Limited Effects of Class II Transactivator-Based Immunotherapy in Murine and Human Glioblastoma.

BACKGROUND: The major histocompatibility complex type II is downregulated in glioblastoma (GB) due to the silencing of the major transcriptional regulator class II transactivator (CIITA). We investigated the pro-immunogenic potential of CIITA overexpression in mouse and human GB. METHODS: The intracerebral growth of wildtype GL261-WT cells was assessed following contralateral injection of GL261-CIITA cells or flank injections with GL261-WT or GL261-CIITA cells. Splenocytes obtained from mice implanted intracerebrally with GL261-WT, GL261-CIITA cells or phosphate buffered saline (PBS) were transferred to other mice and subsequently implanted intracerebrally with GL261-WT. Human GB cells and (syngeneic) GB-infiltrating immune cells were isolated from surgical samples and co-cultured with GB cells expressing CIITA or not, followed by RT-qPCR assessment of the expression of key immune regulators. RESULTS: Intracerebral vaccination of GL261-CIITA significantly reduced the subsequent growth of GL261-WT cells implanted contralaterally. Vaccination with GL261-WT or -CIITA subcutaneously, however, equivalently retarded the intracerebral growth of GL261 cells. Adoptive cell transfer experiments showed a similar antitumor potential of lymphocytes harvested from mice implanted intracerebrally with GL261-WT or -CIITA. Human GB-infiltrating myeloid cells and lymphocytes were not activated when cultured with CIITA-expressing GB cells. Tumor-infiltrating NK cells remained mostly inactivated when in co-culture with GB cells, regardless of CIITA. CONCLUSION: these results question the therapeutic potential of CIITA-mediated immunotherapy in glioblastoma.

Predictors of neutralizing antibody response to BNT162b2 vaccination in allogeneic hematopoietic stem cell transplant recipients.

BACKGROUND: Factors affecting response to SARS-CoV-2 mRNA vaccine in allogeneic hematopoietic stem cell transplantation (allo-HCT) recipients remain to be elucidated. METHODS: Forty allo-HCT recipients were included in a study of immunization with BNT162b2 mRNA vaccine at days 0 and 21. Binding antibodies (Ab) to SARS-CoV-2 receptor binding domain (RBD) were assessed at days 0, 21, 28, and 49 while neutralizing Ab against SARS-CoV-2 wild type (NT50) were assessed at days 0 and 49. Results observed in allo-HCT patients were compared to those obtained in 40 healthy adults naive of SARS-CoV-2 infection. Flow cytometry analysis of peripheral blood cells was performed before vaccination to identify potential predictors of Ab responses. RESULTS: Three patients had detectable anti-RBD Ab before vaccination. Among the 37 SARS-CoV-2 naive patients, 20 (54%) and 32 (86%) patients had detectable anti-RBD Ab 21 days and 49 days postvaccination. Comparing anti-RBD Ab levels in allo-HCT recipients and healthy adults, we observed significantly lower anti-RBD Ab levels in allo-HCT recipients at days 21, 28 and 49. Further, 49% of allo-HCT patients versus 88% of healthy adults had detectable NT50 Ab at day 49 while allo-HCT recipients had significantly lower NT50 Ab titers than healthy adults (P = 0.0004). Ongoing moderate/severe chronic GVHD (P < 0.01) as well as rituximab administration in the year prior to vaccination (P < 0.05) correlated with low anti-RBD and NT50 Ab titers at 49 days after the first vaccination in multivariate analyses. Compared to healthy adults, allo-HCT patients without chronic GVHD or rituximab therapy had comparable anti-RBD Ab levels and NT50 Ab titers at day 49. Flow cytometry analyses before vaccination indicated that Ab responses in allo-HCT patients were strongly correlated with the number of memory B cells and of naive CD4+ T cells (r > 0.5, P < 0.01) and more weakly with the number of follicular helper T cells (r = 0.4, P = 0.01). CONCLUSIONS: Chronic GVHD and rituximab administration in allo-HCT recipients are associated with reduced Ab responses to BNT162b2 vaccination. Immunological markers could help identify allo-HCT patients at risk of poor Ab response to mRNA vaccination. TRIAL REGISTRATION: The study was registered at clinicaltrialsregister.eu on 11 March 2021 (EudractCT # 2021-000673-83).

New role of osteopontin in DNA repair and impact on human glioblastoma radiosensitivity.

Glioblastoma (GBM) represents the most aggressive and common solid human brain tumor. We have recently demonstrated the importance of osteopontin (OPN) in the acquisition/maintenance of stemness characters and tumorigenicity of glioma initiating cells. Consultation of publicly available TCGA database indicated that high OPN expression correlated with poor survival in GBM patients. In this study, we explored the role of OPN in GBM radioresistance using an OPN-depletion strategy in U87-MG, U87-MG vIII and U251-MG human GBM cell lines. Clonogenic experiments showed that OPN-depleted GBM cells were sensitized to irradiation. In comet assays, these cells displayed higher amounts of unrepaired DNA fragments post-irradiation when compared to control. We next evaluated the phosphorylation of key markers of DNA double-strand break repair pathway. Activating phosphorylation of H2AX, ATM and 53BP1 was significantly decreased in OPN-deficient cells. The addition of recombinant OPN prior to irradiation rescued phospho-H2AX foci formation thus establishing a new link between DNA repair and OPN expression in GBM cells. Finally, OPN knockdown improved mice survival and induced a significant reduction of heterotopic human GBM xenograft when combined with radiotherapy. This study reveals a new function of OPN in DNA damage repair process post-irradiation thus further confirming its major role in GBM aggressive disease.

Targeting osteopontin suppresses glioblastoma stem-like cell character and tumorigenicity in vivo.

Osteopontin (OPN) is a secreted protein involved in most aspects of tumor progression and metastasis development. Elevated OPN expression has been reported in multiple types of cancer including glioblastoma (GBM), the highest grade and most aggressive brain tumor. GBMs contain a subpopulation of glioma-initiating cells (GICs) implicated in progression, therapeutic resistance and recurrence. We have previously demonstrated that OPN silencing inhibited GBM cell growth in vitro and in vivo. Moreover, activation of CD44 signaling upon OPN ligation has been recently implicated in the acquisition of a stem cell phenotype by GBM cells. The present study is aimed to explore OPN autocrine function using shRNA silencing strategy in GICs enriched from GBM cell lines and a human primary GBM grown in EGF and bFGF defined medium. The removal of these growth factors and addition of serum induced a significant loss of OPN expression in GICs. We showed that OPN-silenced GICs were unable to grow as spheres and this capacity was restored by exogenous OPN. Importantly, the expression of Sox2, Oct3/4 and Nanog, key stemness transcription factors, was significantly decreased in GICs upon OPN targeting. We identified Akt/mTOR/p70S6K as the main signaling pathway triggered following OPN-mediated EGFR activation in GICs. Finally, in an orthotopic xenograft mouse model, the tumorigenic potential of U87-MG sphere cells was completely abrogated upon OPN silencing. Our demonstration of endogenous OPN major regulatory effects on GICs stemness phenotype and tumorigenicity implies a greater role than anticipated for OPN in GBM pathogenesis from initiation and progression to probable recurrence.

[SIBLING proteins: molecular tools for tumor progression and angiogenesis]. / Les protéines SIBLING - Outils moléculaires de la progression tumorale et de l'angiogenèse.

The small integrin-binding ligand N-linked glycoprotein (SIBLING) family consists of osteopontin (OPN), bonesialoprotein (BSP), dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP) and matrix extracellular phosphoglycoprotein (MEPE). These proteins, initially identified in bone and teeth, share many structural characteristics. It is now well established that they are over expressed in many tumors and play a critical role at different steps of cancer development. In this review, we describe the roles of SIBLING proteins at different stages of cancer progression including cancer cell adhesion, proliferation, migration, invasion, metastasis and angiogenesis.

An alternative method to determine the 5' extremities of non-segmented, negative sense RNA viral genomes using positive replication intermediate 3' tailing: application to two members of the Paramyxoviridae family.

Determining the sequence of non-segmented, negative sense RNA viral genomes is far from routine and often requires the application of several techniques. In this study, an existing method used currently just for determination of the genomic 3' extremity was used to determine both the 3' and 5' sequence extremities of a Newcastle disease virus and an avian metapneumovirus. This was achieved with a single 3' nucleotide tailing reaction of both the genomic RNA and the full length, positive sense, antigenomic RNA, followed by a single reverse transcription reaction targeted to the common polynucleotide tails, and then individual PCRs specific for each extremity using PCR primers derived from the sequence of the RT primer or from neighbouring virus sequences known previously. For each virus the method was employed separately. Sequences from both viruses were in agreement with those reported previously for other paramyxoviruses, yet one extra base at the 3' and one extra base at the 5' were identified for the avian metapneumovirus. In this study, importantly, the newly determined extremities maintained the complementarity known to exist between the extremities of these viruses. The method was equally successful with both viruses and can be tailored easily to function with other non-segmented, negative sense viruses through minor modification of only the primer sequences.

Complete genome sequence of a newcastle disease virus strain belonging to a recently identified genotype.

We report the first complete genome sequence of a strain that presents some pathogenicity and that belongs to a recently characterized genotype of avian paramyxovirus type 1 (APMV-1). This virus, isolated from the common teal, presents the most divergent genome within class I of APMV-1.

The protective immune response against Pseudorabies virus induced by DNA vaccination is impaired if the plasmid harbors a functional Porcine circovirus type 2 rep and origin of replication.

A plasmid rendered replicative in mammalian cells by inserting the Porcine circovirus 2 (PCV2) origin of replication and replicase gene (Ori-rep) has been previously constructed. The aim of the present study was to evaluate if the replication capacity of this plasmid could be advantageously used to improve the protective immunity induced by DNA vaccination. In this case we used the porcine Pseudorabies virus (PrV) DNA vaccination model. The replicative capacity of the DNA vaccine did not improve the protective immunity against PrV in pigs, but on the contrary the presence of the PCV2 Ori-rep sequence was harmful in the induction of this immunity compared to an equivalent but non-replicative DNA vaccine. In addition, the distribution and the persistence of the replicative and non-replicative plasmids inside the body were the same. This is the first study showing an in vivo deleterious effect of the replicative active PCV2 Ori-rep on the natural and specific protection against PrV infection.

Complete genome sequence of a novel avian paramyxovirus.

We report here the complete genome of a new avian paramyxovirus (APMV-11) isolated from common snipes. Sequence data from this virus showed that it has the largest genome of APMV and unusual P gene mRNA editing.

Replication efficiency of rolling-circle replicon-based plasmids derived from porcine circovirus 2 in eukaryotic cells.

In this study, a method was developed to measure replication rates of rolling-circle replicon-based plasmids in eukaryotic cells. This method is based on the discriminative quantitation of MboI-resistant, non-replicated input plasmids and DpnI-resistant, replicated plasmids. To do so, porcine circovirus type 2 (PCV2) replicon-based plasmids were constructed. These plasmids contained the PCV2 origin of replication, the PCV2 Rep promoter and the PCV2 Rep gene. The results show that the replication rate depends on the length of the PCV2 replicon-based plasmid and not on the respective position of the Rep promoter and the promoter of the gene of interest that encodes the enhanced green fluorescent protein (eGFP). In all cases, it was necessary to add the Rep gene encoded by a plasmid and cotransfected as a replication booster. This method can evaluate the replication potential of replicon-based plasmids quickly and is thereby a promising tool for the development of plasmids for vaccine purposes.