About Ag85 / Mycobacterium Tuberculosis Major Secondary Protein Ag85 :
Mycobacterium Tuberculosis is a bacterium that is most well-known for causing tuberculosis (TB), an infection that primarily affects the lungs. Research into this disease has brought attention to the Mycobacterium Tuberculosis major secretory protein Antigen 85A, otherwise known as Ag85A.
The proteins of Antigen 85, including Ag85A, are the most common proteins found in the bacterium culture fluid and have a crystalline structure, although each of them is unique and therefore more suited for certain tasks.
They cause the bacteria to be attracted to fibronectin, an adhesive glycoprotein that helps the bacteria to attach itself to alveolar macrophages, which in turn colonize the lungs of humans or animals. This allows the bacterium to find a home in the lungs.
A85 proteins also help to maintain the structural integrity of the cell wall. They do this by catalyzing the transference of mycolic acids to arabinogalactan, and by synthesizing alpha-trehalose dimycolate (TDM). Both arabinogalactan and TDM are vital for maintaining cell wall integrity.
Ag85A is used to generate TB vaccines, such as the BCG (bacillus Calmette-Guérin) vaccine. When used in a vaccine, it causes an immune response by inducing strong T-cell proliferation in the subject. Also, as the Ag85 proteins make up so much of the bacterium culture fluid, they make an even more attractive target for further research and potential vaccine development. This is important as, while the BCG vaccine has been effective in many cases, some strains and presentations of TB have proved resistant.