| Type |
Adjuvant |
Description |
| Mineral salts |
Aluminum
phosphate |
Aluminum phosphate adjuvants have been used for more than half a century and have been used to induce early, high-titer, durable immunity. An H. pylori vaccine study by Suganya et al. (2017) showed that aluminum phosphate adjuvants can induce high IgG titer levels immediately and achieve long-term protective immunity by slowing the rate of antigen presentation in the immune system of animal models. |
Aluminum
hydroxide |
Aluminum hydroxide adjuvants have a repository effect that ensures high antigen concentrations and enhances the uptake of antigen by antigen-presenting cells (APCs), thereby further enhancing the immune response. Aluminum hydroxide adjuvants also have a pro-phagocytic effect on macrophages, enhancing the immune response against antigens. |
| Liposomes |
Polymerized
liposomes |
Liposomes can be used as effective delivery adjuvants for mucosal vaccines due to their easier endocytosis by antigen presenting cells (APCs). Among them, polymeric liposomes exhibit greater stability in the gastrointestinal tract and can be used in oral vaccines against H. pylori. |
| Oil adjuvants |
Freund's
adjuvant |
The most widely used oil-water emulsion adjuvants in animal experiments are Freund's adjuvants, including incomplete Freund's adjuvant (IFA) and complete Freund's adjuvant (CFA) adjuvants. The addition of killed Mycobacterium tuberculosis to CFA makes it unsuitable for use in humans due to its toxicity and secondary reactions. In contrast, IFA is less toxic and suitable for use in clinical settings. |
| Microbial derivatives |
LT
(R192G/L211A) |
A double mutant heat-labile toxin (dmLT) or LT(R192G/L211A), is an 84 kDa polymeric protein with an AB5 structure that promotes Th17 polarization and enhances prophylactic protection against H. pylori infection when used as an oral immune adjuvant for vaccines. |
| Multiple mutant cholera toxin |
Due to the strong enterotoxicity of cholera toxin, cholera toxin cannot be used for human immunization, and the non-toxic adjuvant multiple mutant cholera toxin (mmCT) can be used as an alternative adjuvant without loss of protective effect. It can strongly promote important protective immune responses against H. pylori infection, such as the Th17 and Th1 responses. |
| Chitosan |
Chitosan can be a good delivery adjuvant as it can be modified with chemical and/or biological molecules and transformed into a variety of formulations with a wide range of particle sizes. More importantly, oral H. pylori vaccines using chitosan have shown greater or similar immunotherapeutic effects in terms of H. pylori elimination rate, humoral immune response, and Th1/Th2 cellular immune response in mice compared to vaccines using cholera toxin. |
| CpG oligodeoxynucleotides |
By mimicking bacterial DNA, CpG oligodeoxynucleotides (CpG ODN) can stimulate a variety of mammalian immune cells including humans, and improve the efficacy of vaccines against infectious diseases and cancer. In a study by Ghasemi et al. (2018), CpG ODN was shown to trigger a complex Th1/Th2/Th17 response and protect against H. pylori infection. |
| α-galactosylceramide |
α-galactosylceramide (α-GalCer) forms a complex with the lipid antigen-presenting molecule CD1d, and this complex then leads to strong activation of invariant natural killer T (iNKT) cells, resulting in high levels of cytokine production and a selectively enhanced antigen-specific Th1 response to H. pylori infection in mice. |
| Plant polysaccharides |
Astragalus
polysaccharide |
Astragalus polysaccharide (APS), when combined with recombinant UreB (rUreB, urease subunit B), stimulates a mixed specific Th1 and Th17 immune response, thus enhancing immune protection against H. pylori. |
