Infectious disease represents one of the most important health problems in the world, particularly in developing countries. Tuberculosis is considered to be the single most important infectious disease. Although there is an effective treatment for tuberculosis, diagnosis is still a considerable obstacle to effective disease control. The WHO estimates that 1,7 billion people are infected by M. tuberculosis and 20 million people have active tuberculosis; most of them with lung lesions and half of the cases are contagious. Active tuberculosis is growing by 8 to 10 million each year and 3 million deaths occur each year.
Laboratory diagnosis of tuberculosis relies on microscopic examination and on the culture of Mycobacterium tuberculosis from clinical specimens. However the smear examination is not always satisfactory and culturing the organism is time consuming (3 to 4 weeks) and expensive. In looking for tools to detect mycobacteria the use of immunodiagnosis system represents an alternative for quickly diagnosing the tuberculosis infection. Lipoarabinomannan (LAM), which is a major anitgen of the mycobacterial cell walls, is released in blood and urine during an active tuberculosis infection, and this has been chosen as a target to develop our immunodiagnostic reagent.
The rapid latex agglutination test being developed to diagnose active tuberculosis infection is based on the following principle: the latex microparticles are coated with specific polyclonal and/or monoclonal anitbodies anti LAM molecule. The binding of the antibodies is done by absorption, or covalently on the polystyrene microparticles. The final product is an homogeneous suspension of these microsphere particles, stored in a stabliser buffer.
The aim of the project was to develop a simple, efficient and cheap test for the diagnosis of tuberculosis and other mycobacteria infections based on the dectection of LAM's antigens (lipoarabinomannan) in the urine. This test will not require any high security (P3) laboratories as the samples can be sterilised by heat treatment before analysis, and hence field adapted.
The innovation of the solution lies in the identification of specific mycobacterial components in the urine of active tuberculosis patients. Neither syringes nor qualified personal are required to obtain the test material, the use of the diagnostic kit requires the minimal training of the laboratory personal, and the method can be performed practically anywhere. The procedure is particularly adapted to the situation in developing countries. The only requirement is to put the urine in contact with latex micro beads covered with antibodies that will agglutinate upon the presence of LAM antigen in the urine. The agglutinates are then easily detected by the naked eye.