Adjuvant formulation structure and composition are critical for the development of an effective vaccine against tuberculosis

Abstract

One third of the world is infected with Mycobacterium tuberculosis (Mtb) with eight million new cases of active tuberculosis (TB) each year. Development of a new vaccine to augment or replace the only approved TB vaccine, BCG, is needed to control this disease. Mtb infection is primarily controlled by TH1 cells through the production of IFN-γ and TNF which activate infected macrophages to kill the bacterium. Here we examine an array of adjuvant formulations containing the TLR4 agonist GLA to identify candidate adjuvants to pair with ID93, a lead TB vaccine antigen, to elicit protective TH1 responses. We evaluate a variety of adjuvant formulations including alum, liposomes, and oil-in-water emulsions to determine how changes in formulation composition alter adjuvant activity. We find that alum and an aqueous nanosuspension of GLA synergize to enhance generation of ID93-specific TH1 responses, whereas neither on their own are effective adjuvants for generation of ID93-specific TH1 responses. For GLA containing oil-in-water emulsions, the selection of the oil component is critical for adjuvant activity, whereas a variety of lipid components may be used in liposomal formulations of GLA. The composition of the liposome formulation of ID93/GLA does alter the magnitude of the TH1 response. These results demonstrate that there are multiple solutions for an effective formulation of a novel TB vaccine candidate that enhances both TH1 generation and protective efficacy.

Cryogenic transmission electron microscopy of recombinant tuberculosis vaccine antigen with anionic liposomes reveals formation of flattened liposomes

“…As reported previously, the liposomes are negatively charged, as expected due to the presence of the anionic DPPG. 7 Theoretical prediction of the pI of ID93 indicates a value of ∼4.7, which was confirmed by zeta potential measurement at different pH values ( Figure S1), indicating that the protein is negatively charged at neutral pH. This charge repulsion may explain why little association was detected between pro- International Journal of Nanomedicine 2014:9 tein and liposome when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) following size exclusion chromatography (SEC).…”

“…We have developed an anionic liposomal formulation containing GLA (GLA-LS) and demonstrated protective immune responses in mice when combined with ID93, 7 although T helper type 1 immunogenicity markers were not induced to the same magnitude as with GLA-SE. Interestingly, in contrast to GLA-SE, there appeared to be little association of ID93 with GLA-LS.…”

“…In fact, changing the liposome charge from anionic to cationic increased the ID93 association but not the immunogenicity or protective responses to the protein. 7 In order to achieve a greater understanding of the interactions between anionic liposomes and ID93, we carried out cryogenic transmission electron microscopy (cryo-TEM) analysis of each of the vaccine components alone as well as after mixing. Cryo-TEM is a high-resolution imaging technique that avoids interference from staining artifacts associated with traditional TEM approaches.…”

“…This charge repulsion may explain why little association was detected between pro- International Journal of Nanomedicine 2014:9 tein and liposome when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) following size exclusion chromatography (SEC). 7 However, in order to investigate whether any interactions were present between protein and liposome not detectable by SEC/SDS-PAGE, we subjected the ID93-liposome mixture to cryo-TEM analysis and compared the images to those obtained from each component alone as well as a negative stain TEM of ID93.…”

<em>Rehmannia glutinosa</em> polysaccharide liposome as a novel strategy for stimulating an efficient immune response and their effects on dendritic cells

“…11,27,28 This adjuvant activity depends on the structural characteristics of the liposomes, which control vesicle fate in vivo, including the mode of antigen interaction with antigen-presenting cells. 29 In this study, the physical properties of RGPL were investigated. In addition, based on our previous studies, the immunomodulatory effects of this novel delivery system were further researched.…”