Cryo-EM structures of Banna virus in multiple states reveal stepwise detachment of viral spikes.

Banna virus (BAV) is the prototype Seadornavirus, a class of reoviruses for which there has been little structural study. Here, we report atomic cryo-EM structures of three states of BAV virions-surrounded by 120 spikes (full virions), 60 spikes (partial virions), or no spikes (cores). BAV cores are double-layered particles similar to the cores of other non-turreted reoviruses, except for an additional protein component in the outer capsid shell, VP10. VP10 was identified to be a cementing protein that plays a pivotal role in the assembly of BAV virions by directly interacting with VP2 (inner capsid), VP8 (outer capsid), and VP4 (spike). Viral spikes (VP4/VP9 heterohexamers) are situated on top of VP10 molecules in full or partial virions. Asymmetrical electrostatic interactions between VP10 monomers and VP4 trimers are disrupted by high pH treatment, which is thus a simple way to produce BAV cores. Low pH treatment of BAV virions removes only the flexible receptor binding protein VP9 and triggers significant conformational changes in the membrane penetration protein VP4. BAV virions adopt distinct spatial organization of their surface proteins compared with other well-studied reoviruses, suggesting that BAV may have a unique mechanism of penetration of cellular endomembranes.

Neutralizing monoclonal antibodies against the Gc fusion loop region of Crimean-Congo hemorrhagic fever virus.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a highly pathogenic tick-borne virus, prevalent in more than 30 countries worldwide. Human infection by this virus leads to severe illness, with an average case fatality of 40%. There is currently no approved vaccine or drug to treat the disease. Neutralizing antibodies are a promising approach to treat virus infectious diseases. This study generated 37 mouse-derived specific monoclonal antibodies against CCHFV Gc subunit. Neutralization assays using pseudotyped virus and authentic CCHFV identified Gc8, Gc13, and Gc35 as neutralizing antibodies. Among them, Gc13 had the highest neutralizing activity and binding affinity with CCHFV Gc. Consistently, Gc13, but not Gc8 or Gc35, showed in vivo protective efficacy (62.5% survival rate) against CCHFV infection in a lethal mouse infection model. Further characterization studies suggested that Gc8 and Gc13 may recognize a similar, linear epitope in domain II of CCHFV Gc, while Gc35 may recognize a different epitope in Gc. Cryo-electron microscopy of Gc-Fab complexes indicated that both Gc8 and Gc13 bind to the conserved fusion loop region and Gc13 had stronger interactions with sGc-trimers. This was supported by the ability of Gc13 to block CCHFV GP-mediated membrane fusion. Overall, this study provides new therapeutic strategies to treat CCHF and new insights into the interaction between antibodies with CCHFV Gc proteins.

Psychometric properties of patient-reported outcome measures assessing self-efficacy in patients with inflammatory bowel disease: A systematic review.

AIMS: The aim of this study is to conduct a comprehensive evaluation of the patient-reported outcome measure assessing self-efficacy in patients with inflammatory bowel disease, and recommend the most robust measurement. DESIGN: A systematic review of psychometric properties. DATA SOURCES: We performed systematic electronic searches in the following databases from inception to 26 May 2022: PubMed, Embase, CINAHL, Web of Science, Cochrane Library, and PsycINFO via OVID. REVIEW METHOD: This review evaluated the tools' quality in accordance with the Selection of Consensus-Based Health Measurement Instruments 2018 system Evaluation guidelines. RESULTS: Three patient-reported outcome measures were identified in the five included studies. The "IBD-yourself" questionnaire revealed very low evidence for a sufficient hypothesis test for construct validity, moderate evidence for insufficient internal consistency, and very low evidence for uncertain measurement error. Evidence from Inflammatory Bowel Disease Self-Efficacy Scale validated internal consistency, structural validity, criterion validity, and hypothesis test for construct validity. However, evidence of moderate quality corroborated this reliability. The Adolescents and Young Adults Inflammatory Bowel Disease Self-Efficacy Scale demonstrated very low evidence for sufficient internal consistency, moderate evidence for a sufficient hypothesis test for construct and content validity, and very low evidence for uncertain reliability. CONCLUSIONS: Compared with the other two measures, the Inflammatory Bowel Disease Self-Efficacy Scale has higher quality evidence of higher overall ratings for some of its psychometric properties, but there were some methodological problems that must be further studied to determine their quality. IMPACT: It is uncertain whether a scale to assess self-efficacy in patients with inflammatory bowel disease has good measurement performance in clinical applications. This study first presents the methodological quality and psychometric properties of the self-efficacy scale used to assess patients with inflammatory bowel disease, which is based on the Consensus-Based Health Measurement Instruments standard. This study can help researchers and physicians decide which scale is the most suitable and reliable for patients with inflammatory bowel disease. NO PATIENT OR PUBLIC CONTRIBUTION: Because this was a systematic review based on synthesizing information from previous studies, no human participants were included.

Structural transitions during the cooperative assembly of baculovirus single-stranded DNA-binding protein on ssDNA.

Single-stranded DNA-binding proteins (SSBs) interact with single-stranded DNA (ssDNA) to form filamentous structures with various degrees of cooperativity, as a result of intermolecular interactions between neighboring SSB subunits on ssDNA. However, it is still challenging to perform structural studies on SSB-ssDNA filaments at high resolution using the most studied SSB models, largely due to the intrinsic flexibility of these nucleoprotein complexes. In this study, HaLEF-3, an SSB protein from Helicoverpa armigera nucleopolyhedrovirus, was used for in vitro assembly of SSB-ssDNA filaments, which were structurally studied at atomic resolution using cryo-electron microscopy. Combined with the crystal structure of ssDNA-free HaLEF-3 octamers, our results revealed that the three-dimensional rearrangement of HaLEF-3 induced by an internal hinge-bending movement is essential for the formation of helical SSB-ssDNA complexes, while the contacting interface between adjacent HaLEF-3 subunits remains basically intact. We proposed a local cooperative SSB-ssDNA binding model, in which, triggered by exposure to oligonucleotides, HaLEF-3 molecules undergo ring-to-helix transition to initiate continuous SSB-SSB interactions along ssDNA. Unique structural features revealed by the assembly of HaLEF-3 on ssDNA suggest that HaLEF-3 may represent a new class of SSB.

Cryo-EM structure of glycoprotein C from Crimean-Congo hemorrhagic fever virus.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a causative agent of serious hemorrhagic diseases in humans with high mortality rates. CCHFV glycoprotein Gc plays critical roles in mediating virus-host membrane fusion and has been studied extensively as an immunogen. However, the molecular mechanisms involved in membrane fusion and Gc-specific antibody-antigen interactions remain unresolved largely because structural information of this glycoprotein is missing. We designed a trimeric protein including most of the ectodomain region of Gc from the prototype CCHFV strain, IbAr10200, which enabled the cryo-electron microscopy structure to be solved at a resolution of 2.8 â€‹Å. The structure confirms that CCHFV Gc is a class II fusion protein. Unexpectedly, structural comparisons with other solved Gc trimers in the postfusion conformation revealed that CCHFV Gc adopted hybrid architectural features of the fusion loops from hantaviruses and domain III from phenuiviruses, suggesting a complex evolutionary pathway among these bunyaviruses. Antigenic sites on CCHFV Gc that protective neutralizing antibodies target were mapped onto the CCHFV Gc structure, providing valuable information that improved our understanding of potential neutralization mechanisms of various antibodies.