Cellular Safety Shelters Allow TB Agent To Survive In Infected Individuals

Main Category: Tuberculosis
Also Included In: Infectious Diseases / Bacteria / Viruses;  Respiratory / Asthma
Article Date: 14 Nov 2008 - 1:00 PDT

email to a friend   printer friendly   view / write opinions   rate article

"Foamy" macrophage formation may be the key to persistence of infection by Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, explains a study published November 14 in the open-access journal PLoS Pathogens. These immunity-related cells are shown to be a safety reservoir where the bacterium can hide for years in infected individuals, before inducing an active disease. According to the research group led by Frederic Altare, the tubercle bacillus circumvents the host immune response by inducing the transformation of aggressive immune cells into a non-aggressive refuge where it is able to survive and have access to large sources of nutrients.

Mtb is responsible for a dramatic global health problem. The World Health Organization has estimated that this pathogen infects one third of the human population and causes three million deaths annually. Most individuals remain asymptomatic for several years before developing an active disease. In such individuals, it is generally admitted that the bacilli are not cleared but rather persist in a dormant state. One of the main goals of TB research is to understand how and where the bacilli survive within infected hosts.

Using a recently developed in vitro assay mimicking the human host immune response, the researchers observed that Mtb uses some of its cell surface constituents to induce the transformation of macrophages (which are supposed to internalize and kill infecting bacteria), into "foamy" cells. These cells have lost their killing ability and have accumulated large amounts of lipids, the main nutrient for internalized Mtb. They further observed that Mtb remained alive within these cells, and switched into a dormant state.

This observation may direct novel research towards the elucidation of tubercle bacillus survival mechanisms. This study also helps explain the role of a previously uncharacterized cell population participating in the human response to Mtb. "Foamy" macrophages may prove to be a useful tool for the development of new antimicrobial drugs targeted to kill the bug directly within its natural shelter.

Constitute a Nutrient-Rich Reservoir for M. tuberculosis Persistence.
Peyron P, Vaubourgeix J, Poquet Y, Levillain F, Botanch C, et al. (2008) Foamy Macrophages from Tuberculous Patients' Granulomas
PLoS Pathog 4(11): e1000204. doi:10.1371/journal.ppat.1000204

Disclaimer

This press release refers to an upcoming article in PLoS Pathogens. The release is provided by the article authors. Any opinions expressed in thesereleases or articles are the personal views of the journal staff and/or article contributors, and do not necessarily represent the views or policies of PLoS. PLoS expressly disclaims any and all warranties and liability in connection with the information found in the releases and articles and your use of such information.

About PLoS Pathogens

PLoS Pathogens publishes outstanding original articles that significantly advance the understanding of pathogens and how they interact with their host organisms. All works published in PLoS Pathogens are open access. Everything is immediately available subject only to the condition that the original authorship and source are properly attributed. Copyright is retained by the authors. The Public Library of Science uses the Creative Commons Attribution License.

PLoS Pathogens

About the Public Library of Science

The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource.

Public Library of Science