The circular life of viruses

Les ARN circulaires (ARNcirc) font partie intégrante de la relation hôte-pathogène. Après la description de la dérégulation d’ARNcirc cellulaires lors d’infections virales, de nombreux ARNcirc d’origine virale ont été identifiés et caractérisés. Des rôles régulateurs, aussi bien du cycle cellulaire que du cycle viral, leur ont été attribués. Ils sont associés à l’oncogenèse viro-induite, à la régulation du système immunitaire et à la différenciation cellulaire. Ces boucles d’ARN, aussi archaïques que les premiers virus, réservent bien des surprises aux chercheurs tant au niveau de leurs fonctions que de leurs biogenèses !Circular RNAs (circRNA), as ancient as the first viruses, take an important part in the host-pathogen relationship. After the first description of dysregulated cellular circRNAs upon viral infection, numerous circRNAs of viral origin were identified and characterized. They are impacting both viral and cellular cycles and are associated with virus-induced oncogenesis, immune system regulation and cell differentiation. While the naïve reader might get swamped by discovering this new field of RNA biology, it seems that these RNA rings are actually full of surprises and wonders at both a functional and a biogenesis level

Marek's disease:Genetic regulation of gallid herpesvirus 2 infection and latency

International audienceGallid herpesvirus-2 (GaHV-2) is an oncogenic α-herpesvirus that causes Marek's disease (MD), a T cell lymphosarcoma (lymphoma) of domestic fowl (chickens). The GaHV-2 genome integrates by homologous recombination into the host genome and, by modulating expression of viral and cellular genes, induces transformation of latently infected cells. MD is a unique model of viral oncogenesis. Mechanisms implicated in the regulation of viral and cellular genes during GaHV-2 infection operate at transcriptional, post-transcriptional and post-translational levels, with involvement of viral and cellular transcription factors, along with epigenetic modifications, alternative splicing, microRNAs and post-translational modifications of viral proteins. Meq, the major oncogenic protein of GaHV-2, is a viral transcription factor that modulates expression of viral genes, for example by binding to the viral bidirectional promoter of the pp38-pp24/1.8 kb mRNA, and also modulates expression of cellular genes, such as Bcl-2 and matrix metalloproteinase 3. GaHV-2 expresses viral telomerase RNA subunit (vTR), which forms a complex with the cellular telomerase reverse transcriptase (TERT), thus contributing to tumorigenesis, while vTR independent of telomerase activity is implicated in metastasis. Expression of a viral interleukin 8 homologue may contribute to lymphomagenesis. Inhibition of expression of the pro-apoptotic factors JARID2 and SMAD2 by viral microRNAs may promote the survival and proliferation of GaHV-2 latently infected cells, thus enhancing tumorigenesis, while inhibition of interleukin 18 by viral microRNAs may be involved in evasion of immune surveillance. Viral envelope glycoproteins derived from glycoprotein B (gp60 and gp49), as well as glycoprotein C, may also play a role in immune evasion

Absence of SARS-CoV-2 in the effluent of peritoneal dialysis patients.

The pandemic of respiratory disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is life-threatening in peritoneal dialysis (PD) patients. In PD patients with systemic viral infections, peritoneal effluent may be theoretically contaminated. We searched for the presence of SARS-CoV-2 genetic material by real-time reverse transcriptase-polymerase chain reaction assays in serial PD effluents of three PD infected patients. Nasopharyngeal swabs obtained at admission showed high viral load in all three patients, whereas none of the PD effluent specimen tested positive, even after dialysate concentration. Those results support at most a very low SARS-CoV-2 dissemination risk by the peritoneal effluent of PD patients. Imposing special disposal procedures, such as the instillation of hypochlorite in the drainage bags to prevent viral spread to health-care workers, are probably not required

Magnetic resonance imaging (MRI) anatomy of the ovine stifle.

3T MRI provided well defined reference images for menisci, synovial cavities, and most ligaments