The growth of this disease remains particularly strong in Africa owing to a high proportion of HIV patients (nearly 13% compared with less than 1% in Asian countries for example). This region of the world is experiencing accelerating advance of a deadly combination of AIDS and TB, developed because the virus weakens the immune system of TB-infected individuals.
A person infected by HIV who is also contaminated with Koch’s bacillus bears a greater risk of developing active TB than a non HIV-infected individual. Latent TB infection diagnosis has for several decades been founded on a positive response to the tuberculin skin test (TST). However, TST’s reliability is limited in highly TB-endemic geographical settings because the presence in the environment of mycobacteria similar to that which causes TB plus the BCG vaccination people receive in early infancy can skew the results.
Moreover, in HIV-carrying patients, the sensitivity of the test is drastically reduced owing to their inability to develop an allergic reaction, the very basis of the skin test. TB is a strong contributing factor to HIV mortality, therefore it is of crucial importance to be able to diagnosis latent infection early in order to adopt an appropriate treatment and prevent the development of the full disease.
The development of new IGRA3 tests is based on in vitro measurement of T-cells secretion of interferon-? when challenged with antigens specific to Mycobacterium tuberculosis, the bacterium causing tuberculosis. Such assays now provide a means of getting round the drawbacks of the tuberculin skin test (TST). Yet, although these new screening methods are more effective than TST in a situation of low TB endemicity, their validity in populations subject to high risk of latent TB infection still has to be clearly established.
Results recently published of an investigation conducted in Senegal, coordinated by IRD in conjunction with other scientific institutions,1 yield important information on the comparative efficiency of the immunological method and the standard TST. The research team set up two cohorts of patients living in the Dakar area: the first one made up of HIV-infected individuals but with no detected TB; the second consisting of TB patients and people from the treatment centre who had been in contact with them during a given period.
For the first cohort, 285 adults newly infected by HIV and showing no clinical or radiological sign of TB were selected at the Fann National University Hospital Centre (Dakar) between 2003 and 2004. An ELISPOT test and a TST were performed for each patient at the beginning of the study. The TST indicated that 21% (53/247) of them had a TB infection at the moment of the test. However, this proportion reached 51% (125/247) with the ELISPOT test. It appears therefore that the latter is more sensitive than the TST whatever the stage of development of the disease. Nevertheless the ability to respond to the ELISPOT test decreases with the decrease in CD4 lymphocyte count, which appears to indicate the limits of this type of test in severely immunosuppressed individuals, as advanced-stage HIV infected patients can be.
In parallel, a cohort of 243 TB patients was followed up for 2 years. The objective this time was to determine the ability of the ELISPOT test to predict, among people living in contact with these individuals, those who run the greatest risk of developing the disease. Between January 2004 and March 2005, 3072 contacts were identified for the whole set of TB patients. Preliminary results showed the sensitivity of the two tests to be comparable with this cohort, although ELISPOT is doted with a better specificity since it is not influenced by recent BCG vaccination.
The data gathered from the studies must now be analysed in greater detail in order to determine if the new tests based on measurement of the immune response to M. tuberculosis-specific antigens can serve as a reliable diagnostic method for TB infection in geographical areas where the disease is endemic and BCG coverage is strong. Such investigations should also found out if in the future these tests could be used as markers of the development of the disease within a given population.
Grégory Fléchet - DIC
Grégory Fléchet | alfa
The genes are not to blame
20.07.2018 | Technische Universität München
Targeting headaches and tumors with nano-submarines
20.07.2018 | Universitätsmedizin der Johannes Gutenberg-Universität Mainz
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences