Development of an antibody cocktail for treatment of Sudan virus infection.

Antibody-based therapies are a promising treatment option for managing ebolavirus infections. Several Ebola virus (EBOV)-specific and, more recently, pan-ebolavirus antibody cocktails have been described. Here, we report the development and assessment of a Sudan virus (SUDV)-specific antibody cocktail. We produced a panel of SUDV glycoprotein (GP)-specific human chimeric monoclonal antibodies (mAbs) using both plant and mammalian expression systems and completed head-to-head in vitro and in vivo evaluations. Neutralizing activity, competitive binding groups, and epitope specificity of SUDV mAbs were defined before assessing protective efficacy of individual mAbs using a mouse model of SUDV infection. Of the mAbs tested, GP base-binding mAbs were more potent neutralizers and more protective than glycan cap- or mucin-like domain-binding mAbs. No significant difference was observed between plant and mammalian mAbs in any of our in vitro or in vivo evaluations. Based on in vitro and rodent testing, a combination of two SUDV-specific mAbs, one base binding (16F6) and one glycan cap binding (X10H2), was down-selected for assessment in a macaque model of SUDV infection. This cocktail, RIID F6-H2, provided protection from SUDV infection in rhesus macaques when administered at 50 mg/kg on days 4 and 6 postinfection. RIID F6-H2 is an effective postexposure SUDV therapy and provides a potential treatment option for managing human SUDV infection.

Rescue of rhesus macaques from the lethality of aerosolized ricin toxin.

Ricin toxin (RT) ranks at the top of the list of bioweapons of concern to civilian and military personnel alike, due to its high potential for morbidity and mortality after inhalation. In nonhuman primates, aerosolized ricin triggers severe acute respiratory distress characterized by perivascular and alveolar edema, neutrophilic infiltration, and severe necrotizing bronchiolitis and alveolitis. There are currently no approved countermeasures for ricin intoxication. Here, we report the therapeutic potential of a humanized mAb against an immunodominant epitope on ricin's enzymatic A chain (RTA). Rhesus macaques that received i.v. huPB10 4 hours after a lethal dose of ricin aerosol exposure survived toxin challenge, whereas control animals succumbed to ricin intoxication within 30 hours. Antibody intervention at 12 hours resulted in the survival of 1 of 5 monkeys. Changes in proinflammatory cytokine, chemokine, and growth factor profiles in bronchial alveolar lavage fluids before and after toxin challenge successfully clustered animals by treatment group and survival, indicating a relationship between local tissue damage and experimental outcome. This study represents the first demonstration, to our knowledge, in nonhuman primates that the lethal effects of inhalational ricin exposure can be negated by a drug candidate, and it opens up a path forward for product development.

Development of a Human Antibody Cocktail that Deploys Multiple Functions to Confer Pan-Ebolavirus Protection.

Passive administration of monoclonal antibodies (mAbs) is a promising therapeutic approach for Ebola virus disease (EVD). However, all mAbs and mAb cocktails that have entered clinical development are specific for a single member of the Ebolavirus genus, Ebola virus (EBOV), and ineffective against outbreak-causing Bundibugyo virus (BDBV) and Sudan virus (SUDV). Here, we advance MBP134, a cocktail of two broadly neutralizing human mAbs, ADI-15878 from an EVD survivor and ADI-23774 from the same survivor but specificity-matured for SUDV GP binding affinity, as a candidate pan-ebolavirus therapeutic. MBP134 potently neutralized all ebolaviruses and demonstrated greater protective efficacy than ADI-15878 alone in EBOV-challenged guinea pigs. A second-generation cocktail, MBP134AF, engineered to effectively harness natural killer (NK) cells afforded additional improvement relative to its precursor in protective efficacy against EBOV and SUDV in guinea pigs. MBP134AF is an optimized mAb cocktail suitable for evaluation as a pan-ebolavirus therapeutic in nonhuman primates.

A Two-Antibody Pan-Ebolavirus Cocktail Confers Broad Therapeutic Protection in Ferrets and Nonhuman Primates.

Recent and ongoing outbreaks of Ebola virus disease (EVD) underscore the unpredictable nature of ebolavirus reemergence and the urgent need for antiviral treatments. Unfortunately, available experimental vaccines and immunotherapeutics are specific for a single member of the Ebolavirus genus, Ebola virus (EBOV), and ineffective against other ebolaviruses associated with EVD, including Sudan virus (SUDV) and Bundibugyo virus (BDBV). Here we show that MBP134AF, a pan-ebolavirus therapeutic comprising two broadly neutralizing human antibodies (bNAbs), affords unprecedented effectiveness and potency as a therapeutic countermeasure to antigenically diverse ebolaviruses. MBP134AF could fully protect ferrets against lethal EBOV, SUDV, and BDBV infection, and a single 25-mg/kg dose was sufficient to protect NHPs against all three viruses. The development of MBP134AF provides a successful model for the rapid discovery and translational advancement of immunotherapeutics targeting emerging infectious diseases.

Therapeutic treatment of Marburg and Ravn virus infection in nonhuman primates with a human monoclonal antibody.

As observed during the 2013-2016 Ebola virus disease epidemic, containment of filovirus outbreaks is challenging and made more difficult by the lack of approved vaccine or therapeutic options. Marburg and Ravn viruses are highly virulent and cause severe and frequently lethal disease in humans. Monoclonal antibodies (mAbs) are a platform technology in wide use for autoimmune and oncology indications. Previously, we described human mAbs that can protect mice from lethal challenge with Marburg virus. We demonstrate that one of these mAbs, MR191-N, can confer a survival benefit of up to 100% to Marburg or Ravn virus-infected rhesus macaques when treatment is initiated up to 5 days post-inoculation. These findings extend the small but growing body of evidence that mAbs can impart therapeutic benefit during advanced stages of disease with highly virulent viruses and could be useful in epidemic settings.

Pharmacokinetics and Preliminary Safety of Pod-Intravaginal Rings Delivering the Monoclonal Antibody VRC01-N for HIV Prophylaxis in a Macaque Model.

The broadly neutralizing antibody (bNAb) VRC01, capable of neutralizing 91% of known human immunodeficiency virus type 1 (HIV-1) isolates in vitro, is a promising candidate microbicide for preventing sexual HIV infection when administered topically to the vagina; however, accessibility to antibody-based prophylactic treatment by target populations in sub-Saharan Africa and other underdeveloped regions may be limited by the high cost of conventionally produced antibodies and the limited capacity to manufacture such antibodies. Intravaginal rings of the pod design (pod-IVRs) delivering Nicotiana-manufactured VRC01 (VRC01-N) over a range of release rates have been developed. The pharmacokinetics and preliminary safety of VRC01-N pod-IVRs were evaluated in a rhesus macaque model. The devices sustained VRC01-N release for up to 21 days at controlled rates, with mean steady-state VRC01-N levels in vaginal fluids in the range of 102 to 103 µg g-1 being correlated with in vitro release rates. No adverse safety indications were observed. These findings indicate that pod-IVRs are promising devices for the delivery of the candidate topical microbicide VRC01-N against HIV-1 infection and merit further preclinical evaluation.

Humanized Monoclonal Antibody That Passively Protects Mice against Systemic and Intranasal Ricin Toxin Challenge.

PB10 is a murine monoclonal antibody against an immunodominant epitope on ricin toxin's enzymatic subunit. Here, we characterize a fully humanized version of PB10 IgG1 (hPB10) and demonstrate that it has potent in vitro and in vivo toxin-neutralizing activities. We also report the minimum serum concentrations of hPB10 required to protect mice against 10 times the 50% lethal dose of ricin when delivered by injection and inhalation.

Monoclonal antibody therapy for Junin virus infection.

Countermeasures against potential biothreat agents remain important to US Homeland Security, and many of these pharmaceuticals could have dual use in the improvement of global public health. Junin virus, the causative agent of Argentine hemorrhagic fever (AHF), is an arenavirus identified as a category A high-priority agent. There are no Food and Drug Administration (FDA) approved drugs available for preventing or treating AHF, and the current treatment option is limited to administration of immune plasma. Whereas immune plasma demonstrates the feasibility of passive immunotherapy, it is limited in quantity, variable in quality, and poses safety risks such as transmission of transfusion-borne diseases. In an effort to develop a monoclonal antibody (mAb)-based alternative to plasma, three previously described neutralizing murine mAbs were expressed as mouse-human chimeric antibodies and evaluated in the guinea pig model of AHF. These mAbs provided 100% protection against lethal challenge when administered 2 d after infection (dpi), and one of them (J199) was capable of providing 100% protection when treatment was initiated 6 dpi and 92% protection when initiated 7 dpi. The efficacy of J199 is superior to that previously described for all other evaluated drugs, and its high potency suggests that mAbs like J199 offer an economical alternative to immune plasma and an effective dual use (bioterrorism/public health) therapeutic.

3B11-N, a monoclonal antibody against MERS-CoV, reduces lung pathology in rhesus monkeys following intratracheal inoculation of MERS-CoV Jordan-n3/2012.

Middle East Respiratory Syndrome Coronavirus (MERS-CoV) was identified in 2012 as the causative agent of a severe, lethal respiratory disease occurring across several countries in the Middle East. To date there have been over 1600 laboratory confirmed cases of MERS-CoV in 26 countries with a case fatality rate of 36%. Given the endemic region, it is possible that MERS-CoV could spread during the annual Hajj pilgrimage, necessitating countermeasure development. In this report, we describe the clinical and radiographic changes of rhesus monkeys following infection with 5×10(6) PFU MERS-CoV Jordan-n3/2012. Two groups of NHPs were treated with either a human anti-MERS monoclonal antibody 3B11-N or E410-N, an anti-HIV antibody. MERS-CoV Jordan-n3/2012 infection resulted in quantifiable changes by computed tomography, but limited other clinical signs of disease. 3B11-N treated subjects developed significantly reduced lung pathology when compared to infected, untreated subjects, indicating that this antibody may be a suitable MERS-CoV treatment.

Plant-based production of two chimeric monoclonal IgG antibodies directed against immunodominant epitopes of Vibrio cholerae lipopolysaccharide.

We have produced and characterized two chimeric human IgG1 monoclonal antibodies that bind different immunodominant epitopes on Vibrio cholerae lipopolysaccharide (LPS). MAb 2D6 IgG1 recognizes Ogawa O-polysaccharide antigen, while mAb ZAC-3 IgG1 recognizes core/lipid A moiety of Ogawa and Inaba LPS. Both antibodies were expressed using a Nicotiana benthamiana-based rapid antibody-manufacturing platform (RAMP) and evaluated in vitro for activities associated with immunity to V. cholerae, including vibriocidal activity, bacterial agglutination and motility arrest.

A tripartite cocktail of chimeric monoclonal antibodies passively protects mice against ricin, staphylococcal enterotoxin B and Clostridium perfringens epsilon toxin.

Due to the fast-acting nature of ricin, staphylococcal enterotoxin B (SEB), and Clostridium perfringens epsilon toxin (ETX), it is necessary that therapeutic interventions following a bioterrorism incident by one of these toxins occur as soon as possible after intoxication. Moreover, because the clinical manifestations of intoxication by these agents are likely to be indistinguishable from each other, especially following aerosol exposure, we have developed a cocktail of chimeric monoclonal antibodies that is capable of neutralizing all three toxins. The efficacy of this cocktail was demonstrated in mouse models of lethal dose toxin challenge.

Reversion of advanced Ebola virus disease in nonhuman primates with ZMapp.

Without an approved vaccine or treatments, Ebola outbreak management has been limited to palliative care and barrier methods to prevent transmission. These approaches, however, have yet to end the 2014 outbreak of Ebola after its prolonged presence in West Africa. Here we show that a combination of monoclonal antibodies (ZMapp), optimized from two previous antibody cocktails, is able to rescue 100% of rhesus macaques when treatment is initiated up to 5 days post-challenge. High fever, viraemia and abnormalities in blood count and blood chemistry were evident in many animals before ZMapp intervention. Advanced disease, as indicated by elevated liver enzymes, mucosal haemorrhages and generalized petechia could be reversed, leading to full recovery. ELISA and neutralizing antibody assays indicate that ZMapp is cross-reactive with the Guinean variant of Ebola. ZMapp exceeds the efficacy of any other therapeutics described so far, and results warrant further development of this cocktail for clinical use.

Glycan variants of a respiratory syncytial virus antibody with enhanced effector function and in vivo efficacy.

Respiratory syncytial virus (RSV) can cause devastating lower respiratory tract infections in preterm infants or when other serious health problems are present. Immunoprophylaxis with palivizumab (Synagis), a humanized IgG1 mAb, is the current standard of care for preventing RSV infection in at-risk neonates. We have explored the contribution of effector function to palivizumab efficacy using a plant-based expression system to produce palivizumab N-glycan structure variants with high homogeneity on different antibody isotypes. We compared these isotype and N-glycoform variants with commercially available palivizumab with respect to both in vitro receptor and C1q binding and in vivo efficacy. Whereas the affinity for antigen and neutralization activity of each variant were indistinguishable from those of palivizumab, their Fcγ receptor binding profiles were very different, which was reflected in either a reduced or enhanced ability to influence the RSV lung titer in challenged cotton rats. Enhanced Fcγ receptor binding was associated with reduced viral lung titers compared with palivizumab, whereas abrogation of receptor binding led to a drastic reduction in efficacy. The results support the hypotheses that classic antibody neutralization is a minor component of efficacy by palivizumab in the cotton rat and that antibody-dependent cell-mediated cytotoxicity activity can significantly enhance the efficacy of this antiviral mAb.

Chimeric plantibody passively protects mice against aerosolized ricin challenge.

Recent incidents in the United States and abroad have heightened concerns about the use of ricin toxin as a bioterrorism agent. In this study, we produced, using a robust plant-based platform, four chimeric toxin-neutralizing monoclonal antibodies that were then evaluated for the ability to passively protect mice from a lethal-dose ricin challenge. The most effective antibody, c-PB10, was further evaluated in mice as a therapeutic following ricin exposure by injection and inhalation.

Therapeutic intervention of Ebola virus infection in rhesus macaques with the MB-003 monoclonal antibody cocktail.

Ebola virus (EBOV) remains one of the most lethal transmissible infections and is responsible for high fatality rates and substantial morbidity during sporadic outbreaks. With increasing human incursions into endemic regions and the reported possibility of airborne transmission, EBOV is a high-priority public health threat for which no preventive or therapeutic options are currently available. Recent studies have demonstrated that cocktails of monoclonal antibodies are effective at preventing morbidity and mortality in nonhuman primates (NHPs) when administered as a post-exposure prophylactic within 1 or 2 days of challenge. To test whether one of these cocktails (MB-003) demonstrates efficacy as a therapeutic (after the onset of symptoms), we challenged NHPs with EBOV and initiated treatment upon confirmation of infection according to a diagnostic protocol for U.S. Food and Drug Administration Emergency Use Authorization and observation of a documented fever. Of the treated animals, 43% survived challenge, whereas both the controls and all historical controls with the same challenge stock succumbed to infection. These results represent successful therapy of EBOV infection in NHPs.

Prophylactic and therapeutic testing of Nicotiana-derived RSV-neutralizing human monoclonal antibodies in the cotton rat model.

Severe lower respiratory tract infection in infants and small children is commonly caused by respiratory syncytial virus (RSV). Palivizumab (Synagis(®)), a humanized IgG1 monoclonal antibody (mAb) approved for RSV immunoprophylaxis in at-risk neonates, is highly effective, but pharmacoeconomic analyses suggest its use may not be cost-effective. Previously described potent RSV neutralizers (human Fab R19 and F2-5; human IgG RF-1 and RF-2) were produced in IgG format in a rapid and inexpensive Nicotiana-based manufacturing system for comparison with palivizumab. Both plant-derived (palivizumab-N) and commercial palivizumab, which is produced in a mouse myeloma cell line, showed protection in prophylactic (p < 0.001 for both mAbs) and therapeutic protocols (p < 0.001 and p < 0.05 respectively). The additional plant-derived human mAbs directed against alternative epitopes displayed neutralizing activity, but conferred less protection in vivo than palivizumab-N or palivizumab. Palivizumab remains one of the most efficacious RSV mAbs described to date. Production in plants may reduce manufacturing costs and improve the pharmacoeconomics of RSV immunoprophylaxis and therapy.

Delayed treatment of Ebola virus infection with plant-derived monoclonal antibodies provides protection in rhesus macaques.

Filovirus infections can cause a severe and often fatal disease in humans and nonhuman primates, including great apes. Here, three anti-Ebola virus mouse/human chimeric mAbs (c13C6, h-13F6, and c6D8) were produced in Chinese hamster ovary and in whole plant (Nicotiana benthamiana) cells. In pilot experiments testing a mixture of the three mAbs (MB-003), we found that MB-003 produced in both manufacturing systems protected rhesus macaques from lethal challenge when administered 1 h postinfection. In a pivotal follow-up experiment, we found significant protection (P < 0.05) when MB-003 treatment began 24 or 48 h postinfection (four of six survived vs. zero of two controls). In all experiments, surviving animals that received MB-003 experienced little to no viremia and had few, if any, of the clinical symptoms observed in the controls. The results represent successful postexposure in vivo efficacy by a mAb mixture and suggest that this immunoprotectant should be further pursued as a postexposure and potential therapeutic for Ebola virus exposure.

Rapid high yield production of different glycoforms of Ebola virus monoclonal antibody.

BACKGROUND: Fc-glycosylation of monoclonal antibodies (mAbs) has profound implications on the Fc-mediated effector functions. Alteration of this glycosylation may affect the efficiency of an antibody. However, difficulties in the production of mAbs with homogeneous N-glycosylation profiles in sufficient amounts hamper investigations of the potential biological impact of different glycan residues. METHODOLOGY/PRINCIPAL FINDINGS: Here we set out to evaluate a transient plant viral based production system for the rapid generation of different glycoforms of a monoclonal antibody. Ebola virus mAb h-13F6 was generated using magnICON expression system in Nicotiana benthamiana, a plant species developed for commercial scale production of therapeutic proteins. h-13F6 was co-expressed with a series of modified mammalian enzymes involved in the processing of complex N-glycans. Using wild type (WT) plants and the glycosylation mutant ΔXTFT that synthesizes human like biantennary N-glycans with terminal N-acetylglucosamine on each branch (GnGn structures) as expression hosts we demonstrate the generation of h-13F6 complex N-glycans with (i) bisected structures, (ii) core α1,6 fucosylation and (iii) ß1,4 galactosylated oligosaccharides. In addition we emphasize the significance of precise sub Golgi localization of enzymes for engineering of IgG Fc-glycosylation. CONCLUSION: The method described here allows the efficient generation of a series of different human-like glycoforms at large homogeneity of virtually any antibody within one week after cDNA delivery to plants. This accelerates follow up functional studies and thus may contribute to study the biological role of N-glycan residues on Fcs and maximizing the clinical efficacy of therapeutic antibodies.

Glycan microarrays for screening sialyltransferase specificities.

Here we demonstrate that glycan microarrays can be used for high-throughput acceptor specificity screening of various recombinant sialyltransferases. Cytidine-5'-monophospho-N-acetylneuraminic acid (CMP-Neu5Ac) was biotinylated at position 9 of N-acetylneuraminic acid (Neu5Ac) by chemoenzymatic synthesis generating CMP-9Biot-Neu5Ac. The activated sugar nucleotide was used as donor substrate for various mammalian sialyltranferases which transferred biotinylated sialic acids simultaneously onto glycan acceptors immobilized onto a microarray glass slide. Biotinylated glycans detected with fluorescein-streptavidin conjugate to generate a specificity profile for each enzyme both confirming previously known specificities and reveal additional specificity information. Human alpha2,6sialyltransferase-I (hST6Gal-I) also sialylates chitobiose structures (GlcNAcbeta1-4GlcNAc)(n) including N-glycans, rat alpha2,3sialyltransferase (rST3Gal-III) tolerates fucosylated acceptors such as Lewis(a), human alpha2,3sialyltransferase-IV (hST3Gal-IV) broadly sialylates oligosaccharides of types 1-4 and porcine alpha2,3sialyltransferase-I (pST3Gal-I) sialylates ganglio-oligosaccharides and core 2 O-glycans in our array system. Several of these sialyltransferases perform a substitution reaction and exchange a sialylated acceptor with a biotinylated sialic acid but are restricted to the most specific acceptor substrates. Thus, this method allows for a rapid generation of enzyme specificity information and can be used towards synthesis of new carbohydrate compounds and expand the glycan array compound library.

Arraying glycomics: a novel bi-functional spacer for one-step microscale derivatization of free reducing glycans.

Glycan array development is limited by the complexity of efficiently generating derivatives of free reducing glycans with primary amines or other functional groups. A novel bi-functional spacer with selective reactivity toward the free glycan and a second functionality, a primary amine, was synthesized. We demonstrated an efficient one-step derivatization of various glycans including naturally isolated N-glycans, O-glycans, milk oligosaccharides, and bacterial polysaccharides in microgram scale. No protecting group manipulations or activation of the anomeric center was required. To demonstrate its utility for glycan microarray fabrication, we compared glycans with different amine-spacers for incorporation onto an amine-reactive glass surface. Our study results revealed that glycans conjugated with this bi-functional linker were effectively printed and detected with various lectins and antibodies.