Tuberculosis(TB) is caused by repeated exposure to airborne droplets contaminated with a rod-shape bacterium, Mycobacterium tuberculosis(MTB). 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 antigens in culture filtrate. 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.

Antigen detection:

Many clinical specimens has recommended the use of liquid medium for primary culture and susceptibility testing and identification testing to achieve better as well as faster results. Our product have developed and found several secreted mycobacteria proteins that showed promise in diagnostic use. Even though liquid medium allows less time for the detection of positive cultures for identifying. Identification of the different of mycobacterium tuberculosis from mycobacteria other than mycobacterium tuberculosis.

The secreted proteins are highly specific for the mycobacterium tuberculosis complex. We have studied the secreted proteins from the mycobacterium tuberculosis complex that showed as a tuberculin skin test by using the purified protein derivates to differentiate with BCG immunized persons. It was not happened cross reaction.

Now, our company utilized the specificity of the monoclonal antibodies against the secreted proteins to develop a quickly, accuracy, simple and inexpensive test product. The test product utilized a principle of immunochromatographic assay which monoclonal antibodies are conjugated with colloidal gold particles and are immobilized at the nitrocellulose membrane. If the target proteins present in the sample from liquid medium are rehydrated by monoclonal antibodies, the nitrocellulose membrane has presented a red band that it indicates the presence of the mycobacterium tuberculosis complex, but if there is no band then it indicates the presence of mycobacteria other than mycobacterium tuberculosis.

The novelty and new functions of the antigens detection kit in our invention are:

(1) The first kit in the world to identify the M. tuberculosis complex.
(2) Differentiate between active and latent tuberculosis.
(3) No cross-reaction with other Mycobacterium and BCG strains, showing negative response for the BCG immunized subjects and non tuberculosis patients.
(4) In vitro testing, and no risk for the medical personnel, and the patients no need to return for clinical reexamination.
(5) Rapid and simple procedures.
(6) Both high sensitivity and specificity.