An entropic safety catch controls hepatitis C virus entry and antibody resistance.

E1 and E2 (E1E2), the fusion proteins of Hepatitis C Virus (HCV), are unlike that of any other virus yet described, and the detailed molecular mechanisms of HCV entry/fusion remain unknown. Hypervariable region-1 (HVR-1) of E2 is a putative intrinsically disordered protein tail. Here, we demonstrate that HVR-1 has an autoinhibitory function that suppresses the activity of E1E2 on free virions; this is dependent on its conformational entropy. Thus, HVR-1 is akin to a safety catch that prevents premature triggering of E1E2 activity. Crucially, this mechanism is turned off by host receptor interactions at the cell surface to allow entry. Mutations that reduce conformational entropy in HVR-1, or genetic deletion of HVR-1, turn off the safety catch to generate hyper-reactive HCV that exhibits enhanced virus entry but is thermally unstable and acutely sensitive to neutralising antibodies. Therefore, the HVR-1 safety catch controls the efficiency of virus entry and maintains resistance to neutralising antibodies. This discovery provides an explanation for the ability of HCV to persist in the face of continual immune assault and represents a novel regulatory mechanism that is likely to be found in other viral fusion machinery.

Application of error-prone PCR to functionally probe the morbillivirus Haemagglutinin protein.

The enveloped morbilliviruses utilise conserved proteinaceous receptors to enter host cells: SLAMF1 or Nectin-4. Receptor binding is initiated by the viral attachment protein Haemagglutinin (H), with the viral Fusion protein (F) driving membrane fusion. Crystal structures of the prototypic morbillivirus measles virus H with either SLAMF1 or Nectin-4 are available and have served as the basis for improved understanding of this interaction. However, whether these interactions remain conserved throughout the morbillivirus genus requires further characterisation. Using a random mutagenesis approach, based on error-prone PCR, we targeted the putative receptor binding site for SLAMF1 interaction on peste des petits ruminants virus (PPRV) H, identifying mutations that inhibited virus-induced cell-cell fusion. These data, combined with structural modelling of the PPRV H and ovine SLAMF1 interaction, indicate this region is functionally conserved across all morbilliviruses. Error-prone PCR provides a powerful tool for functionally characterising functional domains within viral proteins.

Interactions of Viral Proteins from Pathogenic and Low or Non-Pathogenic Orthohantaviruses with Human Type I Interferon Signaling.

Rodent-borne orthohantaviruses are asymptomatic in their natural reservoir, but they can cause severe diseases in humans. Although an exacerbated immune response relates to hantaviral pathologies, orthohantaviruses have to antagonize the antiviral interferon (IFN) response to successfully propagate in infected cells. We studied interactions of structural and nonstructural (NSs) proteins of pathogenic Puumala (PUUV), low-pathogenic Tula (TULV), and non-pathogenic Prospect Hill (PHV) viruses, with human type I and III IFN (IFN-I and IFN-III) pathways. The NSs proteins of all three viruses inhibited the RIG-I-activated IFNß promoter, while only the glycoprotein precursor (GPC) of PUUV, or its cleavage product Gn/Gc, and the nucleocapsid (N) of TULV inhibited it. Moreover, the GPC of both PUUV and TULV antagonized the promoter of IFN-stimulated responsive elements (ISRE). Different viral proteins could thus contribute to inhibition of IFNß response in a viral context. While PUUV and TULV strains replicated similarly, whether expressing entire or truncated NSs proteins, only PUUV encoding a wild type NSs protein led to late IFN expression and activation of IFN-stimulated genes (ISG). This, together with the identification of particular domains of NSs proteins and different biological processes that are associated with cellular proteins in complex with NSs proteins, suggested that the activation of IFN-I is probably not the only antiviral pathway to be counteracted by orthohantaviruses and that NSs proteins could have multiple inhibitory functions.

Efficacy and Non Invasive Treatment of Sialorrhea in the Goldenhar Syndrome.

BACKGROUND AND OBJECTIVE: Goldenhar syndrome (ocular-auricular-vertebral syndrome), a rare congenital condition arising from defects in the first and second brachial arches, consists in clinical variety of features ranging from facial abnormalities, ear-eye abnormalities, vertebral defects and congenital heart problems and severe obstructive sleep apnea. Due to craniofacial abnormalities, patients presents mechanical obstructive phenomena and sialorrhea that cause prone position, language's fastening, use of nasopharyngeal cannulas and tracheal intubation. METHODS: In this article, we report a case of a 16 years old child affected by Goldenhar syndrome and sialorrhea to demonstrate improvement of the daily patient management, through inoculations of botulinum toxin type A. Due to severe sialorrhea which caused tracheobronchial daily aspirations, the caregivers used an external aspirators. RESULTS: In the first infiltration (August 2016) the parotid and submandibular glands bilaterally were inoculated with incobotulinum toxin type A (Xeomin®, Merz Pharma) with dosages of 5 UI for each of them, for a total of 20 UI without clinical efficacy (no quantitative and qualitative saliva reducing during 3 months). In the second (November 2016) and third (February 2017) infiltrations each parotid and each submandibular glands were injected with a (dosage of 7 UI and 5 UI respectively (total of 24 UI of incobotulinumtoxin A) with important clinical results (saliva production and tracheo-bronchial aspirations reduced). CONCLUSION: Therefore, botulinum toxin type A could be a good and non invasive treatment of sialorrhea in Goldenhar syndrome to improve oral hygiene and daily patient management.