Featured Research

from universities, journals, and other organizations

Exhaustion Of HIV-specific T Cells May Be Caused By Chronic Exposure To Virus

Date:
May 6, 2008
Source:
Massachusetts General Hospital
Summary:
The "exhaustion" of immune cells that target HIV appears to result from chronic exposure to the virus, specifically exposure to the protein segments targeted by the pathogen-killing HIV-specific CD8 T cells. A study from researchers at the Partners AIDS Research Center at Massachusetts General Hospital may have answered a key question: whether the functional impairment of these T cells is the cause or the result of unchecked viral replication in chronic progressive HIV-1 infection?

The "exhaustion" of immune cells that target HIV appears to result from chronic exposure to the virus, specifically exposure to the particular protein segments targeted by the pathogen-killing HIV-specific CD8 T cells. A study from researchers at the Partners AIDS Research Center at Massachusetts General Hospital (PARC-MGH), appearing in PLoS Medicine, may have answered a key question regarding the immune response to HIV infection: is the functional impairment of HIV-specific cytotoxic T lymphocytes (CTLs) the cause or the result of unchecked viral replication in chronic progressive HIV-1 infection?

"Although we know that CTLs can control replication of HIV, we still don't know which particular features of the CTL response are key to this control," says Hendrik Streeck, MD, of PARC-MGH, the paper's lead author. "Better understanding how the quality of the T-cell response changes during HIV infection will be necessary for the design of effective T-cell-based vaccines against HIV."

Previous research has shown that, in most HIV-infected individuals, HIV-specific CTLs gradually lose their ability to proliferate and secrete the cell-killing substances called cytokines as infection proceeds. In parallel, the immune system's ability to control viral replication diminishes over time. It was not clear, however, whether the exhaustion of HIV-specific CTLs was caused by or resulted from persistent viral replication. The PARC-MGH team study was designed to address that very issue.

The study enrolled 18 participants who had recently become infected with HIV. Antiviral treatment was started in 7 participants, while 11 remained untreated during the study period. During the following months, the researchers monitored participants' viral loads and also analyzed the ability of their CTLs to respond to the specific viral protein segments against which the cells were targeted. In participants who received antiviral treatment, viral loads quickly dropped to undetectable levels, and HIV-specific CTLs maintained or even improved their response against their target proteins during the four month after study enrollment.

Viral loads in untreated participants gradually rose during the eight months after enrollment, and during that time HIV-specific CTLs gradually lost functional capacity. To further investigate the interaction between CTLs and their target viral peptides, researchers examined what happened when target peptides mutated and were no longer recognized by the T cells. In that situation, CTLs specific for the original version of the mutated peptides regained their functional capacity, but CTLs targeted against unchanged peptides continued in an exhausted state. These results support the theory that it is persistent contact with the peptide antigen that leads to CTL exhaustion.

"To understand what's happening in any battle, you need to know what's going on with the soldiers as well as with the enemy, so investigating the nature of CTL responses in HIV infection requires monitoring both virus and host responses simultaneously," Streeck says. "Therefore, it is important that HIV vaccine trials evaluate the immune responses carefully in the context of the virus, as the virus might already have evolved. The inability of the vaccine-induced immune response to cross-recognize the infecting virus might actually have contributed to the failure of recent HIV vaccine trials." Streeck is a research fellow in Medicine at Harvard Medical School.

Journal reference: Streeck H, Brumme ZL, Anastario M, Cohen KW, Jolin JS, et al. (2008) Antigen load and viral sequence diversification determine the functional profile of HIV-1-- specific CD8 T cells. PLoS Med 5(5):e100.

The senior author of the PLoS Medicine report is Marcus Altfeld, MD, PhD, of PARC-MGH. Additional co-authors are Zabrina Brumme, PhD, Kristin Cohen, Jonathan Jolin, Angela Meier, MD, Chanson Brumme, Eric Rosenberg, MD, Galit Alter, PhD, Todd Allen, PhD and Bruce Walker, MD, of MGH-PARC, and Michael Anastario, PhD, Uniformed Services University of the Health Sciences. The study was supported by funding from the National Institutes of Health, the German Academic Exchange Service, and the Canadian Institutes of Health Research.


Story Source:

The above story is based on materials provided by Massachusetts General Hospital. Note: Materials may be edited for content and length.


Cite This Page:

Massachusetts General Hospital. "Exhaustion Of HIV-specific T Cells May Be Caused By Chronic Exposure To Virus." ScienceDaily. ScienceDaily, 6 May 2008. <www.sciencedaily.com/releases/2008/05/080505211809.htm>.
Massachusetts General Hospital. (2008, May 6). Exhaustion Of HIV-specific T Cells May Be Caused By Chronic Exposure To Virus. ScienceDaily. Retrieved April 17, 2014 from www.sciencedaily.com/releases/2008/05/080505211809.htm
Massachusetts General Hospital. "Exhaustion Of HIV-specific T Cells May Be Caused By Chronic Exposure To Virus." ScienceDaily. www.sciencedaily.com/releases/2008/05/080505211809.htm (accessed April 17, 2014).

Share This



More Health & Medicine News

Thursday, April 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Could Even Casual Marijuana Use Alter Your Brain?

Could Even Casual Marijuana Use Alter Your Brain?

Newsy (Apr. 16, 2014) A new study conducted by researchers at Northwestern and Harvard suggests even casual marijuana use can alter your brain. Video provided by Newsy
Powered by NewsLook.com
Thousands Of Vials Of SARS Virus Go Missing

Thousands Of Vials Of SARS Virus Go Missing

Newsy (Apr. 16, 2014) A research institute in Paris somehow misplaced more than 2,000 vials of the deadly SARS virus. Video provided by Newsy
Powered by NewsLook.com
Formerly Conjoined Twins Released From Dallas Hospital

Formerly Conjoined Twins Released From Dallas Hospital

Newsy (Apr. 16, 2014) Conjoined twins Emmett and Owen Ezell were separated by doctors in August. Now, nearly nine months later, they're being released from the hospital. Video provided by Newsy
Powered by NewsLook.com
Ebola Outbreak Now Linked To 121 Deaths

Ebola Outbreak Now Linked To 121 Deaths

Newsy (Apr. 15, 2014) The ebola virus outbreak in West Africa is now linked to 121 deaths. Health officials fear the virus will continue to spread in urban areas. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins