+1 Frameshifting as a Novel Mechanism to Generate a Cryptic Cytotoxic T Lymphocyte Epitope Derived from Human Interleukin 10

Recent data indicate that some cytotoxic T cells (CTLs) recognize so-called cryptic epitopes, encoded by nonprimary open reading frame (ORF) sequences or other nonclassical expression pathways. We describe here a novel mechanism leading to generation of a cryptic CTL epitope. We isolated from the synovial fluid of a patient suffering from a Reiter's syndrome an autoreactive T cell clone that recognized cellular IL-10 in the HLA-B*2705 context. The minimal IL-10 sequence corresponding to nucleotides 379–408 was shown to activate this clone, upon cotransfection into COS cells with the DNA encoding HLA-B*2705, but the synthetic peptide deduced from this sequence did not stimulate the clone. Using a site-directed mutagenesis approach, we found that this clone recognized a transframe epitope generated by an internal +1 frameshifting in the IL-10 sequence and so derived partly from ORF1, partly from ORF2. We defined that +1 frameshifting was induced by a specific heptamer sequence. These observations illustrate the variety of mechanisms leading to generation of cryptic epitopes and suggest that frameshifting in normal cellular genes may be more common than expected

Human Cytomegalovirus Entry into Dendritic Cells Occurs via a Macropinocytosis-Like Pathway in a pH-Independent and Cholesterol-Dependent Manner

Human cytomegalovirus (HCMV) is a ubiquitous herpesvirus that is able to infect fibroblastic, epithelial, endothelial and hematopoietic cells. Over the past ten years, several groups have provided direct evidence that dendritic cells (DCs) fully support the HCMV lytic cycle. We previously demonstrated that the C-type lectin dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) has a prominent role in the docking of HCMV on monocyte-derived DCs (MDDCs). The DC-SIGN/HCMV interaction was demonstrated to be a crucial and early event that substantially enhanced infection in trans, i.e., from one CMV-bearing cell to another non-infected cell (or trans-infection), and rendered susceptible cells fully permissive to HCMV infection. Nevertheless, nothing is yet known about how HCMV enters MDDCs. In this study, we demonstrated that VHL/E HCMV virions (an endothelio/dendrotropic strain) are first internalized into MDDCs by a macropinocytosis-like process in an actin- and cholesterol-dependent, but pH-independent, manner. We observed the accumulation of virions in large uncoated vesicles with endosomal features, and the virions remained as intact particles that retained infectious potential for several hours. This trans-infection property was specific to MDDCs because monocyte-derived macrophages or monocytes from the same donor were unable to allow the accumulation of and the subsequent transmission of the virus. Together, these data allowed us to delineate the early mechanisms of the internalization and entry of an endothelio/dendrotropic HCMV strain into human MDDCs and to propose that DCs can serve as a "Trojan horse" to convey CMV from entry sites to other locations that may favor the occurrence of either latency or acute infection

Différenciation et modification génétique des cellules dendritiques en vue de l'élaboration d'un modèle d'étude "ex-vivo" du rôle de DC-SIGN et de la langérine dans les étapes précoces de l'infection des cellules dendritiques par le CMV

NANTES-BU Sciences (441092104) / SudocSudocFranceF

Infectious Diseases in Transplantation—Report of the 20th Nantes Actualités Transplantation Meeting

International audienceThe 20th Nantes Actualités Transplantation (NAT) meeting was held on June 11, 2015, and June 12, 2015. This year, the local organizing committee selected an update on infectious diseases in solid organ and hematopoietic stem cell transplanta-tion. With an attendance of close to 170 clinicians, researchers, students, engineers, technicians, invited speakers, and guests from North and South America, Germany, Switzerland, Netherlands, and France, the meeting was well attended. Invited speakers' expertise covered basic as well as translational microbiology, immunology, transplantation, and intensive care medicine. This report identifies a number of advances presented during the meeting in the care and management of infectious diseases in transplanta-tion and immunocompromised patients. New antiviral immune responses and their modulation by pathogens in addition to novel antimicrobial therapeutic strategies, cell therapies, and genomic analysis were discussed

Intra-patient viral evolution in polyomavirus-related diseases

International audienceHuman polyomaviruses show relatively little genetic polymorphism between isolates, indicating that these viruses are genetically stable between hosts. However, it has become increasingly clear that intra-host molecular evolution is a feature of some polyomavirus (PyV) infections in humans. Mutations inducing premature stop codons in the early region of the integrated Merkel cell PyV genome lead to the expression of a truncated form of the large tumour (LT) antigen that is critical for the transformation of Merkel cell carcinoma (MCC) cells. Non-coding control region (NCCR) rearrangements and point mutations in virion protein (VP) 1 have been described in both JCPyV and BKPyV infections. In the context of JCPyV infection, molecular evolution at both these loci allows the virus to replicate effectively in the central nervous system, thereby leading to the development of progressive multifocal leukoencephalopathy (PML). In BKPyV infection, NCCR rearrangements have been linked to higher rates of virus replication in the kidney, and are proposed to play a direct causal role in the development of PyV-associated nephropathy. In all three of these infections, therefore, intra-host viral evolution appears to be an essential component of the disease process. This article is part of the theme issue 'Silent cancer agents: multi-disciplinary modelling of human DNA oncoviruses'

Intra-patient viral evolution in polyomavirus-related diseases

Human polyomaviruses show relatively little genetic polymorphism between isolates, indicating that these viruses are genetically stable between hosts. However, it has become increasingly clear that intra-host molecular evolution is a feature of some polyomavirus (PyV) infections in humans. Mutations inducing premature stop codons in the early region of the integrated Merkel cell PyV genome lead to the expression of a truncated form of the large tumour (LT) antigen that is critical for the transformation of Merkel cell carcinoma (MCC) cells. Non-coding control region (NCCR) rearrangements and point mutations in virion protein (VP) 1 have been described in both JCPyV and BKPyV infections. In the context of JCPyV infection, molecular evolution at both these loci allows the virus to replicate effectively in the central nervous system, thereby leading to the development of progressive multifocal leukoencephalopathy (PML). In BKPyV infection, NCCR rearrangements have been linked to higher rates of virus replication in the kidney, and are proposed to play a direct causal role in the development of PyV-associated nephropathy. In all three of these infections, therefore, intra-host viral evolution appears to be an essential component of the disease process. This article is part of the theme issue ‘Silent cancer agents: multi-disciplinary modelling of human DNA oncoviruses’.</jats:p

The degradation of gelatin/alginate/fibrin hydrogels is cell type dependent and can be modulated by targeting fibrinolysis

In tissue engineering, cell origin is important to ensure outcome quality. However, the impact of the cell type chosen for seeding in a biocompatible matrix has been less investigated. Here, we investigated the capacity of primary and immortalized fibroblasts of distinct origins to degrade a gelatin/alginate/fibrin (GAF)-based biomaterial. We further established that fibrin was targeted by degradative fibroblasts through the secretion of fibrinolytic matrix-metalloproteinases (MMPs) and urokinase, two types of serine protease. Finally, we demonstrated that besides aprotinin, specific targeting of fibrinolytic MMPs and urokinase led to cell-laden GAF stability for at least forty-eight hours. These results support the use of specific strategies to tune fibrin-based biomaterials degradation over time. It emphasizes the need to choose the right cell type and further bring targeted solutions to avoid the degradation of fibrin-containing hydrogels or bioinks