A new intranasal influenza vaccine based on a novel polycationic lipid-ceramide carbamoyl-spermine (CCS). II. Studies in mice and ferrets and mechanism of adjuvanticity.

We recently showed that lipid assemblies comprised of a novel polycationic sphingolipid (ceramide carbamoyl-spermine, CCS) are an effective adjuvant/carrier when complexed with cholesterol (CCS/C) for influenza and other vaccines administered parenterally and intranasally (i.n.) in mice. Here we expand these studies to ferrets, an established model of influenza infection. We also address the question of why the CCS/C-based liposomal vaccine (also known as VaxiSome™) in mice is superior to vaccines based on liposomes of other lipid compositions (neutral, anionic or cationic). Ferrets immunized i.n. with CCS/C-influenza vaccine produced significantly higher hemagglutination inhibition (HI) antibody titers compared to ferrets immunized intramuscularly with the unadjuvanted influenza vaccine, indicating that the CCS/C-based vaccine is very immunogenic. Furthermore, the i.n. adjuvanted vaccine was shown to significantly reduce the severity of influenza virus infection in ferrets following homologous viral challenge as determined by weight loss, temperature rise and viral titer. No adverse reactions were observed. Pharmacokinetic and biodistribution studies following i.n. administration in mice of CCS/C-based vaccine showed that both the lipids and antigens are retained in the nose and lung for at least 24h, and it appears that this retention correlates with the superior immunogenicity elicited by the adjuvanted vaccine formulation. The CCS lipid also increases production of cytokines (mainly IFN gamma, IL-2 and IL-12) and co-stimulatory molecules' expression, which might further explain the robust adjuvantation of this liposome-based vaccine.

A new intranasal influenza vaccine based on a novel polycationic lipid--ceramide carbamoyl-spermine (CCS) I. Immunogenicity and efficacy studies in mice.

Although most pathogens use the mucosal routes for invasion, the majority of currently available vaccines are administered parenterally. Injectable vaccines induce good systemic immunity but often unsatisfactory mucosal immunity. A non-injectable mucosal vaccine, which can be self-administered intranasally, may provide both effective systemic and mucosal immunity and can be used for vaccination of large populations within a short period of time in case of a sudden epidemic. Here, we report on a new intranasal (i.n.) influenza vaccine, based on a novel polycationic sphingolipid, N-palmitoyl D-erythro-sphingosyl carbamoyl-spermine (ceramide carbamoyl-spermine = CCS), having combined carrier and adjuvant activities, which elicits, in mice, strong systemic (serum) and local (lung and nasal) humoral and cellular responses, and provides protective immunity. In a comparative study, we show that both unmodified commercial vaccine and vaccine formulated with neutral or anionic liposomes were poorly immunogenic upon i.n. administration. Of five vaccine formulations based on well-established monocationic lipids in the form of unsized liposomes, three (DC-Chol, DDAB, and DSTAP-based) resulted in low serum and local responses, while two others (DMTAP and DOTAP-based vaccines) induced both systemic and local vigorous Th1+Th2 immune responses. However, only the vaccine formulated with CCS was equivalent or superior to the commercial vaccine co-administered with cholera toxin as an adjuvant. Furthermore, the CCS-based influenza vaccine was highly efficacious following a single or a repeated (x2) i.n. or a single i.m. administration, without an added adjuvant, in both young (2 months) and old (18 months) mice. It elicited high titers of strain cross-reactive hemagglutination inhibition (HI) antibodies, and the high antibody titers and protective immunity persisted for at least 9 months. No systemic adverse effects, and only a mild local inflammatory response, were observed in mice and rabbits vaccinated i.n. with the CCS vaccine formulation. A similar approach may prove efficacious for i.n. vaccination against other pathogens.