Biological activity of human-mouse IgG1, IgG2, IgG3, and IgG4 chimeric monoclonal antibodies with antitumor specificity

Protective Non-neutralizing anti-N-terminal Domain mAb Maintains Fc-mediated Function against SARS-COV-2 Variants up to BA.2.86-JN.1 with Superfluous In Vivo Protection against JN.1 Due to Attenuated Virulence

Substantial evidence supports that Fc-mediated effector functions of anti-spike Abs contribute to anti-SARS-Cov-2 protection. We have previously shown that two non-neutralizing but opsonic mAbs targeting the receptor-binding domain and N-terminal domain (NTD), Ab81 and Ab94, respectively, are protective against lethal Wuhan SARS-CoV-2 infection in K18-hACE2 mice. In this article, we investigated whether these protective non-neutralizing Abs maintain Fc-mediated function and Ag binding against mutated SARS-CoV-2 variants. Ab81 and Ab94 retained their nanomolar affinity and Fc-mediated function toward Omicron and its subvariants, such as BA.2, BA.4, BA.5, XBB, XBB1.5, and BQ1.1. However, when encountering the more heavily mutated BA.2.86, Ab81 lost its function, whereas the 10 new mutations in the NTD did not affect Ab94. In vivo experiments with Ab94 in K18-hACE2 mice inoculated with a stringent dose of 100,000 PFU of the JN.1 variant revealed unexpected results. Surprisingly, this variant exhibited low disease manifestation in this animal model with no weight loss or death in the control group. Still, assessment of mice using a clinical scoring system showed better protection for Ab94-treated mice, indicating that Fc-mediated functions are still beneficial. Our work shows that a protective anti-receptor-binding domain non-neutralizing mAb lost reactivity when BA.2.86 emerged, whereas the anti-NTD mAb was still functional. Finally, this work adds new insight into the evolution of the SARS-CoV-2 virus by reporting that JN.1 is substantially less virulent in vivo than previous strains.

Living in LALA land? Forty years of attenuating Fc effector functions

The Fc region of antibodies is vital for most of their physiological functions, many of which are engaged through binding to a range of Fc receptors. However, these same interactions are not always helpful or wanted when therapeutic antibodies are directed against self-antigens, and can sometimes cause catastrophic adverse reactions. Over the past 40 years, there have been intensive efforts to "silence" unwanted binding to Fc-gamma receptors, resulting in at least 45 different variants which have entered clinical trials. One of the best known is "LALA" (L234A/L235A). However, neither this, nor most of the other variants in clinical use are completely silenced, and in addition, the biophysical properties of many of them are compromised. I review the development of different variants to see what we can learn from their biological properties and use in the clinic. With the rise of powerful new uses of antibody therapy such as bispecific T-cell engagers, antibody-drug conjugates, and checkpoint inhibitors, it is increasingly important to optimize the Fc region as well as the antibody binding site in order to achieve the best combination of safety and efficacy.

Antitumor activity of Z15-0-2, a bispecific nanobody targeting PD-1 and CTLA-4

The combination of programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA-4) antibodies has potential for enhancing clinical efficacy. We described the development and antitumor activity of Z15-0, a bispecific nanobody targeting both the PD-1 and CTLA-4 pathways simultaneously. We designed and optimized the mRNA sequence encoding Z15-0, referred to as Z15-0-2 and through a series of in vitro and in vivo experiments, we established that the optimized Z15-0-2 mRNA sequence significantly increased the expression of the bispecific nanobody. Administration of Z15-0-2 mRNA to tumor-bearing mice led to greater inhibition of tumor growth compared to controls. In aggregate, we introduced a novel bispecific nanobody and have re-engineered it to boost expression of mRNA, representing a new drug development paradigm.

The hinge-engineered IgG1-IgG3 hybrid subclass IgGh47 potently enhances Fc-mediated function of anti-streptococcal and SARS-CoV-2 antibodies

Streptococcus pyogenes can cause invasive disease with high mortality despite adequate antibiotic treatments. To address this unmet need, we have previously generated an opsonic IgG1 monoclonal antibody, Ab25, targeting the bacterial M protein. Here, we engineer the IgG2-4 subclasses of Ab25. Despite having reduced binding, the IgG3 version promotes stronger phagocytosis of bacteria. Using atomic simulations, we show that IgG3's Fc tail has extensive movement in 3D space due to its extended hinge region, possibly facilitating interactions with immune cells. We replaced the hinge of IgG1 with four different IgG3-hinge segment subclasses, IgGhxx. Hinge-engineering does not diminish binding as with IgG3 but enhances opsonic function, where a 47 amino acid hinge is comparable to IgG3 in function. IgGh47 shows improved protection against S. pyogenes in a systemic infection mouse model, suggesting that IgGh47 has promise as a preclinical therapeutic candidate. Importantly, the enhanced opsonic function of IgGh47 is generalizable to diverse S. pyogenes strains from clinical isolates. We generated IgGh47 versions of anti-SARS-CoV-2 mAbs to broaden the biological applicability, and these also exhibit strongly enhanced opsonic function compared to the IgG1 subclass. The improved function of the IgGh47 subclass in two distant biological systems provides new insights into antibody function.

Delivery of CD47-SIRPα checkpoint blocker by BCMA-directed UCAR-T cells enhances antitumor efficacy in multiple myeloma

In the treatment of relapsed or refractory multiple myeloma patients, BCMA-directed autologous CAR-T cells have showed excellent anti-tumor activity. However, their widespread application is limited due to the arguably cost and time-consuming. Multiple myeloma cells highly expressed CD47 molecule and interact with the SIRPα ligand on the surface of macrophages, in which evade the clearance of macrophages through the activation of "don't eat me" signal. In this study, a BCMA-directed universal CAR-T cells, BC404-UCART, secreting a CD47-SIRPα blocker was developed using CRISPR/Cas9 gene-editing system. BC404-UCART cells significantly inhibited tumor growth and prolonged the survival of mice in the xenograft model. The anti-tumor activity of BC404-UCART cells was achieved via two mechanisms, on the one hand, the UCAR-T cells directly killed tumor cells, on the other hand, the BC404-UCART cells enhanced the phagocytosis of macrophages by secreting anti-CD47 nanobody hu404-hfc fusion that blocked the "don't eat me" signal between macrophages and tumor cells, which provides a potential strategy for the development of novel "off-the-shelf" cellular immunotherapies for the treatment of multiple myeloma.

A human immune system (HIS) mouse model that dissociates roles for mouse and human FcR+ cells during antibody-mediated immune responses

Human immune system (HIS) mice provide a model to study human immune responses in vivo. Currently available HIS mouse models may harbor mouse Fc Receptor (FcR)-expressing cells that exert potent effector functions following administration of human Ig. Previous studies showed that the ablation of the murine FcR gamma chain (FcR-γ) results in loss of antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis in vivo. We created a new FcR-γ-deficient HIS mouse model to compare host (mouse) versus graft (human) effects underlying antibody-mediated immune responses in vivo. FcR-γ-deficient HIS recipients lack expression and function of mouse activating FcRs and can be stably and robustly reconstituted with human immune cells. By screening blood B-cell depletion by rituximab Ig variants, we found that human FcγRs-mediated IgG1 effects, whereas mouse activating FcγRs were dominant in IgG4 effects. Complement played a role as an IgG1 variant (IgG1 K322A) lacking complement binding activity was largely ineffective. Finally, we provide evidence that FcγRIIIA on human NK cells could mediate complement-independent B-cell depletion by IgG1 K322A. We anticipate that our FcR-γ-deficient HIS model will help clarify mechanisms of action of exogenous administered human antibodies in vivo.

The unique properties of IgG4 and its roles in health and disease

IgG4 is the least abundant subclass of IgG in human serum and has unique functional features. IgG4 is largely unable to activate antibody-dependent immune effector responses and, furthermore, undergoes Fab (fragment antigen binding)-arm exchange, rendering it bispecific for antigen binding and functionally monovalent. These properties of IgG4 have a blocking effect, either on the immune response or on the target protein of IgG4. In this Review, we discuss the unique structural characteristics of IgG4 and how these contribute to its roles in health and disease. We highlight how, depending on the setting, IgG4 responses can be beneficial (for example, in responses to allergens or parasites) or detrimental (for example, in autoimmune diseases, in antitumour responses and in anti-biologic responses). The development of novel models for studying IgG4 (patho)physiology and understanding how IgG4 responses are regulated could offer insights into novel treatment strategies for these IgG4-associated disease settings.

Heterogeneity and Functions of Tumor-Infiltrating Antibody Secreting Cells: Lessons from Breast, Ovarian, and Other Solid Cancers

Simple Summary

B cells are gaining increasing recognition as important contributors to the tumor microenvironment, influencing, positively or negatively, tumor growth, patient survival, and response to therapies. Antibody secreting cells (ASCs) constitute a variable fraction of tumor-infiltrating B cells in most solid tumors, and they produce tumor-specific antibodies that can drive distinct immune responses depending on their isotypes and specificities. In this review, we discuss the current knowledge of the heterogeneity of ASCs infiltrating solid tumors and how both their canonical and noncanonical functions shape antitumor immunity, with a special emphasis on breast and ovarian cancers.

Abstract

Neglected for a long time in cancer, B cells and ASCs have recently emerged as critical actors in the tumor microenvironment, with important roles in shaping the antitumor immune response. ASCs indeed exert a major influence on tumor growth, patient survival, and response to therapies. The mechanisms underlying their pro- vs. anti-tumor roles are beginning to be elucidated, revealing the contributions of their secreted antibodies as well as of their emerging noncanonical functions. Here, concentrating mostly on ovarian and breast cancers, we summarize the current knowledge on the heterogeneity of tumor-infiltrating ASCs, we discuss their possible local or systemic origin in relation to their immunoglobulin repertoire, and we review the different mechanisms by which antibody (Ab) subclasses and isoforms differentially impact tumor cells and anti-tumor immunity. We also discuss the emerging roles of cytokines and other immune modulators produced by ASCs in cancer. Finally, we propose strategies to manipulate the tumor ASC compartment to improve cancer therapies.

B-Lymphocytes in the Pathophysiology of Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma is highly infiltrated by B lymphocytes but the relevance of these immune cells in tumor development has been surprisingly overlooked until recently. Based on available evidence from other solid tumors, interaction between B lymphocytes and neoplastic cells is probably not uniformly stimulatory or inhibitory. Although presentation of tumor antigens to T cells and production of antitumor immunoglobulins might intuitively suggest a prominent tumor suppressive activity, specific subsets of B lymphocytes can secrete growth factors for neoplastic cells and immunosuppressive cytokines thus promoting escape from immunosurveillance and cancer progression. Because many of these mechanisms might also be implicated in the development of PDAC, and immune-modulation of B-cell activity is nowadays possible at different levels, determining the role of B-lymphocytes in this lethal cancer becomes of utmost importance to design novel therapeutic strategies. This review aims to discuss the emerging role of B cells in PDAC tumorigenesis, progression, and associated stromal reaction.

Stepping forward in antibody-drug conjugate development

Antibody-drug conjugates (ADCs) are cancer therapeutic agents comprised of an antibody, a linker and a small-molecule payload. ADCs use the specificity of the antibody to target the toxic payload to tumor cells. After intravenous administration, ADCs enter circulation, distribute to tumor tissues and bind to the tumor surface antigen. The antigen then undergoes endocytosis to internalize the ADC into tumor cells, where it is transported to lysosomes to release the payload. The released toxic payloads can induce apoptosis through DNA damage or microtubule inhibition and can kill surrounding cancer cells through the bystander effect. The first ADC drug was approved by the United States Food and Drug Administration (FDA) in 2000, but the following decade saw no new approved ADC drugs. From 2011 to 2018, four ADC drugs were approved, while in 2019 and 2020 five more ADCs entered the market. This demonstrates an increasing trend for the clinical development of ADCs. This review summarizes the recent clinical research, with a specific focus on how the in vivo processing of ADCs influences their design. We aim to provide comprehensive information about current ADCs to facilitate future development.

Assessment of Functional Characterization and Comparability of Biotherapeutics: a Review

The development of monoclonal antibody (mAb) biosimilars is a complex process. The key to their successful development and commercialization is an in-depth understanding of the key product attributes that impact safety and efficacy and the strategies to control them. Functional assessment of mAb is a crucial part of the comparability of biopharmaceutical drugs. The development of a relevant and robust functional assay requires an interdisciplinary approach and sufficient flexibility to balance regulatory concerns as well as dynamics and variability during the manufacturing process. Although many advanced tools are available to study and compare the potency and bioactivity of the protein, most of these techniques suffer from major shortcomings that limit their routine use. These include the complexity of the task, establishment of the relevance of the chosen method with the mechanism of action (MOA) of the biosimilar, cost and extended time of analysis, and often the ambiguity in interpretation of the resulting data. To overcome or to address these challenges, the use of multiple orthogonal state-of-the-art techniques is a necessary prerequisite.

Development of a novel humanized mouse model for improved evaluation of in vivo anti-cancer effects of anti-PD-1 antibody

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of cancer in the clinic. Further discovery of novel drugs or therapeutic protocols that enhance efficacy requires reliable animal models that recapitulate human immune responses to ICI treatment in vivo. In this study, we utilized an immunodeficient NOG mouse substrain deficient for mouse FcγR genes, NOG-FcγR^−/− mice, to evaluate the anti-cancer effects of nivolumab, an anti-programmed cell death-1 (PD-1) antibody. After reconstitution of human immune systems by human hematopoietic stem cell transplantation (huNOG-FcγR^−/− mice), four different programmed death-ligand 1 (PD-L1)-positive human cancer cell lines were tested. Among them, the growth of three cell lines was strongly suppressed by nivolumab in huNOG-FcγR^−/− mice, but not in conventional huNOG mice. Accordingly, immunohistochemistry demonstrated the enhanced infiltration of human T cells into tumor parenchyma in only nivolumab-treated huNOG-FcγR^−/− mice. Consistently, the number of human T cells was increased in the spleen in huNOG-FcγR^−/− mice by nivolumab but not in huNOG mice. Furthermore, human PD-L1 expression was strongly induced in the spleen of huNOG-FcγR^−/− mice. Collectively, our results suggest that the anti-cancer effects of anti-PD-1 antibodies can be detected more clearly in NOG-FcγR^−/− mice than in NOG mice.

GD2-directed bispecific trifunctional antibody outperforms dinutuximab beta in a murine model for aggressive metastasized neuroblastoma

Background

Neuroblastoma is the most common extracranial solid tumor of childhood. Patients with high-risk disease undergo extremely aggressive therapy and nonetheless have cure rates below 50%. Treatment with the ch14.18 monoclonal antibody (dinutuximab beta), directed against the GD2 disialoganglioside, improved 5-year event-free survival in high-risk patients when administered in postconsolidation therapy and was recently implemented in standard therapy. Relapse still occurred in 57% of these patients, necessitating new therapeutic options. Bispecific trifunctional antibodies (trAbs) are IgG-like molecules directed against T cells and cancer surface antigens, redirecting T cells (via their CD3 specificity) and accessory immune cells (via their functioning Fc-fragment) toward tumor cells. We sought proof-of-concept for GD2/CD3-directed trAb efficacy against neuroblastoma.

Methods

We used two GD2-specific trAbs differing only in their CD3-binding specificity: EKTOMUN (GD2/human CD3) and SUREK (GD2/mouse Cd3). This allowed trAb evaluation in human and murine experimental settings. Tumor-blind trAb and the ch14.18 antibody were used as controls. A coculture model of human peripheral blood mononuclear cells (PBMCs) and neuroblastoma cell lines was established to evaluate trAb antitumor efficacy by assessing expression of T-cell surface markers for activation, proinflammatory cytokine release and cytotoxicity assays. Characteristics of tumor-infiltrating T cells and response of neuroblastoma metastases to SUREK treatment were investigated in a syngeneic immunocompetent neuroblastoma mouse model mimicking minimal residual disease.

Results

We show that EKTOMUN treatment caused effector cell activation and release of proinflammatory cytokines in coculture with neuroblastoma cell lines. Furthermore, EKTOMUN mediated GD2-dependent cytotoxic effects in human neuroblastoma cell lines in coculture with PBMCs, irrespective of the level of target antigen expression. This effect was dependent on the presence of accessory immune cells. Treatment with SUREK reduced the intratumor Cd4/Cd8 ratio and activated tumor infiltrating T cells in vivo. In a minimal residual disease model for neuroblastoma, we demonstrated that single-agent treatment with SUREK strongly reduced or eliminated neuroblastoma metastases in vivo. SUREK as well as EKTOMUN demonstrated superior tumor control compared with the anti-GD2 antibody, ch14.18.

Conclusions

Here we provide proof-of-concept for EKTOMUN preclinical efficacy against neuroblastoma, presenting this bispecific trAb as a promising new agent to fight neuroblastoma.

Near-infrared photoimmunotherapy targeting human-EGFR in a mouse tumor model simulating current and future clinical trials

Background

near-infrared photoimmunotherapy (NIR-PIT) is a cancer treatment that uses antibody-photoabsorber (IRDye700DX, IR700) conjugates (APCs) which bind to target cells and are photoactivated by NIR light inducing rapid necrotic cell death. NIR-PIT targeting human epidermal growth factor receptor (hEGFR) has been shown to destroy hEGFR expressing human tumor cells and to be effective in immunodeficient mouse models. NIR-PIT can also be targeted to cells in the tumor microenvironment, for instance, CD25-targeted NIR-PIT can be used to selectively deplete regulatory T cells (Tregs) within a tumor. The aim of this study was to evaluate the combined therapeutic efficacy of hEGFR and CD25-targeted NIR-PIT in a newly established hEGFR expressing murine oropharyngeal cell line (mEERL-hEGFR).

Methods

panitumumab conjugated with IR700 (pan-IR700) was used as the cancer cell-directed component of NIR-PIT and anti-CD25-F(ab′)₂-IR700 was used as the tumor microenvironment-directed component of NIR-PIT. Efficacy was evaluated using tumor-bearing mice in four groups: (1) non-treatment group (control), (2) pan-IR700 based NIR-PIT (pan-PIT), (3) anti-CD25-F(ab′)₂-IR700 based NIR-PIT (CD25-PIT), (4) combined NIR-PIT with pan-IR700 and anti-CD25- F(ab′)₂-IR700 (combined PIT).

Findings

the combined PIT group showed the greatest inhibition of tumor growth. Destruction of cancer cells likely leads to an immune response which is amplified by the loss of Tregs in the tumor microenvironment.

Interpretation

combined hEGFR and CD25-targeted NIR-PIT is a promising treatment for hEGFR expressing cancers in which Treg cells play an immunosuppressive role.

Anti-EGFR therapies in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a common malignant tumor in Southern China and South-East Asia. Regardless of initiative high response to radiotherapy, parts of patients still have relapses and metastases. It is reported that epidermal growth factor receptor (EGFR) is highly expressed in most of NPC and is a poor prognostic factor. Targeting EGFR therapies including monoclonal antibodies and EGFR tyrosine kinase inhibitors (EGFR-TKIs), offer different benefits and toxicities for patients with NPC. Herein, we summarize the clinical evidence of anti-EGFR therapies in the management of NPC and provide a direction for the treatment and research of NPC in the future.

Unidirectional transport of IgG by neonatal Fc receptor in human thyrocytes varies across different IgG subclasses

Neonatal Fc receptor (FcRn) is down-regulated in Hashimoto's thyroiditis (HT) thyrocytes and mediates IgG endocytosis in thyrocytes. The serum distribution of IgG subclasses (of TgAb and TPOAb) differs between HT patients and normal individuals. We aimed to explore the direction and regulation of FcRn-mediated IgG transport in thyrocyte monolayers and the difference between various IgG subclass transport. IgG was transported by FcRn from the basolateral to apical side in the thyrocyte monolayers grown on Transwell filters and the transport was inhibited by IFN-γ and TNF-α. Stimulation by T3 and TSH down-regulated FcRn expression in thyrocytes. IgG1 was transported preferentially over IgG2 and IgG4, which might be related to the differences in FcRn-binding affinities as shown by SPR. FcRn mediates unidirectional IgG transport in thyrocytes in a tissue-specific manner. Down-regulation of FcRn is speculated to play a protective role in HT pathogenesis by mainly reducing IgG1 transport in thyrocytes.

Deceleration of glycometabolism impedes IgG-producing B-cell-mediated tumor elimination by targeting SATB1

B lymphocytes, known as antibody producers, mediate tumor cell destruction in the manner of antibody-dependent cell-mediated cytotoxicity; however, their anti-tumor function seems to be weakened during tumorigenesis, while the underlying mechanisms remain unclear. In this study, we found that IgG mediated anti-tumor effects, but IgG-producing B cells decreased in various tumors. Considering the underlying mechanism, glycometabolism was noteworthy. We found that tumor-infiltrating B cells were glucose-starved and accompanied by a deceleration of glycometabolism. Both inhibition of glycometabolism and deprivation of glucose through tumor cells, or glucose-free treatment, reduced the differentiation of B cells into IgG-producing cells. In this process, special AT-rich sequence-binding protein-1 (SATB1) was significantly silenced in B cells. Down-regulating SATB1 by inhibiting glycometabolism or RNA interference reduced the binding of signal transducer and activator of transcription 6 (STAT6) to the promoter of germline Cγ gene, subsequently resulting in fewer B cells producing IgG. Our findings provide the first evidence that glycometabolic inhibition by tumorigenesis suppresses differentiation of B cells into IgG-producing cells, and altering glycometabolism may be promising in improving the anti-tumor effect of B cells.

T cell-mediated antitumor immune response eliminates skin tumors induced by mouse papillomavirus, MmuPV1

Previous studies of naturally occurring mouse papillomavirus (PV) MmuPV1-induced tumors in B6.Cg-Foxn1^nu/nu mice suggest that T cell deficiency is necessary and sufficient for the development of such tumors. To confirm this, MmuPV1-induced tumors were transplanted from T cell-deficient mice into immunocompetent congenic mice. Consequently, the tumors regressed and eventually disappeared. The elimination of MmuPV1-infected skin/tumors in immunocompetent mice was consistent with the induction of antitumor T cell immunity. This was confirmed by adoptive cell experiments using hyperimmune splenocytes collected from graft-recipient mice. In the present study, such splenocytes were injected into T cell-deficient mice infected with MmuPV1, and they eliminated both early-stage and fully formed tumors. We clearly show that anti-tumor T cell immunity activated during tumor regression in immunocompetent mice effectively eliminates tumors developing in T cell-deficient congenic mice. The results corroborate the notion that PV-induced tumors are strongly linked to the immune status of the host, and that PV antigens are major anti-tumor antigens. Successful anti-PV T cell responses should, therefore, lead to effective anti-tumor immune therapy in human PV-infected patients.

Decreased Serum Concentration of Total IgG Is Related to Tumor Progression in Gastric Cancer Patients

BACKGROUND

There is accumulating evidence that shows cell-mediated immunity regulated by T cells is impaired in cancer patients. Unfortunately, the mechanisms by which B cells participate in tumor immunity are only partially understood.

METHODS

The serum concentration of Immunoglobulin G (IgG) was measured by Enzyme-Linked ImmunoSorbent Assay (ELISA) in patients with gastric cancer. Immunohistochemistry was also performed using the anti- cluster of differentiation (CD)134 antibody to evaluate the number of plasma cells in the tumor tissue.

RESULTS

The total serum IgG concentration was significantly lower in patients with lymph node metastasis compared with patients without metastasis. The serum concentration of total IgG at stage III/IV was significantly lower compared with tumors classified as stage I/II. A decreased serum concentration of total IgG and IgG1 was significantly related to a poor prognosis for gastric cancer patients. Furthermore, multivariate analysis indicated that the serum concentration of IgG and lymph node metastasis were independent prognostic indicators for poorer survival. The number of plasma cells was significantly lower in gastric cancer tissue compared with non-cancerous gastric mucosa.

CONCLUSION

A decreased serum concentration of IgG was closely related to poor prognosis, indicating the possibility that impaired antibody-mediated immunity is associated with tumor progression in patients with gastric cancer.

Serum IgG4:IgG Ratio Predicts Recurrence of Patients with Hepatocellular Carcinoma after Curative Resection

Aim: IgG4 is associated with a Th1-to-Th2 switch, which plays a vital role in metastasis, in patients with malignances; thus, we aimed to investigate its clinical significance in predicting hepatocellular carcinoma (HCC) recurrence in the present study.

Methods: The correlation between serum IgG4:IgG ratio and recurrence was analyzed in a cohort of 195 patients undergoing curative resection in 2012. Another 100 patients were analyzed in a prospective independent cohort during 2012-2013 to validate the value of serum IgG4. Serum IgG4 and total IgG concentrations were measured with an automatic immune analyzer and the optimal cutoff value for serum IgG4 levels was determined by X-tile software.

Results: Our data revealed that serum IgG4:IgG were significantly elevated in patients with tumor recurrence (P<0.05). A cutoff IgG:IgG4 ratio of 0.08 was set to stratify HCC patients into high (>0.08) and low (≤0.08) groups. High serum IgG4:IgG ratio correlated with significantly shorter time-to-recurrence (median 11.85 months vs. 39.20, P=0.005). Univariate and multivariate analyses demonstrated that serum IgG4:IgG ratio is an independent indicator of tumor recurrence and this retained its clinical significance even in conventional low-recurrence-risk subgroups, including patients with low α-fetoprotein and early-stage diseases.

Conclusion: Our results demonstrated that elevated serum IgG4:IgG ratio is associated with poor clinical outcomes in HCC patients and therefore, and can serve as a novel prognostic predictor for HCC patients undergoing resection. Analyzing serum IgG4 would be useful to tailor individualized therapies for patients.

Affinity of human IgG subclasses to mouse Fc gamma receptors

Human IgG is the main antibody class used in antibody therapies because of its efficacy and longer half-life, which are completely or partly due to FcγR-mediated functions of the molecules. Preclinical testing in mouse models are frequently performed using human IgG, but no detailed information on binding of human IgG to mouse FcγRs is available. The orthologous mouse and human FcγRs share roughly 60-70% identity, suggesting some incompatibility. Here, we report binding affinities of all mouse and human IgG subclasses to mouse FcγR. Human IgGs bound to mouse FcγR with remarkably similar binding strengths as we know from binding to human ortholog receptors, with relative affinities IgG3>IgG1>IgG4>IgG2 and FcγRI>>FcγRIV>FcγRIII>FcγRIIb. This suggests human IgG subclasses to have similar relative FcγR-mediated biological activities in mice.

An Fc engineering approach that modulates antibody-dependent cytokine release without altering cell-killing functions

Cytotoxic therapeutic monoclonal antibodies (mAbs) often mediate target cell-killing by eliciting immune effector functions via Fc region interactions with cellular and humoral components of the immune system. Key functions include antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), and complement-dependent cytotoxicity (CDC). However, there has been increased appreciation that along with cell-killing functions, the induction of antibody-dependent cytokine release (ADCR) can also influence disease microenvironments and therapeutic outcomes. Historically, most Fc engineering approaches have been aimed toward modulating ADCC, ADCP, or CDC. In the present study, we describe an Fc engineering approach that, while not resulting in impaired ADCC or ADCP, profoundly affects ADCR. As such, when peripheral blood mononuclear cells are used as effector cells against mAb-opsonized tumor cells, the described mAb variants elicit a similar profile and quantity of cytokines as IgG1. In contrast, although the variants elicit similar levels of tumor cell-killing as IgG1 with macrophage effector cells, the variants do not elicit macrophage-mediated ADCR against mAb-opsonized tumor cells. This study demonstrates that Fc engineering approaches can be employed to uncouple macrophage-mediated phagocytic and subsequent cell-killing functions from cytokine release.

A high number of IgG4-positive cells in gastric cancer tissue is associated with tumor progression and poor prognosis

IgG4-related disease is a newly defined disease characterized by elevated serum IgG4 levels and infiltration of affected organs by IgG4-positive plasma cells. Recently, increased IgG4 levels were reported to be closely related with malignancy. To assess the relationship between IgG4 and the progression of gastric cancer, we immunohistochemically stained in this study gastric cancer tissue samples for IgG4-positive cells using an anti-IgG4 antibody. In addition, pre- and postoperative serum concentrations of IgG4 were measured, using an enzyme-linked immunosorbent assay. In gastric cancer samples, the number of CD138-positive plasma cells was significantly lower and the number of IgG4-positive cells significantly higher than in non-cancerous gastric mucosa. The number of IgG4-positive cells was significantly correlated with gross tumor appearance, tumor depth, lymph node metastasis, venous invasion, and lymphatic invasion. Prognosis was significantly poorer in patients with a high number of IgG4-positive cells than in those with a low number. Multivariate analysis indicated that both the number of IgG4-positive cells and the depth of tumor invasion were independently prognostic of survival. In conclusion, in gastric cancer, the number of IgG4-positive cells is increased and this is closely associated with gastric cancer progression.

Deglycosylation of mAb by EndoS for improved molecular imaging

PURPOSE

Monoclonal antibodies (mAbs) have been shown preclinically as reliable targeting moieties for antigen imaging using near-infrared fluorescence (NIRF) molecular imaging. However, crystallizable fragment-gamma receptor (FcγRs) expressed on immune cells also bind mAbs through defined epitopes on the constant fragment (Fc) of IgG. Herein, we evaluate the potential impact Fc interactions have on mAb agent imaging specificity.

PROCEDURE

Through the removal of conserved glycans within the Fc domain, shown to have Fc/FcγR interactions, we evaluate their impact on non-specific binding/accumulation of a NIRF-labeled mAb-based imaging agent in lymph nodes (LNs) in inflamed animals and in an orthotopic prostate cancer animal model of LN metastasis.

RESULTS

Deglycosylation of a murine mAb against the human epithelial cell adhesion marker using endoglycosidase EndoS significantly reduced non-specific binding in the LNs of inflamed animals and in cancer-negative LNs of tumor-bearing animals. Sensitivity remained unchanged while improvement in imaging specificity increased imaging accuracy.

CONCLUSION

The reduction of non-specific binding through deglycosylation of a mAb-based imaging agent shows that reducing Fc/FcγR interactions can improve imaging accuracy.

Influence of IgG Subclass on Human Antimannan Antibody-Mediated Resistance to Hematogenously Disseminated Candidiasis in Mice

Candida albicans is a yeast-like pathogen and can cause life-threatening systemic candidiasis. Its cell surface is enriched with mannan that is resistant to complement activation. Previously, we developed the recombinant human IgG1 antimannan antibody M1g1. M1g1 was found to promote complement activation and phagocytosis and protect mice from systemic candidiasis. Here, we evaluate the influence of IgG subclass on antimannan antibody-mediated protection. Three IgG subclass variants of M1g1 were constructed: M1g2, M1g3, and M1g4. The IgG subclass identity for each variant was confirmed with DNA sequence and subclass-specific antibodies. These variants contain identical M1 Fabs and exhibited similar binding affinities for C. albicans yeast and purified mannan. Yeast cells and hyphae recovered from the kidney of antibody-treated mice with systemic candidiasis showed uniform binding of each variant, indicating constitutive expression of the M1 epitope and antibody opsonization in the kidney. All variants promoted deposition of both murine and human C3 onto the yeast cell surface, with M1g4 showing delayed activation, as determined by flow cytometry and immunofluorescence microscopy. M1g4-mediated complement activation was found to be associated with its M1 Fab that activates the alternative pathway in an Fc-independent manner. Treatment with each subclass variant extended the survival of mice with systemic candidiasis (P < 0.001). However, treatment with M1g1, M1g3, or M1g4, but not with M1g2, also reduced the kidney fungal burden (P < 0.001). Thus, the role of human antimannan antibody in host resistance to systemic candidiasis is influenced by its IgG subclass.

Production of monoclonal antibodies in plants for cancer immunotherapy

Plants are considered as an alternative platform for recombinant monoclonal antibody (mAb) production due to the improvement and diversification of transgenic techniques. The diversity of plant species offers a multitude of possibilities for the valorization of genetic resources. Moreover, plants can be propagated indefinitely, providing cheap biomass production on a large scale in controlled conditions. Thus, recent studies have shown the successful development of plant systems for the production of mAbs for cancer immunotherapy. However, their several limitations have to be resolved for efficient antibody production in plants.

IgG autoantibody subclasses altered in immuno-related hemocytopenia

Recently, we have detected autoantibodies to bone marrow (BM) hemopoietic cells in some idiopathic cytopenia of undetermined significance (ICUS), terming as immunorelated hemocytopenia. Immunoglobulin G consists of 4 subclasses which have different biological functions in many diseases. In this study, we analyzed the alterations of IgG subclasses in 27 IRH patients compared with 20 ICUS patients and 20 normal controls. The results showed that IgG1 and IgG3 levels were increased in the bone marrow supernatant in IRH patients, and had inverse correlations with hematopoietic function. Meanwhile IgG1 level had a positive correlation with the proportion of CD5+ B lymphocytes. Using immunohistochemical staining, IgG1 were also detected on bone marrow nucleated cells in IRH patients. All these results indicated that IgG1 on bone marrow cells in some IRH patients might be involved in the destruction of hematopoietic cells leading to cytopenia and might be a novel therapeutic target in future.

Chimeric antigen receptors with mutated IgG4 Fc spacer avoid fc receptor binding and improve T cell persistence and antitumor efficacy

The success of adoptive therapy using chimeric antigen receptor (CAR)-expressing T cells partly depends on optimal CAR design. CARs frequently incorporate a spacer/linker region based on the constant region of either IgG1 or IgG4 to connect extracellular ligand-binding with intracellular signaling domains. Here, we evaluated the potential for the IgG4-Fc linker to result in off-target interactions with Fc gamma receptors (FcγRs). As proof-of-principle, we focused on a CD19-specific scFv-IgG4-CD28-zeta CAR and found that, in contrast to CAR-negative cells, CAR+ T cells bound soluble FcγRs in vitro and did not engraft in NSG mice. We hypothesized that mutations to avoid FcγR binding would improve CAR+ T cell engraftment and antitumor efficacy. Thus, we generated CD19-specific CARs with IgG4-Fc spacers that had either been mutated at two sites (L235E; N297Q) within the CH2 region (CD19R(EQ)) or incorporated a CH2 deletion (CD19Rch2Δ). These mutations reduced binding to soluble FcγRs without altering the ability of the CAR to mediate antigen-specific lysis. Importantly, CD19R(EQ) and CD19Rch2Δ T cells exhibited improved persistence and more potent CD19-specific antilymphoma efficacy in NSG mice. Together, these studies suggest that optimal CAR function may require the elimination of cellular FcγR interactions to improve T cell persistence and antitumor responses.

IgE immunotherapy: a novel concept with promise for the treatment of cancer

The importance of antibodies in activating immune responses against tumors is now better appreciated with the emergence of checkpoint blockade antibodies and with engineered antibody Fc domains featuring enhanced capacity to focus potent effector cells against cancer cells. Antibodies designed with Fc regions of the IgE class can confer natural, potent, long-lived immune surveillance in tissues through tenacious engagement of high-affinity cognate Fc receptors on distinct, often tumor-resident immune effector cells, and through ability to activate these cells under tumor-induced Th2-biased conditions. Here, we review the properties that make IgE a contributor to the allergic response and a critical player in the protection against parasites, which also support IgE as a novel anti-cancer modality. We discuss IgE-based active and passive immunotherapeutic approaches in disparate in vitro and in vivo model systems, collectively suggesting the potential of IgE immunotherapies in oncology. Translation toward clinical application is now in progress.

Spontaneous antibodies against Engrailed-2 (EN2) protein in patients with prostate cancer

We reported the expression of the homeodomain-containing transcription factor Engrailed-2 (EN2) in prostate cancer and showed that the presence of EN2 protein in the urine was highly predictive of prostate cancer. This study aimed to determine whether patients with prostate cancer have EN2 autoantibodies, what the prevalence of these antibodies is and whether they are associated with disease stage. The spontaneous immunoglobulin (Ig)G immune response against EN2 and for comparison the tumour antigen New York Esophageal Squamous Cell Carcinoma 1 (NY-ESO-1), were tested by enzyme-linked immunosorbent assay (ELISA) in three different cohorts of prostate cancer patients as well as a group of men genetically predisposed to prostate cancer. Thirty-two of 353 (9·1%) of the SUN cohort representing all stages of prostate cancer demonstrated EN2 IgG responses, 12 of 107 patients (11·2%) in the advanced prostate cancer patients showed responses, while only four of 121 patients (3·3%) with castrate-resistant prostate cancer showed EN2 autoantibodies. No significant responses were found in the predisposed group. Anti-EN2 IgG responses were significantly higher in patients with prostate cancer compared to healthy control males and similarly prevalent to anti-NY-ESO-1 responses. While EN2 autoantibodies are not a useful diagnostic or monitoring tool, EN2 immunogenicity provides the rationale to pursue studies using EN2 as an immunotherapeutic target.

Cetuximab-mediated ADCC activity is correlated with the cell surface expression level of EGFR but not with the KRAS/BRAF mutational status in colorectal cancer

Cetuximab, an IgG1 monoclonal antibody against the epidermal growth factor receptor (EGFR), is widely used for the treatment of metastatic colorectal cancer (mCRC). One of the mechanisms of action is considered to be antibody-dependent cell-mediated cytotoxicity (ADCC) triggered by Fcγ-R on natural killer cells. However, whether ADCC is associated with EGFR expression and/or the mutational status of EGF downstream effectors (KRAS and BRAF) in colorectal cancer (CRC) remains unclear. The aim of the present study was to verify whether ADCC activities are associated with the cell surface expression levels of EGFR and/or the mutational status of KRAS and BRAF. Five human CRC cell lines with different cell surface expression levels of EGFR and different KRAS and BRAF mutational statuses were selected to evaluate ADCC activity using peripheral blood mononuclear cells (PBMCs) from healthy human donors. Furthermore, tumor cells from resected specimens of CRC patients were used to evaluate the cell surface expression level of EGFR using immunohistochemistry and the KRAS and BRAF mutational statuses using direct sequencing, while the ADCC activity was examined using PBMCs from the same CRC patients. A strong correlation was observed between the expression levels of EGFR and the ADCC activities in the cell lines (correlation coefficient: 0.949; P=0.003). Of the 13 resected specimens, a high ADCC activity level was significantly observed in tumor cells with high expression levels of cell surface EGFR, when compared with that in the tumor cells with low expression levels (P=0.027). In both CRC cell lines and tumor cells from CRC patients, the ADCC activities were significantly associated with the cell surface expression levels of EGFR [standard partial regression coefficients: 0.911 (P=0.017) and 0.660 (P=0.018), respectively], but not with the mutational status of KRAS and BRAF [standard partial regression coefficient: -0.101 (P=0.631) and 0.160 (P=0.510), respectively]. Cetuximab-mediated ADCC activity may be correlated with the cell surface expression level of EGFR, regardless of the mutational statuses of KRAS and BRAF, in CRC.

Antibody-based tumor vascular theranostics targeting endosialin/TEM1 in a new mouse tumor vascular model

Tumor endothelial marker 1 (TEM1, endosialin) is a tumor vascular marker with significant diagnostic and therapeutic potential. However, in vivo small animal models to test affinity reagents specifically targeted to human (h)TEM1 are limited. We describe a new mouse tumor model where tumor vascular endothelial cells express hTEM1 protein.

METHODS

Immortalized murine endothelial cells MS1 were engineered to express hTEM1 and firefly luciferase and were inoculated in nude mice either alone, to form hemangioma-like endothelial grafts, or admixed with ID8 ovarian tumor cells, to form chimeric endothelial-tumor cell grafts. MORAb-004, a monoclonal humanized IgG 1 antibody specifically recognizing human TEM1 was evaluated for targeted theranostic applications, i.e., for its ability to affect vascular grafts expressing hTEM1 as well as being a tool for molecular positron emission tomography (PET) imaging.

RESULTS

Naked MORAb-004 treatment of mice bearing angioma grafts or chimeric endothelial-tumor grafts significantly suppressed the ability of hTEM1-positive endothelial cells, but not control endothelial cells, to form grafts and dramatically suppressed local angiogenesis. In addition, highly efficient radioiodination of MORAb-004 did not impair its affinity for hTEM1, and [ (124)I]-MORAb-004-PET enabled non-invasive visualization of tumors enriched with hTEM1-positive, but not hTEM1 negative vasculature with high degree of specificity and sensitivity.

CONCLUSION

The development of a new robust endothelial graft model expressing human tumor vascular proteins will help accelerate the development of novel theranostics targeting the tumor vasculature, which exhibit affinity specifically to human targets but not their murine counterparts. Our results also demonstrate the theranostic potential of MORAb-004 as PET imaging tracer and naked antibody therapy for TEM1-positive tumor.

Chimeric antibody c.8B6 to O-acetyl-GD2 mediates the same efficient anti-neuroblastoma effects as therapeutic ch14.18 antibody to GD2 without antibody induced allodynia

Background

Anti-GD2 antibody is a proven therapy for GD2-postive neuroblastoma. Monoclonal antibodies against GD2, such as chimeric mAb ch14.18, have become benchmarks for neuroblastoma therapies. Pain, however, can limit immunotherapy with anti-GD2 therapeutic antibodies like ch14.18. This adverse effect is attributed to acute inflammation via complement activation on GD2-expressing nerves. Thus, new strategies are needed for the development of treatment intensification strategies to improve the outcome of these patients.

Methodology/Principal Findings

We established the mouse-human chimeric antibody c.8B6 specific to OAcGD2 in order to reduce potential immunogenicity in patients and to fill the need for a selective agent that can kill neuroblastoma cells without inducing adverse neurological side effects caused by anti-GD2 antibody immunotherapy. We further analyzed some of its functional properties compared with anti-GD2 ch14.18 therapeutic antibody. With the exception of allodynic activity, we found that antibody c.8B6 shares the same anti-neuroblastoma attributes as therapeutic ch14.18 anti-GD2 mAb when tested in cell-based assay and in vivo in an animal model.

Conclusion/Significance

The absence of OAcGD2 expression on nerve fibers and the lack of allodynic properties of c.8B6–which are believed to play a major role in mediating anti-GD2 mAb dose-limiting side effects–provide an important rationale for the clinical application of c.8B6 in patients with high-risk neuroblastoma.

Phosphatidylserine exposure on the surface of Leishmania amazonensis amastigotes modulates in vivo infection and dendritic cell function

Leishmania amazonensis parasites can cause diverse forms of leishmaniasis in humans and persistent lesions in most inbred strains of mice. In both cases, the infection is characterized by a marked immunosuppression of the host. We previously showed that amastigote forms of the parasite make use of surface-exposed phosphatidylserine (PS) molecules to infect host cells and promote alternative macrophage activation, leading to uncontrolled intracellular proliferation of the parasites. In this study, we demonstrated that treatment of infected mice with a PS-targeting monoclonal antibody ameliorated parasite loads and lesion development, which correlated with increased proliferative responses by lymphocytes. In addition, we observed an enhanced dendritic cell (DC) activation and antigen presentation in vitro. Our data imply that the recognition of PS exposed on the surface of amastigotes plays a role in down-modulating DC functions, in a matter similar to that of apoptotic cell clearance. This study provides new information regarding the mechanism of immune suppression in Leishmania infection.

Nectin-2 is a potential target for antibody therapy of breast and ovarian cancers

Background

Nectin-2 is a Ca²⁺-independent cell-cell adhesion molecule that is one of the plasma membrane components of adherens junctions. However, little has been reported about the involvement of Nectin-2 in cancer.

Methods

To determine the expression of Nectin-2 in cancer tissues and cancer cell lines, we performed gene expression profile analysis, immunohistochemistry studies, and flow cytometry analysis. We also investigated the potential of this molecule as a target for antibody therapeutics to treat cancers by generating and characterizing an anti-Nectin-2 rabbit polyclonal antibody (poAb) and 256 fully human anti-Nectin-2 monoclonal antibodies (mAbs). In addition, we tested anti-Nectin-2 mAbs in several in vivo tumor growth inhibition models to investigate the primary mechanisms of action of the mAbs.

Results

In the present study, we found that Nectin-2 was over-expressed in clinical breast and ovarian cancer tissues by using gene expression profile analysis and immunohistochemistry studies. Nectin-2 was over-expressed in various cancer cell lines as well. Furthermore, the polyclonal antibody specific to Nectin-2 suppressed the in vitro proliferation of OV-90 ovarian cancer cells, which express endogenous Nectin-2 on the cell surface. The anti-Nectin-2 mAbs we generated were classified into 7 epitope bins. The anti-Nectin-2 mAbs demonstrated antibody-dependent cellular cytotoxicity (ADCC) and epitope bin-dependent features such as the inhibition of Nectin-2-Nectin-2 interaction, Nectin-2-Nectin-3 interaction, and in vitro cancer cell proliferation. A representative anti-Nectin-2 mAb in epitope bin VII, Y-443, showed anti-tumor effects against OV-90 cells and MDA-MB-231 breast cancer cells in mouse therapeutic models, and its main mechanism of action appeared to be ADCC.

Conclusions

We observed the over-expression of Nectin-2 in breast and ovarian cancers and anti-tumor activity of anti-Nectin-2 mAbs via strong ADCC. These findings suggest that Nectin-2 is a potential target for antibody therapy against breast and ovarian cancers.

IgG4 subclass antibodies impair antitumor immunity in melanoma

Host-induced antibodies and their contributions to cancer inflammation are largely unexplored. IgG4 subclass antibodies are present in IL-10-driven Th2 immune responses in some inflammatory conditions. Since Th2-biased inflammation is a hallmark of tumor microenvironments, we investigated the presence and functional implications of IgG4 in malignant melanoma. Consistent with Th2 inflammation, CD22+ B cells and IgG4(+)-infiltrating cells accumulated in tumors, and IL-10, IL-4, and tumor-reactive IgG4 were expressed in situ. When compared with B cells from patient lymph nodes and blood, tumor-associated B cells were polarized to produce IgG4. Secreted B cells increased VEGF and IgG4, and tumor cells enhanced IL-10 secretion in cocultures. Unlike IgG1, an engineered tumor antigen-specific IgG4 was ineffective in triggering effector cell-mediated tumor killing in vitro. Antigen-specific and nonspecific IgG4 inhibited IgG1-mediated tumoricidal functions. IgG4 blockade was mediated through reduction of FcγRI activation. Additionally, IgG4 significantly impaired the potency of tumoricidal IgG1 in a human melanoma xenograft mouse model. Furthermore, serum IgG4 was inversely correlated with patient survival. These findings suggest that IgG4 promoted by tumor-induced Th2-biased inflammation may restrict effector cell functions against tumors, providing a previously unexplored aspect of tumor-induced immune escape and a basis for biomarker development and patient-specific therapeutic approaches.

Crosstalk between human IgG isotypes and murine effector cells

Development of human therapeutic Abs has led to reduced immunogenicity and optimal interactions with the human immune system in patients. Humanization had as a consequence that efficacy studies performed in mouse models, which represent a crucial step in preclinical development, are more difficult to interpret because of gaps in our knowledge of the activation of murine effector cells by human IgG (hIgG) remain. We therefore developed full sets of human and mouse isotype variants of human Abs targeting epidermal growth factor receptor and CD20 to explore the crosstalk with mouse FcγRs (mFcγRs) and murine effector cells. Analysis of mFcγR binding demonstrated that hIgG1 and hIgG3 bound to all four mFcγRs, with hIgG3 having the highest affinity. hIgG1 nevertheless was more potent than hIgG3 in inducing Ab-dependent cellular cytotoxicity (ADCC) and Ab-dependent cellular phagocytosis with mouse NK cells, mouse polymorphonuclear leukocytes, and mouse macrophages. hIgG4 bound to all mFcγRs except mFcγRIV and showed comparable interactions with murine effector cells to hIgG3. hIgG4 is thus active in the murine immune system, in contrast with its inert phenotype in the human system. hIgG2 bound to mFcγRIIb and mFcγRIII, and induced potent ADCC with mouse NK cells and mouse polymorphonuclear leukocytes. hIgG2 induced weak ADCC and, remarkably, was unable to induce Ab-dependent cellular phagocytosis with mouse macrophages. Finally, the isotypes were studied in s.c. and i.v. tumor xenograft models, which confirmed hIgG1 to be the most potent human isotype in mouse models. These data enhance our understanding of the crosstalk between hIgGs and murine effector cells, permitting a better interpretation of human Ab efficacy studies in mouse models.

Development and validation of an antibody-dependent cell-mediated cytotoxicity-reporter gene assay

Humanized monoclonal antibodies (mAbs) are the fastest growing class of biological therapeutics that are being developed for various medical indications, and more than 30 mAbs are already approved and in the market place. Antibody-dependent cell-mediated cytotoxicity (ADCC) is an important biological function attributed to the mechanism of action of several therapeutic antibodies, particularly oncology targeting mAbs. The ADCC assay is a complicated and highly variable assay. Thus, the use of an ADCC assay as a lot release test or a stability test for clinical trial batches of mAbs has been a substantial challenge to install in quality control laboratories. We describe here the development and validation of an alternate approach, an ADCC-reporter gene assay that is based on the key attributes of the PBMC-based ADCC assay. We tested the biological relevance of this assay using an anti-CD20 based model and demonstrated that this ADCC-reporter assay correlated well with standard ADCC assays when induced with the drugable human isotypes [IgG1, IgG2, IgG4, IgG4S > P (S228P) and IgG4PAA (S228P, F234A, L235A)] and with IgG1 isotype variants with varying amounts of fucosylation. This data demonstrates that the ADCC-reporter gene assay has performance characteristics (accuracy, precision and robustness) to be used not only as a potency assay for lot release and stability testing for antibody therapeutics, but also as a key assay for the characterization and process development of therapeutic molecules.

Enhanced potency of a fucose-free monoclonal antibody being developed as an Ebola virus immunoprotectant

No countermeasures currently exist for the prevention or treatment of the severe sequelae of Filovirus (such as Ebola virus; EBOV) infection. To overcome this limitation in our biodefense preparedness, we have designed monoclonal antibodies (mAbs) which could be used in humans as immunoprotectants for EBOV, starting with a murine mAb (13F6) that recognizes the heavily glycosylated mucin-like domain of the virion-attached glycoprotein (GP). Point mutations were introduced into the variable region of the murine mAb to remove predicted human T-cell epitopes, and the variable regions joined to human constant regions to generate a mAb (h-13F6) appropriate for development for human use. We have evaluated the efficacy of three variants of h-13F6 carrying different glycosylation patterns in a lethal mouse EBOV challenge model. The pattern of glycosylation of the various mAbs was found to correlate to level of protection, with aglycosylated h-13F6 providing the least potent efficacy (ED(50) = 33 μg). A version with typical heterogenous mammalian glycoforms (ED(50) = 11 μg) had similar potency to the original murine mAb. However, h-13F6 carrying complex N-glycosylation lacking core fucose exhibited superior potency (ED(50) = 3 μg). Binding studies using Fcγ receptors revealed enhanced binding of nonfucosylated h-13F6 to mouse and human FcγRIII. Together the results indicate the presence of Fc N-glycans enhances the protective efficacy of h-13F6, and that mAbs manufactured with uniform glycosylation and a higher potency glycoform offer promise as biodefense therapeutics.

Polymorphonuclear neutrophils and cancer: intense and sustained neutrophilia as a treatment against solid tumors

Polymorphonuclear neutrophils (PMN) are the most abundant circulating immune cells and represent the first line of immune defense against infection. This review of the biomedical literature of the last 40 years shows that they also have a powerful antitumoral effect under certain circumstances. Typically, the microenvironment surrounding a solid tumor possesses many of the characteristics of chronic inflammation, a condition considered very favorable for tumor growth and spread. However, there are many circumstances that shift the chronic inflammatory state toward an acute inflammatory response around a tumor. This shift seems to convert PMN into very efficient anticancer effector cells. Clinical reports of unexpected antitumoral effects linked to the prolonged use of granulocyte colony-stimulating factor, which stimulates an intense and sustained neutrophilia, suggest that an easy way to fight solid tumors would be to encourage the development of intense peritumoral PMN infiltrates. Specifically designed clinical trials are urgently needed to evaluate the safety and efficacy of such drug-induced neutrophilia in patients with solid tumors. This antitumoral role of neutrophils may provide new avenues for the clinical treatment of cancer.

Synergistic antitumor effects of lenalidomide and rituximab on mantle cell lymphoma in vitro and in vivo

Rituximab (RTX), a chimeric anti-CD20 antibody, is associated with direct induction of apoptosis and antibody-dependent cell-mediated cytotoxicity (ADCC) with clinical efficacy in mantle cell lymphoma (MCL). Lenalidomide (LEN), a novel immunomodulatory agent, sensitizes tumor cells and enhances ADCC. Our study attempted to elucidate the mechanism of LEN-enhanced RTX-mediated cytotoxicity of MCL cells. We found that LEN and RTX induced growth inhibition of both cultured and fresh primary MCL cells. LEN enhanced RTX-induced apoptosis via upregulating phosphorylation of c-Jun N-terminal protein kinases (JNK), Bcl-2, Bad; increasing release of cytochrome-c; enhancing activation of caspase-3, -8, -9 and cleavage of PARP. Meanwhile, LEN activated NK cells and increased CD16 expression on CD56(low)CD16(+) NK cells. Whole PBMCs but not NK cell-depleted PBMCs treated with LEN augmented 30% of RTX-dependent cytotoxicity. Daily treatment with LEN increased NK cells by 10-folds in SCID mice, and combination of LEN and RTX decreased tumor burden and prolonged survival of MCL-bearing SCID mice. Taken together, our study demonstrates that LEN plus RTX provides a synergistically therapeutic effect on MCL cells by enhancing apoptosis and RTX-dependent NK cell-mediated cytotoxicity and may be an optimal combination in the clinical trial of relapsed or refractory MCL.

Generation and characterization of high affinity humanized fab against hepatitis B surface antigen

5S is a mouse monoclonal IgG1 that binds to the 'a' epitope of the Hepatitis B surface antigen (HBsAg) and tested positive in an in vitro test for virus neutralization. We have earlier reported the generation of humanized single chain variable fragment (scFv) from the same. In this article we report the generation of a recombinant Fab molecule by fusing humanized variable domains of 5S with the constant domains of human IgG1. The humanized Fab expressed in E. coli and subsequently purified, retained a high binding affinity (K(D) = 3.63 nmol/L) to HBsAg and bound to the same epitope of HBsAg as the parent molecule. The humanized Fab also maintained antigen binding in the presence of various destabilizing agents like 3 M NaCl, 30% DMSO, 8 M urea, and extreme pH. This high affinity humanized Fab provides a basis for the development of therapeutic molecules that can be safely utilized for the prophylaxis and treatment for Hepatitis B infection.

Anti-glypican 3 antibodies cause ADCC against human hepatocellular carcinoma cells

Glypican 3 (GPC3), a GPI-anchored heparan sulfate proteoglycan, is expressed in the majority of hepatocellular carcinoma (HCC) tissues. Using MRL/lpr mice, we successfully generated a series of anti-GPC3 monoclonal antibodies (mAbs). GPC3 was partially cleaved between Arg358 and Ser359, generating a C-terminal 30-kDa fragment and an N-terminal 40-kDa fragment. All mAbs that induced antibody-dependent cellular cytotoxicity (ADCC) and/or complement-dependent cytotoxicity (CDC) against cells expressing GPC3 recognized the 30-kDa fragment, indicating that the C-terminal region of GPC3 serves as an epitope for mAb with ADCC and/or CDC inducing activities. Chimeric mAbs with Fc replaced by human IgG1 were created from GC33, one of the mAbs that reacted with the C-terminal 30-kDa fragment. Chimeric GC33 induced not only ADCC against GPC3-positive human HCC cells but also was efficacious against the Huh-7 human HCC xenograft. Thus, mAbs against the C-terminal 30-kDa fragment such as GC33 are useful in therapy targeting HCC.