In Vivo Cytotoxic T Lymphocyte Elicitation by Mycobacterial Heat Shock Protein 70 Fusion Proteins Maps to a Discrete Domain and Is Cd4+ T Cell Independent

Abstract

To gain insights into the mechanisms by which soluble heat shock protein (hsp) fusions can elicit CD8+ cytotoxic T lymphocytes (CTLs) against the fusion partner, mycobacterial (Mycobacterium tuberculosis) hsp70 was dissected to ascertain whether a particular hsp domain is necessary, and knockout mice were used to determine whether the fusion protein's immunogenicity is dependent on CD4+ T lymphocytes. We found that the ability to elicit CD8+ CTLs depends on a discrete 200–amino acid protein domain, indicating that the fusion protein's immunogenicity for CD8+ T cells does not require coupled chaperone function or peptide binding. Further, we found that ovalbumin (OVA).hsp70 fusion protein elicited anti-OVA CD8+ CTLs about equally well in CD4 knockout and wild-type C57BL/6 mice, and also when the hsp70 was of murine (self) origin. The ability of hsp70 fusion proteins to elicit CD4-independent CTL responses suggests that hsp70 fusion proteins may be useful for immunological prophylaxis and therapy against disease in CD4+ T cell–deficient individuals.

Secretory heat-shock protein as a dendritic cell-targeting molecule: a new strategy to enhance the potency of genetic vaccines

“…These findings are consistent with data in earlier reports of recombinant HSP70 fusion proteins that included HIV-1 p24, 36 OVA, 37,39 influenza virus NP, 45 or HPV16 E7 38 as model antigens or E7/HSP70 fusion proteins released from dying cells. 46,47 However, it remains a mystery why the HSP-mediated presentation of E7 antigens did not induce CD4 þ T-helper responses, presumably through the receptor-mediated class II antigen presentation pathway.…”

“…Although we cannot entirely rule out a CD4 þ response against the human E7 in this mouse model, a recent study also reported a CD4 þ independent CD8 þ T-cell response in mice immunized with recombinant mycobacterial or murine HSP70 fusion proteins. 39 Vaccination with pCMV-Sig/E7/HSP70 induces an E7-specific antibody response…”

“…Finally, recombinant HSP-antigen fusion proteins 36,37 were able to elicit CD4 þ -independent CD8 þ cytotoxic T-lymphocyte (CTL) responses. [38][39][40] In the present study, we sought to enhance the potency of DNA vaccines by using HSP70 as a DC-targeting molecule to enhance antigen cross-presentation and DC maturation. This novel strategy (Figure 1a) uses the human papilloma virus type-16 E7 oncoprotein (HPV16 E7) as a model antigen and HSP70 as a DC binding domain.…”

Immunotherapy of Epstein-Barr Virus Associated Malignancies Using Mycobacterial HSP70 and LMP2A356–364 Epitope Fusion Protein

“…However, among EBV latent-cycle proteins, CD4 + T responses to LMP2A epitopes are much less frequent than EBNA1 and LMP1 (18). Previous studies have demonstrated that MtHsp70 accompanied antigens can induce potential antigen-specific CD8 + T cells with cytolytic and cytokine-secreting functions through CD4 + T cell independent modes (21,23,(39)(40)(41)(42). In this study, we conjugated a conserved LMP2A HLA-A2.1 restricted epitope LMP2A 356-364 to MtHsp70, which not only induces LMP2A 356-364 specific immune recognition in vitro, but also elicits LMP2A specific CTL in vivo.…”

“…Previous studies indicate that MtHsp70 can be used as an adjuvant-free carrier to stimulate the humoral and cellular immune response to accompanied proteins or synthetic peptides (20,21). Many studies have demonstrated that MtHsp70 accompanied antigens are able to induce potential antigen-specific CD8 + T cells with cytolytic and cytokine-secreting functions through CD4 + T cell independent mode (22,23).…”