Summary:

This project aims to study the relation between the cell cycle and dormancy development in Mycobacterium tuberculosis (Mtb), with the final aim being to increase the knowledge on dormancy development and to identify potential candidates for the development of antitubercular drugs specifically active in dormant bacilli. Mtb is a facultative intracellular pathogen able to infect the human lung for decades without showing any symptom. Following immunity suppression caused by age, diseases or malnutrition, tubercle bacilli can reactivate as an overt disease.

About one third of the human population is estimated to be affected by latent tuberculosis representing a huge reservoir for the infection. The lack of drugs efficiently active on dormant bacteria is a major problem in fighting this important disease. Conditional mutants unable to express important cell cycle regulators will be constructed and used to study their role in: global regulation of gene expression; cytolocalisation of cell cycle proteins, and; latency development in vitro and in vivo.

Additionally, a transposon insertion library will be used to identify new mycobacterial genes essential for survival to prolonged stationary phase and their expression will be measured during progressive and latent infection.

Background:

Upon Mtb arrival in the alveoli by inhalation of aerosol particles, it is engulfed by alveolar macrophages. These cells are unable to kill Mtb, which replicate in their phagosomes. Depending on the quality and intensity of the immune response, Mtb will cause a primary acute infection or will be walled off in granulome where it will be able to survive in latency for decades without showing any symptom. In some individuals as the immune system becomes weaker due to the age or to diseases such as AIDS, Mtb can reactivate, escape from the granulome and cause a secondary acute infection. About one third of the world population is believed to affected by latent tuberculosis.

Active tuberculosis is a treatable infection. The main anti-tuberculosis drugs are isoniazid, rifampicin, pyrazinamide, and ethambutol. Most antitubercular drugs target cell wall or RNA synthesis and are thus more active against actively growing bacteria. However, during latent tuberculosis, proliferation appears to be markedly reduced or absent, so that latent bacilli are less amenable to killing and very hard to eradicate. Although some clinical trials have demonstrated that treatment of latent tuberculosis reduces the presence of Mtb, the risk of reactivation is not completely eliminated.

To successfully treat patients affected by latent tuberculosis new drugs are needed active against latent bacteria. These drugs should target bacterial structures expressed during latency and essential for latency maintenance and/or for reactivation. Alternatively, a different class of new drugs can be used in order to interfere with the regulation of Mtb gene expression during latency, forcing it to reactivate. Once bacteria are reactivated, they can be efficiently removed by isoniazid or rifampicin.

Aim:

The aim of this project is to increase the knowledge on dormancy development in Mycobacterium tuberculosis with particular focus on cell-cycle related proteins and to identify potential candidates for the development of antitubercular drugs specifically active against dormant bacilli.

Expected results:

Better characterisation of the physiology of dormancy and its relation to cellcycle proteins. Identification of new genes involved in dormancy development.

Potential applications:

The identified genes will be excellent potential candidates for the development of new antitubercular drugs.

Coordinator:

Partners:

Nº	Principal Scientific Participants	Official Address	Other Information
2	Jean-Marc Reyrat	Inserm U570 Université Descartes Paris V Site Necker 156 rue de Vaugirard 75730 PARIS cedex 15 France	E-mail: jmreyrat@necker.fr
3	Leiria Salazar	IVIC Km 11 Carretera Panamericana Altos de Pipe Estdo Miranda, Venezuela or: PO Box: Apartado 21827 Caracas 1020A, Venezuela	Tel: +58 212 5041715 Fax: +58 212 5041444 E-mail: lsalazar@ivic.ve
4	Miguel Vicente	Centro Nacional de Biotecnología C/ Darwin 3 CSIC Campus de Cantoblanco E-28049 Madrid Spain	Tel: +34 91 585 46 9 Fax: +34 91 585 45 06 E-mail: mvicente@cnb.uam.es Institutional Website: www.cnb.uam.es/Group Website: www.cnb.uam.es/~mvicente/
5	Rogelio Hernandez Pando	Experimental Pathology Section Department of Pathology National Institute of Medical Sciences and Nutrition "Salvador Zubiran" Street- Vasco de Quiroga, no-12, CP-14000, Tlalpan Mexico city, Mexico	Tel: +52 55 54 85 34 91 Fax:+52 55 56 55 10 76 E-mail: rhdezpando@hotmail.com