Safety and immunogenicity of long HSV-2 peptides complexed with rhHsc70 in HSV-2 seropositive persons.

HSV-2, the primary causative agent of genital herpes, establishes latency in sensory ganglia and reactivates causing recurrent lesions and viral shedding. Induction or expansion of CD4(+) and CD8(+) T cell responses are expected to be important for a successful therapeutic vaccine against HSV-2. A candidate vaccine consisting of 32 synthetic 35mer HSV-2 peptides non-covalently complexed with recombinant human Hsc70 protein (named HerpV, formerly AG-707) was tested for safety and immunogenicity in a Phase I study. These peptides are derived from 22 HSV-2 proteins representative of all phases of viral replication. Thirty-five HSV-2 infected participants were randomized and treated in one of four groups: HerpV+QS-21 (saponin adjuvant), HerpV, QS-21, or vehicle. The vaccine was well tolerated and safe. All seven participants with evaluable samples who were administered HerpV with QS-21 demonstrated a statistically significant CD4(+) T cell response to HSV-2 antigens, and the majority of such participants demonstrated a statistically significant CD8(+) T cell response as well. To our knowledge, this is the first candidate vaccine against HSV-2 to demonstrate a broad CD4(+) and CD8(+) T cell response in HSV-2(+) participants, and the first HSP-based vaccine to show immune responses against viral antigens in humans.

A heat shock protein based polyvalent vaccine targeting HSV-2: CD4(+) and CD8(+) cellular immunity and protective efficacy.

Efforts to develop a subunit vaccine against genital herpes have been hampered by lack of knowledge of the protective antigens of HSV-2, the causative agent of the disease. Vaccines based either on selected antigens or attenuated live virus approaches have not demonstrated meaningful clinical activity. We present here results of a therapeutic vaccine candidate, HerpV (formerly called AG-707), consisting of 32 HSV-2 peptides derived from 22 HSV-2 proteins, complexed non-covalently to the HSP70 chaperone and formulated with QS-21 saponin adjuvant. HerpV is observed to be immunogenic, generating CD4(+) and CD8(+) T cell responses in three mouse strains including HLA-A2 transgenic mice. Optimal T cell stimulation was dependent on the synergistic adjuvant properties of QS-21 with hsp70. The vaccine provided significant protection from viral challenge in a mouse prophylaxis model and showed signals of activity in a guinea pig therapeutic model of existing infection. Peripheral blood mononuclear cells from human HSV-2(+) subjects also showed reactivity in vitro to a subset of individual peptides and to the pool of all 32 peptides. Recombinant human Hsc70 complexed with the 32 peptides also stimulated the expansion of CD8(+) T cells from HSV-2(+) subjects in vitro. These studies demonstrate that HerpV is a promising immunotherapy candidate for genital herpes, and provide a foundation for evaluating HerpV in human HSV-2(+) subjects with the intent of eliciting CD4(+) and CD8(+) T cell responses to a broad array of viral antigens.

Autologous renal cell cancer vaccines using heat shock protein-peptide complexes.

Investigations into the role of heat shock proteins (HSPs) in immune response have progressed well into a third decade, and indications of their use for the treatment of renal cell carcinoma (RCC) in the adjuvant setting will be revealed in the near future when a randomized phase III clinical trial is completed. Additional ongoing and planned randomized clinical trials will test the efficacy of HSP-based vaccines in more advanced stages of RCC. This review describes the compelling scientific rationale behind testing HSPs in RCC against the backdrop of other immunotherapeutic approaches in this indication.

High-affinity interactions between peptides and heat shock protein 70 augment CD8+ T lymphocyte immune responses.

Exogenously delivered antigenic peptides complexed to heat shock proteins (HSPs) are able to enter the endogenous Ag-processing pathway and prime CD8+ CTL. It was determined previously that a hybrid peptide containing a MHC class I-binding epitope and HSP70-binding sequence Javelin (J0) in complex with HSP70 could induce cytotoxic T cell responses in vivo that were more robust than those induced by the minimal epitope complexed with HSP70. The present study introduces a novel, higher-affinity HSP70-binding sequence (J1) that significantly enhances binding of various antigenic peptides to HSP70. A competition binding assay revealed a dissociation constant that was 15-fold lower for the H2-K(b) OVA epitope SIINFEKL-J1 compared with SIINFEKL-J0, indicating a substantially higher affinity for HSP70. Further, modifying the orientation of the hybrid epitope and introducing a cleavable linker sequence between the Javelin and the epitope results in even greater immunogenicity, presumably by greater efficiency of epitope processing. The enhanced immunogenicity associated with Javelin J1 and the cleavable linker is consistently observed with multiple mouse and human epitopes. Thus, by creating a series of epitopes with uniform, high-affinity binding to HSP70, successful multiple epitope immunizations are possible, with equal delivery of each antigenic epitope to the immune system via HSP70. These modified epitopes have the potential for creating successful multivalent vaccines for immunotherapy of both infectious disease and cancer.

The potential of heat shock protein-peptide complexes as a therapeutic HIV vaccine.

HIV evades host immune responses through multiple mechanisms including high mutation rate, downregulation of host-cell, HLA class I molecules and depletion of key immune cells. Accordingly, an effective therapeutic vaccine approach to controlling HIV infection will nost likely need to modulate several pathways of both the innate and adaptive immune system. We propose the use of heat shock protein-peptide complexes (HSPPCs) to address this challenge. HSPPCs have been tested for 10 years in cancer patients with signals of clinical activity in phase I and II trials, and the results of two randomised phase III trials are anticipated in the near future. As the cancer setting can also be considered one of chronic disease, the rationale for using HSPPCs to treat HIV infection is clear. Several types of HSPPC vaccines that may be manufactured for testing in HIV-positive patients are discussed, including generation of an autologous vaccine derived from peripheral blood monloonuclear cells (PBMCs) of infected individuals.

Heat shock protein-mediated cross-presentation of exogenous HIV antigen on HLA class I and class II.

Strong CD4(+) and CD8(+) T cell responses are considered important immune components for controlling HIV infection, and their priming may be central to an effective HIV vaccine. We describe in this study an approach by which multiple CD4(+) and CD8(+) T cell epitopes are processed and presented from an exogenously added HIV-1 Gag-p24 peptide of 32 aa complexed to heat shock protein (HSP) gp96. CD8(+) T cell recognition of the HSP/peptide complex, but not the peptide alone, was inhibited by brefeldin A, suggesting an endoplasmic reticulum-dependent pathway. This is the first report to describe efficient processing and simultaneous presentation of overlapping class I- and class II-restricted epitopes from the same extracellularly added precursor peptide complexed to HSP. Given previous reports of the strong immunogenicity of HSP/peptide complexes, the present data suggest that HSP-complexed peptides containing multiple MHC class I- and class II-restricted epitopes represent potential vaccine candidates for HIV and other viral infections suitable to induce effective CTL memory by simultaneously providing CD4 T cell help.

Vaccination with heat shock protein-peptide complexes: from basic science to clinical applications.

There are currently over 150 medical centers worldwide enrolling patients in randomized, controlled Phase III clinical trials testing autologous cancer-derived heat-shock protein (HSP)-peptide complexes for the treatment of renal cell carcinoma and melanoma. In addition, autologous HSP-peptide complexes have been or are being tested in Phase I and II trials of chronic myelogenous leukemia, lymphoma and pancreatic, gastric and colorectal cancers. The door has more recently opened to clinical testing of off-the-shelf HSP-based treatments for infectious diseases. This review recounts the long history of basic research on HSPs in immune response. A keen understanding of how these ancient molecules orchestrate the immune response to cancer and infections has been gained, providing a clear rationale for translating this knowledge into clinical medicine.