Sulfated archaeol glycolipids: Comparison with other immunological adjuvants in mice

Abstract

Archaeosomes are liposomes traditionally comprised of total polar lipids (TPL) or semi-synthetic glycerolipids of ether-linked isoprenoid phytanyl cores with varied glyco- and amino-head groups. As adjuvants, they induce robust, long-lasting humoral and cell-mediated immune responses and enhance protection in murine models of infectious disease and cancer. Traditional total polar lipid (TPL) archaeosome formulations are relatively complex and first generation semi-synthetic archaeosomes involve many synthetic steps to arrive at the final desired glycolipid composition. We have developed a novel archaeosome formulation comprising a sulfated disaccharide group covalently linked to the free sn-1 hydroxyl backbone of an archaeal core lipid (sulfated S-lactosylarchaeol, SLA) that can be more readily synthesized yet retains strong immunostimulatory activity for induction of cell-mediated immunity following systemic immunization. Herein, we have evaluated the immunostimulatory effects of SLA archaeosomes when used as adjuvant with ovalbumin (OVA) and hepatitis B surface antigen (HBsAg) and compared this to various other adjuvants including TLR3/4/9 agonists, oil-in-water and water-in-oil emulsions and aluminum hydroxide. Overall, we found that semi-synthetic sulfated glycolipid archaeosomes induce strong Ag-specific IgG titers and CD8 T cells to both antigens. In addition, they induce the expression of a number of cytokines/chemokines including IL-6, G-CSF, KC & MIP-2. SLA archaeosome formulations demonstrated strong adjuvant activity, superior to many of the other tested adjuvants.

Simplified Admix Archaeal Glycolipid Adjuvanted Vaccine and Checkpoint Inhibitor Therapy Combination Enhances Protection from Murine Melanoma

“…While it was initially thought that entrapment of antigen within the archaeosome vesicle would enhance cytotoxic CD8 + T cell responses by delivering the antigen to the cytosol, allowing it to readily access MHC class I processing machinery that is necessary to initiate CD8 + T cell responses, these findings indicate that the inherent adjuvant effect of archaeosomes is sufficient to initiate CD8 + T cell responses towards exogenous antigens. Notably, our findings that an SLA admix archaeosome formulation functions similarly to an entrapped antigen archaeosome formulation are not out of place in the current vaccine adjuvant landscape as many other adjuvants, such as CpG or Poly (I:C), are capable of initiating CD8 + T cell responses towards exogenous antigen [10].…”

“…In multiple pre-clinical studies, they have been shown to activate antigen-specific CD8 + T cell responses [15,19,26,27] and generate protective immunity in tumor models, e.g., B16-OVA melanoma [7,13,19,23,26,27], and against multiple infectious diseases, e.g., H1N1 influenza [11], Listeria monocytogenes [7,12], Trypanosoma cruzi [13] and Mycobacterium tuberculosis [14]. When compared to commonly used commercial adjuvants, such as Poly(I:C) or Montanide, archaeal lipid vaccines were found to elicit equal or greater antigen specific CD8 + T cell-mediated cytotoxicity and IgG responses [10]. SLA-based archaeosomes can also induce local cytokine production at the site of injection even in the absence of an antigen [19].…”

“…MS-OVA archaeosomes have been previously used to deliver entrapped antigen and induce anti-tumor CD8 + T cell responses [10,15,16,27]. Using the solid B16-OVA melanoma tumor model, we have previously demonstrated a synergy between MS-OVA (enc) and CPI therapy (anti-PD-1, anti-programmed death-ligand 1 (anti-PD-L1) and anti-CTLA-4) in promoting long-term tumor-free survival in C57BL/6 mice [15].…”

“…Archaeosomes have been consistently proven to be a versatile adjuvant capable of inducing potent immunity in a number of animal models of disease. To date, archaeosomes have been used with multiple antigens, including listeriolysin (LLO), tyrosinase-related-protein-2 (Trp2), glycoprotein-100 (Gp100), Hepatitis-B surface antigen (HBsAg), influenza haemagglutinin (HA) and Hepatitis-C virus E1E2 heterodimer (HCV E1E2) [7][8][9][10][11][12], inducing both strong antibody responses as well as potent cellular responses that afford protection against infections and/or tumor challenge in murine models [7,8,[12][13][14][15]. Archaeosomes are lipid vesicles composed of glycerolipids derived from archaea.…”

“…Although traditionally formulated archaeosome vaccines are capable of efficient delivery of antigen and inducing strong humoral and cell-mediated immune responses, there are certain drawbacks associated with using TPL formulations, including difficulty in maintaining batch-to-batch consistency in the proportions of lipid species that are naturally expressed by growing archaea and a low antigen entrapment efficiency (typically 5-40%), resulting in increased production costs and variability in the finalized formulation. To overcome these difficulties, we have developed a simplified archaeosome lipid formulation using a single glycolipid composed of a sulfated saccharide group covalently linked to the free sn-1 hydroxyl backbone of an archaeal core lipid (sulfated lactosyl archaeol, SLA), which when simply admixed with soluble antigen prior to immunization could induce comparable humoral and cellular immune responses to those induced by the traditional method of entrapping antigen within the archaeosome vesicle [10,18,19]. Advantages to this formulation include consistency of production, reduced costs and ease of synthesis while still retaining a similar level of adjuvanticity, as observed with conventional archaeosomes.…”