Induction of Cytotoxic T-Lymphocyte Responses Upon Subcutaneous Administration of a Subunit Vaccine Adjuvanted With an Emulsion Containing the Toll-Like Receptor 3 Ligand Poly(I:C)

Abstract

There is an unmet medical need for new subunit vaccines that induce cytotoxic T-lymphocyte (CTL) responses to prevent infection with a number of pathogens. However, stimulation of CTL responses via clinically acceptable subcutaneous (s.c.) and intramuscular (i.m.) injection is challenging. Recently, we designed a liposomal adjuvant [cationic adjuvant formulation (CAF)09] composed of the cationic lipid dimethyldioctadecylammonium (DDA) bromide, a synthetic monomycoloyl glycerol analog and polyinosinic:polycytidylic acid, which induce strong CTL responses to peptide and protein antigens after intraperitoneal administration. By contrast, CAF09 does not stimulate CTL responses upon s.c. or i.m. injection because the vaccine forms a depot that remains at the injection site. Hence, we engineered a series of nanoemulsions (CAF24a–c) based on the active components of CAF09. The oil phase consisted of biodegradable squalane, and the surface charge was varied systematically by replacing DDA with zwitterionic distearoylphosphoethanolamine. We hypothesized that the nanoemulsions drain to the lymph nodes to a larger extent than CAF09, upon s.c. co-administration with the model antigen chicken egg ovalbumin (OVA). This results in an increased dose fraction that reaches the draining lymph nodes (dLNs) and subsequently activates cross-presenting dendritic cells (DCs), which can prime CTL responses. Indeed, the nanoemulsions induced antigen-specific CD8+ T-cell responses, which were significantly higher than those stimulated by OVA adjuvanted with CAF09. We explain this by the observed rapid localization of CAF24a in the dLNs and the subsequent association with conventional DCs, which promotes induction of CTL responses. Uptake of CAF24a was not specific for DCs, because CAF24a was also detected with B cells and macrophages. No measurable dose fraction of CAF09 was detected in the dLNs within the study period, and CAF09 formed a depot at the site of injection. Importantly, s.c. vaccination with OVA adjuvanted with CAF24a induced significant levels of specific lysis of antigen-pulsed splenocytes were induced after, which was not observed for OVA adjuvanted with CAF09. Thus, CAF24a is a promising adjuvant for induction of CTL responses upon s.c. and i.m. immunization, and it offers interesting perspectives for the design of vaccines against pathogens for which CTL responses are required to prevent infection.

Cross-Protective Potential and Protection-Relevant Immune Mechanisms of Whole Inactivated Influenza Virus Vaccines Are Determined by Adjuvants and Route of Immunization

“…The liposomal adjuvants CAF01 and CAF09 were produced as described previously (42). The dose for both adjuvants was 300 μg per 50 μl for i.m.…”

In silico designing of vaccine candidate against Clostridium difficile

“…Intramuscular administration (I.M) is preferred for the delivery of the vaccine candidate since it is easy to perform and well tolerated, with a low risk for adverse reactions at the site of injection and is the most commonly used route for licensed vaccines 107 . Recent studies also show that intramuscular immunization is a promising strategy for induction of strong systemic CTL response 108 . In addition, CDC recommends that vaccines containing an adjuvant should be injected into a muscle rather than any other routes since they can cause local irritation, induration, skin discolouration, inflammation, and granuloma formation 109 , 110 .…”

Vaccine Adjuvant Delivery Systems Constructed Using Biocompatible Nanoparticles Formed through Self-Assembly of Small Molecules

“…Meanwhile, attempts in pushing into clinical trials of emulsion VADSs for delivery of cancer vaccines and other applications have also increasingly continued and are accompanied by endeavors in shedding light on the mechanisms involved in the action of emulsion adjuvants. Recently, Schmidt et al using squalane as an O and distearoylphosphoethanolamine (DSPE) as an emulsifier engineered the TLR3a poly(I:C)-entrapping cationic nanoemulsions with a size of 200 nm and demonstrated that when given to mice the cationic nanoemulsions drained rapidly to the LNs and activated cross-presenting DCs, MPs as well as B cells, resulting in strong Ag-specific CD8+ T-cell responses [35]. The results suggest the squalane-based cationic nanoemulsions may be a promising VADS with the ability to induce strong CTL responses, offering an alternative way to make vaccines against pathogens that can hardly be protected without activated CTLs.…”