Safety and biodistribution of sulfated archaeal glycolipid archaeosomes as vaccine adjuvants

Abstract

Archaeosomes are liposomes comprised of ether lipids derived from various archaea. Unlike conventional ester-linked liposomes, archaeosomes exhibit high pH and thermal stability. As adjuvants, archaeosomes can induce robust, long-lasting humoral and cell-mediated immune responses and enhance protection in murine models of infectious disease and cancer. Archaeosomes constituted with total polar lipids (TPL) of various archaea are relatively complex, comprising >10 different lipid compounds. Archaeosomes can be constituted with semi-synthetic glycerolipids built on ether-linked isoprenoid phytanyl cores with varied synthetic glycol- and amino-head groups. However, such 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 saccharide group covalently linked to the free sn-1 hydroxyl backbone of an archaeal core lipid (sulfated S-lactosylarchaeol, SLA) mixed with uncharged glycolipid (lactosylarchaeol, LA). This new class of adjuvants can be easily synthesized and retains strong immunostimulatory activity for induction of cell-mediated immunity following systemic immunization. Herein, we demonstrate the safety of SLA/LA archaeosomes following intramuscular injection to mice and evaluate the immunogenicity, in vivo distribution and cellular uptake of antigen (ovalbumin) encapsulated into SLA/LA archaeosomes. Overall, we have found that semi-synthetic sulfated glycolipid archaeosomes are a safe and effective novel class of adjuvants capable of inducing strong antigen-specific immune responses in mice and protection against subsequent B16 melanoma tumor challenge. A key step in their mechanism of action appears to be the recruitment of immune cells to the injection site and the subsequent trafficking of antigen to local draining lymph nodes.

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

“…Archaeal lipid adjuvants are a good potential candidate for use in combination with CPI's, as evidenced by their proven safety and efficacy in mice [19,44]. 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].…”

“…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]. While cytokine production was not measured in this study, the use of empty SLA archaeosomes combined with anti-PD-1 and anti-CTLA-4 therapy (without OVA antigen) did not cause any increase in median survival compared to anti-PD-1 and anti-CTLA-4 alone (22.5 vs. 27 days, respectively).…”

“…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.…”

Effect of Different Adjuvants on the Longevity and Strength of Humoral and Cellular Immune Responses to the HCV Envelope Glycoproteins

“…Traditional archaeosomal formulations consisted of liposomes formed from total polar lipids (TPL) derived from archaea such as the methanogen Methanobrevibacter smithii (MS). These archaeosomes were shown to effectively activate professional antigen-presenting cells [14][15][16] and generate robust cellular and humoral immune response to encapsulated antigen in both cancer and infectious disease models [11,12,17]. More recently, a novel simpler semi-synthetic archaeosome formulation composed of a sulfated disaccharide group covalently linked to the free sn-1 hydroxyl backbone of an archaeal core lipid (sulfated S-lactosylarchaeol, SLA), has been developed [18].…”

“…More recently, a novel simpler semi-synthetic archaeosome formulation composed of a sulfated disaccharide group covalently linked to the free sn-1 hydroxyl backbone of an archaeal core lipid (sulfated S-lactosylarchaeol, SLA), has been developed [18]. Archaeosomes formed with SLA alone or in combination with lactosylarchaeol (LA) retain a similar level of adjuvanticity to MS TPL archaeosomes, but consist of a simpler formulation with many advantages including consistency of production, reduced costs, and ease of synthesis [10,14,19]. A recent comparison of SLA to a wide panel of commercial adjuvants (e.g., aluminum salts, TLR agonists, and water/oil emulsions) when paired with the model antigens ovalbumin and HBsAg demonstrated that SLA archaeosome formulations had robust adjuvant activity that was superior to many of the other tested adjuvants [10].…”