Ebola’s ability to evade the immune system identified

January 28, 11:09 AMScience News ExaminerMeg Marquardt

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Scanning electron microscope image of Ebola virions. (Credit)
 

Researchers at University of Pennsylvania School of Medicine [UPSM] have made an important discovery: just how the Ebola virus manages to evade the immune system.  Since its discovery in 1976, Ebola has been a deadly efficient enigma in the world of health care, killing with rapidity and with no warning or an outbreak.  Though the disease is currently quarantined to the African continent, researchers are racing to find a treatment to not only aid those who are afflicted, but to stop its spread to the rest of the world.

The report published in this week’s Proceedings of the National Academy of Sciences shows that Ebola manages to disable “a cellular protein called tetherin that normally can block the spread of virus from cell to cell.” [UPSM]  Previously it was shown that Tetherin is also compromised in HIV infections.  When working properly, Tetherin “affects the virus replication cycle after the virus is fully made and prevents the virus from being able to go off and infect the next cell.” [UPSM]  When it isn’t working properly, cells that have been infected with the virus are able to spread the disease to uninfected cells with frightening ease.

What makes Ebola such an alarming disease is that scientists have yet to discover its origins.  Though similar diseases are animal-borne (meaning they start in an animal), no one has been able to identify just what animal may be the initial carrier—if it even is truly an animal at all.  Because it isn’t known how a human first contracts the disease, it is impossible to predict when an outbreak will occur.  And it is extremely difficult to stop a disease completely if you do not even know where it starts.

Very little is known about Ebola (properly known as Ebola Hemorrhagic Fever), which was named for the river in the Congo where it was first identified.  When contracted, the disease presents with “fever, headache, joint and muscle aches, sore throat, and weakness, followed by diarrhea, vomiting, and stomach pain. A rash, red eyes, hiccups and internal and external bleeding” is also seen [CDC]. It is spread by contact with bodily fluids, such as blood or feces.  And while some are able to recover, Ebola is fatal 90% of people infected.

Until recently, there were four strains, three which infect humans (Ebola-Zaire, Ebola-Sudan, and Ebola-Ivory Coast) and an additional strain (Ebola-Reston) that only infects nonhuman primates such as gorillas and chimpanzees.  However, in late 2007 a previously unknown strain killed 37 people Uganda, prompting worry that the virus may be starting a phase of mutations which will make it even more difficult to treat by medicine.

That makes the research done by UPSM all the more important.  Dr. Paul Bates, the leader of the study, stated, “Understanding how the Ebola protein blocks the activity of tetherin may facilitate the design of therapeutics to inhibit this interaction, allowing the cell's natural defense systems to slow down viral replication and give the animal or person a chance to mount an effective antiviral response and recover.” [UPSM] Not only will this research help defeat Ebola, it may also pave the way to suppressing HIV’s interaction with tetherin, giving those suffering from the disease a better chance of responding to medication.