Liposomal Meningococcal B Vaccination: Role of Dendritic Cell Targeting in the Development of a Protective Immune Response

Abstract

The effect of targeting strategies for improving the interaction of liposomal PorA with dendritic cells (DC) on the immunogenicity of PorA was investigated. PorA, a major antigen of Neisseria meningitidis, was purified and reconstituted in different types of (targeted) liposomes, i.e., by using mannose or phosphatidylserine as targeting moieties, or with positively charged liposomes. We studied the efficiency of liposome uptake and its effect on the maturation of and interleukin 12 (IL-12) production by murine DC. Moreover, mice were immunized subcutaneously to study the localization and immunogenicity of PorA liposomes. Uptake of liposomes by DC was significantly increased for targeted liposomes and resulted in the maturation of DC, but to various degrees. Maturation markers (i.e., CD80, CD86, major histocompatibility complex class II, and CD40) showed enhanced expression on DC incubated with targeted PorA liposomes relative to those incubated with nontargeted PorA liposomes. Moreover, only the uptake of targeted PorA liposomes induced production of IL-12 by DC, with levels similar to those produced by lipopolysaccharide (LPS)-pulsed DC. Mannose-targeted PorA liposomes administered subcutaneously had an increased localization in draining lymph nodes compared to nontargeted PorA liposomes. Liposomes in draining lymph nodes interacted preferentially with antigen-presenting cells, an effect that was enhanced with targeted PorA liposomes. Immunization studies showed an improvement of the bactericidal antibody response (i.e., increased number of responders) generated by targeted PorA liposomes compared to that generated by nontargeted ones or LPS-containing outer membrane vesicles. In conclusion, the use of targeted PorA liposomes results in an improved uptake by and activation of DC and an increased localization in draining lymph nodes. These effects correlate with an enhanced immune response toward the vaccine.

A Model Vaccine Exploiting Fungal Mannosylation to Increase Antigen Immunogenicity

“…In contrast, mice immunized with mucin 1 conjugated to oxidized mannan induced CTL responses and tumor protection (8,(22)(23)(24)(25). Furthermore, mannan-coated liposomes containing DNA or protein have been shown to elicit CTL responses and hallmarks of Th1-mediated immunity, such as delayed-type hypersensitivity responses and the secretion of cytokines (IL-12 and IFN-␥) (4,5,9,26,27). These studies incorporate the conjugation of mannose or mannan onto Ags, but did not examine the potential benefits of differential mannosylation using a system (e.g., fungi) that naturally mannosylates its glycoproteins.…”

“…However, vaccine-mediated protection against many tumors and infections is thought to require the induction of T cell-mediated immunity (1,2). Mannosylation of Ags has been reported to enhance MHC class I-and MHC class II-restricted Ag presentation and T cell stimulation by up to 200-fold compared with nonmannosylated proteins (3)(4)(5)(6)(7). Furthermore, in vivo induction of Th1 cytokines and Ag-specific CTL responses were observed in mice upon immunization with mannosylated vaccines (6,8,9).…”

Immunological Risk of Injectable Drug Delivery Systems

“…Multiple epitope arrays clustered at the surface of DDS form a particular risk factor for immunogenicity and should be avoided if possible. Ligands such as mannose that are recognized by APCs should especially be avoided, except for vaccination purposes (63,131), although data showing enhanced immune responses when used therapeutically are lacking. The particulate character of many DDS makes them prone to be recognized as foreign by immune cells and the complement system.…”

Cloning, expression and purification of outer membrane protein PorA of Neisseria meningitidis serogroup B

“…Much of this evidence comes from the clinical evaluation of OMV vaccines in which PorA is the immunodominant antigen [13]. Recombinant OMV-formulations with various PorA antigens have been developed in some countries; therefore, it can be considered a reliable candidate antigen as a part of a multi-component recombinant protein vaccine [14]. The aim of the present study was to construct a prokaryotic highlevel expression system for producing recombinant outer membrane protein PorA which can be used for vaccine development in the future.…”