Regulatory T-cell depletion synergizes with gp96-mediated cellular responses and antitumor activity

T cell receptor repertoire as a prognosis marker for heat shock protein peptide complex-96 vaccine trial against newly diagnosed glioblastoma

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults with a dismal prognosis. We previously reported that vaccination with heat shock protein peptide complex-96 (HSPPC-96) improves survival in patients with newly diagnosed GBM (NCT02122822). Especially for patients with a strong antitumor immune response after vaccination, a durable survival benefit can be achieved. Here, we conducted T cell receptor (TCR) sequencing to retrospectively examine the TCR repertoires of tumor-infiltrating lymphocytes in long-term survivors (LTS) and short-term survivors (STS). We found that LTS exhibit lower TCR repertoire diversity compared with STS, indicating the prevalence of dominant TCR clones in LTS tumors. Accordingly, the LTS group showed increased inter-patient similarity, especially among high-frequency TCR clones, implying some of these dominant clones are shared among LTS. Indeed, we discovered four TCR clones significantly enriched in the LTS group: the presence of these clones has predictive value for stratifying patients prior to vaccination. Together, these findings uncover a group of preexisting TCR clones shared in LTS that can be utilized as candidate biomarkers to select GBM patients most likely to durably respond to HSPPC-96 treatment.

Heat shock protein peptide complex-96 vaccination for newly diagnosed glioblastoma: a phase I, single-arm trial

BACKGROUND

Heat shock protein peptide complex-96 (HSPPC-96) triggers adaptive and innate antitumor immune responses. The safety and efficacy of HSPPC-96 vaccination was examined in patients with newly diagnosed glioblastoma multiforme (GBM).

METHODS

In this open-label, single-arm, phase I study, adult patients were vaccinated with HSPPC-96 in combination with the standard treatment for newly diagnosed GBM after surgical resection. Primary endpoints were frequency of adverse events and progression-free survival (PFS) at 6 months. Secondary endpoints included overall survival (OS), PFS, and tumor-specific immune response (TSIR).

RESULTS

A total of 20 patients with newly diagnosed GBM were enrolled from September 2013 to February 2015. No grade 3 or 4 vaccine-related adverse events were noted. After a median follow-up of 42.3 months, PFS was 89.5% (95% CI, 66.9%-98.7%) at 6 months, median PFS was 11.0 months (95% CI, 8.2-13.8), and median OS was 31.4 months (95% CI, 14.9-47.9). TSIR was significantly increased by 2.3-fold (95% CI, 1.7-3.2) after vaccination. Median OS for patients with high TSIR after vaccination was >40.5 months (95% CI, incalculable) as compared with 14.6 months (95% CI, 7.0-22.2) for patients with low TSIR after vaccination (hazard ratio, 0.25; 95% CI, 0.071-0.90; P = 0.034). A multivariate Cox regression model revealed TSIR after vaccination as a primary independent predicator for survival.

CONCLUSION

The HSPPC-96 vaccination, combined with the standard therapy, is a safe and effective strategy for treatment of newly diagnosed GBM patients. TSIR after vaccination would be a good indicator predicting the vaccine efficacy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02122822.

FUNDING

National Key Technology Research and Development Program of the Ministry of Science and Technology of China (2014BAI04B01, 2014BAI04B02), Beijing Natural Science Foundation (7164253), Beijing Talents Fund (2014000021469G257), and Shenzhen Science and Technology Innovation Committee (JSGG20170413151359491).

A novel tuberculosis antigen identified from human tuberculosis granulomas

Tuberculosis is a global infectious disease caused by Mycobacterium tuberculosis (Mtb). Although novel Mtb biomarkers from both the pathogen and host have been studied, more breakthroughs are still needed to meet different clinic requirements. In an effort to identify Mtb antigens, chaperone-peptide complexes were purified from TB infected lungs using free-solution isoelectric focusing combined with high resolution LTQ Orbitrap Velos mass spectrometry. Antigen specific cellular immune responses in vitro were then examined. Those efforts led to the identification of six Mtb peptides only identified in Tuberculosis lung samples and that were not found in the control samples. Additionally, antigen-specific IFN-γ secretion, T-cell proliferation, cytokine expression, and a cytotoxic assay were also evaluated. Among the peptides isolated, we identified a 34 amino acid peptide named PKAp belonging to a serine/threonine-protein kinase, as being able to generate Mtb-specific cellular immune responses as noted by elevated antigen-specific cytokine secretion levels, increased CD8(+) T-cell proliferation and a strong cytotoxic lymphocyte (CTL) response. Moreover, the immune stimulating abilities of PKAp were further validated in vivo, with target peptide immunized mice showing an increased cellular IFN-γ in both the lungs and spleen without causing immunopathogenesis. In conclusion, we identified novel functional Mtb antigens directly from the granulomatous lesions of Tuberculosis patients, inducing not only significant antigen-specific IFN-γ secretion but also a marked cytotoxic lymphocyte functional response. These findings indicated that PKAp has potential as a novel antigen biomarker for vaccine development.

Exogenous heat shock protein gp96 ameliorates CD4+CD62L+ T-cell-mediated transfer colitis

BACKGROUND

The heat shock protein gp96 is an endoplasmic reticulum chaperone involved in endoplasmic reticulum stress reactions. gp96 binds antigens and is secreted into extracellular space on cell stress. After reinternalization by antigen presenting cells, antigens can be transferred to major histocompatibility complex molecules. In recent studies, we found induction of gp96 during differentiation of intestinal macrophages, whereas it was absent in intestinal macrophages of patients with Crohn's disease.

METHODS

To study immuno-modulating effects of gp96 in T-cell transfer colitis BALB/c donor mice were injected with 2 × 100 μg gp96. After 1 week, 2.5 × 10(5) CD4+CD62L+ cells were isolated from spleens and injected into severe combined immunodeficiency recipients. Another group received cells from untreated donors and was treated with 100 μg gp96 after transfer. Control groups received cells from untreated donors, or buffer alone.

RESULTS

After transfer of CD4+CD62L+ T cells from gp96-pretreated donors, mice (TBT gp96) showed an initial weight loss, but after 3 weeks, they recovered and reached the starting weight after 5 weeks. Mice treated with gp96 after transfer (TAT gp96) showed a delayed weight loss in comparison with the CD4+CD62L+ group. The histological scores in CD4CD62L mice were 2.6 ± 0.1, in TBT gp96 mice 1.3 ± 0.3 (CD4+CD62L+ versus TBT gp96: P < 0.05) and in mice treated after transfer 1.9 ± 0.1 (CD4+CD62L+ versus TAT gp96: P < 0.05).

CONCLUSIONS

These findings indicate an essential role of gp96 in the maintenance of tolerance against luminal antigens in the intestinal mucosa. The absence of gp96 in intestinal macrophages of patients with Crohn's disease might provoke loss of this tolerance mediating mechanism.

Placenta-derived gp96 as a multivalent prophylactic cancer vaccine

A major challenge for designing prophylactic cancer vaccines is to define immunogenic and safe cancer antigens. Given the striking similarity of antigen expression patterns between cancer and embryonic tissues, we defined a prototype strategy of using placenta-derived heat shock protein gp96, which induces prophylactic anti-tumor T cell responses. Immunization with placental gp96 provided partial protection and long-term (at least 3 months) anti-tumor immunity against growth of transplantable melanoma or breast tumors in mice, elicited total protection against 7, 12-dimethylbenz(a)-anthracene (DMBA)-induced mammary tumors in rats, and significantly reduced the occurrence and growth of autochthonous breast tumors in HER2 transgenic mice. Placental gp96 activated HER2- and MUC1-specific T cell responses through binding to tumor-associated antigens. Our results reveal the novel immunogenicity of placental gp96 and its potential use as a multivalent cancer vaccine.

Targeting c-MYC with T-cells

Over-expression of the proto-oncogene c-MYC is frequently observed in a variety of tumors and is a hallmark of Burkitt´s lymphoma. The fact that many tumors are oncogene-addicted to c-MYC, renders c-MYC a powerful target for anti-tumor therapy. Using a xenogenic vaccination strategy by immunizing C57BL/6 mice with human c-MYC protein or non-homologous peptides, we show that the human c-MYC protein, despite its high homology between mouse and man, contains several immunogenic epitopes presented in the context of murine H2^b haplotype. We identified an MHC class II-restricted CD4⁺ T-cell epitope and therein an MHC class I-restricted CD8⁺ T-cell epitope (SSPQGSPEPL) that, after prime/boost immunization, protected up to 25% of mice against a lethal lymphoma challenge. Lymphoma-rejecting animals contained MHC multimer-binding CD8⁺ cell within the peripheral blood and displayed in vivo cytolytic activity with specificity for SSPQGSPEPL. Taken together these data suggest that oncogenic c-MYC can be targeted with specific T-cells.

MicroRNA-146a feedback suppresses T cell immune function by targeting Stat1 in patients with chronic hepatitis B

More than 350 million people are chronically infected with hepatitis B virus, and dysfunctional T cell responses contribute to persistent viral infection and immunopathogenesis in chronic hepatitis B (CHB). However, the underlying mechanisms of T cell hyporesponsiveness remain largely undefined. Given the important role of microRNA-146a (miR-146a) in diverse aspects of lymphocyte function, we investigated the potential role and mechanism of miR-146a in regulating T cell immune responses in CHB. We found that miR-146a expression in T cells is significantly upregulated in CHB compared with healthy controls, and miR-146a levels were correlated with serum alanine aminotransaminase levels. Both inflammatory cytokines and viral factors led to miR-146a upregulation in T cells. Stat1 was identified as a miR-146a target that is involved in antiviral cytokine production and the cytotoxicity of CD4(+) and CD8(+) T cells. In vitro blockage of miR-146a in T cells in CHB greatly enhanced virus-specific T cell activity. Therefore, our work demonstrates that miR-146a upregulation in CHB causes impaired T cell function, which may contribute to immune defects and immunopathogenesis during chronic viral infection.

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.

TAT-mediated gp96 transduction to APCs enhances gp96-induced antiviral and antitumor T cell responses

The heat shock protein gp96 is an adjuvant that can elicit T cell responses against cancer and infectious diseases, via antigen presentation, in both rodent models and clinical trials. Its uptake and internalization into antigen presenting cells (APCs) is a critical step in gp96-mediated immune responses. This study examined strategies to improve the cell internalization and T cell activation of gp96. It was found that recombinant fusion with the cell-penetrating peptide TAT (trans-activator of transcription) slightly decreased the aggregation level of gp96 and significantly increased its internalization into macrophages. Furthermore, immunization with the TAT-gp96 fusion dramatically enhanced gp96-mediated hepatitis B virus (HBV)-specific T cell responses and its antiviral efficiency in HBV transgenic mice compared to rgp96. In addition, the inclusion of TAT significantly improved the antitumor T cell immune response to a gp96 vaccine in the B16 melanoma model. These results provide evidence that the efficient transduction of gp96 into APCs can significantly enhance the outcome of gp96-based immunotherapy, and therefore provide a basis for more efficient approaches to improving the immunoregulatory and adjuvant functions of this unique T cell adjuvant.

Enhanced antitumoral efficacy and immune response following conditionally replicative adenovirus containing constitutive HSF1 delivery to rodent tumors

Background

Oncolytic adenoviruses are promising as anticancer agents but have limited clinical responses. Our previous study showed that heat shock transcription factor 1 (HSF1) overexpression could increase the anti-tumor efficacy of E1B55kD deleted oncolytic adenovirus through increasing the viral burst. Due to the important roles of heat shock proteins (HSPs) in eliciting innate and adaptive immunity, we reasoned that besides increasing the viral burst, HSF1 may also play a role in increasing tumor specific immune response.

Methods

In the present study, intra-dermal murine models of melanoma (B16) and colorectal carcinoma (CT26) were treated with E1B55kD deleted oncolytic adenovirus Adel55 or Adel55 incorporated with cHSF1, HSF1i, HSP70, or HSP90 by intra-tumoral injection. Tumors were surgically excised 72 h post injection and animals were analyzed for tumor resistance and survival rate.

Results

Approximately 95% of animals in the Adel55-cHSF1 treated group showed sustained resistance upon re-challenge with autologous tumor cells, but not in PBS, Adel55, or Adel55-HSF1i treated groups. Only 50–65% animals in the Adel55-HSP70 and Adel55-HSP90 treated group showed tumor resistance. Tumor resistance was associated with development of tumor type specific cellular immune responses. Adel55-cHSF1 treatment also showed higher efficacy in diminishing progression of the secondary tumor focus than Adel55-HSP70 or Adel55-HSP90 treatment.

Conclusions

Besides by increasing its burst in tumor cells, cHSF1 could also augment the potential of E1B55kD deleted oncolytic adenovirus by increasing the tumor-specific immune response, which is beneficial to prevent tumor recurrence. cHSF1 is a better gene for neoadjuvant immunotherapy than other heat shock protein genes.

The role of classical and non-classical HLA class I antigens in human tumors

In human tumors alterations in the surface expression and/or function of the major histocompatibility complex (MHC) class I antigens are frequently found and equip neoplastic cells with mechanisms to escape immune control. The aberrant expression of HLA class I molecules can be caused by structural alterations or dysregulations of genes encoding the classical HLA class I antigens and/or components of the HLA class I antigen processing machinery (APM). The dysregulation of APM components could occur at the epigenetic, transcriptional or post-transcriptional level. In some malignancies these abnormalities are significantly associated with a higher tumor staging, grading, disease progression and a reduced survival of patients as well as a failure to CD8(+) T cell-based immunotherapies. In addition to HLA class I abnormalities, expression of the non-classical HLA-G antigen is often induced in tumors, which could be mediated by various microenvironmental factors. Interestingly, soluble HLA-G serum and plasma levels have been useful markers for the prediction of some malignancies. The biological consequence of HLA-G expression or sHLA-G is an escape from T and NK cell-mediated recognition. Thus, alterations of non-classical and classical HLA class I antigens and components of the antigen processing pathway provide tumor cells with different mechanisms to inactivate immune responses resulting in tumor growth and evasion from host immune surveillance.