Featured Research

from universities, journals, and other organizations

How immune cells defend themselves against HIV

Date:
October 1, 2012
Source:
Heidelberg University Hospital
Summary:
Scientists have decoded a mechanism used by the human immune system to protect itself from HIV viruses. The results provide new insights into the molecular background of AIDS and could open up starting points for new treatments.

A team of scientists led by virologists Prof. Oliver T. Fackler and Prof. Oliver T. Keppler from Heidelberg University Hospital have decoded a mechanism used by the human immune system to protect itself from HIV viruses. A protein stops the replication of the virus in resting immune cells, referred to as T helper cells, by preventing the transcription of the viral genome into one that can be read by the cell. The ground-breaking results provide new insights into the molecular background of the immunodeficiency syndrome AIDS and could open up starting points for new treatments.

The study has now been published -- ahead of print online -- in the international journal Nature Medicine.

Human immunodeficiency viruses attack different cells of the human immune system, most frequently, "T helper cells." These lymphocytes play a key role in immune defense, since they activate other immune cells upon contact with pathogens and set off subsequent immune responses. In the course of the HIV infection, they are continuously depleted until the immune system ultimately fails, culminating in AIDS with various infections.

In healthy people, the vast majority of T helper cells in the blood are in a resting state. They are not activated until they contact the pathogens against which they are specialized in defending. In the activated state, the cells are susceptible to HIV infection. "In contrast, resting T helper cells are immune to HIV: While the virus docks, and delivers its genetic information to the cell, the infection does not progress further. We have investigated why this is the case," explained Prof. Fackler, head of the working group at the Department of Infectious Diseases, Virology. Even if the T helper cells are activated later on, the virus does not replicate, because the genetic information of the virus is degraded during this period.

HIV genome cannot be transcribed into cell-compatible version

The team is headed by Prof. Fackler and Prof. Keppler, who moved from Heidelberg to the University Hospital in Frankfurt in April 2012 and now heads the Institute of Medical Virology there. The researchers discovered that the cellular protein SAMHD1 significantly contributes to protecting the resting immune cells. The protein is present in both resting and activated T helper cells and depletes nucleotides, the building blocks of genetic information. In the active phase the cells double their genetic information and divide, a process that depends on the continoues production of nucleotides. In the resting state, the cell does not require any nucleotides and stops their production, and SAMHD1 degrades the remaining nucleotides. "As a result, the HIV viruses most likely also lack the material they need to transcribe their genetic information into a version that can be used for the cell and to allow it to replicate," Fackler explained.

In the experiment, if SAMHD1 expression was silenced, resting T helper cells became susceptible to HIV infection. The same was true for immune cells of a patient who is unable to produce SAMHD1 due to a hereditary condition. "This shows that HIV can only replicate in lymphocytes if the effect of the protective protein SAMHD1 is eliminated," Keppler said. In addition, the researchers discovered that this early protective measure must be followed by other barriers to HIV replication. Even without SAMHD1, no new viruses were released from resting T helper cells. Now that they have described the protective function of SAMHD1 and are able block it, the scientists can for the first time also investigate the downstream mechanisms. "We hope that we will be able to use these findings to develop new strategies in the fight against HIV," the virologist said.


Story Source:

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


Journal Reference:

  1. Hanna-Mari Baldauf, Xiaoyu Pan, Elina Erikson, Sarah Schmidt, Waaqo Daddacha, Manja Burggraf, Kristina Schenkova, Ina Ambiel, Guido Wabnitz, Thomas Gramberg, Sylvia Panitz, Egbert Flory, Nathaniel R Landau, Serkan Sertel, Frank Rutsch, Felix Lasitschka, Baek Kim, Renate König, Oliver T Fackler, Oliver T Keppler. SAMHD1 restricts HIV-1 infection in resting CD4 T cells. Nature Medicine, 2012; DOI: 10.1038/nm.2964

Cite This Page:

Heidelberg University Hospital. "How immune cells defend themselves against HIV." ScienceDaily. ScienceDaily, 1 October 2012. <www.sciencedaily.com/releases/2012/10/121001095905.htm>.
Heidelberg University Hospital. (2012, October 1). How immune cells defend themselves against HIV. ScienceDaily. Retrieved September 1, 2014 from www.sciencedaily.com/releases/2012/10/121001095905.htm
Heidelberg University Hospital. "How immune cells defend themselves against HIV." ScienceDaily. www.sciencedaily.com/releases/2012/10/121001095905.htm (accessed September 1, 2014).

Share This




More Health & Medicine News

Monday, September 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Get on Your Bike! London Cycling Popularity Soars Despite Danger

Get on Your Bike! London Cycling Popularity Soars Despite Danger

AFP (Sep. 1, 2014) — Wedged between buses, lorries and cars, cycling in London isn't for the faint hearted. Nevertheless the number of people choosing to bike in the British capital has doubled over the past 15 years. Duration: 02:27 Video provided by AFP
Powered by NewsLook.com
We've Got Mites Living In Our Faces And So Do You

We've Got Mites Living In Our Faces And So Do You

Newsy (Aug. 30, 2014) — A new study suggests 100 percent of adult humans (those over 18 years of age) have Demodex mites living in their faces. Video provided by Newsy
Powered by NewsLook.com
Liberia Continues Fight Against Ebola

Liberia Continues Fight Against Ebola

AFP (Aug. 30, 2014) — Authorities in Liberia try to stem the spread of the Ebola epidemic by raising awareness and setting up sanitation units for people to wash their hands. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
California Passes 'yes-Means-Yes' Campus Sexual Assault Bill

California Passes 'yes-Means-Yes' Campus Sexual Assault Bill

Reuters - US Online Video (Aug. 30, 2014) — California lawmakers pass a bill requiring universities to adopt "affirmative consent" language in their definitions of consensual sex, part of a nationwide drive to curb sexual assault on campuses. Linda So reports. Video provided by Reuters
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