ADCC-mediating Antibodies Research Articles

CD4 downregulation precedes Env expression and protects HIV-1-infected cells from ADCC mediated by non-neutralizing antibodies.

Antibody-dependent cellular cytotoxicity (ADCC) represents an effective immune response for clearing virally infected cells, making ADCC-mediating antibodies promising therapeutic candidates for HIV-1 cure strategies. Broadly neutralizing antibodies (bNAbs) target epitopes present on the native "closed" envelope glycoprotein (Env), while non-neutralizing antibodies (nnAbs) recognize epitopes exposed upon Env-CD4 interaction. Here, we provide evidence that env mRNA is predominantly expressed by productively infected cells that have already downmodulated cell-surface CD4. This indicates that CD4 downmodulation by HIV-1 precedes Env expression, making productively infected cells resistant to ADCC mediated by nnAbs but sensitive to those mediated by bnAbs. These findings offer critical insights for the development of immunotherapy-based strategies aimed at targeting and eliminating productively infected cells in people living with HIV.

Novel Mouse Model of Recurrent Sublethal Herpes Simplex Virus Infection Recapitulates Human Antibody Responses to Primary and Chronic Infection.

Background: Herpes simplex virus (HSV) vaccine development has been impeded by the absence of predictive preclinical models and defined correlates of immune protection. Prior candidates elicited neutralizing responses greater than natural infection but no antibody-dependent cellular cytotoxicity (ADCC) and failed to protect in clinical trials. Primary HSV infection also elicits only neutralizing responses, but ADCC and an expanded antigenic repertoire emerge over time. This evolution may contribute to the decreased frequency and severity of recurrences. To test this notion, we developed a recurrent HSV infection mouse model and evaluated changes in humoral immunity with repeated challenges. Methods: Mice were repeatedly infected intranasally with clinical isolates of HSV-1 or HSV-2 for four months. HSV binding IgG, neutralizing (with or without complement) and ADCC-mediating antibodies were quantified prior to each round of infection. Viral targets were assessed by western blotting. Pooled immune serum (750 μg IgG per mouse) was passively transferred into naïve wild-type or Hvem knockout mice 24 h prior to lethal skin challenge. Results: Repeated exposure to HSV-1 or HSV-2 induced an increase in total HSV-binding IgG but did not boost neutralizing titers. In contrast, ADCC-mediating responses increased significantly from the first to the fourth viral exposure (p < 0.01). The increase was associated with an expanded antigenic repertoire. Passive transfer of fourth round immune serum provided significant protection whereas first round serum failed to protect (p < 0.01). However, protection was lost when serum was transferred into Hvem knockout mice, which are impaired in mediating ADCC killing. Conclusion: This novel model recapitulates clinical responses, highlights the importance of ADCC in protecting against recurrent infection, and provides a strategy for evaluating therapeutic vaccines.

Greater Durability and Protection against Herpes Simplex Viral Disease following Immunization of Mice with Single-Cycle ΔgD-2 Compared to an Adjuvanted Glycoprotein D Protein Vaccine.

Herpes simplex viruses (HSV) cause chronic infections with significant morbidity. Prior vaccines, designed to generate neutralizing antibodies (nAbs) targeting glycoprotein D (gD), failed to provide durable protection. We adopted a different strategy and evaluated a single-cycle virus deleted in gD (ΔgD-2). ΔgD-2elicits antibodies that primarily mediate antibody-dependent cell mediated cytolysis (ADCC) and provides complete protection against clinical isolates of HSV in multiple lethal mouse models. To assess durability, we vaccinated mice (2 doses administered intramuscularly) with ΔgD-2, adjuvanted recombinant gD-2 (rgD-2/Alum-MPL), or uninfected cells as a control, and quantified antibody responses over one year. Mice (n = 5/group) were lethally challenged at 2, 4, 6, 8, and 10-months post-boost. ΔgD-2-vaccinated mice elicited a durable ADCC-mediating response, which provided complete protection against challenge at all timepoints. In contrast, rgD-2/Alum-MPL elicited only nAbs, which declined significantly within 6 months, provided only partial protection at early timepoints, and no protection after 6 months. Serum sampling after viral challenge showed that infection elicited low levels of ADCC-mediating antibodies in rgD-2/Alum-MPL-vaccinated mice and boosted the nAb response, but only after 6 months. Conversely, infection significantly and consistently boosted both the ADCC and nAbs responses in ΔgD-2-vaccinated mice. Results recapitulate clinical trial outcomes with gD vaccines, highlight the importance of ADCC, and predict that ΔgD-2 will elicit durable responses in humans.

ADCC: An underappreciated correlate of cross-protection against influenza?

In this short review, we summarized the results obtained with an assay to detect influenza virus-specific antibodies that mediate ADCC, which was developed and evaluated within the framework of the IMI-funded project "FLUCOP". HA-specific ADCC mediating antibodies were detected in serum samples from children and adults pre- and post-vaccination with monovalent, trivalent, or quadrivalent seasonal influenza vaccines, or following infection with H1N1pdm09 virus. Additionally, using chimeric influenza HA proteins, the presence of HA-stalk-specific ADCC mediating antibodies after vaccination and natural infection with H1N1pdm09 virus was demonstrated. With serum samples obtained from children that experienced a primary infection with an influenza B virus, we showed that primary infection induces HA-specific ADCC-mediating antibodies that cross-reacted with HA from influenza B viruses from the heterologous lineage. These cross-reactive antibodies were found to be directed to the HA stalk region. Antibodies directed to the influenza B virus HA head mediated low levels of ADCC. Finally, vaccination with a recombinant modified vaccinia virus Ankara expressing the HA gene of a clade 1 A(H5N1) highly pathogenic avian influenza virus led to the induction of ADCC-mediating antibodies, which cross-reacted with H5 viruses of antigenically distinct clades. Taken together, it is clear that virus-specific antibodies induced by infection or vaccination have immunological functionalities in addition to neutralization. These functionalities could contribute to protective immunity. The functional profiling of vaccine-induced antibodies may provide further insight into the effector functions of virus-specific antibodies and their contribution to virus-specific immunity.

HIV-gp140-Specific Antibodies Generated From Indian Long-Term Non-Progressors Mediate Potent ADCC Activity and Effectively Lyse Reactivated HIV Reservoir.

Strategies to reduce the human immunodeficiency virus (HIV) reservoir are urgently required. The antibody-dependent cellular cytotoxicity (ADCC)-mediating anti-HIV antibodies have shown an association with HIV control. We assessed if such antibodies can be generated in vitro and whether the generated antibodies can facilitate the reduction of reactivated HIV reservoir. We isolated HIV-1-gp140-specific memory B cells from HIV-1-infected long-term non-progressors (LTNPs) with or without plasma ADCC and cultured them to generate anti-HIV antibodies. The ability of the generated antibodies to mediate ADCC and facilitate NK cell-mediated lysis of reactivated HIV reservoir was assessed by the rapid fluorometric antibody-dependent cellular cytotoxicity assay and a flow-based novel latency reduction assay, respectively. All LTNPs showed the presence of gp140-specific memory B cells [median: 0.79% (0.54%–1.225%)], which were successfully differentiated into plasma cells [median 72.0% (68.7–82.2%)] in an in-vitro culture and secreted antibodies [median OD: 0.253 (0.205–0.274)]. The HIV-gp140-specific antibodies were generated from 11/13 LTNPs irrespective of their plasma ADCC status. The generated antibodies from LTNPs with plasma ADCC showed higher ADCC potency (median: 37.6%, IQR: 32.95%–51%) and higher reduction in reactivated HIV reservoir (median: 62.5%, IQR: 58.71%–64.92%) as compared with the antibodies generated from LTNPs without plasma ADCC (ADCC: median: 8.85%, IQR: 8%–9.7%; and % p24 reduction median: 13.84, IQR: 9.863%–17.81%). The potency of these antibodies to reduce latent reservoir was two-fold higher than the respective plasma ADCC. The study showed that the potent ADCC-mediating antibodies could be generated from memory B cells of the LTNPs with plasma ADCC activity. These antibodies also showed potent ability to facilitate NK cell-mediated lysis of reactivated HIV reservoirs. It also indicated that memory B cells from individuals with plasma ADCC activity should be preferentially used for such antibody generation. The important role of these antibodies in the reduction of latent reservoirs needs to be further evaluated as a useful strategy to obtain a functional cure for HIV infection.

ADCC-mediating non-neutralizing antibodies can exert immune pressure in early HIV-1 infection.

Despite antibody-dependent cellular cytotoxicity (ADCC) responses being implicated in protection from HIV-1 infection, there is limited evidence that they control virus replication. The high mutability of HIV-1 enables the virus to rapidly adapt, and thus evidence of viral escape is a very sensitive approach to demonstrate the importance of this response. To enable us to deconvolute ADCC escape from neutralizing antibody (nAb) escape, we identified individuals soon after infection with detectable ADCC responses, but no nAb responses. We evaluated the kinetics of ADCC and nAb responses, and viral escape, in five recently HIV-1-infected individuals. In one individual we detected viruses that escaped from ADCC responses but were sensitive to nAbs. In the remaining four participants, we did not find evidence of viral evolution exclusively associated with ADCC-mediating non-neutralizing Abs (nnAbs). However, in all individuals escape from nAbs was rapid, occurred at very low titers, and in three of five cases we found evidence of viral escape before detectable nAb responses. These data show that ADCC-mediating nnAbs can drive immune escape in early infection, but that nAbs were far more effective. This suggests that if ADCC responses have a protective role, their impact is limited after systemic virus dissemination.

A Phase I Trial of the Antibody-Cytokine Fusion Protein F16IL2 in Combination with Anti-CD33 Immunotherapy for Posttransplant AML Relapse

IntroductionNatural killer (NK) cells are key effectors in cancer immunosurveillance and posttransplant immunity, but shortage of environmental growth factors and deficient recognition of malignant cells may limit their anticancer efficacy. We hypothesized that the antibody-mediated anchoring of interleukin-2 (IL-2) to the leukemia-modified extracellular matrix (ECM) would increase NK cell abundance and activity to potentiate antibody-dependent cellular cytotoxicity (ADCC) against acute myeloid leukemia (AML) blasts. In this novel-novel combination dose-escalation phase 1 trial, we enrolled patients with AML relapse after allogeneic hematopoietic stem cell transplantation (HSCT) to evaluate the safety, pharmacokinetics, pharmacodynamics, and preliminary activity of F16IL2, an antibody-cytokine fusion protein composed of the human antibody fragment scFv(F16) in diabody format and two molecules of human IL-2, in combination with the Fc-optimized, ADCC-mediating anti-CD33 monoclonal antibody BI 836858. F16 specifically targets the A1 domain of the ECM protein tenascin C (TnC), which is spliced into the TnC molecule during active angiogenesis and tissue remodeling while it is virtually absent in normal tissues.MethodsF16IL2 (10 - 20 Mio IU IV) was administered on days 1, 8, 15 and 22 of 28-day cycles, followed by administration of BI 836858 (10 - 40 mg IV) two days after each F16IL2 infusion. Dose escalation was performed over 4 dose levels (DL). Cohort 1 (10 Mio IU F16IL2 and 10 mg BI 836858, n = 5), cohort 2 (10 Mio IU F16IL2 and 20 mg BI 836858, n = 3), cohort 3 (20 Mio IU F16IL2 and 20 mg BI 836858, n = 4), cohort 4 (20 Mio IU F16IL2 and 40 mg BI 836858, n = 3). Safety and tolerability, pharmacodynamics and -kinetics, clinical efficacy and immune effector cell dynamics were investigated. This trial was registered at EudraCT as #2015-004763-37.ResultsBetween December 2016 and March 2020, 15 patients with a median age of 50 years (range, 20 - 68) were enrolled and treated across 4 dose levels. Six patients (40%) had received two or more prior HSCT. The most frequent drug-related AEs (F16IL2 or BI 836858 or combination) were pyrexia (n = 13, 87%), chills (n = 12, 80%) and infusion-related reactions (n = 9, 60%), consistent with the expected toxicity profile of cytokine-armed or naked mAbs. These events were generally manageable, transient and of grade ≤ 2. One dose-limiting toxicity occurred at each of DL 3 (pulmonary edema) and 4 (acute GVHD). No patient died within the first 30 days of treatment initiation. Whereas no formal maximum tolerated dose (MTD) was reached, the maximum tested dose of 20 Mio IU F16IL2 and 40 mg BI 836858 was considered the recommended dose (RD). Three objective responses (1 CR, 1 CRi, 1 PR in extramedullary AML) were observed among 7 patients treated at the two higher DL, whereas no responses occurred at the two starting DL. Median OS among all 15 patients was 4.8 months (1.5 - 12.9), with a 6- and 12-month OS of 40% and 27%, respectively. Among those 7 patients whose AML was at least temporarily controlled with study treatment (CR/CRi, PR, SD), 12-month OS was 67% vs. 0% in non-responders. Combination therapy stimulated the expansion and activation of NK cells in bone marrow and peripheral blood.ConclusionsTo the best of our knowledge, this is the first study demonstrating that the strategy of potentiating ADCC with tumor-targeted immunocytokines is feasible in humans. In the difficult-to-treat situation of posttransplant AML relapse, responses were observed at higher DL, even in patients with extramedullary disease. The antibody-mediated targeted delivery of IL-2 to the ECM combined with anti-CD33 immunotherapy represents an innovative experimental approach associated with acceptable safety and encouraging biologic and clinical activity in posttransplant AML relapse. DisclosuresWermke: Novartis, Roche, Pfizer, BMS: Consultancy, Honoraria, Research Funding. Hemmerle: Philogen S.p.A.: Current Employment. Schäfers: Philogen S.p.A.: Research Funding. Rossig: BMS and Celgene: Honoraria; Pfizer: Honoraria; Novartis: Honoraria; AdBoards by Amgen: Honoraria. Stelljes: Pfizer: Consultancy, Research Funding, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Amgen: Consultancy, Speakers Bureau. Rueter: Boehringer Ingelheim Pharma GmbH & Co. KG: Current Employment. Neri: Philogen S.p.A.: Current Employment, Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: Multiple patents on vascular targeting; ETH Zurich: Patents & Royalties: CD117xCD3 TEA. Berdel: Philogen S.p.A.: Consultancy, Current equity holder in publicly-traded company, Honoraria, Membership on an entity's Board of Directors or advisory committees. Schliemann: Roche: Consultancy; Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Astellas: Consultancy; Pfizer: Consultancy; BMS: Consultancy, Other: travel grants; Boehringer-Ingelheim: Research Funding; Novartis: Consultancy; Jazz Pharmaceuticals: Consultancy, Research Funding; AstraZeneca: Consultancy; Abbvie: Consultancy, Other: travel grants.

Improved HIV-positive infant survival is correlated with high levels of HIV-specific ADCC activity in multiple cohorts

SummaryDefining immune responses that protect humans against diverse HIV strains has been elusive. Studying correlates of protection from mother-to-child transmission provides a benchmark for HIV vaccine protection because passively transferred HIV antibodies are present during infant exposure to HIV through breast milk. A previous study by our group illustrated that passively acquired antibody-dependent cellular cytotoxicity (ADCC) activity is associated with improved infant survival whereas neutralization is not. Here, we show, in another cohort and with two effector measures, that passively acquired ADCC antibodies correlate with infant survival. In combined analyses of data from both cohorts, there are highly statistically significant associations between higher infant survival and passively acquired ADCC levels (p = 0.029) as well as dimeric FcγRIIa (p = 0.002) or dimeric FcγRIIIa binding (p < 0.001). These results suggest that natural killer (NK) cell- and monocyte antibody-mediated effector functions may contribute to the observed survival benefit and support a role of pre-existing ADCC-mediating antibodies in clinical outcome.

Frequent Anti-V1V2 Responses Induced by HIV-DNA Followed by HIV-MVA with or without CN54rgp140/GLA-AF in Healthy African Volunteers.

Antibody responses that correlated with reduced risk of HIV acquisition in the RV144 efficacy trial were assessed in healthy African volunteers who had been primed three times with HIV-DNA (subtype A, B, C) and then randomized into two groups; group 1 was boosted twice with HIV-MVA (CRF01_AE) and group 2 with the same HIV-MVA coadministered with subtype C envelope (Env) protein (CN54rgp140/GLA-AF). The fine specificity of plasma Env-specific antibody responses was mapped after the final vaccination using linear peptide microarray technology. Binding IgG antibodies to the V1V2 loop in CRF01_AE and subtype C Env and Env-specific IgA antibodies were determined using enzyme-linked immunosorbent assay. Functional antibody-dependent cellular cytotoxicity (ADCC)-mediating antibody responses were measured using luciferase assay. Mapping of linear epitopes within HIV-1 Env demonstrated strong targeting of the V1V2, V3, and the immunodominant region in gp41 in both groups, with additional recognition of two epitopes located in the C2 and C4 regions in group 2. A high frequency of V1V2-specific binding IgG antibody responses was detected to CRF01_AE (77%) and subtype C antigens (65%). In conclusion, coadministration of CN54rgp140/GLA-AF with HIV-MVA did not increase the frequency, breadth, or magnitude of anti-V1V2 responses or ADCC-mediating antibodies induced by boosting with HIV-MVA alone.

Improved killing of HIV-infected cells using three neutralizing and non-neutralizing antibodies.

The correlation of HIV-specific antibody-dependent cellular cytotoxicity (ADCC) responses with protection from and delayed progression of HIV-1 infection provides a rationale to leverage ADCC-mediating antibodies for treatment purposes. We evaluated ADCC mediated by different combinations of 2 to 6 neutralizing and non-neutralizing anti-HIV-1 Envelope (Env) mAbs, using concentrations ≤ 1 μg/mL, to identify combinations effective at targeting latent reservoir HIV-1 viruses from 10 individuals. We found that within 2 hours, combinations of 3 mAbs mediated more than 30% killing of HIV-infected primary CD4+ T cells in the presence of autologous NK cells, with the combination of A32 (C1C2), DH511.2K3 (MPER), and PGT121 (V3) mAbs being the most effective. Increasing the incubation of target and effector cells in the presence of mAb combinations from 2 to 24 hours resulted in increased specific killing of infected cells, even with neutralization-resistant viruses. The same combination eliminated reactivated latently HIV-1-infected cells in an ex vivo quantitative viral outgrowth assay. Therefore, administration of a combination of 3 mAbs should be considered in planning in vivo studies seeking to eliminate persistently HIV-1-infected cells.

Endocytosis Inhibition in Humans to Improve Responses to ADCC-Mediating Antibodies

A safe and controlled manipulation of endocytosis invivo may have disruptive therapeutic potential. Here, we demonstrate that the anti-emetic/anti-psychotic prochlorperazine can be repurposed to reversibly inhibit the invivo endocytosis of membrane proteins targeted by therapeutic monoclonal antibodies, as directly demonstrated by our human tumor exvivo assay. Temporary endocytosis inhibition results in enhanced target availability and improved efficiency of natural killer cell-mediated antibody-dependent cellular cytotoxicity (ADCC), a mediator of clinical responses induced by IgG1 antibodies, demonstrated here for cetuximab, trastuzumab, and avelumab. Extensive analysis of downstream signaling pathways ruled out on-target toxicities. By overcoming the heterogeneity of drug target availability that frequently characterizes poorly responsive or resistant tumors, clinical application of reversible endocytosis inhibition may considerably improve the clinical benefit of ADCC-mediating therapeutic antibodies.

Optimization of Small Molecules That Sensitize HIV-1 Infected Cells to Antibody-Dependent Cellular Cytotoxicity.

With approximately 37 million people living with HIV worldwide and an estimated 2 million new infections reported each year, the need to derive novel strategies aimed at eradicating HIV-1 infection remains a critical worldwide challenge. One potential strategy would involve eliminating infected cells via antibody-dependent cellular cytotoxicity (ADCC). HIV-1 has evolved sophisticated mechanisms to conceal epitopes located in its envelope glycoprotein (Env) that are recognized by ADCC-mediating antibodies present in sera from HIV-1 infected individuals. Our aim is to circumvent this evasion via the development of small molecules that expose relevant anti-Env epitopes and sensitize HIV-1 infected cells to ADCC. Rapid elaboration of an initial screening hit using parallel synthesis and structure-based optimization has led to the development of potent small molecules that elicit this humoral response. Efforts to increase the ADCC activity of this class of small molecules with the aim of increasing their therapeutic potential was based on our recent cocrystal structures with gp120 core.

Antibody-dependent cellular cytotoxicity targeting CD4-inducible epitopes predicts mortality in HIV-infected infants.

BackgroundAntibody-dependent cellular cytotoxicity (ADCC) has been associated with improved infant outcome in mother-to-child transmission (MTCT) of HIV-1. Epitopes of these ADCC-mediating antibodies remain unidentified. CD4-inducible (CD4i) epitopes on gp120 are common ADCC targets in natural infection and vaccination. We tested whether CD4i epitope-specific ADCC mediated by maternal antibodies or passively-acquired antibodies in infants is associated with reduced MTCT and improved infant survival.MethodsWe used variants of CD4i cluster A-specific antibodies, A32 and C11, and a cluster C-specific antibody, 17b, with mutations abolishing Fc–Fc receptor interactions as inhibitors in a competition rapid and fluorometric ADCC assay using gp120-coated CEM-nkr target cells with plasma from 51 non-transmitting and 21 transmitting breastfeeding mother-infant pairs.FindingsCluster A-specific ADCC was common. Individually, neither A32-like nor C11-like ADCC was statistically significantly associated with risk of MTCT or infected infant survival. In combination, total maternal cluster A-specific ADCC was statistically significantly associated with decreased infected infant survival in a log-rank test (p = 0·017). There was a non-significant association for infant passively-acquired total cluster A-specific ADCC and decreased infected infant survival (p = 0·14). Surprisingly, plasma ADCC was enhanced in the presence of the defective Fc 17b competitor. Defective Fc 17b competitor-mediated maternal ADCC enhancement was statistically significantly associated with reduced infected infant survival (p = 0·011). A non-significant association was observed for passively-acquired infant ADCC enhancement and decreased survival (p = 0·19).InterpretationsThese data suggest that ADCC targeting CD4i epitopes is not associated with protection against breast milk HIV transmission but is associated with decreased survival of infected infants.FundThis study was funded by NIH grant R01AI076105 and NIH fellowship F30AI136636.

Brief Report: The Anti-HIV-1 ADCC-Mediating Antibodies From Cervicovaginal Secretions of HIV-Infected Women Have an Ability to Mediate Lysing of Autologous CD4+ HIV-Infected Cells.

Fragment crystallizable region of antibody-mediated mechanism such as antibody-dependent cellular cytotoxicity (ADCC) has been identified as an important component of immune protection against HIV. We assessed whether the anti-HIV antibodies mediating ADCC from cervicovaginal lavages (CVLs) of HIV-infected women have an ability to mediate lysing of autologous CD4 HIV-infected cells. The CVLs of 62 HIV-infected (37 long-term slow progressors and 25 with progressive HIV infection: progressors) and 20 HIV-uninfected Indian women with high risk of HIV acquisition were tested for the presence of ADCC-mediating anti-HIV antibodies against HIV-1 C Env in a fluorometric assay. Furthermore, we tested the ability of these antibodies to mediate ADCC-dependent killing of the autologous HIV-infected CD4 T cells using paired peripheral blood mononuclear cells containing target and effector cells. The numbers of ADCC responders were significantly higher in long-term slow progressors (34/37) as compared to the progressor group (9/25) with no significant difference in the magnitude. The magnitude of response was inversely associated with detectable CVL viral load (P < 0.003). The lysis of target cells was significantly higher in enriched IgG fraction as compared to the respective non-IgG fraction. The ADCC antibodies from CVLs significantly reduced the frequency of HIV-1 Env-activated autologous CD4 T cells in the presence of autologous effector cells. The presence of ADCC antibodies in CVLs with an ability to mediate lysing of HIV-infected autologous CD4 T cells provides evidence of their promising contribution to mucosal defense against HIV-1 and has implications in designing prophylactic and immunotherapeutic strategies.

Abstract 5621: FAP-4-1BBL: A novel versatile tumor-stroma targeted 4-1BB agonist for combination immunotherapy with checkpoint inhibitors, T-cell bispecific antibodies, and ADCC-mediating antibodies

Abstract For tumor specific co-stimulation via 4-1BB (CD137) a novel tumor-stroma targeted FAP-4-1BB ligand (FAP-4-1BBL) was designed composed of a trimeric split 4-1BBL, a tumor-stroma targeted 4B9 Fab moiety recognizing fibroblast activation protein (FAP) and a heterodimeric Fc-region devoid of FcgR binding but maintained FcRn binding. In presence of a TCR signal 1 either from a T cell receptor MHCI/peptide interaction or through TCR engagement by a T-cell bispecific antibody, FAP-4-1BBL provides co-stimulation to T cells strictly dependent on cross-linking by FAP-expressing fibroblasts. Similarly, FAP-4-1BBL can provide co-stimulation to NK cells with activated FcgRIIIa signaling. FAP-4-1BBL was tested as monotherapy and combined with CEA-TCB, an anti-CEA T-cell bispecific antibody, in the s.c. gastric MKN45 xenograft model co-grafted with NIH-3T3 fibroblasts in human stem cell engrafted (HSC) NSG mice in comparison to DP47-4-1BBL, an analogous untargeted 4-1BBL fusion protein. For use in syngeneic mouse models in immunocompetent mice muFAP-4-1BB, a murine surrogate made of a mu4-1BB agonistic surrogate antibody fused to the variable region of the FAP antibody 4B9, was used. muFAP-4-1BB was tested as monotherapy and combined with a murine specific CEA-TCB surrogate (muCEA-TCB) and the muPD-L1 specific surrogate antibody 6E11 in the s.c. colorectal MC38-CEA model in CEA transgenic (Tg) C57BL/6 mice. For combination with ADCC-mediating antibodies FAP-mu4-1BBL, a hybrid FAP-mu4-1BBL fusion protein, was generated. FAP-mu4-1BBL was tested as monotherapy and combined with the ADCC-mediating anti-HER2 antibody trastuzumab in the s.c. gastric N87 xenograft model in human CD16 Tg Scid mice. In the s.c. gastric MKN45 xenograft model co-grafted with NIH-3T3 fibroblasts in HSC-NSG mice FAP-4-1BBL resulted in combined anti-tumoral efficacy in combination with CEA-TCB, whereas the respective monotherapies as well as the combination with the untargeted DP47-4-1BBL did not improve anti-tumor efficacy. In the syngeneic s.c. MC38-CEA model in CEA Tg C56BL/6 mice, a model with natural FAP expression due to fibroblast infiltration, the muFAP-4-1BB surrogate antibody resulted in combined anti-tumor efficacy, both combined with muCEA-TCB and muPD-L1 antibodies including the induction of tumor remission. Finally, the hybrid FAP-mu4-1BBL surrogate resulted in improved anti-tumor efficacy combined with the ADCC-mediating antibody trastuzumab in the s.c. gastric N87 xenograft model in human CD16 Tg Scid mice. These data show that FAP-4-1BBL is a versatile combination partner for cancer immunotherapy mediating FAP-dependent co-stimulation to T and NK cells in combination with PD-L1 checkpoint inhibition, TCBs and ADCC-mediating antibodies. Clinical evaluation of this novel therapeutic approach is planned early 2018. Citation Format: Johannes Sam, Christina Claus, Claudia Ferrara, Sabine Lang, Valeria Nicolini, Sara Colombetti, Volker Teichgräber, Stefan Evers, Marina Bacac, Pablo Umana, Christian Klein. FAP-4-1BBL: A novel versatile tumor-stroma targeted 4-1BB agonist for combination immunotherapy with checkpoint inhibitors, T-cell bispecific antibodies, and ADCC-mediating antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5621.

Anti-HIV-1 antibody-dependent cellular cytotoxicity: is there more to antibodies than neutralization?

An increasing body of evidence suggests that nonneutralizing Fc effector functions including antibody-dependent cellular cytotoxicity (ADCC) contribute to protection against HIV-1 acquisition. We discuss recent advances in anti-HIV-1 ADCC research with a particular focus on ADCC mediated by Env-specific antibodies in vitro and in vivo, the curative potential of HIV-1-specific ADCC antibodies and the mechanisms of HIV-1 resistance to ADCC. ADCC activities of broadly neutralizing and nonneutralizing monoclonal antibody panels were recently characterized in vitro against several lab-adapted and primary isolates of HIV-1. ADCC activity of these monoclonal antibodies generally correlated with binding to infected cells and were greater against the lab-adapted strains compared with primary HIV-1 isolates. Several recent studies in mouse and macaque models of HIV-1 infection suggest Fc-mediated effector functions contribute to the protective efficacy of broadly neutralizing antibodies and exert immune pressure on HIV-1 in vivo. An increasing body of evidence suggests that ADCC-mediating antibodies, particularly when combined with neutralizing functions, can facilitate prevention and control of HIV-1. The precise mechanisms of partial protection conferred by nonneutralizing antibodies in vivo remain unclear and will need to be fully investigated in order to realize their full potential for HIV-1 vaccines.

Primary Human Influenza B Virus Infection Induces Cross-Lineage Hemagglutinin Stalk-Specific Antibodies Mediating Antibody-Dependent Cellular Cytoxicity.

Influenza A virus (IAV) and influenza B virus (IBV) cause substantial morbidity and mortality during annual epidemics. Two distinct lineages of IBV are distinguished, based on variation in hemagglutinin (HA): B/Victoria/2/87-like (B/Vic) and B/Yamagata/16/88-like (B/Yam). Here, we show that, in humans, primary IBV infection with either lineage induces HA-specific antibody-dependent cellular cytotoxicity (ADCC)-mediating antibodies. IBV infection induced antibodies specific to the HA head and stalk, but only HA stalk-specific antibodies mediated ADCC efficiently and displayed cross-reactivity with IBV of both lineages. This corresponds to recent findings that 2 points of contact between the effector and target cell (ie, HA and sialic acid, respectively, and the fragment crystallizable [Fc] domain and Fcγ receptor IIIα, respectively) are required for efficient ADCC activity and that antibodies specific for the receptor-binding site located in the head domain of HA therefore fail to mediate ADCC. Potentially, ADCC-mediating antibodies directed to the HA stalk of IBV contribute to cross-protective immunity to IBV of both lineages.

Immunization with Clinical HIV-1 Env Proteins Induces Broad Antibody Dependent Cellular Cytotoxicity-Mediating Antibodies in a Rabbit Vaccination Model.

The induction of both neutralizing antibodies and non-neutralizing antibodies with effector functions, for example, antibody-dependent cellular cytotoxicity (ADCC), is desired in the search for effective vaccines against HIV-1. In the pursuit of novel immunogens capable of inducing an efficient antibody response, rabbits were immunized with selected antigens using different prime-boost strategies. We immunized 35 different groups of rabbits with Env antigens from clinical HIV-1 subtypes A and B, including immunization with DNA alone, protein alone, and DNA prime with protein boost. The rabbit sera were screened for ADCC activity using a GranToxiLux-based assay with human peripheral blood mononuclear cells as effector cells and CEM.NKRCCR5 cells coated with HIV-1 envelope as target cells. The groups with the highest ADCC activity were further characterized for cross-reactivity between HIV-1 subtypes. The immunogen inducing the most potent and broadest ADCC response was a trimeric gp140. The ADCC activity was highest against the HIV-1 subtype corresponding to the immunogen. The ADCC activity did not necessarily reflect neutralizing activity in the pseudovirus-TZMbl assay, but there was an overall correlation between the two antiviral activities. We present a rabbit vaccination model and an assay suitable for screening HIV-1 vaccine candidates for the induction of ADCC-mediating antibodies in addition to neutralizing antibodies. The antigens and/or immunization strategies capable of inducing antibodies with ADCC activity did not necessarily induce neutralizing activity and vice versa. Nevertheless, we identified vaccine candidates that were able to concurrently induce both types of responses and that had ADCC activity that was cross-reactive between different subtypes. When searching for an effective vaccine candidate, it is important to evaluate the antibody response using a model and an assay measuring the desired function.

A Replication-Defective Herpes Simplex Virus (HSV)-2 Vaccine, HSV529, is Safe and Well-Tolerated in Adults with or without HSV Infection and Induces Significant HSV-2-Specific Antibody Responses in HSV Seronegative Individuals

BackgroundWe conducted a phase 1, randomized, double-blind, placebo-controlled trial of a replication-defective HSV-2 vaccine, HSV529 (deleted for UL5 and UL29), in 60 healthy adults aged 18 to 40 years.MethodsSubjects were enrolled in groups of 20 from 3 serogroups: HSV1+ or -/HSV2+ (group 1), HSV1+/HSV2– (group 2), and HSV1-/HSV2– (group 3). At months 0, 1, and 6, 15 subjects in each group received HSV529 intramuscularly and 5 subjects received placebo. The primary endpoint was the frequency of solicited injection site and systemic reactions from day 0 to 7 after each vaccination and unsolicited adverse events up to 6 months after the last dose.Results89% of vaccine recipients experienced a mild to moderate solicited injection site reaction vs. 47% of placebo recipients (P = 0.006, 95% CI 0.129, 0.676) that did not preclude additional doses. 64% of vaccine recipients experienced solicited systemic reactions vs. 53% of placebo recipients (P = 0.44, 95% CI -0.179, 0.402). Two serious adverse events occurred in 2 participants and were assessed as unrelated to HSV529 administration. Serum neutralizing antibody titers significantly increased from baseline after 3 doses of HSV529 compared with placebo in group 3 only (P < 0.001). This increase persisted up to 6 months after the third dose of vaccine (P < 0.001). Serum and vaginal antibodies to HSV2 glycoprotein D (gD) also significantly increased after 3 doses of vaccine in group 3 subjects (P < 0.001 and P = 0.012, respectively). The mean vaginal gD titer after 3 doses was about one-third of the mean serum gD titer. In addition, the vaccine induced significant levels of HSV2-specific antibody dependent cellular cytotoxicity (ADCC) after 3 doses in group 3 subjects compared with placebo (P < 0.001). Vaccine-induced CD4 T-cell responses were detected in 46%, 27%, and 36% of subjects in groups 1, 2, and 3, respectively, one month after the third dose of vaccine. CD8 T-cell responses were detected in 8%, 18%, and 14% of subjects in groups 1, 2, and 3, respectively, at the same time point.ConclusionThe HSV529 vaccine was safe, well-tolerated, and immunogenic, eliciting significant neutralizing, gD, and ADCC-mediating antibodies, and modest cellular immune responses in HSV seronegative individuals. NCT01915212Disclosures L. Dropulic, sanofi pasteur: Collaborator, Research support; K. Wang, sanofi pasteur: Collaborator, Research support; M. Oestreich, sanofi pasteur: Collaborator, Research support; H. Pietz, sanofi pasteur: Collaborator, Research support; D. Garabedian, sanofi pasteur: Collaborator, Research support; K. Dowdell, sanofi pasteur: Collaborator, Research support; H. Nguyen, sanofi pasteur: Collaborator, Research support; K. Laing, sanofi pasteur: Research Contractor, payment for conducting T cell assays; D. Koelle, sanofi pasteur: Research Contractor, payment for conducting T cell assays; A. Azose, sanofi pasteur: Research Contractor, Payment for conducting T cell assays; A. Chen, sanofi pasteur: Employee, Salary; L. J. Chang, sanofi pasteur: Employee, Salary; S. Phogat, sanofi pasteur: Employee, Salary

BST-2 Expression Modulates Small CD4-Mimetic Sensitization of HIV-1-Infected Cells to Antibody-Dependent Cellular Cytotoxicity.

Antibodies recognizing conserved CD4-induced (CD4i) epitopes on human immunodeficiency virus type 1 (HIV-1) Env and able to mediate antibody-dependent cellular cytotoxicity (ADCC) have been shown to be present in sera from most HIV-1-infected individuals. These antibodies preferentially recognize Env in its CD4-bound conformation. CD4 downregulation by Nef and Vpu dramatically reduces exposure of CD4i HIV-1 Env epitopes and therefore reduce the susceptibility of HIV-1-infected cells to ADCC mediated by HIV-positive (HIV+) sera. Importantly, this mechanism of immune evasion can be circumvented with small-molecule CD4 mimetics (CD4mc) that are able to transition Env into the CD4-bound conformation and sensitize HIV-1-infected cells to ADCC mediated by HIV+ sera. However, HIV-1 developed additional mechanisms to avoid ADCC, including Vpu-mediated BST-2 antagonism, which decreases the overall amount of Env present at the cell surface. Accordingly, BST-2 upregulation in response to alpha interferon (IFN-α) was shown to increase the susceptibility of HIV-1-infected cells to ADCC despite the activity of Vpu. Here we show that BST-2 upregulation by IFN-β and interleukin-27 (IL-27) also increases the surface expression of Env and thus boosts the ability of CD4mc to sensitize HIV-1-infected cells to ADCC by sera from HIV-1-infected individuals.IMPORTANCE HIV-1 evolved sophisticated strategies to conceal Env epitopes from ADCC-mediating antibodies present in HIV+ sera. Vpu-mediated BST-2 downregulation was shown to decrease ADCC responses by limiting the amount of Env present at the cell surface. This effect of Vpu was shown to be attenuated by IFN-α treatment. Here we show that in addition to IFN-α, IFN-β and IL-27 also affect Vpu-mediated BST-2 downregulation and greatly enhance ADCC responses against HIV-1-infected cells in the presence of CD4mc. These findings may inform strategies aimed at HIV prevention and eradication.