Preventing infectious disease with passive immunization

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.

Prediction of long-term humoral response induced by the two-dose heterologous Ad26.ZEBOV, MVA-BN-Filo vaccine against Ebola

The persistence of the long-term immune response induced by the heterologous Ad26.ZEBOV, MVA-BN-Filo two-dose vaccination regimen against Ebola has been investigated in several clinical trials. Longitudinal data on IgG-binding antibody concentrations were analyzed from 487 participants enrolled in six Phase I and Phase II clinical trials conducted by the EBOVAC1 and EBOVAC2 consortia. A model based on ordinary differential equations describing the dynamics of antibodies and short- and long-lived antibody-secreting cells (ASCs) was used to model the humoral response from 7 days after the second vaccination to a follow-up period of 2 years. Using a population-based approach, we first assessed the robustness of the model, which was originally estimated based on Phase I data, against all data. Then we assessed the longevity of the humoral response and identified factors that influence these dynamics. We estimated a half-life of the long-lived ASC of at least 15 years and found an influence of geographic region, sex, and age on the humoral response dynamics, with longer antibody persistence in Europeans and women and higher production of antibodies in younger participants.

Bovine colostrum-derived antibodies against SARS-CoV-2 show great potential to serve as prophylactic agents

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to impose a serious burden on health systems globally. Despite worldwide vaccination, social distancing and wearing masks, the spread of the virus is ongoing. One of the mechanisms by which neutralizing antibodies (NAbs) block virus entry into cells encompasses interaction inhibition between the cell surface receptor angiotensin-converting enzyme 2 (ACE2) and the spike (S) protein of SARS-CoV-2. SARS-CoV-2-specific NAb development can be induced in the blood of cattle. Pregnant cows produce NAbs upon immunization, and antibodies move into the colostrum immediately before calving. Here, we immunized cows with SARS-CoV-2 S1 receptor binding domain (RBD) protein in proper adjuvant solutions, followed by one boost with SARS-CoV-2 trimeric S protein and purified immunoglobulins from colostrum. We demonstrate that this preparation indeed blocks the interaction between the trimeric S protein and ACE2 in different in vitro assays. Moreover, we describe the formulation of purified immunoglobulin preparation into a nasal spray. When administered to human subjects, the formulation persisted on the nasal mucosa for at least 4 hours, as determined by a clinical study. Therefore, we are presenting a solution that shows great potential to serve as a prophylactic agent against SARS-CoV-2 infection as an additional measure to vaccination and wearing masks. Moreover, our technology allows for rapid and versatile adaptation for preparing prophylactic treatments against other diseases using the defined characteristics of antibody movement into the colostrum.

Methods to Produce Monoclonal Antibodies for the Prevention and Treatment of Viral Infections

A viral threat can arise suddenly and quickly turn into a major epidemic or pandemic. In such a case, it is necessary to develop effective means of therapy and prevention in a short time. Vaccine development takes decades, and the use of antiviral compounds is often ineffective and unsafe. A quick response may be the use of convalescent plasma, but a number of difficulties associated with it forced researchers to switch to the development of safer and more effective drugs based on monoclonal antibodies (mAbs). In order to provide protection, such drugs must have a key characteristic-neutralizing properties, i.e., the ability to block viral infection. Currently, there are several approaches to produce mAbs in the researchers' toolkit, however, none of them may serve as a gold standard. Each approach has its own advantages and disadvantages. The choice of the method depends both on the characteristics of the virus and on time constraints and technical challenges. This review provides a comparative analysis of modern methods to produce neutralizing mAbs and describes current trends in the design of antibodies for therapy and prevention of viral diseases.

Cross-Strain Neutralizing and Protective Monoclonal Antibodies against EEEV or WEEV

The three encephalitic alphaviruses, namely, the Venezuelan, eastern, and western equine encephalitis viruses (VEEV, EEEV, and WEEV), are classified by the Centers for Disease Control and Prevention (CDC) as biothreat agents. Currently, no licensed medical countermeasures (MCMs) against these viruses are available for humans. Neutralizing antibodies (NAbs) are fast-acting and highly effective MCMs for use in both pre- and post-exposure settings against biothreat agents. While significant work has been done to identify anti-VEEV NAbs, less has been done to identify NAbs against EEEV and WEEV. In order to develop anti-EEEV or -WEEV NAbs, mice were immunized using complementary strategies with a variety of different EEEV or WEEV immunogens to maximize the generation of NAbs to each of these viruses. Of the hybridomas generated, three anti-EEEV and seven anti-WEEV monoclonal antibodies were identified with in vitro neutralization activity. The most potent neutralizers (two anti-EEEV NAbs and three anti-WEEV NAbs) were further evaluated for neutralization activity against additional strains of EEEV, a single strain of Madariaga virus (formerly South American EEEV), or WEEV. Of these, G1-2-H4 and G1-4-C3 neutralized all three EEEV strains and the Madariaga virus strain, whereas G8-2-H9 and 12 WA neutralized six out of eight WEEV strains. To determine the protective efficacy of these NAbs, the five most potent neutralizers were evaluated in respective mouse aerosol challenge models. All five NAbs demonstrated various levels of protection when administered at doses of 2.5 mg/kg or 10 mg/kg 24 h before the respective virus exposure via the aerosol route. Of these, anti-EEEV NAb G1-4-C3 and anti-WEEV NAb 8C2 provided 100% protection at both doses and all surviving mice were free of clinical signs throughout the study. Additionally, no virus was detected in the brain 14 days post virus exposure. Taken together, efficacious NAbs were developed that demonstrate the potential for the development of cross-strain antibody-based MCMs against EEEV and WEEV infections.

Enhancing Immunity with Nanomedicine: Employing Nanoparticles to Harness the Immune System

The failure of immune responses to vaccines and dysfunctional immune responses to viral infection, tumor development, or neoantigens lead to chronic viral infection, tumor progression, or incomplete immune protection after vaccination. Thus, strategies to boost host immunity are a topic of intense research and development. Engineered nanoparticles (NPs) possess immunological properties and can be modified to promote improved local immune responses. Nanoparticle-based approaches have been employed to enhance vaccine efficacy and host immune responses to viral and tumor antigens, with impressive results. In this Perspective, we present an overview of studies, such as the one reported by Alam et al. in this issue of ACS Nano, in which virus-like particles have been employed to enhance immunity. We review the cellular cornerstones of effective immunity and discuss how NPs can harness these interactions to overcome the current obstacles in vaccinology and oncology. We also discuss the barriers to effective NP-mediated immune priming including (1) NP delivery to the site of interest, (2) the quality of response elicited, and (3) the potential of the response to overcome immune escape. Through this Perspective, we aim to highlight the value of nanomedicine not only in delivering therapies but also in coordinating the enhancement of host immune responses. We provide a forward-looking outlook for future NP-based approaches and how they could be tailored to promote this outcome.

Can Immunization of Hens Provide Oral-Based Therapeutics against COVID-19?

In the current worldwide pandemic situation caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and the newest coronavirus disease (COVID-19), therapeutics and prophylactics are urgently needed for a large population. Some of the prophylaxis strategies are based on the development of antibodies targeting viral proteins. IgY antibodies are a type of immunoglobulin present in birds, amphibians, and reptiles. They are usually obtained from egg yolk of hyper-immunized hens and represent a relatively inexpensive source of antibodies. Specific IgY can be produced by immunizing chickens with the target antigen and then purifying from the egg yolk. Chicken IgY has been widely explored as a clinical anti-infective material for prophylaxis, preventive medicine, and therapy of infectious diseases. Administered non-systemically, IgY antibodies are safe and effective drugs. Moreover, passive immunization with avian antibodies could become an effective alternative therapy, as these can be obtained relatively simply, cost-efficiently, and produced on a large scale. Here, we highlight the potential use of polyclonal avian IgY antibodies as an oral prophylactic treatment for respiratory viral diseases, such as COVID-19, for which no vaccine is yet available.

Alzheimer's disease; a review of the pathophysiological basis and therapeutic interventions

Alzheimer's disease (AD) is a neurodegenerative disorder and is identified as the most common cause for dementia. Despite huge global economic burden and the impact on the close family of the patients, there is no definitive cure and thus, improved treatment methods are of need. While memory and cognition are severely affected in AD, exact etiology is yet unknown. The β-Amyloid plaque formation and aggregation hypothesis is among the well-known hypotheses used to explain disease pathogenesis. Currently there are five Food and Drug Administration (FDA) approved drugs as treatment options. All these drugs are used for symptomatic treatment of AD. Thus, disease modifying therapies which can directly address the pathological changes in AD, are needed. Such therapies could be designed based on inhibiting key steps of pathogenesis. Currently there are novel AD drug candidates with various therapeutic mechanisms, undergoing different stages of drug development. Extensive research is being done globally to broaden understanding of the exact mechanisms involved in AD and to develop therapeutic agents that can successfully hinder the occurrence and progression of the disease. In this review, a comprehensive approach to understanding AD and suggestions to be considered in the development of therapeutics for it are presented.

Engineering drug delivery systems to overcome mucosal barriers for immunotherapy and vaccination

Mucosal surfaces protect our bodies from pathogens and external irritants using a system of biological barriers. Overcoming these barriers is a significant drug delivery challenge, particularly for immunotherapies that aim to modulate the local immune response. Reaching local lymphoid tissues and draining lymph nodes (LNs) requires crossing the mucus mesh, mucosal epithelium, and either targeting M cells covering lymphoid tissues or utilizing lymphatic transport that shuttles molecules and particulates from the periphery to the LN. We first highlight the barrier properties of mucus and mucosal epithelium, and the function of the mucosal immune system. We then dive into existing drug delivery technologies that have been engineered to overcome each of these barriers. We particularly focus on novel strategies for targeting lymphoid tissues, which has been shown to enhance immunotherapies and vaccinations, via directly targeting LNs, lymphatic vessels, and M cells that transport samples of mucosal content to the lymphoid tissues.

Separation of immunoglobulin G using aqueous biphasic systems composed of cholinium-based ionic liquids and poly(propylene glycol)

BACKGROUND

The use of antibodies, such as immunoglobulin G (IgG), has faced a significant growth in the past decades for biomedical and research purposes. However, antibodies are high cost biopharmaceuticals, for which the development of alternative and cost-effective purification strategies is still in high demand.

RESULTS

Aqueous biphasic systems (ABS) composed of poly(propylene glycol) (PPG) and cholinium-based ionic liquids (ILs) were investigated for the separation of IgG. The ABS phase diagrams were determined and characterized whenever required. Initial optimization studies with commercial IgG were carried out, followed by the extraction of IgG from rabbit serum. In all ABS, IgG preferentially partitions to the IL-rich phase, unveiling preferential interactions between IgG and ILs. Good results were obtained with commercial IgG, with extraction efficiencies ranging between 93% and 100%, and recovery yields ranging between 20% and 100%. Two of the best and two of the worst identified ABS were then evaluated in what concerns their performance to separate and recover IgG from rabbit serum. With these ABS, extraction efficiencies of 100% and recovery yields > 80% were obtained, indicating an increase in the recovery yield and extraction efficiencies when using real matrices. Under the best conditions studied, IgG with a purity level of 49% was obtained in a single-step. This purity level of IgG is higher than those previously reported using other IL-polymer ABS.

CONCLUSION

IgG preferentially migrates to the IL-rich phase in ABS formed by ILs and polymers, allowing the design of effective separation systems for its recovery from serum samples.

Plasma-Derived Polyreactive Secretory-Like IgA and IgM Opsonizing Salmonella enterica Typhimurium Reduces Invasion and Gut Tissue Inflammation through Agglutination

Due to the increasing emergence of antibiotic-resistant strains of enteropathogenic bacteria, development of alternative treatments to fight against gut infections is a major health issue. While vaccination requires that a proper combination of antigen, adjuvant, and delivery route is defined to elicit protective immunity at mucosae, oral delivery of directly active antibody preparations, referred to as passive immunization, sounds like a valuable alternative. Along the gut, the strategy suffers, however, from the difficulty to obtain sufficient amounts of antibodies with the appropriate specificity and molecular structure for mucosal delivery. Physiologically, at the antibody level, the protection of gastrointestinal mucosal surfaces against enteropathogens is principally mediated by secretory IgA and secretory IgM. We previously demonstrated that purified human plasma-derived IgA and IgM can be associated with secretory component to generate biologically active secretory-like IgA and IgM (SCIgA/M) that can protect epithelial cells from infection by Shigella flexneri in vitro. In this study, we aimed at evaluating the protective potential of these antibody preparations in vivo. We now establish that such polyreactive preparations bind efficiently to Salmonella enterica Typhimurium and trigger bacterial agglutination, as observed by laser scanning confocal microscopy. Upon delivery into a mouse ligated intestinal loop, SCIgA/M-mediated aggregates persist in the intestinal environment and limit the entry of bacteria into intestinal Peyer’s patches via immune exclusion. Moreover, oral administration to mice of immune complexes composed of S. Typhimurium and SCIgA/M reduces mucosal infection, systemic dissemination, and local inflammation. Altogether, our data provide valuable clues for the future appraisal of passive oral administration of polyreactive plasma-derived SCIgA/M to combat infection by a variety of enteropathogens.

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.

Administration of nucleoside-modified mRNA encoding broadly neutralizing antibody protects humanized mice from HIV-1 challenge

Monoclonal antibodies are one of the fastest growing classes of pharmaceutical products, however, their potential is limited by the high cost of development and manufacturing. Here we present a safe and cost-effective platform for in vivo expression of therapeutic antibodies using nucleoside-modified mRNA. To demonstrate feasibility and protective efficacy, nucleoside-modified mRNAs encoding the light and heavy chains of the broadly neutralizing anti-HIV-1 antibody VRC01 are generated and encapsulated into lipid nanoparticles. Systemic administration of 1.4 mg kg⁻¹ of mRNA into mice results in ∼170 μg ml⁻¹ VRC01 antibody concentrations in the plasma 24 h post injection. Weekly injections of 1 mg kg⁻¹ of mRNA into immunodeficient mice maintain trough VRC01 levels above 40 μg ml⁻¹. Most importantly, the translated antibody from a single injection of VRC01 mRNA protects humanized mice from intravenous HIV-1 challenge, demonstrating that nucleoside-modified mRNA represents a viable delivery platform for passive immunotherapy against HIV-1 with expansion to a variety of diseases.

Monoclonal antibodies are highly effective therapeutics that can be delivered as proteins or encoded DNA or mRNA. Here the authors develop lipid nanoparticle-formulated nucleoside-modified mRNA encoding an HIV-1 neutralizing antibody and see sustained and protective antibody levels in treated mice.

Transferência passiva de soro hiperimune anti-Streptococcus agalactiae e seu efeito profilático em tilápias-do-nilo infectadas experimentalmente: sobrevivência e títulos de anticorpos

A bactéria Streptococcus agalactiae é um potente agente causador de surtos por doenças bacterianas em peixes. O estresse provocado pelo manejo zootécnico e pela má qualidade ambiental torna a tilápia susceptível às infecções por essa bactéria. O objetivo do presente trabalho foi avaliar a resistência de tilápias-do-nilo imunizadas com soro hiperimune anti-S. agalactiae, posteriormente desafiadas com cepa homóloga da mesma bactéria. Após determinação da DL 50 de S. agalactiae, 36 tilápias foram distribuídas em quatro aquários, dois para o grupo controle e dois para inoculação celomática para produção de anticorpos anti-S. agalactiae. No 21° e 28° dias, foi coletado sangue para obtenção de soro hiperimune utilizado na transferência passiva. Em seguida, 30 tilápias foram distribuídas em três aquários e submetidas a três tratamentos: GI: controle; GII: imunizadas com o soro inativado; GIII: imunizadas com soro ativo. Após 48 horas e sete, 14, 21, 28 e 35 dias, foram realizadas coletas de sangue para titulação de anticorpos anti-S. agalactiae utilizando-se o teste de aglutinação direta. Para avaliar a taxa de sobrevivência, outras 30 tilápias foram distribuídas em três aquários e submetidas a três tratamentos (GI: controle; GII: imunizadas com soro inativado; GIII: imunizadas com soro ativo). Após 48 horas da imunização, as tilápias foram desafiadas via celomática com 100µL de S. agalactiae e avaliadas duas vezes ao dia, pelo período de 35 dias. Os resultados dos títulos séricos de anticorpos foram detectados pela aglutinação direta até o 21° dia pós-transferência passiva, e, no mesmo período, houve proteção de 80% entre os grupos imunizados com soro inativado e soro ativo contendo anticorpos anti-S. agalactiae. Ao final, os grupos soro inativado e soro ativo apresentaram 60 e 80% de proteção, respectivamente, enquanto no grupo controle 100% dos peixes adoeceram, apresentando sinais graves da infecção, e foram eutanasiados. Não houve diferença estatística significativa na taxa de proteção entre os grupos imunizados.

Antibody therapeutics for Ebola virus disease

With the unprecedented scale of the 2014-2016 West Africa outbreak, the clinical and scientific community scrambled to identify potential therapeutics for Ebola virus disease (EVD). Passive administration of antibodies has a long successful history for prophylaxis and therapy of a variety of infectious diseases, but the importance of antibodies in EVD has been unclear and is the subject of some debate. Recent studies in non-human primates have renewed interest in the potential of antibodies to impact EVD. Currently ongoing clinical evaluation of polyclonal and monoclonal antibody therapy in EVD patients in West Africa may finally offer a definitive answer to this debate.

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.

Novel biocompatible and self-buffering ionic liquids for biopharmaceutical applications

Antibodies obtained from egg yolk of immunized hens, immunoglobulin Y (IgY), are an alternative to the most focused mammal antibodies, because they can be obtained in higher titers by less invasive approaches. However, the production cost of high-quality IgY for large-scale applications remains higher than that of other drug therapies due to the lack of efficient purification methods. The search for new purification platforms is thus vital. The solution could be liquid-liquid extraction by using aqueous biphasic systems (ABS). Herein, we report the extraction and attempted purification of IgY from chicken egg yolk by using a new ABS composed of polymers and Good's buffer ionic liquids (GB-ILs). New self-buffering and biocompatible ILs based on the cholinium cation and anions derived from Good's buffers were synthesized and the self-buffering characteristics and toxicity were characterized. Moreover, when these GB-ILs are combined with PPG 400 (poly(propylene) glycol with a molecular weight of 400 g mol(-1)) to form ABS, extraction efficiencies, of the water-soluble fraction of proteins, ranging between 79 and 94% were achieved in a single step. Based on computational investigations, we also demonstrate that the preferential partitioning of IgY for the GB-IL-rich phase is dominated by hydrogen-bonding and van der Waals interactions.

Prevention and treatment of Clostridium perfringens epsilon toxin intoxication in mice with a neutralizing monoclonal antibody (c4D7) produced in Nicotiana benthamiana

Epsilon toxin (ETX), produced by Clostridium perfringens types B and D, is among the most lethal toxins known. ETX is a potential bioterrorism threat that was listed as a Category B agent by the U.S. Centers for Disease Control until 2012 and it still remains a toxin of interest for several government agencies. We produced a monoclonal antibody (MAb) against ETX (ETX MAb c4D7) in Nicotiana benthamiana and characterized its preventive and therapeutic efficacy in mice. The ETX preparation used was highly lethal for mice (LD50 = 1.6 μg/kg) and resulted in a mean time from inoculation to death of 18 and 180 min when administered intravenously or intraperitoneally, respectively. High lethal challenge resulted in dramatic increases of a variety of pro-inflammatory cytokines in serum, while lower, but still lethal doses, did not elicit such responses. ETX MAb c4D7 was highly effective prophylactically (ED50 = 0.3 mg/kg; ED100 = 0.8 mg/kg) and also provided protection when delivered 15-30 min post-ETX intoxication. These data suggest that ETX MAb c4D7 may have use as a pre- and post-exposure treatment for ETX intoxication.

Active immunity induced by passive IgG post-exposure protection against ricin

Therapeutic antibodies can confer an instant protection against biothreat agents when administered. In this study, intact IgG and F(ab')2 from goat anti-ricin hyperimmune sera were compared for the protection against lethal ricin mediated intoxication. Similar ricin-binding affinities and neutralizing activities in vitro were observed between IgG and F(ab')2 when compared at the same molar concentration. In a murine ricin intoxication model, both IgG and F(ab')2 could rescue 100% of the mice by one dose (3 nmol) administration of antibodies 1 hour after 5 × LD50 ricin challenge. Nine days later, when the rescued mice received a second ricin challenge (5 × LD50), only the IgG-treated mice survived; the F(ab')2-treated mice did not. The experimental design excluded the possibility of residual goat IgG responsible for the protection against the second ricin challenge. Results confirmed that the active immunity against ricin in mice was induced quickly following the passive delivery of a single dose of goat IgG post-exposure. Furthermore, it was demonstrated that the induced active immunity against ricin in mice lasted at least 5 months. Therefore, passive IgG therapy not only provides immediate protection to the victim after ricin exposure, but also elicits an active immunity against ricin that subsequently results in long term protection.

Development of human monoclonal antibodies against diseases caused by emerging and biodefense-related viruses

Polyclonal antibodies have a century-old history of being effective against some viruses; recently, monoclonal antibodies (mAbs) have also shown success. The humanized mAb Synagis (palivizumab), which is still the only mAb against a viral disease approved by the US FDA, has been widely used as a prophylactic measure against respiratory syncytial virus infections in neonates and immunocompromised individuals. The first fully human mAbs against two other paramyxoviruses, Hendra and Nipah virus, which can cause high (up to 75%) mortality, were recently developed; one of them, m101, showed exceptional potency against infectious virus. In an amazing pace of research, several potent human mAbs targeting the severe acute respiratory syndrome coronavirus S glycoprotein that can affect infections in animal models have been developed months after the virus was identified in 2003. A potent humanized mAb with therapeutic potential was recently developed against the West Nile virus. The progress in developing neutralizing human mAbs against Ebola, Crimean-Congo hemorrhagic fever, vaccinia and other emerging and biodefense-related viruses is slow. A major problem in the development of effective therapeutic agents against viruses, including therapeutic antibodies, is the viruses' heterogeneity and mutability. A related problem is the low binding affinity of crossreactive antibodies able to neutralize a variety of primary isolates. Combinations of mAbs or mAbs with other drugs, and/or the identification of potent new mAbs and their derivatives that target highly conserved viral structures, which are critical for virus entry into cells, are some of the possible solutions to these problems, and will continue to be a major focus of antiviral research.

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.

Perspectives on immunoglobulins in colostrum and milk

Immunoglobulins form an important component of the immunological activity found in milk and colostrum. They are central to the immunological link that occurs when the mother transfers passive immunity to the offspring. The mechanism of transfer varies among mammalian species. Cattle provide a readily available immune rich colostrum and milk in large quantities, making those secretions important potential sources of immune products that may benefit humans. Immune milk is a term used to describe a range of products of the bovine mammary gland that have been tested against several human diseases. The use of colostrum or milk as a source of immunoglobulins, whether intended for the neonate of the species producing the secretion or for a different species, can be viewed in the context of the types of immunoglobulins in the secretion, the mechanisms by which the immunoglobulins are secreted, and the mechanisms by which the neonate or adult consuming the milk then gains immunological benefit. The stability of immunoglobulins as they undergo processing in the milk, or undergo digestion in the intestine, is an additional consideration for evaluating the value of milk immunoglobulins. This review summarizes the fundamental knowledge of immunoglobulins found in colostrum, milk, and immune milk.

Synthesis and assembly of a full-length human monoclonal antibody in algal chloroplasts

Monoclonal antibodies can be effective therapeutics against a variety of human diseases, but currently marketed antibody-based drugs are very expensive compared to other therapeutic options. Here, we show that the eukaryotic green algae Chlamydomonas reinhardtii is capable of synthesizing and assembling a full-length IgG1 human monoclonal antibody (mAb) in transgenic chloroplasts. This antibody, 83K7C, is derived from a human IgG1 directed against anthrax protective antigen 83 (PA83), and has been shown to block the effects of anthrax toxin in animal models. Here we show that 83K7C heavy and light chain proteins expressed in the chloroplast accumulate as soluble proteins that assemble into complexes containing two heavy and two light chain proteins. The algal-expressed 83K7C binds PA83 in vitro with similar affinity to the mammalian-expressed 83K7C antibody. In addition, a second human IgG1 and a mouse IgG1 were also expressed and shown to properly assemble in algal chloroplast. These results show that chloroplasts have the ability to fold and assemble full-length human mAbs, and suggest the potential of algae as a platform for the cost effective production of complex human therapeutic proteins.

Wanted, dead or alive: new viral vaccines

Vaccination is one of the most effective methods used for protecting the public against infectious disease. Vaccines can be segregated into two general categories: replicating vaccines (i.e., live, attenuated vaccines) and non-replicating vaccines (e.g., inactivated or subunit vaccines). It has been assumed that live attenuated vaccines are superior to non-replicating vaccines in terms of the quality of the antiviral immune response, the level of protective immunity, and the duration of protective immunity. Although this a prevalent viewpoint within the field, there are several exceptions to the rule. Here, we will explore the historical literature in which some of these conclusions have been based, including "Experiments of Nature" and describe examples of the efficacy of replicating vaccines compared to their non-replicating counterparts. By building a better understanding of how successful vaccines work, we hope to develop better "next-generation" vaccines as well as new vaccines against HIV--a pathogen of global importance for which no licensed vaccine currently exists.

Potent human monoclonal antibodies against SARS CoV, Nipah and Hendra viruses

BACKGROUND

Recently, several potently neutralizing fully human monoclonal antibodies (hmAbs) targeting the severe acute respiratory syndrome-associated coronavirus (SARS CoV) S glycoprotein, and the G glycoprotein of the paramyxoviruses Hendra virus (HeV) and Nipah virus (NiV) have been discovered [corrected].

OBJECTIVE

To examine, compare and contrast the functional characteristics of hmAbs with the potential for prophylaxis and treatment of diseases caused by SARS CoV, HeV and NiV.

METHODS

A review of relevant literature.

RESULTS/CONCLUSIONS

Structural, functional and biochemical analyses [corrected] have provided insights into the molecular mechanisms of receptor recognition and antibody neutralization, and suggested that these antibodies alone or in combination could fight the viruses' heterogeneity and mutability, which is a major problem in the development of effective therapeutic agents against viruses, including therapeutic antibodies.

Progress towards recombinant anti-infective antibodies

The global market for monoclonal antibody therapeutics reached a total of $11.2 billion in 2004, with an impressive 42% growth rate over the previous five years and is expected to reach approximately $34 billion by 2010. Coupled with this growth are stream-lined product development, production scale-up and regulatory approval processes for the highly conserved antibody structure. While only one of the 21 current FDA-approved antibodies, and one of the 38 products in advanced clinical trials target infectious diseases, there is increasing academic, government and commercial interest in this area. Synagis, an antibody neutralizing respiratory syncitial virus (RSV), garnered impressive sales of $1.1 billion in 2006 in spite of its high cost and undocumented effects on viral titres in human patients. The success of anti-RSV passive immunization has motivated the continued development of anti-infectives to treat a number of other infectious diseases, including those mediated by viruses, toxins and bacterial/ fungal cells. Concurrently, advances in antibody technology suggest that cocktails of several monoclonal antibodies with unique epitope specificity or single monoclonal antibodies with broad serotype specificity may be the most successful format. Recent patents and patent applications in these areas will be discussed as predictors of future anti-infective therapeutics.

Adenovirus-mediated delivery of an anti-V antigen monoclonal antibody protects mice against a lethal Yersinia pestis challenge

Pneumonic plague, caused by inhalation of Yersinia pestis, represents a major bioterrorism threat for which no vaccine is available. Based on the knowledge that genetic delivery of monoclonal antibodies (MAbs) with adenovirus (Ad) gene transfer vectors results in rapid, high-level antibody expression, we evaluated the hypothesis that Ad-mediated delivery of a neutralizing antibody directed against the Y. pestis V antigen would protect mice against a Y. pestis challenge. MAbs specific for the Y. pestis V antigen were generated, and the most effective in protecting mice against a lethal intranasal Y. pestis challenge was chosen for further study. The coding sequences for the heavy and light chains were isolated from the corresponding hybridoma and inserted into a replication-defective serotype 5 human Ad gene transfer vector (AdalphaV). Western analysis of AdalphaV-infected cell supernatants demonstrated completely assembled antibodies reactive with V antigen. Following AdalphaV administration to mice, high levels of anti-V antigen antibody titers were detectable as early as 1 day postadministration, peaked by day 3, and remained detectable through a 12-week time course. When animals that received AdalphaV were challenged with Y. pestis at day 4 post-AdalphaV administration, 80% of the animals were protected, while 0% of control animals survived (P < 0.01). Ad-mediated delivery of a V antigen-neutralizing antibody is an effective therapy against plague in experimental animals and could be developed as a rapidly acting antiplague therapeutic.

Therapeutic antibodies: current state and future trends--is a paradigm change coming soon?

Antibody-based therapeutics currently enjoy unprecedented success, growth in research and revenues, and recognition of their potential. It appears that the promise of the "magic bullet" has largely been realized. There are currently 22 monoclonal antibodies (mAbs) approved by the United States Food and Drug Administration (FDA) for clinical use and hundreds are in clinical trials for treatment of various diseases including cancers, immune disorders, and infections. The revenues from the top five therapeutic antibodies (Rituxan, Remicade, Herceptin, Humira, and Avastin) nearly doubled from $6.4 billion in 2004 to $11.7 billion in 2006. During the last several years major pharmaceutical companies raced to acquire antibody companies, with a recent example of MedImmune being purchased for $15.6 billion by AstraZeneca. These therapeutic and business successes reflect the major advances in antibody engineering which have resulted in the generation of safe, specific, high-affinity, and non-immunogenic antibodies during the last three decades. Currently, second and third generations of antibodies are under development, mostly to improve already existing antibody specificities. However, although the refinement of already known methodologies is certainly of great importance for potential clinical use, there are no conceptually new developments in the last decade comparable, for example, to the development of antibody libraries, phage display, domain antibodies (dAbs), and antibody humanization to name a few. A fundamental question is then whether there will be another change in the paradigm of research as happened 1-2 decades ago or the current trend of gradual improvement of already developed methodologies and therapeutic antibodies will continue. Although any prediction could prove incorrect, it appears that conceptually new methodologies are needed to overcome the fundamental problems of drug (antibody) resistance due to genetic or/and epigenetic alterations in cancer and chronic infections, as well as problems related to access to targets and complexity of biological systems. If new methodologies are not developed, it is likely that gradual saturation will occur in the pipeline of conceptually new antibody therapeutics. In this scenario we will witness an increase in combination of targets and antibodies, and further attempts to personalize targeted treatments by using appropriate biomarkers as well as to develop novel scaffolds with properties that are superior to those of the antibodies now in clinical use.

A humanized anti-M2 scFv shows protective in vitro activity against influenza

M2 is one of the most conserved influenza proteins, and has been widely prospected as a potential universal vaccine target, with protection predominantly mediated by antibodies. In this paper we describe the creation of a humanized single chain Fv from 14C2, a potent monoclonal antibody against M2. We show that the humanized scFv demonstrates similar activity to the parental mAb: it is able to recognize M2 in its native context on cell surfaces and is able to show protective in vitro activity against influenza, and so represents a potential lead antibody candidate for universal prophylactic or therapeutic intervention in influenza.

Antibodies as molecular mimics of biomolecules: roles in understanding physiological functions and mechanisms

Physiologists have routinely used understanding of the immune system to generate antibodies against regulatory molecules, growth factors, plasma membrane receptors, and other mammalian molecules in the development of analytical tools and assays. In taking this notion further, antibodies have been used in vivo to modulate physiological systems and to improve our understanding of their molecular interactions. To develop antibodies with physiological activity (efficacy), physiologists have worked with immunologists in developing interdisciplinary insights, requiring basic knowledge of immune system function in designing strategies to generate antibodies that interact with endogenous molecules of physiological interest, in vivo. Antibodies in different physiological systems have been shown to enhance or inhibit endogenous molecular functions. Two approaches have been used: passive and active immunization. Antibodies in these contexts have provided tools to develop further insights into molecular physiological mechanisms. Perhaps surprisingly, enhancing antibodies have been developed against a diverse set of target molecules including several members of the growth hormone/insulin-like growth factor-I axes and those of the beta(2)-adrenoceptor axis. Antibodies that inhibit the actions of somatostatin have also been developed. A further novel approach has been the development of antibodies that interact with adipose cells in vivo. These have the potential to be used in therapeutic antiobesity approaches. Antibodies with efficacy in vivo have provided new insights into molecular physiological mechanisms, enhancing our understanding of these complex processes.

Preparation of recombinant viral glycoproteins for novel and therapeutic antibody discovery

Neutralizing antibodies are a critical component in the protection or recovery from viral infections. In the absence of available vaccines or antiviral drugs for many important human viral pathogens, the identification and characterization of new human monoclonal antibodies (hmAbs) that are able to neutralize viruses offers the possibility for effective pre- and/or post-exposure therapeutic modalities. Such hmAbs may also help in our understanding of the virus entry process, the mechanisms of virus neutralization, and in the eventual development of specific entry inhibitors, vaccines, and research tools. The majority of the more recently developed antiviral hmAbs have come from the use of antibody phage-display technologies using both naïve and immune libraries. Many of these agents are also enveloped viruses possessing important neutralizing determinants within their membrane-anchored envelope glycoproteins, and the use of recombinant, soluble versions of these viral glycoproteins is often critical in the isolation and development of antiviral hmAbs. This chapter will detail several methods that have been successfully employed to produce, purify, and characterize soluble and secreted versions of several viral envelope glycoproteins which have been successfully used as antigens to capture and isolate human phage-displayed monoclonal antibodies.

Antibodies for HIV treatment and prevention: window of opportunity?

Monoclonal antibodies are routinely used as therapeutics in a number of disease settings and have thus also been explored as potential treatment for human immunodeficiency virus (HIV)-1 infection. Antibodies targeting viral antigens, and those directed to the cellular receptors, have been considered for use in prevention and therapy. For virus-targeted antibodies, attention has focused primarily on their neutralizing activity, but such antibodies also have the potential to exert antiviral effects via effector functions, such as antibody-dependent cellular cytotoxicity (ADCC), opsonization, or complement activation. Anti-cell antibodies act through occlusion or down-modulation of the viral receptors with notable impact in vivo, as recent trials have shown. This review summarizes the diverse specificities and modes of action of therapeutic antibodies against HIV-1 infection. Successes, challenges, and future opportunities of harnessing antibodies for therapy of HIV-1 infection are discussed.

Targeted strategies for henipavirus therapeutics

Hendra and Nipah viruses are related emergent paramyxoviruses that infect and cause disease in animals and humans. Disease manifests as a generalized vasculitis affecting multiple organs, but is the most severe in the respiratory and central nervous systems. The high case fatality and person-to-person transmission associated with the most recent NiV outbreaks, and the recent re-emergence of HeV, emphasize the importance and necessity of effective therapeutics for these novel agents. In recent years henipavirus research has revealed a more complete understanding of pathogenesis and, as a consequence, viable approaches towards vaccines and therapeutics have emerged. All strategies target early steps in viral replication including receptor binding and membrane fusion. Animal models have been developed, some of which may prove more valuable than others for evaluating the efficacy of therapeutic agents and regimes. Assessments of protective host immunity and drug pharmacokinetics will be crucial to the further advancement of therapeutic compounds.

Concomitant administration of Yersinia pestis specific monoclonal antibodies with plague vaccine has a detrimental effect on vaccine mediated immunity

Antibodies can be used to confer rapid immunity against infectious agents for short periods of time. By comparison, vaccine induced immunity is more protective, but takes a relatively long time to develop. Concomitant administration of antibody and vaccine by different routes was evaluated as a means of providing both rapid and long-term protection against plague. BALB/c mice were treated intraperitoneally with monoclonal antibodies, with specificities for Yersinia pestis LcrV and F1 antigens. A cohort of these mice was simultaneously vaccinated with rF1 and rLcrV by the intramuscular route. Antibody co-administration with vaccine reduced the level of vaccine mediated protection afforded against a high level Y. pestis challenge. Conversely, antibody-mediated protection was unaffected by vaccine co-administration and lasted for at least 8 weeks post administration. We also evaluated the effect of administering vaccine intradermally and antibody intratracheally and observed that, irrespective of administration route, concomitant administration of antibody reduced the effectiveness of vaccine mediated immunity. The results of passive transfer experiments supported the thesis that the development of protective antibody responses following vaccination is impaired by the presence of circulating monoclonal antibodies with specificities for important B-cell epitopes in the vaccine. We also noted that intradermal injection of LcrV antigen and cholera toxin adjuvant afforded good levels of protection against systemic and aerosol challenge with Y. pestis: intradermal injection might therefore be considered as a potential minimally invasive method of plague vaccine administration. These data have implications for the design of therapeutic strategies against plague infection.

Attempted passive prophylaxis with a monoclonal anti-Burkholderia pseudomallei exopolysaccharide antibody in a murine model of melioidosis

Melioidosis is a severe gram-negative infection caused by the facultative intracellular bacterium Burkholderia pseudomallei, which is responsible for a broad spectrum of symptoms in both humans and animals. No licensed vaccine currently exists. This study evaluated the protective effect of a monoclonal antibody (Mab Ps6F6) specific to B. pseudomallei exopolysaccharide in an outbred murine model of sub-acute melioidosis. When administered before the infectious challenge, Ps6F6 significantly increased resistance to infection and restrained bacterial burden in the spleen over a 30-days period. Patterns of IFN-gamma production were similar in the treated and non treated groups of mice. However, Ps6F6 lowered IFN-gamma levels over the duration of the assay period, except on day 1, suggesting a transient and rapid production of IFN-gamma under Ps6F6 control. Minor but persisting increases occurred in IL-12 levels while TNF-alpha was detected only in the controls at the later stages of infection. No IL-10 secretion was detected in both groups of mice. These data suggest that passive prophylaxis with Mab Ps6F6 provide a moderate and transient induction of inflammatory responses in infected mice but failed to trigger a sterilizing protective immunity.

Administration of antibody to the lung protects mice against pneumonic plague

Intratracheal delivery of aerosolized monoclonal antibodies with specificity for Yersinia pestis LcrV and F1 antigens protected mice in a model of pneumonic plague. These data support the utility of inhaled antibodies as a fast-acting postexposure treatment for plague.

The transmission and control of mastitis in dairy cows: A theoretical approach

A multi-species model that incorporates the transmission of both major and minor mastitis pathogens as well as the interaction between them via coinfection of a quarter is fitted to data from seven dairy herds. The results suggest that major and minor pathogens can interact, on occasion, in a counter-intuitive way with implications for the control of clinical mastitis. The key finding is that delaying culling of cows with major pathogen infections for more than 100 days post infection could result in a higher prevalence of major pathogen infections, whereas early culling would reduce the levels. A theoretical exploration of current and proposed control strategies is carried out, informed by parameters estimated from the model and data. The results at each stage suggest of areas of further research such as: field-testing of the hypotheses presented; the exploration of a stochastic formulation of the model; analysis of the raw repeated measures data; application of control theory to determine the most effective combination of control strategies; inclusion of economic factors into the modelling framework.

Developments towards effective treatments for Nipah and Hendra virus infection

Hendra and Nipah virus are closely related emerging viruses comprising the Henipavirus genus of the subfamily Paramyxovirinae and are distinguished by their ability to cause fatal disease in both animal and human hosts. In particular, the high mortality and person-to-person transmission associated with the most recent Nipah virus outbreaks, as well as the very recent re-emergence of Hendra virus, has confirmed the importance and necessity of developing effective therapeutic interventions. Much research conducted on the henipaviruses over the past several years has focused on virus entry, including the attachment of virus to the host cell, the identification of the virus receptor and the membrane fusion process between the viral and host cell membranes. These findings have led to the development of possible vaccine candidates, as well as potential antiviral therapeutics. The common link among all of the possible antiviral agents discussed here, which have also been developed and tested, is that they target very early stages of the infection process. The establishment and validation of suitable animal models of Henipavirus infection and pathogenesis are also discussed as they will be crucial in the assessment of the effectiveness of any treatments for Hendra and Nipah virus infection.

Combinations of polyclonal or monoclonal antibodies to proteins of the outer membranes of the two infectious forms of vaccinia virus protect mice against a lethal respiratory challenge

Previous studies demonstrated that antibodies to live vaccinia virus infection are needed for optimal protection against orthopoxvirus infection. The present report is the first to compare the protective abilities of individual and combinations of specific polyclonal and monoclonal antibodies that target proteins of the intracellular (IMV) and extracellular (EV) forms of vaccinia virus. The antibodies were directed to one IMV membrane protein, L1, and to two outer EV membrane proteins, A33 and B5. In vitro studies showed that the antibodies to L1 neutralized IMV and that the antibodies to A33 and B5 prevented the spread of EV in liquid medium. Prophylactic administration of individual antibodies to BALB/c mice partially protected them against disease following intranasal challenge with lethal doses of vaccinia virus. Combinations of antibodies, particularly anti-L1 and -A33 or -L1 and -B5, provided enhanced protection when administered 1 day before or 2 days after challenge. Furthermore, the protection was superior to that achieved with pooled immune gamma globulin from human volunteers inoculated with live vaccinia virus. In addition, single injections of anti-L1 plus anti-A33 antibodies greatly delayed the deaths of severe combined immunodeficiency mice challenged with vaccinia virus. These studies suggest that antibodies to two or three viral membrane proteins optimally derived from the outer membranes of IMV and EV, may be beneficial for prophylaxis or therapy of orthopoxvirus infections.

Display and selection of chicken IgA Fab fragments

Passive immune therapy is regaining interest to prevent and cure infectious diseases both in human and veterinary medicine. Therefore, systems are required that enable efficient targeted selection of antibodies originating from virtually any animal species. Here, a system for the selection of chicken IgA, using phage display, is described. A novel phagemid vector (pChick3) for the display and selection of chicken IgA antibodies in Fab format was developed. The functionality of pChick3 was demonstrated by construction of an immune antibody library using B cells from chickens infected with Eimeria acervulina. From this library, 10 different IgA fragments with specific binding to the E. acervulina antigen mix, the sporozoite or oocyst fractions were selected. These results demonstrate the efficiency and versatility of the pChick3 vector system that can readily be applied to construct libraries and subsequently select antibodies of the alpha isotype against a wide variety of pathogens and parasites.

Passive immunization of immune-suppressed animals: Chicken antibodies protect against Ornithobacterium rhinotracheale infection

Unravelling of the protective immunity acquired during a natural infection may contribute to vaccine development. To assess the role of antibody-mediated immunity in protection against Ornithobacterium rhinotracheale infection in chickens, a novel experimental method was applied that combined immune depletion and passive transfer of immunity within the same host. Administration of cyclophosphamide (CY) to broiler chickens successfully suppressed B lymphocyte development, and therefore humoral immunity, as confirmed by histological and serological analysis. Challenge of CY-treated birds with O. rhinotracheale revealed a significantly higher pathology score in comparison to immune-competent birds that received the same bacterial challenge. Measurement of serum immunoglobulin levels of immune-competent birds revealed a positive correlation between IgA and/or IgG production and protection against infection. Passive transfer of O. rhinotracheale-specific antiserum to the immune-suppressed birds prior to pathogen challenge significantly decreased morbidity. This protective effect was not observed after administration of control sera containing similar concentrations of immunoglobulins. Together, these results provide firm evidence that chicken humoral immunity to O. rhinotracheale is a key component in protection against infection. Our data confirm that the applied immune depletion and reconstitution approach is an attractive tool to analyse the nature of the protective immune response.