April 29, 2014
Two Separate Studies On MERS-Coronavirus Offer Better Understanding Of Newly Emerging Disease
Lawrence LeBlond for redOrbit.com - Your Universe Online
Two separate studies this week are helping scientists gain a better understanding of the dangerous Middle East respiratory syndrome (MERS) coronavirus, a disease that has sickened more than 300 people and left at least a hundred dead since it was first reported in September 2012.
The first study comes from scientists at Dana-Farber Cancer Institute who have identified natural human antibodies against the virus that causes MERS, a step that could help in the development of new treatments against the newly emerging disease.
Currently there is no vaccine or antiviral treatment for MERS, which has a mortality rate of more than 40 percent.
The team, led by Wayne Marasco, MD, an infectious expert at Dana-Farber, found that these “neutralizing” antibodies prevented a key part of the virus from attaching to protein receptors that allow the virus to infect human cells. Their findings are published in the Proceedings of the National Academy of Sciences.
"This panel of neutralizing antibodies offers the possibility of developing human monoclonal antibody-based immunotherapy, especially for health care workers," noted the authors.
Marasco and colleagues discovered the MERS antibodies using a “library” of some 27 billion human antibodies they had created and maintained in a freezer at the lab – this is one of the largest such libraries in the world, note the authors.
The research team took seven MERS-specific neutralizing antibodies from the library after using samples of the virus to screen for them.
MERS coronavirus “has on its surface an array of spike-shaped proteins that bind to host cells – specifically to receptor proteins called DPP4 on the surface of cells that line human airways. The neutralizing antibodies identified in the study prevented the virus' spikes from binding to the DPP4 receptors,” wrote the authors.
The researchers selected one of the antibodies, labeled 3b11, as a lead candidate for further research. The antibody has been produced in sufficient quantities to begin testing in non-human primates and mice to determine if they protect against the virus, according to Marasco. However, the studies have been delayed because no good animal model for MERS has been developed.
Marasco said that an antibody-based treatment for MERS would be administered by injection and may provide protection from the disease for about three weeks.
A second study this week has found more definitive evidence linking camels to the ongoing MERS outbreak.
Camels have been one of the key targets of concern since a study last August found MERS antibodies in camels that were similar to the disease in humans. Subsequent research found evidence of the disease in camels and several human cases have been reported after close contact with the dromedary animals since.
In this latest camel study, scientists from the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health, King Saud University, and EcoHealth Alliance extracted a complete, live, infectious sample of MERS coronavirus from two camels in Saudi Arabia. A lab analysis of the sample matched MERS coronavirus found in humans, indicating that the virus in camels is capable of infecting humans and could very well be the source of the outbreak.
The team, publishing a paper in the journal mBio, examined nasal samples collected during a countrywide survey of camels and selected samples from two animals with the highest viral load. They obtained complete genomic sequence from both animals as well as the virus from nasal samples of several other camels.
The consensus genomic sequences were consistent with viruses found in human cases; however, the researchers noted that samples from camels contained more than one virus genotype. Over the course of 48 hours of culture in primate cells, the genomic variation of viruses narrowed, mirroring the lower sequence diversity found in humans with MERS.
"The finding of infectious virus strengthens the argument that dromedary camels are reservoirs for MERS-CoV," said first author Thomas Briese, PhD, associate director of the Center for Infection and Immunity and associate professor of Epidemiology at the Mailman School. "The narrow range of MERS viruses in humans and a very broad range in camels may explain in part the why human disease is uncommon: because only a few genotypes are capable of cross species transmission."
"Given these new data, we are now investigating potential routes for human infection through exposure to camel milk or meat products," said co-author Abdulaziz N. Alagaili, PhD, director of the Mammals Research Chair at King Saud University. "This report builds on work published earlier this year when our team found that three-quarters of camels in Saudi Arabia carry MERS virus."
MERS IN EGYPT
The first case of a dangerous SARS-like virus has been reported in Egypt, the state news agency MENA said on Saturday, as reported by the Associated Press.
The cases occurred in a 27-year-old civil engineer who was diagnosed April 26 after returning from Saudi Arabia, where MERS is prevalent. MENA said the man was quarantined upon his arrival at Cairo airport Friday and transported to a local hospital. He was reportedly being treated for pneumonia and was in stable condition at last report.
Egypt becomes the 15th country to report a MERS case and the latest one outside the Arabian Peninsula. Concerns have been rising in Egypt because of the recent evidence of the virus in camels there.
According to Saudi Arabia’s Ministry of Health, five more people in the kingdom have died from MERS as of Sunday, April 27. The ministry said that 92 people have died and 313 have contracted the virus since September 2012.
The World Health Organization (WHO) had released its number on Saturday, April 26, stating that 261 cases have been reported along with 93 deaths (the agency doesn’t always recognize all reports immediately from government and media sources).