Antibody-dependent Phagocytosis Research Articles

Development of a highly effective combination monoclonal antibody therapy against Herpes simplex virus

BackgroundInfections with Herpes simplex virus (HSV)-1 or -2 usually present as mild chronic recurrent disease, however in rare cases can result in life-threatening conditions with a large spectrum of pathology. Monoclonal antibody therapy has great potential especially to treat infections with virus resistant to standard therapies. HDIT101, a humanized IgG targeting HSV-1/2 gB was previously investigated in phase 2 clinical trials. The aim of this study was to develop a next-generation therapy by combining different antiviral monoclonal antibodies.MethodsA lymph-node derived phage display library (LYNDAL) was screened against recombinant gB from Herpes simplex virus (HSV) -1 and HDIT102 scFv was selected for its binding characteristics using bio-layer interferometry. HDIT102 was further developed as fully human IgG and tested alone or in combination with HDIT101, a clinically tested humanized anti-HSV IgG, in vitro and in vivo. T-cell stimulating activities by antigen-presenting cells treated with IgG-HSV immune complexes were analyzed using primary human cells. To determine the epitopes, the cryo-EM structures of HDIT101 or HDIT102 Fab bound to HSV-1F as well as HSV-2G gB protein were solved at resolutions < 3.5 Å.ResultsHDIT102 Fab showed strong binding to HSV-1F gB with Kd of 8.95 × 10–11 M and to HSV-2G gB with Kd of 3.29 × 10–11 M. Neutralization of cell-free virus and inhibition of cell-to-cell spread were comparable between HDIT101 and HDIT102. Both antibodies induced internalization of gB from the cell surface into acidic endosomes by binding distinct epitopes in domain I of gB and compete for binding. CryoEM analyses revealed the ability to form heterogenic immune complexes consisting of two HDIT102 and one HDIT101 Fab bound to one gB trimeric molecule. Both antibodies mediated antibody-dependent phagocytosis by antigen presenting cells which stimulated autologous T-cell activation. In vivo, the combination of HDIT101 and HDIT102 demonstrated synergistic effects on survival and clinical outcome in immunocompetent BALB/cOlaHsd mice.ConclusionThis biochemical and immunological study showcases the potential of an effective combination therapy with two monoclonal anti-gB IgGs for the treatment of HSV-1/2 induced disease conditions.

Identification of isoaspartate-modified transthyretin as potential target for selective immunotherapy of transthyretin amyloidosis

Background Numerous studies suggest a progressive accumulation of post-translationally modified peptides within amyloid fibrils, including isoaspartate (isoD) modifications. Here, we generated and characterised novel monoclonal antibodies targeting isoD-modified transthyretin (TTR). The antibodies were used to investigate the presence of isoD-modified TTR in deposits from transthyretin amyloidosis patients and to mediate antibody-dependent phagocytosis of TTR fibrils. Methods Monoclonal antibodies were generated by immunisation of mice using an isoD-modified peptide and subsequent hybridoma generation. The antibodies were characterised in terms of affinity and specificity to isoD-modified TTR using surface plasmon resonance, transmission electron microscopy and immunohistochemical staining of human cardiac tissue. The potential to elicit antibody-dependent phagocytosis of TTR fibrils was assessed using THP-1 cells. Results We developed two mouse monoclonal antibodies, 2F2 and 4D4, with high nanomolar affinity for isoD-modified TTR and strong selectivity over the unmodified epitope. Both antibodies show presence of isoD-modified TTR in human cardiac tissue, but not in freshly purified recombinant TTR, suggesting isoD modification only present in aged fibrillar deposits. Likewise, the antibodies only facilitated phagocytosis of TTR fibrils and not TTR monomers by THP-1 cells. Conclusions These antibodies label aged, non-native TTR deposits, leaving native TTR unattended and thereby potentially enabling new therapeutic approaches.

Anti-CAMP1 IgG promotes macrophage phagocytosis of Cutibacterium acnes type II

Among 5 types of the Christie-Atkins-Munch-Petersen factor (CAMP) of Cutibacterium acnes, CAMP1 is highly expressed in phylotype II as well as IB, and thought to be a virulence factor of opportunistic but fatal blood, soft tissue, and implant-related infections. The target of a human single-chain variable antibody fragment (scFv), recently isolated from a phage display library, has been identified as CAMP1 of phylotype II, using immunoprecipitation followed by mass spectrometry, phage display peptide biopanning, 3D-modelling, and ELISA. The IgG1 format of the antibody could enhance phagocytosis of C. acnes DMST 14916 by THP-1 human monocytes. Our results suggest that the antibody-dependent phagocytosis process is mediated by the caveolae membrane system and involves the induction of IL-1β. This is the first report on the study of a human antibody against CAMP1 of C. acnes phylotype II, of which a potential use as therapeutic antibody against virulence C. acnes infection is postulated.

Subtype recognition and identification of a prognosis model characterized by antibody-dependent cell phagocytosis-related genes in breast cancer.

Breast cancer (BC) is a heterogeneous tumor with a variety of etiology and clinical features. Antibody-dependent cell phagocytosis (ADCP) is the last step of immune checkpoint inhibition (ICI), and macrophages detect and recognize tumor cells, then destroy and engulf tumor cells. Despite the large number, negative regulators that inhibit phagocytic activity are still a key obstacle to the full efficacy of ICI. An ADCP-related risk score prognostic model for risk stratification as well as prognosis prediction was established in the Cancer Genome Atlas (TCGA) cohort. The predictive value of ADCP risk score in prognosis and immunotherapy was also further validated in the TCGA along with International Cancer Genome Consortium cohorts. To promote the clinical application of the risk score, a nomogram was established, with its effectiveness verified by different methods. In this study, the genes collected from previous studies were defined as ADCP-related genes. In BC patients, two ADCP-related subtypes were identified. The immune characteristics and prognostic stratification were significant different between them. We identified two subtypes associated with ADCP gene expression in breast cancer. They have significant differences in immune cells, molecular functions, HLA family genes, immune scores, stromal scores, and inflammatory gene expression, which have important guiding significance for the selection of clinical treatment methods. At the same time, we constructed a risk model based on ADCP, and the risk score can be used as a good indicator of prognosis, providing potential therapeutic advantages for chemotherapy and immunotherapy, thus helping the clinical decision-making of BC patients.

Identification of CD160-TM as a tumor target on triple negative breast cancers: possible therapeutic applications

BackgroundDespite major therapeutic advances, triple-negative breast cancer (TNBC) still presents a worth prognosis than hormone receptors-positive breast cancers. One major issue relies in the molecular and mutational heterogeneity of TNBC subtypes that is reinforced by the absence of reliable tumor-antigen that could serve as a specific target to further promote efficient tumor cell recognition and depletion. CD160 is a receptor mainly expressed by NK lymphocytes and presenting two isoforms, namely the GPI-anchored form (CD160-GPI) and the transmembrane isoform (CD160-TM). While CD160-GPI is constitutively expressed on resting cells and involved in the generation of NK cells' cytotoxic activity, CD160-TM is neo-synthesized upon activation and promotes the amplification of NK cells' killing ability.MethodsCD160 expression was assessed by immunohistochemistry (IHC) and flow cytometry on TNBC patient biopsies or cell lines, respectively. Antibody (Ab)-mediated tumor depletion was tested in vitro by performing antibody-dependent cell cytotoxicity (ADCC) and phagocytosis (ADCP) assays, and in vivo on a TNBC mouse model.ResultsPreliminary data obtained by IHC on TNBC patients' tumor biopsies revealed an unconventional expression of CD160 by TNBC tumor cells. By using a specific but conformation-dependent anti-CD160-TM Ab, we established that CD160-TM, but not CD160-GPI, was expressed by TNBC tumor cells. A conformation-independent anti-CD160-TM mAb (22B12; muIgG2a isotype) was generated and selected according to pre-defined specificity and functional criterions. In vitro functional assays demonstrated that ADCC and ADCP could be induced in the presence of 22B12, resulting in TNBC cell line apoptosis. The ability of 22B12 to exert an in vivo anti-tumor activity was also demonstrated on a TNBC murine model.ConclusionsOur data identify CD160-TM as a tumor marker for TNBC and provide a rational for the use of anti-CD160-TM antibodies as therapeutic tools in this tumor context.

Humoral profiles of toddlers and young children following SARS-CoV-2 mRNA vaccination

Although young children generally experience mild symptoms following infection with SARS-CoV-2, severe acute and long-term complications can occur. SARS-CoV-2 mRNA vaccines elicit robust immunoglobulin profiles in children ages 5 years and older, and in adults, corresponding with substantial protection against hospitalizations and severe disease. Whether similar immune responses and humoral protection can be observed in vaccinated infants and young children, who have a developing and vulnerable immune system, remains poorly understood. To study the impact of mRNA vaccination on the humoral immunity of infant, we use a system serology approach to comprehensively profile antibody responses in a cohort of children ages 6 months to 5 years who were vaccinated with the mRNA-1273 COVID-19 vaccine (25 μg). Responses are compared with vaccinated adults (100 μg), in addition to naturally infected toddlers and young children. Despite their lower vaccine dose, vaccinated toddlers elicit a functional antibody response as strong as adults, with higher antibody-dependent phagocytosis compared to adults, without report of side effects. Moreover, mRNA vaccination is associated with a higher IgG3-dependent humoral profile against SARS-CoV-2 compared to natural infection, supporting that mRNA vaccination is effective at eliciting a robust antibody response in toddlers and young children.

Rhamnose modified antibodies show improved immune killing towards EGFR-positive solid tumor cells

Therapeutic monoclonal antibodies (mAbs) against the epidermal growth factor receptor (EGFR) have shown clinical efficacy in colorectal cancer and other solid cancers. Enhancing the effector functions of these anti-EGFR mAbs is believed to be a valuable approach to achieve improved efficacy in clinical setting. Here, we report the development of an effector function-enhanced antibody by rhamnose (Rha) functionalization. Cetuximab, a human/mouse chimeric anti-EGFR mAb, was selected and site-specifically conjugated with Rha haptens. The obtained cetuximab-Rha conjugate was shown to be able to selectively redirect amounts of endogenous anti-Rha antibodies onto EGFR-positive solid tumor cells and thereby provide more Fc domains to achieve enhancement of effector functions including complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated phagocytosis (ADCP). Particularly, CDC, one powerful cell killing mechanism which is inactive in cetuximab, was dramatically improved. This study demonstrates the potential of rhamnose-modified antibody for EGFR-positive solid tumor immunotherapy.

New Frontiers in Monoclonal Antibodies for Relapsed/Refractory Diffuse Large B-Cell Lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive lymphoma. Approximately 60% of patients are cured with R-CHOP as a frontline treatment, while the remaining patients experience primary refractory or relapsed disease (R/R). The prognosis for R/R DLBCL patients who are neither eligible for autologous stem-cell transplantations nor CAR-T-cell treatment is poor, representing an important unmet need. Monoclonal antibodies (mAbs) have dramatically improved therapeutic options in anti-cancer strategies, offering new opportunities to overcome chemo-refractoriness in this challenging disease, even in cases of primary non-responder DLBCL. Several novel mAbs, characterized by different mechanisms of action and targets, are now available for R/R DLBCL. Unbound mAbs induce an immune response against cancer cells, triggering different mechanisms, including antibody-dependent cellular cytotoxicity (ADCC), activation of antibody-dependent cell-mediated phagocytosis (ADCP) and complement-dependent cytotoxicity (CDC). Antibody-drug conjugates (ADCs) and radioimmunotherapy (RIT), respectively, deliver a cytotoxic payload or a beta-emitter radionuclide to the targeted cells and nearby bystanders. Bispecific T-cell engagers (BiTes) and immune checkpoint inhibitors (ICIs) redirect and enhance the immune response against tumor cells. Here, we review therapeutic strategies based on monoclonal antibodies for R/R DLBCL.

RBD-Protein/Peptide Vaccine UB-612 Elicits Mucosal and Fc-Mediated Antibody Responses against SARS-CoV-2 in Cynomolgus Macaques.

Antibodies provide critical protective immunity against COVID-19, and the Fc-mediated effector functions and mucosal antibodies also contribute to the protection. To expand the characterization of humoral immunity stimulated by subunit protein-peptide COVID-19 vaccine UB-612, preclinical studies in non-human primates were undertaken to investigate mucosal secretion and the effector functionality of vaccine-induced antibodies in antibody-dependent monocyte phagocytosis (ADMP) and antibody-dependent NK cell activation (ADNKA) assays. In cynomolgus macaques, UB-612 induced potent serum-neutralizing, RBD-specific IgG binding, ACE2 binding-inhibition antibodies, and antibodies with Fc-mediated effector functions in ADMP and ADNKA assays. Additionally, immunized animals developed mucosal antibodies in bronchoalveolar lavage fluids (BAL). The level of mucosal or serum ADMP and ADNKA antibodies was found to be UB-612 dose-dependent. Our results highlight that the novel subunit UB-612 vaccine is a potent B-cell immunogen inducing polyfunctional antibody responses contributing to anti-viral immunity and vaccine efficacy.

Lacutamab in Patients with Relapsed and Refractory Sèzary Syndrome: Results from the Tellomak Phase 2 Trial

Introduction Cutaneous T-cell lymphoma (CTCL) is a rare form of non-Hodgkin lymphoma. Sézary syndrome (SS) is a rare, aggressive and advanced type of CTCL. It has a unique biology, with high expression of KIR3DL2, a killer immunoglobulin-like receptor, reported in more than 85% of patients. SS is characterized by erythroderma, significant blood involvement with malignant SS cells, and lymphadenopathy. These patients suffer from debilitating itching and recurrent skin infections, often affecting quality of life (QoL). SS is distinguished by its poor prognosis, as the median survival of patients is approximately 5 years. Lacutamab is a first-in-class monoclonal antibody designed to specifically deplete KIR3DL2-expressing cells via antibody-dependent cell-cytotoxicity and phagocytosis. Methods TELLOMAK is an international, open-label, Phase 2 trial with multiple cohorts (NCT03902184). We report here results from Cohort 1, designed to evaluate safety and efficacy of single agent lacutamab in patients with relapsed/refractory (R/R) SS after at least 2 prior systemic therapies including mogamulizumab. Patients had blood stage B2 (≥1000 circulating Sézary cells/mm 3) at screening based on central evaluation by flow cytometry. Patients with evidence of large cell transformation were excluded. Lacutamab 750 mg is administered as an intravenous infusion weekly × 5 weeks (w), every 2 w × 10, then every 4 w until progression or unacceptable toxicity. Primary endpoint was Objective Response Rate (ORR) by global response score based on the evaluation of 4 compartments: skin, blood, lymph nodes and viscera according to International Consensus criteria (Olsen 2011). Secondary endpoints included but not limited to additional efficacy endpoints, safety, QoL assessments. Results At the data cut-off of May 1, 2023, 56 SS patients were enrolled treated and evaluated in Cohort 1. Median age was 69 years (range: 42-86), the median prior lines of systemic therapies was 6.0 (range: 2-15), 60.7 % (n=34) had stage IVA1, 32.1 % (n=18) had stage IVA2 and 7.1% (n=4) had stage IVB disease at baseline, all patients (100%) had blood involvement (B2), 67.9% (n=38) had confluence of erythema covering ≥ 80% body surface area (T4), 35.7% (n=20) had lymph node lymphoma involvement (N3). Median follow-up was 14.4 months (95% CI 9.0-18.4). In the ITT population (n=56), Global confirmed ORR was 37.5% (n=21; 95% CI 26.0-50.6) including 2 CRs, with a median time to response of 2.8 months (range 1-9; Figure 1). Confirmed ORR in skin was 46.4% (n=26; 95% CI 34.0-59.3) including 5 CRs. Confirmed ORR in blood was 48.2% (n=27; 95% CI 35.7-61.0) including 15 CRs. Clinical Benefit Rate (CBR, defined as CR+PR+SD) was 87.5 % (n=49; 95% CI 76.4-93.8). Median PFS was 8.0 months (95% CI 4.7-21.2). Grade ≥ 3 Treatment-related (TR) Treatment-Emergent Adverse events (TEAEs) were observed in 10/56 (17.9%) pts, Serious TR TEAEs were observed in 4/56 (7.1%) and 3/56 (5.4%) pts discontinued study drug due to TR TEAE. Data from additional key endpoints will be presented. Conclusion In this SS cohort from the TELLOMAK study, our data confirm that lacutamab monotherapy shows promising clinical activity in a R/R population previously treated with 2 or more prior systemic therapies including mogamulizumab, and an overall favourable safety profile. Continued evaluation of this new targeted treatment option for patients with SS is warranted.

Immunological Subgroups Predicting Efficacy of Elotuzumab in Multiple Myeloma Patients: Insights from the GMMG-HD6 Clinical Trial

Introduction: Elotuzumab, a monoclonal antibody targeting SLAM family member 7 protein (SLAMF7) on multiple myeloma (MM) cells, has shown promise in relapsed/refractory MM when combined with immunomodulatory agents. However, its effectiveness in newly diagnosed patients did not show improved progression-free survival (PFS) nor overall survival. In a previous study we demonstrated that elotuzumab specifically depleted high SLAMF7 expressing regulatory CD8 + T cells by macrophage induced antibody dependent phagocytosis. This study aimed to identify immunological predictive factors for elotuzumab efficacy, enabling improved risk stratification and personalized treatment decisions based on the detection and quantification of SLAMF7-positive T cell subsets. Patients and Methods: This pre-planned accompanying immunological research analyzed samples from the German-Speaking Myeloma Multicenter Group (GMMG) HD6 clinical trial (NCT02495922). The trial investigated elotuzumab in combination with lenalidomide/bortezomib/dexamethasone induction and consolidation, followed by lenalidomide maintenance in transplant-eligible newly diagnosed MM patients and found no progression-free or overall survival advantage with the addition of elotuzumab in any treatment sequence. Peripheral blood samples were collected at three time points: trial inclusion (T1), after induction therapy (T2), and during consolidation or maintenance therapy (T3). Flow cytometry was used to assess T cell subpopulations. Results: Elotuzumab during induction therapy significantly reduced the percentage of regulatory SLAMF7 high expressing CD8 + CD28 - ( p &amp;lt; 0.001) and effector CD8 + T cells ( p &amp;lt; 0.001) in MM patients after induction therapy and during maintenance therapy. A T2 landmark multivariate analysis (after induction therapy) revealed that a higher percentage of effector CD8 + T cells at T1 showed a borderline advantageous effect on the progression-free survival (PFS) ( HR = 0.98 [CI 95% 0.97; 1.00], p = 0.010) regardless of the study arm. Further, in a multivariate analysis a high regulatory CD8 + T cell level at T2 was associated with an adverse PFS in patients receiving elotuzumab in addition to lenalidomide during consolidation and maintenance (PFS from T2 for high vs. low regulatory CD8 + T cell levels at T2, HR = 3.64 [CI 95% 1.58; 8.36], p = 0.002 for patients that received elotuzumab during consolidation and maintenance only; regulatory CD8 + T cells at T2 [high versus low] HR = 5.93 [CI 95% 2.30; 15.26], p &amp;lt; 0.001 for patients that received elotuzumab during induction, consolidation and maintenance). Conclusion: The efficacy of elotuzumab in MM patients may be influenced by the frequency of regulatory CD8 + T cells after induction therapy. As high levels of regulatory CD8 + T cells showed adverse progression-free survival in MM patients, the assessment of the level of regulatory CD8 + SLAMF7 + T cells could be a prerequisite for MM patients' response to elotuzumab. This study highlights the importance of T cell level-driven immunological treatment approaches when utilizing elotuzumab.

Anti-PD-1 Antibody (Tislelizumab) Combined with R-CHOP for the Treatment of Previously Untreated Primary Mediastinal B-Cell Lymphoma: A Prospective Phase II Study

Background: Primary mediastinal B-cell lymphoma (PMBCL) is a rare aggressive B-cell lymphoma of thymic origin. Due to the low incidence rate of PMBCL, there is currently no internationally accepted standard first-line treatment regimen. Dose-adjusted (DA) EPOCH-R which is the more commonly used first-line therapy plan is not so effective because patients usually cannot tolerate it. The R-CHOP regimen is comparable to the R-DA-EPOCH for the first-line treatment of PMBCL in terms of survival and has a better safety profile (Bhatt, V.R. et al, Cancer Treat Rev 2015; Iwanicka el al., Curr Hematol Malig Rep 2014). Meanwhile, patients with PMBCL usually have alterations of 9p24.1, leading to overexpression of PDL-1/2. Previous studies have found that PD-1 monoclonal antibody shows good efficacy in recurrent and refractory PMBCL (Steidl et al., Blood 2011; Zinzani et al., Blood 2017). Tislelizumab, a humanized IgG4 antibody that binds PD-1 with high affinity, minimizes binding to Fcγ receptor 1 (FcγRI) on macrophages by the genetic engineering of Fc segment, abrogating antibody-dependent phagocytosis (ADCP)-induced T-cell clearance. The efficacy and safety of its combination with R-CHOP in previously untreated PMBCL is not yet clear. We speculate that the combination of both may be a new option for the first-line therapy for PMBCL patients with good efficacy and low toxicity. Methods: This is a single-arm, multi-center, phase II clinical study (ChiCTR2100044313). Patients aged 18 years or older with a diagnosis of PMBCL and previously untreated were eligible. Eligible patients received 6 cycles of Tislelizumab (200 mg D1), Rituximab (375 mg/m 2 D1), Cyclophosphamide (750 mg/m 2 D2), Pirarubicin (50 mg/m 2 D2), Vincristine (1.4 mg/m 2, maximum dose 2 mg, D2), Prednisone (100 mg/d D2-6), every 21 days for 1 cycle. Disease response assessments were performed by positron emission tomography and computed tomography (PET-CT) or enhanced CT every two cycles, meanwhile peripheral blood ctDNA was monitored, and treatment-related adverse effects were assessed and recorded. The primary endpoint was objective remission rate (ORR). The secondary endpoints included treatment safety, progression-free survival (PFS) and overall survival (OS), and the exploratory analyses of the correlation between PD-L1 expression in tumor tissues, tumor-associated macrophages (TAM) phenotype in tumor microenvironment and efficacy. Results: From June 2020 to June 2023, 12 patients were enrolled and 9 patients had evaluable efficacy with the median age of 34 years, 3 males and 6 females, all patients had large mediastinal mass at initial diagnosis. 7 patients had PD-L1 expression (VENTANA SP263) above 80% and 2 cases could not be further tested due to insufficient tissue specimens. The ORR was 100%, and the CR rate was 77.8% (7/9) after 6 cycles of treatment. The 5 th and 9 th patient reached PR after 6 cycles of treatment due to irregular hospitalization. And CR was achieved after 2 cycles of regular treatment for the 5 th patient. NGS from formalin-fixed paraffin-embedded (FFPE) and circulating tumor DNA (ctDNA) evaluation from blood were performed across all patients before treatment. 5 patients underwent end of treatment-ctDNA test. Median follow-up 15m (6.8m-26.3m), the third patient was lost to follow-up at 9m. The other patients who achieved CR are still at complete remission. Moreover, we found SOCS1, TNFAIP3 are the most frequently mutated genes in biopsies of PMBCL and only the 5th patient had RHOA mutation which is highly related to PMBCL. The PET-CT and ctDNA assessments were negative in three patients at the end of 6 cycles with 60% concordance, and the 5 th and 9 th patient achieved PR on PET-CT, but the ctDNA assessments were negative. The most common adverse events (AEs) were gastrointestinal reactions, 2 patients experienced grade IV myelosuppression and 1 patient had grade I hyperthyroidism. No treatment-related deaths occurred. Conclusion: Tislelizumab combined with R-CHOP for the treatment of previously untreated PMBCL had good efficacy and sustained response with low toxicity. Longer follow-up is required to access the survival benefit of this regimen. Figure 1: Disease Remission in the Included Patients

EXTH-24. FC-ENHANCED ANTI-CTLA-4 IMMUNE CHECKPOINT BLOCKADE AND ITS COMBINATION WITH ANTI-PD-1 WITH CONCOMITANT DOXORUBICIN AND ULTRASOUND-MEDIATED BBB OPENING: A NOVEL IMMUNOTHERAPY FOR GLIOBLASTOMA

Abstract Despite the recent success of immune checkpoint blockade in various cancer types, glioblastoma (GBM) remains resistant to immunotherapy due to its immunosuppressive features and the poor penetration of systemic agents across the blood-brain barrier (BBB). Recent clinical trials demonstrated the unprecedented efficacy of Fc enhanced anti-CTLA-4, an anti-CTLA-4 antibody with enhanced affinity to Fcγ receptors (FcE-aCTLA-4), against immunologically inactive (‘cold’) tumors. This agent exhibits a high affinity for FcγRIIIA regardless of its polymorphic variants of FcgRIIIA that are known to influence the binding affinity and efficacy of conventional anti-CTLA-4 antibodies. We observed robust expression of FcγRIIIA in tumor-associated macrophages/myeloid cells (TAM) of human GBM, which was most pronounced in newly diagnosed GBM. FcE-aCTLA-4 demonstrated high-affinity binding to FcγRIV, the mouse ortholog of human FcγRIIIA, which was highly expressed on TAMs in mouse gliomas. We evaluated the efficacy of the murine homologous FcE-aCTLA-4 antibody as monotherapy and in combination with other treatments in several murine glioma models. FcE-aCTLA-4 selectively depleted CTLA-4 expressing intra-tumoral regulatory T cells (Tregs) via antibody-dependent phagocytosis by TAMs while spearing peripheral Tregs and other CD4+ T cell populations. In a cohort of 4 GBM patients, doxorubicin delivered with low-intensity pulsed ultrasound and microbubbles (LIPU/MB), a procedure that temporarily opens the BBB, upregulated FcγRIIIA expression on TAMs. Treatment of immunotherapy-resistant murine gliomas with a combination of FcE-aCTLA-4, anti-PD-1, and doxorubicin with concomitant LIPU/MB resulted in over 90% cure rates, which correlated with increased infiltration of activated CD8+ T cells in the brain, and complete rejection upon subsequent tumor rechallenge. Our findings indicate that FcE-aCTLA-4 exhibits a novel immunomodulatory function in GBM, and its therapeutic potential is significantly improved when combined with anti-PD-1, doxorubicin, and delivered by LIPU/MB. This therapy warrants further evaluation in clinical trials.

Fc-mediated functions of nirsevimab complement direct respiratory syncytial virus neutralization but are not required for optimal prophylactic protection.

Nirsevimab is an extended half-life (M252Y/S254T/T256E [YTE]-modified) monoclonal antibody to the pre-fusion conformation of the respiratory syncytial virus (RSV) Fusion protein, with established efficacy in preventing RSV-associated lower respiratory tract infection in infants for the duration of a typical RSV season. Previous studies suggest that nirsevimab confers protection via direct virus neutralization. Here we use preclinical models to explore whether fragment crystallizable (Fc)-mediated effector functions contribute to nirsevimab-mediated protection. Nirsevimab, MEDI8897* (i.e., nirsevimab without the YTE modification), and MEDI8897*-TM (i.e., MEDI8897* without Fc effector functions) binding to Fc γ receptors (FcγRs) was evaluated using surface plasmon resonance. Antibody-dependent neutrophil phagocytosis (ADNP), antibody-dependent cellular phagocytosis (ADCP), antibody-dependent complement deposition (ADCD), and antibody-dependent cellular cytotoxicity (ADCC) were assessed through in vitro and ex vivo serological analyses. A cotton rat challenge study was performed with MEDI8897* and MEDI8897*-TM to explore whether Fc effector functions contribute to protection from RSV. Nirsevimab and MEDI8897* exhibited binding to a range of FcγRs, with expected reductions in FcγR binding affinities observed for MEDI8897*-TM. Nirsevimab exhibited in vitro ADNP, ADCP, ADCD, and ADCC activity above background levels, and similar ADNP, ADCP, and ADCD activity to palivizumab. Nirsevimab administration increased ex vivo ADNP, ADCP, and ADCD activity in participant serum from the MELODY study (NCT03979313). However, ADCC levels remained similar between nirsevimab and placebo. MEDI8897* and MEDI8897*-TM exhibited similar dose-dependent reduction in lung and nasal turbinate RSV titers in the cotton rat model. Nirsevimab possesses Fc effector activity comparable with the current standard of care, palivizumab. However, despite possessing the capacity for Fc effector activity, data from RSV challenge experiments illustrate that nirsevimab-mediated protection is primarily dependent on direct virus neutralization.

Exploring the dual role of B cells in solid tumors: implications for head and neck squamous cell carcinoma.

In the tumor milieu of head and neck squamous cell carcinoma (HNSCC), distinct B cell subpopulations are present, which exert either pro- or anti-tumor activities. Multiple factors, including hypoxia, cytokines, interactions with tumor cells, and other immune infiltrating lymphocytes (TILs), alter the equilibrium between the dual roles of B cells leading to cancerogenesis. Certain B cell subsets in the tumor microenvironment (TME) exhibit immunosuppressive function. These cells are known as regulatory B (Breg) cells. Breg cells suppress immune responses by secreting a series of immunosuppressive cytokines, including IL-10, IL-35, TGF-β, granzyme B, and adenosine or dampen effector TILs by intercellular contacts. Multiple Breg phenotypes have been discovered in human and mouse cancer models. However, when compartmentalized within a tertiary lymphoid structure (TLS), B cells predominantly play anti-tumor effects. A mature TLS contains a CD20+ B cell zone with several important types of B cells, including germinal-center like B cells, antibody-secreting plasma cells, and memory B cells. They kill tumor cells via antibody-dependent cytotoxicity and phagocytosis, and local complement activation effects. TLSs are also privileged sites for local T and B cell coordination and activation. Nonetheless, in some cases, TLSs may serve as a niche for hidden tumor cells and indicate a bad prognosis. Thus, TIL-B cells exhibit bidirectional immune-modulatory activity and are responsive to a variety of immunotherapies. In this review, we discuss the functional distinctions between immunosuppressive Breg cells and immunogenic effector B cells that mature within TLSs with the focus on tumors of HNSCC patients. Additionally, we review contemporary immunotherapies that aim to target TIL-B cells. For the development of innovative therapeutic approaches to complement T-cell-based immunotherapy, a full understanding of either effector B cells or Breg cells is necessary.

A Fully Human IgE Specific for CD38 as a Potential Therapy for Multiple Myeloma.

Multiple myeloma (MM) is an incurable malignancy of plasma cells and the second most common hematologic malignancy in the United States. Although antibodies in clinical cancer therapy are generally of the IgG class, antibodies of the IgE class have attractive properties as cancer therapeutics, such as their high affinity for Fc receptors (FcεRs), the low serum levels of endogenous IgE allowing for less competition for FcR occupancy, and the lack of inhibitory FcRs. Importantly, the FcεRs are expressed on immune cells that elicit antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), and/or antigen presentation such as mast cells, eosinophils, macrophages, and dendritic cells. We now report the development of a fully human IgE targeting human CD38 as a potential MM therapy. We targeted CD38 given its high and uniform expression on MM cells. The novel anti-CD38 IgE, expressed in mammalian cells, is properly assembled and secreted, exhibits the correct molecular weight, binds antigen and the high affinity FcεRI, and induces degranulation of FcεRI expressing cells in vitro and also in vivo in transgenic BALB/c mice expressing human FcεRIα. Moreover, the anti-CD38 IgE induces ADCC and ADCP mediated by monocytes/macrophages against human MM cells (MM.1S). Importantly, the anti-CD38 IgE also prolongs survival in a preclinical disseminated xenograft mouse model using SCID-Beige mice and human MM.1S cells when administered with human peripheral blood mononuclear cells (PBMCs) as a source of monocyte effector cells. Our results suggest that anti-CD38 IgE may be effective in humans bearing MM and other malignancies expressing CD38.

IgG antibodies mediated gold nanoparticles conjugated to methotrexate as targeted chemotherapy for lung cancer

Vincamine, a natural chemical, was used as a reducing agent in the synthesis of IgG antibodies mediated biogenic gold nanoparticles (IgGAuNPs). Eventually, the synthesised IgGAuNPs were bioconjugated with the chemotherapeutic drug methotrexate (MTX-IgGAuNPs). The IgG isotype can target cancer cells through polymorphic Fc gamma receptors (FcγRs) and have therapeutic effects. They can restrict cell division by inhibiting different intracellular signal transduction pathways and activating NK cells and macrophages through antibody-dependent cellular cytotoxicity and macrophage-mediated antibody-dependent phagocytosis, respectively. Further, IgGAuNPs and MTX-IgGAuNPs were characterised by physical techniques. Moreover, 3D conformational changes in the structure of IgG were analysed by fluorescence spectroscopy during and after the synthesis of IgGAuNPs. Furthermore, the IgGAuNPs and MTX-IgGAuNPs were effective against lung cancer (A549 cells), while they were found to be non-toxic against normal cells (NRK cells). The effectiveness of IgGAuNPs and MTX-IgGAuNPs was examined by MTT cytotoxicity assay, DCFDA method for the production of ROS, and release of Cyt-c from the mitochondria for caspase-3-mediated apoptosis. Moreover, the confirmation of internalisation of particles into the nucleus was examined under the DAPI assay, and it was found that particles caused nuclear fragmentation, which was also an indication of apoptosis.

Serum concentration of antigen-specific IgG can substantially bias interpretation of antibody-dependent phagocytosis assay readout

Because virus neutralization cannot solely explain vaccine-induced, antibody-mediated protection, antibody effector functions are being considered as a potential correlate of protection (CoP). However, measuring effector functions at a fixed serum dilution for high throughput purposes makes it difficult to distinguish between the effect of serum antibody concentration and antibody properties such as epitopes, subclass, and glycosylation. To address this issue, we evaluated antibody-dependent cellular phagocytosis (ADCP) assay against SARS-CoV-2 spike. Adjustment of serum samples to the same concentration of antigen-specific IgG prior to the ADCP assay revealed concentration-independent differences in ADCP after mRNA vaccination in subjects with and without prior SARS-CoV-2 infection not detectable in assay performed with fixed serum dilution. Phagocytosis measured at different concentrations of spike-specific IgG strongly correlated with the area under the curve (AUC) indicating that ADCP assay can be performed at a standardized antibody concentration for the high throughput necessary for vaccine trial analyses.

Unlocking the Power of Complement-Dependent Cytotoxicity: Engineering Strategies for the Development of Potent Therapeutic Antibodies for Cancer Treatments.

The complement system is a crucial part of the innate immune response, providing defense against invading pathogens and cancer cells. Recently, it has become evident that the complement system plays a significant role in anticancer activities, particularly through complement-dependent cytotoxicity (CDC), alongside antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cell-mediated phagocytosis (ADCP). With the discovery of new roles for serum complement molecules in the human immune system, various approaches are being pursued to develop CDC-enhanced antibody therapeutics. In this review, we focus on successful antibody engineering strategies for enhancing CDC, analyzing the lessons learned and the limitations of each approach. Furthermore, we outline potential pathways for the development of antibody therapeutics specifically aimed at enhancing CDC for superior therapeutic efficacy in the future.

Characterization of epitopes of human monoclonal antibodies against cytomegalovirus glycoprotein B for neutralization and antibody-dependent phagocytosis

As congenital cytomegalovirus (CMV) infections are the leading non-genetic cause of sensorineural hearing loss and significant neurological disabilities in children, the development of CMV vaccines should be given the highest public health priority. Although MF59-adjuvanted glycoprotein B (gB) vaccine (gB/MF59) is safe and immunogenic, its efficacy in terms of protection from natural infection was around 50 % in clinical trials. Although gB/MF59 induced high antibody titers, anti-gB antibodies contributed little to the neutralization of infection. Recent studies have found that non-neutralizing functions, including antibody-dependent phagocytosis of virions and virus-infected cells, are likely to play important roles in pathogenesis and vaccine design. Previously, we isolated human monoclonal antibodies (MAbs) that reacted with the trimeric form of gB ectodomain and found that preferential epitopes for neutralization were present on Domains (Doms) I and II of gB, while there were abundant non-neutralizing antibodies targeting Dom IV. In this study, we analyzed the phagocytosis activities of these MAbs and found the following: 1) MAbs effective for phagocytosis of the virions targeted Doms I and II, 2) the MAbs effective for phagocytosis of the virions and those of virus-infected cells were generally distinct, and 3) the antibody-dependent phagocytosis showed little correlation with neutralizing activities. Taking account of the frequency and levels of neutralization and phagocytosis, incorporation of the epitopes on Doms I and II into developing vaccines is considered desirable for the prevention of viremia.