Hsp70 enhances presentation of FMDV antigen to bovine CD4+ T cells in vitro

Endotoxin-minimized HIV-1 p24 fused to murine hsp70 activates dendritic cells, facilitates endocytosis and p24-specific Th1 response in mice

Heat shock proteins hsp70 and gp96 have been confirmed as adjuvants enabling induction of cell- and antibody-mediated immunity specific to associated protein or peptide antigens due to the activation of naive dendritic cells and supporting cross-presentation of associated antigen. An efficacious vaccine preventing HIV-1 infection should induce (1) antibodies neutralizing HIV-1 Env protein, preventing virus spreading and (2) CD4(+) Th1 and CD8(+) T cells specific to viral proteins, especially gag p24, important for elimination of HIV-1 infected cells. As p24 is relatively poorly recognized by dendritic cells, its targeting to DC is important for enhancement of vaccine efficacy. In this study, a p24 protein fused to the C- or N-terminus of murine hsp70 was produced as a recombinant protein and administered without any adjuvant to experimental BALB/c mice. Consequently, p24-specific cellular and humoral immune responses were measured. To minimize the effect of bacterial endotoxin, each protein was subjected to a repeated endotoxin phase extraction until each preparation contained less than 2.5 endotoxin unit (EU) per mg of antigen. In addition, endocytosis of p24 fused to hsp70 by dendritic cells and their activation were characterized. The fusion to hsp70 protein enhanced endocytosis of p24 as well as activation of dendritic cells in vitro. After immunization of mice, hsp70-p24 fusion protein induced the strongest p24-specific CD4(+) and CD8(+) T cells (IFN-γ production) and humoral (IgG2b) responses corresponding to Th1 type dominance, whereas p24-hsp70 or p24 itself induced weaker responses.

CD91-Dependent Modulation of Immune Responses by Heat Shock Proteins: A Role in Autoimmunity

Heat shock proteins (HSPs) have been known for decades for their ability to protect cells under stressful conditions. In the 1980s a new role was ascribed for several HSPs given their ability to elicit specific immune responses in the setting of cancer and infectious disease. These immune responses have primarily been harnessed for the immunotherapy of cancer in the clinical setting. However, because of the ability of HSPs to prime diverse immune responses, they have also been used for modulation of immune responses during autoimmunity. The apparent dichotomy of immune responses elicited by HSPs is discussed here on a molecular and cellular level. The potential clinical application of HSP-mediated immune responses for therapy of autoimmune diseases is reviewed.

Hsp110-mediated enhancement of CD4+ T cell responses to the envelope glycoprotein of members of the family Flaviviridae in vitro does not occur in vivo

The use of heat shock proteins (HSP) to enhance activation of the immune response to chaperoned antigen is being explored for immunotherapy. Hsp110 chaperones large protein substrates more effectively than Hsp70, offering the potential to use complex antigens containing multiple epitopes in HSP-based vaccines. In this study, we investigated the ability of recombinant bovine Hsp110 to chaperone E2 glycoprotein, the major envelope protein of bovine viral diarrhea virus (BVDV) and the dominant target of neutralizing antibodies. Hsp110 formed complexes with E2, as demonstrated by immunoprecipitation. When monocytes from BVDV-immunized cattle were stimulated with these complexes and incubated with autologous CD4(+) T cells, enhanced levels of proliferation were observed. To determine the ability of these complexes to improve immunogenicity in vivo, cattle were vaccinated with either Hsp110-E2 complex or E2 only, combined with Quil-A adjuvant. In contrast to the in vitro data, cellular and humoral responses to E2 were greater in the E2-only vaccination group, indicating that complex formation had actually reduced the immunogenicity of E2. This study highlights the need for further understanding of the means by which HSP complexes are endocytosed and processed in vivo to enable the design of successful vaccine strategies.