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Tuberculosis (TB) is
caused by repeated exposure to airborne
droplets contaminated with a rod-shape
bacterium, Mycobacterium tuberculosis.
The TB bacterium is also known as
the tubercle bacillus. A person with
active pulmonary tuberculosis can
spread the disease by coughing and
sneezing. Once the person is infected
with Mycobacterium tuberculosis, the
infection will slowly progress to
disease. More than 8 million new cases
of Tuberculosis (TB) have been diagnosed
each year and are responsible for
more than three million deaths per
year. Almost two and three quarter
billion people (2.75 billion) or 33%
of population are latently infected
with TB.
Among screening infectious diseases,
a rapid and accurate diagnostic method
of tuberculosis is very important
for human health maintain and the
disease control. At present, the clinical
check (X-ray) coupling with the microscope
examination and specimen bacterial
culture is the major diagnostic method
for the tuberculosis. However, this
often takes 4-6 weeks, and the results
sometime inaccurate. In the early
days, the antibody detection in the
blood test was regarded as a convenient
method. However, its sensitivity and
specificity appeared very poor. For
the last 50 years, the successful
program for screening tuberculosis
is based on the tuberculin skin test
(TST) by using the purified protein
derivates (PPD) to stimulate the T
cells. However, the major drawback
of TST with PPD is its cross-reaction
with BCG immunized persons.
To improve the tuberculosis diagnosis
we search for the specific antigens
and produce their antibodies, then,
prepare diagnostic kits for the detection
of antibodies and antigens in body
fluid. By using techniques of biotechnology,
Mahairas et al. have identified some
M. tuberculosis specific antigens.
They employed subtractive genomic
hybridization analysis to identify
genetic differences between virulent
M. bovis and M. tuberculosis and attenuated/avirulent
BCG. Three distinct genomic regions
of difference, designated RD1, RD2,
and RD3, were found deleted in BCG.
The specific proteins encoded from
the regions of difference (RDs) gene
clusters in M. tuberculosis have been
chosen as the specific antigens for
the diagnosis of tuberculosis, and
some proteins have been cloned and
expressed, and their antibodies were
also prepared both as monoclonal and
polyclonal forms. In our invention,
various devices of immunoassays such
as radio-immunoassay, enzyme immunoassay,
immunochromatographic assay device,
fluorescence immunoassays, immunoblotting
and dot immunobinging, luminescence
immunoassay, immuno-agglutination,
biological chips can be used to develop
an in vitro tuberculosis diagnostic
kit by comprising these antigens and
antibodies.
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