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Biomedical subjects

Maurizio Zanetti

Publications and source records attributed to Maurizio Zanetti.

26 records · Page 2Linked to original sources
PubMed2004

B lymphocytes as antigen-presenting cell-based genetic vaccines.

Inoculation of plasmid DNA is a simple way to immunize, but it is characterized by low immunogenicity, which has hampered the development of effective DNA vaccines for human use. Here, we discuss how poor immunogenicity can be solved and present our proposal: genetically programmed B lymphocytes as antigen-presenting cell (APC) vaccines. First, we demonstrate that mature B lymphocytes take up plasmid DNA spontaneously, i.e., in the absence of any facilitating molecule or event, spontaneous lymphocyte transgenesis. Second, we demonstrate that transgenic B lymphocytes are easily and reproducibly turned into functional APCs with dual characteristics: upregulation of costimulatory molecules and endogenous synthesis of antigen. Used as immunogens in mice, transgenic B lymphocytes induce robust and long-lasting T-cell immunity after single intravenous injection. Surprisingly, immunity and protection against lethal virus challenge can be obtained with a single intravenous injection of 3 x 10(2) transgenic lymphocytes. The new approach is discussed relative to the advantage of targeting secondary lymphoid organs with genetically programmed B lymphocytes and the advantage offered with respect to low antigen dose. We suggest that these properties reflect on simple characteristics, such as time synchronization and initial localization to secondary lymphoid organs of APCs endowed with protracted synthesis and presentation of antigen to T cells.

Animals↗
PubMed2003

HIV-specific immunity during structured antiviral drug treatment interruption.

The immunologic correlates associated with control of viremia in HIV disease are poorly understood. We hypothesized that structured antiviral drug treatment interruptions could be utilized to better understand the relationship between HIV-specific immunity and viral replication. We thus examined the effects of two 8 weeks antiviral structured treatment interruptions (STIs) in a cohort of HIV-1 chronically infected individuals on highly active antiretroviral treatment (HAART) with (n = 13) and without (n = 12) therapeutic HIV immunizations. In this study, we observed that p24 gag antigen (np24) stimulated MIP-1beta levels and T helper immune responses prior to antiviral drug discontinuation were associated with control of viremia. Stronger and earlier production of gag peptide stimulated gamma interferon was observed in the immunized group during the structured antiviral drug interruptions. These results support the concept that HIV-specific immune responses are associated with control of viremia. Further study of immune-based therapies that enhance HIV-specific immunity is warranted.

AIDS Vaccines↗
PubMed2003

Role of T cell help and endoplasmic reticulum targeting in protective CTL response against influenza virus.

We report on the induction of primary and long-term memory cytotoxic T lymphocyte (CTL) responses against the nucleoprotein of the influenza virus A/PR8/34 in mice immunized with plasmid DNA targeted to B lymphocytes in the spleen. We found that the magnitude of the CTL response and the size of the pool of memory CTL was greater when the CTL response was induced in presence of T cell help. Interestingly, immunization with a signal sequence-competent transgene was markedly superior to immunization with a transgene lacking the endoplasmic reticulum (ER) targeting sequence, in inducing CTL. We also found a correlation between in vivo protection from lethal virus challenge and (1) the availability of T cell help and (2) ER targeting. Immunization of dendritic cell-deficient mice suggests that B lymphocytes function as antigen-presenting cells in this model of immunization. Collectively, the results suggest that somatic transgene immunization is a conceptually new approach to induce effective anti-viral CTL responses and to assess the parameters critical for long-lasting and protective CTL responses in vivo.

Animals↗
PubMed2003

Apoptotic DNA binds to HLA class II molecules inhibiting antigen presentation and participating in the development of anti-inflammatory functional behavior of phagocytic macrophages.

Resident macrophages are mainly responsible for the clearance of apoptotic cells from tissue by phagocytosis. Phagocytosis of apoptotic cells is not accompanied by activation of inflammatory mechanisms, unlike what happens when necrotic phenomena occur. We analyzed the effect of phagocytosis of apoptotic bodies on macrophage cell functions. After phagocytosis of apoptotic cells macrophages were unable to present an exogenous antigen to autologous antigen-specific T-cell lines. The inhibition was mediated by different mechanisms including binding of apoptotic DNA to human leukocyte antigen (HLA) class II molecules of macrophages, decreased expression of co-stimulatory molecules and increased secretion of tumor growth factor beta (TGFbeta). When dendritic cells were cultured with macrophages phagocytosing apoptotic cells, or with their supernatant, impaired dendritic cell antigen presenting activity and reduced tumor necrosis factor alpha (TNFalpha) secretion were found. Our results suggest that: (1) the phagocytosis of apoptotic bodies inhibits macrophage antigen presentation; (2) such inhibition is mediated by the binding of apoptotic DNA to macrophage HLA class II molecules as well as by the activation of biological mechanisms that induce an anti-inflammatory functional behavior in macrophages; and (3) macrophages phagocytosing apoptotic cells inhibit antigen presentation of neighboring dendritic cells via TGFbeta secretion. These events are likely related to the preservation of healthy tissues from the onset of inflammation.

Antigen Presentation↗
PubMed2003

CD4 T cell priming in dendritic cell-deficient mice.

Bone marrow (BM) chimeras (BMC) generated from mice carrying a null (-/-) mutation in the relB gene of the NF-kappaB family represent an ideal model for in vivo studies on the role of dendritic cells (DC) in the adaptive immune response. The spleen and lymph nodes (LN) of relB(-/-) BMC contain a small number of residual DC, mainly CD8alpha(+), that fail to up-regulate MHC class II and co-stimulatory molecules after stimulation in vitro. Moreover, residual spleen DC of relB(-/-) BMC have a 4-fold decrease in the ability to uptake and process soluble model antigen, ovalbumin (OVA), and failed to prime CD4 and CD8 T cells in vitro and in vivo. In addition, they also failed to present OVA peptide to OT-II transgenic T lymphocytes at a normal 1:10 (stimulator:responder) cell ratio. In spite of these multiple DC defects, relB(-/-) BMC immunized with plasmid DNA targeted to the spleen as the site of immune induction develop a specific CD4(+) T cell response comparable to that of relB competent mice. These data demonstrate that CD4( +) T cells can be primed in the absence of functional DC and suggest that relB may gauge the T cell response in vivo.

Animals↗
PubMed2003

The role of relB in regulating the adaptive immune response.

Dendritic cells (DCs), which represent a key type of antigen-presenting cell (APC), are important for the development of innate and adaptive immunity. DCs are involved in T cell activation in at least two main ways: priming via direct processing/presentation of soluble antigen taken up from the microenvironment (conventional priming), and processing/presentation of antigen released from other cells (cross-priming). relB, a component of the NF-kappaB complex of transcription factors, is a critical regulator of the differentiation of DCs. In mice, lack of relB impairs DCs derived from bone marrow both in number and function. Here relB (-/-) bone marrow chimera mice is used to study the APC function of residual DCs in presentation of soluble antigen and cross-priming. It is found that the DCs in these mice are profoundly deficient in their ability to both prime and cross-prime T cell responses. It was concluded that the relB gene is involved in regulating the APC function of DCs in vivo.

Adaptation, Physiological↗
PubMed2002

Identification of a human telomerase reverse transcriptase peptide of low affinity for HLA A2.1 that induces cytotoxic T lymphocytes and mediates lysis of tumor cells.

Telomerase reverse transcriptase (TRT) is a tumor-associated antigen expressed in the vast majority of human tumors and is presently one of the most promising target candidates for a therapeutic cancer vaccine. TRT is also expressed at low level in selected tissues and should be considered a self antigen. In the present study we sought to develop cytotoxic T lymphocytes (CTL) responses directed against human (h)TRT peptides with low relative affinity for which the available repertoire is to be preferentially spared from tolerance. This was accomplished by using analogue peptides of hTRT whose relative affinity for the MHC was increased by a targeted (-->Tyr) substitution in position one. By immunizing HLA A2.1 transgenic mice with these analogue peptides, we identified one such low relative affinity peptide (p572) that is endogenously processed and presented by HLA A2.1 in tumor cells, and is recognized by specific CTL. We used the highly immunogenic analogue peptide to successfully induce TRT-specific CTL in cancer patients and normal donors. CTL against p572-lysed human and mouse tumor cells but not activated autologous B cells. This peptide represents, therefore, an important candidate component of a cancer vaccine based on a TRT substrate and validates the strategy of targeting peptides with low affinity for the MHC for cancer immunotherapy.

Amino Acid Motifs↗