Delineation of a PFOA Plume and Assessment of Data Gaps in its Conceptual Model Using PlumeSeeker™.

An accurate conceptual site model (CSM) and plume-delineation at contamination sites are pre-requisites for successful remediation and for satisfying regulators and stakeholders. PlumeSeeker™ is well-suited for assessing data gaps in CSMs by using available site data and for identifying the optimal number and locations of sampling locations to delineate contaminant plumes. It is an enhancement of a university research code for plume delineation using geostatistical and stochastic modeling integrated with the groundwater modeling software MODFLOW-SURFACT™. PlumeSeeker™ increases the overall confidence in the location of the plume boundary through a variance-reduction approach that selects existing- or new monitoring wells for sampling based on minimizing the uncertainty in plume boundary and on new field information. Applicable at sites with or without existing monitoring wells, PlumeSeeker™ is particularly powerful for optimally allocating project resources (labor, well installation, and laboratory costs) between existing wells and sampling at new locations. An application of PlumeSeeker™ at Lakehurst, the naval component of Joint Base McGuire-Dix-Lakehurst in New Jersey, demonstrates how the cost of delineating the migration pathway of a perfluorooctanoic acid (PFOA) plume can be minimized by requiring only 9 new sampling locations in addition to samples from 2 existing wells for achieving a 70% reduction in plume uncertainty. In addition, the use of available site data in three different scenarios identified CSM data-gaps in the source area and in the interaction between Manapaqua Branch and groundwater, where the observed high concentration in this area could have resulted from a combination of groundwater migration and induced infiltration.

NL-201 Upregulates MHC-I Expression and Intratumoral T-cell Receptor Diversity, and Demonstrates Robust Antitumor Activity as Monotherapy and in Combination with PD-1 Blockade.

Cytokine engineering has shown promise as a means to create novel immunomodulatory agents or to improve upon the therapeutic potential of natural cytokines. NL-201, a de novo, hyperstable, IL2 receptor alpha (IL2Rα)-independent agonist of the receptors for IL2 and IL15, elicits robust preclinical activity in syngeneic murine cancer models, including those resistant to immune checkpoint inhibitors (ICI). Here, we report that NL-201 monotherapy converts 'cold' tumor microenvironments (TME) to immunologically 'hot' states by driving pro-inflammatory gene expression, enhancing IFNγ-dependent MHC-I expression, and expanding both T-cell number and clonal diversity. In addition, the combination of NL-201 and anti-PD-1 resulted in complementary antitumor activity in the immunologically 'cold' and ICI resistant B16F10, EMT6, and Renca syngeneic models. In the B16F10 model, treatment with NL-201 plus anti-PD-1 increased the abundance of CD4+ and CD8+ effector T cells in the TME. These findings reveal an important mechanistic basis for the antitumor activity of NL-201 both as a monotherapy and in combination with PD-1 antagonists, and provide further context for the role of IL2Rα-based signaling in ICI-resistant tumors.

The networked micro-decision context: a new lens on transformative urban governance.

Recent large-scale societal disruptions, from the COVID-19 pandemic to intensifying wildfires and weather events, reveal the importance of transforming governance systems so they can address complex, transboundary, and rapidly evolving crises. Yet current knowledge of the decision-making dynamics that yield transformative governance remains scant. Studies typically focus on the aggregate outputs of government decisions, while overlooking their micro-level underpinnings. This is a key oversight because drivers of policy change, such as learning or competition, are prosecuted by people rather than organizations. We respond to this knowledge gap by introducing a new analytical lens for understanding policymaking, aimed at uncovering how characteristics of decision-makers and the structure of their relationships affect their likelihood of effectuating transformative policy responses. This perspective emphasizes the need for a more dynamic and relational view on urban governance in the context of transformation.

Enzyme Nanoscale Interactions with Manganese Zinc Sulfide Give Insight into Potential Antiviral Mechanisms and SARS-CoV-2 Inhibition.

Recent interest in nanomedicine has skyrocketed because of mRNA vaccine lipid nanoparticles (LNPs) against COVID-19. Ironically, despite this success, the innovative nexus between nanotechnology and biochemistry, and the impact of nanoparticles on enzyme biochemical activity is poorly understood. The studies of this group on zinc nanoparticle (ZNP) compositions suggest that nanorod morphologies are preferred and that ZNP doped with manganese or iron can increase activity against model enzymes such as luciferase, DNA polymerase, and ß-galactosidase (ß-Gal), with the latter previously being associated with antimicrobial activity. SARS-CoV-2 encodes several of these types of oxido-reductase, polymerase, or hydrolase types of enzymes, and while metamaterials or nanoparticle composites have become important in many fields, their application against SARS-CoV-2 has only recently been considered. Recently, this group discovered the antiviral activity of manganese-doped zinc sulfide (MnZnS), and here the interactions of this nanoparticle composite with ß-Gal, angiotensin converting enzyme (ACE), and human ACE2 (hACE2), the SARS-CoV-2 receptor, are demonstrated. Low UV, circular dichroism, and zeta potential results confirm their enzyme interaction and inhibition by fluorometric area under the curve (AUC) measurements. The IC50 of enzyme activity varied depending on the manganese percentage and surface ranging from 20 to 50 µg/mL. MnZnS NPs give a 1-2 log order inhibition of SARS-CoV-2; however, surface-capping with cysteine does not improve activity. These data suggest that Mn substituted ZNP interactions to hACE2 and potentially other enzymes may underlie its antiviral activity, opening up a new area of pharmacology ready for preclinical translation.

The engineered CD80 variant fusion therapeutic davoceticept combines checkpoint antagonism with conditional CD28 costimulation for anti-tumor immunity.

Despite the recent clinical success of T cell checkpoint inhibition targeting the CTLA-4 and PD-1 pathways, many patients either fail to achieve objective responses or they develop resistance to therapy. In some cases, poor responses to checkpoint blockade have been linked to suboptimal CD28 costimulation and the inability to generate and maintain a productive adaptive anti-tumor immune response. To address this, here we utilize directed evolution to engineer a CD80 IgV domain with increased PD-L1 affinity and fuse this to an immunoglobulin Fc domain, creating a therapeutic (ALPN-202, davoceticept) capable of providing CD28 costimulation in a PD-L1-dependent fashion while also antagonizing PD-1 - PD-L1 and CTLA-4-CD80/CD86 interactions. We demonstrate that by combining CD28 costimulation and dual checkpoint inhibition, ALPN-202 enhances T cell activation and anti-tumor efficacy in cell-based assays and mouse tumor models more potently than checkpoint blockade alone and thus has the potential to generate potent, clinically meaningful anti-tumor immunity in humans.

Zn-based physiometacomposite nanoparticles: distribution, tolerance, imaging, and antiviral and anticancer activity.

The aim of this study was to investigate the distribution, tolerance, and anticancer and antiviral activity of Zn-based physiometacomposites (PMCs). Manganese, iron, nickel and cobalt-doped ZnO, ZnS or ZnSe were synthesized. Cell uptake, distribution into 3D culture and mice, and biochemical and chemotherapeutic activity were studied by fluorescence/bioluminescence, confocal microscopy, flow cytometry, viability, antitumor and virus titer assays. Luminescence and inductively coupled plasma mass spectrometry analysis showed that nanoparticle distribution was liver >spleen >kidney >lung >brain, without tissue or blood pathology. Photophysical characterization as ex vivo tissue probes and LL37 peptide, antisense oligomer or aptamer delivery targeting RAS/Ras binding domain (RBD) was investigated. Treatment at 25 µg/ml for 48 h showed ≥98-99% cell viability, 3D organoid uptake, 3-log inhibition of ß-Galactosidase and porcine reproductive respiratory virus infection. Data support the preclinical development of PMCs for imaging and delivery targeting cancer and infectious disease.

VipariNama: RNA viral vectors to rapidly elucidate the relationship between gene expression and phenotype.

Synthetic transcription factors have great promise as tools to help elucidate relationships between gene expression and phenotype by allowing tunable alterations of gene expression without genomic alterations of the loci being studied. However, the years-long timescales, high cost, and technical skill associated with plant transformation have limited their use. In this work, we developed a technology called VipariNama (ViN) in which vectors based on the tobacco rattle virus are used to rapidly deploy Cas9-based synthetic transcription factors and reprogram gene expression in planta. We demonstrate that ViN vectors can implement activation or repression of multiple genes systemically and persistently over several weeks in Nicotiana benthamiana, Arabidopsis (Arabidopsis thaliana), and tomato (Solanum lycopersicum). By exploring strategies including RNA scaffolding, viral vector ensembles, and viral engineering, we describe how the flexibility and efficacy of regulation can be improved. We also show how this transcriptional reprogramming can create predictable changes to metabolic phenotypes, such as gibberellin biosynthesis in N. benthamiana and anthocyanin accumulation in Arabidopsis, as well as developmental phenotypes, such as plant size in N. benthamiana, Arabidopsis, and tomato. These results demonstrate how ViN vector-based reprogramming of different aspects of gibberellin signaling can be used to engineer plant size in a range of plant species in a matter of weeks. In summary, ViN accelerates the timeline for generating phenotypes from over a year to just a few weeks, providing an attractive alternative to transgenesis for synthetic transcription factor-enabled hypothesis testing and crop engineering.

Annual regulation of adrenocortical function in migrant and resident subspecies of white-crowned sparrow.

Corticosterone affects physiology and behavior both during normal daily processes but also in response to environmental challenges and is known to mediate life history trade-offs. Many studies have investigated patterns of corticosterone production at targeted times of year, while ignoring underlying annual profiles. We aimed to understand the annual regulation of hypothalamic-pituitary-adrenal (HPA) axis function of both migrant (Zonotrichia leucophrys gambelii; n = 926) and resident (Z. l. nutalli; n = 688) subspecies of white-crowned sparrow and how it is influenced by environmental conditions - wind, precipitation, and temperature. We predicted that more dramatic seasonal changes in baseline and stress-induced corticosterone would occur in migrants to precisely time the onset of breeding and cope with environmental extremes on their arctic breeding grounds, while changes in residents would be muted as they experience a more forgiving breeding schedule and comparatively benign environmental conditions in coastal California. During the course of a year, the harshest conditions were experienced the summer breeding grounds for migrants, at which point they had higher corticosterone levels compared to residents. For residents, the winter months coincided with harshest conditions at which point they had higher corticosterone levels than migrants. For both subspecies, corticosterone tended to rise as environmental conditions became colder and windier. We found that the annual maxima in stress-induced corticosterone occurred prior to egg lay for all birds except resident females. Migrants had much higher baseline and acute stress-induced corticosterone during breeding compared to residents; where in a harsher environment the timing of the onset of reproduction is more critical because the breeding season is shorter. Interestingly, molt was the only stage within the annual cycle in which subspecies differences were absent suggesting that a requisite reduction in corticosterone may have to be met for feather growth. These data suggest that modulation of the HPA axis is largely driven by environmental factors, social cues, and their potential interactions with a genetic program.

De novo design of potent and resilient hACE2 decoys to neutralize SARS-CoV-2.

We developed a de novo protein design strategy to swiftly engineer decoys for neutralizing pathogens that exploit extracellular host proteins to infect the cell. Our pipeline allowed the design, validation, and optimization of de novo human angiotensin-converting enzyme 2 (hACE2) decoys to neutralize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The best monovalent decoy, CTC-445.2, bound with low nanomolar affinity and high specificity to the receptor-binding domain (RBD) of the spike protein. Cryo-electron microscopy (cryo-EM) showed that the design is accurate and can simultaneously bind to all three RBDs of a single spike protein. Because the decoy replicates the spike protein target interface in hACE2, it is intrinsically resilient to viral mutational escape. A bivalent decoy, CTC-445.2d, showed ~10-fold improvement in binding. CTC-445.2d potently neutralized SARS-CoV-2 infection of cells in vitro, and a single intranasal prophylactic dose of decoy protected Syrian hamsters from a subsequent lethal SARS-CoV-2 challenge.

ICOSL+ plasmacytoid dendritic cells as inducer of graft-versus-host disease, responsive to a dual ICOS/CD28 antagonist.

Acute graft-versus-host disease (aGVHD) remains a major complication of allogeneic hematopoietic cell transplantation (HCT). CD146 and CCR5 are proteins that mark activated T helper 17 (Th17) cells. The Th17 cell phenotype is promoted by the interaction of the receptor ICOS on T cells with ICOS ligand (ICOSL) on dendritic cells (DCs). We performed multiparametric flow cytometry in a cohort of 156 HCT recipients and conducted experiments with aGVHD murine models to understand the role of ICOSL+ DCs. We observed an increased frequency of ICOSL+ plasmacytoid DCs, correlating with CD146+CCR5+ T cell frequencies, in the 64 HCT recipients with gastrointestinal aGVHD. In murine models, donor bone marrow cells from ICOSL-deficient mice compared to those from wild-type mice reduced aGVHD-related mortality. Reduced aGVHD resulted from lower intestinal infiltration of pDCs and pathogenic Th17 cells. We transplanted activated human ICOSL+ pDCs along with human peripheral blood mononuclear cells into immunocompromised mice and observed infiltration of intestinal CD146+CCR5+ T cells. We found that prophylactic administration of a dual human ICOS/CD28 antagonist (ALPN-101) prevented aGVHD in this model better than did the clinically approved belatacept (CTLA-4-Fc), which binds CD80 (B7-1) and CD86 (B7-2) and interferes with the CD28 T cell costimulatory pathway. When started at onset of aGVHD signs, ALPN-101 treatment alleviated symptoms of ongoing aGVHD and improved survival while preserving antitumoral cytotoxicity. Our data identified ICOSL+-pDCs as an aGVHD biomarker and suggest that coinhibition of the ICOSL/ICOS and B7/CD28 axes with one biologic drug may represent a therapeutic opportunity to prevent or treat aGVHD.

De novo design of ACE2 protein decoys to neutralize SARS-CoV-2.

There is an urgent need for the ability to rapidly develop effective countermeasures for emerging biological threats, such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes the ongoing coronavirus disease 2019 (COVID-19) pandemic. We have developed a generalized computational design strategy to rapidly engineer de novo proteins that precisely recapitulate the protein surface targeted by biological agents, like viruses, to gain entry into cells. The designed proteins act as decoys that block cellular entry and aim to be resilient to viral mutational escape. Using our novel platform, in less than ten weeks, we engineered, validated, and optimized de novo protein decoys of human angiotensin-converting enzyme 2 (hACE2), the membrane-associated protein that SARS-CoV-2 exploits to infect cells. Our optimized designs are hyperstable de novo proteins (∼18-37 kDa), have high affinity for the SARS-CoV-2 receptor binding domain (RBD) and can potently inhibit the virus infection and replication in vitro. Future refinements to our strategy can enable the rapid development of other therapeutic de novo protein decoys, not limited to neutralizing viruses, but to combat any agent that explicitly interacts with cell surface proteins to cause disease.

Building customizable auto-luminescent luciferase-based reporters in plants.

Bioluminescence is a powerful biological signal that scientists have repurposed as a reporter for gene expression in plants and animals. However, there are downsides associated with the need to provide a substrate to these reporters, including its high cost and non-uniform tissue penetration. In this work we reconstitute a fungal bioluminescence pathway (FBP) in planta using a composable toolbox of parts. We demonstrate that the FBP can create luminescence across various tissues in a broad range of plants without external substrate addition. We also show how our toolbox can be used to deploy the FBP in planta to build auto-luminescent reporters for the study of gene-expression and hormone fluxes. A low-cost imaging platform for gene expression profiling is also described. These experiments lay the groundwork for future construction of programmable auto-luminescent plant traits, such as light driven plant-pollinator interactions or light emitting plant-based sensors.

Many animals have evolved the capacity to produce light from chemical reactions. For example, an enzyme known as luciferase in fireflies produces light by acting on a molecule called luciferin. Scientists have identified the enzymes that drive several of these systems and used them to build reporters that can study the activity of genes in the tissues of plants and other lifeforms over space and time. However, these reporters often require chemicals to be added to the tissues to produce light. These chemicals tend to be expensive and may not penetrate evenly into the tissues of interest, limiting the potential applications of the reporters in research studies. Recently, it has been discovered that fungi have a bioluminescence pathway that converts a molecule known as caffeic acid into luciferin. Caffeic acid is a common molecule in plants, therefore, it is possible the fungal bioluminescence pathway could be used to build reporters that produce light without needing the addition of chemicals. Now, Khakhar et al. have inserted the genes that encode the enzymes of the fungal bioluminescence pathway into tobacco plants. The experiments found that this was sufficient to turn caffeic acid into molecules of luciferin which are able to produce light. Inserting the same genes into several other plant species, including tomatoes and dahlias, produced similar results. Further experiments showed that the fungal bioluminescence pathway can be used to build reporters that monitor the activity of plant genes throughout living tissues and over a period of several days as well as examine the response to plant hormones. Alongside studying the activities of genes in plants, Khakhar et al. propose that the toolkit developed in this work could be used to generate plants with luminescence that can be switched on or off as desired. This could have many uses including helping plants attract insects to pollinate flowers and building plant biosensors that emit light in response to environmental signals.

Tissue-specific expression of 11ß-HSD and its effects on plasma corticosterone during the stress response.

The hypothalamic-pituitary-adrenal (HPA) axis is under complex regulatory control at multiple levels. Enzymatic regulation plays an important role in both circulating levels of glucocorticoids and target tissue exposure. Three key enzyme pathways are responsible for the immediate control of glucocorticoids. De novo synthesis of glucocorticoid from cholesterol involves a multistep enzymatic cascade. This cascade terminates with 11ß-hydroxylase, responsible for the final conversion of 11-deoxy precursors into active glucocorticoids. Additionally, 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) controls regeneration of glucocorticoids from inactive metabolites, providing a secondary source of active glucocorticoids. Localized inactivation of glucocorticoids is under the control of Type 2 11ß-HSD (11ß-HSD2). The function of these enzymes is largely unexplored in wild species, particularly songbirds. Here, we investigated the contribution of both clearance and generation of glucocorticoids to regulation of the hormonal stress response via the use of pharmacological antagonists. Additionally, we mapped 11ß-HSD gene expression. We found 11ß-HSD1 primarily in liver, kidney and adrenal glands, although it was detectable across all tissue types. 11ß-HSD2 was predominately expressed in the adrenal glands and kidney with moderate gonadal and liver expression. Inhibition of glucocorticoid generation by metyrapone was found to decrease levels peripherally, while both peripheral and central administration of the 11ß-HSD2 inhibitor DETC resulted in elevated concentrations of corticosterone. These data suggest that during the stress response, peripheral antagonism of the 11ß-HSD system has a greater impact on circulating glucocorticoid levels than central control. Further studies should aim to elucidate the respective roles of the 11ß-HSD and 11ß-hydroxylase enzymes.

Overexpression of T-bet in HIV infection is associated with accumulation of B cells outside germinal centers and poor affinity maturation.

Nearly all chronic human infections are associated with alterations in the memory B cell (MBC) compartment, including a large expansion of CD19hiT-bethi MBC in the peripheral blood of HIV-infected individuals with chronic viremia. Despite their prevalence, it is unclear how these B cells arise and whether they contribute to the inefficiency of antibody-mediated immunity in chronic infectious diseases. We addressed these questions by characterizing T-bet-expressing B cells in lymph nodes (LN) and identifying a strong T-bet signature among HIV-specific MBC associated with poor immunologic outcome. Confocal microscopy and quantitative imaging revealed that T-bethi B cells in LN of HIV-infected chronically viremic individuals distinctly accumulated outside germinal centers (GC), which are critical for optimal antibody responses. In single-cell analyses, LN T-bethi B cells of HIV-infected individuals were almost exclusively found among CD19hi MBC and expressed reduced GC-homing receptors. Furthermore, HIV-specific B cells of infected individuals were enriched among LN CD19hiT-bethi MBC and displayed a distinct transcriptome, with features similar to CD19hiT-bethi MBC in blood and LN GC B cells (GCBC). LN CD19hiT-bethi MBC were also related to GCBC by B cell receptor (BCR)-based phylogenetic linkage but had lower BCR mutation frequencies and reduced HIV-neutralizing capacity, consistent with diminished participation in GC-mediated affinity selection. Thus, in the setting of chronic immune activation associated with HIV viremia, failure of HIV-specific B cells to enter or remain in GC may help explain the rarity of high-affinity protective antibodies.

Novel Immunomodulatory Proteins Generated via Directed Evolution of Variant IgSF Domains.

Immunoglobulin superfamily member (IgSF) proteins play a significant role in regulating immune responses with surface expression on all immune cell subsets, making the IgSF an attractive family of proteins for therapeutic targeting in human diseases. We have developed a directed evolution platform capable of engineering IgSF domains to increase affinities for cognate ligands and/or introduce binding to non-cognate ligands. Using this scientific platform, ICOSL domains have been derived with enhanced binding to ICOS and with additional high-affinity binding to the non-cognate receptor, CD28. Fc-fusion proteins containing these engineered ICOSL domains significantly attenuate T cell activation in vitro and in vivo and can inhibit development of inflammatory diseases in mouse models. We also present evidence that engineered ICOSL domains can be formatted to selectively provide costimulatory signals to augment T cell responses. Our scientific platform thus provides a system for developing therapeutic protein candidates with selective biological impact for treatments of a wide array of human disorders including cancer and autoimmune/inflammatory diseases.

Evaluation of chromatofocusing as a capture method for monoclonal antibody products.

Chromatofocusing is investigated as an alternative to protein A chromatography for the initial capture step in a purification process for several monoclonal antibodies and antibody fusion products. For comparison, this work also investigates the use of ion-exchange chromatography with either pH or salt gradient elution as additional alternatives to protein A chromatography. The specific conditions employed for the capture step for the case of chromatofocusing were selected on a rational basis using a computer-aided design method implemented in the form of a Microsoft Excel spreadsheet. Alternative operating conditions were compared experimentally with regard to the product yield achieved as well as the removal of total host cell proteins (HCPs) and of a specific HCP major component. Results from this study indicate that both chromatofocusing and ion-exchange chromatography are useful alternatives to a protein A chromatography capture step in many practical cases. This is especially true for the case of chromatofocusing when it is possible to exploit the ability of the method to create complex gradient shapes that are self-forming inside the column and to simultaneous focus and separate proteins inside the column.

Accounting for host cell protein behavior in anion-exchange chromatography.

Host cell proteins (HCP) are a problematic set of impurities in downstream processing (DSP) as they behave most similarly to the target protein during separation. Approaching DSP with the knowledge of HCP separation behavior would be beneficial for the production of high purity recombinant biologics. Therefore, this work was aimed at characterizing the separation behavior of complex mixtures of HCP during a commonly used method: anion-exchange chromatography (AEX). An additional goal was to evaluate the performance of a statistical methodology, based on the characterization data, as a tool for predicting protein separation behavior. Aqueous two-phase partitioning followed by two-dimensional electrophoresis provided data on the three physicochemical properties most commonly exploited during DSP for each HCP: pI (isoelectric point), molecular weight, and surface hydrophobicity. The protein separation behaviors of two alternative expression host extracts (corn germ and E. coli) were characterized. A multivariate random forest (MVRF) statistical methodology was then applied to the database of characterized proteins creating a tool for predicting the AEX behavior of a mixture of proteins. The accuracy of the MVRF method was determined by calculating a root mean squared error value for each database. This measure never exceeded a value of 0.045 (fraction of protein populating each of the multiple separation fractions) for AEX. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1453-1463, 2016.

Molecular perspective of antibody aggregates and their adsorption on Protein A resin.

Antibody aggregate is a common issue in therapeutic antibodies, which may compromise product efficacy and cause adverse effects. Antibody aggregate level is normally controlled in bioprocessing by polishing steps after Protein A capture. This paper studied the Higher Order Structures (HOS) of antibody aggregates (dimer H1 and H2) and their adsorption on Protein A resin and thus elucidated the mechanism using Protein A capture for enhanced aggregate removal. The HOS of antibody aggregates and their complex with Protein A were characterized using HDX-MS combined with SEC-MALS, Protein Conformational Array (PCA), and molecular modeling. The aggregate size and Protein A binding ratio suggested that H2 has much more compact structure than H1. HDX-MS and PCA further revealed that H1 was formed by single Fab-Fab interaction while H2 formed by Fab-Fab and likely Fc-Fc interaction. On Protein A resin, both the molar binding ratio and the correlation between protein size and ligand distance support that each monomer can only bind one Protein A ligand, while each dimer can bind two ligands, thus resulting in stronger resin binding. Furthermore, dimer H2 binds stronger than dimer H1 due to its compact structure. By integrating biophysical analysis and molecular modeling with process development, this study revealed the antibody aggregate structures and the mechanism of aggregate removal using Protein A chromatography. It also provided a general strategy for in-depth product and process understanding in antibody and other biologics development.