Insight into mode-of-action and structural determinants of the compstatin family of clinical complement inhibitors.

With the addition of the compstatin-based complement C3 inhibitor pegcetacoplan, another class of complement targeted therapeutics have recently been approved. Moreover, compstatin derivatives with enhanced pharmacodynamic and pharmacokinetic profiles are in clinical development (e.g., Cp40/AMY-101). Despite this progress, the target binding and inhibitory modes of the compstatin family remain incompletely described. Here, we present the crystal structure of Cp40 complexed with its target C3b at 2.0-Å resolution. Structure-activity-relationship studies rationalize the picomolar affinity and long target residence achieved by lead optimization, and reveal a role for structural water in inhibitor binding. We provide explanations for the narrow species specificity of this drug class and demonstrate distinct target selection modes between clinical compstatin derivatives. Functional studies provide further insight into physiological complement activation and corroborate the mechanism of its compstatin-mediated inhibition. Our study may thereby guide the application of existing and development of next-generation compstatin analogs.

Research on the Constitutive Model of PTFE/Al/Si Reactive Material.

As a new type of energetic material, reactive materials are widely used at present; in particular, the metal/polymer mixtures type reactive materials show great advantages in engineering applications. This type of reactive material has good mechanical properties, and its overall performance is insensitive and high-energy under external impact loading. After a large number of previous studies, our team found that the energy release characteristics of PTFE/Al/Si reactive material are prominent. In order to master the mechanical properties of PTFE/Al/Si reactive materials, the quasi-static mechanical properties and dynamic mechanical properties were obtained by carrying out a quasi-static compression test and a dynamic SHPB test in this paper. Based on the experimental data, a Johnson-Cook constitutive model of PTFE/Al/Si reactive material considering strain hardening effect, strain rate hardening effect and thermal softening effect was constructed. The relevant research results will be used to guide future research on the reaction mechanism of PTFE/Al/Si reactive materials, in order to promote the engineering application of PTFE/Al/Si reactive materials.

Dose prediction via distance-guided deep learning: Initial development for nasopharyngeal carcinoma radiotherapy.

BACKGROUND AND PURPOSE: Geometric information such as distance information is essential for dose calculations in radiotherapy. However, state-of-the-art dose prediction methods use only binary masks without distance information. This study aims to develop a dose prediction deep learning method for nasopharyngeal carcinoma radiotherapy by taking advantage of the distance information as well as the mask information. MATERIALS AND METHODS: A novel transformation method based on boundary distance was proposed to facilitate the prediction of dose distributions. Radiotherapy datasets of 161 nasopharyngeal carcinoma patients were retrospectively collected, including binary masks of organs-at-risk (OARs) and targets, planning CT, and clinical plans. The patients were randomly divided into 130, 11 and 20 cases for training, validating, and testing the models, respectively. Furthermore, 40 patients from an external cohort were used to test the generalizability of the models. RESULTS: The proposed method shows superior performance. The predicted dose error and dose-volume histogram (DVH) error of our method were 7.51% and 11.6% lower than the mask-based method, respectively. For the inverse planning, compared with mask-based methods, our method provided similar performances on the GTVnx and OARs and outperformed on the GTVnd and the CTV, the pass rates of which increased from 89.490% and 90.016% to 96.694% and 91.189%, respectively. CONCLUSION: The preliminary results on nasopharyngeal carcinoma radiotherapy cases showed that our proposed distance-guided method for dose prediction achieved better performance than mask-based methods. Further studies with more patients and on other cancer sites are warranted to fully validate the proposed method.

Comparative Analysis of Antibodies and Heavily Glycosylated Macromolecular Immune Complexes by Size-Exclusion Chromatography Multi-Angle Light Scattering, Native Charge Detection Mass Spectrometry, and Mass Photometry.

Qualitative and quantitative mass analysis of antibodies and related macromolecular immune complexes is a prerequisite for determining their identity, binding partners, stoichiometries, and affinities. A plethora of bioanalytical technologies exist to determine such characteristics, typically based on size, interaction with functionalized surfaces, light scattering, or direct mass measurements. While these methods are highly complementary, they also exhibit unique strengths and weaknesses. Here, we benchmark mass photometry (MP), a recently introduced technology for mass measurement, against native mass spectrometry (MS) and size exclusion chromatography multi-angle light scattering (SEC-MALS). We examine samples of variable complexity, namely, IgG4Δhinge dimerizing half-bodies, IgG-RGY hexamers, heterogeneously glycosylated IgG:sEGFR antibody-antigen complexes, and finally megadalton assemblies involved in complement activation. We thereby assess the ability to determine (1) binding affinities and stoichiometries, (2) accurate masses, for extensively glycosylated species, and (3) assembly pathways of large heterogeneous immune complexes. We find that MP provides a sensitive approach for characterizing antibodies and stable assemblies, with dissociation correction enabling us to expand the measurable affinity range. In terms of mass resolution and accuracy, native MS performs the best but is occasionally hampered by artifacts induced by electrospray ionization, and its resolving power diminishes when analyzing extensively glycosylated proteins. In the latter cases, MP performs well, but single-particle charge detection MS can also be useful in this respect, measuring masses of heterogeneous assemblies even more accurately. Both methods perform well compared to SEC-MALS, still being the most established method in biopharma. Together, our data highlight the complementarity of these approaches, each having its unique strengths and weaknesses.

Regulator-dependent mechanisms of C3b processing by factor I allow differentiation of immune responses.

The complement system labels microbes and host debris for clearance. Degradation of surface-bound C3b is pivotal to direct immune responses and protect host cells. How the serine protease factor I (FI), assisted by regulators, cleaves either two or three distant peptide bonds in the CUB domain of C3b remains unclear. We present a crystal structure of C3b in complex with FI and regulator factor H (FH; domains 1-4 with 19-20). FI binds C3b-FH between FH domains 2 and 3 and a reoriented C3b C-terminal domain and docks onto the first scissile bond, while stabilizing its catalytic domain for proteolytic activity. One cleavage in C3b does not affect its overall structure, whereas two cleavages unfold CUB and dislodge the thioester-containing domain (TED), affecting binding of regulators and thereby determining the number of cleavages. These data explain how FI generates late-stage opsonins iC3b or C3dg in a context-dependent manner, to react to foreign, danger or healthy self signals.

Regulators of complement activity mediate inhibitory mechanisms through a common C3b-binding mode.

Regulators of complement activation (RCA) inhibit complement-induced immune responses on healthy host tissues. We present crystal structures of human RCA (MCP, DAF, and CR1) and a smallpox virus homolog (SPICE) bound to complement component C3b. Our structural data reveal that up to four consecutive homologous CCP domains (i-iv), responsible for inhibition, bind in the same orientation and extended arrangement at a shared binding platform on C3b. Large sequence variations in CCP domains explain the diverse C3b-binding patterns, with limited or no contribution of some individual domains, while all regulators show extensive contacts with C3b for the domains at the third site. A variation of ~100° rotation around the longitudinal axis is observed for domains binding at the fourth site on C3b, without affecting the overall binding mode. The data suggest a common evolutionary origin for both inhibitory mechanisms, called decay acceleration and cofactor activity, with variable C3b binding through domains at sites ii, iii, and iv, and provide a framework for understanding RCA disease-related mutations and immune evasion.

Novel C3 mutation p.Lys65Gln in aHUS affects complement factor H binding.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) is associated with mutations affecting complement proteins and regulators and with autoantibodies against complement factor H (CFH). Approximately half of the aHUS patients progress to end-stage renal disease. DNA analysis of the risk factor genes is important for prognosis of aHUS recurrence after renal transplantation. METHODS: Mutational screening of C3 encoding the central complement component was performed by Sanger sequencing in 70 aHUS patients. Mutated and wild type recombinant C3b proteins were produced and their affinity to CFH was analyzed by ELISA. RESULTS: A single novel missense change p.Lys65Gln in C3 was found in 3 aHUS patients. The alteration leads to decreased binding of C3b to CFH in vitro. All three patients acquired the illness as adults and had a first aHUS episode after renal transplantation or suffered recurrence of the disease after transplantation. CONCLUSIONS: The novel C3 change was found in 3 aHUS patients. It results in decreased C3b binding to CFH and thus might lead to impaired C3b inactivation in vivo. The p.Lys65Gln is likely to be associated with aHUS after kidney transplantation and, therefore, might be an important prognostic factor.

Structural basis of chemokine sequestration by CrmD, a poxvirus-encoded tumor necrosis factor receptor.

Pathogens have evolved sophisticated mechanisms to evade detection and destruction by the host immune system. Large DNA viruses encode homologues of chemokines and their receptors, as well as chemokine-binding proteins (CKBPs) to modulate the chemokine network in host response. The SECRET domain (smallpox virus-encoded chemokine receptor) represents a new family of viral CKBPs that binds a subset of chemokines from different classes to inhibit their activities, either independently or fused with viral tumor necrosis factor receptors (vTNFRs). Here we present the crystal structures of the SECRET domain of vTNFR CrmD encoded by ectromelia virus and its complex with chemokine CX3CL1. The SECRET domain adopts a ß-sandwich fold and utilizes its ß-sheet I surface to interact with CX3CL1, representing a new chemokine-binding manner of viral CKBPs. Structure-based mutagenesis and biochemical analysis identified important basic residues in the 40s loop of CX3CL1 for the interaction. Mutation of corresponding acidic residues in the SECRET domain also affected the binding for other chemokines, indicating that the SECRET domain binds different chemokines in a similar manner. We further showed that heparin inhibited the binding of CX3CL1 by the SECRET domain and the SECRET domain inhibited RAW264.7 cell migration induced by CX3CL1. These results together shed light on the structural basis for the SECRET domain to inhibit chemokine activities by interfering with both chemokine-GAG and chemokine-receptor interactions.

Improvement of quality of life with Shenfu injection in non small cell lung cancer patients treated with gemcitabine plus cisplatin regimen.

OBJECTIVE: To observe the effect of Shenfu injection (SFI) in treating non small cell lung cancer (NSCLC) patients on quality of life with gemcitabine (GEM) plus cisplatin (GP) regimen. METHODS: Thirty-four patients were ready to receive GP regimen chemotherapy for treating NSCLC disease, according to lot-drawing, they were divided into SFI pre-treatment group (18 cases) and SFI post-treatment group (16 cases). SFI pre-treatment group: During the first treatment course, chemotherapy was begun with SFI 60 ml, intravenous dripping on the 3rd day, once daily, consecutively for 10 days; on the 1st day, GP regimen (GEM 1250 mg/m(2), intravenous dripping, on the 1st and 8th day; cisplatin 70 mg/m(2) on the 2nd day; 21 days as one cycle) was carried out; in the second treatment course GP regimen was merely given to serve as the self-control. SFI post-treatment group: the medicament sequence order was reversed from that of pre-treatment group. Using dual international quality of life (QOL) scores, the effect of SFI on the patients' QOL was observed through randomized self pre- and post-crossover control. RESULTS: The QOL in the 34 patients after being treated by SFI in combination with GP chemotherapy regimen in one group, and GP chemotherapy regimen alone in the other, was improved in different degrees, with significant difference (P < 0.01); comparison of SFI combined with GP chemotherapy regimen with GP chemotherapy alone showed that QOL in patients was significantly different (P < 0.01). CONCLUSION: SFI could improve QOL in patients with NSCLC who were treated with GP regimen.

[Preparation, characterization and application of monoclonal antibodies to Fc fragment of Ig fusion protein].

AIM: To prepare and characterize mAb to Fc fragment of Ig fusion protein, and to establish sandwich ELISA for detecting Ig fusion proteins and affinity chromatography method for Ig fusion protein purification. METHODS: hBCMA-Ig was used as antigen to immune BALB/c mice. The lymphocyte hybridoma technique was used to establish hybridoma cell lines stably secreting anti-Fc mAb. ELISA was employed to detect the isotype, epitopes, and species specificity of mAbs. Western blot was used to assess the reactivity between anti-Fc mAbs and denatured Ig fusion protein. LAIR1-Ig fusion protein was purified through affinity column anti-Fc mAb cross-linked to Sepharose 4B. RESULTS: Seven hybridoma cell lines(FMUFc1-FMUFc7) were acquired. A sandwich ELISA was successfully established using FMUFc4 as coating mAb and FMUFc5 as enzyme-labeled mAb. FMUFc6 could be used for Western blot. LAIR1-Ig fusion protein was effectively purified through FMUFc5-Sepharose affinity chromatography column. CONCLUSION: mAb against Fc fragment of Ig fusion protein has been prepared successfully, and methods to detect and purify Ig fusion protein are established. These mAbs provide useful tool for further application of Ig fusion protein.