MRC PhD students

His research project is aimed at determining the reproducibility of the ESPRIT biosensor from serum samples prepared from HIV positive blood clinically assessed to confirm their TB status from Pretoria Academic Hospital.

Tuberculosis has re-emerged as a global health problem due to co-infection with HIV and the emergence of drug resistant strains of Mycobacterium tuberculosis. HIV co-infection introduced a 30% underestimation in TB diagnosis based on sputum analysis, calling for a reliable and fast serodiagnostic assay to assist in the management of TB in HIV burdened populations. In this study, free mycolic acids have been considered because they are unique in structure to each species of Mycobacterium and can be economically extracted and purified. In standard immunoassay such as ELISA, however, an unacceptable number of false positive and negative test results were obtained. In this study a much-improved biosensor (IAsys) method to detect antibodies to mycolic acids in patient sera as surrogate markers of active tuberculosis was shown. The accuracy of the inhibition test was 84% if HIV positive patients were excluded for whom a negative TB sputum analyses could not be relied upon to serve as a reference standard. If biosensor technology could be made amenable for high throughput screening, then it may provide the solution to the serodiagnosis of tuberculosis against HIV burden population.

The EDCPT (European and Developing Countries Clinical Trials Partnership) samples were analysed on the ESPRIT biosensor to explore the application of the assay by monitoring the progression of TB during chemotherapy with detection of anti-mycolic acids antibodies level in serum. The ESPRIT biosensor has demonstrated that the MARTI (Mycolic Acids Real-Time Inhibition) assay can distinguish between the MDR infected and cured patients. The results obtained in this study clearly correspond with the clinical assessment of the patients after completing their TB treatment. But, more patient sera are being analysed to determine the reliability of the MARTI-assay in its application to monitor the progression of tuberculosis and compliance of TB treatment. To analyse HIV positive serum on ESPRIT biosensor collected from Pretoria Academic hospital, to determine the accuracy of the MARTI assay in the HIV-burdened population.

The new MARTI assay diagnostic test proposed here will substantially shorten the time required to obtain a result in comparison to sputum smear analysis. HIV and TB is a lethal combination and results in millions of deaths annually, especially in sub-Saharan Africa. It is imperative that TB+ HIV+ patients be diagnosed quickly and placed on a treatment regime. If not these individuals continue to spread the disease, and place themselves at risk of succumbing to the TB infection. The results on the MARTI assay to verify TB infection is also rapid, with results available within hours after sampling, although throughput is currently still limited.  The main focus of this project is to have a multi-channel assay for TB detection. The MARTI assay will be commercialised after validation of the results.

This study is supervised by Professor Jan van Schoor in the MRC TB Epidemiology and Intervention Research Unit.