Roghayeh Teimourpour , Zahra Meshkat , Mohsen Arzanlou , Hadi Peeridogaheh , Aida Gholoobi ,
Volume 74, Issue 10 (January 2017)
Abstract
Background: Despite advances in the vaccinology and chemotherapy in the past century, tuberculosis is still responsible for two million deaths every year. Emergence of multi-drug resistant strain and coinfection of TB-HIV make it a serious concern. Treatment and control of tuberculosis is a great health burden in every community. Active tuberculosis in children has very severe consequences especially those who are under 5-years-old, therefore vaccine indication should be taken. Bacille Calmette-Guérin (BCG) is a live attenuated strain of Mycobacterium bovis that has been used for providing immunity or protection against tuberculosis (TB). In addition, BCG provides relative protection against leprosy and Buruli ulcer, it also can be used for treatment of bladder cancer. BCG is the most widely administered vaccine around the world. It has been given to over three billion individuals over the past decades. At first it was developed in 1908 at the Pasteur Institute in Lille by Albert Calmette and Camille Guérin. In fact BCG is a strain of Mycobacterium bovis that bear deletion in its genome following too long subculture in special media. Deletion in region of deletion 1 (RD1), a specific region of Mycobacterium bovis genome, has decreased pathogenicity of BCG strain. Following culture of BCG on different media since 1921 make genetic variation in the BCG strains that have specific characteristics. BCG should begin given to only immune-competent individuals and should not be administered to immunocompromised people. This vaccine is not effective in people formerly infected or sensitized with environmental mycobacteria. Previous meta-analysis studies indicate that BCG has variable range of protection from 0 to 80 percent against pulmonary TB, but is very effective against severe disseminated forms such as meningitis and miliary form of TB. Despite many research and develop new generation vaccine against TB, BCG vaccine still remains as the only effective vaccine because many efforts to replace it with better ones were unsuccessful.
Hadi Peeridogaheh , Roghayeh Teimourpour , Mohsen Arzanlou , Sina Rostami , Elham Raeisi ,
Volume 75, Issue 8 (November 2017)
Abstract
Historically, tuberculosis has been the leading cause of death throughout human history. Tuberculosis infection (TB) causes by Mycobacterium tuberculosis that is very dangerous and can affect any parts of the body, especially lungs. Tuberculosis infection still remains a serious threat to human public health due to its contagious nature, capability to stay latent form in host for indefinite time and then appear as active disease. It is estimated that one third of world’s population, nearly 2 billion persons are infected with Mycobacterium tuberculosis. Transmission occurs among people through inhalation of infected droplets. Lungs and especially alveolar macrophage are primary sites of infection. Mycobacterium tuberculosis bacilli by preventing fusion of phagosome with lysosome can remain alive inside the macrophages. Such situation defined as latent infection. In fact, persons with latent tuberculosis infection (LTBI) are only infected with M. tuberculosis without any sign of infectious. Latent infection in compared with active infection is not contagious, but in about 10-5 percent of people will develop active tuberculosis especially in elderly and people who use immunosuppressive drugs. Pulmonary TB is an active form of tuberculosis infection in which bacteria can spread among people by infected droplets. So identifying and treating people with latent TB infection can significantly reduce the progression of latent form to active infection. The tuberculin skin test (TST) is the most widely used test in worldwide that is applied to determine a person who is infected with M. tuberculosis. TST provide valubale information for diagnosis LTBI however its specificity can be reduced by bacillus Calmette-Guérin (BCG) vaccination and infected with non-tuberculous mycobacteria (NTM). In TST test host hypersensitivity responses to Purified protein derivative (PPD) from mycobacterium are evaluated. TST positive reaction indicates the presence of high risk for acquiring TB infection or progression of latent tuberculosis to active form. Previous studies indicated that there is correlation between TST response and subsequent risk of active TB. Experimental evidence has shown that treatment of latent infection in the basis of positive TST reduces the risk of active TB. Although TST is far from gold standard but it's low cost and simplicity make it a suitable laboratory test especially in developing country.
