No abstract

CD25+ regulatory T (T reg) cells suppress the activation/proliferation of other CD4+ or CD8+ T cells in vitro. Also, down-regulation of CD25+ T reg cells enhance antitumor immune responses. In this study, we show that depletion of CD25+ T reg cells allows the host to induce both CD4+ and CD8+ antitumoral responses following tumor challenge. Simultaneous depletion of CD25+ and CD8+ cells, as well as adoptive transfer experiments, revealed that tumor-specific CD4+ T cells, which emerged in the absence of CD25+ T reg cells, were able to reject CT26 colon cancer cells, a MHC class II-negative tumor. The antitumoral effect mediated by CD4+ T cells was dependent on IFN-γ production, which exerted a potent antiangiogenic activity. The capacity of the host to mount this antitumor response is lost once the number of CD25+ T reg cells is restored over time. However, CD25+ T reg cell depletion before immunization with AH1 (a cytotoxic T cell determinant from CT26 tumor cells) permits the induction of a long-lasting antitumoral immune response, not observed if immunization is conducted in the presence of regulatory cells. A study of the effect of different levels of depletion of CD25+ T reg cells before immunization with the peptide AH1 alone, or in combination with a Th determinant, unraveled that Th cells play an important role in overcoming the suppressive effect of CD25+ T reg on the induction of long-lasting cellular immune responses.

No abstract

This manufacturing process is reliable and robust, the manufacturing time from biopsy to vaccine is <12 weeks and the expression and purification of antigens require only 2 weeks. The process is also broadly applicable for manufacturing monoclonal antibodies in plants, providing 50- to 1000-fold higher yields than alternative plant expression methods.

Idiotypic vaccination induced a specific immune response in the majority of patients with follicular lymphoma. Specific immune response was associated with a dramatic and highly statistically significant increase in disease-free survival. This is the first formal demonstration of clinical benefit associated with the use of a human cancer vaccine.

Patients infected with hepatitis C virus (HCV) have an impaired response against HCV antigens while keeping immune competence for other antigens. We hypothesized that expression of HCV proteins in infected dendritic cells (DC) might impair their antigen-presenting function, leading to a defective anti-HCV T-cell immunity. To test this hypothesis, DC from normal donors were transduced with an adenovirus coding for HCV core and E1 proteins and these cells (DC-CE1) were used to stimulate T lymphocytes. DC-CE1 were poor stimulators of allogeneic reactions and of autologous primary and secondary proliferative responses. Autologous T cells stimulated with DC-CE1 exhibited a pattern of incomplete activation characterized by enhanced CD25 expression but reduced interleukin 2 production. The same pattern of incomplete lymphocyte activation was observed in CD4 ؉ T cells responding to HCV core in patients with chronic HCV infection. However, CD4؉ response to HCV core was normal in patients who cleared HCV after alpha interferon therapy. Moreover, a normal CD4 ؉ response to tetanus toxoid was found in both chronic HCV carriers and patients who had eliminated the infection. Our results suggest that expression of HCV structural antigens in infected DC disturbs their antigen-presenting function, leading to incomplete activation of anti-HCV-specific T cells and chronicity of infection. However, presentation of unrelated antigens by noninfected DC would allow normal T-cell immunity to other pathogens.Hepatitis C virus (HCV) is a single-stranded RNA virus belonging to the Flaviviridae family (25). Although some patients exhibit acute self-limited infection, a characteristic feature of HCV is the high incidence of persistent infection and chronic hepatitis, with a strong risk for the development of hepatocellular carcinoma (10). This high incidence of chronicity suggests that the virus has developed efficient mechanisms to escape host immune responses. Indeed, although most patients have anti-HCV antibodies (38), cellular immune responses are weak in chronically infected patients. It has been reported that CD4 ϩ T-cell responses against viral antigens are vigorous in individuals who have cleared HCV after acute infection or after treatment with alpha interferon (IFN-␣) (11,21,26,35). By contrast, patients who fail to respond to therapy exhibit poor T-cell reactivity against viral proteins. Regarding CD8 ϩ lymphocytes, low responses have been detected in infected patients (7,32,37), and recent reports show that these cells play a critical role during the acute phase of the disease (8). Thus, chronicity of HCV infection is related to the inability of HCV-specific CD4 ϩ and CD8 ϩ T cells to accomplish efficient effector functions. These defects, however, are not the result of general immunosuppression since T-cell immunity to other pathogens is well preserved in patients with chronic HCV infection.HCV may evade immune surveillance by different mechanisms including mutations in regions that are targets for the immune system (13,40,41)...

T regulatory cells type 1 (Tr1 cells) are excellent candidates for cell therapy in multiple sclerosis (MS). The aim of our study was to assess the functional state of Tr1 cells and IL-10R signaling in patients with MS. Tr1 cells were induced in vitro by activation with anti-CD46 antibodies in controls and patients with MS. Cells were phenotyped by cytometry and suppression assays, and the expression of cytokines and transcription factors was evaluated by real-time PCR, ELISA, cytometry and Western blotting. We found that the activity of Tr1 cells and IL-10R signaling is impaired in MS patients since Tr1 cells isolated from MS patients produced less IL-10 than those obtained from controls. Indeed, the supernatants from Tr1 cells from controls did not suppress the proliferation of stimulated CD4 + cells from patients with MS. Furthermore, the IL-10R signaling pathway was not fully active in CD4 + cells from MS patients and these cells had higher baseline levels of SOCS3 transcripts than controls. Indeed, after in vitro IL-10 stimulation, the expression levels of the STAT1, STAT3 and IL-10RA genes were higher in MS patients than in controls. Moreover, Stat-3 phosphorylation was lower in controls than in patients after IL-10 stimulation. These results indicate that IL-10 regulatory function is impaired in patients with MS.

CD28 is one of the main costimulatory receptors responsible for the proper activation of T lymphocytes. We have isolated two aptamers that bind to the CD28 receptor. As a monomer, one of them interfered with the binding of CD28 to its ligand (B7), precluding the costimulatory signal, whereas the other one was inactive. However, dimerization of any of the anti-CD28 aptamers was sufficient to provide an artificial costimulatory signal. No antibody has featured a dual function (i.e., the ability to work as agonist and antagonist) to date. Two different agonistic structures were engineered for each anti-CD28 aptamer. One showed remarkably improved costimulatory properties, surpassing the agonistic effect of an anti-CD28 antibody. Moreover, we showed in vivo that the CD28 agonistic aptamer is capable of enhancing the cellular immune response against a lymphoma idiotype and of prolonging survival of mice which receive the aptamer together with an idiotype vaccine. The CD28 aptamers described in this work could be used to modulate the immune response either blocking the interaction with B7 or enhancing vaccine-induced immune responses in cancer immunotherapy.