CTLA-4: new insights into its biological function and use in tumor immunotherapy

Cell surface delivery of TRAIL strongly augments the tumoricidal activity of T cells

PURPOSE

Adoptive T-cell therapy generally fails to induce meaningful anticancer responses in patients with solid tumors. Here, we present a novel strategy designed to selectively enhance the tumoricidal activity of T cells by targeted delivery of TNF-related apoptosis-inducing ligand (TRAIL) to the T-cell surface.

EXPERIMENTAL DESIGN

We constructed two recombinant fusion proteins, anti-CD3:TRAIL and K12:TRAIL. Tumoricidal activity of T cells in the presence of these fusion proteins was assessed in solid tumor cell lines, primary patient-derived malignant cells, and in a murine xenograft model.

RESULTS

When added to T cells, K12:TRAIL and anti-CD3:TRAIL selectively bind to the T-cell surface antigens CD3 and CD7, respectively, leading to cell surface accretion of TRAIL. Subsequently, anti-CD3:TRAIL and K12:TRAIL increased the tumoricidal activity of T cells toward cancer cell lines and primary patient-derived malignant cells by more than 500-fold. Furthermore, T-cell surface delivery of TRAIL strongly inhibited tumor growth and increased survival time of xenografted mice more than 6-fold.

CONCLUSIONS

Targeted delivery of TRAIL to cell surface antigens of T cells potently enhances the tumoricidal activity of T cells. This approach may be generally applicable to enhance the efficacy of adoptive T-cell therapy.

Cytotoxic T-lymphocyte antigen-4 polymorphisms and susceptibility to osteosarcoma

Despite the knowledge of many genetic alterations present in osteosarcoma, the complexity of this disease precludes placing its biology into a simple conceptual framework. Cytotoxic T-lymphocyte antigen-4 (CTLA-4) plays important roles in downregulating T-cell activation, thereby attenuating anti-tumor responses and increasing cancer susceptibility. Polymorphisms in the CTLA-4 gene are associated with different autoimmune diseases and cancers. The current study evaluated the association of four CTLA-4 gene mutations, -1661A/G (rs4553808), -318C/T (rs5742909), +49G/A (rs231775), and CT60A/G (rs3087243), with osteosarcoma in the Chinese population. CTLA-4 polymorphisms were detected by polymerase chain reaction-restriction fragment length polymorphism in 267 osteosarcoma patients and 282 age-matched healthy controls. Results showed that the CTLA-4 gene +49 AA genotype, +49 A allele, and GTAG haplotype were significantly more frequent in osteosarcoma patients than in controls (odds ratio [OR] 2.20, 95% confidence interval [CI] 1.23-2.95, p = 0.007; OR 1.32, 95% CI 1.03-1.69, p = 0.029, and OR = 1.47, 95% CI 1.03-2.09, p = 0.033, respectively). The CTLA-4 +49G/A polymorphism and GTAG haplotype are associated with increased risk of osteosarcoma.

Genetic variants associated with breast-cancer risk: comprehensive research synopsis, meta-analysis, and epidemiological evidence

BACKGROUND

More than 1000 reports have been published in the past two decades on associations between variants in candidate genes and risk of breast cancer. Results have been generally inconsistent. We did a literature search and meta-analyses to provide a synopsis of the current understanding of the genetic architecture of breast-cancer risk.

METHODS

A systematic literature search for candidate-gene association studies of breast-cancer risk was done in two stages, using PubMed on or before Feb 28, 2010. A total of 24,500 publications were identified, of which 1059 were deemed eligible for inclusion. Meta-analyses were done for 279 genetic variants in 128 candidate genes or chromosomal loci that had at least three data sources. Variants with significant associations by meta-analysis were assessed using the Venice criteria and scored as having strong, moderate, or weak cumulative evidence for an association with breast-cancer risk.

FINDINGS

51 variants in 40 genes showed significant associations with breast-cancer risk. Cumulative epidemiological evidence of an association was graded as strong for ten variants in six genes (ATM, CASP8, CHEK2, CTLA4, NBN, and TP53), moderate for four variants in four genes (ATM, CYP19A1, TERT, and XRCC3), and weak for 37 variants. Additionally, in meta-analyses that included a minimum of 10,000 cases and 10,000 controls, convincing evidence of no association with breast-cancer risk was identified for 45 variants in 37 genes.

INTERPRETATION

Whereas most genetic variants assessed in previous candidate-gene studies showed no association with breast-cancer risk in meta-analyses, 14 variants in nine genes had moderate to strong evidence for an association. Further evaluation of these variants is warranted.

FUNDING

US National Cancer Institute.

Ipilimumab: a novel treatment for metastatic melanoma

OBJECTIVE

To review the mechanism of action, pharmacokinetics, efficacy, safety, drug interactions, dosing, and economic considerations of ipilimumab.

DATA SOURCES

A literature search using MEDLINE (1966-November 2010) was performed using the terms ipilimumab, metastatic melanoma, MDX-010, and MDX-101. Additional data were obtained from meeting abstracts, bibliographies, and media releases.

STUDY SELECTION AND DATA EXTRACTION

English-language articles identified from the data sources were reviewed. Selected studies evaluated the pharmacology, pharmacokinetics, efficacy, and safety of ipilimumab for the treatment of metastatic melanoma.

DATA SYNTHESIS

The incidence of melanoma in the US is increasing faster than any other type of cancer in men and more than any other type of cancer, except lung cancer, in women. For patients with metastatic melanoma, systemic therapies are limited by low response rates, short durations of response, and a 5-year survival rate <10%. Ipilimumab, a novel CTLA-4 inhibitor, is under investigation for the treatment of metastatic melanoma. Results of a randomized, controlled Phase 3 trial showed a first-ever overall survival benefit for patients with previously treated metastatic melanoma who received ipilimumab compared with the controls. The majority of adverse events reported with ipilimumab administration are considered to be low-grade immune-related events involving the skin and intestine and can be managed medically. Nonetheless, 10-17% of patients have immune-related adverse events of grade 3 or higher severity, with 2-3% of these events resulting in death.

CONCLUSIONS

Ipilimumab is a novel CTLA-4 inhibitor that has been evaluated for the treatment of metastatic melanoma. On March 25, 2011, the Food and Drug Administration approved ipilimumab, making it the first agent indicated for unresectable or metastatic melanoma in more than a decade.

Association of T-cell regulatory gene polymorphisms with oral squamous cell carcinoma

Costimulatory molecules have complementary effects on T-cell activation and their balance may control the development of oral cancer. The aim of this study was to determine the relevance of cytotoxic T-lymphocyte antigen 4 (CTLA-4), CD28 and inducible costimulator (ICOS) polymorphisms in oral squamous cell carcinoma (OSCC). Genotyping for CTLA-4 (-1661 A/G and +49 A/G), CD28 (0 C/G and +3160 G/T) and ICOS (+637 A/C and +1599 C/T) was performed in the 83 patients with OSCC, compared to the 40 unrelated healthy volunteers as controls. The genotype CTLA-4 -1661 was significantly different between the patient group and the control group. The allele CTLA-4 -1661 G was significantly found more frequent in patients with OSCC (p=0.001). In bivariate analysis, noticeable differences between OSCC and controls were seen. The combinations CTLA-4 -1661 G/G and CTLA-4 +49 A/G, ICOS +1559 C/T and ICOS +1559 C/C each with CTLA-4 -1661 G/G, ICOS +637 C/C and ICOS +637 A/C each with CTLA-4 -1661, CTLA-4 -1661 A/G and ICOS +637 C/C, CD28 +3160 G/T and CTLA-4 -1661 A/A and CD28 +3160 G/T and CTLA-4 -1661 A/G were seen in the patient group only. Especially the polymorphisms of the CTLA-4 -1661-genotype - alone and in combination with other T cell regulator polymorphisms - seem to be possible predisposing factors for OSCC. Therefore, they might be future targets for a primary prophylaxis or an individualised therapy.

Cytotoxic T-lymphocyte-associated antigen-4

Cancer immunotherapy relies on the ability of the immune system to target tumor-specific antigens to generate an immune response. This initial response requires both binding of the MHC/antigen peptide to T-cell receptor complex, along with a second costimulatory signal created by the binding of CD28 on the T cell, with B7 located on the antigen-presenting cell. Regulatory checkpoints, such as cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), serve to attenuate this signal, thereby preventing autoimmunity. Its key role in regulating the immune system has made CTLA-4 an attractive therapeutic target for cancer, with the development of fully human monoclonal antibodies that have successfully targeted CTLA-4 in clinical trials. Augmentation of the immune response via blockade of CTLA-4 represents a significant advance in the field of oncology and has shown an improvement in survival for patients with metastatic melanoma. An increased understanding of the components of this pathway and the identification of other methods to modulate the immune system hold great promise for future therapy.

Visualization of Cell-Cell Interaction Contacts: Synapses and Kinapses

T-cell activation requires interactions of T-cell antigen receptors (TCR) and peptides presented by major histocompatibility complex molecules (MHCp) in an adhesive junction between the T-cell and antigen-presenting cell (APC). Stable junctions with bull's eye supramolecular activation clusters (SMACs) have been defined as immunological synapses. The term synapse works in this case because it joins roots for "same" and "fasten," which could be translated as "fasten in the same place." These structures maintain T-cell-APC interaction and allow directed secretion. We have proposed that SMACs are not really clusters, but are analogous to higher order membrane-cytoskeleton zones involved in amoeboid locomotion including a substrate testing lamellipodium, an adhesive lamella and anti-adhesive uropod. Since T-cells can also integrate signaling during locomotion over antigen presenting cells, it is important to consider adhesive junctions maintained as cells move past each other. This combination of movement (kine-) and fastening (-apse) can be described as a kinapse or moving junction. Synapses and kinapses operate in different stages of T-cell priming. Optimal effector functions may also depend upon cyclical use of synapses and kinapses. Visualization of these structures in vitro and in vivo presents many distinct challenges that will be discussed in this paper.

Cytotoxic T-lymphocyte antigen-4 +49G/A polymorphism is associated with increased risk of osteosarcoma

BACKGROUND

Cytotoxic T-lymphocyte antigen-4 (CTLA-4) is a potent immunoregulatory molecule that suppresses anti-tumor response by down-regulating T-cell activation. CTLA-4 gene +49G/A polymorphism (rs231775) has been reported to be associated with various cancers.

OBJECTIVE

The objective of this study is to investigate the association between CTLA-4 gene +49G/A polymorphism and the susceptibility to osteosarcoma in the Chinese population.

METHODS

The CTLA-4 variant +49G/A was detected by polymerase chain reaction-restriction fragment length polymorphism in 205 osteosarcoma cases and 216 age-matched healthy controls. Data were analyzed using the Chi-square test.

RESULTS

Frequencies of the CTLA-4 +49AA genotype and the +49A allele were significantly increased in patients with osteosarcoma compared to healthy controls (OR 2.27, p=0.010, and OR 1.41, p=0.015).

CONCLUSIONS

Our data suggest that the +49G/A polymorphism of CTLA-4 gene is associated with increased susceptibility to osteosarcoma.

Regulatory T cells in colorectal cancer: from biology to prognostic relevance

Regulatory T cells (Tregs) were initially described as "suppressive" lymphocytes in the 1980s. However, it took almost 20 years until the concept of Treg-mediated immune control in its present form was finally established. Tregs are obligatory for self-tolerance and defects within their population lead to severe autoimmune disorders. On the other hand Tregs may promote tolerance for tumor antigens and even hamper efforts to overcome it. Intratumoral and systemic accumulation of Tregs has been observed in various types of cancer and is often linked to worse disease course and outcome. Increase of circulating Tregs, as well as their presence in mesenteric lymph nodes and tumor tissue of patients with colorectal cancer de facto suggests a strong involvement of Tregs in the antitumor control. This review will focus on the Treg biology in view of colorectal cancer, means of Treg accumulation and the controversies regarding their prognostic significance. In addition, a concise overview will be given on how Tregs and their function can be targeted in cancer patients in order to bolster an inherent immune response and/or increase the efficacy of immunotherapeutic approaches.

OX40 engagement stabilizes Mxd4 and Mnt protein levels in antigen-stimulated T cells leading to an increase in cell survival

OX40 engagement on activated T cells leads to increased proliferation, expansion and survival of Ag-specific T cells. Direct ex vivo examination of Ag-stimulated murine T cells show that the Myc antagonists, Mxd4 and Mnt, are transiently upregulated and translocated to the nucleus following OX40 engagement and may be involved in suppressing cell death. Both Mxd4 and Mnt are upregulated following OX40 stimulation through increased protein stability and we identify a critical phosphorylation site in Mxd4 that controls Mxd4 stability. The upregulation of Mxd4 and Mnt contributes to OX40-mediated T-cell survival because siRNA knockdown of Mxd4 and Mnt led to increased cell death. We hypothesize the upregulation of c-Myc following OX40 engagement drives T-cell proliferation and that upregulation of Mxd4 and Mnt suppresses Myc-dependent cell death. Thus, Mxd4 and Mnt upregulation following OX40 engagement most likely increases T-cell survival.

Meta-analysis of genome-wide association studies in celiac disease and rheumatoid arthritis identifies fourteen non-HLA shared loci

Epidemiology and candidate gene studies indicate a shared genetic basis for celiac disease (CD) and rheumatoid arthritis (RA), but the extent of this sharing has not been systematically explored. Previous studies demonstrate that 6 of the established non-HLA CD and RA risk loci (out of 26 loci for each disease) are shared between both diseases. We hypothesized that there are additional shared risk alleles and that combining genome-wide association study (GWAS) data from each disease would increase power to identify these shared risk alleles. We performed a meta-analysis of two published GWAS on CD (4,533 cases and 10,750 controls) and RA (5,539 cases and 17,231 controls). After genotyping the top associated SNPs in 2,169 CD cases and 2,255 controls, and 2,845 RA cases and 4,944 controls, 8 additional SNPs demonstrated P<5×10⁻⁸ in a combined analysis of all 50,266 samples, including four SNPs that have not been previously confirmed in either disease: rs10892279 near the DDX6 gene (P_combined = 1.2×10⁻¹²), rs864537 near CD247 (P_combined = 2.2×10⁻¹¹), rs2298428 near UBE2L3 (P_combined = 2.5×10⁻¹⁰), and rs11203203 near UBASH3A (P_combined = 1.1×10⁻⁸). We also confirmed that 4 gene loci previously established in either CD or RA are associated with the other autoimmune disease at combined P<5×10⁻⁸ (SH2B3, 8q24, STAT4, and TRAF1-C5). From the 14 shared gene loci, 7 SNPs showed a genome-wide significant effect on expression of one or more transcripts in the linkage disequilibrium (LD) block around the SNP. These associations implicate antigen presentation and T-cell activation as a shared mechanism of disease pathogenesis and underscore the utility of cross-disease meta-analysis for identification of genetic risk factors with pleiotropic effects between two clinically distinct diseases.

Celiac disease (CD) and rheumatoid arthritis (RA) are two autoimmune diseases characterized by distinct clinical features but increased co-occurrence in families and individuals. Genome-wide association studies (GWAS) performed in CD and RA have identified the HLA region and 26 non-HLA genetic risk loci in each disease. Of the 26 CD and 26 RA risk loci, previous studies have shown that six are shared between the two diseases. In this study we aimed to identify additional shared risk alleles and, in doing so, gain more insight into shared disease pathogenesis. We first empirically investigated the distribution of putative risk alleles from GWAS across both diseases (after removing known risk loci for both diseases). We found that CD risk alleles are non-randomly distributed in the RA GWAS (and vice versa), indicating that CD risk alleles have an increased prior probability of being associated with RA (and vice versa). Next, we performed a GWAS meta-analysis to search for shared risk alleles by combing the RA and CD GWAS, performing both directional and opposite allelic effect analyses, followed by replication testing in independent case-control datasets in both diseases. In addition to the already established six non-HLA shared risk loci, we observed statistically robust associations at eight SNPs, thereby increasing the number of shared non-HLA risk loci to fourteen. Finally, we used gene expression studies and pathway analysis tools to identify the plausible candidate genes in the fourteen associated loci. We observed remarkable overrepresentation of T-cell signaling molecules among the shared genes.

Sipuleucel-T: harbinger of a new age of therapeutics for prostate cancer

Sipuleucel-T (Provenge) is the first therapeutic cancer vaccine approved by the US FDA. The approval heralds the long-awaited promise of improved patient survival with minimal toxicity by therapies designed to generate an active, specific anticancer immune response. The development of this first-in-class agent as well as other therapeutic vaccines in clinical evaluation has also led to a better understanding of relevant patient populations and end points for clinical trials. This article discusses the development and approval of sipuleucel-T in the context of other approved therapies for prostate cancer, as well as controversies and novel paradigms brought about by this new agent.

CD4+/CD25+ cells in systemic inflammation in COPD

The autoimmune reaction is recently suspected to play a role in the pathogenesis of chronic obstructive lung disease (COPD). As COPD is a systemic disease, the elements of an autoimmune response in circulatory system is of interest. It has been shown that regulatory T cells are important in the control of autoimmunity. There are some data on a role of adiponectin in the regulation of immune reactions. The objective of this study was to assess the elements of autoimmune reaction in the peripheral blood (PB) of patients with COPD. Twenty-eight patients with mild/moderate COPD and 20 healthy volunteers were investigated. Flow cytometry method with mixtures of monoclonal antibodies anti: CD14/CD45, CD3/CD19, CD4/CD25/CTLA4 and CD8/CD25 were used. Concentration of adiponectin was measured using ELISA method. We observed significantly lower proportion of CD4+/CD25+ as well as CD4+/CD25+ (high) cells in COPD patients than in healthy controls (15.3 versus 17.8% and 0.79 versus 1.54%, respectively, P < 0.05). The proportion of CTLA4+ cells in CD25+ cells and the mean fluorescence of CTLA4 on CD4+ cells were higher in patients than in healthy controls (10.4 versus 4.7%, P < 0.05, 189% versus 149%, non significant, respectively). We found significantly elevated concentration of adiponectin in patients when compared to healthy subjects (15.4 versus 8.5 μl/ml, P < 0.05). We found that the adiponectin/BMI ratio correlated with the decrease of FEV(1) %. The results of this study support the possible role of CD4/CD25/CTLA4 cells and adiponectin in the systemic inflammation in COPD.

The dermis as a portal for dendritic cell-targeted immunotherapy of cutaneous melanoma

Complete surgical excision at an early stage remains the only curative treatment for cutaneous melanoma with few available adjuvant therapy options. Nevertheless, melanoma is a relatively immunogenic tumor type and particularly amenable to immunotherapeutic approaches. A dense network of cutaneous dendritic cells (DC) may account for the reported efficacy of vaccination through the skin and provide an attractive target for the immunotherapy of melanoma. Several phenotypically distinct DC subsets are discernable in the skin, among others, epidermal Langerhans cells and dermal DC. Upon appropriate activation both subsets can efficiently migrate to melanoma-draining lymph nodes (LN) to prime T cell-mediated responses. Unfortunately, from an early stage, melanoma development is characterized by strong immune suppression, facilitating unchecked tumor growth and spread. Particularly the primary tumor site and the first-line tumor-draining LN, the so-called sentinel LN, bear the brunt of this melanoma-induced immune suppression-and these are exactly the sites where anti-melanoma effector T cell responses should be primed by DC in order to prevent early metastasis. Through local immunopotentiation or through DC-targeted vaccination, the dermis may be utilized as a portal to activate DC and kick-start or boost effective T cell-mediated anti-melanoma immunity, even in the face of this immune suppression.

Current experience with CTLA4-blocking monoclonal antibodies for the treatment of solid tumors

Monoclonal antibodies (mAbs) specific for cytotoxic T lymphocyte-associated antigen 4 (CTLA4) are a novel form of immunotherapy for treatment of patients with advanced cancers. These anti-CTLA4 mAbs prevent normal downregulation of the immune system, thus prolonging and enhancing T-cell activation and potentially promoting an antitumor immune response. Clinical studies in patients with advanced cancers have indicated that CTLA4 blockade with mAbs is associated with antitumor activity in a small percentage of patients and has a manageable toxicity profile. The key limitations for broader applicability of this mode of therapy are better definition of the mechanism that leads to tumor rejection and the validation of favorable observations in single-arm studies into prospectively randomized clinical trials.

Signaling through OX40 enhances antitumor immunity

The existence of tumor-specific T cells, as well as their ability to be primed in cancer patients, confirms that the immune response can be deployed to combat cancer. However, there are obstacles that must be overcome to convert the ineffective immune response commonly found in the tumor environment to one that leads to sustained destruction of tumor. Members of the tumor necrosis factor (TNF) superfamily direct diverse immune functions. OX40 and its ligand, OX40L, are key TNF members that augment T-cell expansion, cytokine production, and survival. OX40 signaling also controls regulatory T-cell differentiation and suppressive function. Studies over the past decade have demonstrated that OX40 agonists enhance antitumor immunity in preclinical models using immunogenic tumors; however, treatment of poorly immunogenic tumors has been less successful. Combining strategies that prime tumor-specific T cells together with OX40 signaling could generate and maintain a therapeutic antitumor immune response.

Clinical experiences with anti-CD137 and anti-PD1 therapeutic antibodies

Monoclonal antibodies (mAbs) provide a pharmacological platform to block or activate the function of surface receptors. The immune system has evolved receptor-ligand pairs that repress or empower the cellular immune response, which, if tampered with, unleash more potent cellular immunity against tumor antigens. Agonist antibodies directed against CD137 (4-1BB) on the surface of antigen-primed T lymphocytes increase tumor immunity that is curative against some transplantable murine tumors. A fully human IgG4 anti-CD137 antibody is under development with signs of clinical activity and cases of severe liver toxicity that seem to be on-target and dose-dependent effects. Programmed death-1 (PD1) is a surface molecule delivering inhibitory signals important to maintain T-cell functional silence against their cognate antigens. Interference with PD1 or its ligand PD-L1 (B7-H1) increases antitumor immunity. As a result anti-PD1 and anti-PD-L1 human mAbs are under clinical development. Phase I trials with anti-PD1 mAb have yielded encouraging results with durable objective responses and a reasonable safety profile. As new class of drugs in cancer therapy, immunostimulatory mAbs have resulted in redefinition of tumor response criteria and rethinking of the rationale for combining these among each other and with other strategies.

Hepatitis B e-antigen persistency is associated with the properties of HBV-specific CD8 T cells in CHB patients

To investigate the correlation between the HBeAg and the properties of HBV-specific CD8 T cells, as well as liver injury, serum HBV markers, liver histology, the frequency and phenotypic characteristics of CD4(+)CD25(+) Treg and HBV-pentamer(+) CD8 T cells were measured. No significant differences between the median serum ALT levels, the frequency and Foxp3 expression of CD4(+)CD25(+) Treg, and liver fibrosis were observed. Higher HBV DNA levels in HBeAg(+) patients were observed, while liver necroinflammation was more severe in HBeAg(-) patients. Differences in HBV-pentamer(+) T cell frequency were not significant, but increased PD-1 and CTLA-4 expression on HBV-specific CD8 T cells was seen in the HBeAg(+) group. HBV-peptide stimulation with anti-PD-L1 and anti-CTLA-4 significantly increased the proliferation in PBMCs from both groups, but enhanced IFN-γ production only in the HBeAg(+) patients. Therefore, HBeAg persistency in CHB patients probably increased the expression of PD-1 and CTLA-4 on HBV-specific CD8 T cells, which may be associated with the low intensity of T cell responses and high HBV DNA load.

The current and emerging role of immunotherapy in prostate cancer

Recent phase III trial results have demonstrated the effectiveness of sipuleucel-T, a therapeutic cancer vaccine, in the treatment of metastatic prostate cancer. Yet, despite the survival benefit of sipuleucel-T, questions remain about how immunologic agents can be used in the treatment of metastatic prostate cancer. The primary issue confounding researchers and practitioners about the benefits of sipuleucel-T is the lack of effect on time to progression. It may be helpful to note that recent phase II data from a different therapeutic prostate cancer vaccine (Prostvac), as well as phase III data from an anti-cytotoxic T-lymphocyte antigen-4 (CTLA-4) blocking agent in metastatic melanoma, also show improved survival without short-term changes in disease progression. Furthermore, mathematical tumor growth models provide some insight into the fact that immunologic therapies do allow for continued tumor growth, but at a slower rate, thus prolonging survival. This understanding can help to clarify the role of the newly approved sipuleucel-T in the treatment of metastatic prostate cancer. It is also possible that appropriate sequencing of therapies could further improve the clinical course for such patients. Additional clinical trials will further our understanding of the role of therapeutic cancer vaccines and add new agents to the armamentarium of therapy for patients with prostate cancer.

Extended dose ipilimumab with a peptide vaccine: immune correlates associated with clinical benefit in patients with resected high-risk stage IIIc/IV melanoma

PURPOSE

To determine safety and feasibility of adjuvant ipilimumab following resection of high-risk melanoma and to identify surrogate markers for benefit.

EXPERIMENTAL DESIGN

In this phase II trial, 75 patients with resected stage IIIc/IV melanoma received the CTLA-4 antibody ipilimumab every 6 to 8 weeks for 1 year. Eligible patients received further maintenance treatments. The first 25 patients received 3 mg/kg of ipilimumab, and an additional 50 patients received 10 mg/kg. HLA-A*0201+ patients received multipeptide immunizations in combination with ipilimumab. Leukapheresis was performed prior to and 6 months after initiation of treatment.

RESULTS

Median overall and relapse-free survivals were not reached after a median follow-up of 29.5 months. Significant immune-related adverse events were observed in 28 of 75 patients and were positively associated with longer relapse-free survival. Antigen-specific T cell responses to vaccine were variable, and vaccine combination was not associated with additional benefit. No effects on T regulatory cells were observed. Higher changes in Th-17 inducible frequency were a surrogate marker of freedom from relapse (P = 0.047), and higher baseline C-reactive protein (CRP) levels were associated with freedom from relapse (P = 0.035).

CONCLUSIONS

Adjuvant ipilimumab following resection of melanoma at high risk for relapse appeared to be associated with improved outcome compared to historical reports. Significant immune-related adverse events were generally reversible and appeared to be associated with improved relapse-free survival. Although vaccination failed to induce a consistent in vitro measurable response, a higher change in Th-17 inducible cells and higher baseline CRP levels were positively associated with freedom from relapse.

Differential requirements for CD80/86-CD28 costimulation in primary and memory CD4 T cell responses to vaccinia virus

Vaccinia virus infection can confer immunity to smallpox by inducing potent T cell and antibody responses. While the CD8 T cell response to vaccinia virus has been well characterized, less is known about factors required for priming and memory for the CD4 T cells. Focusing on two recently described epitopes, we show that after intranasal infection, both I1L and L4R epitopes are co-dominant during the acute response, but the I1L epitope dominates during memory. CD4 T cell priming was intact in the absence of CD80/86, however secondary responses were reduced. This contrasts with our previous data showing CD80/86-CD28 interaction is required for optimal primary and memory CD8 T cell responses. The absence of CD80/86 also changed the immunodominance hierarchy during memory, with the I1L and L4R responses becoming co-dominant in knockout mice. These data highlight different costimulatory requirements for primary CD4 and CD8 T cell responses to vaccinia virus.

Spatiotemporal basis of CTLA-4 costimulatory molecule-mediated negative regulation of T cell activation

T cell activation is positively and negatively regulated by a pair of costimulatory receptors, CD28 and CTLA-4, respectively. Because these receptors share common ligands, CD80 and CD86, the expression and behavior of CTLA-4 is critical for T cell costimulation regulation. However, in vivo blocking of CD28-mediated costimulation by CTLA-4 and its mechanisms still remain elusive. Here, we demonstrate the dynamic behavior of CTLA-4 in its real-time competition with CD28 at the central-supramolecular activation cluster (cSMAC), resulting in the dislocalization of protein kinase C-θ and CARMA1 scaffolding protein. CTLA-4 translocation to the T cell receptor microclusters and the cSMAC is tightly regulated by its ectodomain size, and its accumulation at the cSMAC is required for its inhibitory function. The CTLA-4-mediated suppression was demonstrated by the in vitro anergy induction in regulatory T cells constitutively expressing CTLA-4. These results show the dynamic mechanism of CTLA-4-mediated T cell suppression at the cSMAC.

Attenuated T cell responses to a high-potency ligand in vivo

According to this study, the strongest T cell receptor ligands in vitro do not necessarily induce the strongest T cell responses in vivo, suggesting that vaccine designers may need to reconsider their strategies.

αβ T cell receptor (TCR) recognition of foreign peptides bound to major histocompatibility complex (pMHC) molecules on the surface of antigen presenting cells is a key event in the initiation of adaptive cellular immunity. In vitro, high-affinity binding and/or long-lived interactions between TCRs and pMHC correlate with high-potency T cell activation. However, less is known about the influence of TCR/pMHC interaction parameters on T cell responses in vivo. We studied the influence of TCR/pMHC binding characteristics on in vivo T cell immunity by tracking CD4⁺ T cell activation, effector, and memory responses to immunization with peptides exhibiting a range of TCR/pMHC half-lives and in vitro T cell activation potencies. Contrary to predictions from in vitro studies, we found that optimal in vivo T cell responses occur to ligands with intermediate TCR/pMHC half-lives. The diminished in vivo responses we observed to the ligand exhibiting the longest TCR/pMHC half-life were associated with attenuation of intracellular signaling, expansion, and function over a broad range of time points. Our results reveal a level of control over T cell activation in vivo not recapitulated in in vitro assays and highlight the importance of considering in vivo efficacy of TCR ligands as part of vaccine design.

As an important part of immune system, T cells fight infections by recognizing signs of foreign invaders. A molecule on the surface of these cells—called the T cell receptor—recognizes and binds to protein components (peptides) from bacteria, viruses, and other pathogens that are displayed on the surface of other cells. The T cells can then use this information to orchestrate the fight against infection. Vaccination involves injecting into the body foreign peptides that mimic a pathogen, therefore tricking it into raising a T cell response against that pathogen that will be protective in the event of a real infection. We studied T cell responses in mice injected with one of several peptides to which the T cell receptor binds more or less strongly. Contrary to expectations, we found that the peptide that interacted most strongly with the T cell receptor did not provoke the strongest T cell response. This may be nature's way of preventing harmful inflammatory damage due to excessively strong T cell activation. Our work shows that peptides that bind the T cell receptor with medium strength may be best to use for vaccines. Current vaccine strategies seeking to design peptides that bind with maximum strength to the T cell receptor may need to be reconsidered in light of our findings.

Inhibiting the inhibitors: evaluating agents targeting cancer immunosuppression

IMPORTANCE OF THE FIELD

Immunotherapy of cancer has not improved disease-free or overall patient survival. The lack of concordance between immunological and clinical responses in cancer immunotherapy trials is thought to result from the pervasive presence of tumor-driven immune suppression that allows tumor to escape and that has not been adequately targeted by current therapies.

AREAS COVERED IN THIS REVIEW

Because multiple mechanisms of tumor induced suppression have been identified and shown to contribute to tumor escape, the opportunity arises to interfere with these mechanisms. A range of known tumor-derived inhibitors can now be blocked or neutralized by biologic or metabolic agents. Used alone or in combination with each other or with conventional cancer therapies, these agents offer novel therapeutic strategies for the control of tumor escape.

WHAT THE READER WILL GAIN

This review deals with currently available inhibitors for counteracting tumor immune escape. The restoration of effective anti-tumor immunity in patients with cancer will require new approaches aiming at: i) protection of immune cells from adverse effects of myeloid-derived suppressor cells, regulatory T cells or inhibitory factors thus enhancing effector functions; and ii) prolonging survival of central memory T cells, thus ensuring long-term protection.

TAKE HOME MESSAGE

Inhibitors of mechanisms responsible for tumor escape could restore anti-tumor immune responses in patients with cancer.

Alternatives to calcineurin inhibition in renal transplantation: belatacept, the first co-stimulation blocker

In the early 1990s, Linsley and colleagues produced a soluble fusion protein, comprising of the extracellular domain of cytotoxic T lymphocyte antigen (CTLA)4 and the human IgG1 Fc domain. Since then, several hundreds of scientific publications have demonstrated that CTLA4–Ig blocks CD28-mediated co-stimulation and suppresses unwanted T cell-mediated responses in animal models of transplantation, autoimmunity and inflammation. In the past two decades, Bristol-Myers Squibb Co. has developed abatacept, a CTLA4–Ig molecule for treating psoriasis and rheumatoid arthritis, and belatacept, a second-generation, higher affinity CTLA4–Ig molecule for use in kidney transplantation. Belatacept represents a new class of transplantation immunosuppressants and potentially offers clinicians a breakthrough therapy to preserve kidney function in the long term and reduce the side effects of current immunosuppressive therapies.

Therapeutic cancer vaccines in prostate cancer: the paradox of improved survival without changes in time to progression

Therapeutic cancer vaccines represent a new class of agents in the treatment of cancer. Sipuleucel-T is an antigen-presenting cell-based vaccine that recently demonstrated a significant 4.8-month improvement in overall survival in advanced prostate cancer patients and was well tolerated. The findings of that study have been met with skepticism, primarily because the agent did not change initial disease progression and yet led to longer survival. Although the commonly accepted treatment paradigm suggests that treatments should initially decrease tumor volume, perhaps vaccines work differently. Vaccines may induce delayed responses not seen in the first few months of therapy or they may initiate a dynamic immune response that ultimately slows the tumor growth rate, resulting in longer survival. Subsequent therapies may also combine with the induced immune response, resulting in a combination that is more effective than conventional treatments alone. Also, other treatments may alter tumor-associated antigen expression, enhancing the immune response. Future trials are currently planned to investigate these hypotheses; however, the results of the sipuleucel-T vaccine in prostate cancer should not be dismissed. Results with another vaccine in prostate cancer are similar, perhaps suggesting a class effect. In a broader context, clinicians may need to reconsider how they measure success. Several agents have been approved that produce superior disease progression results, but do not affect overall survival. Given the toxicity and costs of cancer therapies, perhaps studies should put more weight on long-term survival endpoints than on short-term endpoints that may be less consequential.

Overcoming immunological tolerance to melanoma: Targeting CTLA-4

Abstract The use of immunotherapeutics in melanoma has received much attention, and recent advances to further characterize the regulatory components of the immune system and the importance of co-stimulatory molecules have opened a new area for clinical investigation. Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) serves as a negative regulator of immunity. Recent trials administering fully human anti-CTLA-4 monoclonal antibodies to melanoma patients have demonstrated clinically meaningful responses. Treatment with CTLA-4 blocking antibodies, however, is not without potential toxicities. Autoimmune side-effects, the most common being colitis-associated diarrhea, are frequently associated with clinical responses. In efforts to build upon prior vaccination efforts as well as attempt to offer patients clinically meaningful immune responses with a CTLA-4 blockade but without significant toxicities, we conducted a clinical trial in patients who previously received autologous tumor cells engineered to secrete granulocyte-macrophage colony stimulating factor (GVAX; Cell Genesys, South San Francisco, CA, USA) with periodic infusions of CTLA-4 blocking antibodies. This sequential treatment resulted in clinically significant anti-tumor immunity without grade 3 or 4 toxicity in most patients. Pathological analyses following treatment of pre-existing tumors revealed a linear correlation between tumor necrosis and the ratio of intra-tumoral CD8+ effector cells to FoxP3+ regulatory cells (T(regs)). Effective anti-tumor immunity and serious autoimmunity can be disassociated. Further targeting of anti-tumor T(regs)in combinatorial therapy approaches may be a rich avenue of future investigation.

Cutting edge: CTLA-4--B7 interaction suppresses Th17 cell differentiation

Th cells that produce IL-17 (Th17 cells) are a distinct subset of Th cells implicated in several autoimmune diseases. Although CD28-B7 interaction has been shown to be involved in Th17 differentiation in vitro, the role of CTLA-4 in controlling Th17 development is completely unknown. We report in this paper that blocking the CTLA-4-B7 interaction potentiates Th17 cell differentiation in vitro and in vivo. Furthermore, blocking CTLA-4-B7 interaction in vivo confers the susceptibility of experimental autoimmune myocarditis to CD28(-/-) mice or increases the severity of experimental autoimmune myocarditis in wild-type mice. The enhanced disease susceptibility is mediated by heightened Th17 responses. With these results, we are the first to demonstrate that CTLA-4-B7 interaction inhibits Th17 differentiation in vitro and in vivo and suppresses Th17-mediated autoimmunity.

CTLA-4 blockade: therapeutic potential in cancer treatments

Enhancing or prolonging T-cell activation by monoclonal antibodies (mAbs) blocking negative signaling receptors such as CTLA4 is one approach to overcoming tumor-induced immune tolerance. Ipilimumab and tremelimumab inhibit CTLA4, prolonging antitumor immune responses and leading to durable anti-tumor effects. Treatment with these mAbs has demonstrated clinically important and durable tumor responses and disease control rates in patients with unresectable advanced melanoma. Durable objective responses have been reported across a spectrum of doses and schedules, with relative safety in this patient population. Although the phase III tremelimumab melanoma study was closed for "futility", the 1-year survival rate of >50% for tremelimumab and the median survival of 11.7 months (compared with 10.7 months for chemotherapy) are notable. Results of the phase III studies testing CTLA4-blockade with ipilimumab are eagerly anticipated. The further development of these agents includes testing in the neoadjuvant melanoma setting (ipilimumab) as well the adjuvant high-risk melanoma setting (ipilimumab). Future progress with CTLA-4 blockade therapy will also likely come from the use of combinations of agents that target several critical regulatory pathways of the immune system and modulate the immune response in the host in a synergistic and controlled fashion.

Local release of highly loaded antibodies from functionalized nanoporous support for cancer immunotherapy

We report that antibodies can be spontaneously loaded in functionalized mesoporous silica (FMS) with superhigh density (0.4-0.8 mg of antibody/mg of FMS) due to their comprehensive noncovalent interaction. The superhigh loading density and noncovalent interaction between FMS and antibodies allow long-lasting local release of the immunoregulatory molecules from FMS under physiological conditions. Preliminary data indicate that FMS-anti-CTLA4 antibody injected directly into a mouse melanoma induces much greater and extended inhibition of tumor growth than the antibody given systemically. Our findings open up a novel approach for local delivery of therapeutically active proteins to tumors and, potentially, other diseases.

Two distinct mechanisms of augmented antitumor activity by modulation of immunostimulatory/inhibitory signals

PURPOSE

Blockade of CTL-associated antigen-4 (CTLA-4), an inhibitory immunomodulatory molecule on T cells, has been shown to enhance T-cell responses and induce tumor rejection, and a number of clinical trials with anti-CTLA-4 blocking monoclonal antibody (mAb) are under way. However, accumulating evidence indicates that anti-CTLA-4 mAb increases the number of CD4+CD25+Foxp3+ regulatory T cells (Treg) and that anti-CTLA4 mAb alone is often insufficient to reject established tumors in mice and humans. Thus, finding maneuvers to control Tregs and other immunosuppressive mechanisms remains a critical challenge.

EXPERIMENTAL DESIGN

The potential to enhance antitumor immune responses by combining anti-CTLA-4 mAb with anti-glucocorticoid-induced tumor necrosis factor receptor family related gene (GITR) mAb, a costimulatory molecule that abrogates directly/indirectly Treg-mediated immune suppression or anti-CD25 mAb that depletes Tregs was analyzed with two tumor models, CT26 (a murine colon carcinoma cell line) and CMS5a (a murine fibrosarcoma cell line).

RESULTS

Anti-CTLA-4/anti-GITR mAb combination treatment exhibited far stronger antitumor effects compared with either antibody alone. This strong antitumor effect was attributed to (a) increased numbers of CD8+ T cells infiltrating tumor sites in anti-CTLA-4 mAb-treated mice and (b) increased cytokine secretion and Treg resistance of tumor-specific CD8+ T cells with strongly upregulated CD25 expression in anti-GITR mAb-treated mice, indicating distinct quantitative/qualitative changes induced by modulating CTLA-4 and GITR signaling.

CONCLUSIONS

This study shows that combined treatment with different immune modulators can augment antitumor immune responses and provides justification for exploring anti-CTLA-4/anti-GITR mAb combination treatment in the clinic.

Slow down and survive: Enigmatic immunoregulation by BTLA and HVEM

B and T lymphocyte associated (BTLA) is an Ig domain superfamily protein with cytoplasmic immunoreceptor tyrosine-based inhibitory motifs. Its ligand, herpesvirus entry mediator (HVEM), is a tumor necrosis factor receptor superfamily member. The unique interaction between BTLA and HVEM allows for a system of bidirectional signaling that must be appropriately regulated to balance the outcome of the immune response. HVEM engagement of BTLA produces inhibitory signals through SH2 domain-containing protein tyrosine phosphatase 1 (Shp-1) and Shp-2 association, whereas BTLA engagement of HVEM produces proinflammatory signals via activation of NF-kappaB. The BTLA-HVEM interaction is intriguing and quite complex given that HVEM has four other ligands that also influence immune responses, the conventional TNF ligand LIGHT and lymphotoxin alpha, as well as herpes simplex virus glycoprotein D and the glycosylphosphatidylinositol-linked Ig domain protein CD160. BTLA-HVEM interactions have been shown to regulate responses in several pathogen and autoimmune settings, but our understanding of this complex system of interactions is certainly incomplete. Recent findings of spontaneous inflammation in BTLA-deficient mice may provide an important clue.

Targeting cytotoxic T-lymphocyte antigen 4 in immunotherapies for melanoma and other cancers

The immune system can simultaneously protect against tumor growth and sculpt resistant tumor strains. By a variety of mechanisms, anti-cytotoxic T-lymphocyte antigen (CTLA)-4 therapy may shift such opposing forces towards tumor elimination. In recent clinical trials, anti-CTLA-4 therapy induces durable responses that correlate with markers of immune activity, such as antigen-specific CD4+ or CD8+ cytokine release, antitumor antibody formation or cellular phenotype differentiation. However, some patients exhibit atypical responses to anti-CTLA-4 therapy, demonstrating transient/delayed responses or heterogeneity by lesion site. Such atypical responses may offer insight into the mechanism of anti-CTLA-4 therapy. The immunogram – a newly described graphical synthesis of treatment data and immune correlates in individual patients – may help us to confirm, reject or formulate new hypotheses regarding the mechanism of anti-CTLA-4 activity.

Regulatory T cells in cancer

At the present time, regulatory T cells (Tregs) are an integral part of immunology but the route from discovery of "suppressive" lymphocytes in the 1980s to the current established concept of Tregs almost 20 years later has been a rollercoaster ride. Tregs are essential for maintaining self-tolerance as defects in their compartment lead to severe autoimmune diseases. This vitally important function exists alongside the detrimental effects on tumor immunosurveillance and antitumor immunity. Beginning with the identification of CD4(+)CD25(+) Tregs in 1995, the list of Treg subsets, suppressive mechanisms, and knowledge about their various origins is steadily growing. Increase in Tregs within tumors and circulation of cancer patients, observed in early studies, implied their involvement in pathogenesis and disease progression. Several mechanisms, ranging from proliferation to specific trafficking networks, have been identified to account for their systemic and/or local accumulation. Since various immunotherapeutic approaches are being utilized for cancer therapy, various strategies to overcome the antagonistic effects exerted by Tregs are being currently explored. An overview on the biology of Tregs present in cancer patients, their clinical impact, and methods for modulating them is given in this review. Despite the extensive studies on Tregs in cancer many questions still remain unanswered. Even the paradigm that Tregs generally are disadvantageous for the control of malignancies is now under scrutiny. Insight into the specific role of Tregs in different types of neoplasias is the key for targeting them in a way that is beneficial for the clinical outcome.

Immuno- and gene-therapeutic strategies targeted against cancer (mainly focusing on pancreatic cancer)

Current treatment modalities of surgical resection and chemotherapy against cancers have improved survival. However, mortality from tumor recurrence remains high. Immunotherapy and gene therapy are potential additions to the treatment arsenal in the care of cancer patients. These novel therapeutic approaches need further investigation in in vitro and in vivo models as they are developed for potential use in humans. Here we reviewed immunotherapies and gene therapies that included clinical trials against cancers (mainly focusing on pancreatic cancer) suggesting the strong possibility of using these novel approaches.

Combination of CTL-associated antigen-4 blockade and depletion of CD25 regulatory T cells enhance tumour immunity of dendritic cell-based vaccine in a mouse model of colon cancer

Immune regulation has been shown to be involved in the progressive growth of some murine tumours. Interruption of immune regulatory pathways via CTL-associated antigen-4 (CTLA-4) blockade or removal of CD4(+) CD25(+) regulatory T (Treg) cells appears to be a promising strategy for cancer immunotherapy. In this study, we tested the hypothesis that the combination of CTLA-4 blockade and depletion of Treg cells would improve the potency of dendritic cell (DC)-based vaccine in a clinically relevant mouse model, which is transgenic for both carcinoembryonic antigen (CEA) and HLA-A2 for the treatment of colon carcinoma in a therapeutic setting. We found that administration of anti-CD25 antibody prior to vaccination or systemic administration of anti-CTLA-4 antibody with the vaccine improved tumour-free survival against CEA-expressing tumours compared with mice immunized with DC-based vaccine alone. However, the efficacy of the vaccine proved to be most effective when anti-CTLA-4 antibody was combined with Treg inhibition. This vaccination strategy dramatically improved the tumour-free survival and allowed the development of long-lasting immune responses. The combined vaccination strategy resulted in increased secretion of IFN-gamma and enhanced HLA-A2-restricted CEA-specific CTL responses. Furthermore, coadministration of anti-CD25 and anti-CTLA-4 antibodies along with the vaccine was effective against more advanced tumours. These results provide evidence that simultaneous blockade of T-cell regulatory pathways is a promising approach for the induction of therapeutic antitumour immunity against CEA(+) colon carcinoma.

Radiotherapy enhances antitumor effect of anti-CD137 therapy in a mouse Glioma model

Previously, we reported that peripheral vaccination of mice with modified autologous tumor cells secreting granulocyte-macrophage colony-stimulating factor (GM-CSF) combined with ionizing radiation to the whole brain cured 50% of mice using a syngeneic, intracranial model of murine high-grade glioma. Here, we tested the combination of radiotherapy (4 Gy x 2) with an immunotherapeutic approach using an anti-CD137 antibody directed to the co-stimulatory molecule CD137. The CD137 antibody has shown promise in generating effective antitumor responses in several animal models and has demonstrated a favorable toxicity profile in the clinic. The combination of radiation and anti-CD137 therapy resulted in complete tumor eradication and prolonged survival in six of nine (67%) mice with established brain tumors (P = 0.0009). Five of six (83%) long-term survivors in the combination group demonstrated antitumor immunity by rejecting challenge tumors. Antitumor immunity was associated with an increased number of tumor-infiltrating lymphocytes (TILs) in brain tumors and increased tumor-specific production of gammaIFN. In view of the finding that radiation enhanced the antitumor effect of anti-CD137 therapy, this approach should be studied further for clinical translation.

Combination therapy of established tumors by antibodies targeting immune activating and suppressing molecules

The blockade of immune suppression against antitumor responses is a particularly attractive strategy when combined with agents that promote tumor-specific CTLs. In this study, we have attempted to further improve the CTL induction and potent antitumor efficacy of a combination mAb-based therapy (termed "trimAb therapy") that comprises tumor cell death-inducing anti-death receptor 5 mAb and immune activating anti-CD40 and anti-CD137 mAbs. Among trimAb-treated tumors, the infiltration of CD4(+) Foxp3(+) cells was greater in progressing tumors compared with stable tumors. Blockade of CTLA-4 (CD152)-mediated signals by an antagonistic mAb substantially increased the tumor rejection rate of trimAb therapy, although the immune responses of draining lymph node cells were not augmented. Interestingly, by comparison, additional treatment with agonistic anti-glucocorticoid-induced TNF receptor mAb, antagonistic anti-programmed death-1 (CD279) mAb, or agonistic anti-OX40 (CD134) mAb significantly augmented immune responses of draining lymph node cells, but did not augment the therapeutic effect of trimAb. CD4 T cell depletion reduced the antitumor effect of anti-CTLA-4 mAb treatment alone, but did not reduce the tumor rejection rate of trimAb in conjunction with anti-CTLA-4 mAb. Thus, the blockade of the CTLA-4-mediated inhibitory signal in tumor infiltrating CTL may be the most effective strategy to augment the effect of immune therapies that generate tumor-specific CTL.

3-Methylcholanthrene-induced transforming growth factor-beta-producing carcinomas, but not sarcomas, are refractory to regulatory T cell-depletion therapy

Regulatory T cells (Tregs) are major immunosuppressors in tumor-bearing hosts. Although Treg-depletion therapy has been shown to induce a complete cure in tumor-bearing mice, this treatment is not always successful. Using 3-methylcholanthrene-induced primary mouse tumors, we examined the distinct regulation of Treg-mediated immunosuppression between carcinomas and sarcomas. We showed that the number of Tregs was greatly increased in squamous cell carcinoma (SCC)-bearing mice compared with sarcoma-bearing mice. This appeared to be because SCC produced higher levels of active transforming growth factor (TGF)-beta, which is essential for inducing Tregs, compared with sarcoma. Moreover, SCC, but not sarcomas, were refractory to Treg-depletion therapy by treatment with anti-CD25 mAb. The refractoriness of SCC against Treg-depletion therapy was due to the rapid recovery of Tregs in SCC-bearing mice compared with sarcoma-bearing mice. However, combination treatment of anti-TGF-beta mAb with anti-CD25 mAb caused a significant reduction in Treg recovery and induced a complete cure in SCC-bearing mice. Thus, we showed the refractoriness of mouse carcinoma against Treg-depletion therapy using anti-CD25 mAb treatment. We also proposed a novel Treg-blocking combination therapy using anti-CD25 mAb and anti-TGF-beta mAb to induce a complete cure of tumor-bearing hosts.

Polymorphisms in genes of interleukin 12 and its receptors and their association with protection against severe malarial anaemia in children in western Kenya

Background

Malarial anaemia is characterized by destruction of malaria infected red blood cells and suppression of erythropoiesis. Interleukin 12 (IL12) significantly boosts erythropoietic responses in murine models of malarial anaemia and decreased IL12 levels are associated with severe malarial anaemia (SMA) in children. Based on the biological relevance of IL12 in malaria anaemia, the relationship between genetic polymorphisms of IL12 and its receptors and SMA was examined.

Methods

Fifty-five tagging single nucleotide polymorphisms covering genes encoding two IL12 subunits, IL12A and IL12B, and its receptors, IL12RB1 and IL12RB2, were examined in a cohort of 913 children residing in Asembo Bay region of western Kenya.

Results

An increasing copy number of minor variant (C) in IL12A (rs2243140) was significantly associated with a decreased risk of SMA (P = 0.006; risk ratio, 0.52 for carrying one copy of allele C and 0.28 for two copies). Individuals possessing two copies of a rare variant (C) in IL12RB1 (rs429774) also appeared to be strongly protective against SMA (P = 0.00005; risk ratio, 0.18). In addition, children homozygous for another rare allele (T) in IL12A (rs22431348) were associated with reduced risk of severe anaemia (SA) (P = 0.004; risk ratio, 0.69) and of severe anaemia with any parasitaemia (SAP) (P = 0.004; risk ratio, 0.66). In contrast, AG genotype for another variant in IL12RB1 (rs383483) was associated with susceptibility to high-density parasitaemia (HDP) (P = 0.003; risk ratio, 1.21).

Conclusions

This study has shown strong associations between polymorphisms in the genes of IL12A and IL12RB1 and protection from SMA in Kenyan children, suggesting that human genetic variants of IL12 related genes may significantly contribute to the development of anaemia in malaria patients.

Vaccines against human carcinomas: strategies to improve antitumor immune responses

Multiple observations in preclinical and clinical studies support a role for the immune system in controlling tumor growth and progression. Various components of the innate and adaptive immune response are able to mediate tumor cell destruction; however, certain immune cell populations can also induce a protumor environment that favors tumor growth and the development of metastasis. Moreover, tumor cells themselves are equipped with various mechanisms that allow them to evade surveillance by the immune system. The goal of cancer vaccines is to induce a tumor-specific immune response that ultimately will reduce tumor burden by tipping the balance from a protumor to an antitumor immune environment. This review discusses common mechanisms that govern immune cell activation and tumor immune escape, and some of the current strategies employed in the field of cancer vaccines aimed at enhancing activation of tumor-specific T-cells with concurrent reduction of immunosuppression.

Variable number of tandem repeat polymorphisms of the interleukin-1 receptor antagonist gene IL-1RN: a novel association with the athlete status

BACKGROUND

The interleukin-1 (IL-1) family of cytokines is involved in the inflammatory and repair reactions of skeletal muscle during and after exercise. Specifically, plasma levels of the IL-1 receptor antagonist (IL-1ra) increase dramatically after intense exercise, and accumulating evidence points to an effect of genetic polymorphisms on athletic phenotypes. Therefore, the IL-1 family cytokine genes are plausible candidate genes for athleticism. We explored whether IL-1 polymorphisms are associated with athlete status in European subjects.

METHODS

Genomic DNA was obtained from 205 (53 professional and 152 competitive non-professional) Italian athletes and 458 non-athlete controls. Two diallelic polymorphisms in the IL-1beta gene (IL-1B) at -511 and +3954 positions, and a variable number tandem repeats (VNTR) in intron 2 of the IL-1ra gene (IL-1RN) were assessed.

RESULTS

We found a 2-fold higher frequency of the IL-1RN 1/2 genotype in athletes compared to non-athlete controls (OR = 1.93, 95% CI = 1.37-2.74, 41.0% vs. 26.4%), and a lower frequency of the 1/1 genotype (OR = 0.55, 95% CI = 0.40-0.77, 43.9% vs. 58.5%). Frequency of the IL-1RN 2/2 genotype did not differ between groups. No significant differences between athletes and controls were found for either -511 or +3954 IL-1B polymorphisms. However, the haplotype (-511)C-(+3954)T-(VNTR)2 was 3-fold more frequent in athletes than in non-athletes (OR = 3.02, 95% CI = 1.16-7.87). Interestingly, the IL-1RN 1/2 genotype was more frequent in professional than in non-professional athletes (OR = 1.92, 95% CI = 1.02-3.61, 52.8% vs. 36.8%).

CONCLUSIONS

Our study found that variants at the IL-1ra gene associate with athletic status. This confirms the crucial role that cytokine IL-1ra plays in human physical exercise. The VNTR IL-1RN polymorphism may have implications for muscle health, performance, and/or recovery capacities. Further studies are needed to assess these specific issues. As VNTR IL-1RN polymorphism is implicated in several disease conditions, athlete status may constitute a confounding variable that will need to be accounted for when examining associations of this polymorphism with disease risk.

Role of vaccine therapy in cancer: biology and practice

Vaccines constitute a potential new therapeutic approach for a range of human cancers. Unlike other therapeutics, vaccines initiate a dynamic process in the host immune system that can be exploited with subsequent therapies. Indeed, recent preclinical and clinical studies with cancer vaccines have provided evidence that this unique therapeutic modality should lead to consideration of new paradigms in both clinical trial design and endpoints and in combination therapies. The present article reviews and sets out a rationale for these new paradigms, with a focus on prostate cancer.