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

Development of cancer vaccines to activate cytotoxic T lymphocytes

Cancer vaccines have been shown to stimulate cytotoxic T lymphocyte (CTL) responses in a variety of cancer patients. However, the response is often of low frequency and moderate avidity, and does not result in objective clinical responses. This is related to the target antigens, which are usually over-expressed self-antigens that elicit tolerogenic and regulatory immune responses, resulting in deletion or inactivation of high-avidity T cells. Although moderate-avidity T cells can be efficient killers, tumours are often poor targets as they express a variety of molecules to protect them from cell-mediated immunity. Adoptive transfer of large numbers of high-avidity T cells has been shown to induce regression of bulky disease, proving that immune responses can effectively eradicate tumours. New approaches that target activated dendritic cells in vivo, resulting in cross-presentation of CTL epitopes and release of cytokines that suppress regulatory T cells, have resulted in the production of T cells with sufficient avidity to kill tumour target cells. These approaches in combination with regimes, such as cytokine therapy, chemotherapy or radiotherapy, that modulate effector costimulatory expression on tumour targets may result in more effective second-generation cancer vaccines.

Preoperative Serum hCGβ as a Prognostic Marker in Primary Fallopian Tube Carcinoma

OBJECTIVES

It was the aim of this study to evaluate the prognostic value of the pretreatment serum concentrations of the beta-subunit of human chorionic gonadotropin (hCGbeta), CA 125 and tumour-associated trypsin inhibitor (TATI) in primary fallopian tube carcinoma (PFTC).

METHODS

The pretreatment serum concentrations of hCGbeta, CA 125 and TATI were analyzed in serum samples from 60 women with a mean age of 61 years, treated for PFTC between 1985 and 2000. Of the 91 patients treated during this period, 31 were excluded because no serum sample was available. The patients were followed-up for recurrence and survival until February 14, 2003. The prognostic value of the serum markers were compared with those of stage, grade and histological type.

RESULTS

The median survival time was 27 months and the overall 5-year survival rate 33%. Stage and size of the residual tumour (<1 vs. > or =1 cm) predicted both overall and disease-free survival (p < 0.050). Histology (serous vs. others) (p = 0.023) also influenced overall survival. Overall 5-year survival was 38% when serum hCGbeta was below 3.5 pmol/l, while it was 18% when the level was higher (p = 0.052). The corresponding disease-free 5-year survival was 38 and 20%, respectively (p = 0.014). Patients with CA 125 values above 1,017 kU/l had an overall 5-year survival of 39% as compared with 14% for those with lower values (p = 0.009), while the disease-free survival was 37 and 23%, respectively (p = 0.096). Serum TATI was not a prognostic marker. Serum concentrations of hCGbeta and CA 125 correlated significantly with stage (p = 0.049 and p = 0.050, respectively). In multivariate Cox proportional hazards regression analysis, only hCGbeta, stage and histology emerged as independent prognostic factors.

CONCLUSIONS

Clearly elevated serum concentrations of hCGbeta and CA 125 predict survival in fallopian tube carcinoma, but in multivariate analyses, only hCGbeta is a prognostic factor independent of stage and histology.

Using antibodies in tumour immunotherapy

The role of antibodies as therapeutic cancer vaccines includes two distinct approaches, which are summarised in this review, namely anti-idiotypic vaccines and antigen-antibody complex therapies. Bispecific antibodies directed against T cells or antigen-presenting cells are also referenced. The report focuses on theoretical issues, laboratory data on the mechanism of action, examples of humoral and cellular immune induction, and novel therapeutic advances in vaccine development. The biology of antigen processing and recent advances in the field of dendritic cell biology are critical to understanding the potent immune response induction. Future directions include combination therapies to manipulate immune regulatory mechanisms and to enhance clinical effects. Additional applications of antibodies targeting costimulatory or regulatory receptors on antigen-presenting cells and T cells, neutralising immune suppressive cytokines, and depleting T regulatory cells hold promise for future mono- and particularly combination therapies.

Effective induction of naive and recall T-cell responses by targeting antigen to human dendritic cells via a humanized anti-DC-SIGN antibody

Current dendritic cell (DC)-based vaccines are based on ex vivo-generated autologous DCs loaded with antigen prior to readministration into patients. A more direct and less laborious strategy is to target antigens to DCs in vivo via specific surface receptors. Therefore, we developed a humanized antibody, hD1V1G2/G4 (hD1), directed against the C-type lectin DC-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) to explore its capacity to serve as a target receptor for vaccination purposes. hD1 was cross-linked to a model antigen, keyhole limpet hemocyanin (KLH). We observed that the chimeric antibody-protein complex (hD1-KLH) bound specifically to DC-SIGN and was rapidly internalized and translocated to the lysosomal compartment. To determine the targeting efficiency of hD1-KLH, monocyte-derived DCs and peripheral blood lymphocytes (PBLs) were obtained from patients who had previously been vaccinated with KLH-pulsed DCs. Autologous DCs pulsed with hD1-KLH induced proliferation of patient PBLs at a 100-fold lower concentration than KLH-pulsed DCs. In addition, hD1-KLH-targeted DCs induced proliferation of naive T cells recognizing KLH epitopes in the context of major histocompatibility complex (MHC) classes I and II. We conclude that antibody-mediated targeting of antigen to DCs via DC-SIGN effectively induces antigen-specific naive as well as recall T-cell responses. This identifies DC-SIGN as a promising target molecule for DC-based vaccination strategies.

The mannose receptor is expressed by subsets of APC in non-lymphoid organs

BACKGROUND

The mannose receptor (MR) is an endocytic receptor of Mphi and endothelial cell subsets whose natural ligands include both self glycoproteins and microbial glycans. It is also expressed by immature cultured dendritic cells (DC), where it mediates high efficiency uptake of glycosylated antigens, yet its role in antigen handling in vivo is unknown. Knowledge of which APC subsets express MR will assist the design of experiments to address its immunological functions. Here the expression of MR by MHC class II positive APC in non-lymphoid organs of the mouse is described.

RESULTS

MR positive APC were identified in several peripheral organs: skin, liver, cardiac and skeletal muscle and tongue. MR positive cells in salivary gland, thyroid and pancreas coexpressed MHC class II and the myeloid markers macrosialin and sialoadhesin, but not the dendritic cell markers CD11c or DEC-205. MR and MHC class II colocalised in confocal microscope images, implying that antigen capture may be the primary role of MR in these cells. Distinct ligands of MR were found in salivary gland and pancreas tissue lysates that are candidate physiological ligands of MR positive APC in these organs.

CONCLUSIONS

The tissue and subcellular distribution of MR suggest it is appropriately located to serve as a high efficiency antigen uptake receptor of APC.