Human monoclonal antibody and vaccine approaches to prevent human rabies

Ante-mortem and Post-mortem Diagnosis Modalities and Phylogenetic Analysis of Rabies Virus in Domestic and Wild Animals of Gujarat, India

In the present study, total of 32 ante-mortem (AM) samples (saliva = 18 and corneal smears = 14) from six animal species (cattle = 5; camel = 1; goat = 1; horse = 1; buffalo = 4; dog = 6) and 28 post-mortem (PM) samples of domestic (cattle = 6; camel = 1; goat = 1; buffalo = 5; dog = 7) and wild animals (lion = 4, mongoose = 2; bear = 1; leopard = 1) were examined for rabies diagnosis in Gujarat, India. Direct fluorescent antibody test (dFAT) and reverse transcriptase polymerase chain reaction (RT-PCR) were applied on AM samples, whereas along with dFAT and RT-PCR, histopathological examination, immunohistochemistry (IHC) and real time PCR (qPCR) were used for PM diagnosis. Nucleotide sequencing of full nucleoprotein (N) and glycoprotein (G) genes were carried out upon representative amplicons. In AM examination, 7/18 saliva and 5/14 corneal impressions samples were found positive in dFAT and 8/18 saliva samples were found positive in RT-PCR. In PM examination, 14/28 samples showed positive results in dFAT and IHC with unusual large fluorescent foci in two samples. In histopathology, 11/28 samples showed appreciable lesion and Negri bodies were visible in 6 samples, only. Out of 23 brain samples examined. 12 samples were found positive in N gene RT-PCR and qPCR, and 10 samples in G gene RT-PCR. Phylogenetic analysis of N gene revealed that test isolates (except sample ID: lion-1; lion, Gir) form a close group with sequence ID, KM099393.1 (Mongoose, Hyderabad) and KF660246.1 (Water Buffalo, Hyderabad) which was far from some south Indian and Sri Lankan isolates but similar to Indian isolates from rest of India and neighboring countries. In G gene analysis, the test isolates form a close group with sequence ID, KP019943.1.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01126-0.

Broadly neutralizing antibody cocktails targeting Nipah virus and Hendra virus fusion glycoproteins

Hendra virus (HeV) and Nipah virus (NiV) are henipaviruses (HNVs) causing respiratory illness and severe encephalitis in humans, with fatality rates of 50-100%. There are no licensed therapeutics or vaccines to protect humans. HeV and NiV use a receptor-binding glycoprotein (G) and a fusion glycoprotein (F) to enter host cells. HNV F and G are the main targets of the humoral immune response, and the presence of neutralizing antibodies is a correlate of protection against NiV and HeV in experimentally infected animals. We describe here two cross-reactive F-specific antibodies, 1F5 and 12B2, that neutralize NiV and HeV through inhibition of membrane fusion. Cryo-electron microscopy structures reveal that 1F5 and 12B2 recognize distinct prefusion-specific, conserved quaternary epitopes and lock F in its prefusion conformation. We provide proof-of-concept for using antibody cocktails for neutralizing NiV and HeV and define a roadmap for developing effective countermeasures against these highly pathogenic viruses.

In Vivo Efficacy of SYN023, an Anti-Rabies Monoclonal Antibody Cocktail, in Post-Exposure Prophylaxis Animal Models

Rabies immune globulin (RIG) is an indispensable component of rabies post-exposure prophylaxis (PEP) because it provides passive immunity to prevent this otherwise inescapably fatal disease in Category III exposed patients. Even with decades of development, RIG products are still criticized for their high cost, lot-to-lot variation, and potential safety issues. They remain largely unattainable in most developing regions of the world, where demand is highest. In recent years, monoclonal antibodies (MAbs) have become widely accepted as safer and more cost-effective alternatives to RIG products. As an example, SYN023 is a 1:1 cocktail of two humanized anti-rabies MAbs previously shown to display extensive neutralizing capabilities. Here, we further assessed the efficacy of SYN023 in animal models of rabies, and found that SYN023 afforded protection equal to a standard dose of human RIG (HRIG) at 0.03 mg/kg in Syrian hamsters and 0.1 mg/kg in beagles. Potential interference with vaccine-induced immunity was analyzed for the MAbs at these concentrations. While individual MAbs did not interfere with vaccine response, SYN023 at dosages of 0.1 mg/kg and above resulted in reduced neutralizing antibody titers similar to HRIG. Thus, the in vivo characterization of SYN023 supports its utility in human rabies PEP as an efficacious alternative to RIG products.

The Serological Prevalence of Rabies Virus-Neutralizing Antibodies in the Bat Population on the Caribbean Island of Trinidad

: Rabies virus (RABV) is the only lyssavirus known to be present within the Caribbean. The island of Trinidad, is richly diverse in chiropteran fauna and endemic for bat-transmitted rabies with low RABV isolation rates observed in this population. We aimed to determine the seroprevalence of rabies virus neutralizing antibodies (RVNA) in light of spatio-temporal and bat demographic factors to infer the extent of natural exposure to RABV in the Trinidadian bat population. RVNA titers were determined by the RABV micro-neutralization test on 383 bat samples representing 21 species, comprising 30.9% of local bat diversity, from 31 locations across the island over 5 years. RVNA was positively detected in 33 samples (8.6%) representing 6 bat species (mainly frugivorous) with titers ranging from 0.1 to 19 IU/mL (mean 1.66 IU/mL). The analyses based on a multivariable binomial generalised linear mixed-effects model showed that bat age and year of capture were significant predictors of seropositivity. Thus, juvenile bats were more likely to be seropositive when compared to adults (estimate 1.13; p = 0.04) which may suggest early exposure to the RABV with possible implications for viral amplification in this population. Temporal variation in rabies seropositivity, 2012-2014 versus 2015-2017 (estimate 1.07; p = 0.03) may have been related to the prevailing rabies epizootic situation. Regarding other factors investigated, RVNA was found in bats from both rural and non-rural areas, as well as in both hematophagous and non-hematophagous bat species. The most common seropositive species, Artibeusjamaicensisplanirostris is ubiquitous throughout the island which may potentially facilitate human exposure. The findings of this study should be factored into public health assessments on the potential for rabies transmission by non-hematophagous bats in Trinidad.

Four Thousand Years of Concepts Relating to Rabies in Animals and Humans, Its Prevention and Its Cure

The epitome of the One Health paradigm-and of its shortcomings-rabies has been known to humankind for at least 4000 years. We review the evolution through history of concepts leading to our current understanding of rabies in dogs and humans and its prevention, as transmitted by accessible and surviving written texts. The tools and concepts currently available to control rabies were developed at the end of the 19th Century, including the first live, attenuated vaccine ever developed for humans and the first post-exposure prophylaxis (PEP) regimen. No progress, however, has been made in etiological treatment, leaving clinicians who provide care to animals or patients with symptomatic rabies as powerless today as their colleagues in Mesopotamia, 40 centuries ago. Rabies remains to date the most lethal infectious disease known to humans. Widespread access to timely, effective, and affordable PEP in rural areas of developing countries is urgently needed.

Use of rabies immune globulin in seven urban emergency rooms in Pakistan

Background: Human rabies is a fatal infectious disease that is entirely preventable if correct and timely postexposure prophylaxis is given. Unfortunately, rabies immune globulin (RIG) administration, a life-saving biological, is often avoided by Emergency Room health care providers (HCPs).

Objective: To understand the practices of HCPs for administration of RIG in severe dog-bite exposures, which are common causes of emergency room visits in Pakistan.

Methods: A cross-sectional study was conducted among 103 HCPs working in seven hospitals in three cities of Pakistan.

Results: Of 103 HCPs who responded to the questionnaires, 97.1% had administered rabies vaccine and 31.1% had administered ERIG in the past three years of their practice; three quarters said they would prefer to use HRIG if available; 35% said they would not inject wounds at all, 24.3% would only vaccinate a patient with severe dog bites, but not administer RIG. More than 55% were concerned about the cost of human and equine RIG.

Conclusion: Although there is awareness about use of RIG, this life saving biological is grossly underused because of poor availability in Emergency Rooms (ERs) even though stocked by local dealers. Animal bite centers must make RIG available for severe exposures.

Stray dog trade fuelled by dog meat consumption as a risk factor for rabies infection in Calabar, southern Nigeria

BACKGROUND

Rabies is a preventable zoonosis with the highest case fatality of any disease in the world. In the developing world, it is transmitted mainly by dog bites. In parts of southern Nigeria, dog meat is a delicacy.

OBJECTIVE

To highlight trade in stray dogs as a major risk factor for rabies in animals and humans in south-south Nigeria.

METHOD

Patients admitted into the University of Calabar Teaching Hospital (UCTH) with a diagnosis of rabies between July and October 2012 were analysed for risk factors, post exposure prophylaxis (PEP), health seeking behaviour and outcome. Focused group interview were also conducted among traders/handlers of stray dogs.

RESULTS

Ten cases of rabies in subjects aged 3 to 52 years were recorded in these five months period. Eight of the cases were male and apparently got infected directly or indirectly through the trade in stray dogs for human consumption. None had proper PEP and all patients died.

CONCLUSION

Stray dog trade, fuelled by eating of dog meat, is a risk factor for human and animal rabies in Calabar, southern Nigeria. Culling of stray dogs, control of stray dogs' trade and public enlightenment on PEP is recommended.

Development of monoclonal antibodies suitable for rabies virus antibody and antigen detection

The control of an infectious viral disease as rabies is made easier by rapid and accurate diagnosis. Successful rabies prophylaxis is dependent upon the active immunization with vaccine along with passive administration of rabies virus neutralizing antibodies which together clear the virus before widespread infection of central nervous system occurs. The present study aimed at the development of monoclonal antibodies (MAbs) suitable for rabies virus antibody and antigen detection. For the production of rabies specific MAbs, immunization of Swiss albino mice with a commercially available vaccine was done and Polyethylene glycol mediated fusion of spleenocytes with myeloma cells was performed. The positive clones were selected on the basis of distinct reactivity by cell Enzyme linked immunosorbent assay and fluorescence in Indirect Fluorescent antibody test. The positive clones obtained were subjected to single cell cloning by limiting dilution method. The reactive clones were further titrated and employed for virus titration and virus neutralization. The neutralizing activity was evaluated using Fluorescence Activated Cell Sorter technique. Three MAb clones showed a distinct percent inhibition in the presence of positive serum. One of the MAb clone No. 5C3 was relatively more specific in detecting rabies antibodies and also found suitable for competitive ELISA to assess the antibody level in vaccinated subjects.

Plant-derived antigens as mucosal vaccines

During the last two decades, researchers have developed robust systems for recombinant subunit vaccine production in plants. Stably and transiently transformed plants have particular advantages that enable immunization of humans and animals via mucosal delivery. The initial goal to immunize orally by ingestion of plant-derived antigens has proven difficult to attain, although many studies have demonstrated antibody production in both humans and animals, and in a few cases, protection against pathogen challenge. Substantial hurdles for this strategy are low-antigen content in crudely processed plant material and limited antigen stability in the gut. An alternative is intranasal delivery of purified plant-derived antigens expressed with robust viral vectors, especially virus-like particles. The use of pattern recognition receptor agonists as adjuvants for mucosal delivery of plant-derived antigens can substantially enhance serum and mucosal antibody responses. In this chapter, we briefly review the methods for recombinant protein expression in plants, and describe progress with human and animal vaccines that use mucosal delivery routes. We do not attempt to compile a comprehensive list, but focus on studies that progressed to clinical trials or those that showed strong indications of efficacy in animals. Finally, we discuss some regulatory concerns regarding plant-based vaccines.

Immunological mechanisms of vaccination

Vaccines represent one of the greatest triumphs of modern medicine. Despite the common origins of vaccinology and immunology more than 200 years ago, the two disciplines have evolved along such different trajectories that most of the highly successful vaccines have been made empirically, with little or no immunological insight. Recent advances in innate immunity have offered new insights about the mechanisms of vaccine-induced immunity and have facilitated a more rational approach to vaccine design. Here we will discuss these advances and emerging themes on the immunology of vaccination.

Systems vaccinology

Vaccination is one of the greatest triumphs of modern medicine, yet we remain largely ignorant of the mechanisms by which successful vaccines stimulate protective immunity. Two recent advances are beginning to illuminate such mechanisms: realization of the pivotal role of the innate immune system in sensing microbes and stimulating adaptive immunity, and advances in systems biology. Recent studies have used systems biology approaches to obtain a global picture of the immune responses to vaccination in humans. This has enabled the identification of early innate signatures that predict the immunogenicity of vaccines, and identification of potentially novel mechanisms of immune regulation. Here, we review these advances and critically examine the potential opportunities and challenges posed by systems biology in vaccine development.

Human monoclonal antibodies and engineered antibody domains as HIV-1 entry inhibitors

PURPOSE OF REVIEW

To summarize the in-vivo efficacy of neutralizing human monoclonal antibodies against HIV-1, to discuss the recent finding that an engineered human antibody VH domain, domain antibody (dAb), exhibits exceptionally potent and broadly cross-reactive neutralizing activity against HIV-1 primary isolates by targeting a hidden conserved epitope that is not accessible by larger antibodies and to suggest the possibility of developing a novel class of potent HIV-1 inhibitors based on human dAbs.

RECENT FINDINGS

HIV-1 has evolved a number of strategies to evade humoral immunity, including protecting highly conserved and important structures from the access of antibodies generated by the immune system. We have recently demonstrated that a human dAb (size approximately 15 kDa), m36, targets a highly protected structure on the HIV-1 envelope glycoprotein (Env), gp120, and exhibits exceptionally potent neutralizing activity against HIV-1 primary isolates, with potency on average higher than those of the broadly cross-reactive neutralizing human monoclonal antibody, scFv m9, and the inhibitory peptide, C34.

SUMMARY

The efficacy of the anti-HIV-1 therapy is significantly compromised by resistance to the currently used US Food and Drug Administration-approved antiretroviral drugs, which suggests an urgent need to develop novel classes of potent inhibitors. Several broadly cross-reactive neutralizing human monoclonal antibodies are highly effective against HIV-1 infection in vitro, but their administration to HIV-1-infected humans has only resulted in modest antiviral effects. Engineered human antibody fragments, dAbs, could be more potent because of their small size (about 10-fold smaller than that of an IgG), which allows targeting of highly conserved structures on the HIV-1 envelope glycoprotein that are not accessible by full-size antibodies and relatively efficient penetration into the densely packed lymphoid environment in which HIV-1 mostly replicates and spreads.

Lyssaviruses: current trends

Various technological developments have revitalized the approaches employed to study the disease of rabies. In particular, reverse genetics has facilitated the generation of novel viruses used to improve our understanding of the fundamental aspects of rabies virus (RABV) biology and pathogenicity and yielded novel constructs potentially useful as vaccines against rabies and other diseases. Other techniques such as high throughput methods to examine the impact of rabies virus infection on host cell gene expression and two hybrid systems to explore detailed protein-protein interactions also contribute substantially to our understanding of virus-host interactions. This review summarizes much of the increased knowledge about rabies that has resulted from such studies but acknowledges that this is still insufficient to allow rational attempts at curing those who present with clinical disease.