Archaeosomes are liposomes manufactured utilising archaea-derived total polar lipids (TPLs). Traditional antigen-encrusted archaeosomes reveal robust adjuvant efficacy in different mouse and cancer models by increasing antigen-specific humoral and cell-mediated responses, and boosted protective immunity. However, the efficacy of the antigen trap may vary considerably, leading to antigen loss during formulation and varying antigen: lipid ratios. In order to overcome this, an admixtured archaeosome formula was recently devised consisting of one semi-synthetic archaeal lipid (SLA), which might cause an equally strong adjuvant activity as an encapsulated formula. In this context the mechanisms involved in induce both admixed SLA (adm), encapsulated (Enc) and admixtured archaeosomes in the initial innate and antigen specific responses are evaluated and compared.
The study shows that both archaeosome formulations lead to increased immune cell infiltration, improved retention at the injection site and increased uptake of antigen by antigen-presenting cells and other types of immune cells including intramuscular injection neutrophils and monocytes in mice using the model antigen, ovalbumin. Although the encapsulated formulation could better generate antigen-specific CD8+ T dendritic cell activation in vitro, both encapsulated and admixed formulations gained tumor-specific protection using a B16-OVA melanoma in vivo test. Despite certain changes in the immunostimulatory profile with regard to SLA formulation (enc), SLA (Adm), while providing ease of formulation, causes substantial in vivo immunogenicity and effectiveness.