Novel Generation Mycobacterial Adjuvant Based on Liposome-Encapsulated Monomycoloyl Glycerol from Mycobacterium bovis Bacillus Calmette-Guérin

Abstract

The immunostimulatory activity of lipids associated with the mycobacterial cell wall has been recognized for several decades and exploited in a large variety of different adjuvant preparations. Previously, we have shown that a mycobacterial lipid extract from Mycobacterium bovis bacillus Calmette-Guérin delivered in cationic liposomes was a particular efficient Th1-inducing adjuvant formulation effective against tuberculosis. Herein, we have dissected the adjuvant activity of the bacillus Calmette-Guérin lipid extract showing that the majority of the activity was attributable to the apolar lipids and more specifically to a single lipid, monomycoloyl glycerol (MMG), previously also shown to stimulate human dendritic cells. Delivered in cationic liposomes, MMG induced the most prominent Th1-biased immune response that provided significant protection against tuberculosis. Importantly, a simple synthetic analog of MMG, based on a 32 carbon mycolic acid, was found to give rise to comparable high Th1-biased responses with a major representation of polyfunctional CD4 T cells coexpressing IFN-γ, TNF-α, and IL-2. Furthermore, comparable activity was shown by an even simpler monoacyl glycerol analog, based on octadecanoic acid. The use of these synthetic analogs of MMG represents a promising new strategy for exploiting the immunostimulatory activity and adjuvant potential of components from the mycobacterial cell wall without the associated toxicity issues observed with complex mycobacterial preparations.

Polyfunctional CD4+ T Cells As Targets for Tuberculosis Vaccination

“…Several adjuvanted recombinant Mtb proteins or fusions of multiple Mtb proteins have been shown to elicit polyfunctional CD4 + T cells in mice, including recombinant Ag85B (50), and MT1721 (51) and fusion proteins comprised of ESAT-6 fused to the n-terminus of Ag85B (E6-85) (43), Ag85B/TB10.4 (H4) (40, 52), Ag85B/ESAT-6 (H1) (38, 41, 53), and gene products of Rv2608, Rv3619, Rv3620, and Rv1813 (ID93) (54). These recombinant protein vaccines have successfully utilized several different adjuvant formulations based upon immunostimulatory lipids (38, 40, 41, 43, 53, 54) or nucleotides (50–52) to elicit these T cell responses. In addition, adjuvanted recombinant protein vaccines induce polyfunctional CD4 + T cell responses when used alone (40, 41, 43, 50, 52–54) and when administered as a boost after BCG prime (38, 43) or a DNA vaccine prime (51).…”

Contribution of MINCLE–SYK Signaling to Activation of Primary Human APCs by Mycobacterial Cord Factor and the Novel Adjuvant TDB

“…There is a lack of adjuvants inducing robust Th1 or Th17 immune responses to protein Ag in humans because CFA is too toxic for application in humans. The synthetic cord factor analog, trehalose-6,6-dibehenate (TDB), has been developed together with a liposomal carrier as the so-called CAF01 adjuvant system (12)(13)(14)(15). Although TDM and TDB share the same trehalose disaccharide head group, the two ester-linked lipid tails differ, with mycolic acids of 60-90 carbons (C) for TDM and 22C behenic acids in case of TDB.…”

Multi-walled carbon nanotubes functionalized with recombinant Dengue virus 3 envelope proteins induce significant and specific immune responses in mice

“…The wall components of inactivated mycobacteria (present in the complete form of the Freund’s adjuvant) are potent inducers of T cell-mediated responses and are known to activate human TLR2 and TLR4 [39]. Isolated components of mycobacteria cell wall have been proven less reactogenic than full cell extracts while retaining important Th1-biased immune-stimulatory properties [39, 40]. Experimental vaccines using such components have shown promising results against a variety of infectious diseases [41, 42], including dengue [43].…”