Structural elements of a protein antigen determine immunogenicity of the embedded MHC class I-restricted T cell epitope

Comparison of chitosan nanoparticles and chitosan hydrogels for vaccine delivery

In this work the potential of chitosan nanoparticles (CNP) and thermosensitive chitosan hydrogels as particulate and sustained release vaccine delivery systems was investigated. CNP and chitosan hydrogels were prepared, loaded with the model protein antigen ovalbumin (OVA) and characterised. The immunostimulatory capacity of these vaccine delivery systems was assessed in-vitro and in-vivo. Particle sizing measurements and SEM images showed that optimised OVA-loaded CNP had a size of approximately 200 nm, a polydispersity index < 0.2, and a positive zeta-potential of approximately 18 mV. The amount of OVA adsorbed onto CNP was high with an adsorption efficacy of greater than 96%. Raman spectroscopy indicated conformational changes of OVA when adsorbed onto the surface of CNP. Uptake of the dispersions and immunological activation of murine dendritic cells in-vitro could be demonstrated. Investigation of the release of fluorescently-labelled OVA (FITC-OVA) from CNP and chitosan hydrogels in-vitro showed that approximately 50% of the total protein was released from CNP within a period of ten days; release of antigen from chitosan gel occurred in a more sustained manner, with < 10% of total protein being released after 10 days. The slow release from gel formulations may be explained by the strong interactions of the protein with chitosan. While OVA-loaded CNP showed no significant immunogenicity, formulations of OVA in chitosan gel were able to stimulate both cell-mediated and humoral immunity in-vivo.

Immune shaping and the development of Alzheimer's disease vaccines

Given the emotional, social, and financial devastation wrought by Alzheimer's disease (AD), it is imperative that effective therapeutics be devised to ameliorate this presently incurable disorder. Vaccine-based approaches have been developed to target and eliminate amyloid beta (Abeta), a key peptide implicated in AD pathogenesis. Preclinical successes in AD mouse models created excitement and impetus for the clinical application of an Abeta-based vaccine. Eliciting immune responses against a self-peptide (that is, a peptide produced by the organism itself), such as Abeta, carries with it the potential to induce autoimmune and inflammatory conditions in the vaccinated individual, a caveat borne out in multiple patients enrolled as part of a recent clinical trial. These clinical adverse events seemingly overshadowed interesting behavioral stabilization and alterations of Abeta burden in these and other vaccinated patients, thus speaking to the potential of immunotherapy for AD. Understanding the mechanisms by which vaccines reduce Abeta burden in AD brain and the types of immune responses raised, as well as developing new modalities of vaccine delivery that facilitate the modulation of elicited immune responses, will undoubtedly lead to a new generation of efficacious Abeta immunotherapeutics with improved safety profiles.

In vivo plasmid DNA electroporation generates exceptionally high levels of epitope-specific CD8+ T-cell responses

Based on observations that DBA/2 mice develop a highly specific response towards an HLA-Cw3-derived epitope, consisting entirely of CD8+CD62L-Vbeta10+ cells, we have established an in vivo mouse model for screening a variety of immunization approaches. Responder cells were readily detectable in small samples of the peripheral blood using three-color FACS analysis. This permitted multiple, sequential determination of CD8+ T-cell responses in living animals at a very high degree of precision. In vivo electroporation delivery of expression construct plasmids, outclassed the other approaches tested. Dominant, specific responses were induced already upon a single administration. Both the peak and the longevity of the response resembled those that are generated by the most active viral infections. The induced CTLs rejected epitope-bearing tumor cells in vivo and released interferon-gamma upon stimulation with the correct MHC::peptide combination in vitro. The potent in vivo response was not influenced by known modulators of the innate immune system, such as CpG DNA and LPS content. In vivo electroporation thus deserves consideration in the future in antitumor and antiviral immunization approaches, where CD8+ T cells play a predominant role.