Properties and therapeutic efficacy of broadly reactive chimeric and humanized H5-specific monoclonal antibodies against H5N1 influenza viruses

Engineering of Organic Solvent-Tolerant Antibody to Sulfonamides by CDR Grafting for Analytical Purposes

The use of organic solvents to extract chemical contaminants for an immunoassay is mostly inevitable. On this occasion, the intolerance of natural antibodies against organic solvent is detrimental to the performance of immunoassays in terms of sensitivity, assay time, accuracy, and precision. Few studies have focused on improving the low tolerance of natural antibodies to organic solvents for analytical purposes. In this study, we engineered the monoclonal antibody (mAb) 4D11 to sulfonamides through CDR grafting by using one proven highly stable humanized antibody (hAb) 4D5 for the first time. The engineered antibody hAb 4D11 showed significantly improved tolerance abilities to acetonitrile (2% to 20%) and methanol (10% to 20%), and retained the highly affinity and class-specificity to sulfonamides. This study provided a general strategy to improve antibody tolerance to organic solvents and was greatly beneficial to the robust development of immunoassays.

A potential therapeutic neutralization monoclonal antibody specifically against multi-coxsackievirus A16 strains challenge

Coxsackievirus A16 (CA16) has caused worldwide epidemics of hand, foot and mouth disease (HFMD), particularly in infants and pre-school children. Currently, there are no vaccines or antiviral drugs available for CA16-associated disease. In this study, a CA16-specific monoclonal antibody (MAb) NA11F12 was derived with an epidemic CA16 strain (GenBank no. JX127258). NA11F12 was found to have high cross-neutralization activity against different CA16 subgenotypes but not EV71 using RD cells. The neutralizing titers of NA11F12 ranged from 1:1024 to 1:12288 against A, B1, B2 and C subgenotypes of CA16 and was less than 8 against EV71 strain. In the neonatal mouse model, a single treatment of NA11F12 showed effective protection with a dose- and time-dependent relationship against lethal challenge by CA16 strain (GenBank no. JX481738). At day 1 post-infection, administering more than 0.1 μg/g of NA11F12 could protect 100% newborn mice from mobility and mortality challenged by CA16. With dose of 10 μg/g of NA11F12, a single administration fully protected mice against CA16-associated disease within 4 days post-infection. And there were 80% and 60% mice protected by administering NA11F12 at day 5 post-infection and day 6 post-infection when the control mice had shown clinical symptoms for 1- and 2-day, respectively. Immunohistochemical and histological analysis confirmed that NA11F12 significantly prohibited CA16 VP1 expression in various tissues and prevented CA16-induced necrosis. In conclusion, a CA16-specific MAb NA11F12 with high cross-neutralization activity was identified, which could effectively protect lethal CA16 challenge in mice. It could be a potential therapeutic MAb against CA16 in the future.

Generation and testing anti-influenza human monoclonal antibodies in a new humanized mouse model (DRAGA: HLA-A2. HLA-DR4. Rag1 KO. IL-2Rγc KO. NOD)

Pandemic outbreaks of influenza type A viruses have resulted in numerous fatalities around the globe. Since the conventional influenza vaccines (CIV) provide less than 20% protection for individuals with weak immune system, it has been considered that broadly cross-neutralizing antibodies may provide a better protection. Herein, we showed that a recently generated humanized mouse (DRAGA mouse; HLA-A2. HLA-DR4. Rag1KO. IL-2Rgc KO. NOD) that lacks the murine immune system and expresses a functional human immune system can be used to generate cross-reactive, human anti-influenza monoclonal antibodies (hu-mAb). DRAGA mouse was also found to be suitable for influenza virus infection, as it can clear a sub-lethal infection and sustain a lethal infection with PR8/A/34 influenza virus. The hu-mAbs were designed for targeting a human B-cell epitope (¹⁸⁰WGIHHPPNSKEQ QNLY¹⁹⁵) of hemagglutinin (HA) envelope protein of PR8/A/34 (H1N1) virus with high homology among seven influenza type A viruses. A single administration of HA_180-195 specific hu-mAb in PR8-infected DRAGA mice significantly delayed the lethality by reducing the lung damage. The results demonstrated that DRAGA mouse is a suitable tool to (i) generate heterotype cross-reactive, anti-influenza human monoclonal antibodies, (ii) serve as a humanized mouse model for influenza infection, and (iii) assess the efficacy of anti-influenza antibody-based therapeutics for human use.

Antibody humanization methods for development of therapeutic applications

Recombinant antibody technologies are rapidly becoming available and showing considerable clinical success. However, the immunogenicity of murine-derived monoclonal antibodies is restrictive in cancer immunotherapy. Humanized antibodies can overcome these problems and are considered to be a promising alternative therapeutic agent. There are several approaches for antibody humanization. In this article we review various methods used in the antibody humanization process.

In vivo time-related evaluation of a therapeutic neutralization monoclonal antibody against lethal enterovirus 71 infection in a mouse model

Enterovirus 71 (EV71) is a neurotropic virus capable of inducing severe neurological symptoms and death. No direct targeting antivirals are useful in the treatment of severe EV71 infection. Because of low toxicity and good specificity, monoclonal antibodies (MAb) are a potential candidate for the treatment of viral infections. Therefore, we developed an EV71-specific conformational MAb with high in vitro cross-neutralization activity to heterologous EV71 subgenotypes. The in vivo treatment experiment at different days post-infection indicated that a single treatment of MAb CT11F9 within day 3 post-infection fully protected mice from morbidity and mortality (0% PBS vs. 100% at 10 µg/g per body weight ***P<0.0001). Immunohistochemical and histological analysis confirmed that CT11F9 significantly prohibited EV71 VP1 expression in various tissues and prevented EV71-induced myonecrosis. Moreover, thrice-treatment at day 4, 5, 6 post-infection was associated with an increased survival rate (18.2% single vs. 50% thrice at 20 µg/g per body weight), and the mice recovered from limb paralysis. Competitive ELISA also confirmed that CT11F9-recognized epitopes were immunodominant in humans. In conclusion, MAb CT11F9 is an ideal candidate to be humanized and used in severe EV71 infection.

Passive broad-spectrum influenza immunoprophylaxis

Influenza is a perennial problem affecting millions of people annually with the everpresent threat of devastating pandemics. Active prophylaxis by vaccination against influenza virus is currently the main countermeasure supplemented with antivirals. However, disadvantages of this strategy include the impact of antigenic drift, necessitating constant updating of vaccine strain composition, and emerging antiviral drug resistance. The development of other options for influenza prophylaxis, particularly with broad acting agents able to provide protection in the period between the onset of a pandemic and the development of a strain specific vaccine, is of great interest. Exploitation of broad-spectrum mediators could provide barricade protection in the early critical phase of influenza virus outbreaks. Passive immunity has the potential to provide immediate antiviral effects, inhibiting virus replication, reducing virus shedding, and thereby protecting vulnerable populations in the event of an impending influenza pandemic. Here, we review passive broad-spectrum influenza prophylaxis options with a focus on harnessing natural host defenses, including interferons and antibodies.

Novel approaches and challenges to treatment of central nervous system viral infections

Existing and emerging viral central nervous system (CNS) infections are major sources of human morbidity and mortality. Treatments of proven efficacy are currently limited predominantly to herpesviruses and human immunodeficiency virus (HIV). Development of new therapies has been hampered by the lack of appropriate animal model systems for some important viruses and by the difficulty in conducting human clinical trials for diseases that may be rare, or in the case of arboviral infections, often have variable seasonal and geographic incidence. Nonetheless, many novel approaches to antiviral therapy are available, including candidate thiazolide and pyrazinecarboxamide derivatives with potential broad‐spectrum antiviral efficacy. New herpesvirus drugs include viral helicase‐primase and terminase inhibitors. The use of antisense oligonucleotides and other strategies to interfere with viral RNA translation has shown efficacy in experimental models of CNS viral disease. Identifying specific molecular targets within viral replication cycles has led to many existing antiviral agents and will undoubtedly continue to be the basis of future drug design. A promising new area of research involves therapies based on enhanced understanding of host antiviral immune responses. Toll‐like receptor agonists and drugs that inhibit specific cytokines as well as interferon preparations have all shown potential therapeutic efficacy. Passive transfer of virus‐specific cytotoxic T lymphocytes has been used in humans and may provide an effective therapy for some herpesvirus infections and potentially for progressive multifocal leukoencephalopathy. Humanized monoclonal antibodies directed against specific viral proteins have been developed and in several cases evaluated in humans in settings including West Nile virus and HIV infection and in pre‐exposure prophylaxis for rabies. Ann Neurol 2013;74:412–422

Extent of antigenic cross-reactivity among highly pathogenic H5N1 influenza viruses

Highly pathogenic H5N1 avian influenza viruses emerged in 1996 and have since evolved so extensively that a single strain can no longer be used as a prepandemic vaccine or diagnostic reagent. We therefore sought to identify the H5N1 strains that may best serve as cross-reactive diagnostic reagents. We compared the cross-reactivity of 27 viruses of clades 0, 1, 2.1, 2.2, 2.3, and 4 and of four computationally designed ancestral H5N1 strains by hemagglutination inhibition (HI) and microneutralization (MN) assays. Antigenic cartography was used to analyze the large quantity of resulting data. Cartographs of HI titers with chicken red blood cells were similar to those of MN titers, but HI with horse red blood cells decreased antigenic distances among the H5N1 strains studied. Thus, HI with horse red blood cells seems to be the assay of choice for H5N1 diagnostics. Whereas clade 2.2 antigens were able to detect antibodies raised to most of the tested H5N1 viruses (and clade 2.2-specific antisera detected most of the H5N1 antigens), ancestral strain A exhibited the widest reactivity pattern and hence was the best candidate diagnostic reagent for broad detection of H5N1 strains.