Genomics Revolution

Guest Hosts: Matthew Hecker & Miranda Mordue

Episode 54: MERS Coronavirus- Middle East Respiratory Syndrome-related coronavirus

 

Hello, and welcome to Genomics Revolution.  This is Matthew Hecker, and this is Miranda Mordue, bringing you in from the Hiram College Genetics course of 2020. 

 

As we stand in April 2020, the world is currently in a state of flux with COVID-19, a novel coronavirus that is taking the world by storm, and not in a good way.  In light of COVID-19, our topic for today is another variety of novel coronavirus, MERS-Coronavirus.  This stands for Middle East Respiratory syndrome coronavirus, but we’ll be calling it MERS from here on out.

 

MERS was first reported in 2012 in Saudi Arabia in the respiratory tract of a businessman who had died from viral pneumonia.  It was the first highly pathogenic coronavirus since the SARS coronavirus in 2003.  This virus had a very high mortality rate of greater than 35%. 

 

The MERS genome is single stranded RNA and is made up of about 30,000 bases.  Though sometimes it is difficult to think about the scale of genetics, this is a relatively small genome size that contains only 10 Open Reading Frames, or ORFs.  Each of these ORFS is a section in which transcription can occur.  One of these ORFs encodes for a “polyprotein.”  This is a large encoded structure that can be cleaved in order to serve different purposes, basically a conglomeration of different proteins that can be broken up and used as necessary.  In the case of MERS, this polyprotein encodes viral replicase and the methods of interaction with ribosomes.  Basically, this polyprotein is what allows for the infection and takeover of host cells to replicate itself, while the rest of the ORFs translate to structural and functional proteins.  These other proteins are responsible for getting the polyprotein into host cells. 

 

Knowing this, what else can genetics tell us about MERS?  Based on genomic comparison, it is very likely that the strain of MERS that eventually came to affect humans began development in the dromedary camel.  With MERS, the evidence of human to human transmission is differing based on location the virus was found.  In Riyadh, there were cases of human transmission, but in other places, it was not observed.  This means that some of the infections of humans beyond the initial case are a result of contact with livestock. 

 

Because of this discreet infection from various sources, it was actually discover that that are many different strains of MERS.  In a study from 2013, 21 samples of MERS were examined from different patients, and 10 different genomes were produced for the virus.  This means that MERS infections are not limited to human contact and this will obviously affect the manner in which the virus must be addressed.

 

MERS has also shown some resistance to the innate immune response of the body.  The codon selectivity in MERS is variable in three genetic clusters, which have developed a codon bias to survive inside the host.  By using different codon sequences, the immune system is not able to recognize the virus as effectively.  In different strains, this leads to adaptation to resist the human immune system, making MERS a more dangerous virus. 

 

As of now, there is no specific “cure” for MERS, but levels of infection remain relatively low due to low human to human transmission in strains, as well as potentially lethal symptoms from the onset which cause quarantining very quickly.

 

I’d hate to end on too negative a note, so let me just say this: Scientists all over the world are very capable at what they do, and they will be able to figure out a way to defeat MERS, as well as the current COVID-19.  Just remember to continue listening and learning!  Thank you all for listening!  This has been Genomics Revolution.

 

 

Sources:

1)     Cotten et al., 2013. The Lancet Vol 382, pp 1993-2002. Transmission and  evolution of the Middle East Respiratory syndrome coronavirus in Saudi Arabia: A descriptive Genomics Study.

2)     Alnazawi et al., 2017. Biol. Pharm. Bull. Vol 40 pp 1289-1298. Comparative Genomic Analysis MERS CoV Isolated from Humans and Camels with Special Reference to Virus Encoded Helicase. 

3)     Shapiro et al., 2016. Disaster and Military Medicine 2:9. Middle EAst Respiratory Syndrome Coronavirus: A Review of the Current Situation in the World.

4)     Chafekar, A., & Fielding, B. C., 2018. Viruses vol. 10,2 93. MERS-CoV: Understanding the Latest Human Coronavirus Threat.