Specific polyclonal F(ab')2 neutralize a large panel of highly pathogenic avian influenza A viruses (H5N1) and control infection in mice

PEGylation Prolongs the Half-Life of Equine Anti-SARS-CoV-2 Specific F(ab')2

Therapeutic antibodies-F(ab')₂ obtained from hyperimmune equine plasma could treat emerging infectious diseases rapidly because of their high neutralization activity and high output. However, the small-sized F(ab')₂ is rapidly eliminated by blood circulation. This study explored PEGylation strategies to maximize the half-life of equine anti-SARS-CoV-2 specific F(ab')₂. Equine anti-SARS-CoV-2 specific F(ab')₂ were combined with 10 KDa MAL-PEG-MAL in optimum conditions. Specifically, there were two strategies: Fab-PEG and Fab-PEG-Fab, F(ab')₂ bind to a PEG or two PEG, respectively. A single ion exchange chromatography step accomplished the purification of the products. Finally, the affinity and neutralizing activity was evaluated by ELISA and pseudovirus neutralization assay, and ELISA detected the pharmacokinetic parameters. The results displayed that equine anti-SARS-CoV-2 specific F(ab')₂ has high specificity. Furthermore, PEGylation F(ab')₂-Fab-PEG-Fab had a longer half-life than specific F(ab')₂. The serum half-life of Fab-PEG-Fab, Fab-PEG, and specific F(ab')₂ were 71.41 h, 26.73 h, and 38.32 h, respectively. The half-life of Fab-PEG-Fab was approximately two times as long as the specific F(ab')₂. Thus far, PEGylated F(ab')₂ has been prepared with high safety, high specificity, and a longer half-life, which could be used as a potential treatment for COVID-19.

Non-clinical safety assessment and in vivo biodistribution of CoviFab, an RBD-specific F(ab')2 fragment derived from equine polyclonal antibodies

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has required the urgent development of new therapies, among which passive immunotherapy is contemplated. CoviFab (INM005) is a RBD-specific F(ab′)2 fragment derived from equine polyclonal antibodies. We investigate their preclinical security and biodistribution by in vivo and ex vivo NIR imaging after intravenous administration of a dose of 4 mg/kg at time 0 and 48 h. Images were taken at 1, 12, 24, 36, 48, 49, 60, 72, 84, 96, 108, 120, 132 and 144 h after the first intravenous injection. At 96 and 144 h, mice were sacrificed for haematology, serum chemistry, clinical pathology, histopathology and ex vivo imaging. The biodistribution profile was similar in all organs studied, with the highest fluorescence at 1 h after each injection, gradually decreasing after that each one and until the end of the study (144 h). The toxicology study revealed no significant changes in the haematology and serum chemistry parameters. Further, there were no changes in the gross and histological examination of organs. Nonclinical data of the current study confirm that CoviFab is safe, without observable adverse effects in mice. Furthermore, we confirm that bioimaging studies are a useful approach in preclinical trials to determine biodistribution.

Prophylactic Efficacy of Equine Immunoglobulin F(ab')2 Fragments Against Feline Parvovirus

Feline parvovirus (FPV), a type of parvovirus prevalent worldwide, can cause foetal death and acute enteritis in adult cats with severe leukopenia, and yet there are no effective drugs to prevent or treat FPV. Here, the immune effects of two FPV vaccines on horses were compared. IgG was extracted from FPV-immunized horse sera. Equine F(ab')2 fragments were obtained from pepsin-digested IgG and then purified by protein-G column chromatography. The results showed that the inactivated FPV oil vaccine was more effective than the inactivated FPV propolis vaccine in helping healthy horses to produce hyper-immune serum. Four methods were tested, among which the optimized octanoic acid-ammonium sulphate precipitation method was proved to be the best process for extracting IgG. The optimal condition for preparing F(ab')2 by pepsin digestion was 30 °C for 3.5 h, and the content, purity and recovery of F(ab')2 were 8.64 mg/mL, 90.36% and 93.24%, respectively. Our equine immunoglobulin F(ab')2 fragments effectively neutralized activity in vitro against FPV, alleviated the clinical symptoms of FPV-infected cats, reduced the viral loads in the intestine and had prophylactic effects in FPV-infected cats. These results indicate that the F(ab')2 fragment prepared from inactivated FPV-immunized horses may be used as a prophylactic agent for diseases caused by FPV.

Donkey-derived anti-CDV IgG, as a passive immunotherapy agent, can effectively increase survival rates of the experimental CDV-infected dogs

BACKGROUND

Humoral immunity plays an important role in the prevention of canine distemper. Anti-CD virus (CDV) antibody has strong antiviral activity and is widely used in the treatment of CD. However, with the increase of CD cases, the availability of therapeutic CD antibody fell short of the clinical needs.

RESULTS

The high-titer antiserum with the high-titer neutralizing activity against CDV was obtained from the donkeys (Dezhou Donkey) immunized with the inactivated CDV vaccine. The donkey anti-CDV IgG was purified from the donkey serum, which was identified to significantly inhibit the CDV replication in the cultured Vero cells and effectively reduce the clinical symptoms and increase the survival rates (75%) of CDV-infected dogs (Shih-tzu Dog), similar to that treated with the dog-derived anti-CDV IgG. These results indicate that donkey-derived IgG is a potential substitute for dog-derived IgG to treat the CD in clinic.

CONCLUSIONS

Administration of donkey-derived anti-CDV IgG can ameliorate clinical symptoms and inhibit virus replication, thereby increasing the survival of CDV-infected dogs. This study opens up a new source of therapeutic antibody for CD treatment.

Polyclonal and monoclonal antibodies for the treatment of influenza

PURPOSE OF REVIEW

This review summarizes past and ongoing efforts for using polyclonal and monoclonal antibodies for the treatment of influenza, and is focused on products that have entered clinical trials.

RECENT FINDINGS

At least three polyclonal and eight monoclonal antibody products have been tested in clinical trials for the treatment of influenza. Considered across the two classes of therapeutics, these products appear to be safe and well tolerated. However, the efficacy results have been mixed and inconclusive. To date, no products have consistently shown superiority to currently available antivirals.

SUMMARY

No products within these two classes have been licensed, and several products appear to have stopped further clinical development. There are several ongoing studies that are anticipated to be completed or reported in the next 1-2 years which will be critical for understanding the value of polyclonal and monoclonal antibodies in the treatment of influenza.

Antibody immunoprophylaxis and immunotherapy for influenza virus infection: Utilization of monoclonal or polyclonal antibodies?

Control programs for emerging influenza are in urgent need of novel therapeutic strategies to mitigate potentially devastating threats from pathogenic strains with pandemic potential. Current vaccines and antivirals have inherent limitations in efficacy, especially with rapid evolutionary changes of influenza viruses. Antibody-based antiviral protection harnesses the natural power of the immune system. Antibodies present prophylactic and therapeutic intervention options for prevention and control of influenza, especially for at-risk populations. Specific monoclonal antibodies are well defined in purity and initial efficacy but polyclonal antibodies are easier to scale-up and cost-effective with long-term efficacy, using batches with broadly neutralizing properties against influenza variants. This review presents the pros and cons of monoclonal versus polyclonal antibody therapy for influenza.

The ongoing evolution of antibody-based treatments for Ebola virus infection

The 2014-2016 Ebola virus outbreak in West Africa was the deadliest in history, prompting the evaluation of various drug candidates, including antibody-based therapeutics for the treatment of Ebola hemorrhagic fever (EHF). Prior to 2014, only convalescent blood products from EHF survivors had been administered to newly infected individuals as a form of treatment. However, during the recent outbreak, monoclonal antibody cocktails such as ZMapp, ZMAb and MB-003 were either tested in a human clinical safety and efficacy trial or provided to some based on compassionate grounds. This review aims to discuss the evolution of antibody-based treatments for EHF, their clinical trial efficacy and the development of new antibody-based therapies currently advancing in preclinical testing.

Immunotherapeutic strategies for sexually transmitted viral infections: HIV, HSV and HPV

More than 1 million sexually transmitted infections (STIs) are acquired each day globally. Etiotropic drugs cannot effectively control infectious diseases therefore, there is a dire need to explore alternative strategies especially those based on the regulation of immune system. The review discusses all rational approaches to develop better understanding towards immunotherapeutic strategies based on modulation of immune system in an attempt to curb the elevating risk of infectious diseases such as HIV, HPV and HSV because of their high prevalence. Development of monoclonal antibodies, vaccines and several other immune based treatments are promising alternative strategies that are offering new opportunities to eradicate pathogens.

Efficacy of a specific polyclonal equine F(ab')2 against avian influenza (H5N1) in ferrets: synergy with oseltamivir

Aim: Current therapies against avian influenza (H5N1) provide limited clinical benefit. FBF-001 is a highly purified equine polyclonal immunoglobulin fragment against H5N1. Methods: Using a ferret model of severe acute H5N1 infection, we assessed FBF-001 when administered on the same day or 1 day after viral challenge, in comparison with oseltamivir therapy. Results: Untreated animals died 2–3 days after challenge. FBF-001 prevented most severe illness and reduced nasal viral load, with best efficacy when administered on the day of viral challenge. Oseltamivir and FBF-001 had synergistic impact on survival. Conclusion: FBF-001 prevented severe consequences of lethal H5N1 challenge in ferrets by controlling viral replication, an effect synergistic to oseltamivir. FBF-001 has recently been granted EMA orphan drug status.

Preserved antiviral adaptive immunity following polyclonal antibody immunotherapy for severe murine influenza infection

Passive immunotherapy may have particular benefits for the treatment of severe influenza infection in at-risk populations, however little is known of the impact of passive immunotherapy on the formation of memory responses to the virus. Ideally, passive immunotherapy should attenuate the severity of infection while still allowing the formation of adaptive responses to confer protection from future exposure. In this study, we sought to determine if administration of influenza-specific ovine polyclonal antibodies could inhibit adaptive immune responses in a murine model of lethal influenza infection. Ovine polyclonal antibodies generated against recombinant PR8 (H1N1) hemagglutinin exhibited potent prophylactic capacity and reduced lethality in an established influenza infection, particularly when administered intranasally. Surviving mice were also protected against reinfection and generated normal antibody and cytotoxic T lymphocyte responses to the virus. The longevity of ovine polyclonal antibodies was explored with a half-life of over two weeks following a single antibody administration. These findings support the development of an ovine passive polyclonal antibody therapy for treatment of severe influenza infection which does not affect the formation of subsequent acquired immunity to the virus.

Benefits of using heterologous polyclonal antibodies and potential applications to new and undertreated infectious pathogens

BACKGROUND

Passive immunotherapy using polyclonal antibodies (immunoglobulins) has been used for over a century in the treatment and post-exposure prophylaxis of various infections and toxins. Heterologous polyclonal antibodies are obtained from animals hyperimmunised with a pathogen or toxin.

AIMS

The aims of this review are to examine the history of animal polyclonal antibody therapy use, their development into safe and effective products and the potential application to humans for emerging and neglected infectious diseases.

METHODS

A literature search of OVID Medline and OVID Embase databases was undertaken to identify articles on the safety, efficacy and ongoing development of polyclonal antibodies. The search contained database-specific MeSH and EMTREE terms in combination with pertinent text-words: polyclonal antibodies and rare/neglected diseases, antivenins, immunoglobulins, serum sickness, anaphylaxis, drug safety, post marketing surveillance, rabies, human influenza, Dengue, West Nile, Nipah, Hendra, Marburg, MERS, Hemorrhagic Fever Virus, and Crimean-Congo. No language limits were applied. The final search was completed on 20.06.2015. Of 1960 articles, title searches excluded many irrelevant articles, yielding 303 articles read in full. Of these, 179 are referenced in this study.

RESULTS

Serum therapy was first used in the 1890s against diphtheria. Early preparation techniques yielded products contaminated with reactogenic animal proteins. The introduction of enzymatic digestion, and purification techniques substantially improved their safety profile. The removal of the Fc fragment of antibodies further reduces hypersensitivity reactions. Clinical studies have demonstrated the efficacy of polyclonal antibodies against various infections, toxins and venoms. Products are being developed against infections for which prophylactic and therapeutic options are currently limited, such as avian influenza, Ebola and other zoonotic viruses.

CONCLUSIONS

Polyclonal antibodies have been successfully applied to rabies, envenomation and intoxication. Polyclonal production provides an exciting opportunity to revolutionise the prognosis of both longstanding neglected tropical diseases as well as emerging infectious threats to humans.

Protection Against H7 Subtype Influenza Virus Infection in Mice by Passive Transfer of Neutralizing Monoclonal Antibody

H7 subtype influenza viruses pose serious threats to both the poultry industry and public health. Recent human infections of avian H7N9 influenza viruses with substantial morbidity and mortality have raised concerns about this virus becoming a potential pandemic pathogen. Neutralizing antibodies have been proven to be highly effective in blocking influenza virus infections. In this study, in order to develop an antibody-based immunoprophylaxis against H7 subtype influenza virus, we first generated a neutralizing monoclonal antibody (MAb) by using a pseudotyped lentiviral vector carrying the hemagglutinin protein of H7 subtype influenza virus. In vitro studies demonstrated that this neutralizing MAb completely inhibited the infection of an H7 subtype influenza virus to cells. The protective efficacy of this MAb was then further tested in a mouse model. It was shown that passive immunization of this MAb protected mice from local virus challenge. Results of the current study lay a foundation for the development of neutralizing MAb-mediated prophylactic strategies to combat human H7 influenza virus infections.

Safety, potential efficacy, and pharmacokinetics of specific polyclonal immunoglobulin F(ab')₂ fragments against avian influenza A (H5N1) in healthy volunteers: a single-centre, randomised, double-blind, placebo-controlled, phase 1 study

BACKGROUND

Human infection with the avian influenza A H5N1 virus results in disease with a high fatality rate, against which antiviral treatments have limited efficacy. We aimed to investigate the safety, pharmacokinetics, and therapeutic potential of specific polyclonal immunoglobulin equine F(ab')₂ fragments raised against influenza A/Vietnam/1194/2004 virus (H5N1 subtype) in healthy volunteers.

METHODS

We did a randomised, double-blind, placebo-controlled, single-centre phase 1 study. In stage 1 (one infusion) and stage 2 (five infusions) of the trial, we randomly assigned healthy male volunteers to receive once-daily intravenous infusions of 0·85 U/kg body weight of F(ab')₂ or once-daily saline placebo. Randomisation was done centrally, with one block of four patients and one block for substitutes (three actives, one placebo) in stage 1, and two blocks of six patients (five actives and one placebo) and the same block for substitutes in stage 2. The primary objective was assessment of the clinical and laboratory safety of F(ab')₂, which was monitored for 22 days in the group that received one dose (assessments on days 0-2, 4, 8, 15, and 22) and 33 days in the group that received five doses (days 0-6, 8, 10, 12, 19, 26, and 33). A final post-study safety assessment was done at 120 days. We also assessed pharmacokinetic outcomes, and assayed haemagglutination and seroneutralisation activity. Analysis was done according to intention-to-treat. This trial is registered with ClinicalTrials.gov, number NCT02295813.

FINDINGS

We enrolled 16 healthy Asian men between Sept 28 and Dec 28, 2012, and randomly assigned 13 to one or five doses of F(ab')₂ and three to placebo. F(ab')₂ was well tolerated, and no deaths or serious adverse events occurred. Three patients had mild adverse events (one each of blepharospasm, sinusitis, and pyrexia). The pyrexia (38°C) was regarded as probably related to the infusion, and resolved after 37 min. Our laboratory assessments of blood and urine samples and physical examinations of heart rate, electrocardiogram readings, and weight showed no clinically significant safety issues. Mean peak plasma concentrations were 19·3 μg/mL (SD 3·5) with the one dose schedule and 23·0 μg/mL (4·5) with the five-dose schedule. F(ab')₂ were still detectable in plasma on average up to 5 days after five doses. Haemagglutination inhibition was only increased after the third dose, but in-vitro seroneutralisation activity was transiently increased after each of the five doses to concentrations regarded as clinically beneficial in infected patients.

INTERPRETATION

F(ab')₂ showed good safety, tolerability, and therapeutic potential for managing of H5N1 exposed patients.

FUNDING

Fab'entech.

Avian influenza: recent epidemiology, travel-related risk, and management

H5N1 influenza continues to smolder in Southeast Asia over the past 5 years, but the emergence of H7N9 in China in 2012 raised concerns for a new avian influenza threat. In contrast with H5N1 with over 650 confirmed cases over 11 years, H7N9 has infected over 450 persons within 2 years. The case fatality rate for H7N9 (35 %) is lower than for H5N1 (60 %) or H10N8 (67 %) but is comparable to that for the Middle East respiratory syndrome coronavirus (MERS CoV), another emerging zoonosis with travel-associated importations. Exposure to poultry and fomites are considered the likely sources of infection for H7N9, H5N1, and H10N8, with limited human-to-human transmission in close contacts. Most cases have occurred in local populations of affected countries, and travel-related risk can be mitigated by avoiding exposure. Vaccines, antivirals, and other therapeutics remain in development stage or of modest benefit for dangerous infections carrying high morbidity and mortality.