Protein G, protein A and protein A-derived peptides inhibit the agitation induced aggregation of IgG

Performance study of a sterilization box using a combination of heat and ultraviolet light irradiation for the prevention of COVID-19

SARS-CoV-2 virus and other pathogenic microbes are transmitted to the environment through contacting surfaces, which need to be sterilized for the prevention of COVID-19 and related diseases. In this study, a prototype of a cost-effective sterilization box is developed to disinfect small items. The box utilizes ultra violet (UV) radiation with heat. For performance assessment, two studies were performed. First, IgG (glycoprotein, a model protein similar to that of spike glycoprotein of SARS-COV-2) was incubated under UV and heat sterilization. An incubation with UV at 70 °C for 15 min was found to be effective in unfolding and aggregation of the protein. At optimized condition, the hydrodynamic size of the protein increased to ~171 nm from ~5 nm of the native protein. Similarly, the OD₂₈₀ values also increased from 0.17 to 0.78 indicating the exposure of more aromatic moieties and unfolding of the protein. The unfolding and aggregation of the protein were further confirmed by the intrinsic fluorescence measurement and FTIR studies, showing a 70% increase in the β-sheets and a 22% decrease in the α-helixes of the protein. The designed box was effective in damaging the protein's native structure indicating the effective inactivation of the SARS-COV-2. Furthermore, the incubation at 70 °C for 15 min inside the chamber resulted in 100% antibacterial efficacy for the clinically relevant E.coli bacteria as well as for bacteria collected from daily use items. It is the first detailed performance study on the efficacy of using UV irradiation and heat together for disinfection from virus and bacteria.

Site-Specific Conjugation of Metal-Chelating Polymers to Anti-Frizzled-2 Antibodies via Microbial Transglutaminase

Metal-chelating polymer-based radioimmunoconjugates (RICs) are effective agents for radioimmunotherapy but are currently limited by nonspecific binding and off-target organ uptake. Nonspecific binding appears after conjugation of the polymer to the antibody and may be related to random lysine conjugation since the polymers themselves do not bind to cells. To investigate the role of conjugation sites on nonspecific binding of polymer RICs, we developed a microbial transglutaminase reaction to prepare site-specific antibody-polymer conjugates. The reaction was enabled by introducing a Q-tag (i.e., 7M48) into antibody (i.e., Fab) fragments and synthesizing a polyglutamide-based metal-chelating polymer with a PEG amine block to yield substrates. Mass spectrometric analyses confirmed that the microbial transglutaminase conjugation reaction was site-specific. For comparison, random lysine conjugation analogs with an average of one polymer per Fab were prepared by bis-aryl hydrazone conjugation. Conjugates were prepared from an anti-frizzled-2 Fab to target the Wnt pathway, along with a nonbinding specificity control, anti-Luciferase Fab. Fabs were engineered from a trastuzumab-based IgG1 framework and lack lysines in the antigen-binding site. Conjugates were analyzed for thermal conformational stability by differential scanning fluorimetry, which showed that the site-specific conjugate had a similar melting temperature to the parent Fab. Binding assays by biolayer interferometry showed that the site-specific anti-frizzled-2 conjugate maintained high affinity to the antigen, while the random conjugate showed a 10-fold decrease in affinity, which was largely due to changes in association rates. Radioligand cell-binding assays on frizzled-2+ PANC-1 cells and frizzled-2- CHO cells showed that the site-specific anti-frizzled-2 conjugate had ca. 4-fold lower nonspecific binding compared to the random conjugate. Site-specific conjugation appeared to reduce nonspecific binding associated with random conjugation of the polymer in polymer RICs.

Protein A does not induce allosteric structural changes in an IgG1 antibody during binding

Affinity chromatography is widely used for antibody purification in biopharmaceutical production. Although there is evidence suggesting that affinity chromatography might induce structural changes in antibodies, allosteric changes in structure have not been well-explored. Here, we used hydrogen exchange-mass spectrometry (HX-MS) to reveal conformational changes in the NIST mAb upon binding with a protein A (ProA) matrix. HX-MS measurements of NIST mAb bound to in-solution and resin forms of ProA revealed regions of the C_H2 and C_H3 domains with increased protection from HX upon ProA binding, consistent with the known ProA binding region. In-solution ProA experiments revealed regions in the F_ab with increased HX uptake when the ProA:mAb molar ratio was increased to 2:1, suggesting an allosterically induced increase in backbone flexibility. Such effects were not observed with lower ProA concentration (1:1 molar ratio) or when ProA resin was used, suggesting some kind of change in binding mode. Since all pharmaceutical processes use ProA bound to resin, our results rule out reversible allosteric effects on the NIST mAb during interaction with resin ProA. However, irreversible effects cannot be ruled out since the NIST mAb was previously exposed to ProA during its original purification.

Antibody-mediated soluble CD14 stabilization prevents agitation-induced increases in presepsin levels in blood component specimens

Presepsin is a 13-kDa N-terminal glycoprotein of CD14. Previously, agitation-induced increases in presepsin levels have been reported; however, the mechanism remains poorly understood. In this study, we aimed to reveal the mechanism of presepsin increase. The agitated plasma or serum was separated using gel exclusion chromatography and analyzed by ELISA. The effect of an anti-CD14 antibody (F1024-1-3) was examined. We observed elevated presepsin levels in the agitated plasma and aggregated soluble CD14 (sCD14). However, treatment with F1024-1-3 before agitation prevented the aggregation and the increase in presepsin levels. Depletion of aggregated sCD14 decreased the presepsin levels. Our findings indicate that agitation induces the aggregation of sCD14 and triggers an increase in presepsin. Anti-CD14 antibody prevents an increases in presepsin.

M. Brito R. Structure and Aggregation Mechanisms in Amyloids

The aggregation of a polypeptide chain into amyloid fibrils and their accumulation and deposition into insoluble plaques and intracellular inclusions is the hallmark of several misfolding diseases known as amyloidoses. Alzheimer′s, Parkinson′s and Huntington’s diseases are some of the approximately 50 amyloid diseases described to date. The identification and characterization of the molecular species critical for amyloid formation and disease development have been the focus of intense scrutiny. Methods such as X-ray and electron diffraction, solid-state nuclear magnetic resonance spectroscopy (ssNMR) and cryo-electron microscopy (cryo-EM) have been extensively used and they have contributed to shed a new light onto the structure of amyloid, revealing a multiplicity of polymorphic structures that generally fit the cross-β amyloid motif. The development of rational therapeutic approaches against these debilitating and increasingly frequent misfolding diseases requires a thorough understanding of the molecular mechanisms underlying the amyloid cascade. Here, we review the current knowledge on amyloid fibril formation for several proteins and peptides from a kinetic and thermodynamic point of view, the structure of the molecular species involved in the amyloidogenic process, and the origin of their cytotoxicity.

Characterization of a Novel Bispecific Antibody With Improved Conformational and Chemical Stability

Bispecific antibodies containing single-chain variable fragment (scFv) appended to immunoglobulins G offer unique development challenges. Here, we describe the stability of a novel bispecific format, BiS5, where the scFv is tethered to the C_H3 domain. BiS5 showed an improved conformational and chemical stability compared with that of BiS4 in which the scFv is appended in the hinge region between the F_ab and F_c. By switching the location of the scFv from hinge region to the C_H3, there was an improved stabilization of C_H2 and scFv domains. Interestingly, no noticeable impact was observed on the conformational stability of C_H3 and F_ab domains. BiS4 and BiS5 showed different aggregation and fragmentation rates under accelerated temperature stress conditions. BiS4 showed higher fragmentation rates compared with BiS5 likely owing to fragmentation in the linker region on either side of the scFv while BiS5 is more resistant toward fragmentation owing to tethering of scFv to the C_H3 domain at its N and C terminus. In conclusion, the location of scFv affects both aggregation and fragmentation kinetics. These insights into the molecular structure and correlations with their physical and chemical stability will help formulation development of these novel bispecific antibodies.

Predictive approach for protein aggregation: Correlation of protein surface characteristics and conformational flexibility to protein aggregation propensity

The aggregation of proteins became one of the major challenges in the development of biopharmaceu-ticals since the formation of aggregates can affect drug quality and immunogenicity. However, aggregation mechanisms are highly complex and the investigation requires cost, time, and material intensive experi-mental effort. In the present work, the predictive power of protein characteristics for the phase behavior of three different proteins which are very similar in size and structure was studied. In particular, the surface hydrophobicity, zeta potential, and conformational flexibility of human lysozyme, lysozyme from chicken egg white, and α-lactalbumin at pH 3, 5, 7, and 9 were assessed and examined for correlation with experimental stability studies focusing on protein phase behavior induced by sodium chloride and ammonium sulfate. The molecular dynamics (MD) simulation based study of the conformational flexibility without precipitants was able to identify highly flexible protein regions which could be associated to the less regular secondary structure elements and random coiled and terminal regions in particular. Conformational flex-ibility of the entire protein structure and protein surface hydrophobicity could be correlated to differing aggregation propensities among the studied proteins and could be identified to be applicable for predic-tion of protein phase behavior in aqueous solution without precipitants. For prediction of protein phase behavior and aggregation propensity in aqueous solution with precipitants, protein flexibility was further studied in dependency of salt concentration and species by means of human lysozyme. Even though the results of the salt dependent MD simulations could not be shown to be sufficient for prediction of salt depending phase behavior, this study revealed a more pronounced destabilizing effect of ammonium sulfate in comparison to sodium chloride and thus, was found to be in good agreement with theoretical considerations along the Hofmeister series as well as experimentally evaluated phase behavior. Biotechnol. Bioeng. 2017;114: 1170-1183. © 2016 Wiley Periodicals, Inc.

Physical Characterization and Innate Immunogenicity of Aggregated Intravenous Immunoglobulin (IGIV) in an In Vitro Cell-Based Model

PURPOSE

To investigate in vitro the innate immune response to accelerated stress-induced aggregates of intravenous immunoglobulin (IGIV) using a well-defined human cell-line model, and to correlate the innate response to physical properties of the aggregates.

METHODS

IGIV aggregates were prepared by applying various accelerated stress methods, and particle size, count and structure were characterized. Immune cell activation as tracked by inflammatory cytokines released in response to aggregates was evaluated in vitro using peripheral blood mononuclear cells (PBMC), primary monocytes and immortalized human monocyte-like cell lines.

RESULTS

IGIV aggregates produced by mechanical stress induced higher cytokine release by PBMC and primary monocytes than aggregates formed by other stresses. Results with the monocytic cell line THP-1 paralleled trends in PBMC and primary monocytes. Effects were dose-dependent, enhanced by complement opsonization, and partially inhibited by blocking toll-like receptors (TLR2 and TLR4) and to a lesser extent by blocking Fc gamma receptors (FcγRs).

CONCLUSIONS

Stress-induced IGIV aggregates stimulate a dose-dependent cytokine response in human monocytes and THP-1 cells, mediated in part by TLRs, FcγRs and complement opsonization. THP-1 cells resemble primary monocytes in many respects with regard to tracking the innate response to IgG aggregates. Accordingly, the measurement of inflammatory cytokines released by THP-1 cells provides a readily accessible assay system to screen for the potential innate immunogenicity of IgG aggregates. The results also highlight the role of aggregate structure in interacting with the different receptors mediating innate immunity.

Structure based descriptors for the estimation of colloidal interactions and protein aggregation propensities

The control of protein aggregation is an important requirement in the development of bio-pharmaceutical formulations. Here a simple protein model is proposed that was used in molecular dynamics simulations to obtain a quantitative assessment of the relative contributions of proteins' net-charges, dipole-moments, and the size of hydrophobic or charged surface patches to their colloidal interactions. The results demonstrate that the strength of these interactions correlate with net-charge and dipole moment. Variation of both these descriptors within ranges typical for globular proteins have a comparable effect. By comparison no clear trends can be observed upon varying the size of hydrophobic or charged patches while keeping the other parameters constant. The results are discussed in the context of experimental literature data on protein aggregation. They provide a clear guide line for the development of improved algorithms for the prediction of aggregation propensities.