Little has been uncovered about how the Ebola virus works inside the human body since it was discovered in Africa four decades ago, but the 2014 outbreak gave researchers a chance to learn more about how the often-fatal disease attacks the body and how the body fights back.
In a first-of-its-kind study published Wednesday by the Centers for Disease Control and Prevention, researchers shared the results of daily tests done on the seven Americans who were treated in the U.S.
Rick Sacra and Ashoka Mukpo were successfully treated that fall at the Biocontainment Patient Care Unit at Nebraska Medicine, the clinical partner of the University of Nebraska Medical Center in Omaha.
Martin Salia died shortly after arriving at the unit in November 2014.
Blood draws taken from the three, as well as from four people treated in other U.S. hospitals, have provided a foundation for understanding Ebola’s progression, said Chris Kratochvil, associate vice chancellor for clinical research at UNMC.
Although more than 30,000 people have been infected since Ebola was identified in 1976, few blood samples had been taken and fewer still studied as extensively.
“The vast majority of those 30,000 cases weren’t able to have routine lab samples collected, and for those who did, the samples were not able to be preserved and tested extensively,” Kratochvil said. “We could test the blood and then save more for more elaborate testing down the road.”
Researchers studied 54 biomarkers present in human blood during the course of an acute Ebola infection and during recuperation and compared them with biomarkers found in a healthy person.
They learned that the virus triggers an inflammatory response similar to that in people with autoimmune disorders like rheumatoid arthritis. And it creates dysfunction in blood vessels and with clotting, the markers showed.
But the results of the study, which included UNMC faculty members Peter Iwen and Phillip Smith, also contained a surprising factor.
“The body is forced to mount such a robust immune defense to fight the virus,” Kratochvil said. “One of the concerns is that it’s overcompensating.”
Controlling the body’s response to Ebola could be a difficult tightrope to walk: Intervene too early and risk inhibiting the body’s natural ability to fight off the virus, but respond too late and a supercharged immune system could begin attacking healthy tissues, resulting in organ failure, or more commonly, death.
“Not only will using the correct therapies be important, but also the timing of administration will be critical,” the report says. “Immune inhibition, if initiated at an inappropriate time, could be detrimental to the host.”
Put more simply, Kratochvil said: “The challenge is not to intervene and stop the aspects of the body fighting off the virus that are beneficial.”
There are limitations to the research. Aside from the small sample size, it remains unclear from data collected by the CDC, UNMC and Emory University how any of the experimental treatments tried in Omaha and elsewhere affected the immune system biomarkers.
The report, which was published in the Clinical Infectious Disease Journal this week, illuminates the benefits and drawbacks of the immune system’s response to Ebola, but researchers say more study must be done before effective treatments can be deployed.
“We were able to identify the particular components of patients’ immune systems that successfully fought off the virus,” said the CDC's Anita McElroy. “These are parts of the immune system we need to tap into to develop new therapies.”
Kratochvil said the study also demonstrates the importance of research that allows clinicians to prepare for the next outbreak of Ebola and similar diseases.
“We’ve known about Ebola since it was discovered, but the extent of the research conducted into understanding it has been limited,” he said. “There has been some momentum with research into Ebola, but we must continue to move forward to better prepare vaccines and better treat and manage patients.”