Tuberculosis and cigarette smoke exposure: An update of in vitro and in vivo studies.

Tuberculosis (TB) has been declared the first cause of death by an infectious agent. Annually, 10.4 million people suffer active TB. Most infected individuals live in low-income countries, where social and economic conditions enhance the dissemination and progression of the disease. These countries have a high percentage of smokers. Thousands of studies have linked cigarette smoke (CS) with increased risk of many diseases, such as cancer and lung diseases. Numerous in vitro studies have been conducted to evaluate the general and specific toxic effects of CS in lung immune function. Smoke exposure increases the risk of TB development three-fold. However, until now, only few animal studies have been performed to analyze the association between smoke and TB. In the present work, we review in vitro and in vivo studies whose aim was to analyze the molecular basis of TB susceptibility caused by exposure to CS.

Induction of ß-defensins by l-isoleucine as novel immunotherapy in experimental murine tuberculosis.

Tuberculosis is a worldwide health problem, and multidrug-resistant (MDR) and extensively multidrug-resistant (XMDR) strains are rapidly emerging and threatening the control of this disease. These problems motivate the search for new treatment strategies. One potential strategy is immunotherapy using cationic anti-microbial peptides. The capacity of l-isoleucine to induce beta-defensin expression and its potential therapeutic efficiency were studied in a mouse model of progressive pulmonary tuberculosis. BALB/c mice were infected with Mycobacterium tuberculosis strain H37Rv or with a MDR clinical isolate by the intratracheal route. After 60 days of infection, when disease was in its progressive phase, mice were treated with 250 µg of intratracheal l-isoleucine every 48 h. Bacillary loads were determined by colony-forming units, protein and cytokine gene expression were determined by immunohistochemistry and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), respectively, and tissue damage was quantified by automated morphometry. Administration of l-isoleucine induced a significant increase of beta-defensins 3 and 4 which was associated with decreased bacillary loads and tissue damage. This was seen in animals infected with the antibiotic-sensitive strain H37Rv and with the MDR clinical isolate. Thus, induction of beta-defensins might be a potential therapy that can aid in the control of this significant infectious disease.

IFN-α Boosting of Mycobacterium bovis Bacillus Calmette Güerin-Vaccine Promoted Th1 Type Cellular Response and Protection against M. tuberculosis Infection.

The role of type I IFNs in the pathogenesis and control of mycobacterial infection is still controversial. It has been reported that type I IFNs exacerbated M. tuberculosis infection through hampering Th1 type cellular immune response. However, under certain conditions they can act as natural immune adjuvants for commercial vaccines. At this point, we have reported recently that successive IFN-alpha boosting of Mycobacterium bovis Bacillus Calmette Güerin (BCG) vaccinated mice protected adult mice from intradermal M. lepraemurium infection and a difference in iNOS was observed. In the present work, we have found that intramuscular IFN-α boosting of Mycobacterium bovis Bacillus Calmette Güerin (BCG) vaccine, either in vitro (human cell line or macrophages derived from PBMC) or in vivo (aerosol mouse model of MTb infection), promoted mostly the development of specific anti-antimycobacterial Th1 type cytokines (IFN-γ; IL-12, TNF-alpha, and IL-17; IL1ß) while bacterial load reduction (0.9 logs versus PBS or BCG vaccine) was observed. These findings indicate that, under the experimental settings reported here, interferon alpha can drive or affect the TH cellular immune response in favour of BCG-inducing immunity against M. tuberculosis infection.