Project Overview (live on website)

Background information

All mycobacteria, including the etiologic agent of tuberculosis (TB)–M. tuberculosis, have complex cell walls critical for their immunopathogenicity. Specifically, the lipopolysaccharide antigen–lipoarabinomannan (LAM)—can be recognized by antibodies in infected individuals. Lowary group had previously identified a hexasaccharide fragment (Ara₆) derived from LAM as a promising agent for TB diagnosis. This antigen, however, exhibit suboptimal specificity in real world samples because many non-infected patients possess diverse anti-LAM antibodies due to previous exposure to other mycobacteria species, hence inaccurately diagnosed as TB(+).

Expected key outcome

To improve the specificity the Ara₆ antigen, we use genetically-encoded fragment-based discovery (GE-FBD)¹ to discover glycopeptide sequences with enhanced affinity and specificity towards anti-LAM antibodies than the Ara₆ antigen alone. Our proposal aims to test whether these glycopeptides can also serve as discriminatory antigens for real world samples, such as TB(+) and TB(-) serum samples, and further be developed into efficient, cost-effective serological tests.

Research significance

The WHO stresses the importance of much faster, targeted research for serological and/or point-of-care tests with improved accuracy for TB diagnosis. Successful implementation of this proposal can address this issue. While low-cost devices and development of diagnostics is not the main focus, we develop our proposal around simple-to-make glycopeptide antigens. In the long term, the combination of glycopeptides and simple carbohydrates can provide a greater diversity of biomarkers, which can be incorporated into rapid, low-cost point-of-care serological tests with higher specificity and sensitivity than existing serological tests on the market. 

1. Ng, S., et al., Genetically Encoded Fragment-Based Discovery of Glycopeptide Ligands for Carbohydrate-Binding Proteins. J. Am. Chem. Soc. 2015, 137, 5248-5251.