised researchers because, in the case of most microbes, the immune system is more likely to react to viral surface proteins like GP.
The findings help illuminate how some people exposed to Ebola virus disease survive the infection and may offer insights into protection against future exposure to EBOV. Learn more about NIAID’s research on Ebola virus.
S Sakabe et al. Analysis of CD8+ T Cell Response During the 2013-2016 Ebola Epidemic in West Africa. PNAS DOI: 10.1073/pnas.1806200115 (2018).