Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scripps Florida scientists develop a process to disrupt hepatitis C virion production

25.03.2008
Findings offer hope for new therapies

HCV is a significant human pathogen, infecting more than three percent of the world’s population. The incidence of infection in the United States has been estimated to be as high as 4 million cases.

In the March issue of the journal PLoS Pathogens, Timothy Tellinghuisen, an assistant professor in the Department of Infectology at Scripps Florida, and his colleagues describe how they used mutations of the viral NS5A phosphoprotein to disrupt virus particle production at an early stage of assembly. NS5A has long been proposed as a regulator of events in the HCV life cycle, but exactly how it orchestrates these events has been unclear.

“The interesting thing about this mutant is that while it triggers totally normal RNA replication, it causes severe defects in the output of infectious virus—in fact, it releases no infectious virus that we can detect,” says Tellinghuisen. “And though this discovery isn’t a cure for HCV, it is an important research tool that stops the assembly pathway.” Total disruption of the replication process would be a cure for the disease, he adds, and that’s the team’s long-term goal.

HCV infection is roughly five to seven times more prevalent than HIV, underscoring the pandemic nature of HCV infection. HCV occurs when blood from an infected person enters the body of someone who is not infected. Most new HCV infections are due to illegal drug injections and sharing needles. However, those who had blood transfusions prior to blood donor screening in 1991, healthcare workers who had needle stick accidents, and hemodialysis patients are also at risk for developing HCV infection. The virus predominantly infects the liver, and following many decades of virus reproduction serious disease such as hepatitis (liver inflammation), cirrhosis (liver scarring), and carcinoma (liver cancer) develop. Ultimately, HCV infection destroys the liver, resulting in death. Attempts at curing HCV infections with drug therapy have been only marginally successful.

Before more effective therapies can be developed, scientists need to understand, at the molecular level, the detailed mechanisms HCV uses to infect cells, replicate itself, assemble progeny virus, and exit the cell. Each of these processes could potentially be a target for a new drug to eliminate HCV infection. HCV, like all viruses, requires the normal cellular machinery for its replication and has developed strategies to utilize normal cell physiology for its own benefit (often to the detriment of the host).

The Tellinghuisen team, which includes Research Assistants Katie L. Foss and Jason Treadaway, has focused recent efforts on NS5A to understand the regulation of events used by the virus to assemble infectious copies of itself and exit the cell. NS5A is a three-domain protein, which means it is comprised of three compactly folded regions roughly 50 to 300 amino acids in length. The requirement of domains I and II for RNA replication is well documented. NS5A domain III, however, is not required for RNA replication, and the function of this region in the HCV life cycle is unknown.

Using standard molecular biology, the researchers removed from domain III of NS5A a coding sequence corresponding to roughly 15 amino acids. Then they generated a clone of the virus, transcribed the RNA from that clone, and purified the RNA. This RNA, which is directly infectious, was then transfected into a liver cell line where it produced all the HCV proteins that are encoded by that RNA genome.

“Those proteins assemble in the cell to make a structure called a replicase that then copies the viral RNA,” Tellinghuisen explains. “We measured that RNA accumulation and observed no defect in RNA replication, but found, surprisingly, that no infectious viral particles were released from the cells.” The team also found that no viral RNA nor nucleocapsid protein are released from cells, indicating that an early event in virus assembly had been affected.

Using genetic mapping and biochemical analyses, the authors were able to show that their deletion altered a phosphorylation signal controlling the switch from RNA replication to virus particle assembly. This signal was attributed to the activity of a cellular kinase that when inhibited by genetic or chemical means led to a reduction in infectious virus production without altering HCV RNA replication.

“These data provide the first evidence for a function of domain III of NS5A and implicate NS5A as an important regulator of the RNA replication and virion assembly of HCV,” Tellinghuisen says. “The ability to uncouple virus production from RNA replication may be useful in understanding HCV assembly and may become therapeutically important.”

Charles M. Rice, head of the Center for the Study of Hepatitis C at Rockefeller University, comments, “This is a spectacular advance linking a specific phosphorylation event by a cellular kinase to hepatitis C virus assembly. Remarkably, the target is a viral nonstructural protein, NS5A, and the data point to a pivotal role for this protein in regulating RNA amplification and infectious virus production. These new data make this multifunctional protein an even more attractive target for developing new anti-virals for treating hepatitis C.”

This project was funded by a Career Development Award from the National Institutes of Allergy and Infectious Diseases of the National Institutes of Health, and by the State of Florida.

About The Scripps Research Institute

The Scripps Research Institute is one of the world's largest independent, non-profit biomedical research organizations, at the forefront of basic biomedical science that seeks to comprehend the most fundamental processes of life. Scripps Research is internationally recognized for its discoveries in immunology, molecular and cellular biology, chemistry, neurosciences, autoimmune, cardiovascular, and infectious diseases, and synthetic vaccine development. Established in its current configuration in 1961, it employs approximately 3,000 scientists, postdoctoral fellows, scientific and other technicians, doctoral degree graduate students, and administrative and technical support personnel. Scripps Research is headquartered in La Jolla, California. It also includes Scripps Florida, whose researchers focus on basic biomedical science, drug discovery, and technology development. Currently operating from temporary facilities in Jupiter, Scripps Florida will move to its permanent campus in 2009.

For information:

Keith McKeown
858-784-8134
kmckeown@scripps.edu

Keith McKeown | EurekAlert!
Further information:
http://www.scrpps.edu

Further reports about: Cellular HCV HCV infection Infection NS5A RNA Tellinghuisen Viral develop infect replication

More articles from Life Sciences:

nachricht Individual Receptors Caught at Work
19.10.2017 | Julius-Maximilians-Universität Würzburg

nachricht Rapid environmental change makes species more vulnerable to extinction
19.10.2017 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>