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Differentiation of cytolytic T cells can be supported by type I and type II interferons (IFN). To characterize the role of type I interferons further we tested the role of recombinant IFN-alpha and IFN-beta on the induction of a weak immune response, against a low immunogenic tumor, which has been shown to be increased by IFN. Both type I interferons IFN-alpha and IFN-beta were able to support the differentiation of cytolytic T lymphocytes (CTL). In case of IFN-alpha no correlation with the antiviral activity could be seen by comparison of IFN-alpha1 and IFN-alpha4. The maximal in vitro effects were achieved with very low concentrations in the range of 1-100 IU/ml. IFN-alpha showed the strongest effects, if added in the early phase of the mixed leukocyte culture, whereas IFN-beta was most effective when given at the last day the culture. In combination, both IFNs gave additional/synergistic effects, whereby addition of IFN-alpha at day 0 and IFN-beta at day 4 led to maximal specific CTL responses. In vivo augmentation of the anti-tumor immune response by both types of IFNs supported the in vitro findings and also the synergistic effect of both types of IFNs could be demonstrated. Therefore we propose that IFN-alpha is relevant in the induction of CTL responses, i.e., the conversion of precursor T cell into mature cells and growth promotion whereby IFN-beta might trigger the lytic machinery of the cells and promote differentiation. This synergistic efficacy is also operative in tumor rejection.

Scientific discoveries that provide strong evidence of antitumor effects in preclinical models often encounter significant delays before being tested in patients with cancer. While some of these delays have a scientific basis, others do not. We need to do better. Innovative strategies need to move into early stage clinical trials as quickly as it is safe, and if successful, these therapies should efficiently obtain regulatory approval and widespread clinical application. In late 2009 and 2010 the Society for Immunotherapy of Cancer (SITC), convened an "Immunotherapy Summit" with representatives from immunotherapy organizations representing Europe, Japan, China and North America to discuss collaborations to improve development and delivery of cancer immunotherapy. One of the concepts raised by SITC and defined as critical by all parties was the need to identify hurdles that impede effective translation of cancer immunotherapy. With consensus on these hurdles, international working groups could be developed to make recommendations vetted by the participating organizations. These recommendations could then be considered by regulatory bodies, governmental and private funding agencies, pharmaceutical companies and academic institutions to facilitate changes necessary to accelerate clinical translation of novel immune-based cancer therapies. The critical hurdles identified by representatives of the collaborating organizations, now organized as the World Immunotherapy Council, are presented and discussed in this report. Some of the identified hurdles impede all investigators; others hinder investigators only in certain regions or institutions or are more relevant to specific types of immunotherapy or first-in-humans studies. Each of these hurdles can significantly delay clinical translation of promising advances in immunotherapy yet if overcome, have the potential to improve outcomes of patients with cancer. © 2011 Fox et al; licensee BioMed Central Ltd.

This study demonstrates that a syngeneic specific cytotoxic T lymphocyte (CTL) response to a class I major histocompatibility complex (MHC) positive tumour requires dual processing and recognition of tumour antigens. One type of antigen is processed and expressed in association with class I MHC at the surface of intact tumour cells. It is recognized by CD8 alpha, beta TCR CTL in vitro and by protective immune T cells in vivo and thus functions as a tumour-associated transplantation antigen (TATA). The other type of antigen is processed and expressed by distinct host APC in association with class II MHC. This is recognized by immune CD4 T cells which function as essential helper cells in the generation of the CD8 CTL response. These conclusions are supported by cell depletion and reconstitution experiments as well as by blocking experiments with monoclonal antibodies using the highly metastatic class II negative murine lymphoma ESb as a model system. The existence of two types of cognate T cell responses in a syngeneic anti-tumour response was directly proved by the establishment of two types of tumour specific T cell lines which required as co-stimulator either MHC class II positive APC or IL-2. In suboptimal mixed lymphocyte tumour cell cultures either of these co-stimulator functions was found to be limiting the overall anti-tumour CTL response. The generation of the tumour specific CTL response could be blocked by monoclonal antibodies against all the molecules involved in the cognate interactions (i.e. class I MHC, CD8, class II MHC, CD4 and TCR) but not by anti-CD2 or anti-IgG. The strict requirement for helper cells and APC could be bypassed by the addition of recombinant IL-2 but optimal triggering of CD8 CTL-precursor required viable tumour stimulator cells. This well characterized in vitro assay may be useful (i) for monitoring the immune status of CD4 and CD8 immune T cells separately, for instance of tumour bearing and/or treated animals and (ii) for the development and testing of potent tumour cell vaccines with T cell stimulatory and/or co-stimulatory activities.

For the optimal delivery of antigens to mucosal tissues, especially as nasal sprays, protein antigen alone is often not sufficient. A clear need for nasal delivery systems has therefore evolved, especially for Influenza A vaccines. Such technologies will be even more essential for new modern vaccines based on recombinant antigens. Here we describe synthetic biomimetic supra molecular Biovector™ (SMBV™) which have proven in preclinical and clinical evaluation to be suitable candidates for the delivery of nasal vaccines. They also demonstrate the potential to work with multiple antigens and furthermore allow combination with adjuvants. These Biovectors can associate with internal or lipid layer membrane proteins and peptides due to their charged polysaccharide core. The mimicry with viruses is also provided through their size of 60–80 nm, which allows sterilization by filtration. This makes them an ideal tool for the development of modern nasal vaccines, as they have shown to be able to induce the desired types of humoral immunity (serosal and mucosal immunity, IgA and IgG antibodies) as well as cellular immunity (CD4 and CD8 responses).

Human immunodeficiency virus type 1 (HIV-1) gp120W61D-specific T cell lines (TCL) were generated from an HIV-1-seronegative volunteer who received rgp120W61D in QS21/MPL adjuvant with emulsion. TCL were challenged with pools of consecutive, overlapping peptides spanning the gp120W61D sequence and then with the individual peptides of the immunostimulatory pool. T cell epitopes were found within both variable and conserved domains, and there was no evidence of a single immunodominant epitope. The two most frequently recognized peptides were located in the C1 domain and in the C-terminal region of the V3 loop. Several TCL were shown to recognize multiple peptides from nonoverlapping regions. Peptides from both conserved and variable domains were capable of inducing MIP-1alpha, MIP-1beta, and RANTES production. When tested against the equivalent peptide from the HIV-1IIIB sequence, however, TCL were able to tolerate only minor conserved changes in the amino acid sequence.

Lymph node and spleen cells of human foetuses from the 18th to the 24th week of gestation were analysed with regard to their phenotypes and their functional capacities. Fetal mesenteric lymph nodes contain high percentages of CD45RA+ T cells and few B cells and monocytes, whereas the fetal spleen is comprised of equal numbers of T and B cells as well as monocytes/macrophages. Functional analysis of lymph node T cells revealed a lack of proliferative response to PHA or CD3 specific mAb, despite induction of expression of the activation marker CD69. Proliferation of LN cells and thymocytes was observed upon addition of exogenous IL-2. An allogeneic EBV transformed tumour cell line, known to be an effective antigen presenting cell, could induce proliferation of LN cells without exogenous IL-2 and fetal spleen cells could proliferate in response to all stimuli tested without additional IL-2. Splenic non-T cells could restore the proliferation of lymph node cells as efficiently as IL-2 or the EBV transformed B cell line. Separated B cells were more effective than plastic adherent cells on a per cell basis. Naivity of the fetal immune system is therefore not only reflected by the expression of markers representative for naive lymphocytes but can also be due to the absence of potential accessory cells in the different lymphoid organs.

Background Humoral immune responses are often the hallmark of efficient vaccines. The recent RV144 vaccine trial has turned attention to the stimulation of humoral immune response as a potential mode of action for HIV vaccines. Therefore, detailed monitoring of antibody reactivities in patient specimens before and after vaccination is crucial. The determination of these reactivities on a sub-protein level provides information on the site of antigen/antibody interaction. In contrast to assays relying on whole antigens such as ELISA, peptide microarrays are efficient tools to deliver such information. Besides, complex peptide libraries can cover HIV sequence diversity, a special challenge provided by this virus.

Previously we described a monoclonal antibody (mAb 12-15) that reacted with murine Fc receptor proteins (beta 1, beta 2 and alpha) and an undefined molecule of 37 kDa (beta 3) on certain types of cells. Here we present serological and biochemical evidence that the beta 3 chain is expressed on mouse thymocytes and that it is identical to the CD2 antigen. By immunofluorescence staining and cytofluorographic analysis greater than 95% of thymocytes were positive. Brightly staining cells coincided with cortisone-resistant thymocytes suggesting that mature thymocytes expressed higher levels of the antigen. Biosynthetic labeling of DBA/2 thymocytes with [35S]methionine showed that the size of the CD2 precursor molecule was 43 kDa which was processed to approximately 55-65 kDa in the mature molecule. mAb 12-15 was also reactive with the tunicamycin-treated form of the CD2 antigen suggesting that the cross-reactive epitope was of protein nature. Comparison of different mouse strains indicated that two molecular forms of CD2 exist. On BALB/c thymocytes, the relative mass of the native molecule was approximately 60-70 kDa (CD2.1) and slightly larger than in DBA/2 (CD2.2). Following endoglycosidase F treatment both proteins still showed a slight difference in electrophoretic mobility. Several inbred mouse strains were analyzed for expression of CD2 forms. When mAb 12-15 was used in cytotoxic T lymphocyte inhibition experiments using specific CTL and tumor target cells it was found that the antibody could specifically inhibit CTL-mediated lysis presumably by interfering with CD2 function.

Augmented tumor-specific T cell responses were observed against the high metastatic murine lymphoma variant ESb when using as immunogen ESb tumor cells that had been modified by infection with a low dose of Newcastle disease virus (NDV). Such virus-modified inactivated tumor cells (ESb-NDV) were potent tumor vaccines when applied postoperatively for active specific immunotherapy of ESb metastases. We demonstrate here that immune spleen cells from mice immunized with ESb-NDV contain enhanced immune capacity in both the CD4+, CD8- and the CD4-, CD8+ T cell compartments to mount a secondary-tumor-specific cytotoxic T cell response in comparison with immune cells from mice immunized with ESb. ESb-NDV immune CD4+, CD8- helper T cells also produced more interleukin 2 after antigen stimulation than the corresponding ESb immune cells. There was no participation of either CD4+ or CD8+ virus-specific cells in the augmented response. The specificity of the T cells for the tumor-associated antigen remained unchanged. Thus, there is the paradox that the virus-mediated augmentation of the tumor-specific T cell response in this system involves increased T helper activity but does not involve the recognition of viral epitopes as potential new helper determinants.

T-cell accessory molecules, particularly CD4 and CD8, seem to be involved in the control of T-cell activation by antigen. Precisely how such molecules operate is not fully understood, but evidence to date suggests a dual role, as receptors binding ligands on stimulator cells and by direct or indirect involvement in intracellular signalling events. In mouse, truncated 'tailless' CD8 molecules occur naturally (CD8 alpha' polypeptides) and although they are expressed on the surface of thymocytes, they are not expressed on the surface of mature T cells. In this study, we show that truncated CD8 molecules are impaired in their ability to interact with the protein tyrosine kinase, p56lck, and have decreased ability to restore immune responsiveness in vitro. Our data support a dual function for CD8 molecules correlated with expression of external domains and cytoplasmic domains, respectively. Both functions appear to be critical for a competent immune system in vivo.

The specific immune response against syngeneic tumors by T cells is dependent on the existence of tumor-associated transplantation antigens (TATA). In the case of the chemically induced DBA/2-derived lymphoma Eb and its highly metastatic variant ESb the immunogenicity of these antigens is not sufficient to prevent tumor growth. Therefore we tested in two systems the influence of additional antigens as possible helper determinants for the generation of tumor-specific immune responses. In the Eb tumor system additional antigens were induced by mutagenization. The frequency of cytotoxic T lymphocytes (CTL) in response to mutagenized Eb cells was higher than that in response to untreated Eb cells. Fine specificity analysis revealed there there was no increase in the CTL response against the original TATA, but an activation of additional CTL clones responding to mutagen-induced antigens. In the ESb tumor system we tested the effect of additional recognition of minor histocompatibility antigens on the frequency of TATA-specific CTL. Transplantation of ESb tumor cells into B10.D2 mice, which are H-2-identical but differ in minor antigens, results in strong tumor rejection responses. In a limiting dilution mixed-leukocyte-tumor microculture system it was found that the minor antigens are recognized at the clonal level as independent antigens. The overall frequency of anti-tumor CTL in ESb-immunized B10.D2 mice was about 1 3000 . Among these, the frequency of TATA-specific CTL was 1 16,709 and thus not significantly different from that of syngeneic DBA/2 mice. Thus neither minor antigens nor mutagen-induced antigens acted in the Eb/ESb tumor system as helper determinants and did not increase the frequency of tumor-specific CTLs.

A role of CD4+ T helper cells in induction of tumor transplant rejection leading to complete regression of a highly metastatic DBA/2 mouse lymphoma was analyzed. Using an anti-CD4 monoclonal antibody (GK1.5) which eliminates T helper cells in vivo and in vitro, we found that CD4+ cells are required for tumor resistance in syngeneic DBA/2 mice or allogeneic but major histocompatibility complex-identical B10.D2 mice. In contrast, in allogeneic C57BL/6 mice tumor rejection was independent of CD4+ cells. An analogous requirement for immune CD4+ cells for in vitro induction of CD8+ tumor-specific cytotoxic T cells was found in these respective strains. The requirement for immune CD4+ cells in vitro could be replaced by recombinant interleukin 2. These results demonstrate a role of CD4+ regulatory T cells and T-T cell cooperation in the induction of anti-tumor immunity and tumor rejection, and point to possible therapeutic interventions in the afferent phase of anti-tumor immune responses.