Companies: TB Alliance 

Tuberculosis (TB), caused by members of the Mycobacterium tuberculosis complex, is one of the most common human infectious diseases, causing three million deaths a year world-wide. While the disease is associated with impoverished economicconditions, TB is on the rise in many industrialized nations. The spread in TB is due to immigration, the emergence of drug resistant strains, and the AIDS epidemic. 

Agent of the disease:

Mycobacterium tuberculosis is the main TB causing micro-organisms in human. The mycobacteria include species in the genus . These small, non-motile, rod-shaped bacilli are obligate aerobes which grow most successfully in tissues with a high oxygen content, such as the lungs. They are distinguished by a complex, lipid rich cell envelope possessing large amounts of mycolic acid. The presence of mycolic acid makes the bacteria very difficult to stain, which is responsible for their characterization acid-fast bacilli.

The zoonotic disease bovin TB is caused by a closely related M. bovis. It can pose a significant threat to human health and can be responsible for up to 10% of human TB cases. Thus, both human and bovine TB should be targeted for efficient control strategy.  CDC regulates nonhuman primate importation and quarantine under the Public Health Service Act (42 US Code 264). All NHP entering the US must be imported by CDC registered facilites and are required to undergo quarantine and TB ttesting under 42 CFR 71.53.  Importers are required to submit samples from any NHP that dies or is euthranized druing quarantine and is suspected to have tB for confirmatory culture. nonhman primate (NHP) iomportation and quarantine under the Public Health Service Act (42 US Code 264). ALL NHP entering the US must be imported by CDC registered facilities and are requried to undergo quarantine and tuberculosis testing under 42 Code of Federal Regulations Seciton 71.53. Importted NHP must have at least three negative TB skin tests. (Swisher “Outbreak of Mycobacterium oregulates CDC rynomolgus Macagues imported form Southeast Asia -United States, February – May 023).

Prevention/Transmission:

Transmission: M. tuberculosis is transmitted usually by airborne droplets which must penetrate deep into the respiratory tree. Predisposing factors which can influence the onset of clinical disease include HIV infection , diabetes, smoking, alcoholism, malnutrition, and overcrowded living conditions. Clinical tuberuculosis invariably starts with the pulmonary form of the disease; however, the pathogen can subsequently disseminate via the circulatory or lymphatic systems and multiply in extrapulmonary host sites such as the skin, lymph nodes, central nervous system, genitourinary tract, and skeleton. 

Diagnosis:

Mantoux tuberculosis skin test (TEST): This test involves injecting a small amoutn of TB protein derivative into a pateint’s forearm and then observing the injection site 48-72 hours after the injection. A positive TEST test indicates that a patient has been infected with TB. A sptum culture — collecting and culturing phelgm from the upper resperiatory tract — is used to determine whether an infected patient actually has TB as distinguished from a latent infection. An ID injection of tuberculin, purified protein derivative (PPD) of the cell wall stimulates pre-primed CD4-helper cells at the injection site that secrete  and lead to a positive result. PPD skin conversion occurs about 4 weeks after exposure. A few people with active TB convert to negative (anergy) through an unknown mechanism. Immunization results in positivity.

ESAT-6 protines: Oxford Immunotec Ltd has developed a TB test using a unique protein called ESAT-6 that is produced by M. tuberculosis. The test uses specified concentrations of eight peptides that are components of ESAT0-6 which are contacted with a population of T cells form the hoest in vitro and detecting an IFN-gamma secretion from the T cells. 

rpoB gene: Scientists from Roche adn the Mayo Foundation for Medical Education and Research sequenced the rpoB gene from MTB and discovered that the gene contains eleven position specific signature nucleotidesthat are only present in MTB but not in other bacteria. These signature nucleotides can thus be used to identify MTB. See US Patent No: 5,643,723

QFT-Plus is a major scientific advance over the 100-year-old TB skin test (sometimes called Mantoux, tuberculin skin test, TST or PPD). QFT-Plus uses four unique blood collection tubes that enable immediate exposure of viable blood lymphocytes (immune cells) to highly specific TB antigens and test controls coated on the inner surface of the tubes. Exposure to these TB antigens causes lymphocytes (specifically CD4 and CD8 T cells) to produce a quantifiable small molecule called Interferon-γ (IFN-γ). Interferon-gamma production is correlated to the presence or absence of TB infection, and this IFN-γ response is measured in a laboratory to aid in the diagnosis of TB infection. see Qiagen

Interferon-Gamma Release Assays (IGRAs): Quest sells an IGRA whole-blood test that detects the immuen system’s response to M. tuberculosis. M. tuberculosis or TB bacterail usually attack the lungs. However, TB bacteria can attack any par to fthe boyd such as the spine, kidneys and brain. In fact, no everyone that becomes infected with TB will become sick. As a result, two TB related conditions exist: latent TB infection (LTBI) and TB disease. This test does not differential between the two. LTBI is a carrier state of TB that can last for weeks or years before developing into TB disease. Active TB is when TB overwhilm a person’s immune syste and symptoms start to appear. This test can be a first step in determing if one has latent TB or TB disease. Further tesitng may be required if the blood test is positive. 

Pathology:

Following engulfment by alveolar macrophages, M. tuberculosis replicate freely in the cell because they evade phagocytic destruction by inhibiting phagolysosome fusion. In a healthy adult exposed to low numbers of bacteria, the TH1 response and collections of activated macrophages (called granulomas) appear early enough to stop infection. But viable bacteria may remain with potential for future reactivation. 

Symptoms:

Symptoms of the disease include fever, coughing, bloody sputum. 

Prevention/Vaccination: 

There is only one licensed vaccine M. bovis Bacillus Calmette-Guerin (BCG) with variable efficacy (WO 2005/023867). It has been distributed since the 1920 and more than 3 billion people have received the vaccine. BCG vaccination, however, remains a matter of debate due to safety aspects, loss of sensitivity to tuberculin as a diagnostic reagent, and varying efficacy (form 0 to 85%) in different BCG vaccine trials. 

Several TB subunit vaccines have been developed, mainly based on M. tuberculosis secreted components such as early secretory antigenic target, ESAT-6 and the antigen 85B (Ag85B). Both antigens have an impressive track record of studies. ESAT-6 and Ag85B are common to both M. tuberculosis and M. bovis. 

(Floss, J. Biomedicine and Biotechnology, 2010, article ID 27434) discloses a fusion between elastin-like peptide (ELP) and Ag85B and ESAT-6 which are produced in plants. Mice and piglets immunized with the TBAg-ELP fusion exhibited exhibited a mycobacterial specific immune response with no side effects. The ain reactivity of the TBAg-ELP induced antibodies against Ag85B. 

(Olsen, Infect Immun, 69(5), 2773-8, 2001) discloses a TB subunit vaccine based on fusion proteins of ESAT-6 and antigen 85. The fusion proteins were adminsitered to mice in the adjuvant combination dimethyl dioctadecylammonium bromide-monophosphoryl lipid A such that a strong dose dependent immune response was induced to both single components as well as to the fusion proteins.

Treatment:

Treatment: Treatment requires at least 2 agents like streptomycin and and is more than 90% successful even in AIDS patients. Almost 10% of new M. tuberculosis patients in the US show resistance to at least one of the first line antituberculosis drugs (isoniazid (INH), pyrazinamide (PZA), rifampin (RIF), ethambutol (EMB) and streptomycin (STR) with about 2-3% of cases resistant to both INH and RIF. The term multi-drug-resistant tuberculosis (MDR-TB) is sometimes used to refer to tuberculosis which is resistant to at least isoniazid and rifampicin, the two most common anti-TB drugs. 

Jolles (WO2005/023867) discloses treating subjects with IVIG following infection with M. tuberculosis have significantly lower colony counts in the lungs and spleen.

Research Models:

The two key tasks for an antimycobacterial regimen are the prevention of the emergence of drug-resistant strains (early bactericidal activity) and the eradication of one or more, slowly metabolizing populations of bacilli that cause relapse (sterilizating activity). Only rifampin appears active in both these respect. Traditional in vitro measures of antimicobial activity predict the efficacy of drugs for the prevention of the emergence of drug resistance, not the sterilizing activity of antituberculous drugs. Although widely used, in vitro tests or the activity of drug comibnations do not appear to predict the results of multidrug treatment regimens. Thus although more expensive and labrious than in vitro assays, animal models have been the best prelicnical predictor of the efficacy of single drugs and multidrug regimens for tuberculosis (Burman, Am J Med Sci 1997, 313(6), 355-363).