Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How do the rules of immunity change during chronic infections?

11.04.2007
New study finds an altered immune response to viruses like HIV and hepatitis C

After a viral infection, a small percentage of the T cells generated to kill virus-infected cells remain on guard to establish long-term immunity. These so-called memory T cells, which derive from a family of immune cells known as CD8 T cells, engage in a self-renewal process that is essential to their persistence. This ongoing process ensures effective protection against any repeat infection by the same virus, even decades later.

But not all infections are equal. While most viral infections are cleared from the body within a few days or weeks, some infections, such as HIV or hepatitis C infections, become chronic. Some studies have suggested that the virus-specific CD8 T cells generated during a chronic infection may not develop the same characteristics as the CD8 T cells that persist after an acute infection.

Now, scientists at The Wistar Institute have found that the CD8 T cells generated to fight a chronic infection operate under an entirely different maintenance scheme than do the CD8 T cells that become memory T cells following an acute infection, becoming wholly dependent upon the presence of virus for their continuation. Details of the study will appear in the April 16 issue of The Journal of Experimental Medicine, published online April 9.

In addition, the CD8 T cells maintained during chronic infections establish a distinct pattern of cell division that creates a rapid turnover of cells, a characteristic that could be manipulated to design new therapeutic options for chronic infections, says E. John Wherry, Ph.D., senior author on the study and an assistant professor in the Immunology Program at Wistar.

"It appears the immune system responds to viral infections with two very different cell types," Wherry says. "In one case, when virus is completely cleared, you have a memory T cell capable of self-renewal. But during chronic infection, you have a totally different type of T cell that is not governed by the same pathways and mechanisms."

Understanding how the body’s immune response operates during chronic infections, and why it fails to clear these infections, could help scientists design more effective therapies to fight chronic infections and certain types of tumors, says Wherry.

In previous studies, Wherry had shown that chronically stimulated CD8 T cells were unable to undergo the slow, steady self-renewal process used by the CD8 T cells that persist as memory T cells after an acute infection. In addition, his studies showed that CD8 T cells associated with chronic infections responded poorly to IL-7 and IL-15, growth factors needed to maintain memory T cells after an acute infection. He theorized that prolonged exposure to the virus might prevent the development of normal memory T cells.

To test his theory, Wherry and his group infected mice with a virus that simulates a chronic infection. The scientists then treated the mice to clear the virus from their systems. When the virus was cleared, the CD8 T cells that had partial function also disappeared. By not going through the normal process of self-renewal, the disappearing T cells left the mice with no long-term immunity.

"The findings suggest that we’re caught in an immunological catch-22 with chronic infections," Wherry says. "The persistence of the virus is inactivating the T cells, yet the T cells are now dependent on the persisting virus for their maintenance."

The study also showed that over a four-week period, the CD8 T cells generated to fight the virus had divided five to six times, yet the number of these T cells remained relatively stable. Wherry says this observation suggests that either a very small subset of the cells are recruited to divide or that the virus-driven division of this T cell population is accompanied by extensive cell death.

Though these questions remain to be answered, the findings have implications for developing treatments for patients with chronic infections, Wherry says. "The results suggest that the rate of proliferation or cell death could perhaps be modulated to alter the size or quality of virus-specific CD8 T cell populations during persisting infections."

Franklin Hoke | EurekAlert!
Further information:
http://www.wistar.org

Further reports about: CD8 T cells Wherry chronic infections viral infection

More articles from Life Sciences:

nachricht Kidney tumor: Genetic trigger discovered
18.06.2018 | Julius-Maximilians-Universität Würzburg

nachricht New type of photosynthesis discovered
18.06.2018 | Imperial College London

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

Im Focus: Water is not the same as water

Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.

From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Novel method for investigating pore geometry in rocks

18.06.2018 | Earth Sciences

Diamond watch components

18.06.2018 | Process Engineering

New type of photosynthesis discovered

18.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>