A hydrogen peroxide-inactivated virus vaccine elicits humoral and cellular immunity and protects against lethal West Nile virus infection in aged mice

Protein characterization of an Indonesian isolate of foot and mouth disease virus inactivated with formaldehyde and binary ethylenimine

Background and Aim

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-footed animals. It is a major threat to livestock production worldwide, causing significant economic losses. Inactivation of FMD virus (FMDV) is crucial for vaccine development and control of outbreaks. However, traditional inactivation methods can sometimes damage the viral protein, affecting vaccine efficacy. Therefore, finding new inactivating agents that effectively inactivate the virus while preserving the integrity of its proteins is an important research area. This study investigated the optimal materials (0.04% formaldehyde, 0.001 M binary ethylenimine [BEI], or a combination) for inactivating and preserving the specific molecular weight of Serotype O FMDV protein.

Materials and Methods

This study used serotype O FMDV isolated from several areas of East Java. The virus was inoculated into baby hamster kidney-21 cells, and the titer was calculated using the TCID50 Assay. The virus was inactivated using 0.04% formaldehyde, 0.001 M BEI, or a combination of 0.04% formaldehyde and 0.001 M BEI. Inactive viral proteins were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blotting.

Results

Serotype O FMDV can be inactivated using 0.04% formaldehyde while preserving specific FMDV proteins, specifically VP0 and VP3 with a molecular weight (MW) of 36 kDa and VP3 with a MW of 24 kDa. Serotype O FMDV can be inactivated by 0.001 M BEI while preserving specific FMDV proteins, specifically VP0 with a MW of 35 kDa, VP3 with a MW of 28 kDa, and VP1 with a MW of 23 kDa. FMDV serotype O can be inactivated using a combination of 0.04% formaldehyde and 0.001 M BEI while preserving specific FMDV proteins, specifically VP0 and VP3 with a MW of 36 kDa and VP3 with a MW of 24 kDa.

Conclusion

This study found that 0.04% formaldehyde, alone or in combination with 0.001 M BEI, was effective for inactivating and preserving the specific molecular weight of Serotype O FMDV protein. The limitation of this study was the inactivations of the virus have not yet been tested for their potency on experimental animals. Further research is warranted to investigate the inactivation kinetics of these materials, including their potency on experimental animals. Additionally, a comparison of the inactivation rates between 0.04% formaldehyde alone and the combination with BEI would help to determine the optimal inactivation agent for future applications.

Development of a hydrogen peroxide-inactivated vaccine that protects against viscerotropic yellow fever in a non-human primate model

Yellow fever virus (YFV) is endemic in >40 countries and causes viscerotropic disease with up to 20%-60% mortality. Successful live-attenuated yellow fever (YF) vaccines were developed in the mid-1930s, but their use is restricted or formally contraindicated in vulnerable populations including infants, the elderly, and people with compromised immune systems. In these studies, we describe the development of a next-generation hydrogen peroxide-inactivated YF vaccine and determine immune correlates of protection based on log neutralizing index (LNI) and neutralizing titer-50% (NT50) studies. In addition, we compare neutralizing antibody responses and protective efficacy of hydrogen peroxide-inactivated YF vaccine candidates to live-attenuated YFV-17D (YF-VAX) in a rhesus macaque model of viscerotropic YF. Our results indicate that an optimized, inactivated YF vaccine elicits protective antibody responses that prevent viral dissemination and lethal infection in rhesus macaques and may be a suitable alternative for vaccinating vulnerable populations who are not eligible to receive replicating live-attenuated YF vaccines.

Precise modulation and use of reactive oxygen species for immunotherapy

Reactive oxygen species (ROS) play an important role in regulating the immune system by affecting pathogens, cancer cells, and immune cells. Recent advances in biomaterials have leveraged this mechanism to precisely modulate ROS levels in target tissues for improving the effectiveness of immunotherapies in infectious diseases, cancer, and autoimmune diseases. Moreover, ROS-responsive biomaterials can trigger the release of immunotherapeutics and provide tunable release kinetics, which can further boost their efficacy. This review will discuss the latest biomaterial-based approaches for both precise modulation of ROS levels and using ROS as a stimulus to control the release kinetics of immunotherapeutics. Finally, we will discuss the existing challenges and potential solutions for clinical translation of ROS-modulating and ROS-responsive approaches for immunotherapy, and provide an outlook for future research.

An inactivated whole-virion vaccine for Enterovirus D68 adjuvanted with CpG ODN or AddaVax elicits potent protective immunity in mice

Enterovirus D68 (EV-D68), a pathogen that causes respiratory symptoms, mainly in children, has been implicated in acute flaccid myelitis, which is a poliomyelitis-like paralysis. Currently, there are no licensed vaccines or treatments for EV-D68 infections. Here, we investigated the optimal viral inactivation reagents, vaccine adjuvants, and route of vaccination in mice to optimize an inactivated whole-virion (WV) vaccine against EV-D68. We used formalin, β-propiolactone (BPL), and hydrogen peroxide as viral inactivation reagents and compared their effects on antibody responses. Use of any of these three viral inactivation reagents effectively induced neutralizing antibodies. Moreover, the antibody response induced by the BPL-inactivated WV vaccine was enhanced when adjuvanted with cytosine phosphoguanine oligodeoxynucleotide (CpG ODN) or AddaVax (MF59-like adjuvant), but not with aluminum hydroxide (alum). Consistent with the antibody response results, the protective effect of the inactivated WV vaccine against the EV-D68 challenge was enhanced when adjuvanted with CpG ODN or AddaVax, but not with alum. Further, while the intranasal inactivated WV vaccine induced EV-D68-specific IgA antibodies in the respiratory tract, it was less protective against EV-D68 challenge than the injectable vaccine. Thus, an injectable inactivated EV-D68 WV vaccine prepared with appropriate viral inactivation reagents and an optimal adjuvant is a promising EV-D68 vaccine.

Efficacy of H2O2 inactivated bovine virus diarrhoea virus (BVDV) type 1 vaccine in mice

BACKGROUND

Bovine viral diarrhea (BVD) is an acute febrile infectious disease caused by the bovine viral diarrhea virus (BVDV), which has brought huge economic losses to the world's cattle industry. At present, commercial inactivated BVDV vaccines may cause some adverse reactions during use. This study aims to develop a safer and more efficient inactivated BVDV vaccine.

METHODS

Here, we described the generation and preclinical efficacy of a hydrogen peroxide (H2O2) inactivated BVDV type 1 vaccine in mice, and administered it separately with commercial vaccine (formaldehyde inactivated) in mice to study its efficacy.

RESULTS

The BVDV type 1 IgG, IFN- γ, IL-4 and neutralizing antibody in the serum of the H2O2 inactivated vaccine group can be maintained in mice for 70 days. The IgG level reached its maximum value of 0.67 on the 42nd day, significantly higher than the commercial formaldehyde inactivated BVDV type 1 vaccine. IFN- γ and IL-4 reached their maximum values on the 28th day after immunization, at 123.16 pg/ml and 143.80 pg/ml, respectively, slightly higher than commercial vaccines, but the effect was not significant. At the same time the BVDV-1 neutralizing antibody titer reached a maximum of 12 Nu on the 42nd day post vaccination.

CONCLUSIONS

The H2O2 inactivated BVDV vaccine has good safety and immunogenicity, which provides a potential solution for the further development of an efficient and safe BVDV vaccine.

Immunization with different recombinant West Nile virus envelope proteins induces varying levels of serological cross-reactivity and protection from infection

Introduction

West Nile Virus (WNV) is a zoonotic flavivirus transmitted by mosquitoes. Especially in the elderly or in immunocompromised individuals an infection with WNV can lead to severe neurological symptoms. To date, no human vaccine against WNV is available. The Envelope (E) protein, located at the surface of flaviviruses, is involved in the invasion into host cells and is the major target for neutralizing antibodies and therefore central to vaccine development. Due to their close genetic and structural relationship, flaviviruses share highly conserved epitopes, such as the fusion loop domain (FL) in the E protein, that are recognized by cross-reactive antibodies. These antibodies can lead to enhancement of infection with heterologous flaviviruses, which is a major concern for potential vaccines in areas with co-circulation of different flaviviruses, e.g. Dengue or Zika viruses.

Material

To reduce the potential of inducing cross-reactive antibodies, we performed an immunization study in mice using WNV E proteins with either wild type sequence or a mutated FL, and WNV E domain III which does not contain the FL at all.

Results and discussion

Our data show that all antigens induce high levels of WNV-binding antibodies. However, the level of protection against WNV varied, with the wildtype E protein inducing full, the other antigens only partial protection. On the other hand, serological cross-reactivity to heterologous flaviviruses was significantly reduced after immunization with the mutated E protein or domain III as compared to the wild type version. These results have indications for choosing antigens with the optimal specificity and efficacy in WNV vaccine development.

Manipulation of Oxidative Stress Responses by Non-Thermal Plasma to Treat Herpes Simplex Virus Type 1 Infection and Disease

Herpes simplex virus type 1 (HSV-1) is a contagious pathogen with a large global footprint, due to its ability to cause lifelong infection in patients. Current antiviral therapies are effective in limiting viral replication in the epithelial cells to alleviate clinical symptoms, but ineffective in eliminating latent viral reservoirs in neurons. Much of HSV-1 pathogenesis is dependent on its ability to manipulate oxidative stress responses to craft a cellular environment that favors HSV-1 replication. However, to maintain redox homeostasis and to promote antiviral immune responses, the infected cell can upregulate reactive oxygen and nitrogen species (RONS) while having a tight control on antioxidant concentrations to prevent cellular damage. Non-thermal plasma (NTP), which we propose as a potential therapy alternative directed against HSV-1 infection, is a means to deliver RONS that affect redox homeostasis in the infected cell. This review emphasizes how NTP can be an effective therapy for HSV-1 infections through the direct antiviral activity of RONS and via immunomodulatory changes in the infected cells that will stimulate anti-HSV-1 adaptive immune responses. Overall, NTP application can control HSV-1 replication and address the challenges of latency by decreasing the size of the viral reservoir in the nervous system.

Antibody-Dependent Enhancement Activity of a Plant-Made Vaccine against West Nile Virus

West Nile virus (WNV) causes annual outbreaks globally and is the leading cause of mosquito-borne disease in Unite States. In the absence of licensed therapeutics, there is an urgent need to develop effective and safe human vaccines against WNV. One of the major safety concerns for WNV vaccine development is the risk of increasing infection by related flaviviruses in vaccinated subjects via antibody-dependent enhancement of infection (ADE). Herein, we report the development of a plant-based vaccine candidate that provides protective immunity against a lethal WNV challenge mice, while minimizes the risk of ADE for infection by Zika (ZIKV) and dengue (DENV) virus. Specifically, a plant-produced virus-like particle (VLP) that displays the WNV Envelope protein domain III (wDIII) elicited both high neutralizing antibody titers and antigen-specific cellular immune responses in mice. Passive transfer of serum from VLP-vaccinated mice protected recipient mice from a lethal challenge of WNV infection. Notably, VLP-induced antibodies did not enhance the infection of Fc gamma receptor-expressing K562 cells by ZIKV or DENV through ADE. Thus, a plant-made wDIII-displaying VLP presents a promising WNV vaccine candidate that induces protective immunity and minimizes the concern of inducing ADE-prone antibodies to predispose vaccinees to severe infection by DENV or ZIKV.

Comparing the Immunogenicity and Protective Effects of Three MERS-CoV Inactivation Methods in Mice

The Middle East respiratory syndrome (MERS) is a fatal acute viral respiratory disease caused by MERS-coronavirus (MERS-CoV) infection. To date, no vaccine has been approved for MERS-CoV despite continuing outbreaks. Inactivated vaccines are a viable option when developed using the appropriate inactivation methods and adjuvants. In this study, we evaluated the immunogenicity and protective effects of MERS-CoV vaccine candidates inactivated by three different chemical agents. MERS-CoV was effectively inactivated by formaldehyde, hydrogen peroxide, and binary ethylene imine and induced humoral and cellular immunity in mice. Although inflammatory cell infiltration was observed in the lungs four days after the challenge, the immunized hDPP4-transgenic mouse group showed 100% protection against a challenge with MERS-CoV (100 LD50). In particular, the immune response was highly stimulated by MERS-CoV inactivated with formaldehyde, and all mice survived a challenge with the minimum dose. In the adjuvant comparison test, the group immunized with inactivated MERS-CoV and AddaVax had a higher immune response than the group immunized with aluminum potassium sulfate (alum). In conclusion, our study indicates that the three methods of MERS-CoV inactivation are highly immunogenic and protective in mice and show strong potential as vaccine candidates when used with an appropriate adjuvant.

Development of a next-generation chikungunya virus vaccine based on the HydroVax platform

Chikungunya virus (CHIKV) is an emerging/re-emerging mosquito-borne pathogen responsible for explosive epidemics of febrile illness characterized by debilitating polyarthralgia and the risk of lethal infection among the most severe cases. Despite the public health risk posed by CHIKV, no vaccine is currently available. Using a site-directed hydrogen peroxide-based inactivation approach, we developed a new CHIKV vaccine, HydroVax-CHIKV. This vaccine technology was compared to other common virus inactivation approaches including β-propiolactone (BPL), formaldehyde, heat, and ultraviolet (UV) irradiation. Heat, UV, and BPL were efficient at inactivating CHIKV-181/25 but caused substantial damage to neutralizing epitopes and failed to induce high-titer neutralizing antibodies in vaccinated mice. HydroVax-CHIKV and formaldehyde-inactivated CHIKV retained intact neutralizing epitopes similar to live virus controls but the HydroVax-CHIKV approach demonstrated a more rapid rate of virus inactivation. HydroVax-CHIKV vaccination induced high neutralizing responses to homologous and heterologous CHIKV clades as well as to other alphaviruses including Mayaro virus, O’nyong’nyong virus, and Una virus. Following heterologous infection with CHIKV-SL15649, HydroVax-CHIKV-immunized mice were protected against viremia, CHIKV-associated arthritic disease, and lethal CHIKV infection by an antibody-dependent mechanism. In contrast, animals vaccinated with Heat- or UV-inactivated virus showed no protection against viremia in addition to demonstrating significantly exacerbated CD4⁺ T cell-mediated footpad swelling after CHIKV infection. Together, these results demonstrate the risks associated with using suboptimal inactivation methods that fail to elicit protective neutralizing antibody responses and show that HydroVax-CHIKV represents a promising new vaccine candidate for prevention of CHIKV-associated disease.

Chikungunya virus (CHIKV) is a mosquito-borne virus that has gained significant attention due to its ability to cause large epidemics and to spread beyond endemic countries through international travelers. Despite substantial efforts over the course of many years, a licensed CHIKV vaccine remains unavailable for protecting at-risk populations. Our research group has established an advanced site-directed oxidation system, termed HydroVax, for the development of new vaccines. Here, we describe a novel CHIKV vaccine that utilizes this peroxide-based vaccine platform and demonstrates greatly improved antiviral immunity compared to other traditional virus inactivation approaches as well as complete protection against viremia, CHIKV-associated arthritic disease and lethal CHIKV infection in robust preclinical mouse models. The HydroVax-CHIKV vaccine not only induced neutralizing antibodies to geographically diverse strains of CHIKV, but also elicited neutralizing antibody responses to other clinically important alphaviruses including, Mayaro, O’nyong’nyong, and Una virus. Together, this indicates that this vaccine not only protects against CHIKV infection but may potentially provide immunity across a broader range of virulent alphaviruses as well.

Methods of Inactivation of Highly Pathogenic Viruses for Molecular, Serology or Vaccine Development Purposes

The handling of highly pathogenic viruses, whether for diagnostic or research purposes, often requires an inactivation step. This article reviews available inactivation techniques published in peer-reviewed journals and their benefits and limitations in relation to the intended application. The bulk of highly pathogenic viruses are represented by enveloped RNA viruses belonging to the Togaviridae, Flaviviridae, Filoviridae, Arenaviridae, Hantaviridae, Peribunyaviridae, Phenuiviridae, Nairoviridae and Orthomyxoviridae families. Here, we summarize inactivation methods for these virus families that allow for subsequent molecular and serological analysis or vaccine development. The techniques identified here include: treatment with guanidium-based chaotropic salts, heat inactivation, photoactive compounds such as psoralens or 1.5-iodonaphtyl azide, detergents, fixing with aldehydes, UV-radiation, gamma irradiation, aromatic disulfides, beta-propiolacton and hydrogen peroxide. The combination of simple techniques such as heat or UV-radiation and detergents such as Tween-20, Triton X-100 or Sodium dodecyl sulfate are often sufficient for virus inactivation, but the efficiency may be affected by influencing factors including quantity of infectious particles, matrix constitution, pH, salt- and protein content. Residual infectivity of the inactivated virus could have disastrous consequences for both laboratory/healthcare personnel and patients. Therefore, the development of inactivation protocols requires careful considerations which we review here.

Testing Novel Inactivation Methods and Adjuvants for Vaccines Against Streptococcus agalactiae in Nile Tilapia Oreochromis niloticus

Inactivation by hydrogen peroxide and pH manipulation are two novel methods used recently in experimental vaccines against Streptococcus agalactiae in Nile tilapia. Here we describe in detail inactivation using novel methods as well as the classical method of inactivation. These vaccines showed similar moderate efficacy when compared to the conventional formaldehyde vaccine. In addition, we describe the inclusion of adjuvants in a hydrogen peroxide vaccine.

An Overview of Veterinary Viral Diseases and Vaccine Technologies

Ensuring the maximum standards of quality and welfare in animal production requires developing effective tools to halt and prevent the spread of the high number of infectious diseases affecting animal husbandry. Many of these diseases are caused by pathogens of viral etiology. To date, one of the best strategies is to implement preventive vaccination policies whenever possible. However, many of the currently manufactured animal vaccines still rely in classical vaccine technologies (killed or attenuated vaccines). Under some circumstances, these vaccines may not be optimal in terms of safety and immunogenicity, nor adequate for widespread application in disease-free countries at risk of disease introduction. One step ahead is needed to improve and adapt vaccine manufacturing to the use of new generation vaccine technologies already tested in experimental settings. In the context of viral diseases of veterinary interest, we overview current vaccine technologies that can be approached, with a brief insight in the type of immunity elicited.

Vaccination with a Brucella ghost developed through a double inactivation strategy provides protection in Guinea pigs and cattle

Vaccination can prevent and control animal brucellosis. Currently, live attenuated vaccines are extensively used to prevent Brucella infection. However, traditional vaccines such as live attenuated vaccines are associated with biological safety risks for both humans and animals. The bacterial ghost (BG) is a new form of vaccine with great prospects. However, bacterial cells cannot be completely inactivated by biological lysis, conferring a safety risk associated with the vaccine. In this study, we developed a Brucella abortus A19 bacterial ghost (A19BG) through a double inactivation strategy with sequential biological lysis and hydrogen peroxide treatment. This strategy resulted in 100% inactivation of Brucella, such that viable bacterial cells were not detected even at an ultrahigh concentration of 10¹⁰ colony-forming units/mL. Furthermore, A19BG had a typical BG morphology and good genetic stability. Moreover, it did not induce adverse reactions in guinea pigs. The levels of antibodies, interferon-γ, interleukin-4, and CD4⁺ T cells in guinea pigs inoculated with the A19BG vaccine were similar to those inoculated with the existing A19 vaccine. Immunization with A19BG conferred a similar level of protection with that of A19 against Brucella melitensis M28 in both guinea pigs and cattle. In conclusion, the combination of biological lysis and H₂O₂-mediated inactivation is a safe and effective strategy that can serve as a reference for the preparation of BG vaccines.

Obesity Enhances Disease Severity in Female Mice Following West Nile Virus Infection

A rise in adiposity in the United States has resulted in more than 70% of adults being overweight or obese, and global obesity rates have tripled since 1975. Following the 2009 H1N1 pandemic, obesity was characterized as a risk factor that could predict severe infection outcomes to viral infection. Amidst the SARS-CoV-2 pandemic, obesity has remained a significant risk factor for severe viral disease as obese patients have a higher likelihood for developing severe symptoms and requiring hospitalization. However, the mechanism by which obesity enhances viral disease is unknown. In this study, we utilized a diet-induced obesity mouse model of West Nile virus (WNV) infection, a flavivirus that cycles between birds and mosquitoes and incidentally infects both humans and mice. Likelihood for severe WNV disease is associated with risk factors such as diabetes that are comorbidities also linked to obesity. Utilizing this model, we showed that obesity-associated chronic inflammation increased viral disease severity as obese female mice displayed higher mortality rates and elevated viral titers in the central nervous system. In addition, our studies highlighted that obesity also dysregulates host acute adaptive immune responses, as obese female mice displayed significant dysfunction in neutralizing antibody function. These studies highlight that obesity-induced immunological dysfunction begins at early time points post infection and is sustained through memory phase, thus illuminating a potential for obesity to alter the differentiation landscape of adaptive immune cells.

Immunity to acute virus infections with advanced age

New infections in general, and new viral infections amongst them, represent a serious challenge to an older organism. This review discusses the age-related alterations in responsiveness to infection from the standpoint of virus:host relationship and the host physiological whole-organism and specific immune response to the virus. Changes with age in the innate and adaptive immune system homeostasis and function are reviewed briefly. This is followed by a review of specific alterations and defects in the response of older organisms (chiefly mice and humans) to acute (particularly emerging and re-emerging) viral infections, with a very brief summary of the response to latent persistent infections. Finally, we provide a brief summary of the perspectives for possible interventions to enhance antiviral immunity.

In-Vitro Inactivation of Sabin-Polioviruses for Development of Safe and Effective Polio Vaccine

After years of global collaboration; we are steps away from a polio-free world. However, the currently conventional inactivated polio vaccine (cIPV) is suboptimal for the post eradication era. cIPV production cost and biosafety hazards hinder its availability and coverage of the global demands. Production of IPV from the attenuated Sabin strains (sIPV) was an ideal solution and scientists work extensively to perfect a safe, effective and affordable sIPV. This study investigated the ability of hydrogen peroxide (H₂O₂), ascorbic acid (AA) and epigallocatechin-3-gallate (EGCG) as alternatives for Formaldehyde (HCHO) to inactivate Sabin-polioviruses strains for sIPV production. Sabin-polioviruses vaccine strains were individually treated with AA, EGCG or H₂O₂ and were compared to HCHO. This was investigated by determination of the inactivation kinetics on HEP_2C cells, testing of D-antigen preservation by ELISA and the immune response in Wistar rats of the four vaccine preparations. H₂O₂, AA and EGCG were able to inactivate polioviruses within 24 h while HCHO required 96 h. Significant high D-antigen levels were observed using AA, EGCG and H₂O₂ compared to HCHO. Rat sera tested for neutralizing antibodies showed comparable results. These findings support the idea of using these inactivating agents as safe and time- saving alternatives for HCHO to produce sIPV.

Efficacy of two adjuvants administrated with a novel hydrogen peroxide-inactivated vaccine against Streptococcus agalactiae in Nile tilapia fingerlings

Streptococcus agalactiae is considered the main bacterial pathogen in cultured Nile tilapia. Formaldehyde-inactivated vaccines are the most accepted method for prevention and control of the disease. However, alternative inactivation methods for S. agalactiae vaccines have not been fully explored. Recently, we developed a hydrogen peroxide-inactivated vaccine against S. agalactiae with moderate efficacy, with the possibility to improve vaccine efficacy by adding adjuvants. The current study compared the efficacy of aluminum hydroxide and Freund's incomplete adjuvant (FIA) incorporated into a novel hydrogen peroxide-inactivated intraperitoneal vaccine against S. agalactiae for Nile tilapia fingerlings. The relative percentage survival (RPS) for aluminum hydroxide-adjuvanted vaccine (59.3%), and FIA-adjuvanted vaccine (77.8%) were higher than the vaccine without adjuvant (40.7%). In addition, fish immunized with aluminum hydroxide-adjuvanted vaccine had significantly higher levels of specific antibodies than control fish at 4 weeks post vaccination (wpv). Blood lymphocytes counts showed a decrease in vaccinated groups when compared to control fish, suggesting white cells migration to the tissues where antigen presentation is ongoing. Fish that received FIA-adjuvanted vaccine exhibited persistence of adjuvant deposits on intraperitoneal surfaces for at least 4 wpv that may be related to its superior performance compared to aluminum hydroxide adjuvanted vaccine, which did not evidence any type of deposit at any sampling times. The results observed in this study demonstrate that hydrogen peroxide-inactivated vaccine administered with either aluminum hydroxide or FIA induce optimal levels of protection, with a superior performance for FIA vaccine, which could be a good alternative to conventional formaldehyde-inactivated vaccines against S. agalactiae, due to its shorter manufacture time, and less toxicity.

The Role of Microglia during West Nile Virus Infection of the Central Nervous System

Encephalitis resulting from viral infections is a major cause of hospitalization and death worldwide. West Nile Virus (WNV) is a substantial health concern as it is one of the leading causes of viral encephalitis in the United States today. WNV infiltrates the central nervous system (CNS), where it directly infects neurons and induces neuronal cell death, in part, via activation of caspase 3-mediated apoptosis. WNV infection also induces neuroinflammation characterized by activation of innate immune cells, including microglia and astrocytes, production of inflammatory cytokines, breakdown of the blood-brain barrier, and infiltration of peripheral leukocytes. Microglia are the resident immune cells of the brain and monitor the CNS for signs of injury or pathogens. Following infection with WNV, microglia exhibit a change in morphology consistent with activation and are associated with increased expression of proinflammatory cytokines. Recent research has focused on deciphering the role of microglia during WNV encephalitis. Microglia play a protective role during infections by limiting viral growth and reducing mortality in mice. However, it also appears that activated microglia are triggered by T cells to mediate synaptic elimination at late times during infection, which may contribute to long-term neurological deficits following a neuroinvasive WNV infection. This review will discuss the important role of microglia in the pathogenesis of a neuroinvasive WNV infection. Knowledge of the precise role of microglia during a WNV infection may lead to a greater ability to treat and manage WNV encephalitis.

Current Flavivirus Research Important for Vaccine Development

The Flaviviridae family of RNA viruses includes numerous human disease-causing pathogens that largely are increasing in prevalence due to continual climate change, rising population sizes and improved ease of global travel [...].

Preparation of the inactivated Newcastle disease vaccine by plasma activated water and evaluation of its protection efficacy

Vaccination has been regarded as the most effective way to reduce death and morbidity caused by infectious diseases in the livestock industry. In this study, plasma activated water (PAW) was introduced to prepare the inactivated Newcastle disease vaccine. Humoral immune response was tested by hemagglutination inhibition (HI) assay and enzyme-linked immunosorbent assay (ELISA). In addition, cell-mediated immune response was evaluated by lymphocyte proliferation assay and flow cytometry. The results demonstrated that the vaccine prepared by PAW at appropriate volume ratio could induce similar antibody titers in specific pathogen-free (SPF) chickens compared with the formaldehyde-inactivated vaccine. The challenge experiment further confirmed that the vaccine prepared by PAW conferred solid protection against virulent NDV. Moreover, it was found that the vaccine could promote the proliferation of lymphocytes and stimulate cell-mediated immunity of SPF chickens. Furthermore, analysis of electron spin resonance (ESR) spectroscopy and physicochemical properties of PAW suggested reactive oxygen and nitrogen species (RONS) played an essential role in the virus inactivation. Therefore, this study indicated that NDV treated by PAW in an appropriate ratio retained immunogenicity on the premise of virus inactivation. PAW as a promising strategy could be used to prepare inactivated vaccine for Newcastle disease.

Replication-Defective West Nile Virus with NS1 Deletion as a New Vaccine Platform for Flavivirus

We previously produced a replication-defective West Nile virus (WNV) lacking NS1 (WNV-ΔNS1) that could propagate at low levels (10⁵ infectious units [IU]/ml) in a 293T cell line expressing wild-type (WT) NS1. This finding indicates the potential of developing WNV-ΔNS1 as a noninfectious vaccine. To explore this idea, we developed an NS1-expressing Vero cell line (Vero_NS1) that significantly improved the yield of WNV-ΔNS1 (10⁸ IU/ml). We evaluated the safety and efficacy of WNV-ΔNS1 in mice. WNV-ΔNS1 appeared to be safe, as no replicative virus was found in naive Vero cells after continuous culturing of WNV-ΔNS1 in Vero_NS1 cells for 15 rounds. WNV-ΔNS1 was noninfectious in mice, even when IFNAR^-/- mice were administered a high dose of WNV-ΔNS1. Vaccination with a single dose of WNV-ΔNS1 protected mice from a highly lethal challenge with WT WNV. The antibody response against WNV correlated well with the protection of vaccinated mice. Our study demonstrates the potential of the NS1 trans complementation system as a new platform for flavivirus vaccine development.IMPORTANCE Many flaviviruses are significant human pathogens that frequently cause outbreaks and epidemics around the world. Development of novel vaccine platforms against these pathogens is a public health priority. Using WNV as a model, we developed a new vaccine platform for flaviviruses. WNV containing a NS1 deletion (WNV-ΔNS1) could be efficiently trans complemented in Vero cells that constitutively expressed WT NS1 protein. A single-dose immunization with WNV-ΔNS1 elicited robust immune responses in mice. The immunized animals were fully protected against pathogenic WNV infection. No adverse effects related to the WNV-ΔNS1 vaccination were observed. The results have demonstrated the potential of the NS1 complementation system as an alternative platform for flavivirus vaccine development, especially for highly pathogenic flaviviruses.

West Nile virus vaccines - current situation and future directions

West Nile virus (WNV) is a widely spread human pathogenic arthropod-borne virus. It can lead to severe, sometimes fatal, neurological disease. Over the last two decades, several vaccine candidates for the protection of humans from WNV have been developed. Some technologies were transferred into clinical testing, but these approaches have not yet led to a licensed product. This review summarizes the current status of a human WNV vaccine and discusses reasons for the lack of clinically advanced product candidates. It also discusses the problem of immunological cross-reactivity between flaviviruses and how it can be addressed during vaccine development.

Role of NS1 and TLR3 in Pathogenesis and Immunity of WNV

West Nile Virus (WNV) is a mosquito-transmitted flavivirus which causes encephalitis especially in elderly and immunocompromised individuals. Previous studies have suggested the protective role of the Toll-like receptor 3 (TLR3) pathway against WNV entry into the brain, while the WNV non-structural protein 1 (NS1) interferes with the TLR3 signaling pathway, besides being a component of viral genome replication machinery. In this study, we investigated whether immunization with NS1 could protect against WNV neuroinvasion in the context of TLR3 deficiency. We immunized mice with either an intact or deleted TLR3 system (TLR3KO) with WNV envelope glycoprotein (gE) protein, NS1, or a combination of gE and NS1. Immunization with gE or gE/NS1, but not with NS1 alone, induced WNV neutralizing antibodies and protected against WNV brain invasion and inflammation. The presence of intact TLR3 signaling had no apparent effect on WNV brain invasion. However, mock-immunized TLR3KO mice had higher inflammatory cell invasion upon WNV brain infection than NS1-immunized TLR3KO mice and wild type mice. Thus, immunization against NS1 may reduce brain inflammation in a context of TLR3 signaling deficiency.

Mouse Models of Heterologous Flavivirus Immunity: A Role for Cross-Reactive T Cells

Most of the world is at risk of being infected with a flavivirus such as dengue virus, West Nile virus, yellow fever virus, Japanese encephalitis virus, tick-borne encephalitis virus, and Zika virus, significantly impacting millions of lives. Importantly, many of these genetically similar viruses co-circulate within the same geographic regions, making it likely for individuals living in areas of high flavivirus endemicity to be infected with multiple flaviviruses during their lifetime. Following a flavivirus infection, a robust virus-specific T cell response is generated and the memory recall of this response has been demonstrated to provide long-lasting immunity, protecting against reinfection with the same pathogen. However, multiple studies have shown that this flavivirus specific T cell response can be cross-reactive and active during heterologous flavivirus infection, leading to the question: How does immunity to one flavivirus shape immunity to the next, and how does this impact disease? It has been proposed that in some cases unfavorable disease outcomes may be caused by lower avidity cross-reactive memory T cells generated during a primary flavivirus infection that preferentially expand during a secondary heterologous infection and function sub optimally against the new pathogen. While in other cases, these cross-reactive cells still have the potential to facilitate cross-protection. In this review, we focus on cross-reactive T cell responses to flaviviruses and the concepts and consequences of T cell cross-reactivity, with particular emphasis linking data generated using murine models to our new understanding of disease outcomes following heterologous flavivirus infection.

An observer blinded, randomized, placebo-controlled, phase I dose escalation trial to evaluate the safety and immunogenicity of an inactivated West Nile virus Vaccine, HydroVax-001, in healthy adults

Background

West Nile virus (WNV) is the most common mosquito-borne infection in the United States. HydroVax-001 WNV is a hydrogen peroxide inactivated, whole virion (WNV-Kunjin strain) vaccine adjuvanted with aluminum hydroxide.

Methods

We performed a phase 1, randomized, placebo-controlled, double-blind (within dosing group), dose escalation clinical trial of the HydroVax-001 WNV vaccine administered via intramuscular injection. This trial evaluated 1 mcg and 4 mcg dosages of HydroVax-001 WNV vaccine given intramuscularly on day 1 and day 29 in healthy adults. The two dosing groups of HydroVax-001 were enrolled sequentially and each group consisted of 20 individuals who received HydroVax-001 and 5 who received placebo. Safety was assessed at all study days (days 1, 2, 4 and 15 post dose 1, and days 1, 2, 4, 15, 29, 57, 180 and 365 post dose 2), and reactogenicity was assessed for 14 days after administration of each dose. Immunogenicity was measured by WNV-specific plaque reduction neutralization tests (PRNT₅₀) in the presence or absence of added complement or by WNV-specific enzyme-linked immunosorbent assays (ELISA).

Results

HydroVax-001 was safe and well-tolerated as there were no serious adverse events or concerning safety signals. At the 1 mcg dose, HydroVax-001 was not immunogenic by PRNT₅₀ but elicited up to 41% seroconversion by WNV-specific ELISA in the per-protocol population (PP) after the second dose. At the 4 mcg dose, HydroVax-001 elicited neutralizing antibody responses in 31% of the PP following the second dose. In the presence of added complement, PRNT₅₀ seroconversion rates increased to 50%, and 75% seroconversion was observed by WNV-specific ELISA.

Conclusions

The HydroVax-001 WNV vaccine was found to be modestly immunogenic and welltolerated at all dose levels.

Advanced oxidation technology for the development of a next-generation inactivated West Nile virus vaccine

West Nile virus (WNV) is the most frequent mosquito-borne disease reported in the continental United States and although an effective veterinary vaccine exists for horses, there is still no commercial vaccine approved for human use. We have previously tested a 3% hydrogen peroxide (H₂O₂)-based WNV inactivation approach termed, HydroVax, in Phase I clinical trials and the vaccine was found to be safe and modestly immunogenic. Here, we describe an advanced, next-generation oxidation approach (HydroVax-II) for the development of inactivated vaccines that utilizes reduced concentrations of H₂O₂ in combination with copper (cupric ions, Cu²⁺) complexed with the antiviral compound, methisazone (MZ). Further enhancement of this oxidative approach included the addition of a low percentage of formaldehyde, a cross-linking reagent with a different mechanism of action that, together with H₂O₂/Cu/MZ, provides a robust two-pronged approach to virus inactivation. Together, this new approach results in rapid virus inactivation while greatly improving the maintenance of WNV-specific neutralizing epitopes mapped across the three structural domains of the WNV envelope protein. In combination with more refined manufacturing techniques, this inactivation technology resulted in vaccine-mediated WNV-specific neutralizing antibody responses that were 130-fold higher than that observed using the first generation, H₂O₂-only vaccine approach and provided 100% protection against lethal WNV infection. This new approach to vaccine development represents an important area for future investigation with the potential not only for improving vaccines against WNV, but other clinically relevant viruses as well.

A combination of TLR-4 agonist and saponin adjuvants increases antibody diversity and protective efficacy of a recombinant West Nile Virus antigen

Members of the Flaviviridae family are the leading causes of mosquito-borne viral disease worldwide. While dengue virus is the most prevalent, the recent Zika virus outbreak in the Americas triggered a WHO public health emergency, and yellow fever and West Nile viruses (WNV) continue to cause regional epidemics. Given the sporadic nature of flaviviral epidemics both temporally and geographically, there is an urgent need for vaccines that can rapidly provide effective immunity. Protection from flaviviral infection is correlated with antibodies to the viral envelope (E) protein, which encodes receptor binding and fusion functions. TLR agonist adjuvants represent a promising tool to enhance the protective capacity of flavivirus vaccines through dose and dosage reduction and broadening of antiviral antibody responses. This study investigates the ability to improve the immunogenicity and protective capacity of a promising clinical-stage WNV recombinant E-protein vaccine (WN-80E) using a novel combination adjuvant, which contains a potent TLR-4 agonist and the saponin QS21 in a liposomal formulation (SLA-LSQ). Here, we show that, in combination with WN-80E, optimized SLA-LSQ is capable of inducing long-lasting immune responses in preclinical models that provide sterilizing protection from WNV challenge, reducing viral titers following WNV challenge to undetectable levels in Syrian hamsters. We have investigated potential mechanisms of action by examining the antibody repertoire generated post-immunization. SLA-LSQ induced a more diverse antibody response to WNV recombinant E-protein antigen than less protective adjuvants. Collectively, these studies identify an adjuvant formulation that enhances the protective capacity of recombinant flavivirus vaccines.

A plant-produced vaccine protects mice against lethal West Nile virus infection without enhancing Zika or dengue virus infectivity

West Nile virus (WNV) has caused multiple global outbreaks with increased frequency of neuroinvasive disease in recent years. Despite many years of research, there are no licensed therapeutics or vaccines available for human use. One of the major impediments of vaccine development against WNV is the potential enhancement of infection by related flaviviruses in vaccinated subjects through the mechanism of antibody-dependent enhancement of infection (ADE). For instance, the recent finding of enhancement of Zika virus (ZIKV) infection by pre-exposure to WNV further complicates the development of WNV vaccines. Epidemics of WNV and the potential risk of ADE by current vaccine candidates demand the development of effective and safe vaccines. We have previously reported that the domain III (DIII) of the WNV envelope protein can be readily expressed in Nicotiana benthamiana leaves, purified to homogeneity, and promote antigen-specific antibody response in mice. Herein, we further investigated the in vivo potency of a plant-made DIII (plant-DIII) in providing protective immunity against WNV infection. Furthermore, we examined if vaccination with plant-DIII would enhance the risk of a subsequent infection by ZIKV and Dengue virus (DENV). Plant-DIII vaccination evoked antigen-specific cellular immune responses as well as humoral responses. DIII-specific antibodies were neutralizing and the neutralization titers met the threshold correlated with protective immunity by vaccines against multiple flaviviruses. Furthermore, passive administration of anti-plant DIII mouse serum provided full protection against a lethal challenge of WNV infection in mice. Notably, plant DIII-induced antibodies did not enhance ZIKV and DENV infection in Fc gamma receptor-expressing cells, addressing the concern of WNV vaccines in inducing cross-reactive antibodies and sensitizing subjects to subsequent infection by heterologous flavivirus. This study provides the first report of a WNV subunit vaccine that induces protective immunity, while circumventing induction of antibodies with enhancing activity for ZIKV and DENV infection.

An Overview of Current Approaches Toward the Treatment and Prevention of West Nile Virus Infection

The persistence of West Nile virus (WNV) infections throughout the USA since its inception in 1999 and its continuous spread throughout the globe calls for an urgent need of effective treatments and prevention measures. Although the licensing of several WNV vaccines for veterinary use provides a proof of concept, similar efforts on the development of an effective vaccine for humans remain still unsuccessful. Increased understanding of biology and pathogenesis of WNV together with recent technological advancements have raised hope that an effective WNV vaccine may be available in the near future. In addition, rapid progress in the structural and functional characterization of WNV and other flaviviral proteins have provided a solid base for the design and development of several classes of inhibitors as potential WNV therapeutics. Moreover, the therapeutic monoclonal antibodies demonstrate an excellent efficacy against WNV in animal models and represent a promising class of WNV therapeutics. However, there are some challenges as to the design and development of a safe and efficient WNV vaccine or therapeutic. In this chapter, we discuss the current approaches, progress, and challenges toward the development of WNV vaccines, therapeutic antibodies, and antiviral drugs.

Protection of mice deficient in mature B cells from West Nile virus infection by passive and active immunization

B cell activating factor receptor (BAFFR)-/- mice have a profound reduction in mature B cells, but unlike μMT mice, they have normal numbers of newly formed, immature B cells. Using a West Nile virus (WNV) challenge model that requires antibodies (Abs) for protection, we found that unlike wild-type (WT) mice, BAFFR-/- mice were highly susceptible to WNV and succumbed to infection within 8 to 12 days after subcutaneous virus challenge. Although mature B cells were required to protect against lethal infection, infected BAFFR-/- mice had reduced WNV E-specific IgG responses and neutralizing Abs. Passive transfer of immune sera from previously infected WT mice rescued BAFFR-/- and fully B cell-deficient μMT mice, but unlike μMT mice that died around 30 days post-infection, BAFFR-/- mice survived, developed WNV-specific IgG Abs and overcame a second WNV challenge. Remarkably, protective immunity could be induced in mature B cell-deficient mice. Administration of a WNV E-anti-CD180 conjugate vaccine 30 days prior to WNV infection induced Ab responses that protected against lethal infection in BAFFR-/- mice but not in μMT mice. Thus, the immature B cells present in BAFFR-/- and not μMT mice contribute to protective antiviral immunity. A CD180-based vaccine may promote immunity in immunocompromised individuals.

Advanced oxidation and disinfection processes for onsite net-zero greywater reuse: A review

Net-zero greywater (NZGW) reuse, or nearly closed-loop recycle of greywater for all original uses, can recover both water and its attendant hot-water thermal energy, while avoiding the installation and maintenance of a separate greywater sewer in residential areas. Such a system, if portable, could also provide wash water for remote emergency health care units. However, such greywater reuse engenders human contact with the recycled water, and hence superior treatment. The purpose of this paper is to review processes applicable to the mineralization of organics, including control of oxidative byproducts such as bromate, and maintenance of disinfection consistent with potable reuse guidelines, in NZGW systems. Specifically, TiO₂-UV, UV-hydrogen peroxide, hydrogen peroxide-ozone, ozone-UV advanced oxidation processes, and UV, ozone, hydrogen peroxide, filtration, and chlorine disinfection processes were reviewed for performance, energy demand, environmental impact, and operational simplicity. Based on the literature reviewed, peroxone is the most energy-efficient process for organics mineralization. However, in portable applications where delivery of chemicals to the site is a concern, the UV-ozone process appears promising, at higher energy demand. In either case, reverse osmosis, nanofiltration, or ED may be useful in controlling the bromide precursor in make-up water, and a minor side-stream of ozone may be used to prevent microbial regrowth in the treated water. Where energy is not paramount, UV-hydrogen peroxide and UV-TiO₂ can be used to mineralize organics while avoiding bromate formation, but may require a secondary process to prevent microbial regrowth. Chlorine and ozone may be useful for maintenance of disinfection residual.

Progress and Works in Progress: Update on Flavivirus Vaccine Development

Most areas of the globe are endemic for at least one flavivirus, putting billions at risk for infection. This diverse group of viral pathogens causes a range of manifestations in humans from asymptomatic infection to hemorrhagic fever to encephalitis to birth defects and even death. Many flaviviruses are transmitted by mosquitos and have expanded in geographic distribution in recent years, with dengue virus being the most prevalent, infecting approximately 400 million people each year. The explosive emergence of Zika virus in Latin America in 2014 refocused international attention on this medically important group of viruses. Meanwhile, yellow fever has caused major outbreaks in Africa and South America since 2015 despite a reliable vaccine. There is no vaccine for Zika yet, and the only licensed dengue vaccine performs suboptimally in certain contexts. Further lessons are found when considering the experience with Japanese encephalitis virus, West Nile virus, and tickborne encephalitis virus, all of which now have protective vaccination in human or veterinary populations. Thus, vaccination is a mainstay of public health strategy for combating flavivirus infections; however, numerous challenges exist along the path from development to delivery of a tolerable and effective vaccine. Nevertheless, intensification of investment and effort in this area holds great promise for significantly reducing the global burden of disease attributable to flavivirus infection.

Inactivation of West Nile virus in serum with heat, ionic detergent, and reducing agent for proteomic applications

Research involving biosafety level 3 pathogens such as West Nile virus (WNV) is often limited by the limited space and technical constraints of these environments. To conduct complex analytical studies outside of high containment, robust and reliable inactivation methods are needed that maintain compatibility with downstream assays. Here we report the inactivation of WNV in spiked serum samples using a commercially available SDS-PAGE sample buffer for proteomic studies. Using this method, we demonstrate its utility by identification proteins differentially expressed in the serum of mice experimentally infected with WNV.

Pre-clinical development of a hydrogen peroxide-inactivated West Nile virus vaccine

West Nile virus (WNV) is a mosquito-transmitted pathogen with a wide geographical range that can lead to long-term disability and death in some cases. Despite the public health risk posed by WNV, including an estimated 3 million infections in the United States alone, no vaccine is available for use in humans. Here, we present a scaled manufacturing approach for production of a hydrogen peroxide-inactivated whole virion WNV vaccine, termed HydroVax-001WNV. Vaccination resulted in robust virus-specific neutralizing antibody responses and protection against WNV-associated mortality in mice or viremia in rhesus macaques (RM). A GLP-compliant toxicology study performed in rats demonstrated an excellent safety profile with clinical findings limited to minor and transient irritation at the injection site. An in vitro relative potency (IVRP) assay was developed and shown to correlate with in vivo responses following forced degradation studies. Long-term in vivo potency comparisons between the intended storage condition (2-8°C) and a thermally stressed condition (40±2°C) demonstrated no loss in vaccine efficacy or protective immunity over a 6-month span of time. Together, the positive pre-clinical findings regarding immunogenicity, safety, and stability indicate that HydroVax-001WNV is a promising vaccine candidate.

Computational predictions suggest that structural similarity in viral polymerases may lead to comparable allosteric binding sites

The identification of ligand-binding sites is often the first step in drug targeting and design. To date there are numerous computational tools available to predict ligand binding sites. These tools can guide or mitigate the need for experimental methods to identify binding sites, which often require significant resources and time. Here, we evaluate four ligand-binding site predictor (LBSP) tools for their ability to predict allosteric sites within the Hepatitis C Virus (HCV) polymerase. Our results show that the LISE LBSP is able to identify all three target allosteric sites within the HCV polymerase as well as a known allosteric site in the Coxsackievirus polymerase. LISE was then employed to identify novel binding sites within the polymerases of the Dengue, West Nile, and Foot-and-mouth Disease viruses. Our results suggest that all three viral polymerases have putative sites that share structural or chemical similarities with allosteric pockets of the HCV polymerase. Thus, these binding locations may represent an evolutionarily conserved structural feature of several viral polymerases that could be exploited for the development of small molecule therapeutics.

A Novel Synthetic TLR-4 Agonist Adjuvant Increases the Protective Response to a Clinical-Stage West Nile Virus Vaccine Antigen in Multiple Formulations

West Nile virus (WNV) is a mosquito-transmitted member of the Flaviviridae family that has emerged in recent years to become a serious public health threat. Given the sporadic nature of WNV epidemics both temporally and geographically, there is an urgent need for a vaccine that can rapidly provide effective immunity. Protection from WNV infection is correlated with antibodies to the viral envelope (E) protein, which encodes receptor binding and fusion functions. Despite many promising E-protein vaccine candidates, there are currently none licensed for use in humans. This study investigates the ability to improve the immunogenicity and protective capacity of a promising clinical-stage WNV recombinant E-protein vaccine (WN-80E) by combining it with a novel synthetic TLR-4 agonist adjuvant. Using the murine model of WNV disease, we find that inclusion of a TLR-4 agonist in either a stable oil-in-water emulsion (SE) or aluminum hydroxide (Alum) formulation provides both dose and dosage sparing functions, whereby protection can be induced after a single immunization containing only 100 ng of WN-80E. Additionally, we find that inclusion of adjuvant with a single immunization reduced viral titers in sera to levels undetectable by viral plaque assay. The enhanced protection provided by adjuvanted immunization correlated with induction of a Th1 T-cell response and the resultant shaping of the IgG response. These findings suggest that inclusion of a next generation adjuvant may greatly enhance the protective capacity of WNV recombinant subunit vaccines, and establish a baseline for future development.

Vaccines and Vaccination for Veterinary Viral Diseases: A General Overview

A high number of infectious diseases affecting livestock and companion animals are caused by pathogens of viral etiology. Ensuring the maximum standards of quality and welfare in animal production requires developing effective tools to halt and prevent the spread of those infectious diseases affecting animal husbandry. To date, one of the best strategies is to implement vaccination policies whenever possible. However many of the currently manufactured vaccines relies in classical vaccine technologies (killed or attenuated vaccines) which, under some circumstances, may not be optimal in terms of safety or adequate for widespread application in disease-free countries at risk of disease introduction. One step ahead is needed to improve and adapt vaccine manufacturing to the use of new generation vaccine technologies already tested in experimental settings. Here we present in the context of animal viral diseases of veterinary interest, an overview of some current vaccine technologies that can be approached for virus pathogens with a brief insight in the type of immunity elicited.

The Nucleoprotein Is Required for Lymphocytic Choriomeningitis Virus-Based Vaccine Vector Immunogenicity

Recombinant glycoprotein-deficient lymphocytic choriomeningitis virus-based vaccine vectors (rLCMV/ΔGP) are potent CD8(+) T cell inducers. To investigate the underlying molecular requirements, we generated a nucleoprotein-deficient vector counterpart (rLCMV/ΔNP). NP but not GP is a minimal trans-acting factor for viral transcription and genome replication. We found that, unlike rLCMV/ΔGP, rLCMV/ΔNP failed to elicit detectable CD8(+) T cell responses unless NP was trans complemented in a transgenic host. Hence, NP-dependent intracellular gene expression is essential for LCMV vector immunogenicity.

Age-Dependent Cell Trafficking Defects in Draining Lymph Nodes Impair Adaptive Immunity and Control of West Nile Virus Infection

Impaired immune responses in the elderly lead to reduced vaccine efficacy and increased susceptibility to viral infections. Although several groups have documented age-dependent defects in adaptive immune priming, the deficits that occur prior to antigen encounter remain largely unexplored. Herein, we identify novel mechanisms for compromised adaptive immunity that occurs with aging in the context of infection with West Nile virus (WNV), an encephalitic flavivirus that preferentially causes disease in the elderly. An impaired IgM and IgG response and enhanced vulnerability to WNV infection during aging was linked to delayed germinal center formation in the draining lymph node (DLN). Adoptive transfer studies and two-photon intravital microscopy revealed a decreased trafficking capacity of donor naïve CD4+ T cells from old mice, which manifested as impaired T cell diapedesis at high endothelial venules and reduced cell motility within DLN prior to antigen encounter. Furthermore, leukocyte accumulation in the DLN within the first few days of WNV infection or antigen-adjuvant administration was diminished more generally in old mice and associated with a second aging-related defect in local cytokine and chemokine production. Thus, age-dependent cell-intrinsic and environmental defects in the DLN result in delayed immune cell recruitment and antigen recognition. These deficits compromise priming of early adaptive immune responses and likely contribute to the susceptibility of old animals to acute WNV infection.

Technologies for the development of West Nile virus vaccines

West Nile virus (WNV), an emerging mosquito-borne and zoonotic flavivirus, continues to spread worldwide and represents a major problem for human and veterinary medicine. In recent years, severe outbreaks were observed in the USA and Europe with neighboring countries, and the virus is considered to be endemic in an increasing number of areas. Although most infections remain asymptomatic, WNV can cause severe, even fatal, neurological disease, which affects mostly the elderly and immunocompromised individuals. Several vaccines have been licensed in the veterinary sector, but no human vaccine is available today. This review summarizes recent strategies that are being followed to develop WNV vaccines with emphasis on technologies suitable for the use in humans.

Plant-made vaccines against West Nile virus are potent, safe, and economically feasible

The threat of West Nile virus (WNV) epidemics with increasingly severe neuroinvasive infections demands the development and licensing of effective vaccines. To date, vaccine candidates based on inactivated, live-attenuated, or chimeric virus, and viral DNA and WNV protein subunits have been developed. Some have been approved for veterinary use or are under clinical investigation, yet no vaccine has been licensed for human use. Reaching the milestone of a commercialized human vaccine, however, may largely depend on the economics of vaccine production. Analysis suggests that currently only novel low-cost production technologies would allow vaccination to outcompete the cost of surveillance and clinical treatment. Here, we review progress using plants to address the economic challenges of WNV vaccine production. The advantages of plants as hosts for vaccine production in cost, speed and scalability, especially those of viral vector-based transient expression systems, are discussed. The progress in developing WNV subunit vaccines in plants is reviewed within the context of their expression, characterization, downstream processing, and immunogenicity in animal models. The development of vaccines based on enveloped and non-enveloped virus-like particles is also discussed. These advancements suggest that plants may provide a production platform that offers potent, safe and affordable human vaccines against WNV.

Vaccines. An Ebola whole-virus vaccine is protective in nonhuman primates

Zaire ebolavirus is the causative agent of the current outbreak of hemorrhagic fever disease in West Africa. Previously, we showed that a whole Ebola virus (EBOV) vaccine based on a replication-defective EBOV (EBOVΔVP30) protects immunized mice and guinea pigs against lethal challenge with rodent-adapted EBOV. Here, we demonstrate that EBOVΔVP30 protects nonhuman primates against lethal infection with EBOV. Although EBOVΔVP30 is replication-incompetent, we additionally inactivated the vaccine with hydrogen peroxide; the chemically inactivated vaccine remained antigenic and protective in nonhuman primates. EBOVΔVP30 thus represents a safe, efficacious, whole-EBOV vaccine candidate that differs from other EBOV vaccine platforms in that it presents all viral proteins and the viral RNA to the host immune system, which might contribute to protective immune responses.

Risk factors for West Nile virus infection and disease in populations and individuals

West Nile virus (WNV) is a mosquito-borne enveloped positive-strand RNA virus that emerged in North America in 1999 in New York City. Over the past 15 years, WNV has become established throughout the USA and has spread into Canada, Mexico and the Caribbean. CDC reports indicate >41,000 clinical cases, including more than 1700 fatalities. An estimated 3 million people in the USA may have been infected to date. Infection with WNV is dependent on many factors including climate, mosquito habitats and immunologically naïve bird populations. In addition, variations within individuals contribute to the risk of severe disease, in particular, advanced age, hypertension, immunosuppression and critical elements of the immune response. Recent advances in technology now allow detailed analysis of complex immune interactions relevant to disease susceptibility.

T cell epitope mapping of the e-protein of West Nile virus in BALB/c mice

West Nile virus (WNV) is a zoonotic virus, which is transmitted by mosquitoes. It is the causative agent of the disease syndrome called West Nile fever. In some human cases, a WNV infection can be associated with severe neurological symptoms. The immune response to WNV is multifactorial and includes both humoral and cellular immunity. T-cell epitope mapping of the WNV envelope (E) protein has been performed in C57BL/6 mice, but not in BALB/c mice. Therefore, we performed in BALB/c mice a T-cell epitope mapping using a series of peptides spanning the WNV envelope (E) protein. To this end, the WNV-E specific T cell repertoire was first expanded by vaccinating BALB/c mice with a DNA vaccine that generates subviral particles that resemble West Nile virus. Furthermore, the WNV structural protein was expressed in Escherichia coli as a series of overlapping 20-mer peptides fused to a carrier-protein. Cytokine-based ELISPOT assays using these purified peptides revealed positive WNV-specific T cell responses to peptides within the different domains of the E-protein.

Mosaic RNA phage VLPs carrying domain III of the West Nile virus E protein

The virus-neutralising domain III (DIII) of the West Nile virus glycoprotein E was exposed on the surface of RNA phage AP205 virus-like particles (VLPs) in mosaic form. For this purpose, a 111 amino acid sequence of DIII was added via amber or opal termination codons to the C-terminus of the AP205 coat protein, and mosaic AP205-DIII VLPs were generated by cultivation in amber- or opal-suppressing Escherichia coli strains. After extensive purification to 95 % homogeneity, mosaic AP205-DIII VLPs retained up to 11-16 % monomers carrying DIII domains. The DIII domains appeared on the VLP surface because they were fully accessible to anti-DIII antibodies. Immunisation of BALB/c mice with AP205-DIII VLPs resulted in the induction of specific anti-DIII antibodies, of which the level was comparable to that of the anti-AP205 antibodies generated against the VLP carrier. The AP205-DIII-induced anti-DIII response was represented by a significant fraction of IgG2 isotype antibodies, in contrast to parallel immunisation with the DIII oligopeptide, which failed to induce IgG2 isotype antibodies. Formulation of AP-205-DIII VLPs in alum adjuvant stimulated the level of the anti-DIII response, but did not alter the fraction of IgG2 isotype antibodies. Mosaic AP205-DIII VLPs could be regarded as a promising prototype of a putative West Nile vaccine.

Vaccine-induced protection of rhesus macaques against plasma viremia after intradermal infection with a European lineage 1 strain of West Nile virus

The mosquito-borne West Nile virus (WNV) causes human and animal disease with outbreaks in several parts of the world including North America, the Mediterranean countries, Central and East Europe, the Middle East, and Africa. Particularly in elderly people and individuals with an impaired immune system, infection with WNV can progress into a serious neuroinvasive disease. Currently, no treatment or vaccine is available to protect humans against infection or disease. The goal of this study was to develop a WNV-vaccine that is safe to use in these high-risk human target populations. We performed a vaccine efficacy study in non-human primates using the contemporary, pathogenic European WNV genotype 1a challenge strain, WNV-Ita09. Two vaccine strategies were evaluated in rhesus macaques (Macaca mulatta) using recombinant soluble WNV envelope (E) ectodomain adjuvanted with Matrix-M, either with or without DNA priming. The DNA priming immunization was performed with WNV-DermaVir nanoparticles. Both vaccination strategies successfully induced humoral and cellular immune responses that completely protected the macaques against the development of viremia. In addition, the vaccine was well tolerated by all animals. Overall, The WNV E protein adjuvanted with Matrix-M is a promising vaccine candidate for a non-infectious WNV vaccine for use in humans, including at-risk populations.