First look at immune cells of Ebola survivors

Ebola Virus

Source: Wikimedia Commons

In a first-of-its-kind-study on patients who survived the Ebola infection, researchers from Emory and the Centers for Disease Control and Prevention have obtained a close look at the immune responses in four Ebola virus survivors who received care at Emory University Hospital in 2014, by closely examining their immune response. The four patients voluntarily donated blood on multiple occasions as part of this research study, says Aneesh Mehta who is an immunologist at Emory Vaccine Center.

The death toll due to Ebola is 9961, as on March 8th, 2015.  Still, scientists have very limited information about how the body’s immune system responds to this virus infection. Previous research on Ebola virus disease had suggested that the immune system could be impaired during infection, however, “Our findings counter the idea that Ebola virus infection is immunosuppressive, at least in the patients that we were able to study,” says lead author Anita McElroy, MD, Assistant professor of pediatrics (infectious disease) at Emory University School of Medicine.

Study of the immune systems of these four patients showed that the body musters a robust immune response against the virus, with strong signs of T cells and B cells activation during the acute phase of the disease. They monitored the patients’ B cells, which are responsible for generating antibodies against Ebola virus, and T cells (specifically, CD8+ T cells) which directly kills infected cells.

The CD8+ T cells  seemed to target several proteins, specifically the internal Ebola virus nucleoprotein, NP. However, the current vaccines which are entering clinical trials in Africa (in Guinea and Liberia) are designed to trigger immune response against a different protein, called GP – the glycoprotein which coats the surface of the virus. “Since human T cells are really interested in this nucleoprotein, maybe we should try incorporating it into the vaccine to see if that could give even better immune responses,” says virologist and paediatrician Anita McElroy of Emory University.

Their study further supports the general consensus that: if patients receive early care, it can give their bodies enough time to fight off the infection.

“It’s like we’re racing against the virus,” says Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases in Bethesda, Maryland. “The idea that Ebola causes 90% mortality is under the worst conditions. If you take that same patient and put her in intensive care until her immune system kicks in, you can dramatically diminish the mortality to maybe 20% or less,” he says.

Two of the patients showed heightened immune response to Ebola virus for as long as a month, after they were cured and released from the hospital. This shows, that even after the infection is cleared out from the body, the viral fragments remained and kept the immune system on ‘high alert’. This could explain the typical ‘post-Ebola syndrome’ experienced by survivors who show symptoms such as body aches and pains, vision problems, fatigue and skin problems when they were convalescing. However, McElroy states that the study involves too few survivors to pinpoint what underlies the post-Ebola syndrome.

The current study could have a lot of implications in the effort to develop vaccines against Ebola.

The original publication can be accessed here.

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