Rational design of a hydrolysis-resistant mycobacterial phosphoglycolipid antigen presented by CD1c to T cells

Abstract

Whereas proteolytic cleavage is crucial for peptide presentation by classical major histocompatibility complex (MHC) proteins to T cells, glycolipids presented by CD1 molecules are typically presented in an unmodified form. However, the mycobacterial lipid antigen mannosyl-β1-phosphomycoketide (MPM) may be processed through hydrolysis in antigen presenting cells, forming mannose and phosphomycoketide (PM). To further test the hypothesis that some lipid antigens are processed, and to generate antigens that lead to defined epitopes for future tuberculosis vaccines or diagnostic tests, we aimed to create hydrolysis-resistant MPM variants that retain their antigenicity. Here, we designed and tested three different, versatile synthetic strategies to chemically stabilize MPM analogs. Crystallographic studies of CD1c complexes with these three new MPM analogs showed anchoring of the lipid tail and phosphate group that is highly comparable to nature-identical MPM, with considerable conformational flexibility for the mannose head group. MPM-3, a difluoromethylene-modified version of MPM that is resistant to hydrolysis, showed altered recognition by cells, but not by CD1c proteins, supporting the cellular antigen processing hypothesis. Furthermore, the synthetic analogs elicited T cell responses that were cross-reactive with nature-identical MPM, fulfilling important requirements for future clinical use.

Lipids Extracted from Mycobacterial Membrane and Enveloped PLGA Nanoparticles for Encapsulating Antibacterial Drugs Elicit Synergistic Antimicrobial Response against Mycobacteria

“…Although the lipid-based and lipid-associated antigens from M. tuberculosis have been extracted before, details of the composition of these antigens are not clearly understood . In this study, we have characterized and compared the composition of lipids extracted from M.…”

“…Although the lipid-based and lipid-associated antigens from M. tuberculosis have been extracted before, details of the composition of these antigens are not clearly understood. 34 In this study, we have characterized and compared the composition of lipids extracted from M. smegmatis using three different methods. The highest lipid extraction efficiency and encapsulation efficiency of SRB were obtained with Method 3 relying on a solvent consisting of CH 2 Cl 2 /CH 3 OH (2:1, v/v), which may be attributed to decreased polarity when compared with solvents used in Method 1 or Method 2 and was defined as the best way to form LrNs.…”

Spotlight on mycobacterial lipid exploitation using nanotechnology for diagnosis, vaccines, and treatments

“…, 36. , 37. have been described, and chemical probes for tagging mycobacterial lipids are available as well.…”

“…In M. tuberculosis , the lipids identified as CD1-restricted T-cell antigens are mycolic acids (MA), glucose- and glycerol-monomycolates (GMM, GroMM), LAM, PIMs, diacyltrehalose (DAT) and mannosyl-phosphomycoketide (MPM), 36. , 37. , 95.…”