Tumor-associated antigen human chorionic gonadotropin beta contains numerous antigenic determinants recognized by in vitro-induced CD8+ and CD4+ T lymphocytes

CDX-1307: a novel vaccine under study as treatment for muscle-invasive bladder cancer

Cancer vaccines have demonstrated clinical benefit, however greater efficacy could be achieved by enhancing their immunogenicity. Owing to cancer vaccines depending on uptake and cross-presentation of tumor antigens by antigen-presenting cells (APCs), we hypothesized that greater immunogenicity would accompany strategies that direct antigen to APC-expressed mannose receptors, initiating a pathway increasing class I and II presentation to T cells. CDX-1307 consists of a human monoclonal antibody targeting the mannose receptor, fused to the human chorionic gonadotropin-β chain (hCG-β), a tumor antigen frequently expressed by epithelial cancers including bladder cancer. In Phase I studies of cancer patients, CDX-1307 was well tolerated and induced significant hCG-β-specific cellular and humoral immune responses when co-administered with GM-CSF and the Toll-like receptor agonists resiquimod and poly-ICLC. An ongoing Phase II trial evaluates CDX-1307 in patients with newly diagnosed, resectable, hCG-β-expressing bladder cancer, where low tumor burden and early intervention may provide greater potential for benefit.

Phase I study utilizing a novel antigen-presenting cell-targeted vaccine with Toll-like receptor stimulation to induce immunity to self-antigens in cancer patients

PURPOSE

The use of tumor-derived proteins as cancer vaccines is complicated by tolerance to these self-antigens. Tolerance may be broken by immunization with activated, autologous, ex vivo generated and antigen-loaded, antigen-presenting cells (APC); however, targeting tumor antigen directly to APC in vivo would be a less complicated strategy. We wished to test whether targeted delivery of an otherwise poorly immunogenic, soluble antigen to APC through their mannose receptors (MR) would induce clinically relevant immunity.

EXPERIMENTAL DESIGN

Two phase I studies were conducted with CDX-1307, a vaccine composed of human chorionic gonadotropin beta-chain (hCG-β) fused to an MR-specific monoclonal antibody, administered either locally (intradermally) or systemically (intravenously) in patients with advanced epithelial malignancies. An initial dose escalation of single-agent CDX-1307 was followed by additional cohorts of CDX-1307 combined with granulocyte-macrophage colony-stimulating factor (GM-CSF) and the Toll-like receptor (TLR) 3 agonist polyinosinic-polycytidylic acid (poly-ICLC) and TLR7/8 agonist resiquimod to activate the APC.

RESULTS

CDX-1307 induced consistent humoral and T-cell responses to hCG-β when coadministered with TLR agonists. Greater immune responses and clinical benefit, including the longest duration of stable disease, were observed with immunization combined with local TLR agonists. Immune responses were induced equally efficiently in patients with elevated and nonelevated levels of serum hCG-β. Antibodies within the serum of vaccinated participants had tumor suppressive function in vitro. Toxicity consisted chiefly of mild injection site reactions.

CONCLUSIONS

APC targeting and activation induce adaptive immunity against poorly immunogenic self-antigens which has implications for enhancing the efficacy of cancer immunotherapy.

Seasonal variation in detection of bacterial DNA in arthritic stifle joints of dogs with cranial cruciate ligament rupture using PCR amplification of the 16S rRNA gene

An underappreciated cause and effect relationship between environmental bacteria and arthritis may exist. Previously, we found that stifle arthritis in dogs was associated with the presence of environmental bacteria within synovium. Cranial cruciate ligament rupture (CCLR) is often associated with stifle arthritis in dogs. We now wished to determine whether seasonal variation in detection of bacterial material may exist in affected dogs, and to also conduct analyses of both synovium and synovial fluid. We also wished to analyze a larger clone library of the 16S rRNA gene to further understanding of the microbial population in the canine stifle. Synovial biopsies were obtained from 117 affected dogs from January to December 2006. Using PCR, synovium and synovial fluid were tested for Borrelia burgdorferi and Stenotrophomonas maltophilia DNA. Broad-ranging 16S rRNA primers were also used and PCR products were cloned and sequenced for bacterial identification. Overall, 41% of arthritic canine stifle joints contained bacterial DNA. Detection of bacterial DNA in synovial fluid samples was increased, when compared with synovium (p<0.01). Detection rates were highest in the winter and spring and lowest in the summer period, suggesting environmental factors influence the risk of translocation to the stifle. Organisms detected were predominately Gram's negative Proteobacteria, particularly the orders Rhizobiales (32.8% of clones) and Burkholderiales (20.0% of clones), usually as part of a polymicrobial population. PCR-positivity was inversely correlated with severity of arthritis assessed radiographically and with dog age. Bacterial translocation to the canine stifle may be associated with changes to the indoor environment.

The distinct effects of three tandem repeats of C3d in the immune responses against tumor-associated antigen hCGbeta by DNA immunization

Several examples have shown that C3d3, when fused to a corresponding antigen, had a strong adjuvant effect on certain specific antibody production. In a previous study, we attempted to prove that this was the case of the human chorionic gonadotrophin beta chain (hCGbeta)-induced immunity following DNA vaccination. However, we found that C3d3 when fused to hCGbeta inhibited rather than enhanced the antigen-specific immune response. In the present study, using hCGbeta DNA vaccine preparations, we demonstrated that C3d3 inhibited the antigen-specific humoral antibody response and several other immune responses, such as the hCGbeta specific lymphoproliferation. Such inhibitory effects of C3d3 were not related to the expression level of the target protein, the gender of the test mice, or the vector used. Contrastingly, C3d3 fused with the envelope protein of hepatitis B virus (PreS2/S) used as a control system resulted in the enhancement of both humoral and cell-mediated antigen-specific immune responses against HBV-preS2/S, which was consistent with other groups' adjuvant-effect findings. We further showed that the mechanisms involved in the inhibitory effect of C3d3 might be possible due to impairing the function of antigen presenting B lymphocytes and reducing the expression of transcription factors (T-bet and GATA-3) and cytokine IL-4. Collectively, unlike its usual expected adjuvant function, the fusion of C3d3 with the tumor-associated antigen hCGbeta was found to inhibit both humoral and cell-mediated antigen-specific immune responses. These findings indicate that research concerning tumor immune escapes and vaccine designs require further extensive attention.

Immunobiology of gestational trophoblastic diseases

Gestational trophoblastic diseases (GTDs) comprise a group of interrelated diseases characterized by development after gestation, widespread metastases, and high curability with chemotherapy. The good prognosis of GTDs is considered partly a result of the host immune response to paternal antigens expressed on trophoblastic cells. In this study, we review current understanding of the immunobiology of GTDs. First of all, we describe the microenvironment between trophoblastic cells and subpopulation of immune cells. Second, immunogenetics, immune microenvironment around abnormal trophoblast, and mechanism of GTDs escaping from maternal immune system surveillance were also discussed. Third, we propose the possible immunotherapy for persistent GTDs, particularly the vaccine designed on human chorionic gonadotrophin, which is generally accepted as a tumor marker for GTDs diagnosis. Due to the low incidence of GTDs and high response to chemotherapy, there have been few literatures about immunobiologic characteristics of GTDs compared with the other gynecologic malignancies, such as ovarian cancer, but the immunologic behavior of GTDs should be explored for further understanding of the etiology of these diseases and to help designing immunotherapeutic strategies for persistent GTDs.

Antibody Targeting to a Class I MHC-Peptide Epitope Promotes Tumor Cell Death

Therapeutic mAbs that target tumor-associated Ags on the surface of malignant cells have proven to be an effective and specific option for the treatment of certain cancers. However, many of these protein markers of carcinogenesis are not expressed on the cells' surface. Instead these tumor-associated Ags are processed into peptides that are presented at the cell surface, in the context of MHC class I molecules, where they become targets for T cells. To tap this vast source of tumor Ags, we generated a murine IgG2a mAb, 3.2G1, endowed with TCR-like binding specificity for peptide-HLA-A*0201 (HLA-A2) complex and designated this class of Ab as TCR mimics (TCRm). The 3.2G1 TCRm recognizes the GVL peptide (GVLPALPQV) from human chorionic gonadotropin beta presented by the peptide-HLA-A*0201 complex. When used in immunofluorescent staining reactions using GVL peptide-loaded T2 cells, the 3.2G1 TCRm specifically stained the cells in a peptide and Ab concentration-dependent manner. Staining intensity correlated with the extent of cell lysis by complement-dependent cytotoxicity (CDC), and a peptide concentration-dependent threshold level existed for the CDC reaction. Staining of human tumor lines demonstrated that 3.2G1 TCRm was able to recognize endogenously processed peptide and that the breast cancer cell line MDA-MB-231 highly expressed the target epitope. The 3.2G1 TCRm-mediated CDC and Ab-dependent cellular cytotoxicity of a human breast carcinoma line in vitro and inhibited in vivo tumor implantation and growth in nude mice. These results provide validation for the development of novel TCRm therapeutic reagents that specifically target and kill tumors via recognition and binding to MHC-peptide epitopes.

Expression of MG7-Ag in patients with gastric cancer correlates with weaker T cell immune response and more proinflammatory cytokine secretion

MG7-Ag is a human gastric-carcinoma-associated antigen with a high specificity. So far it is remained unclear whether MG7-Ag is correlated with the in vivo cellular immune response of patients with gastric cancer. In this study, we detected the expression of the T cell receptor (TCR) repertoire of T cell subpopulations and cytokines in tumor-infiltrating lymphocytes (TIL), peripheral blood lymphocytes (PBL), and residue benign mucosal lymphocytes (NML) of patients with gastric cancer using semiquantitative RT-PCR. Our data showed that the expanded clones in CD8(+) NML and TIL and CD4+ NML and PBL in MG7-Ag-positive patients were significantly fewer than those of MG7-Ag-negative patients (p = 0.0360; p = 0.0026; p = 0.0065 p = 0.0109, respectively). The levels of IL-8 in CD8(+) TIL and TNF in CD4(+) TIL from the MG7-Ag-positive group were significantly higher than those from the MG7-Ag-negative group (p = 0.0302; p = 0.0177, respectively). Taken together, the results demonstrated a weaker T cell immune response and more proinflammatory cytokine secretion in MG7-Ag-positive patients with gastric cancer than in MG7-Ag-negative ones. This likely contributes to the poor prognosis in MG7-Ag-positive gastric-cancer patients.

Ten tandem repeats of beta-hCG 109-118 enhance immunogenicity and anti-tumor effects of beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65

The beta-subunit of human chorionic gonadotropin (beta-hCG) is secreted by many kinds of tumors and it has been used as an ideal target antigen to develop vaccines against tumors. In view of the low immunogenicity of this self-peptide,we designed a method based on isocaudamer technique to repeat tandemly the 10-residue sequence X of beta-hCG (109-118), then 10 tandemly repeated copies of the 10-residue sequence combined with beta-hCG C-terminal 37 peptides were fused to mycobacterial heat-shock protein 65 to construct a fusion protein HSP65-X10-betahCGCTP37 as an immunogen. In this study, we examined the effect of the tandem repeats of this 10-residue sequence in eliciting an immune by comparing the immunogenicity and anti-tumor effects of the two immunogens, HSP65-X10-betahCGCTP37 and HSP65-betahCGCTP37 (without the 10 tandem repeats). Immunization of mice with the fusion protein HSP65-X10-betahCGCTP37 elicited much higher levels of specific anti-beta-hCG antibodies and more effectively inhibited the growth of Lewis lung carcinoma (LLC) in vivo than with HSP65-betahCGCTP37, which should suggest that HSP65-X10-betahCGCTP37 may be an effective protein vaccine for the treatment of beta-hCG-dependent tumors and multiple tandem repeats of a certain epitope are an efficient method to overcome the low immunogenicity of self-peptide antigens.

The mouse chorionic gonadotropin beta-subunit-like (muCG beta l) molecule produced by tumor cells elicits the switch of T-cell immunity response from TH2 to TH1 in mice immunized with DNA vaccine based on rhesus monkey homologous CG beta (rmCG beta)

BACKGROUND

CG beta is expressed not only in placenta, but also in a wide range of tumors. To study DNA vaccine based on xenogeneic CG beta for cancer immuno-therapy, we investigated whether rhesus monkey CG beta (rmCG beta) DNA vaccine could induce protective T-cell responses and humoral responses in mouse.

METHODS

We constructed a plasmid containing the rmCG beta coding sequence. Two cloned syngeneic SP2/0 myeloma cell lines that stably express muCG beta l (SP2/0-muCG beta l) and HN (SP2/0-HN) protein were established. Inoculation of these cell lines was made into mice that had been immunized with DNA vaccine. Specific IgG and IgG type were measured by ELISA and the cytokine expression was detected with RT-PCR. To measure the lymphocyte metabolic activity, the MTS assay was used.

RESULTS

After injection of SP2/0-muCG beta l into mice that had been immunized with DNA vaccine, a significant increase in the IgG2a specific to the antigen (p < 0.05) and a decrease in the specific IgG1 (p < 0.05) were measured. The expression of T(H)1 but not T(H)2 cytokines, including IFN-gamma and IL-2, were detected in the splenocytes. However, injection of tumor cells expressing irrelevant or mock molecules into immunized mice could not induce these changes. The survival rate of vaccine-immunized mice injected with SP2/0-muCG beta l was as high as 58.3% after 55 days.

CONCLUSIONS

The rmCG beta DNA vaccine has proved to be a potential strategy for protection against tumors with homologous molecules. The muCG beta l produced by tumors is able to elicit an immunity switch from T(H)2 to T(H)1 in vaccinated mice.

A Novel Human Cancer Vaccine Elicits Cellular Responses to the Tumor-Associated Antigen, Human Chorionic Gonadotropin β

PURPOSE

The oncofetal antigen, human chorionic gonadotropin beta subunit (hCGbeta), is expressed by a number of carcinomas and is a prognostic indicator in renal, colorectal, bladder, and pancreatic cancers. We describe the development of a novel antibody-based dendritic cell (DC)-targeted cancer vaccine capable of eliciting cellular immune responses directed against hCGbeta.

EXPERIMENTAL DESIGN

The tumor-associated antigen hCGbeta was coupled genetically to a human anti-DC antibody (B11). The resulting fusion protein (B11-hCGbeta) was evaluated for its ability to promote tumor antigen-specific cellular immune responses in a human in vitro model. Monocyte-derived human DCs from normal donors were exposed to purified B11-hCGbeta, activated with CD40 ligand, mixed with autologous lymphocytes, and tested for their ability to promote hCGbeta-specific proliferative and cytotoxic T-lymphocyte responses.

RESULTS

B11-hCGbeta was found to be a soluble, well-defined, and readily purified product that specifically recognized the human mannose receptor via the B11 antibody portion of the fusion protein. B11-hCGbeta functionally promoted the uptake and processing of tumor antigen by DCs, which led to the generation of tumor-specific HLA class I and class II-restricted T-cell responses, including CTLs capable of killing human cancer cell lines expressing hCGbeta.

CONCLUSIONS

Although other hCG vaccines have been shown to be capable of eliciting antibody responses to hCGbeta, this is the first time that cellular immune responses to hCGbeta have been induced by a vaccine in a human system. This DC-targeted hCGbeta vaccine holds promise for the management of a number of cancers and merits additional clinical development.

Enhancement of Immunogenicity of Jeg3 Cells by Ectopic Expression of HLA-A*0201 and CD80

PROBLEM

The choriocarcinoma cell line Jeg3 suppresses immunity in vitro by secretion of soluble factors like leukemia inhibitory factor suppressing leukocyte activation. The cells lack expression of classical human leukocyte antigen (HLA)-A and -B alleles but express some HLA-C, and non-classical HLA-G and -E. Upon binding to killing inhibitory receptor on natural killer (NK) cells, HLA-G prevents activation of cytolytic activity. We investigated whether Jeg3 cells are capable of immune stimulation after complementation with classical HLA and T cell costimulatory signal CD80.

METHOD OF STUDY

Jeg3 cells were transduced to express HLA-A*0201 and/or CD80. Parental Jeg3 or transfectants Jeg3-A2, Jeg3-CD80 or Jeg3-CD80-A2 were used to stimulate allogeneic resting and activated peripheral blood lymphocytes (PBL). The different cell lines were loaded with a HLA-A2-restricted Epstein-Barr virus (EBV) recall antigen peptide epitope and antigen presenting ability was examined. T cell lines specific for Jeg3 and transfectants were generated from HLA-A2 matched and nonmatched donors and compared for expansion, phenotypes and cytolytic activity.

RESULTS

While all Jeg3 cell lines induced only marginal proliferation of resting T cells, phytohemagglutinin (PHA)-activated T cells were stimulated by CD80 or CD80-A2 expressing Jeg3. Only the transfectant Jeg3-CD80-A2 was capable of specific T cell stimulation by EBV recall antigen presentation. T cell lines of HLA-A2 non-matched donors stimulated with the Jeg3 transfectants showed significant expansion only when HLA-A2 and the costimulus CD80 were present. T cells from HLA-A2 positive donors did not expand significantly or differentially. No NK cells grew under any condition. In Jeg3-CD80-A2 stimulated T cells lines CD8+ cells expanded preferentially. These T cells exerted cytolytic activity toward all Jeg3 cell lines.

CONCLUSION

Our data suggest that, in spite of immunosuppressive mechanisms, proliferative and cytolytic T cell responses are induced by Jeg3 cells when classical HLA- and/or costimulatory signals are present on the cells.