Therapy for Argentine hemorrhagic fever in nonhuman primates with a humanized monoclonal antibody.

The COVID-19 pandemic has reemphasized the need to identify safe and scalable therapeutics to slow or reverse symptoms of disease caused by newly emerging and reemerging viral pathogens. Recent clinical successes of monoclonal antibodies (mAbs) in therapy for viral infections demonstrate that mAbs offer a solution for these emerging biothreats. We have explored this with respect to Junin virus (JUNV), an arenavirus classified as a category A high-priority agent and the causative agent of Argentine hemorrhagic fever (AHF). There are currently no Food and Drug Administration-approved drugs available for preventing or treating AHF, although immune plasma from convalescent patients is used routinely to treat active infections. However, immune plasma is severely limited in quantity, highly variable in quality, and poses significant safety risks including the transmission of transfusion-borne diseases. mAbs offer a highly specific and consistently potent alternative to immune plasma that can be manufactured at large scale. We previously described a chimeric mAb, cJ199, that provided protection in a guinea pig model of AHF. To adapt this mAb to a format more suitable for clinical use, we humanized the mAb (hu199) and evaluated it in a cynomolgus monkey model of AHF with two JUNV isolates, Romero and Espindola. While untreated control animals experienced 100% lethality, all animals treated with hu199 at 6 d postinoculation (dpi) survived, and 50% of animals treated at 8 dpi survived. mAbs like hu199 may offer a safer, scalable, and more reproducible alternative to immune plasma for rare viral diseases that have epidemic potential.

Hexavalent sperm-binding IgG antibody released from vaginal film for development of potent on-demand nonhormonal female contraception.

Nonhormonal products for on-demand contraception are a global health technology gap; this unmet need motivated us to pursue the use of sperm-binding monoclonal antibodies to enable effective on-demand contraception. Here, using the cGMP-compliant Nicotiana-expression system, we produced an ultrapotent sperm-binding IgG antibody possessing 6 Fab arms per molecule that bind a well-established contraceptive antigen target, CD52g. We term this hexavalent antibody "Fab-IgG-Fab" (FIF). The Nicotiana-produced FIF had at least 10-fold greater sperm-agglutination potency and kinetics than the parent IgG, while preserving Fc-mediated trapping of individual spermatozoa in mucus. We formulated the Nicotiana-produced FIF into a polyvinyl alcohol-based water-soluble contraceptive film and evaluated its potency in reducing progressively motile sperm in the sheep vagina. Two minutes after vaginal instillation of human semen, no progressively motile sperm were recovered from the vaginas of sheep receiving FIF Film. Our work supports the potential of multivalent contraceptive antibodies to provide safe, effective, on-demand nonhormonal contraception.

Long-term Prophylaxis Against Aerosolized Marburg Virus in Nonhuman Primates With an Afucosylated Monoclonal Antibody.

Marburg virus (MARV) causes a hemorrhagic fever disease in human and nonhuman primates with high levels of morbidity and mortality. Concerns about weaponization of aerosolized MARV have spurred the development of nonhuman primate (NHP) models of aerosol exposure. To address the potential threat of aerosol exposure, a monoclonal antibody that binds MARV glycoprotein was tested, MR186YTE, for its efficacy as a prophylactic. MR186YTE was administered intramuscularly to NHPs at 15 or 5 mg/kg 1 month prior to MARV aerosol challenge. Seventy-five percent (3/4) of the 15 mg/kg dose group and 50% (2/4) of the 5 mg/kg dose group survived. Serum analyses showed that the NHP dosed with 15 mg/kg that succumbed to infection developed an antidrug antibody response and therefore had no detectable MR186YTE at the time of challenge. These results suggest that intramuscular dosing of mAbs may be a clinically useful prophylaxis for MARV aerosol exposure.

ZB-06, a vaginal film containing an engineered human contraceptive antibody (HC4-N), demonstrates safety and efficacy in a phase 1 postcoital test and safety study.

BACKGROUND: With an unplanned pregnancy rate of 50% or more in many countries, there is an urgent need for contraceptives that are more accessible and acceptable. To meet the growing demand for new contraceptives, ZabBio developed ZB-06, a vaginal film containing HC4-N, a human contraceptive antibody that inactivates sperm. OBJECTIVE: This study aimed to assess the potential contraceptive activity of the ZB-06 film using a surrogate assessment for contraceptive efficacy, the postcoital test. We also assessed clinical safety of film use among healthy heterosexual couples. Serum, cervical mucus, and vaginal fluid HC4-N antibody concentrations and sperm agglutination potency were determined after single film use. Changes in the concentration of soluble proinflammatory cytokines and vaginal Nugent score after film use were measured as subclinical safety endpoints. STUDY DESIGN: This was a phase 1, first-in-woman, open-label, proof-of-concept, postcoital test and safety study. RESULTS: A total of 20 healthy women were enrolled in the study, and 8 heterosexual couples completed all study visits. The product was safe for both female participants and their male sexual partners. The postcoital test performed on ovulatory cervical mucus at baseline (no product use) revealed a mean of 25.9 (±30.6) progressively motile sperm per high-power field. After use of a single ZB-06 film before intercourse, this number dropped to 0.04 (±0.06) progressively motile sperm per high-power field (P<.0001). At the follow-up postcoital test visit approximately 1 month later (no product use), a mean of 47.4 (±37.4) progressively motile sperm per high-power field was observed, indicating contraceptive reversibility. CONCLUSION: A single dose of the ZB-06 film applied before intercourse was safe and met efficacy surrogate benchmarks of excluding progressively motile sperm from ovulatory cervical mucus. These data indicate that ZB-06 is a viable contraceptive candidate warranting further development and testing.

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.

Acute Organophosphate Poisoning Case Review With Consideration of Off-Gassing During Postmortem Examination.

ABSTRACT: Although self-harm via ingestion of organophosphorus compounds is relatively common in the developing world, it is rare in the United States. This article reviews the signs and symptoms associated with acute organophosphate poisoning and highlights the effects of organophosphate off-gassing during postmortem examinations to increase awareness of this potentially dangerous workplace exposure.Paramedics responded to a 42-year-old man with pulseless electrical activity. Spontaneous circulation was restored after aggressive resuscitation. Before loss of consciousness, the patient exhibited diaphoresis, vomiting, and diarrhea. Upon admission, the patient had a Glasgow Coma Scale score of 3. Significant laboratory values included a pH of 6.8, p co2 of 72 mm Hg, and lactic acid of 21.8 mmol/L. Electrocardiography suggested inferior ST-elevation myocardial infarction. Electroencephalogram revealed severe cerebral dysfunction. The patient died shortly thereafter.Scene investigation revealed suicidal ideations, which included a snapshot of a bottle containing granular sediment associated with statements that he had imbibed fertilizer. During the postmortem examination, the decedent exuded a petroleum-like odor. In addition, autopsy personnel developed symptoms consistent with organophosphate exposure.A reported history of suspected organophosphate exposure in a decedent should prompt increased safety practices to avoid potential harm to autopsy personnel.

Safety, acceptability, and pharmacokinetics of a monoclonal antibody-based vaginal multipurpose prevention film (MB66): A Phase I randomized trial.

BACKGROUND: MB66 film is a multipurpose prevention technology (MPT) product with monoclonal antibodies (mAbs) against HIV-1 (VRC01-N) and HSV-1 and 2 (HSV8-N). The mAbs were produced by transient expression in Nicotiana benthamiana (N). We conducted a Phase I clinical trial to assess the safety, pharmacokinetics (PK), and ex vivo efficacy of single and repeated doses of MB66 when used intravaginally. METHODS AND FINDINGS: The clinical trial enrolled healthy reproductive-aged, sexually abstinent women. In Segment A, 9 women received a single MB66 film which was inserted into the vaginal posterior fornix by a clinician. In Segment B, 29 women were randomly assigned to MB66 (Active) or Placebo film groups and were instructed to insert 1 film vaginally for 7 consecutive days. Visits and clinical sampling occurred predose and at various time points after single and repeated film doses. The primary endpoint was number of adverse events (AEs) Grade 2 or higher related to product use. Secondary endpoints included film dissolution rate, Nugent score (a Gram stain scoring system to diagnose bacterial vaginosis), vaginal pH, post-use survey results, cytokine concentrations in cervicovaginal lavage (CVL) specimens (assessed by Luminex assay), mAb concentrations in vaginal fluid collected from 4 sites (assessed by ELISA), and HIV and HSV neutralization activity of CVL samples ex vivo (assessed by TZM-bl and plaque reduction assay, respectively). The product was generally safe and well tolerated, with no serious AEs recorded in either segment. The AEs in this study were primarily genitourinary in nature with the most commonly reported AE being asymptomatic microscopic hematuria. There were no differences in vaginal pH or Nugent scores or significant increases in levels of proinflammatory cytokines for up to 7 days after film insertion in either segment or between Active and Placebo groups. Acceptability and willingness to use the product were judged to be high by post-use surveys. Concentrations of VRC01-N and HSV8-N in vaginal secretions were assessed over time to generate pharmacokinetic curves. Antibody levels peaked 1 hour postdosing with Active film (median: 35 µg/mL) and remained significantly elevated at 24 hours post first and seventh film (median: 1.8 µg/mL). Correcting for sample dilution (1:20), VRC01-N concentrations ranged from 36 to 700 µg/mL at the 24-hour time point, greater than 100-fold the IC50 for VRC01 (0.32 µg/mL); HSV8-N concentrations ranged from 80 to 601 µg/mL, well above the IC50 of 0.1 µg/m. CVL samples collected 24 hours after MB66 insertion significantly neutralized both HIV-1 and HSV-2 ex vivo. Study limitations include the small size of the study cohort, and the fact that no samples were collected between 24 hours and 7 days for pharmacokinetic evaluation. CONCLUSIONS: Single and repeated intravaginal applications of MB66 film were safe, well tolerated, and acceptable. Concentrations and ex vivo bioactivity of both mAbs in vaginal secretions were significantly elevated and thus could provide protection for at least 24 hours postdose. However, further research is needed to evaluate the efficacy of MB66 film in women at risk for HIV and HSV infection. Additional antibodies could be added to this platform to provide protection against other sexually transmitted infections (STIs) and contraception. TRIAL REGISTRATION: ClinicalTrials.gov NCT02579083.

Engineering monoclonal antibody-based contraception and multipurpose prevention technologies†.

Sexually transmitted infections are highly prevalent, and over 40% of pregnancies are unplanned. We are producing new antibody-based multipurpose prevention technology products to address these problems and fill an unmet need in female reproductive health. We used a Nicotiana platform to manufacture monoclonal antibodies against two prevalent sexually transmitted pathogens, HIV-1 and HSV-2, and incorporated them into a vaginal film (MB66) for preclinical and Phase 1 clinical testing. These tests are now complete and indicate that MB66 is effective and safe in women. We are now developing an antisperm monoclonal antibody to add contraceptive efficacy to this product. The antisperm antibody, H6-3C4, originally isolated by Shinzo Isojima from the blood of an infertile woman, recognizes a carbohydrate epitope on CD52g, a glycosylphosphatidylinositol-anchored glycoprotein found in abundance on the surface of human sperm. We engineered the antibody for production in Nicotiana; the new antibody which we call "human contraception antibody," effectively agglutinates sperm at concentrations >10 µg/ml and maintains activity under a variety of physiological conditions. We are currently seeking regulatory approval for a Phase 1 clinical trial, which will include safety and "proof of principle" efficacy endpoints. Concurrently, we are working with new antibody production platforms to bring the costs down, innovative antibody designs that may produce more effective second-generation antibodies, and delivery systems to provide extended protection.

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.

Effective Treatment of Staphylococcal Enterotoxin B Aerosol Intoxication in Rhesus Macaques by Using Two Parenterally Administered High-Affinity Monoclonal Antibodies.

Staphylococcal enterotoxin B (SEB) is a protein exotoxin found on the cell surface of Staphylococcus aureus that is the source for multiple pathologies in humans. When purified and concentrated in aerosol form, SEB can cause an acute and often fatal intoxication and thus is considered a biological threat agent. There are currently no vaccines or treatments approved for human use. Studies with rodent models of SEB intoxication show that antibody therapy may be a promising treatment strategy; however, many have used antibodies only prophylactically or well before any clinical signs of intoxication are apparent. We assessed and compared the protective efficacies of two monoclonal antibodies, Ig121 and c19F1, when administered after aerosol exposure in a uniformly lethal nonhuman primate model of SEB intoxication. Rhesus macaques were challenged using small-particle aerosols of SEB and then were infused intravenously with a single dose of either Ig121 or c19F1 (10 mg/kg of body weight) at either 0.5, 2, or 4 h postexposure. Onset of clinical signs and hematological and cytokine response in untreated controls confirmed the acute onset and potency of the toxin used in the challenge. All animals administered either Ig121 or c19F1 survived SEB challenge, whereas the untreated controls succumbed to SEB intoxication 30 to 48 h postexposure. These results represent the successful therapeutic in vivo protection by two investigational drugs against SEB in a severe nonhuman primate disease model and punctuate the therapeutic value of monoclonal antibodies when faced with treatment options for SEB-induced toxicity in a postexposure setting.

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.

ZMapp Reinforces the Airway Mucosal Barrier Against Ebola Virus.

Filoviruses, including Ebola, have the potential to be transmitted via virus-laden droplets deposited onto mucus membranes. Protecting against such emerging pathogens will require understanding how they may transmit at mucosal surfaces and developing strategies to reinforce the airway mucus barrier. Here, we prepared Ebola pseudovirus (with Zaire strain glycoproteins) and used high-resolution multiple-particle tracking to track the motions of hundreds of individual pseudoviruses in fresh and undiluted human airway mucus isolated from extubated endotracheal tubes. We found that Ebola pseudovirus readily penetrates human airway mucus. Addition of ZMapp, a cocktail of Ebola-binding immunoglobulin G antibodies, effectively reduced mobility of Ebola pseudovirus in the same mucus secretions. Topical delivery of ZMapp to the mouse airways also facilitated rapid elimination of Ebola pseudovirus. Our work demonstrates that antibodies can immobilize virions in airway mucus and reduce access to the airway epithelium, highlighting topical delivery of pathogen-specific antibodies to the lungs as a potential prophylactic or therapeutic approach against emerging viruses or biowarfare agents.

Efficacy of Human Monoclonal Antibody Monotherapy Against Bundibugyo Virus Infection in Nonhuman Primates.

Background: The 2013-2016 Ebola virus disease (EVD) epidemics in West Africa highlighted a need for effective therapeutics for treatment of the disease caused by filoviruses. Monoclonal antibodies (mAbs) are promising therapeutic candidates for prophylaxis or treatment of virus infections. Data about efficacy of human mAb monotherapy against filovirus infections in preclinical nonhuman primate models are limited. Methods: Previously, we described a large panel of human mAbs derived from the circulating memory B cells from Bundibugyo virus (BDBV) infection survivors that bind to the surface glycoprotein (GP) of the virus. We tested one of these neutralizing mAbs that recognized the glycan cap of the GP, designated mAb BDBV289, as monotherapy in rhesus macaques. Results: We found that recombinant mAb BDBV289-N could confer up to 100% protection to BDBV-infected rhesus macaques when treatment was initiated as late as 8 days after virus challenge. Protection was associated with survival and decreased viremia levels in the blood of treated animals. Conclusions: These findings define the efficacy of monotherapy of lethal BDBV infection with a glycan cap-specific mAb and identify a candidate mAb therapeutic molecule that could be included in antibody cocktails for prevention or treatment of ebolavirus infections.

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.

Protective mAbs and Cross-Reactive mAbs Raised by Immunization with Engineered Marburg Virus GPs.

The filoviruses, which include the marburg- and ebolaviruses, have caused multiple outbreaks among humans this decade. Antibodies against the filovirus surface glycoprotein (GP) have been shown to provide life-saving therapy in nonhuman primates, but such antibodies are generally virus-specific. Many monoclonal antibodies (mAbs) have been described against Ebola virus. In contrast, relatively few have been described against Marburg virus. Here we present ten mAbs elicited by immunization of mice using recombinant mucin-deleted GPs from different Marburg virus (MARV) strains. Surprisingly, two of the mAbs raised against MARV GP also cross-react with the mucin-deleted GP cores of all tested ebolaviruses (Ebola, Sudan, Bundibugyo, Reston), but these epitopes are masked differently by the mucin-like domains themselves. The most efficacious mAbs in this panel were found to recognize a novel "wing" feature on the GP2 subunit that is unique to Marburg and does not exist in Ebola. Two of these anti-wing antibodies confer 90 and 100% protection, respectively, one hour post-exposure in mice challenged with MARV.

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.

Emerging antibody-based products.

Antibody-based products are not widely available to address many global health challenges due to high costs, limited manufacturing capacity, and long manufacturing lead times. There are now tremendous opportunities to address these industrialization challenges as a result of revolutionary advances in plant virus-based transient expression. This review focuses on some antibody-based products that are in preclinical and clinical development, and have scaled up manufacturing and purification (mg of purified mAb/kg of biomass). Plant virus-based antibody products provide lower upfront cost, shorter time to clinical and market supply, and lower cost of goods (COGs). Further, some plant virus-based mAbs may provide improvements in pharmacokinetics, safety and efficacy.

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.

Strategies for preventing mucosal cell-associated HIV transmission.

Human immunodeficiency virus (HIV) may be transmitted through either cell-free virions or leukocytes harboring intracellular HIV in bodily fluids. In recent years, the early initiation of combination antiretroviral therapy leading to virological suppression has resulted in decreased HIV transmission to uninfected partners. Additionally, the efficacy of primary chemoprophylaxis with oral or topical antiretroviral regimens containing tenofovir (with or without emtricitabine) has been demonstrated. However, the efficacy of these approaches may be compromised by suboptimal adherence, decreased drug concentrations in mucosal compartments in women, and genital inflammation. Furthermore, in vitro studies on the effects of tenofovir on cell-associated HIV transmission have produced conflicting results. Preclinical studies suggest that combination preventive approaches may be most effective in stopping the transmission of HIV after mucosal exposure. Since the development of antibodies were found to correlate with protection in the only effective HIV vaccine trial, the administration of preformed mucosal and systemic antibodies may inform the development of safe and effective antibody-based oral, topical, and/or systemic preexposure prophylaxis agents and provide guidance in the development of HIV vaccines that effectively block cell-associated HIV transmission.

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

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