Biology subjects

Aftalion, M.

Publications and source records attributed to Aftalion, M..

8 recordsLinked to original sources

bioRxiv2022

An Effective mRNA-LNP Vaccine Against the Lethal Plague Bacterium

Plague is a rapidly deteriorating contagious disease that has killed millions of people during the history of mankind and is caused by the gram-negative bacterium Yersinia pestis. Currently, the disease is treated effectively with antibiotics. However, in the case of an outbreak caused by a multiple-antibiotic-resistant strain, alternative countermeasures are required. Despite the many efforts to develop a safe vaccine against the disease, there is still no vaccine approved for use in western countries. mRNA Lipid Nanoparticle (mRNA-LNP) vaccines have been demonstrated during the Covid-19 pandemic to be a versatile, clinically relevant, and rapidly manufactured vaccine platform. However, harnessing this platform for bacterial pathogens remains a formidable challenge. Here, we describe the design of several mRNA-LNP vaccine versions against Y. pestis, based on the F1 capsular antigen. We demonstrate that mRNA-LNP vaccines encoding the F1 antigen with either no signal sequences or conjugated to human Fc, provide substantial cellular and humoral responses. Most importantly, these vaccine candidates fully protect animals against Y. pestis infection. The results of this study suggest that mRNA-LNPs can be effective as anti-bacterial vaccines, and further developed to combat other bacterial pathogens, which are urgently needed, given the looming threat of antibiotic resistance. One-Sentence SummaryA novel mRNA-LNP vaccine against Y. pestis, the etiological agent of plague and the first documented mRNA-LNP vaccine to protect against a lethal bacterial pathogen infection.

microbiology↗

bioRxiv2022

Phage therapy potentiates second-line antibiotic treatment against pneumonic plague

Plague pandemics and outbreaks have killed millions of people during the history of humankind. The disease, caused by Yersinia pestis bacteria, can currently be treated efficiently with antibiotics. However, in the case of multidrug-resistant (MDR) bacteria, alternative treatments are required. Bacteriophage (phage) therapy has shown efficient antibacterial activity in various experimental animal models and in human patients infected with different MDR pathogens. Herein, we evaluated the efficiency of {phi}A1122 and PST phage therapy, alone or in combination with second-line antibiotics, using a well-established mouse model of pneumonic plague. Phage treatment significantly delayed mortality and limited bacterial proliferation in the lungs. However, the treatment did not prevent bacteremia, suggesting that phage efficiency may decrease in circulation. Indeed, in vitro phage proliferation assays indicated that blood has inhibitory effects on lytic activity, which may be the major cause of treatment inefficiency. Combining phage therapy and second-line ceftriaxone treatment, which are individually insufficient, provided protection that led to survival of all infected animals, presenting a synergistic protective effect that represents a proof of concept for efficient combinatorial therapy in an emergency event of a plague outbreak involving MDR Y. pestis strains. Author summaryPlague, caused by Yersinia pestis bacteria, can be efficiently treated with antibiotics. However, alternative therapies for the case of natively evolved or maliciously generated antibiotic-resistant Y. pestis must be developed. Due to the global increase in antibiotic resistance, there is renewed interest in examining the effectiveness of bacteriophage-based alternative therapies. Here, using a mouse model of pneumonic plague, we demonstrate that phage treatment significantly delayed mortality. By monitoring bioluminescence of engineered Y. pestis strain and live bacterial counts, we show that phage therapy effectively inhibited bacterial proliferation in the lung but not in blood. In vitro analyses showed decreased phage activity in the presence of blood, which probably explains the low efficacy of phage treatment alone. Because combination therapies will be used in an emergency situation, we tested the efficacy of Y. pestis-lysing phages as adjunctive therapy with a second-line antibiotic, ceftriaxone. Whereas each individual treatment was insufficient, the combination provided effective protection and rescued all infected animals. These results clearly demonstrated the synergistic effect of combined phage and antibiotic therapy and represent a proof of concept for this alternative therapy against multidrug-resistant Y. pestis strains.

microbiology↗

bioRxiv2021

Monitoring group activity of hamsters and mice as a novel tool to evaluate COVID-19 progression, convalescence and rVSV-ΔG-spike vaccination efficacy

COVID-19 pandemic initiated a worldwide race toward the development of treatments and vaccines. Small animal models were the Syrian golden hamster and the K18-hACE2 mice infected with SARS-CoV-2 to display a disease state with some aspects of the human COVID-19. Group activity of animals in their home cage continuously monitored by the HCMS100 was used as a sensitive marker of disease, successfully detecting morbidity symptoms of SARS-CoV-2 infection in hamsters and in K18-hACE2 mice. COVID-19 convalescent hamsters re-challenged with SARS-CoV-2, exhibited minor reduction in group activity compared to naive hamsters. To evaluate rVSV-{Delta}G-spike vaccination efficacy against SARS-CoV-2, we used the HCMS100 to monitor group activity of hamsters in their home cage. Single-dose rVSV-{Delta}G-spike vaccination of immunized group showed a faster recovery compared to the non-immunized infected hamsters, substantiating the efficacy of rVSV-{Delta}G-spike vaccine. HCMS100 offers non-intrusive, hands-free monitoring of a number of home cages of hamsters or mice modeling COVID-19.

immunology↗

bioRxiv2021

Fc-independent neutralization of SARS-CoV-2 by recombinant human monoclonal antibodies

The use of passively-administered neutralizing antibodies is a promising approach for the prevention and treatment of SARS-CoV-2 infection. Antibody-mediated protection may involve immune system recruitment through Fc-dependent activation of effector cells and the complement system. However, the role of Fc-mediated functions in the efficacious in vivo neutralization of SARS-CoV-2 is not yet clear. Delineating the role this process plays in antibody-mediated protection will have a great impact on the design of such therapeutics. Here, the Fc of two highly potent SARS-CoV-2 neutralizing human monoclonal antibodies, targeting distinct domains of the spike, was engineered to abrogate their Fc-dependent functions. The protective activity of these antibodies was tested against lethal SARS-CoV-2 infections in K18-hACE2 transgenic mice, both before or two days post-exposure in comparison to their original, Fc-active antibodies. Antibody treatment with both Fc-variants similarly rescued the mice from death, reduced viral load and prevented signs of morbidity. In addition, surviving animals developed a significant endogenous immune response towards the virus. Taken together, this work provides important insight regarding the contribution of Fc-effector functions in antibody-mediated protection, which should aid in future design of effective antibody-based therapies.

immunology↗

bioRxiv2021

A lipid nanoparticle RBD-hFc mRNA vaccine protects hACE2 transgenic mice against lethal SARS-CoV-2 infection

The current global COVID-19 pandemic led to an unprecedented effort to develop effective vaccines against SARS-CoV-2. mRNA vaccines were developed very rapidly during the last year, and became the leading immunization platform against the virus, with highly promising phase-3 results and remarkable efficacy data. Since most animal models are not susceptible to SARS CoV-2 infection, pre-clinical studies are often limited to infection-prone animals such as hamsters and non-human primates. In these animal models, SARS-CoV-2 infection results in viral replication and a mild disease disease. Therefore, the protective efficacy of the vaccine in these animals is commonly evaluated by its ability to elicit immunologic responses, diminish viral replication and prevent weight loss. Our lab recently reported the design of a SARS-CoV-2 human Fc-conjugated receptor-binding domain (RBD-hFc) mRNA vaccine delivered via lipid nanoparticles (LNPs). These experiments demonstrated the development of a robust and specific immunologic response in RBD-hFc mRNA-vaccinated BALB/c mice. In the current study, we evaluated the protective effect of this RBD-hFc mRNA vaccine by employing the K18-hACE2 mouse model. We report that administration of RBD-hFc mRNA vaccine to K18-hACE2 mice led to a robust humoral response comprised of both binding and neutralizing antibodies. In accordance with the recorded immunologic immune response, 70% of vaccinated mice were protected against a lethal dose (3000 plaque forming units) of SARS-CoV-2, while all control animals succumbed to infection. To the best of our knowledge, this is the first non-replicating mRNA vaccine study reporting protection of K18-hACE2 against a lethal SARS-CoV-2 infection.

microbiology↗

bioRxiv2021

Therapeutic antibodies, targeting the SARS-CoV-2 spike N-terminal domain, protect lethally infected K18-hACE2 mice

Since the onset of the current COVID-19 pandemic, high priority is given to the development of neutralizing antibodies, as a key approach for the design of therapeutic strategies to countermeasure and eradicate the disease. Previously, we reported the development of human therapeutic monoclonal antibodies (mAbs) exhibiting very high protective ability. These mAbs recognize epitopes on the spike receptor binding domain (RBD) of SARS-CoV-2 that is considered to represent the main rout of receptor engagement by the SARS-CoV-2 virus. The recent emergence of viral variants emphasizes the notion that efficient antibody treatments need to rely on mAbs against several distinct key epitopes in order to circumvent the occurrence of therapy escape-mutants. Here we report the isolation and characterization of 12 neutralizing mAbs, identified by screening a phage-display library constructed from lymphatic cells collected from severe COVID-19 patients. The antibodies target three distinct epitopes on the spike N-terminal domain (NTD) of SARS-CoV-2, one of them defining a major site of vulnerability of the virus. Extensive characterization of these mAbs suggests a neutralization mechanism which relies both on amino-acid and N-glycan recognition on the virus, and involvement of receptors other than the hACE2 on the target cell. Two of the selected mAbs, which demonstrated superior neutralization potency in vitro, were further evaluated in vivo, demonstrating their ability to fully protect K18-hACE2 transgenic mice even when administered at low doses and late after infection. The study demonstrates the high potential of the mAbs for therapy of SARS-CoV-2 infection and underlines the possible role of the NTD in mediating infection of host cells via alternative cellular portals other than the canonical ACE2 receptor.

immunology↗

bioRxiv2020

Induced pulmonary comorbidities render CD-1 mice sensitive to SARS-CoV-2

Severe manifestations of COVID-19 are mostly restricted to people with comorbidities. Here we report that induced mild pulmonary morbidities render SARS-CoV-2-refractive CD-1 mice to be susceptible to this virus. Specifically, SARS-CoV-2 infection after application of low-doses of the acute-lung-injury stimulants bleomycin or ricin caused a severe disease in CD-1 mice, manifested by sustained body weight loss and mortality rates of >50%. Further studies revealed markedly higher levels of viral RNA in the lungs, heart and serum of low-dose-ricin pretreated, as compared to non-pretreated mice. Notably, the deleterious effects of SARS-CoV-2 infection were effectively alleviated by passive transfer of polyclonal or monoclonal antibodies generated against SARS-CoV-2 RBD. Thus, viral cell entry in the sensitized mice seems to involve viral RBD binding, albeit by a mechanism other than the canonical ACE2-mediated uptake route. In summary, we present a novel mice-based animal model for the study of comorbidity-dependent severe COVID-19.

pathology↗

bioRxiv2020

Post-exposure protection of SARS-CoV-2 lethal infected K18-hACE2 transgenic mice by neutralizing human monoclonal antibody

Coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), exhibits high levels of mortality and morbidity and has dramatic consequences on human life, sociality and global economy. Neutralizing antibodies constitute a highly promising approach for treating and preventing infection by this novel pathogen. In the present study, we characterized and further evaluated the recently identified human monoclonal MD65 antibody for its ability to provide protection against a lethal SARS-CoV-2 infection of K18-hACE2 transgenic mice. Eighty percent of the untreated mice succumbed 6-9 days post-infection while administration of the MD65 antibody as late as 3 days after exposure, rescued all infected animals. In addition, the efficiency of the treatment is supported by prevention of morbidity and ablation of the load of infective virions in the lungs of treated animals. The data unprecedentedly demonstrate, the therapeutic value of human monoclonal antibodies as a life-saving treatment of severe COVID-19 infection.

immunology↗