Researchers Develop Treatment That Neutralizes Ebola Virus

RNA-based therapy worked on monkeys and is now being tested on people; meanwhile CDC warns against unprotected sex with recovered patients.

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James Dorbor, 8, being carried to an Ebola treatment center in Monrovia, Liberia: part of a Pulitzer-winning series by NYT photographer Daniel Berehulak.Credit: AP

A collaboration of academia and business has developed a drug to treat Ebola, which has proven successful in animal models – meaning it helped primates infected with the disease.

The treatment was specifically developed for the "Makona" strain of Ebola that killed over 10,000 people in West Africa from December 2013 to date.
The therapy does not kill the virus: it effectively renders the virus paralyzed, and harmless.

There are no cures as such for diseases caused by viruses, which not only infect our bodies – they infect our very cells. That is in fact their whole raised d'etre: while other parasites reproduce on their own, viruses can only reproduce by "hijacking" the cellular mechanisms, which instead of producing things our bodies need, produce new virus particles.

Another useful factoid is that the Ebola virus contains DNA (other viruses contain only RNA). When the virus injects its DNA into the right kind of host cell, that DNA gets expressed (instead of the cell's DNA) as RNA, which in turn gets expressed as proteins. One corollary of these natural processes is that specific strands of RNA will stick to specific strands of DNA.

What the researchers from the University of Texas Medical Branch and the biopharmaceuticals company Tekmira Pharmaceuticals Corp. did, as reported in Nature today, is to make a strand of RNA that "paralyzes" the Ebola viral DNA, rendering it harmless.

The RNA strand they developed – a kind of "siRNA," or "small interfering RNA" - has been tested on sick animals. Testing on actual people is just starting, in Sierra Leone. But the news is good not only for sufferers of Makona: based on the advancements in genetic manipulation techniques, siRNA strands can be built and adapted quite quickly to different strains of virus.

UTMB professor of microbiology and immunology Thomas Geisbert said the siRNA demonstrated that it could protect primate subjects against a lethal Makona infection when treatment began three days following infection. "At this point, those infected showed clinical signs of disease and had detectable levels of virus in their blood," he stated.

All the animals on which the drug was tested had advanced Ebola, which is a hemorrhagic fever with mortality rates of between 50% to 90%, depending on the strain. But the apes that received the siRNA treatment had milder symptoms relative to untreated apes, and recovered fully, the scientists said.

The untreated animals died after eight or nine days, which is similar to reports of the epidemic in human populations.

This siRNA treatment also proved to protect the apes against the liver and kidney dysfunction typical of Ebola, the scientists said.

"This study demonstrates that we can rapidly and accurately adapt our siRNA-LNP technology to target genetic sequences emerging from new Ebola virus outbreaks," said Dr. Mark Murray, president and CEO of Tekmira Pharmaceuticals in a statement.

CDC bans unprotected sex after infection

The Ebola virus is not "native" to humans, but over the years, certain strains have made the interspecies leap. The source of the Makona strain is unknown, though some suspect fruit bats are involved. This outbreak began in Guinea and quickly spread to the neighboring countries of Liberia and Sierra Leone, which is where almost all the deaths occurred.

As this had been the worst-ever known outbreak of the disease known so far, an international panic ensued, leading to measures that some authorities now suspect were overdone – in the sense that heavy investment was made in preventative measures and in preparing isolation units for travelers suspected to have caught the disease, of which little to no use has been made.

As of writing the disease seems to have halted in Liberia but new cases have been reported in Sierra Leone and Guinea. Some cases had been reported in Nigeria, Senegal and Mali, but the disease was contained, and travelers bringing Ebola were recorded in the U.S., UK and Spain.

More recently, the question in the spotlight is whether Ebola survivors become carriers – who can infect others through sex.

Normally, Ebola is either caught from the primary source (a fruit bat, monkey or whatever), or physical contact with the body fluids of an infected human. The question is now whether after recovery, the patient continues to carry the virus and whether others can be infected.

following a case in Liberia where a survivor is suspected of infecting his lover months after his recovery (she could theoretically have caught the disease otherwise), for the sake of caution, earlier this week the U.S. Centers for Disease Control and Prevention changed its guideline.

The new guideline is basically a blanket ban: "Because sexual transmission of Ebola cannot be ruled out, Ebola survivors should not have sex (oral, vaginal, or anal) until more information becomes available. Those who do have sex should use a condom correctly and consistently every time they have sex," the CDC wrote, without placing a limit in time.

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