Exonic knockout and knockin gene editing in hematopoietic stem and progenitor cells rescues RAG1 immunodeficiency

Recombination activating genes (RAGs) are tightly regulated during lymphoid differentiation, and their mutations cause a spectrum of severe immunological disorders. Hematopoietic stem and progenitor cell (HSPC) transplantation is the treatment of choice but is limited by donor availability and toxicity. To overcome these issues, we developed gene editing strategies targeting a corrective sequence into the human RAG1 gene by homology-directed repair (HDR) and validated them by tailored two-dimensional, three-dimensional, and in vivo xenotransplant platforms to assess rescue of expression and function. Whereas integration into intron 1 of RAG1 achieved suboptimal correction, in-frame insertion into exon 2 drove physiologic human RAG1 expression and activity, allowing disruption of the dominant-negative effects of unrepaired hypomorphic alleles. Enhanced HDR-mediated gene editing enabled the correction of human RAG1 in HSPCs from patients with hypomorphic RAG1 mutations to overcome T and B cell differentiation blocks. Gene correction efficiency exceeded the minimal proportion of functional HSPCs required to rescue immunodeficiency in Rag1-/- mice, supporting the clinical translation of HSPC gene editing for the treatment of RAG1 deficiency.

Unbiased assessment of genome integrity and purging of adverse outcomes at the target locus upon editing of CD4+ T-cells for the treatment of Hyper IgM1

Hyper IgM1 is an X-linked combined immunodeficiency caused by CD40LG mutations, potentially treatable with CD4+ T-cell gene editing with Cas9 and a "one-size-fits-most" corrective template. Contrary to established gene therapies, there is limited data on the genomic alterations following long-range gene editing, and no consensus on the relevant assays. We developed drop-off digital PCR assays for unbiased detection of large on-target deletions and found them at high frequency upon editing. Large deletions were also common upon editing different loci and cell types and using alternative Cas9 and template delivery methods. In CD40LG edited T cells, on-target deletions were counter-selected in culture and further purged by enrichment for edited cells using a selector coupled to gene correction. We then validated the sensitivity of optical genome mapping for unbiased detection of genome wide rearrangements and uncovered on-target trapping of one or more vector copies, which do not compromise functionality, upon editing using an integrase defective lentiviral donor template. No other recurring events were detected. Edited patient cells showed faithful reconstitution of CD40LG regulated expression and function with a satisfactory safety profile. Large deletions and donor template integrations should be anticipated and accounted for when designing and testing similar gene editing strategies.

Scalable GMP-compliant gene correction of CD4+ T cells with IDLV template functionally validated in vitro and in vivo

Hyper-IgM1 is a rare X-linked combined immunodeficiency caused by mutations in the CD40 ligand (CD40LG) gene with a median survival of 25 years, potentially treatable with in situ CD4+ T cell gene editing with Cas9 and a one-size-fits-most corrective donor template. Here, starting from our research-grade editing protocol, we pursued the development of a good manufacturing practice (GMP)-compliant, scalable process that allows for correction, selection and expansion of edited cells, using an integrase defective lentiviral vector as donor template. After systematic optimization of reagents and conditions we proved maintenance of stem and central memory phenotypes and expression and function of CD40LG in edited healthy donor and patient cells recapitulating the physiological CD40LG regulation. We then documented the preserved fitness of edited cells by xenotransplantation into immunodeficient mice. Finally, we transitioned to large-scale manufacturing, and developed a panel of quality control assays. Overall, our GMP-compliant process takes long-range gene editing one step closer to clinical application with a reassuring safety profile.

Access site bleeding complications comparing oral anticoagulation therapy with NOACs and VKAs in patients with atrial fibrillation undergoing cardiac implantable device intervention

Funding Acknowledgements

Type of funding sources: None.

Background

Atrial fibrillation is frequent in patients undergoing cardiac implantable electronic device (CIED) intervention. Such population require oral anticoagulation therapy, which increases risk of procedure related bleeding. There is a lack on data on procedure-related bleeding outcome with non-vitamin K antagonist anticoagulants (NOACs) vs vitamin K antagonist anticoagulants (VKAs) in patients with AF undergoing CIED intervention.

Study purpose

Aim of the present stud was to evaluate whether NOACs have a safety benefit compared to VKAs in terms of fewer hemorrhagic complications at the site of CIED implant.

Methods

Consecutive AF patients receiving NOACs or VKAs at the time of CIED procedure were included in this observational, retrospective, monocentric investigation. Primary endpoint was the incidence of post-intervention clinically significant pocket hematoma. Multivariate analysis was performed to investigate the association between covariates and the primary endpoint.

Results

A total of 311 patients were enrolled, 146 on NOACs and 165 on VKAs. The incidence of pocket hematoma was 3.4% in the NOAC vs 13.3% in the VKA group (p=0.002) (Figure 1). Primary outcome-free survival at 30-days was 96.6 % in patients on NOACs and 86.0% in those on VKAs (p=0.019) (Figure 2). Multivariate analysis, adjusted by propensity-score calculation of inverse-probability-weighting, showed a significantly lower occurrence of pocket hematoma in patients receiving NOACs vs VKAs (HR 0.35, 95% CI 0.13-0.96, p=0.042). Such NOACs benefit was confirmed vs patients on VKAs without peri-procedural bridging with low-molecular weight heparin (HR 0.34, 95% CI 0.11-0.99, p=0.048). The incidence of pocket infection, surgical pocket evacuation, ischemic events and major bleeding complications at 30 days (secondary endpoints) was similar in the two groups.

Conclusion

Among patients with AF undergoing implantable cardiac defibrillator or pace-maker intervention, the use of NOACs vs VKAs is associated with significant reduction of post-procedural pocket hematoma, regardless of bridging with low molecular-weight heparin in the VKA group.

Comparison of infective complications with two different antibiotic prophylaxis at two-years follow up in patients undergoing cardiac implantable electronic device procedure: a prospective study

Funding Acknowledgements

Type of funding sources: None.

Background

Cardiac implantable electronic device (CIED) infective complications are associated with high morbidity and mortality. Selection of proper antibiotic prophylaxis therapy is mandatory, as it can decrease the infective risk.

Purpose of the Study

Aim of the present study was to compare two different antibiotic strategy in term of procedural-related infective complications in a two-years follow-up.

Material and Methods

Patients undergoing CIED procedure (implant, replacement, or revision), with cefuroxime antibiotic prophylaxis during 2009 were consecutively enrolled as study group, with the purpose to have a long follow-up available (10 years). Patients undergoing CIED procedure (implant, replacement, or revision), with cefazolin antibiotic prophylaxis during 2020 were consecutively enrolled as control group. Primary endpoint was the evaluation of infective complications in the first 2 years follow-up (pocket infection, endocarditis and infective complication requiring CIED complete extraction). Multivariate analysis was performed to evaluate association between covariates resulted significantly different between the two study groups and study endpoint. Long-term follow-up incidence of infective complications was evaluated in the cefuroxime group.

Results

340 patients were enrolled in the cefuroxime prophylaxis group and 239 patients in the cefazolin prophylaxis group. There was no significative difference of median age between the two study groups. Patients in the cefazolin prophylaxis group compared to the cefuroxime group showed higher rate of diabetes (33.1% vs 22.1%, p=0.003), dyslipidemia (46.4% vs 36.5%, p=0.02) and higher rate of antiplatelet (45.2% vs 40.6%, p<0.001) and anticoagulation therapy (36.8% vs 31.8%, p<0.001) (Figure 1). ICD and CRT implant was more frequent in patients in the cefazolin group (33.3% vs 25.06%, p=0.05) (Figure 2). There was no significant difference of the primary endpoint in the two study groups: pocket infection (cefazolin group n=4, 1.7%, vs cefuroxime group n=5, 1.5%, p=0.85), endocarditis (cefazolin group n=1, 0.4%, vs cefuroxime group n=1, 0.3%, p=0.8) and infection requiring complete device extraction (cefazolin group n=2, 0.8%, vs cefuroxime group n=2, 0.6%, p=0.95). At multivariate analysis, there was an observed trend in reduction of infective complications in patients undergoing pacemaker (odds ratio 0.23) and CRT (odds ratio 0.82) implant.

At 10 years follow-up, 11 (3.2%) infective procedure-related complications were recorded in the cefuroxime group, 5 pocket infection, 5 pocket infection with erosion and 1 endocarditis.

Conclusion

Cefazolin antibiotic prophylaxis is effective as cefuroxime prophilaxis in reducing CIED procedure-related infections, even if patients in the cefazolin group showed higher prevalence of comorbidities and more complex device procedure (ICD and CRT implant).

Characterization and Functional Analysis of CD44v6.CAR T Cells Endowed with a New Low-Affinity Nerve Growth Factor Receptor-Based Spacer

Effectiveness of adoptively transferred chimeric antigen receptor (CAR) T cells strongly depends on the quality of CAR-mediated interaction of the effector cells with the target antigen on tumor cells. A major role in this interaction is played by the affinity of the single-chain variable fragment (scFv) for the antigen, and by the CAR design. In particular, the spacer domain may impact on the CAR T cell function by affecting the length and flexibility of the resulting CAR. This study addresses the need to improve the manufacturing process and the antitumor activity of CD44v6-specific CAR T cells by defining the optimal structure of a spacer region derived from the extracellular domain of the human low-affinity nerve growth factor receptor (LNGFR). We tailored the LNGFR spacer to modulate CAR length to efficiently recognize distal or proximal epitopes and to allow selection of transduced CAR T cells by the use of clinical-grade validated manufacturing systems. The different LNGFR spacers investigated in this study are responsible for the generation of CAR T cells with a different memory phenotype, which is mainly related to the level of CAR expression and the extent of the associated tonic signaling. In particular, the CD44v6-NWN2.CAR T cells are enriched in central memory cells and show improved in vitro functions in terms of killing capability, and in vivo antitumor activity against hematological and solid tumors. Clinical Trial Registration numbers: clinicaltrial.gov NCT04097301; ClinicalTrials.gov, NCT00423124.

CAR T Cells Redirected to CD44v6 Control Tumor Growth in Lung and Ovary Adenocarcinoma Bearing Mice

The main challenge of adoptive therapy with Chimeric Antigen Receptor modified T cells (CAR T) is the application to the field of solid tumors, where the identification of a proper antigen has emerged as one of the major drawbacks to CAR T cell treatment success. CD44 is a glycoprotein involved in cell-cell and cell-matrix interactions. The isoform containing the variant domain 6 of CD44 gene (CD44v6) has been implicated in tumorigenesis, tumor cell invasion and metastasis and represents an attractive target for CAR T cell therapies. Targeting CD44v6 antigen has been shown to control tumor growth in acute myeloid leukemia and multiple myeloma mouse models. While CAR T approach for the treatment of B cell malignancies has shown great success, response rates among patients with solid cancer are less favorable. The purpose of our study was to test the efficacy of CD44v6.CAR T cells, produced in compliance with Good Manufacturing Practice (GMP), in adenocarcinoma tumor models. We generated a bicistronic retroviral vector containing the CD44v6 CAR and the HSV-TK Mut2 suicide gene to enhance the safety of the proposed CAR T cell therapy. CD44v6 transduced CAR T cells were homogeneously positive for ΔLNGFR selection marker, were enriched in T central memory (T_CM) and T memory stem cells (T_SCM) and displayed a highly activated phenotype. In vitro assays revealed antigen-specific activation and cytotoxicity of human CD44v6.CAR T cells against CD44v6 expressing tumor cell lines. When infused in immunodeficient tumor bearing mice, human CD44v6.CAR T cells were able to reach, infiltrate and proliferate at tumor sites, finally resulting in tumor growth control. Next, we checked if cells produced in compliance with GMP grade standards retained the same antitumor activity of those produced with research grade materials and protocols. Noteworthy, no differences in the potency of the CAR T obtained with the two manufacturing processes were observed. In conclusion, our preclinical results suggest that CD44v6.CAR T based adoptive therapy could be a promising strategy in solid cancer treatment.

Extracellular NGFR Spacers Allow Efficient Tracking and Enrichment of Fully Functional CAR-T Cells Co-Expressing a Suicide Gene

Chimeric antigen receptor (CAR)-T cell immunotherapy is at the forefront of innovative cancer therapeutics. However, lack of standardization of cellular products within the same clinical trial and lack of harmonization between different trials have hindered the clear identification of efficacy and safety determinants that should be unveiled in order to advance the field. With the aim of facilitating the isolation and in vivo tracking of CAR-T cells, we here propose the inclusion within the CAR molecule of a novel extracellular spacer based on the low-affinity nerve-growth-factor receptor (NGFR). We screened four different spacer designs using as target antigen the CD44 isoform variant 6 (CD44v6). We successfully generated NGFR-spaced CD44v6 CAR-T cells that could be efficiently enriched with clinical-grade immuno-magnetic beads without negative consequences on subsequent expansion, immuno-phenotype, in vitro antitumor reactivity, and conditional ablation when co-expressing a suicide gene. Most importantly, these cells could be tracked with anti-NGFR monoclonal antibodies in NSG mice, where they expanded, persisted, and exerted potent antitumor effects against both high leukemia and myeloma burdens. Similar results were obtained with NGFR-enriched CAR-T cells specific for CD19 or CEA, suggesting the universality of this strategy. In conclusion, we have demonstrated that the incorporation of the NGFR marker gene within the CAR sequence allows for a single molecule to simultaneously work as a therapeutic and selection/tracking gene. Looking ahead, NGFR spacer enrichment might allow good manufacturing procedures-manufacturing of standardized CAR-T cell products with high therapeutic potential, which could be harmonized in different clinical trials and used in combination with a suicide gene for future application in the allogeneic setting.

The tumor vessel targeting agent NGR-TNF controls the different stages of the tumorigenic process in transgenic mice by distinct mechanisms

NGR-TNF is a vascular targeting agent in advanced clinical development, coupling tumor necrosis factor-α (TNF) with the CNGRCG peptide, which targets a CD13 isoform specifically expressed by angiogenic vessels. Antitumor efficacy of NGR-TNF has been described in different transplantation tumor models. Nevertheless, the mechanism underlying its activity is not fully understood. In the wild type and in the immunodeficient (RAG^-/-) RIP1-Tag2 models of multistage pancreatic carcinogenesis, we demonstrate that CD13 is highly expressed on endothelial cells of hyperplastic and angiogenic islets, whereas its expression is down regulated in tumors where it partially colocalize with pericytes. In vivo CNGRCG peptides coupled to fluorescent nanoparticles (quantum dots) bind to CD13 and colocalize with anti-CD31, in pancreatic islets. At early stage, low doses of NGR-murine (m)TNF have a direct cytotoxic effect inducing endothelial cell apoptosis, reducing vessel density and eventually inhibiting the development of angiogenic islets. At a later stage, NGR-mTNF is able to reduce tumor growth inducing vascular normalization, exclusively when treatment is carried out in the immunocompetent mice. Interestingly, NGR-mTNF-treated tumors from these mice are characterized by CD8⁺ T cell infiltration. At molecular level, overexpression of genes involved in vessels normalization was detected only in NGR-mTNF-treated tumors from immunocompetent mice. These findings identified a new mechanism of action of NGR-mTNF, providing support for the development of new therapeutic strategies combining chemotherapy or active/adoptive immunotherapies to low dose NGR-TNF treatment.

Therapeutic genes for anti-HIV/AIDS gene therapy

The multiple therapeutic approaches developed so far to cope HIV-1 infection, such as anti-retroviral drugs, germicides and several attempts of therapeutic vaccination have provided significant amelioration in terms of life-quality and survival rate of AIDS patients. Nevertheless, no approach has demonstrated efficacy in eradicating this lethal, if untreated, infection. The curative power of gene therapy has been proven for the treatment of monogenic immunodeficiensies, where permanent gene modification of host cells is sufficient to correct the defect for life-time. No doubt, a similar concept is not applicable for gene therapy of infectious immunodeficiensies as AIDS, where there is not a single gene to be corrected; rather engineered cells must gain immunotherapeutic or antiviral features to grant either short- or long-term efficacy mostly by acquisition of antiviral genes or payloads. Anti-HIV/AIDS gene therapy is one of the most promising strategy, although challenging, to eradicate HIV-1 infection. In fact, genetic modification of hematopoietic stem cells with one or multiple therapeutic genes is expected to originate blood cell progenies resistant to viral infection and thereby able to prevail on infected unprotected cells. Ultimately, protected cells will re-establish a functional immune system able to control HIV-1 replication. More than hundred gene therapy clinical trials against AIDS employing different viral vectors and transgenes have been approved or are currently ongoing worldwide. This review will overview anti-HIV-1 infection gene therapy field evaluating strength and weakness of the transgenes and payloads used in the past and of those potentially exploitable in the future.

Abstract 5081: Development and characterization of a new antiangiogenic peptide targeting tumor vessels

Vascular targeting is a promising approach for the treatment of angiogenesis-dependent diseases particularly for tumor treatment. Targeted drug-delivery to tumor vasculature preferentially localizes the drug at the tumor site, thus increasing efficacy and decreasing systemic side effects. In tumor neovasculature activated endothelial cells have been shown to express molecules characteristic of angiogenic vessels and virtually not expressed in normal vessels. Notably, tumor-associated endothelial cells express an isoform of aminopeptidase N (CD13) that binds to the cyclic peptide Cys-Asn-Gly-Arg-Cys (named NGR). Such “vascular addresses” allow the selective targeting of systemically administrated therapies to tumors, including chemotherapeutic agents and cytokines. In particular, the NGR-TNF conjugate has been shown to induce potent antitumor effects and is currently tested in phase II-III clinical trials. In this context, we developed and characterized a new tumor targeting peptide with a pathway of specificity comparable to that of NGR, but with a higher stability and affinity for the tumor vessels. In particular, we synthesized peptides containing the Cys-Arg-Gly-Asn-Cys cyclic motif made of D-aminoacids (i.e. crGnc, named rGn). The rGn peptide can be considered a partial retro-inverso of the NGR peptide, since a real retro-inverso petpide requires cyclization through the backbone, whereas in this case cyclization was obtained via the formation of the disulphide bond between the N and the C- terminal cysteins. The main advantage of retro-inverso peptides is their high metabolic stability, because the peptide bonds generated by D-aminoacids are stable to enzymatic cleavage. To characterize the biological activity and functions of the new peptide, we studied the rGn/CD13 interactions in vitro and in vivo on both tumour blood vessels and normal tissues, using quantum dots (Qd), whole-mount histology, and fluorescence/confocal microscopy. rGn-Qd showed the same recognition pattern of NGR-Qd on primary cell cultures of endothelial origin. Consistently, in vivo administered rGn-Qd and NGR-Qd bind to tumor blood vessels of several murine tumours. Of note, the binding of either rGn-Qd or NGR-Qd to CD13 is efficiently competed by an excess of either NGR or rGn peptide, respectively, both in in vitro and in vivo models. In particular, the rGn peptide showed a significantly higher affinity than NGR for its target cells in vitro. Moreover, silencing CD13 with specific shRNA prevented not only anti-CD13 MoAb binding, but also rGn-Qd binding. Finally, stressed experimental conditions that allowed deamidation of NGR to isoDGR, do not affect rGn structural integrity. In conclusion, the rGn peptide binds to CD13 expressed by angiogenic vessels with higher affinity and stability than NGR. Coupling rGn to cytotoxic/cytostatic molecules could lead to the generation of new potent antitumor compounds.

Citation Format: Paola Di Matteo, Claudia Asperti, Simona Porcellini, Andrea Spitaleri, Claudio Bordignon, Giovanna Musco, Gian-Paolo Rizzardi, Catia Traversari. Development and characterization of a new antiangiogenic peptide targeting tumor vessels. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5081. doi:10.1158/1538-7445.AM2013-5081

Abstract 4381: The novel direct-acting vascular targeting agent NGR-TNF exerts in vivo antitumor activity by inducing endothelial and tumor cell death in the absence of proangiogenic bone-marrow derived cell recruitment

Treatment with either certain chemotherapy drugs at maximum tolerated dose (e.g. paclitaxel, cyclophosphamide, 5-FU), vascular-disrupting agents (VDAs; e.g. fosbretabulin, Oxi4503), or local irradiation can rapidly induce mobilization and subsequent tumor homing of proangiogenic bone marrow derived cells (BMDCs), such as circulating endothelial progenitor cells (CEPs), CD11b/Tie-2-expressing monocytes (TEMs), CD11b+Gr1+ neutrophils and myeloid-derived suppressor cells (MDSCs). Increase in several growth factors and chemokines, such as SDF-1, G-CSF as well as osteopontin, contribute to the mobilization of these BMDCs that can colonize the drug treated tumors preferentially at the viable tumor rim that characteristically remains after treatment with drugs such as VDAs. This process promotes angiogenesis and rapid tumor regrowth, thus diminishing the overall antitumor activities of the aforementioned treatments. NGR-TNF, presently in advanced clinical development, is a direct-acting vascular targeting agent coupling the CNGRCG peptide (NGR), homing to angiogenic blood vessels, and tumor necrosis factor alpha (TNF). Experiments performed in the Lewis lung carcinoma (LLC) model, suggested that when administrated at low doses, NGR-TNF causes a decrease of tumor blood vessels density and induces apoptosis of tumor cells without inducing cytokine-rebound and recruitment of pro-angiogenic BMDC. In order to extend these results, we investigated whether NGR-TNF fails to mobilize proangiogenic BMDC even after repeated treatments and in a highly aggressive and metastatic tumor model. LLC and 4T1 mammary gland carcinoma cells were subcutaneously implanted respectively into immunocompetent C57BL/6J or Balb/C mice. Blood was obtained by cardiac puncture or retro-orbital sinus bleeding, 4, 24 hours or 1 week after single or repeated treatments with either NGR-TNF at low and high dose or saline. Using flow cytometry CEPs were defined as CD45−/CD13+/flk-1+/CD117+/7AAD−, TEMs as CD45+/CD11b+/Tie2+ and MDSCs as CD45+/CD11b+/Gr1+ cells. At low doses, NGR-TNF exerts a control of 4T1 primary tumor growth, without inducing cytokine rebound and pro-angiogenic BMDCs mobilization. In addition, even after repeated administrations at low doses, NGR-TNF fails to mobilize or recruit to the tumor site different subtypes of BMDCs. Therefore, low doses of NGR-TNF exert an antitumor activity without inducing a reactive pro-angiogenic host response, and as such provide an explanation and the rationale for the successful use of lower dose NGR-TNF administration protocols in the clinic.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4381. doi:1538-7445.AM2012-4381

Abstract 4258: Both NGR and TNF portions contribute to the biological activity of NGR-TNF vascular targeting agent in vivo

NGR-TNF, presently in advanced clinical development, is a direct-acting vascular targeting agent coupling the CNGRCG peptide (NGR), homing to angiogenic blood vessels, and tumour necrosis factor alpha (TNF). To elucidate its mechanism of action, we investigated the NGR-TNF homing and downstream effects using doses comparable to those used in clinical trials. Targeting studies with NGR-quantum dots administered in vivo demonstrate that the binding to CD13 occurs only in neo-angiogenic tissues, sparing CD13-expressing normal tissues. NGR-TNF binding is highly specific targeting the tumour vessel of human colon cancer specimens, whereas the binding does not occur in the normal colon tissue of the very same patients. To investigate the interaction between NGR and CD13, we incubated human primary mesangioblasts with biotinylated peptides, cross-linked with BS3 to form covalent bounds between interacting molecules, lysed the cells and pulled down biotinylated proteins by streptavidin-coated magnetic beads. Only biotinylated NGR pulls down CD13 in monomeric and dimeric forms. After CD13 immunoprecipitation, the CD13 immunoprecipitated from NGR-treated cells is biotinylated, unlike CD13 immunoprecipitated from control peptide. Depriving CD13 completely in the total lysate of cells incubated with NGR, the biotinylated bands at 150 kDa disappears. Overall these data demonstrate that biotinylated NGR directly interacts with CD13 on the cell membrane. To address whether NGR binding affects the TNF-TNFR interaction, we used TNF conjugated to an Ig Fc portion so that it can be visualised onto target cells, and we tested the ability of both TNF and NGR-hTNF to compete with this binding. Interestingly, while in NGR-non-binder cells the affinity between TNF and NGR-TNF is the same, NGR-hTNF clearly displays an higher affinity than TNF in NGR-binder cells. It is worth noting that the 1-log increase in NGR-hTNF affinity is actually due to the binding of NGR to CD13 because this is overcome with increasing amounts of free NGR. We then investigated how NGR-hTNF affects signaling pathways in human endothelial cells. Interestingly, we found that, over hTNF, NGR-hTNF impairs cell survival a) by inhibiting the activation of the pro-survival Ras pathway inducing a down-modulation of Raf, MEK, Erk, and Akt, along with preventing VEGFR2 mRNA up-regulation, and b) by activating the pro-apoptotic caspases (3, 8 and 9). Interestingly, if we stimulate endothelial cells with TNF and a neutral NGR-carrying molecule (administering them in combination, not conjugated), we observe the same impairment of the Ras signaling pathway, thus demonstrating that the engagement of CD13 has a direct effect on the signaling downstream of Ras. In conclusion, the binding of NGR to CD13 determines not only the “mere homing” of NGR-TNF but confers to NGR-hTNF specific features that significantly differentiate it from TNF.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4258. doi:10.1158/1538-7445.AM2011-4258

Selective preservation of bone marrow mature recirculating but not marginal zone B cells in murine models of chronic inflammation

Inflammation promotes granulopoiesis over B lymphopoiesis in the bone marrow (BM). We studied B cell homeostasis in two murine models of T cell mediated chronic inflammation, namely calreticulin-deficient fetal liver chimeras (FLC), which develop severe blepharitis and alopecia due to T cell hyper responsiveness, and inflammatory bowel disease (IBD) caused by injection of CD4⁺ naïve T cells into lymphopenic mice. We show herein that despite the severe depletion of B cell progenitors during chronic, peripheral T cell-mediated inflammation, the population of BM mature recirculating B cells is unaffected. These B cells are poised to differentiate to plasma cells in response to blood borne pathogens, in an analogous fashion to non-recirculating marginal zone (MZ) B cells in the spleen. MZ B cells nevertheless differentiate more efficiently to plasma cells upon polyclonal stimulation by Toll-like receptor (TLR) ligands, and are depleted during chronic T cell mediated inflammation in vivo. The preservation of mature B cells in the BM is associated with increased concentration of macrophage migration inhibitory factor (MIF) in serum and BM plasma. MIF produced by perivascular dendritic cells (DC) in the BM provides a crucial survival signal for recirculating B cells, and mice treated with a MIF inhibitor during inflammation showed significantly reduced mature B cells in the BM. These data indicate that MIF secretion by perivascular DC may promote the survival of the recirculating B cell pool to ensure responsiveness to blood borne microbes despite loss of the MZ B cell pool that accompanies depressed lymphopoiesis during inflammation.

Mutational analysis of the HIV-1 auxiliary protein Vif identifies independent domains important for the physical and functional interaction with HIV-1 reverse transcriptase

The HIV-1 accessory protein Vif plays a dual role: it counteracts the natural restriction factors APOBEC3G and 3F and ensures efficient retrotranscription of the HIV-1 RNA genome. We have previously shown that Vif can act as an auxiliary factor for HIV-1 reverse transcriptase (RT), increasing its rate of association to RNA or DNA templates. Here, by using seven different Vif mutants, we provide in vitro evidences that Vif stimulates HIV-1 RT through direct protein–protein interaction, which is mediated by its C-terminal domain. Physical interaction appears to require the proline-rich region comprised between amino acid (aa) 161 and 164 of Vif, whereas the RT stimulatory activity requires, in addition, the extreme C-terminal region (aa 169–192) of the Vif protein. Neither the RNA interaction domain, nor the Zn⁺⁺-binding domain of Vif are required for its interaction with the viral RT. Pseudotyped HIV-1 lentiviral vectors bearing Vif mutants deleted in the RNA- or RT-binding domains show defects in retrotranscription/integration processes in both permissive and nonpermissive cells. Our results broaden our knowledge on how three important functions of Vif (RNA binding, RT binding and stimulation and Zn⁺⁺ binding), are coordinated by different domains.

Transcriptional enhancers induce insertional gene deregulation independently from the vector type and design

The integration characteristics of retroviral (RV) vectors increase the probability of interfering with the regulation of cellular genes, and account for a tangible risk of insertional mutagenesis in treated patients. To assess the potential genotoxic risk of conventional or self-inactivating (SIN) gamma-RV and lentiviral (LV) vectors independently from the biological consequences of the insertion event, we developed a quantitative assay based on real-time reverse transcriptase--PCR on low-density arrays to evaluate alterations of gene expression in individual primary T-cell clones. We show that the Moloney leukemia virus long terminal repeat (LTR) enhancer has the strongest activity in both a gamma-RV and a LV vector context, while an internal cellular promoter induces deregulation of gene expression less frequently, at a shorter range and to a lower extent in both vector types. Downregulation of gene expression was observed only in the context of LV vectors. This study indicates that insertional gene activation is determined by the characteristics of the transcriptional regulatory elements carried by the vector, and is largely independent from the vector type or design.

EVA regulates thymic stromal organisation and early thymocyte development

Epithelial V-like antigen (EVA) is an immunoglobulin-like adhesion molecule identified in a screen for molecules developmentally regulated at the DN to DP progression in thymocyte development. We show that EVA is expressed during the early stages of thymus organogenesis in both fetal thymic epithelia and T cell precursors, and is progressively downregulated from day 16.5 of embryonic development. In the postnatal thymus, EVA expression is restricted to epithelial cells and is distributed throughout both cortical and medullary thymic regions. Transgenic overexpression of EVA in the thymus cortex resulted in a modified stromal environment, which elicited an increase in organ size and absolute cell number. Although peripheral T lymphocyte numbers are augmented throughout life, no imbalance either in the repertoire, or in the different T cell subsets was detected. Collectively, these data suggest a role for EVA in structural organisation of the thymus and early lymphocyte development.

Regulation of peripheral T cell activation by calreticulin

Regulated expression of positive and negative regulatory factors controls the extent and duration of T cell adaptive immune response preserving the organism's integrity. Calreticulin (CRT) is a major Ca2+ buffering chaperone in the lumen of the endoplasmic reticulum. Here we investigated the impact of CRT deficiency on T cell function in immunodeficient mice reconstituted with fetal liver crt-/- hemopoietic progenitors. These chimeric mice displayed severe immunopathological traits, which correlated with a lower threshold of T cell receptor (TCR) activation and exaggerated peripheral T cell response to antigen with enhanced secretion of inflammatory cytokines. In crt-/- T cells TCR stimulation induced pulsatile cytosolic elevations of Ca2+ concentration and protracted accumulation of nuclear factor of activated T cells in the nucleus as well as sustained activation of the mitogen-activated protein kinase pathways. These observations support the hypothesis that CRT-dependent shaping of Ca2+ signaling critically contributes to the modulation of the T cell adaptive immune response.

NKG2D-independent suppression of T cell proliferation by H60 and MICA

The activating receptor NKG2D recognizes a wide range of different ligands, some of which are primarily expressed in "stressed" tissues or on tumor cells. Until now, similar stimulatory effects on natural killer and CD8+ T cells have been described for all NKG2D ligands, and the NKG2D receptor/ligand system has therefore been interpreted as a sensor system involved in tumor immune surveillance and activation of immune responses. We show here that the NKG2D ligands H60 and MIC class 1 chain-related protein A (MICA) can also mediate strong suppressive effects on T cell proliferation. Responsiveness to H60- and MICA-mediated suppression requires IL-10 and involves a receptor other than NKG2D. These findings might provide explanations for the observation that strong in vivo NKG2D ligand expression, such as that on tumor cells, sometimes fails to support effective immune responses and links this observation to a distinct subgroup of NKG2D ligands.

Improved thymopoietic potential in aviremic HIV infected individuals treated with HAART by intermittent IL-2 administration

OBJECTIVE

In HIV-positive individuals administration of intermittent interleukin (IL)-2 in addition to highly active antiretroviral therapy (HAART) induces expansion of the peripheral T cell pool with dilution of signal joint T cell receptor excision circles (sjTREC) that cannot be used to measure thymic output. We analysed whether in vitro thymopoiesis could be used to predict in vivo thymic output in IL-2 treated subjects.

DESIGN AND METHODS

We correlated the relative variation of peripheral CD4 T cells over 12 months in HIV-positive subjects on HAART or HAART + IL-2 with the mean levels of both sjTREC and T cells developed in chimeric murine foetal thymic organ cultures (FTOC) reconstituted with circulating progenitors.

RESULTS

In contrast with HAART treated individuals in which these values were directly correlated, in subjects receiving HAART + IL-2 the increase of CD4 T cells in vivo was correlated to neither sjTREC number nor to reconstitution of FTOC, probably reflecting a main effect of IL-2 in the expansion of the peripheral T cell pool. Nevertheless, addition of IL-2 to HAART determined a significant increase of in vitro thymopoietic potential in individuals with undetectable viraemia.

CONCLUSIONS

The increased T cell development in vitro after addition of IL-2 to HAART suggests that intermittent IL-2 administration may exert a positive influence on lymphopoiesis. In two subjects with positive viraemia treated with IL-2 we observed reduced in vitro development of T cell precursors suggesting that the positive influence of IL-2 on thymopoiesis could be secondary to the control of viral replication by HAART. These observations provide novel evidence in support of the potential beneficial use of IL-2 in HAART treated individuals.

Constitutive endocytosis and degradation of the pre-T cell receptor

The pre-T cell receptor (TCR) signals constitutively in the absence of putative ligands on thymic stroma and signal transduction correlates with translocation of the pre-TCR into glycolipid-enriched microdomains (rafts) in the plasma membrane. Here, we show that the pre-TCR is constitutively routed to lysosomes after reaching the cell surface. The cell-autonomous down-regulation of the pre-TCR requires activation of the src-like kinase p56(lck), actin polymerization, and dynamin. Constitutive signaling and degradation represents a feature of the pre-TCR because the gammadeltaTCR expressed in the same cell line does not exhibit these features. This is also evident by the observation that the protein adaptor/ubiquitin ligase c-Cbl is phosphorylated and selectively translocated into rafts in pre-TCR- but not gammadeltaTCR-expressing cells. A role of c-Cbl-mediated ubiquitination in pre-TCR degradation is supported by the reduction of degradation through pharmacological inhibition of the proteasome and through a dominant-negative c-Cbl ubiquitin ligase as well as by increased pre-TCR surface expression on immature thymocytes in c-Cbl-deficient mice. The pre-TCR internalization contributes significantly to the low surface level of the receptor on developing T cells, and may in fact be a requirement for optimal pre-TCR function.

Lack of NO Formation Is Involved in the Vasodilative Response to Contrast Media

Intravascular injection of angiographic contrast media results in peripheral vasodilation and hypotension. The mechanisms underlying these hemodynamic changes are not entirely clear. We hypothesized that increased formation of nitric oxide (NO) could be involved in the vasodilatory response to contrast media. To address this assumption we have investigated whether N(G)-monomethyl-L-arginine (L-NMMA, 200 mg/kg) and N(G)-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg), two specific NO formation inhibitors, can abolish the hypotensive response to intravascular injection of isopaque amin (1 g/kg), a contrast medium, as well as bradykinin (10 µg/kg), a NO-dependent vasodilator, in anaesthetized normotensive rats. In rats before pretreatment with L-NMMA and L-NAME, the absolute values of the average fall in mean arterial pressure (MAP) induced by intravascular injection of isopaque amin and bradykinin were 21.3 +/- 2.1 and 37.2 +/- 4.4 mmHg, respectively. Pretreatment with L-NMMA and L-NAME failed to affect the hypotensive response to isopaque amin; by administering isopaque amin in rats pretreated with L-NMMA and L-NAME the absolute values of the average fall in MAP were 25.6 +/- 4.9 and 23.4 +/- 3.9 mmHg, respectively, similar to the average fall in MAP before treatment with NO formation inhibitors. In contrast, the hypotensive response to bradykinin was significantly inhibited; by administering bradykinin in rats pretreated by L-NMMA and L-NAME, the absolute values of the average fall in MAP were 10.2 +/- 2.8 and 7.2 +/- 2.2 mmHg, respectively, much less than the average fall in MAP before treatment with NO formation inhibitors. We conclude that intravascular injection of isopaque amin causes reduction in systemic arterial pressure. However, this vasodilative effect seems unrelated majorly to augmented endothelium-derived NO formation.

[Bifurcation stenting of unprotected common trunk: a case report and review of the literature]

Left main disease is the most severe form of atherosclerotic heart disease, with severe prognostic implications in the short-medium term. The traditional therapeutic approach has been surgical, with placement of bypass grafts both on the LAD and the circumflex artery. Published experience with the percutaneous approach to left main disease has been disappointing because of acute procedural problems and poor long-term outcome. On the other hand, a review of the literature shows a strong negative selection of patients offered PTCA of left main-stem lesions: most published series are composed of extremely high-risk patients, often in cardiogenic shock or with severe extracardiac multisystem disease, with a prohibitive surgical risk and an inherently poor acute and mid-term prognosis. We describe such a patient, a 77-year-old woman with end-stage renal disease on hemodialysis, who developed unstable angina due to distal critical left main disease, with involvement of the origin of both the LAD and the circumflex branch. Angina did not stabilize with medical therapy; the patient was denied surgery because of a prohibitively high surgical risk. A bifurcation stenting procedure was performed with no acute complications, a satisfactory one-month angiographic follow-up and no recurrence of angina until the death of the patient 4 months after the procedure for extracardiac reasons. As indicated by a recent paper by M. Leon, we likewise suggest that left main disease (especially in its simpler proximal variants) may actually be a good target for state-of-the-art transcatheter interventions, including primary stenting, under close angiographic follow-up and careful positive (instead of negative) selection of patients.

Molecular and cellular aspects of induced thymus development in recombinase-deficient mice

Thymus development and microenvironment organization require stage- and site-specific cross-talk between thymocyte and stroma. In this study we have used recombinase-activating gene-deficient (RAG-2(-/-)) mice to analyze regulated gene expression both in thymocytes and stromal cells following injection of anti-CD3 monoclonal antibodies as inducer of thymus development. We show that IFN-gamma, TNF-alpha and lymphotactin are transcriptionally regulated in thymocytes, whereas cytoskeletal keratin 14, IL-1alpha and TNF-alpha are regulated in the stroma, quantitatively reproducing the variations associated with beta selection of thymocytes. In addition, RAG-2(-/-) thymus development is associated with entry of epithelial cells into the cell cycle. The histochemical evidence that expanded RAG-2(-/-) thymus becomes undistinguishable from wild-type cortex further suggests that cross-talk phenomena occurring during beta selection of thymocyte are reproduced in this system.

Surface Expression and Functional Competence of CD3-Independent TCR ζ-Chains in Immature Thymocytes

In recombinase-deficient (RAG-2−/−) mice, double-negative thymocytes can be stimulated to proliferate and differentiate by anti-CD3 Abs. CD3 molecules are expressed on the surface of these cells in association with calnexin. In this study, we show that ζ-chains can be recovered as phosphorylated proteins in association with phosphorylated ZAP-70 from anti-CD3-stimulated RAG-2−/− thymocytes, even though they are not demonstrably associated with the CD3/calnexin complex. The lack of a physical association of ζ dimers with the CD3 complex in RAG-2−/− thymocytes and also in a pre-TCR-expressing cell line, as well as the efficient association of ζ dimers with ZAP-70 in the RAG-2−/− thymocytes, suggest that these ζ-chain dimers could contribute to pre-TCR signaling. This idea is supported by the finding that in RAG-2−/− ζ-deficient thymocytes, ZAP-70 and p120cbl were only weakly phosphorylated.

Surface expression and functional competence of CD3-independent TCR zeta-chains in immature thymocytes

In recombinase-deficient (RAG-2-/-) mice, double-negative thymocytes can be stimulated to proliferate and differentiate by anti-CD3 Abs. CD3 molecules are expressed on the surface of these cells in association with calnexin. In this study, we show that zeta-chains can be recovered as phosphorylated proteins in association with phosphorylated ZAP-70 from anti-CD3-stimulated RAG-2-/- thymocytes, even though they are not demonstrably associated with the CD3/calnexin complex. The lack of a physical association of zeta dimers with the CD3 complex in RAG-2-/- thymocytes and also in a pre-TCR-expressing cell line, as well as the efficient association of zeta dimers with ZAP-70 in the RAG-2-/- thymocytes, suggest that these zeta-chain dimers could contribute to pre-TCR signaling. This idea is supported by the finding that in RAG-2-/- zeta-deficient thymocytes, ZAP-70 and p120cbl were only weakly phosphorylated.

GKLF in thymus epithelium as a developmentally regulated element of thymocyte-stroma cross-talk

Gut-enriched Krüppel-like factor (GKLF) is a transcriptional regulator expressed in differentiated epithelia. We identified GKLF transcript as a regulated element in thymic epithelium of recombinase-deficient mice during thymus development induced by anti-CD3 antibody injection. This treatment recapitulates the organogenetic process depending on productive rearrangement of T cell receptor (TCR) beta gene with thymocytes expansion and acquisition of the CD4+8+ double positive phenotype. In wildtype mice, GKLF is expressed very early in embryogenesis and becomes intensely up-regulated in thymus epithelium at day 18 of gestation when TCR beta expressing cells have selectively expanded and express both CD4 and CD8. The results presented here suggest that thymocytes may regulate GKLF transcriptionally in the cortical epithelium at the developmental check-point controlled by TCR beta gene rearrangement. Furthermore, GKLF expression in hematopoietic stroma might suggest the thus far uncharacterised participation of this factor in hematopoiesis.

Epithelial V-like antigen (EVA), a novel member of the immunoglobulin superfamily, expressed in embryonic epithelia with a potential role as homotypic adhesion molecule in thymus histogenesis

Thymus development depends on a complex series of interactions between thymocytes and the stromal component of the organ. To identify regulated genes during this codependent developmental relationship, we have applied an RNA fingerprinting technique to the analysis of thymus expansion and maturation induced in recombinase-deficient mice injected with anti-CD3 antibodies. This approach led us to the identification of a gene encoding a new member of the immunoglobulin superfamily, named epithelial V-like antigen (EVA), which is expressed in thymus epithelium and strongly downregulated by thymocyte developmental progression. This gene is expressed in the thymus and in several epithelial structures early in embryogenesis. EVA is highly homologous to the myelin protein zero and, in thymus-derived epithelial cell lines, is poorly soluble in nonionic detergents, strongly suggesting an association to the cytoskeleton. Its capacity to mediate cell adhesion through a homophilic interaction and its selective regulation by T cell maturation might imply the participation of EVA in the earliest phases of thymus organogenesis.