Heat shock fusion protein gp96-Ig mediates strong CD8 CTL expansion in vivo

Enhancement of Immune Response of Bioconjugate Nanovaccine by Loading of CpG through Click Chemistry

CpG is a widely used adjuvant that enhances the cellular immune response by entering antigen-presenting cells and binding with receptors. The traditional physical mixing of the antigen and CpG adjuvant results in a low adjuvant utilization rate. Considering the efficient delivery capacity of nanovaccines, we developed an attractive strategy to covalently load CpG onto the nanovaccine, which realized the co-delivery of both CpG and the antigen. Briefly, the azide-modified CpG was conjugated to a bioconjugate nanovaccine (NP-OPS) against Shigella flexneri through a simple two-step reaction. After characterization of the novel vaccine (NP-OPS-CpG), a series of in vitro and in vivo experiments were performed, including in vivo imaging, lymph node sectioning, and dendritic cell stimulation, and the results showed that more CpG reached the lymph nodes after covalent coupling. Subsequent flow cytometry analysis of lymph nodes from immunized mice showed that the cellular immune response was greatly promoted by the nanovaccine coupled with CpG. Moreover, by analyzing the antibody subtypes of immunized mice, NP-OPS-CpG was found to further promote a Th1-biased immune response. Thus, we developed an attractive method to load CpG on a nanovaccine that is simple, convenient, and is especially suitable for immune enhancement of vaccines against intracellular bacteria.

Laser ablation: Heating up the anti-tumor response in the intracranial compartment

Immunotherapies, such as immune checkpoint inhibition (ICI), have had limited success in treating intracranial malignancies. These failures are due partly to the restrictive blood-brain-barrier (BBB), the profound tumor-dependent induction of local and systemic immunosuppression, and immune evasion exhibited by these tumors. Therefore, novel approaches must be explored that aim to overcome these stringent barriers. LITT is an emerging treatment for brain tumors that utilizes thermal ablation to kill tumor cells. LITT provides an additional therapeutic benefit by synergizing with ICI and systemic chemotherapies to strengthen the anti-tumor immune response. This synergistic relationship involves transient disruption of the BBB and local augmentation of immune function, culminating in increased CNS drug penetrance and improved anti-tumor immunity. In this review, we will provide an overview of the challenges facing immunotherapy for brain tumors, and discuss how LITT may synergize with the endogenous anti-tumor response to improve the efficacy of ICI.

Functions of heat shock proteins in pathways of the innate and adaptive immune system

For more than 50 years, heat shock proteins (HSPs) have been studied for their role in protecting cells from elevated temperature and other forms of stress. More recently, several roles have been ascribed to HSPs in the immune system. These include intracellular roles in Ag presentation and expression of innate receptors, as well as extracellular roles in tumor immunosurveillance and autoimmunity. Exogenously administered HSPs can elicit a variety of immune responses that have been used in immunotherapy of cancer, infectious diseases, and autoimmune disease.

The allure and peril of hematopoietic stem cell transplantation: overcoming immune challenges to improve success

Since its inception in the mid-twentieth century, the complication limiting the application and utility of allogeneic hematopoietic stem cell transplantation (allo-HSCT) to treat patients with hematopoietic cancer is the development of graft-versus-host disease (GVHD). Ironically, GVHD is induced by the cells (T lymphocytes) transplanted for the purpose of eliminating the malignancy. Damage ensuing to multiple tissues, e.g., skin, GI, liver, and others including the eye, provides the challenge of regulating systemic and organ-specific GVH responses. Because the immune system is also targeted by GVHD, this both: (a) impairs reconstitution of immunity post-transplant resulting in patient susceptibility to lethal infection and (b) markedly diminishes the individual's capacity to generate anti-cancer immunity--the raison d'etre for undergoing allo-HSCT. We hypothesize that deleting alloreactive T cells ex vivo using a new strategy involving antigen stimulation and alkylation will prevent systemic GVHD thereby providing a platform for the generation of anti-tumor immunity. Relapse also remains the major complication following autologous HSCT (auto-HSCT). While GVHD does not complicate auto-HSCT, its absence removes significant grant anti-tumor responses (GVL) and raises the challenge of generating rapid and effective anti-tumor immunity early post-transplant prior to immune reconstitution. We hypothesize that effective vaccine usage to stimulate tumor-specific T cells followed by their amplification using targeted IL-2 can be effective in both the autologous and allogeneic HSCT setting. Lastly, our findings support the notion that the ocular compartment can be locally targeted to regulate visual complications of GVHD which may involve both alloreactive and self-reactive (i.e., autoimmune) responses.

Heat shock protein vaccination and directed IL-2 therapy amplify tumor immunity rapidly following bone marrow transplantation in mice

Tumor relapse is the primary cause of mortality in patients with hematologic cancers following autologous hematopoietic stem cell transplantation (HSCT). Vaccination early after HSCT can exploit both the state of lymphopenia and minimal residual disease for generating antitumor immunity. Here, multiple vaccinations using lymphoma cells engineered to secrete heat shock protein fusion gp96-Ig within 2 weeks of T cell-replete syngeneic HSCT led to cross-presentation and increased survival of lymphoma-bearing mice. To enhance vaccine efficacy, interleukin (IL)-2 was directed to predominantly memory phenotype CD8(+) T lymphocytes and natural killer (NK) cells via administration bound to anti-IL-2 monoclonal antibody clone S4B6 (IL-2S4B6). Combination therapy with gp96-Ig vaccination and coordinated infusions of IL-2S4B6 resulted in marked prolongation of survival, which directly correlated with ~500% increase in effector CD8(+) T-cell numbers. Notably, this dual regimen elicited large increases in both donor CD8(+) T and NK cells, but not CD4(+) T lymphocytes; the former 2 populations are essential for both vaccine efficacy and protection against opportunistic infections after HSCT. Indeed, IL-2S4B6-treated HSCT recipients infected with Listeria monocytogenes exhibited decreased bacterial levels. These preclinical studies validate a new strategy particularly well suited to the post-HSCT environment, which may augment adaptive and innate immune function in patients with malignant disease receiving autologous HSCT.

Cloning, expression, and functional characterization of TL1A-Ig

TNF superfamily member 15 (TL1A) is the ligand for TNFR superfamily (TNFRSF)25. We previously reported that TNFRSF25 stimulation with an agonist Ab, 4C12, expands pre-existing CD4(+)Foxp3(+) regulatory T cells (Tregs) in vivo. To determine how the physiological ligand differs from the Ab, we generated a soluble mouse TL1A-Ig fusion protein that forms a dimer of TL1A trimers in solution with an apparent molecular mass of 516 kDa. In vitro, TL1A-Ig mediated rapid proliferation of Foxp3(+) Tregs and a population of CD4(+)Foxp3(-) conventional T cells. TL1A-Ig also blocked de novo biogenesis of inducible Tregs and it attenuated the suppressive function of Tregs. TNFRSF25 stimulation by TL1A-Ig in vivo induced expansion of Tregs such that they increased to 30-35% of all CD4(+) T cells in the peripheral blood within 5 d of treatment. Treg proliferation in vivo was dependent on TCR engagement with MHC class II. Elevated Treg levels can be maintained for at least 20 d with daily injections of TL1A-Ig. TL1A-Ig-expanded Tregs expressed high levels of activation/memory markers KLRG1 and CD103 and were highly suppressive ex vivo. TL1A-Ig-mediated Treg expansion in vivo was protective against allergic lung inflammation, a mouse model for asthma, by reversing the ratio of conventional T cells to Tregs in the lung and blocking eosinophil exudation into the bronchoalveolar fluid. Thus, TL1A-Ig fusion proteins are highly active and tightly controllable agents to stimulate Treg proliferation in vivo, and they are uniquely able to maintain high levels of expanded Tregs by repeated administration.

Heat shock proteins, autoimmunity, and cancer treatment

Heat shock proteins (HSPs) have been linked to the therapy of both cancer and inflammatory diseases, approaches that utilize contrasting immune properties of these proteins. It would appear that HSP family members Hsp60 and Hsp70, whether from external sources or induced locally during inflammation, can be processed by antigen-presenting cells and that HSP-derived epitopes then activate regulatory T cells and suppress inflammatory diseases. These effects also extend to the HSP-rich environments of cancer cells where elevated HSP concentrations may participate in the immunosuppressive tumor milieu. However, HSPs can also be important mediators of tumor immunity. Due to their molecular chaperone properties, some HSPs can bind tumor-specific peptides and deliver them deep into the antigen-processing pathways of antigen-presenting cells (APCs). In this context, HSP-based vaccines can activate tumor-specific immunity, trigger the proliferation and CTL capabilities of cancer-specific CD8+ T cells, and inhibit tumor growth. Further advances in HSP-based anticancer immunotherapy appear to involve improving the properties of the molecular chaperone vaccines by enhancing their antigen-binding properties and combating the immunosuppressive tumor milieu to permit programming of active CTL capable of penetrating the tumor milieu and specifically targeting tumor cells.

Hyperthermia on immune regulation: a temperature's story

Over the last decade the linkage between hyperthermia, heat shock proteins and fever with the body's immune system has been well investigated. The immunomodulatory function of hyperthermia has been found to be quite sensitively regulated by temperature, as different levels of heating can bring different modulatory effect on different sensitive targets. Understanding these intrinsic mechanisms could bring new inspirations on the design of clinical trials combining local tumor hyperthermia with immunotherapy in cancer patients. This review will attempt to tell the story about the effect of temperature on immune regulation, with special emphasis on the clinical application of hyperthermia and the feasibility of combining it with immunotherapy in the clinic.

Heat-shock protein–peptide complex-96 for the treatment of cancer

Heat-shock proteins (HSPs) are the most abundant and ubiquitous soluble intracellular proteins. Members of the HSP family bind peptides, including antigenic peptides generated within cells. HSPs also interact with antigen-presenting cells (APCs) through CD91 and other receptors, eliciting a cascade of events that includes representation of HSP-chaperoned peptides MHC, translocation of NF-kappaB into the nuclei, and maturation of dendritic cells. These consequences point to a key role of HSPs in fundamental immunologic phenomena such as activation of APCs, indirect presentation (or crosspriming) of antigenic peptides, and chaperoning of peptides during antigen presentation. The properties of HSPs also allow them to be used for immunotherapy of cancers and infections in novel ways. This paper reviews the development and clinical trial progress of vitespen, an HSP peptide complex vaccine based on tumor-derived glycoprotein 96.

Heat Shock Protein–Based Cancer Vaccines

The ability to duplicate the remarkable success of infectious disease vaccines in cancer, with durably robust and highly specific antitumor immune responses, has been long held as one of the keys in developing true "magic bullet" cancer therapies. This article attempts to explain why cancer vaccines have failed (so far), delineate the increasingly complex barriers that prevent the eliciting of effective antitumor immunity and examines the ability of heat shock protein-based vaccines to overcome these barriers. This article is not a definitive compendium of the huge body of relevant literature but rather focuses on the major concepts underlying active specific immunotherapy in general and heat shock protein vaccines in particular.

Heat shock proteins HSP70 and GP96: structural insights

Several heat shock proteins (HSPs) act as potent adjuvants for eliciting anti-tumor immunity. HSP-based tumor vaccine strategies have been highly successful in animal models and are undergoing testing in clinical trials. It is generally accepted that HSPs, functioning as chaperones for tumor antigens, elicit tumor-specific adaptive immune responses. HSPs also appear to induce innate immune responses in an antigen-independent fashion. Innate responses generated by HSPs may contribute to anti-tumor immunity. Immunologically active chaperones with anti-tumor activity are referred to as "immunochaperones". Here, we review the studies that address the role of structural domains or regions of the immunochaperones HSP70 and GP96 that may be involved in the induction of adaptive or innate immune responses.

Glucose-regulated protein 94/glycoprotein 96 elicits bystander activation of CD4+ T cell Th1 cytokine production in vivo

Glucose-regulated protein 94 (GRP94/gp96), the endoplasmic reticulum heat shock protein 90 paralog, elicits both innate and adaptive immune responses. Regarding the former, GRP94/gp96 stimulates APC cytokine expression and dendritic cell maturation. The adaptive component of GRP94/gp96 function reflects a proposed peptide-binding activity and, consequently, a role for native GRP94/gp96-peptide complexes in cross-presentation. It is by this mechanism that tumor-derived GRP94/gp96 is thought to suppress tumor growth and metastasis. Recent data have demonstrated that GRP94/gp96-elicited innate immune responses can be sufficient to suppress tumor growth and metastasis. However, the immunological processes activated in response to tumor Ag-negative sources of GRP94/gp96 are currently unknown. We have examined the in vivo immunological response to nontumor sources of GRP94/gp96 and report that administration of syngeneic GRP94/gp96- or GRP94/gp96-N-terminal domain-secreting KBALB fibroblasts to BALB/c mice stimulates CD11b(+) and CD11c(+) APC function and promotes bystander activation of CD4(+) T cell Th1 cytokine production. Only modest activation of CD8(+) T cell or NK cell cytolytic function was observed. The GRP94/gp96-dependent induction of CD4(+) T cell cytokine production was markedly inhibited by carrageenan, indicating an essential role for APC in this response. These results identify the bystander activation of CD4(+) T lymphocytes as a previously unappreciated immunological consequence of GRP94/gp96 administration and demonstrate that GRP94/gp96-elicited alterations in the in vivo cytokine environment influence the development of CD4(+) T cell effector functions, independently of its proposed function as a peptide chaperone.

Heat shock proteins: to present or not, that is the question

The contribution of major histocompatibility complex (MHC) I and II to the adaptive immune response has been well documented. In 1996, Peter Doherty and Rolf Zinkernagel were awarded the Nobel Prize, for their fundamental observations concerning the genetic elements involved in specific antigen (Ag) recognition. These elements encode molecules that present self and non-self peptide fragments to both CD4+ and CD8+ cytolytic T lymphocytes (CTL). The recognition by Srivastava and coworkers that heat shock proteins (HSPs) might also present Ag in chemically induced sarcomas brought about many new questions concerning the central dogma of Ag processing and presentation. HSPs, in particular glucose-regulated peptide 94 (GRP94), HSP70 and to a lesser extent HSP90, bind peptides that are immunogenic in vitro and in vivo. There is mounting evidence that these HSP-peptide complexes provide alternative Ag-specific recognition in many systems. Whether a separate genetic program evolved in addition to MHC that increases the antigenic repertoire of the cell or if this newly observed function of HSP is predominantly a laboratory-based phenomena and/or a normal chaperone function of this family of proteins remains to be answered. Nevertheless, there are clinical therapeutic strategies that involve HSP-derived peptides isolated from various tumors that look extremely promising.

Re-evaluating the role of heat-shock protein-peptide interactions in tumour immunity

Early investigations into the immune surveillance of chemically-induced sarcomas led to two important concepts in tumour immunobiology: one, tumour rejection can be elicited by immune recognition of tumour antigens; and two, tumours express unique sets of antigens, which are known as tumour-specific antigens. The pioneering studies of Srivastava and colleagues led to the proposal that heat-shock proteins (HSPs) function as ubiquitous tumour-specific antigens, with the specificity residing in a population of bound peptides that identify the tissue of origin of the HSP. However, recent findings, including new data on the cell biology of peptide generation and trafficking, have called into question the specificity of tumour rejection that is induced by HSPs.