Anti-CRISPR Protein AcrIIC5 Inhibits CRISPR-Cas9 by Occupying the Target DNA Binding Pocket.

Anti-CRISPR proteins inhibit CRISPR-Cas immune systems through diverse mechanisms. Previously, the anti-CRISPR protein AcrIIC5Smu was shown to potently inhibit a type II-C Cas9 from Neisseria meningitidis (Nme1Cas9). In this work, we explore the mechanism of activity of the AcrIIC5 homologue from Neisseria chenwenguii (AcrIIC5Nch) and show that it prevents Cas9 binding to target DNA. We show that AcrIIC5Nch targets the PAM-interacting domain (PID) of Nme1Cas9 for inhibition, agreeing with previous findings for AcrIIC5Smu, and newly establish that strong binding of the anti-CRISPR requires guide RNA be pre-loaded on Cas9. We determined the crystal structure of AcrIIC5Nch using X-ray crystallography and identified amino acid residues that are critical for its function. Using a protein docking algorithm we show that AcrIIC5Nch likely occupies the Cas9 DNA binding pocket, thereby inhibiting target DNA binding through a mechanism similar to that previously described for AcrIIA2 and AcrIIA4.

Safety and Efficacy of Mavrilimumab For Rheumatoid Arthritis: A Systematic Review and Meta-Analysis.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease characterized by progressive swelling and stiffness in the joints. Mavrilimumab is a human monoclonal antibody that may block the autoimmune mechanism of the antibodies causing RA. OBJECTIVE: We aim to assess the safety and efficacy of Mavrilimumab in treating rheumatoid arthritis. METHODS: We conducted an online search using PubMed, Scopus, Web of Science, and Cochrane CENTRAL till June 2019, and updated the search in May 2020, using relevant keywords. We screened studies for eligibility. Data were extracted from eligible studies and pooled as Risk ratio (RR) with a 95% confidence interval (CI), using Review Manager software (ver.3.5). RESULTS: Five studies (with 1145 patients) were eligible to our criteria. Pooled result from three trials showed a significant reduction in Disease Activity Score 28 based on C-reactive protein (DAS28-CRP) remission < 2.6 after 12 weeks (RR = 3.31, 95% CI [1.53, 7.18], P = 0.002), American College of Rheumatology (ACR) 20, after 12 weeks (RR = 2.38, 95% CI [1.80, 3.16], P < 0.00001), ACR 50, after 12 weeks (RR = 2.93, 95% CI [1.67, 5.15], P = 0.0002), ACR 70, after 12 weeks (RR = 4.90, 95% CI [1.60, 15.00], P = 0.005). Mavrilimumab not associated with a significant adverse event (RR = 1.22, 95% CI [0.89, 1.68], P = 0.22). CONCLUSION: We found that subcutaneous Mavrilimumab was effective and well-tolerating in treating RA patients, with no significant adverse events.