Structural Characterization of Archaeal Lipid Mucosal Vaccine Adjuvant and Delivery (AMVAD) Formulations Prepared by Different Protocols and Their Efficacy Upon Intranasal Immunization of Mice

Abstract

Intranasal administration of ovalbumin (OVA) formulated in an archaeal lipid mucosal vaccine adjuvant and delivery (AMVAD) system prepared by the addition of CaCl2 to small unilamellar archaeosomes (liposomes made from archaeal polar lipids) containing encapsulated OVA, was recently shown to elicit strong and sustained OVA-specific mucosal and systemic immune responses. In this study, we show that the centrifugation/washing and antigen quantization steps required in the standard protocol for obtaining OVA/AMVAD model vaccine formulations can be eliminated by using simpler protocols such as admixing OVA with preformed empty archaeosomes, or by changing the starting ratio (w/w) of archaeal lipid to antigen at the archaeosome preparation stage, prior to the addition of CaCl2 to convert to the AMVAD structures. Irrespective of the vaccine preparation protocol, the AMVAD particle typically comprised of larger spherical structures that had aggregated like a bunch of grapes, and it contained aqueous compartment(s). The anti-OVA IgA antibody responses in vaginal wash, nasal wash, serum, and bile samples, and the anti-OVA IgG antibody responses in sera, in mice intranasally immunized with the OVA/AMVAD formulations prepared by the simplified or the standard protocols, were comparable.