[81] Heat-shock proteins possess broad utility as vaccine components. For example, marketed adjuvants often possess side-effects (e.g. ulceration); hsp adjuvants

avoid such effects. The abilities of hsp to drive innate stimulation and deliver antigens are now being exploited in prophylactic vaccines against infectious diseases. In one approach, hsp-based vaccines have check details been produced by over-expressing the influenza virus nucleoprotein in cultured cells before purification of gp96.[84] The gp96 preparation was well tolerated in mice; with preliminary results suggesting that a cellular immune response was induced, providing a novel strategy to develop vaccines against virus targets.[84] There are several published approaches to prepare hsp complexes, including ion exchange and hydroxyapatite column chromatography and immunoprecipitation with antibodies coupled to magnetic beads.[85] In an innovative approach, hsp70C have

been extracted from plant cells expressing viral antigens[86, 87] using the same ADP-chromatography purification protocol described for animal hsp70,[88] a method able to prevent the release of the naturally chaperoned peptides. Plant-derived hsp70C were shown to activate the immune system inducing both activation of MHC class I-restricted polyclonal T-cell responses and antibody production in mice of different haplotypes without the need of adjuvant co-delivery.[87] These results indicate that hsp70C derived from plants producing recombinant antigens may be used to formulate multi-epitope vaccines. Several investigational prophylactic vaccines containing Monoiodotyrosine hsp and hsp complex are in development. For example, a tuberculosis vaccine based on hsp complex from SB203580 BCG (T-BioVax) has demonstrated good efficacy in the mouse Mycobacterium tuberculosis aerosol challenge model.[89, 90] ImmunoBiology Ltd is also developing a vaccine against meningitis (MenBioVax) derived from heat-shocked

Neisseria meningitidis. Both T-BioVax and MenBioVax contain multiple hsp families derived from the stressed bacterium of interest to maximize efficacy. MenBioVax provides protection against lethal challenge in a mouse model of meningococcal septicaemia. Sera obtained from mice immunized with this vaccine show promising bactericidal and opsonophagocytic responses against a panel of N. meningitidis strains.[91] HerpV, a vaccine consisting of 32 synthetic 35mer HSV-2 peptides representative of all phases of viral replication, non-covalently complexed with recombinant human hsp70 protein, is well tolerated and safe.[92] This was the first hsp-based vaccine to show immune responses against viral antigens in humans.[92] Vaccinated subjects demonstrated a statistically significant CD4+ T-cell response to HSV-2 antigens, with the majority of subjects also having a significant CD8+ T-cell response. Development of hsp vaccines is based on the need to emulate safely, the mechanism by which protection is established during a normal infection.