Latent tuberculosis
Encyclopedia
Also called latent tuberculosis infection, latent TB or LTBI.
Latent tuberculosis
is where a patient is infected with Mycobacterium tuberculosis
, but does not have active tuberculosis disease. Patients with latent tuberculosis are not infectious, and it is not possible to get TB from someone with latent tuberculosis. The main risk is that approximately 10% (5% in the first two years after infection and 0.1% per year thereafter but higher risk if immunosuppressed) of these patients will go on to develop active tuberculosis at a later stage of their life. This is particularly true if there is development of a disease affecting the immune system
(such as AIDS) or a disease whose treatment affects the immune system (such as chemotherapy
in cancer or systemic steroids in asthma or Enbrel, Humira or Orencia in rheumatoid arthritis) or in cirucumstances resulting in malnutrition (such as illness or injury affecting the digestive system, or prolonged period of not eating, or disturbance in availability such as famine, residence in refugee camp or concentration camp, or civil war. Another factor is that "old age" affects the immune system. The identification and treatment of people with latent TB is an important part of controlling this disease.
The tuberculin skin tests in use include (but are not limited to)
There are currently three γ-interferon (interferon gamma release assay - IGRA) tests available.
A description of the tests and their interpretation is given below.
The Mantoux test is now standardised by the WHO. 0.1 ml of tuberculin (100 units/ml) is given by intradermal injection into the volar
surface of the forearm (subcutaneous injection results in false negative results). A waterproof ink mark is drawn around the injection site so as to avoid difficulty finding it later if the level of reaction is small. The test is read two to seven days afterwards. The area of induration (NOT erythema
) is measured transverse
ly across the forearm (left to right, not up and down) and recorded to the nearest millimetre.
The Heaf test was first described in 1951 . The test uses a Heaf gun with disposable single-use heads; each head has six needles arranged in a circle. There are standard heads and pediatric heads: the standard head is used on all patients aged 2 years and older; the pediatric head is for infants under the age of 2. For the standard head, the needles protrude 2 mm when the gun is actuated; for the pediatric heads, the needles protrude 1 mm. Skin is cleaned with alcohol, then tuberculin (100,000 units/ml) is evenly smeared on the skin (about 0.1 ml); the gun is then applied to the skin and fired. The excess solution is then wiped off and a waterproof ink mark is drawn around the injection site. The test is read 2 to 7 days later.
It is not easy to translate between Heaf and Mantoux, but
The tuberculin used for Heaf tests is 1000 times more concentrated than that used for Mantoux tests. In countries where both tests are used, use of the correct concentration avoids false positive and false negative results.
(BCG), an attenuated strain of Mycobacterium bovis
that is used in some countries as a vaccine against tuberculosis are given repeated tuberculin skin tests. In these people, the first test revives or primes the immune response so that on repeat testing, the response is much stronger and the patient then looks as if he now has a positive reaction. The second tuberculin skin test result is the correct one.
The UK and U.S. guidelines approach the phenomenon of boosting differently. Under U.S. guidelines, which say to ignore previous immunisation with BCG, a person showing the phenomenon of boosting will be falsely described as a tuberculin converter. On the other hand, UK guidelines advise two tuberculin skin tests one week apart if boosting is suspected, taking the result of the second test as being the true result.
Boosting can occur up to two years after the first Mantoux test.
The UK guidelines are formulated according to the Heaf test: In patients who have had BCG previously, latent TB is diagnosed if the Heaf test is grade 3 or 4 and have no signs or symptoms of active TB; if the Heaf test is grade 0 or 1, then the test is repeated and. In patients who have not had BCG previously, latent TB is the Heaf test if grade 2, 3 or 4, and have no signs or symptoms of active TB. Repeat Heaf testing is not done in patients who have had BCG (because of the phenomenon of boosting). For details of tuberculin skin test interpretation, please refer to the BTS guidelines (references given below).
Given that the US recommendation is that prior BCG vaccination be ignored in the interpretation of tuberculin skin tests, false positives are possible as a result of: (1) people who have previously had BCG (even many years ago) may still have a false positive Mantoux test, and (2) serial testing with tuberculin skin tests boosts the immunological response in those people who have previously had BCG, so these people will falsely appear to be tuberculin converters. This may lead to treating more people than necessary, with the possible risk of those patients suffering adverse drug reactions. However, as Bacille Calmette-Guérin vaccine is not 100% effective, and is less protective in adults than pediatric patients, not treating these patients could lead to a possible infection. The current US policy seems to a reflect a desire to err on the side of safety (of the general public).
The U.S. guidelines also allow for tuberculin skin testing in immunosuppressed patients (those with HIV
, or who are on immunosuppressive drugs), whereas the UK guidelines recommend that tuberculin skin tests should not be used for such patients because it is unreliable.
There are currently (26 March 2009) three commercially available interferon-γ release assays (IGRAs): QuantiFERON-TB Gold, QuantiFERON-TB Gold In-Tube and T-SPOT.TB
. These tests are not affected by prior BCG vaccination, and look for the body's response to specific TB antigens not present in other forms of mycobacteria and BCG (ESAT-6
). Whilst these tests are new they are now becoming available globally.
CDC:
HPA Interim Guidance:
, and this regimen is still widely used in the U.S. (but not elsewhere).
There are several treatment regimens currently in use:
and PAS has been used before. It would appear sensible to choose a combination of antibiotics based on the known sensitivities of the organism. The CDC
have recommended a combination of pyrazinamide
and ethambutol
, with either pyrazinamide
or fluoroquinolone. Immunocompetent contacts should be treated for 6 months; immunocompromised contacts should be treated for 12 months.
(WHO) approximately 36 million people will die of tuberculosis by 2020 if it is not controlled. They add that eight million people develop active tuberculosis every year. Approximately 98 percent of those victims are from developing countries. Furthermore, WHO estimates that approximately one-third of the world's population are carriers of latent tuberculosis.
Therefore, the scientific community continues its research efforts to learn more from this disease in order to develop more options for possible treatments.
The factors that trigger latent tuberculosis infection to progress into active disease have been unknown. However, Professor David Russell and his group at Cornell University in New York
, USA, recently demonstrated that the bacteria responsible for causing TB are able to hijack fat metabolism
in the host to drive the progression of the disease.
The research made clear that the Mycrobacterium tuberculosis is able to stimulate the immune cells they infect resulting in the accumulation of fat droplets. These droplets turn into what they called “foamy” cells and such transformation can trigger a reawakening of the TB infection from its latent state.
Professor Russell believes that more knowledge about the bacterium's life cycle and its host interactions will open possibilities to develop new treatments.
Another group of researchers at Sydney's Centenary Institute made an important discovery that could lead to the development of a new drug for TB. The team, led by Dr Nick West, investigated a protein
that is essential for TB to survive and later they reported some success in developing a drug that would inhibit this protein. If the group is successful in finding a way to treat latent tuberculosis, millions of people around the world could be saved.
Furthermore, researchers from the Genome Institute of Singapore together with collaborators in The Netherlands, Indonesia
, United Kingdom
, and the Russian Federation, identified a new gene
that would provide susceptibility to pulmonary tuberculosis. The gene is named Toll-like receptor 8 (TLR8) and it recognizes some factors from viruses such as HIV
. This gene is believed to also have a role in human susceptibility to Mycobacterium tuberculosis infections. This discovery could open new options for therapeutic interventions.
Latent tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
is where a patient is infected with Mycobacterium tuberculosis
Mycobacterium tuberculosis
Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...
, but does not have active tuberculosis disease. Patients with latent tuberculosis are not infectious, and it is not possible to get TB from someone with latent tuberculosis. The main risk is that approximately 10% (5% in the first two years after infection and 0.1% per year thereafter but higher risk if immunosuppressed) of these patients will go on to develop active tuberculosis at a later stage of their life. This is particularly true if there is development of a disease affecting the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
(such as AIDS) or a disease whose treatment affects the immune system (such as chemotherapy
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
in cancer or systemic steroids in asthma or Enbrel, Humira or Orencia in rheumatoid arthritis) or in cirucumstances resulting in malnutrition (such as illness or injury affecting the digestive system, or prolonged period of not eating, or disturbance in availability such as famine, residence in refugee camp or concentration camp, or civil war. Another factor is that "old age" affects the immune system. The identification and treatment of people with latent TB is an important part of controlling this disease.
Tests for latent tuberculosis
There are currently two major classes of tests used to identify patients with latent tuberculosis: tuberculin skin tests and γ-interferon tests.The tuberculin skin tests in use include (but are not limited to)
- Mantoux testMantoux testThe Mantoux test is a diagnostic tool for tuberculosis. It is one of the two major tuberculin skin tests used in the world, largely replacing multiple-puncture tests such as the Tine test...
- Heaf testHeaf testThe Heaf test is a diagnostic skin test performed in order to determine whether or not a child has been exposed to tuberculosis. Also known as the Sterneedle test, it is administered by a Heaf gun which is a spring-loaded instrument with six needles arranged in a circular formation.Patients who...
- Tine testTine testThe Tine test is a multiple puncture tuberculin skin test used to aid in the medical diagnosis of tuberculosis .This test uses a small "button" that has four to six short needles coated with TB antigens...
(often misspelled as tyne)
There are currently three γ-interferon (interferon gamma release assay - IGRA) tests available.
- T-SPOT.TBT-SPOT.TBT-SPOT.TB is a type of ELISPOT assay used for tuberculosis diagnosis. It is available in most European countries, the United States as well as various other territories. It was developed by researchers at the University of Oxford in England. It counts the number of effector T cells, white blood...
- QuantiFERON-TB Gold
- QuantiFERON-TB Gold In-Tube
A description of the tests and their interpretation is given below.
Tuberculin skin testing
The tuberculin skin test has its origins in the late 19th century. Crudely speaking, tuberculin (also called purified protein derivative or PPD) is a standardised killed extract of cultured TB, injected into the skin to measure the reaction that person's immune response to TB. There are three methods of testing, the Mantoux test, the Heaf test and the Tine test. The Heaf test was preferred in the UK because it requires less training to administer and because there is less interobserver variation in its interpretation. The Heaf test was stopped in 2005 because the manufacturer did not find it financially sustainable to continue manufacturing the test.Mantoux test
- See: Mantoux testMantoux testThe Mantoux test is a diagnostic tool for tuberculosis. It is one of the two major tuberculin skin tests used in the world, largely replacing multiple-puncture tests such as the Tine test...
The Mantoux test is now standardised by the WHO. 0.1 ml of tuberculin (100 units/ml) is given by intradermal injection into the volar
Volar
Volar may refer to:*Volar, Afghanistan*Flight*Volar Airlines*Anatomical terms of location#Relative_directions_in_the_limbs**Volar arches**Volar branch of ulnar nerve**Volar radioulnar ligament**Volar carpal branch...
surface of the forearm (subcutaneous injection results in false negative results). A waterproof ink mark is drawn around the injection site so as to avoid difficulty finding it later if the level of reaction is small. The test is read two to seven days afterwards. The area of induration (NOT erythema
Erythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
) is measured transverse
Transverse plane
The transverse plane is an imaginary plane that divides the body into superior and inferior parts. It is perpendicular to the coronal and sagittal planes....
ly across the forearm (left to right, not up and down) and recorded to the nearest millimetre.
Heaf test
- See:Heaf testHeaf testThe Heaf test is a diagnostic skin test performed in order to determine whether or not a child has been exposed to tuberculosis. Also known as the Sterneedle test, it is administered by a Heaf gun which is a spring-loaded instrument with six needles arranged in a circular formation.Patients who...
The Heaf test was first described in 1951 . The test uses a Heaf gun with disposable single-use heads; each head has six needles arranged in a circle. There are standard heads and pediatric heads: the standard head is used on all patients aged 2 years and older; the pediatric head is for infants under the age of 2. For the standard head, the needles protrude 2 mm when the gun is actuated; for the pediatric heads, the needles protrude 1 mm. Skin is cleaned with alcohol, then tuberculin (100,000 units/ml) is evenly smeared on the skin (about 0.1 ml); the gun is then applied to the skin and fired. The excess solution is then wiped off and a waterproof ink mark is drawn around the injection site. The test is read 2 to 7 days later.
- Grade 0: no reaction, or induration of 3 or less puncture points;
- Grade 1: induration of four or more puncture points;
- Grade 2: induration of the six puncture points coalesce to form a circle;
- Grade 3: induration of 5 mm; or more
- Grade 4: induration of 10 mm or more, or ulceration
It is not easy to translate between Heaf and Mantoux, but
- Heaf grade 0 & 1 ~ Mantoux less than 5 mm;
- Heaf grade 2 ~ Mantoux 5–14 mm;
- Heaf grade 3 & 4 ~ Mantoux 15 or greater
The tuberculin used for Heaf tests is 1000 times more concentrated than that used for Mantoux tests. In countries where both tests are used, use of the correct concentration avoids false positive and false negative results.
Tuberculin conversion
Tuberculin conversion is said to occur if a patient who has previously had a negative tuberculin skin test develops a positive tuberculin skin test at a later date. This is strong evidence for significant exposure to TB. The UK recommendation is that the two tests be done at least six weeks apart; the U.S. recommendation is that the two tests can be done as little as one week apart.Boosting
The phenomenon of boosting occurs when people who have had remote infection with Mycobacterium tuberculosis and/or previous exposure to Bacille Calmette Guerin of Mycobacterium bovisMycobacterium bovis
Mycobacterium bovis is a slow-growing , aerobic bacterium and the causative agent of tuberculosis in cattle...
(BCG), an attenuated strain of Mycobacterium bovis
Mycobacterium bovis
Mycobacterium bovis is a slow-growing , aerobic bacterium and the causative agent of tuberculosis in cattle...
that is used in some countries as a vaccine against tuberculosis are given repeated tuberculin skin tests. In these people, the first test revives or primes the immune response so that on repeat testing, the response is much stronger and the patient then looks as if he now has a positive reaction. The second tuberculin skin test result is the correct one.
The UK and U.S. guidelines approach the phenomenon of boosting differently. Under U.S. guidelines, which say to ignore previous immunisation with BCG, a person showing the phenomenon of boosting will be falsely described as a tuberculin converter. On the other hand, UK guidelines advise two tuberculin skin tests one week apart if boosting is suspected, taking the result of the second test as being the true result.
Boosting can occur up to two years after the first Mantoux test.
Interpretation of tuberculin skin tests
According to the U.S. guidelines, latent tuberculosis is diagnosed on a Mantoux test if there is more than 10 (recent immigrant, under age of 4 or have other risk factors for the disease) or 15 mm (no risk factors) of induration. In high risk groups, such as those who are HIV positive, the cut-off is 5 mm on induration. The U.S. guidelines recommend that a history of previous BCG vaccination should be ignored. For details of tuberculin skin test interpretation, please refer to the CDC guidelines (reference given below).The UK guidelines are formulated according to the Heaf test: In patients who have had BCG previously, latent TB is diagnosed if the Heaf test is grade 3 or 4 and have no signs or symptoms of active TB; if the Heaf test is grade 0 or 1, then the test is repeated and. In patients who have not had BCG previously, latent TB is the Heaf test if grade 2, 3 or 4, and have no signs or symptoms of active TB. Repeat Heaf testing is not done in patients who have had BCG (because of the phenomenon of boosting). For details of tuberculin skin test interpretation, please refer to the BTS guidelines (references given below).
Given that the US recommendation is that prior BCG vaccination be ignored in the interpretation of tuberculin skin tests, false positives are possible as a result of: (1) people who have previously had BCG (even many years ago) may still have a false positive Mantoux test, and (2) serial testing with tuberculin skin tests boosts the immunological response in those people who have previously had BCG, so these people will falsely appear to be tuberculin converters. This may lead to treating more people than necessary, with the possible risk of those patients suffering adverse drug reactions. However, as Bacille Calmette-Guérin vaccine is not 100% effective, and is less protective in adults than pediatric patients, not treating these patients could lead to a possible infection. The current US policy seems to a reflect a desire to err on the side of safety (of the general public).
The U.S. guidelines also allow for tuberculin skin testing in immunosuppressed patients (those with HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
, or who are on immunosuppressive drugs), whereas the UK guidelines recommend that tuberculin skin tests should not be used for such patients because it is unreliable.
γ-interferon testing
The role of gamma interferon tests is under going constant review and various guidelines have been published with the option for revision as new data comes to hand.CDC:MMWR Health Protection Agency:UKThere are currently (26 March 2009) three commercially available interferon-γ release assays (IGRAs): QuantiFERON-TB Gold, QuantiFERON-TB Gold In-Tube and T-SPOT.TB
T-SPOT.TB
T-SPOT.TB is a type of ELISPOT assay used for tuberculosis diagnosis. It is available in most European countries, the United States as well as various other territories. It was developed by researchers at the University of Oxford in England. It counts the number of effector T cells, white blood...
. These tests are not affected by prior BCG vaccination, and look for the body's response to specific TB antigens not present in other forms of mycobacteria and BCG (ESAT-6
ESAT-6
ESAT-6, the 6 kDa early secretory antigenic target of Mycobacterium tuberculosis, is a secretory protein and potent T cell antigen. It is used in tuberculosis diagnosis by the whole blood interferon γ test QuantiFERON-TB Gold, in conjunction with CFP-10 and TB7.7.ESAT-6 has been shown to directly...
). Whilst these tests are new they are now becoming available globally.
CDC:
CDC recommends that QFT-G may be used in all circumstances in which the TST is currently used, including contact investigations, evaluation of recent immigrants, and sequential-testing surveillance programs for infection control (e.g., those for health-care workers).
HPA Interim Guidance:
The HPA recommends the use of IGRA testing in health care workers, if available, in view of the importance of detecting latently infected staff who may go on to develop active disease and come into contact with immunocompromised patients and the logistical simplicity of IGRA testing.
Treatment
The treatment of latent tuberculosis infection (LTBI) is essential to controlling and eliminating TB by reducing the risk that TB infection will progress to disease. The gold standard of treatment is nine months of isoniazidIsoniazid
Isoniazid , also known as isonicotinylhydrazine , is an organic compound that is the first-line antituberculosis medication in prevention and treatment. It was first discovered in 1912, and later in 1951 it was found to be effective against tuberculosis by inhibiting its mycolic acid...
, and this regimen is still widely used in the U.S. (but not elsewhere).
Terminology
There is no agreement regarding terminology: the terms preventive therapy and chemoprophylaxis have been used for decades, and are preferred in the UK because it involves giving medication to people who have no disease and are currently well: the reason for giving medication is primarily to prevent people from becoming unwell. In the U.S., physicians talk about latent tuberculosis treatment because the medication does not actually prevent infection: the person is already infected and the medication prevents existing silent infection from becoming active disease. There are no convincing reasons to prefer one term over the other.Treatment regimens
It is essential that assessment to rule out active TB be carried out before treatment for LTBI is started. To give treatment for latent tuberculosis to someone with active tuberculosis is a serious error: the tuberculosis will not be adequately treated and there is a serious risk of developing drug-resistant strains of TB.There are several treatment regimens currently in use:
- 9H — IsoniazidIsoniazidIsoniazid , also known as isonicotinylhydrazine , is an organic compound that is the first-line antituberculosis medication in prevention and treatment. It was first discovered in 1912, and later in 1951 it was found to be effective against tuberculosis by inhibiting its mycolic acid...
for 9 months is the gold standard (93% effective). - 6H — Isoniazid for 6 months might be adopted by a local TB program based on cost-effectiveness and patient compliance. This is the regimen currently recommended in the UK for routine use. The U.S. guidance excludes this regimen from use in children or persons with radiographic evidence of prior tuberculosis (old fibrotic lesions) (69% effective).
- 6 to 9H2 — An intermittent twice-weekly regimen for the above 2 treatment regimens is an alternative if administered under Directly observed therapy (DOT).
- 4R — Rifampin for 4-months is an alternative for those who are unable to take isoniazid or who have had known exposure to isoniazid-resistant TB.
- 3HR — Isoniazid and rifampin may be given daily for three months.
- 2RZ — The two month regimen of rifampin and pyrazinamidePyrazinamidePyrazinamide is a drug used to treat tuberculosis. The drug is largely bacteriostatic, but can be bacteriocidal on actively replicating tuberculosis bacteria.-Abbreviations:...
is no longer recommended for treatment of LTBI because of the greatly increased risk of drug-induced hepatitis and death. - 3RPT/INH - three-month (12-dose) regimen of weekly rifapentineRifapentineRifapentine is an antibiotic drug used in the treatment of tuberculosis.-History:...
and isoniazid.
Multi-drug-resistant TB
There is no evidence for any regimen used for persons with known exposure to MDR-TB and no consensus on optimal treatment. A regimen consisting of ethambutolEthambutol
Ethambutol is a bacteriostatic antimycobacterial drug prescribed to treat tuberculosis. It is usually given in combination with other tuberculosis drugs, such as isoniazid, rifampicin and pyrazinamide....
and PAS has been used before. It would appear sensible to choose a combination of antibiotics based on the known sensitivities of the organism. The CDC
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
have recommended a combination of pyrazinamide
Pyrazinamide
Pyrazinamide is a drug used to treat tuberculosis. The drug is largely bacteriostatic, but can be bacteriocidal on actively replicating tuberculosis bacteria.-Abbreviations:...
and ethambutol
Ethambutol
Ethambutol is a bacteriostatic antimycobacterial drug prescribed to treat tuberculosis. It is usually given in combination with other tuberculosis drugs, such as isoniazid, rifampicin and pyrazinamide....
, with either pyrazinamide
Pyrazinamide
Pyrazinamide is a drug used to treat tuberculosis. The drug is largely bacteriostatic, but can be bacteriocidal on actively replicating tuberculosis bacteria.-Abbreviations:...
or fluoroquinolone. Immunocompetent contacts should be treated for 6 months; immunocompromised contacts should be treated for 12 months.
Research
Although a tuberculosis cure was developed more than 50 years ago, TB continues to kill from 2 to 3 million people every year. According to the World Health OrganizationWorld Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
(WHO) approximately 36 million people will die of tuberculosis by 2020 if it is not controlled. They add that eight million people develop active tuberculosis every year. Approximately 98 percent of those victims are from developing countries. Furthermore, WHO estimates that approximately one-third of the world's population are carriers of latent tuberculosis.
Therefore, the scientific community continues its research efforts to learn more from this disease in order to develop more options for possible treatments.
The factors that trigger latent tuberculosis infection to progress into active disease have been unknown. However, Professor David Russell and his group at Cornell University in New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
, USA, recently demonstrated that the bacteria responsible for causing TB are able to hijack fat metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
in the host to drive the progression of the disease.
The research made clear that the Mycrobacterium tuberculosis is able to stimulate the immune cells they infect resulting in the accumulation of fat droplets. These droplets turn into what they called “foamy” cells and such transformation can trigger a reawakening of the TB infection from its latent state.
Professor Russell believes that more knowledge about the bacterium's life cycle and its host interactions will open possibilities to develop new treatments.
Another group of researchers at Sydney's Centenary Institute made an important discovery that could lead to the development of a new drug for TB. The team, led by Dr Nick West, investigated a protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
that is essential for TB to survive and later they reported some success in developing a drug that would inhibit this protein. If the group is successful in finding a way to treat latent tuberculosis, millions of people around the world could be saved.
Furthermore, researchers from the Genome Institute of Singapore together with collaborators in The Netherlands, Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, and the Russian Federation, identified a new gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
that would provide susceptibility to pulmonary tuberculosis. The gene is named Toll-like receptor 8 (TLR8) and it recognizes some factors from viruses such as HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
. This gene is believed to also have a role in human susceptibility to Mycobacterium tuberculosis infections. This discovery could open new options for therapeutic interventions.