RxPG News Feed for RxPG News

Medical Research Health Special Topics World
  Home
 
   Health
 Aging
 Asian Health
 Events
 Fitness
 Food & Nutrition
 Happiness
 Men's Health
 Mental Health
 Occupational Health
 Parenting
 Public Health
 Sleep Hygiene
 Women's Health
 
   Healthcare
 Africa
 Australia
 Canada Healthcare
 China Healthcare
 India Healthcare
 New Zealand
 South Africa
 UK
 USA
 World Healthcare
 
   Latest Research
 Aging
 Alternative Medicine
 Anaethesia
 Biochemistry
 Biotechnology
 Cancer
 Cardiology
 Clinical Trials
 Cytology
 Dental
 Dermatology
 Embryology
 Endocrinology
 ENT
 Environment
 Epidemiology
 Gastroenterology
 Genetics
 Gynaecology
 Haematology
 Immunology
 Infectious Diseases
 Medicine
 Metabolism
 Microbiology
  Bacteriology
  Virology
   West Nile Virus
 Musculoskeletal
 Nephrology
 Neurosciences
 Obstetrics
 Ophthalmology
 Orthopedics
 Paediatrics
 Pathology
 Pharmacology
 Physiology
 Physiotherapy
 Psychiatry
 Radiology
 Rheumatology
 Sports Medicine
 Surgery
 Toxicology
 Urology
 
   Medical News
 Awards & Prizes
 Epidemics
 Launch
 Opinion
 Professionals
 
   Special Topics
 Ethics
 Euthanasia
 Evolution
 Feature
 Odd Medical News
 Climate

Last Updated: Oct 11, 2012 - 10:22:56 PM
West Nile Virus Channel

subscribe to West Nile Virus newsletter
Latest Research : Microbiology : Virology : West Nile Virus

   EMAIL   |   PRINT
Secrets to monoclonal antibody's success against West Nile Virus

Sep 29, 2005 - 8:54:00 PM
"This was a complete surprise to us, but it gives us some very useful insights. Based on what we've learned, we are now developing therapeutic antibodies for related viruses that also are effective at stopping the process of infection after the virus attaches to host cells."

 
[RxPG] A monoclonal antibody that can effectively treat mice infected with West Nile virus has an intriguing secret: Contrary to scientists' expectations, it does not block the virus's ability to attach to host cells. Instead, the antibody somehow stops the infectious process at a later point.

"This was a complete surprise to us, but it gives us some very useful insights," says senior author Daved Fremont, Ph.D., associate professor of pathology & immunology and of biochemistry & molecular biophysics at Washington University School of Medicine in St. Louis. "Based on what we've learned, we are now developing therapeutic antibodies for related viruses that also are effective at stopping the process of infection after the virus attaches to host cells."

Detailed study of how the antibody physically binds to the virus has provided intriguing clues to how it may block infection. Scientists found evidence suggesting that the antibody prevents the virus from rearranging the protein envelope that surrounds its genetic material after it enters a host cell.

To reproduce, a virus must alter its envelope in order to inject its genetic material inside the cell. After that injection, the virus tricks the host cell into making more copies of the genetic material that can then be assembled into new viral particles or virions and sent out to infect other host cells and reproduce. But with the viral reproduction process blocked by the antibody, scientists suspect that the host cell eventually destroys the virion.

Fremont and colleagues, who publish their results in the Sept. 29 issue of Nature, hope to design a new diagnostic system that can determine whether vaccines for West Nile and related viruses undergoing clinical trials stimulate production of antibodies that stop infections at a similar point.

In 2004, West Nile virus, which is a mosquito-borne flavivirus, reportedly caused 2,470 infections and 88 deaths in the United States. First isolated in Africa in 1937, West Nile spread to the Middle East, Europe, and Asia before arriving in the United States in 1999. Most infections with the virus are mild or symptom-free, but infections in people with weakened immune systems and those over 50 sometimes lead to serious complications or death.

Like West Nile, dengue virus is a flavivirus spread by mosquito bites, but only in tropical regions of the world. The dengue virus is estimated by Centers for Disease Control and Prevention epidemiologists to cause100 million infections annually worldwide.

"Currently there are no effective and safe vaccines for pediatric dengue," says co-author Michael Diamond, M.D., Ph.D., assistant professor of molecular microbiology, of pathology & immunology and of medicine. "Thanks to our data from the West Nile virus antibody, we believe we now have a much better idea of how to evaluate vaccines for dengue."

Fremont and Diamond led a team of researchers at Washington University and Macrogenics Inc., a private company, that announced the identification of the effective West Nile antibody earlier this year. In a line of mice genetically altered to increase vulnerability to the virus, they found injection of the new antibodies could boost survival rates of mice infected with the virus to greater than 90 percent.

Scientists at Macrogenics are working on the preliminary studies required before the West Nile antibody can be tested in humans. Meanwhile, researchers at Washington University wanted to know why the new antibody was so effective.

Antibodies normally work by binding to invaders to flag them for consumption and destruction by immune system cells known as macrophages. In the prior study, which screened several potential West Nile antibodies, scientists found that all the most potent antibodies bound to a particular section of a protein that makes up the exterior of the viral envelope. The envelope of a single viral particle or virion is comprised of 180 copies of this protein.

For the new study, scientists determined the detailed structure of a single antibody bound to its envelope protein target region using the technique of protein crystallography. Scientists were able to affirm in greater detail earlier observations suggesting that the antibody will be therapeutic for all strains of West Nile Virus.

Based on this data, they predicted how multiple copies of the successful antibody would bind to a virion.

"We were startled to find that the antibody only seemed to be able to attach to 120 of the 180 copies of the target region in the complete viral envelope," says Grant Nybakken, a Washington University M.D./Ph.D. student who was lead author of the study.

Further tests showed that virions covered in infection-stopping antibodies could still bind to host cells, while antibodies that were less effective at stopping infection could more effectively prevent the virion from binding to host cells.

How does an antibody that's better at preventing the virus from binding to host cells actually turn out to be worse at treating infection? The key may lie in a theory known as antibody-dependent enhancement (ADE) of infection, which has been observed in test tube studies of dengue virus and may be important to the onset of dengue hemorrhagic fever.

This theory suggests that dengue and other viruses may have developed tricks that let them reproduce inside macrophages, the immune cells that normally consume and destroy any object that they find covered in antibodies. In effect, these tricks turn antibodies that should be death warrants into passes into cells where invaders can reproduce.

Fremont cautions that this phenomenon has not been seen in West Nile virus, but notes that when he and his colleagues tested the ability of several antibodies to prevent West Nile from reproducing inside macrophages, they found that only the therapeutic antibodies blocked the virus' reproduction. The therapeutic antibodies' ability to stop reproduction in macrophages even worked when the virions were simultaneously exposed to antibodies known to enhance infection.

"Do the therapeutic antibodies also prevent the virus from properly injecting its genetic material into macrophages? It's a tempting possibility, but we don't have the evidence to prove it yet," he says.



Publication: Nybakken GE, Oliphant T, Johnson S, Burke S, Diamond MS, and Fremont DH. Structural basis of West Nile virus neutralization by a therapeutic antibody. Nature, Sept. 29, 2005.
On the web: www.wustl.edu 

Advertise in this space for $10 per month. Contact us today.


Related West Nile Virus News
How West Nile virus evades immune defenses
Secrets to monoclonal antibody's success against West Nile Virus
Monoclonal antibody cures West Nile Virus

Subscribe to West Nile Virus Newsletter

Enter your email address:


 Additional information about the news article
Funding from the Pediatric Dengue Vaccine Research Institute, the National Institutes of Health, and the Midwest Regional Center of Excellence in Biodefense and Emerging Infectious Diseases Research supported this research.

Washington University School of Medicine's full-time and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked third in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.
 Feedback
For any corrections of factual information, to contact the editors or to send any medical news or health news press releases, use feedback form

Top of Page

 
Contact us

RxPG Online

Nerve

 

    Full Text RSS

© All rights reserved by RxPG Medical Solutions Private Limited (India)