Latent tuberculosis: mechanisms of host and bacillus that contribute to persistent infection

• Published in: The Lancet infectious diseases Vol. 3; no. 9; pp. 578 - 590
• Main Authors: Tufariello, JoAnn M, Chan, John, Flynn, JoAnne L
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.09.2003; Elsevier Limited
• Subjects: Activation; Animals; Antigens; Bacteria; Chemokines; Cytokines; Dendritic cells; Disease Models, Animal; Gangrene; Genes, MHC Class II - genetics; HIV; Human immunodeficiency virus; Humans; Immune response; Immune system; Infections; Infectious diseases; Latent infection; Lungs; Lymphocytes; Mycobacterium tuberculosis; Mycobacterium tuberculosis - genetics; Mycobacterium tuberculosis - immunology; Persistent infection; Reactive Nitrogen Species - adverse effects; Reactive Nitrogen Species - immunology; Skin tests; Tuberculin; Tuberculosis; Tuberculosis - immunology; Tuberculosis - prevention & control; Tumor necrosis factor-TNF
• ISSN: 1473-3099; 1474-4457
• DOI: 10.1016/S1473-3099(03)00741-2

Most people infected with Mycobacterium tuberculosis contain the initial infection and develop latent tuberculosis. This state is characterised by evidence of an immune response against the bacterium (a positive tuberculin skin test) but no signs of active infection. It can be maintained for the lifetime of the infected person. However, reactivation of latent infection occurs in about 10% of infected individuals, leading to active and contagious tuberculosis. An estimated 2 billion people worldwide are infected with M tuberculosis-an enormous reservoir of potential tuberculosis cases. The establishment and reactivation of latent infection depend on several factors, related to both host and bacterium. Elucidation of the host immune mechanisms that control the initial infection and prevent reactivation has begun. The bacillus is well adapted to the human host and has a range of evasion mechanisms that contribute to its ability to avoid elimination by the immune system and establish a persistent infection. We discuss here current understanding of both host and bacterial factors that contribute to latent and reactivation tuberculosis.