No specific drugs exist to work against coronaviruses - the pathogens behind severe acute respiratory syndrome and Middle East respiratory syndrome - but research published in the journal PLOS Pathogens unveils a new coronavirus inhibitor.
Prior to the 2003 severe acute respiratory syndrome (SARS) epidemic, coronaviruses were not regarded as a threat to humans. Only two coronaviruses were known to be in circulation in humans, both of which caused only relatively mild, common cold-type symptoms.
The recent concern over Middle East respiratory syndrome (MERS), another highly pathogenic coronavirus, has made the need for drug treatments that can effectively combat coronaviruses ever more pressing.
An international team of scientists, led by representatives of the University of Gothenburg in Sweden and the University of Berne in Switzerland, have now identified a compound that they say inhibits coronaviruses.
In initial experiments, the researchers found that the compound - called K22 - displayed antiviral properties against a mild, cold-like coronavirus.
Follow-up experiments confirmed that K22 is also effective against all other coronaviruses, including SARS and MERS. K22 also appeared to inhibit viruses in cells lining the human airways - a natural entry point for respiratory viruses.
Experiments confirmed that K22 is effective against all coronaviruses, including SARS and MERS.
The researchers found that K22 prevents host membranes from being "re-shaped" by the attacking virus. A coronavirus alters the membranes in host cells by building a scaffolding of sorts in order to multiply and spread the infection. By blocking this scaffolding action, K22 is able to prevent the virus from reproducing.
The authors explain:
"The remarkable efficacy of K22-mediated inhibition of coronavirus replication confirms that the employment of host cell membranes for viral RNA synthesis is a crucial step in the coronavirus life cycle, and importantly, demonstrates that this step is extremely vulnerable and also druggable for antiviral intervention."
The authors also remind that the identification of K22 is only the first, preclinical step towards a treatment for coronaviruses.
"One important lesson of the past SARS and recent MERS coronavirus outbreaks," they say, "is the need to invest significant efforts to developing efficacious and approved drugs to increase preparedness and combat coronavirus infections."
Concern over MERS has prompted a rush to develop treatments
The news earlier this month that two cases of MERS had been confirmed within the US was met with concern. However, the World Health Organization (WHO) have stated that the conditions for a Public Health Emergency of International Concern have "not yet been met."
In response to the MERS outbreak, other researchers - such as those from Purdue University in Indiana - are also examining alternative approaches to stopping potentially deadly coronaviruses. The Purdue team are creating molecules designed to "shut down" the MERS coronavirus.
Team leader Prof. Andrew Mesecar explains that the molecule does this by targeting a key enzyme crucial to the survival of the virus:
"This enzyme has a big mouth that, in a way, allows it to chew up other proteins the virus needs to live. How do we stop a big mouth from chewing things up? We stuff it full of something else. That is what the molecules we invent do. If you can shut down this critical enzyme, you can effectively shut down the virus."