Purification of Native Ag85 Complex, 38-kDa and MTB12 Protein Antigens from the Culture Filtrate ofMycobacterium tuberculosis

Biorecognition and detection of antigens from Mycobacterium tuberculosis using a sandwich ELISA associated with magnetic nanoparticles

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is one of the 10 leading causes of death worldwide, especially in low-income areas. A rapid, low-cost diagnostic assay for TB with high sensitivity and specificity is not currently available. Bio-functionalized magnetic nanoparticles (MNPs) which are able to efficiently detect and concentrate biomolecules from complex biological samples, allows improving the diagnostic immunoassays. In this way, a proof-of-concept of MNP-based sandwich immunoassay was developed to detect various MTB protein antigens. The superficial and secretory antigenic proteins considered in this research were: CFP10, ESAT6, MTC28, MPT64, 38 kDa protein, Ag85B, and MoeX. The proteins were cloned and expressed in an E. coli system. Polyclonal antibodies (ab) against the recombinant antigens were elicited in rabbits and mice. Antibodies were immobilized on the surface of amine-silanized nanoparticles (MNP@Si). The functionalized MNP@Si@ab were tested in a colorimetric sandwich enzyme-linked immunosorbent assay (sELISA-MNP@Si@ab) to recognize the selected antigens in sputum samples. The selected MTB antigens were successfully detected in sputum from TB patients in a shorter time (~ 4 h) using the sELISA-MNP@Si@ab, compared to the conventional sELISA (~15 h) standardized in home. Moreover, the sELISA-MNP@Si@ab showed the higher sensitivity in the real biological samples from infected patients.

Therapeutic effects of mycobacterial secretory proteins against established asthma in BALB/c mice

Purpose

Live/killed mycobacteria and culture supernatants can suppress asthmatic reactions. This study investigated whether mycobacterial secretory proteins have therapeutic effects on asthma.

Methods

Mycobacterium bovis bacille Calmette-Guérin (BCG; 2×10⁵ CFUs) and mycobacterial secretory proteins (Ag85 complex, 38-kDa protein or MPB70; 4 or 20 µg) were administered intraperitoneally to female BALB/c mice with established airway hyperresponsiveness. One week after treatment, the mice underwent a methacholine challenge test, and then inflammatory cell numbers in bronchoalveolar lavage fluid (BAL) and around bronchi (<500 µm), and cytokine levels in splenocyte supernatants, were assessed.

Results

BCG and all of the tested secretory proteins significantly improved airway sensitivity compared to baseline values (P<0.05). The secretory protein Ag85 complex significantly suppressed airway reactivity also (P<0.05), while 38-kDa protein significantly suppressed reactivity and maximal narrowing (P<0.05). The number of eosinophils in BAL and around bronchi, and the goblet cell proportion, were also significantly reduced in mice in both the BCG and secretory protein groups compared to the asthma control group. IFN-γ/IL-5 ratios were significantly higher in mice treated with BCG, 4 µg MPB70 or 4 µg 38-kDa protein than in asthma control mice (P<0.05), and were negatively associated with airway hyperresponsiveness, peribronchial eosinophil numbers and goblet cell proportion (all P<0.05). IL-17A was positively correlated with IL-5 (r=0.379, P<0.001), maximal airway narrowing, peribronchial eosinophil numbers and goblet cell proportion (all P<0.05).

Conclusions

Secretory proteins from BCG and M. tuberculosis and live BCG were effective against established asthma, their effects being accompanied by increased IFN-γ/IL-5 ratios. Thus, allergic asthma could be effectively treated with mycobacterial secretory proteins.