MedicineWorld.Org
Your gateway to the world of medicine
Home
News
Cancer News
About Us
Cancer
Health Professionals
Patients and public
Contact Us
Disclaimer

Medicineworld.org: Optimizing Immune Response Viral Infections

Back to research news Blogs list Cancer blog  


Subscribe To Research News RSS Feed  RSS content feed What is RSS feed?






Optimizing Immune Response Viral Infections

Optimizing Immune Response Viral Infections Gordon Freeman, PhD
Like boxers wearied by a 15-round bout, the immune system's CD8 T cells eventually become "exhausted" in their battle against persistent viral infection, and less effective in fighting the disease.

In a study would be published Dec. 28 on the journal Nature's website, scientists at Dana-Farber Cancer Institute and Emory University have traced the problem to a gene that turns off the infection-fighting drive of CD8 T cells in mice. The discovery raises the possibility that CD8 cell exhaustion can be reversed in human patients, reinvigorating the immune system's defenses against chronic viral infections ranging from hepatitis to HIV, the virus that causes AIDS.

"CD8 T cells that have fought viral infections retain a 'memory' of the viruses they've encountered, so they can rapidly respond to new infections from those viruses," says the study's author, Gordon Freeman, PhD, of Dana-Farber. In the case of chronic infection, however, senior author Rafi Ahmed, PhD, of Emory, has shown that memory cells become exhausted and lose the capacity to respond to the virus. Why this occurs, on a molecular level, has been unclear.

To find the cause, Freeman and colleagues conducted a "microarray" experiment measuring the activity of thousands of genes in normal memory CD8 T cells in mice and in "exhausted" versions of those cells. They found that a gene known as PD-1 was much more active in the exhausted cells.

From prior research, Freeman's team knew that PD-1 is responsible for a specialized "receptor" in CD8 cells - a tiny socket for receiving signals from other cells. In 2001, Freeman and colleagues showed that when the PD-1 receptor latches onto a molecule called PD-L1, the immune system's response to infection is weakened. Freeman's team made antibodies to block this interaction.

"When [co-author] John Wherry of the Wistar Institute found a high level of the PD-1 gene in microarray experiments, we wanted to test whether this was contributing to the CD8 exhaustion," says Freeman, who is also an assistant professor of medicine at Harvard Medical School. "We found that exhausted CD8 T cells in mice have uncommonly large numbers of PD-1 receptors, and blocking the PD-1/PD-L1 bond reactivated the cells' response to infection."

Just as strikingly, scientists found that even in persistently infected mice that lacked a type of T cell known as helper CD4, preventing PD-1 from binding to PD-L1 had a beneficial effect on "helpless" CD8 T cells - restoring their ability to kill infected cells and release infection-fighting substances called cytokines, substantially reducing the animals' "viral load."

Eventhough it's not known why CD8 cells become exhausted - roughly a month after infection begins - researchers theorize that it may be part of the body's system for naturally ending the immune response after an infection has been quelled. If it persists too long, the immune response can damage normal, healthy tissue. In the mouse studies, CD8 T cells were reinvigorated only as long as scientists continued to administer PD-1/PD-L1 blockers, so the chance of sparking a runaway immune response seems unlikely.

If human CD8 T cells are found to operate by a mechanism similar to that in mice, the new findings may offer a simple immunological strategy for treating chronic viral infections. Freeman's lab is also exploring whether anti-cancer T cells become exhausted in various types of tumors and in HIV-infected individuals.

"The potential applications of this work are wide-ranging," Freeman remarks, noting that he and his collaborators have recently received a grant from the Bill and Melinda Gates Foundation's Grand Challenges in Global Health program to extend their findings to hepatitis C infection.

The study's first author is Daniel Barber, PhD, of Emory University School of Medicine.

In addition to Freeman, Ahmed and Wherry, the study's other authors are David Masopust, PhD, of Emory; Baogong Zhu, MD, of Dana-Farber; James Allison, PhD, of Memorial Sloan-Kettering Cancer Center in New York; and Arlene Sharpe, MD, PhD, of Brigham and Women's Hospital in Boston.

The research was supported in part by the Bill and Melinda Gates Foundation's Grand Challenges in Global Health initiative, the National Institutes of Health, Howard Hughes Medical Institute, and Cancer Research Institute.
Dana-Farber Cancer Institute (www.danafarber.org) is a principal teaching affiliate of the Harvard Medical School and is among the leading cancer research and care centers in the United States. It is a founding member of the Dana-Farber/Harvard Cancer Center (DF/HCC), designated a comprehensive cancer center by the National Cancer Institute.

Source: Dana-Farber Cancer Institute

Posted By: Scott




Did you know?
Like boxers wearied by a 15-round bout, the immune system's CD8 T cells eventually become "exhausted" in their battle against persistent viral infection, and less effective in fighting the disease. In a study would be published Dec. 28 on the journal Nature's website, scientists at Dana-Farber Cancer Institute and Emory University have traced the problem to a gene that turns off the infection-fighting drive of CD8 T cells in mice. The discovery raises the possibility that CD8 cell exhaustion can be reversed in human patients, reinvigorating the immune system's defenses against chronic viral infections ranging from hepatitis to HIV, the virus that causes AIDS.

Medicineworld.org: Optimizing Immune Response Viral Infections

Acute bacterial meningitis| Alzheimer's disease| Carpal tunnel syndrome| Cerebral aneurysms| Cerebral palsy| Chronic fatigue syndrome| Cluster headache| Dementia| Epilepsy seizure disorders| Febrile seizures| Guillain barre syndrome| Head injury| Hydrocephalus| Neurology| Insomnia| Low backache| Mental retardation| Migraine headaches| Multiple sclerosis| Myasthenia gravis| Neurological manifestations of aids| Parkinsonism parkinson's disease| Personality disorders| Sleep disorders insomnia| Syncope| Trigeminal neuralgia| Vertigo|

Copyright statement
The contents of this web page are protected. Legal action may follow for reproduction of materials without permission.