Science news from the Bond LSC



NEW GRANT WILL FUND IMPORTANT BATTLE IN WAR ON VIRUSES

Bond Center scientist and Japanese colleagues are closing in on an antibody to fight HIV


October 20, 2010
Denise Henderson Vaughn

 


Unraveling the mysterious XMRV virus

 

Milestone recently achieved as researchers "solve the structure" of one XMRV protein

Work with the XMRV virus is "potentially explosively important," Sarafianos said. The letters stand for Xenotropic Murine-Leukemia-Virus Related Virus, and it's the third-ever retrovirus that targets humans, he said. The other two are HIV and HTLV, a virus associated with certain types of leukemia and lymphoma.

Currently no clinical test exists to determine if a person carries XMRV, nor do scientists know exactly what the virus does to the body, but "it could be in the blood supply," he said. No links to specific diseases have been positively established yet; however, the virus is subject to intense research by government medical scientists, who are looking into possible relationships between XMRV and prostate cancer and/or chronic fatigue, he said.

Sarafianos' lab is investigatating compounds that could inhibit the XMRV virus from reproducing itself. If XMRV is found to indeed be causing the above diseases or others, scientists will have a jump on developing treatment, he said.

Just recently, Sarafianos' lab "solved the crystal structure" of one of the proteins within the XMRV virus, he said. This particular protein is required for viral replication and could be a good target for potential antiviral therapies, he said.

In this case, "solving the structure" means identifying the protein's three-dimensional detailed shape so accurately that researchers will be able to design a molecule which can bind tightly to that protein and potently block its biological activity, he said.

"It's like a lock and key. If we know what the lock looks like, we can make the key," Sarafianos said. "So information on the structure is important. It guides design for structure-based drugs."

This is the first XMRV protein for which the structure has been solved by any research group, anywhere, he said.

Collaborators on the XMRV research are Donald Burke, Marc Johnson, and Shan-Lu Liu, who are also Bond Life Sciences Center investigators. They all work in the molecular microbiology and immunology department at the University of Missouri.

 

Stefan Sarafianos and his lab team members are working toward developing antibodies that will prevent the HIV virus from entering human cells, and last month the National Institute of Health (NIH) awarded him a two-year $400,000-plus grant to support that effort.

Antibodies have long been used to produce immunizations to protect against other diseases, but until fairly recently the complex HIV virus has foiled all attempts to develop an effective vaccine.

Dr. Stefan Sarafianos
Stefan Sarafianos

Several years ago Japanese researchers made a breakthrough, creating KD-747, an antibody that successfully blocks HIV virus, Sarafianos said. But this product only stops one type of HIV virus, known as Clade B, which is typically found in the U.S., Australia, Europe and Japan.

Sarafianos' mission is to modify the KD-747 antibody so that it also blocks a second type of HIV virus, Clade C, which is found primarily in Africa, and which affects about 80 percent of all HIV patients worldwide, he said. If his team designs an effective antibody, that should help efforts to produce a vaccine, he said.

Sarafianos is assistant professor of molecular microbiology and immunology at the MU School of Medicine and an investigator with the Bond Life Sciences Center. He is working cooperatively on the NIH grant with one of KD-747's creators, Shuzo Matsushita of Kumamoto University in Japan.

His lab's researchers are going beyond developing one antibody for one specific disease, Sarafianos said. They're "tinkering with antibody structure" in ways previously untried, and these methods could be put to use in future projects.

"This is cutting edge," Sarafianos said. "We hope to find novel ways to design antibody-based therapeutics. Today it's HIV. Tomorrow, it's the next disease, maybe cancer."

 

Waging virus wars on three fronts

Developing an antibody that stops new HIV infections represents only about five percent of the activities carried out by Sarafianos' lab, located on the fourth floor at the Bond Center.

By directing the 20-member lab, Sarafianos is a leader in a fight against a variety of viruses, attacking them in three ways. Using antibodies to stop viruses from entering host cells is one important approach. But if viruses do infect a cell, the second defense is to prevent them from replicating. The third effort is to create microbicides - substances that kill viruses.

Sarafianos uses combinations of these three methods to attack not only HIV, but also SARS, Hepatitis B, Foot and Mouth Disease virus, and the relatively unknown but potentially troublesome XMRV virus.

"Scientific discoveries nowadays are typically a team effort," said Sarafianos. He's referring to collaborations with researchers worldwide; this approach expedites progress, encourages peer exchanges and allows specialists to contribute to a bigger effort.

 

EFdA: an effective HIV weapon

A few years back, researchers in Japan and NIH developed EFdA. It's a molecule that mimics the building blocks that are used by the HIV virus to make copies of its own DNA, Sarafianos said. Once this molecule has entered into the viral DNA, then HIV can't multiply anymore, and its numbers remain few enough that the body's immune system can keep them under control, he said.

Sarafianos is collaborating with the scientist who created EFdA, Hiroaki Mitsuya, at the National Cancer Institute, Bethesda, Maryland. Sarafianos has taken Mitsuya's EFdA research a step further. "We discovered how it works, its mechanism for action," he said. His lab, funded by a $1.8 million grant from NIH, is now digging deeper into EFdA, to more fully understand how it acts to stop HIV and in what situations HIV might be resistant to treatment with EFdA, he said.

Compared to drugs currently used to treat HIV, EFdA remains active for longer periods of time and is much more potent, Sarafianos said.

Another research collaborator, Michael Parniak at the University of Pittsburgh, is working to develop additional uses for EFdA, Sarafianos said. Within the next few years, EFdA could be a component in a topical "microbicide" employed to prevent new HIV cases. For example, a woman whose husband is infected could protect herself with a vaginal gel. Use of EFdA in therapeutics to treat infected patients is also being explored.

EFdA is currently being experimentally tested in animals, Sarafianos said. Collaborators hope that a pharmaceutical company might develop it as a drug. That's an expensive enterprise, requiring an average of $800 million for a company to conduct clinical trials and then put a new drug on the market, he said.

 

Preparing for SARS to pack a new punch

Severe Acute Respiratory Syndrome (SARS) is not creating widespread problems at this time, but it could easily re-emerge from natural reservoirs, Sarafianos said. Currently no vaccines or drugs are available to treat it.

Working with collaborators, Sarafianos and his lab team have discovered three inhibitors that efficiently block SARS, preventing the virus from entering and infecting cells. They are also trying to identify an inhibitor that targets a specific enzyme that the virus needs to replicate itself, he said. Collaborators are Susan Weiss at the University of Pennsylvania and Colleen Jonsson at the University of Louisville.

 

New attack plan needed for resistant Hepatitis B virus

Even though a Hepatitis B vaccine is available, this disease actively infects over 300 million people worldwide, and some 1.2 million Americans are infected. New drugs are needed, because of resistance to existing drugs, Sarafianos said.

Sarafianos' team is working toward discovering Hepatitis B inhibitors that act through new mechanisms, and these inhibitors are expected to have different resistance patterns. They would be used to complement existing therapeutics, he said. Collaborators on this project are Michael Parniak at the University of Pittsburgh and John Tavis at St. Louis University.

 

Foot and Mouth Disease

This viral disease affects animals with cloven hoofs, including cattle, sheep, goats, and even deer. There is no cure; whole herds are typically destroyed to prevent its spread. While no U.S. cases have surfaced in recent years, it wrecked havoc in England a few years back.

A vaccine is available, but it only prevents one type of the 60 variations of the virus that causes foot and mouth disease, Sarafianos said. The vaccine is not used in the U.S. because a vaccinated animal will test positive for the disease, and there is no way to ascertain whether a positive test is pointing to vaccine antibodies or the real disease, which could be caused by any one of the other 59 types.

Sarafianos' lab has identified a substance that inhibits the foot and mouth disease virus from replicating itself; it is expected to work on all 60 varieties, he said. He is working with the U.S. government on this project, and the expected product will be a patented compound which will kill or suppress this contagious and potentially devastating livestock disease, he said.

Collaborators on this research are Mark McIntosh, professor and chair of the molecular microbiology and immunology department at the University of Missouri, and Elizabeth Reider at the Plum Island Animal Disease Center in New York.

Update 12/15/2010: See related story at MU School of Medicine News