Return of inactivated whole-virus vaccine for superior efficacy

Influenza Virus Inactivated by Heavy Ion Beam Irradiation Stimulates Antigen-Specific Immune Responses

The COVID-19 pandemic has made clear the need for effective and rapid vaccine development methods. Conventional inactivated virus vaccines, together with new technologies like vector and mRNA vaccines, were the first to be rolled out. However, the traditional methods used for virus inactivation can affect surface-exposed antigen, thereby reducing vaccine efficacy. Gamma rays have been used in the past to inactivate viruses. We recently proposed that high-energy heavy ions may be more suitable as an inactivation method because they increase the damage ratio between the viral nucleic acid and surface proteins. Here, we demonstrate that irradiation of the influenza virus using heavy ion beams constitutes a suitable method to develop effective vaccines, since immunization of mice by the intranasal route with the inactivated virus resulted in the stimulation of strong antigen-specific humoral and cellular immune responses.

Mucosal Application of a Low-Energy Electron Inactivated Respiratory Syncytial Virus Vaccine Shows Protective Efficacy in an Animal Model

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections in the elderly and in children, associated with pediatric hospitalizations. Recently, first vaccines have been approved for people over 60 years of age applied by intramuscular injection. However, a vaccination route via mucosal application holds great potential in the protection against respiratory pathogens like RSV. Mucosal vaccines induce local immune responses, resulting in a fast and efficient elimination of respiratory viruses after natural infection. Therefore, a low-energy electron irradiated RSV (LEEI-RSV) formulated with phosphatidylcholine-liposomes (PC-LEEI-RSV) was tested ex vivo in precision cut lung slices (PCLSs) for adverse effects. The immunogenicity and protective efficacy in vivo were analyzed in an RSV challenge model after intranasal vaccination using a homologous prime-boost immunization regimen. No side effects of PC-LEEI-RSV in PCLS and an efficient antibody induction in vivo could be observed. In contrast to unformulated LEEI-RSV, the mucosal vaccination of mice with PC formulated LEEI-RSV showed a statistically significant reduction in viral load after challenge. These results are a proof-of-principle for the use of LEEI-inactivated viruses formulated with liposomes to be administered intranasally to induce a mucosal immunity that could also be adapted for other respiratory viruses.

Fast-track development of vaccines for SARS-CoV-2: The shots that saved the world

In December 2019, an outbreak emerged of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which leads to coronavirus disease 2019 (COVID-19). The World Health Organisation announced the outbreak a global health emergency on 30 January 2020 and by 11 March 2020 it was declared a pandemic. The spread and severity of the outbreak took a heavy toll and overburdening of the global health system, particularly since there were no available drugs against SARS-CoV-2. With an immediate worldwide effort, communication, and sharing of data, large amounts of funding, researchers and pharmaceutical companies immediately fast-tracked vaccine development in order to prevent severe disease, hospitalizations and death. A number of vaccines were quickly approved for emergency use, and worldwide vaccination rollouts were immediately put in place. However, due to several individuals being hesitant to vaccinations and many poorer countries not having access to vaccines, multiple SARS-CoV-2 variants quickly emerged that were distinct from the original variant. Uncertainties related to the effectiveness of the various vaccines against the new variants as well as vaccine specific-side effects have remained a concern. Despite these uncertainties, fast-track vaccine approval, manufacturing at large scale, and the effective distribution of COVID-19 vaccines remain the topmost priorities around the world. Unprecedented efforts made by vaccine developers/researchers as well as healthcare staff, played a major role in distributing vaccine shots that provided protection and/or reduced disease severity, and deaths, even with the delta and omicron variants. Fortunately, even for those who become infected, vaccination appears to protect against major disease, hospitalisation, and fatality from COVID-19. Herein, we analyse ongoing vaccination studies and vaccine platforms that have saved many deaths from the pandemic.

Viral inactivation by light

Nowadays, viral infections are one of the greatest challenges for medical sciences and human society. While antiviral compounds and chemical inactivation remain inadequate, physical approaches based on irradiation provide new potentials for prevention and treatment of viral infections, without the risk of drug resistance and other unwanted side effects. Light across the electromagnetic spectrum can inactivate the virions using ionizing and non-ionizing radiations. This review highlights the anti-viral utility of radiant methods from the aspects of ionizing radiation, including high energy ultraviolet, gamma ray, X-ray, and neutron, and non-ionizing photo-inactivation, including lasers and blue light.

Influence of SARS-CoV-2 inactivation by different chemical reagents on the humoral response evaluated in a murine model

Viral inactivation for antibody induction purposes, among other applications, should ensure biosafety, completely avoiding the risk of infectivity, and preserving viral immunogenicity. β-propiolactone (BPL) is one of the most used reagents for viral inactivation, despite its high toxicity and recent difficulties related to importation, experienced in Brazil during the SARS-CoV-2 pandemic. In this context, the main objectives of this work were to test different inactivation procedures for SARS-CoV-2 and to evaluate the induction of neutralizing antibodies in mice immunized with antigenic preparations obtained after viral treatment with formaldehyde (FDE), glutaraldehyde (GDE), peroxide hydrogen (H₂O₂), as well as with viral proteins extract (VPE), in parallel with BPL. Verification of viral inactivation was performed by subsequent incubations of the inactivated virus in Vero cells, followed by cytopathic effect and lysis plaques observation, as well as by quantification of RNA load using reverse transcription-quantitative real time polymerase chain reaction. Once viral inactivation was confirmed, cell culture supernatants were concentrated and purified. In addition, an aliquot inactivated by BPL was also subjected to viral protein extraction (VPE). The different antigens were prepared using a previously developed microemulsion as adjuvant, and were administered in a four-dose immunization protocol. Antibody production was comparatively evaluated by ELISA and Plaque Reduction Neutralization Tests (PRNT). All immunogens evaluated showed some level of IgG anti-SARS-CoV-2 antibodies in the ELISA assay, with the highest levels presented by the group immunized with FDE-inactivated viral antigen. In the PRNT results, except for VPE-antigen, all other immunogens evaluated induced some level of neutralizing anti-SARS-CoV-2 antibodies, and the FDE-antigen stood out again with the most expressive values. Taken together, the present work shows that FDE can be an efficient and affordable alternative to BPL for the production of inactivated SARS-CoV-2 viral antigen.

Low-Energy Electron Irradiation of Tick-Borne Encephalitis Virus Provides a Protective Inactivated Vaccine

Tick-borne encephalitis virus (TBEV) is a zoonotic flavivirus which is endemic in many European and Asian countries. Humans can get infected with TBEV usually via ticks, and possible symptoms of the infection range from fever to severe neurological complications such as encephalitis. Vaccines to protect against TBEV-induced disease are widely used and most of them consist of whole viruses, which are inactivated by formaldehyde. Although this production process is well established, it has several drawbacks, including the usage of hazardous chemicals, the long inactivation times required and the potential modification of antigens by formaldehyde. As an alternative to chemical treatment, low-energy electron irradiation (LEEI) is known to efficiently inactivate pathogens by predominantly damaging nucleic acids. In contrast to other methods of ionizing radiation, LEEI does not require substantial shielding constructions and can be used in standard laboratories. Here, we have analyzed the potential of LEEI to generate a TBEV vaccine and immunized mice with three doses of irradiated or chemically inactivated TBEV. LEEI-inactivated TBEV induced binding antibodies of higher titer compared to the formaldehyde-inactivated virus. This was also observed for the avidity of the antibodies measured after the second dose. After viral challenge, the mice immunized with LEEI- or formaldehyde-inactivated TBEV were completely protected from disease and had no detectable virus in the central nervous system. Taken together, the results indicate that LEEI could be an alternative to chemical inactivation for the production of a TBEV vaccine.

Advances in Irradiated Livestock Vaccine Research and Production Addressing the Unmet Needs for Farmers and Veterinary Services in FAO/IAEA Member States

The Animal Production and Health section (APH) of the Joint FAO/IAEA Centre of Nuclear Techniques in Food and Agriculture at the International Atomic Energy Agency has over the last 58 years provided technical and scientific support to more than 100 countries through co-ordinated research activities and technical co-operation projects in peaceful uses of nuclear technologies. A key component of this support has been the development of irradiated vaccines targeting diseases that are endemic to participating countries. APH laboratories has over the last decade developed new techniques and has put in place a framework that allows researchers from participating member states to develop relevant vaccines targeting local diseases while using irradiation as a tool for improving livestock resources.

A global survey in the developmental landscape of possible vaccination strategies for COVID-19

The development of COVID-19 vaccines was promptly regulated to ensure the best possible approach. By January 2022, 75 candidates reached preclinical evaluation in various animal models, 114 vaccines were in clinical trials on humans, and 48 were in the final testing stages. Vaccine platforms range from whole virus vaccines to nucleic acid vaccines, which are the most promising in prompt availability and safety. The USA and Europe have approved vaccines developed by Pfizer-BioNTech (BNT162b2) and Moderna (mRNa1273). So far, Pfizer-BioNTech, Moderna, Johnson & Johnson, AstraZeneca-University of Oxford, Sinopharm, Sinovac Biotech Gamaleya, Bharat Biotech, and Novavax have documented effective vaccines. Even with technological advances and a fast-paced development approach, many limitations and problems need to be overcome before a large-scale production of new vaccines can start. The Key is to ensure equal and fair distribution globally through regulatory measures. Recent studies link Bacillus Calmette-Guérin (BCG) vaccination programs and lower disease severity.

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.

Leishmaniac Quest for Developing a Novel Vaccine Platform. Is a Roadmap for Its Advances Provided by the Mad Dash to Produce Vaccines for COVID-19?

“Bugs as drugs” in medicine encompasses the use of microbes to enhance the efficacy of vaccination, such as the delivery of vaccines by Leishmania—the protozoan etiological agent of leishmaniasis. This novel approach is appraised in light of the successful development of vaccines for Covid-19. All relevant aspects of this pandemic are summarized to provide the necessary framework in contrast to leishmaniasis. The presentation is in a side-by-side matching format with particular emphasis on vaccines. The comparative approach makes it possible to highlight the timeframe of the vaccine workflows condensed by the caveats of pandemic urgency and, at the same time, provides the background of Leishmania behind its use as a vaccine carrier. Previous studies in support of the latter are summarized as follows. Leishmaniasis confers life-long immunity on patients after cure, suggesting the effective vaccination is achievable with whole-cell Leishmania. A new strategy was developed to inactivate these cells in vitro, rendering them non-viable, hence non-disease causing, albeit retaining their immunogenicity and adjuvanticity. This was achieved by installing a dual suicidal mechanism in Leishmania for singlet oxygen (¹O₂)-initiated inactivation. In vitro cultured Leishmania were genetically engineered for cytosolic accumulation of UV-sensitive uroporphyrin I and further loaded endosomally with a red light-sensitive cationic phthalocyanine. Exposing these doubly dye-loaded Leishmania to light triggers intracellular production of highly reactive but extremely short-lived ¹O₂, resulting in their rapid and complete inactivation. Immunization of susceptible animals with such inactivated Leishmania elicited immunity to protect them against experimental leishmaniasis. Significantly, the inactivated Leishmania was shown to effectively deliver transgenically add-on ovalbumin (OVA) to antigen-presenting cells (APC), wherein OVA epitopes were processed appropriately for presentation with MHC molecules to activate epitope-specific CD8+ T cells. Application of this approach to deliver cancer vaccine candidates, e.g., enolase-1, was shown to suppress tumor development in mouse models. A similar approach is predicted to elicit lasting immunity against infectious diseases, including complementation of the spike protein-based vaccines in use for COVID-19. This pandemic is devastating, but brings to light the necessity of considering many facets of the disease in developing vaccination programs. Closer collaboration is essential among those in diverse disciplinary areas to provide the roadmap toward greater success in the future. Highlighted herein are several specific issues of vaccinology and new approaches worthy of consideration due to the pandemic.

Enhanced Immunogenicity of a Whole-Inactivated Influenza A Virus Vaccine Using Optimised Irradiation Conditions

Influenza A virus presents a constant pandemic threat due to the mutagenic nature of the virus and the inadequacy of current vaccines to protect against emerging strains. We have developed a whole-inactivated influenza vaccine using γ-irradiation (γ-Flu) that can protect against both vaccine-included strains as well as emerging pandemic strains. γ-irradiation is a widely used inactivation method and several γ-irradiated vaccines are currently in clinical or pre-clinical testing. To enhance vaccine efficacy, irradiation conditions should be carefully considered, particularly irradiation temperature. Specifically, while more damage to virus structure is expected when using higher irradiation temperatures, reduced radiation doses will be required to achieve sterility. In this study, we compared immunogenicity of γ-Flu irradiated at room temperature, chilled on ice or frozen on dry ice using different doses of γ-irradiation to meet internationally accepted sterility assurance levels. We found that, when irradiating at sterilising doses, the structural integrity and vaccine efficacy were well maintained in all preparations regardless of irradiation temperature. In fact, using a higher temperature and lower radiation dose appeared to induce higher neutralising antibody responses and more effective cytotoxic T cell responses. This outcome is expected to simplify irradiation protocols for manufacturing of highly effective irradiated vaccines.

Radiation-Inactivated S. gallinarum Vaccine Provides a High Protective Immune Response by Activating Both Humoral and Cellular Immunity

Salmonella enterica subsp. enterica serovar Gallinarum (SG) is a common pathogen in chickens, and causes an acute systemic disease that leads to high mortality. The live attenuated vaccine 9R is able to successfully protect chickens older than six weeks by activating a robust cell-mediated immune response, but its safety and efficacy in young chickens remains controversial. An inactivated SG vaccine is being used as an alternative, but because of its low cellular immune response, it cannot be used as a replacement for live attenuated 9R vaccine. In this study, we employed gamma irradiation instead of formalin as an inactivation method to increase the efficacy of the inactivated SG vaccine. Humoral, cellular, and protective immune responses were compared in both mouse and chicken models. The radiation-inactivated SG vaccine (r-SG) induced production of significantly higher levels of IgG2b and IgG3 antibodies than the formalin-inactivated vaccine (f-SG), and provided a homogeneous functional antibody response against group D, but not group B Salmonella. Moreover, we found that r-SG vaccination could provide a higher protective immune response than f-SG by inducing higher Th17 activation. These results indicate that r-SG can provide a protective immune response similar to the live attenuated 9R vaccine by activating a higher humoral immunity and a lower, but still protective, cellular immune response. Therefore, we expect that the radiation inactivation method might substitute for the 9R vaccine with little or no side effects in chickens younger than six weeks.

A Reduced Dose Whole Virion Aluminum Adjuvanted Seasonal Influenza Vaccine Is Immunogenic, Safe, and Well Tolerated in Pediatric Patients

BACKGROUND

Data suggest that pediatric patients might react differently to influenza vaccination, both in terms of immunity and side effects. We have recently shown that using a whole virion vaccine with aluminum phosphate adjuvants, reduced dose vaccines containing 6 µg of viral hemagglutinin (HA) per strain are immunogenic, and well tolerated in adult and elderly patients. Here we show the results of a multicenter clinical trial of pediatric patients, using reduced doses of a new, whole virion, aluminum phosphate adjuvanted vaccine (FluArt, Budapest, Hungary).

METHODS

A total of 120 healthy volunteers were included in two age groups (3-11 years, receiving 3 µg of HA per strain, and 12-18 years, receiving 6 µg of HA per strain). We used hemagglutination inhibition testing to assess immunogenicity, based on EMA and FDA licensing criteria, including post/pre-vaccination geometric mean titer ratios, seroconversion and seropositivity rates. Safety and tolerability were assessed using CHMP guidelines.

RESULTS

All subjects entered the study and were vaccinated (ITT population). All 120 subjects attended the control visit on Day 21 (PP population). All immunogenicity licensing criteria were met in both age groups for all three vaccine virus strains. No serious adverse events were detected and the vaccine was well tolerated by both age groups.

DISCUSSION

Using a whole virion vaccine and aluminum phosphate adjuvants, a reduction in the amount of the viral hemmaglutinin is possible while maintaining immunogenicity, safety and tolerability in pediatric and adolescent patients.

COVID-19: Diagnostics, Therapeutic Advances, and Vaccine Development

Purpose of Review

Human race is currently facing the wrath of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a highly transmittable and pathogenic RNA virus, causing coronavirus disease 2019 (COVID-19), the worst ever global pandemic. Coronaviruses (CoVs) have emerged as a major public health concern. Urgent global response to COVID-19 outbreak has been to limit spread of SARS-CoV-2 via extensive monitoring and containment. Various treatment regimens have been adopted to manage COVID-19, with known drugs and drug combinations used to decrease the morbidity and mortality associated with COVID-19. Intensive research on various fronts including studying molecular and structural aspects of these viruses and unraveling the pathophysiology and mechanistic basis of COVID-19 aimed at developing effective prophylactic, therapeutic agents and vaccines has been carried out globally.

Recent Findings

No approved antiviral treatment except remdesivir exists for SARS-CoV-2 till date though novel drug targets have been identified. However, worldwide frantic and competitive vaccine development pharmaceutical race has borne fruit in the form of a number of promising candidate vaccines, out of which few have already received emergency use authorization by regulatory bodies in record time.

Summary

This review highlights the painstaking efforts of healthcare workers and scientific community to successfully address the COVID-19 pandemic—though damage in the form of severe illness, loss of lives, and livelihood has left a serious mark. Focusing on extensive research on various therapeutic options and antiviral strategies including neutralizing antibodies, potential drugs, and drug targets, light has been shed on various diagnostic options and the amazing vaccine development process as well.

Adenoviral Vectors as Vaccines for Emerging Avian Influenza Viruses

It is evident that the emergence of infectious diseases, which have the potential for spillover from animal reservoirs, pose an ongoing threat to global health. Zoonotic transmission events have increased in frequency in recent decades due to changes in human behavior, including increased international travel, the wildlife trade, deforestation, and the intensification of farming practices to meet demand for meat consumption. Influenza A viruses (IAV) possess a number of features which make them a pandemic threat and a major concern for human health. Their segmented genome and error-prone process of replication can lead to the emergence of novel reassortant viruses, for which the human population are immunologically naïve. In addition, the ability for IAVs to infect aquatic birds and domestic animals, as well as humans, increases the likelihood for reassortment and the subsequent emergence of novel viruses. Sporadic spillover events in the past few decades have resulted in human infections with highly pathogenic avian influenza (HPAI) viruses, with high mortality. The application of conventional vaccine platforms used for the prevention of seasonal influenza viruses, such as inactivated influenza vaccines (IIVs) or live-attenuated influenza vaccines (LAIVs), in the development of vaccines for HPAI viruses is fraught with challenges. These issues are associated with manufacturing under enhanced biosafety containment, and difficulties in propagating HPAI viruses in embryonated eggs, due to their propensity for lethality in eggs. Overcoming manufacturing hurdles through the use of safer backbones, such as low pathogenicity avian influenza viruses (LPAI), can also be a challenge if incompatible with master strain viruses. Non-replicating adenoviral (Ad) vectors offer a number of advantages for the development of vaccines against HPAI viruses. Their genome is stable and permits the insertion of HPAI virus antigens (Ag), which are expressed in vivo following vaccination. Therefore, their manufacture does not require enhanced biosafety facilities or procedures and is egg-independent. Importantly, Ad vaccines have an exemplary safety and immunogenicity profile in numerous human clinical trials, and can be thermostabilized for stockpiling and pandemic preparedness. This review will discuss the status of Ad-based vaccines designed to protect against avian influenza viruses with pandemic potential.

SARS-CoV-2 Vaccines: Inactivation by Gamma Irradiation for T and B Cell Immunity

Despite accumulating preclinical data demonstrating a crucial role of cytotoxic T cell immunity during viral infections, ongoing efforts on developing COVID-19 vaccines are mostly focused on antibodies. In this commentary article, we discuss potential benefits of cytotoxic T cells in providing long-term protection against COVID-19. Further, we propose that gamma-ray irradiation, which is a previously tested inactivation method, may be utilized to prepare an experimental COVID-19 vaccine that can provide balanced immunity involving both B and T cells.

Automated application of low energy electron irradiation enables inactivation of pathogen- and cell-containing liquids in biomedical research and production facilities

Ionizing radiation is widely used to inactivate pathogens. It mainly acts by destroying nucleic acids but causes less damage to structural components like proteins. It is therefore highly suited for the sterilization of biological samples or the generation of inactivated vaccines. However, inactivation of viruses or bacteria requires relatively high doses and substantial amounts of radiation energy. Consequently, irradiation is restricted to shielded facilities—protecting personnel and the environment. We have previously shown that low energy electron irradiation (LEEI) has the same capacity to inactivate pathogens in liquids as current irradiation methods, but generates much less secondary X-ray radiation, which enables the use in normal laboratories by self-shielded irradiation equipment. Here, we present concepts for automated LEEI of liquids, in disposable bags or as a continuous process. As the electrons have a limited penetration depth, the liquid is transformed into a thin film. High concentrations of viruses (Influenza, Zika virus and Respiratory Syncytial Virus), bacteria (E. coli, B. cereus) and eukaryotic cells (NK-92 cell line) are efficiently inactivated by LEEI in a throughput suitable for various applications such as sterilization, vaccine manufacturing or cell therapy. Our results validate the premise that for pathogen and cell inactivation in liquids, LEEI represents a suitable and versatile irradiation method for standard biological research and production laboratories.

Characterization of humoral and cellular immune features of gamma-irradiated influenza vaccine

The most widely used influenza vaccines are prepared by chemical inactivation. However, chemical, especially formalin, treatment-induced modifications of the antigenic structure of the virus are frequently associated with adverse effects including low efficacy of protection, unexpected immune responses, or exacerbation of disease. Gamma-irradiation was suggested as an alternative influenza virus inactivation method due to its great features of completely inactivating virus while not damaging the structures of protein antigens, and cross-protective ability against heterologous strains. However, immunological features of gamma radiation-inactivated influenza vaccine have not been fully understood. In this study, we aimed to investigate the humoral and cellular immune responses of gamma radiation-inactivated influenza vaccine. The gamma irradiation-inactivated influenza vaccine (RADVAX_FluA) showed complete viral inactivation but retained normal viral structure with functional activities of viral protein antigens. Intranasal immunization of RADVAX_FluA provided better protection against influenza virus infection than formalin-inactivated influenza virus (FIV) in mice. RADVAX_FluA greatly enhanced the production of virus-specific serum IgG and alveolar mucosal IgA, which effectively neutralized HA (hemagglutinin) and NA (neuraminidase) activities, and blocked viral binding to the cells, respectively. Further analysis of IgG subclasses showed RADVAX_FluA-immunized sera had higher levels of IgG1 and IgG2a than those of FIV-immunized sera. In addition, analysis of cellular immunity found RADVAX_FluA induced strong dendritic cells (DC) activation resulting in higher DC-mediated activation of CD8⁺ T cells than FIV. The results support improved immunogenicity by RADVAX_FluA.

A review on Promising vaccine development progress for COVID-19 disease

The emergence of the strain of coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) that causes corona virus disease 2019 (COVID-19) and its impact on in the world have made imperative progress to develop an effective and safe vaccine. Despite several measures undertaken, the spread of this virus is ongoing. So far, more than 1,560,000 cases and 1000,000 deaths occurred in the world. Efforts have been made to develop vaccines against human coronavirus (CoV) infections such as MERS and SARS. However, currently, no approved vaccine exists for these coronavirus strains. Such Previous research efforts to develop a coronavirus vaccine in the years following the 2003 pandemic have opened the door for the scientist to design a new vaccine for the COVID-19. Both SARS-CoV and SARS-CoV-2 has a high degree of genetic similarity and bind to the same host cell ACE2 receptor. By using different vaccine development platforms including whole virus vaccines, recombinant protein subunit vaccines, and nucleic acid vaccines several candidates displayed efficacy in vitro studies but few progressed to clinical trials. This review provides a brief introduction of the general features of SARS-CoV-2 and discusses the current progress of ongoing advances in designing vaccine development efforts to counter COVID-19.

A review on Promising vaccine development progress for COVID-19 disease

The emergence of the strain of coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) that causes corona virus disease 2019 (COVID-19) and its impact on in the world have made imperative progress to develop an effective and safe vaccine. Despite several measures undertaken, the spread of this virus is ongoing. So far, more than 1,560,000 cases and 1000,000 deaths occurred in the world. Efforts have been made to develop vaccines against human coronavirus (CoV) infections such as MERS and SARS. However, currently, no approved vaccine exists for these coronavirus strains.

Such Previous research efforts to develop a coronavirus vaccine in the years following the 2003 pandemic have opened the door for the scientist to design a new vaccine for the COVID-19. Both SARS-CoV and SARS-CoV-2 has a high degree of genetic similarity and bind to the same host cell ACE2 receptor.

By using different vaccine development platforms including whole virus vaccines, recombinant protein subunit vaccines, and nucleic acid vaccines several candidates displayed efficacy in vitro studies but few progressed to clinical trials. This review provides a brief introduction of the general features of SARS-CoV-2 and discusses the current progress of ongoing advances in designing vaccine development efforts to counter COVID-19.

A novel gamma radiation-inactivated sabin-based polio vaccine

A concerted action on the part of international agencies and national governments has resulted in the near-eradication of poliomyelitis. However, both the oral polio vaccine (OPV) and the inactivated polio vaccine (IPV) have deficiencies which make them suboptimal for use after global eradication. OPV is composed of attenuated Sabin strains and stimulates robust immunity, but may revert to neurovirulent forms in the intestine which can be shed and infect susceptible contacts. The majority of IPV products are manufactured using pathogenic strains inactivated with formalin. Upon eradication, the production of large quantities of pathogenic virus will present an increased biosecurity hazard. A logical ideal endgame vaccine would be an inactivated form of an attenuated strain that could afford protective immunity while safely producing larger numbers of doses per unit of virus stock than current vaccines. We report here the development of an ionizing radiation (IR)-inactivated Sabin-based vaccine using a reconstituted Mn-decapeptide (MDP) antioxidant complex derived from the radioresistant bacterium Deinococcus radiodurans. In bacteria, Mn2+-peptide antioxidants protect proteins from oxidative damage caused by extreme radiation exposure. Here we show for the first time, that MDP can protect immunogenic neutralizing epitopes in picornaviruses. MDP protects epitopes in Polio Virus 1 and 2 Sabin strains (PV1-S and PV2-S, respectively), but viral genomic RNA is not protected during supralethal irradiation. IR-inactivated Sabin viruses stimulated equivalent or improved neutralizing antibody responses in Wistar rats compared to the commercially used IPV products. Our approach reduces the biosecurity risk of the current PV vaccine production method by utilizing the Sabin strains instead of the wild type neurovirulent strains. Additionally, the IR-inactivation approach could provide a simpler, faster and less costly process for producing a more immunogenic IPV. Gamma-irradiation is a well-known method of virus inactivation and this vaccine approach could be adapted to any pathogen of interest.

Inactivation methods for whole influenza vaccine production

Despite tremendous efforts toward vaccination, influenza remains an ongoing global threat. The induction of strain-specific neutralizing antibody responses is a common phenomenon during vaccination with the current inactivated influenza vaccines, so the protective effect of these vaccines is mostly strain-specific. There is an essential need for the development of next-generation vaccines, with a broad range of immunogenicity against antigenically drifted or shifted influenza viruses. Here, we evaluate the potential of whole inactivated vaccines, based on chemical and physical methods, as well as new approaches to generate cross-protective immune responses. We also consider the mechanisms by which some of these vaccines may induce CD8⁺ T-cells cross-reactivity with different strains of influenza. In this review, we have focused on conventional and novel methods for production of whole inactivated influenza vaccine. As well as chemical modification, using formaldehyde or β-propiolactone and physical manipulation by ultraviolet radiation or gamma-irradiation, novel approaches, including visible ultrashort pulsed laser, and low-energy electron irradiation are discussed. These two latter methods are considered to be attractive approaches to design more sophisticated vaccines, due to their ability to maintain most of the viral antigenic properties during inactivation and potential to produce cross-protective immunity. However, further studies are needed to validate them before they can replace traditional methods for vaccine manufacturing.

Imprinting and Editing of the Human CD4 T Cell Response to Influenza Virus

Immunity to influenza is unique among pathogens, in that immune memory is established both via intermittent lung localized infections with highly variable influenza virus strains and by intramuscular vaccinations with inactivated protein-based vaccines. Studies in the past decades have suggested that the B cell responses to influenza infection and vaccination are highly biased by an individual's early history of influenza infection. This reactivity likely reflects both the competitive advantage that memory B cells have in an immune response and the relatively limited diversity of epitopes in influenza hemagglutinin that are recognized by B cells. In contrast, CD4 T cells recognize a wide array of epitopes, with specificities that are heavily influenced by the diversity of influenza antigens available, and a multiplicity of functions that are determined by both priming events and subsequent confrontations with antigens. Here, we consider the events that prime and remodel the influenza-specific CD4 T cell response in humans that have highly diverse immune histories and how the CD4 repertoire may be edited in terms of functional potential and viral epitope specificity. We discuss the consequences that imprinting and remodeling may have on the potential of different human hosts to rapidly respond with protective cellular immunity to infection. Finally, these issues are discussed in the context of future avenues of investigation and vaccine strategies.

Cross-Protective Potential and Protection-Relevant Immune Mechanisms of Whole Inactivated Influenza Virus Vaccines Are Determined by Adjuvants and Route of Immunization

Adjuvanted whole inactivated virus (WIV) influenza vaccines show promise as broadly protective influenza vaccine candidates. Using WIV as basis we assessed the relative efficacy of different adjuvants by carrying out a head-to-head comparison of the liposome-based adjuvants CAF01 and CAF09 and the protein-based adjuvants CTA1-DD and CTA1-3M2e-DD and evaluated whether one or more of the adjuvants could induce broadly protective immunity. Mice were immunized with WIV prepared from A/Puerto Rico/8/34 (H1N1) virus intramuscularly with or without CAF01 or intranasally with or without CAF09, CTA1-DD, or CTA1-3M2e-DD, followed by challenge with homologous, heterologous or heterosubtypic virus. In general, intranasal immunizations were significantly more effective than intramuscular immunizations in inducing virus-specific serum-IgG, mucosal-IgA, and splenic IFNγ-producing CD4 T cells. Intranasal immunizations with adjuvanted vaccines afforded strong cross-protection with milder clinical symptoms and better control of virus load in lungs. Mechanistic studies indicated that non-neutralizing IgG antibodies and CD4 T cells were responsible for the improved cross-protection while IgA antibodies were dispensable. The role of CD4 T cells was particularly pronounced for CTA1-3M2e-DD adjuvanted vaccine as evidenced by CD4 T cell-dependent reduction of lung virus titers and clinical symptoms. Thus, intranasally administered WIV in combination with effective mucosal adjuvants appears to be a promising broadly protective influenza vaccine candidate.

Gamma-irradiation-killed Streptococcus pneumoniae potently induces the expression of IL-6 and IL-8 in human bronchial epithelial cells

Streptococcus pneumoniae is a major respiratory pathogen that can cause pneumonia, meningitis, and otitis media. Although capsular polysaccharide-based vaccines are commercially available, there is a need for broad-spectrum, serotype-independent, and cost-effective vaccines. Recently, an intranasal vaccine formulated with gamma-irradiated nonencapsulated S. pneumoniae whole cells has been developed and its immunogenicity is under investigation. Since innate immunity influences the subsequent adaptive immunity, in the present study, we investigated the immunostimulatory activity of gamma-irradiated S. pneumoniae (r-SP) in the human bronchial epithelial cell-line, BEAS-2B, by comparing with heat-inactivated S. pneumoniae (h-SP) and formalin-inactivated S. pneumoniae (f-SP). r-SP potently induced interleukin (IL)-6 and IL-8 at both mRNA and protein levels in a dose- and time-dependent manner, whereas h-SP and f-SP poorly induced them. Of note, the mRNA levels of IL-6 and IL-8 were approximately two-fold higher when cells were stimulated with 3 × 10⁷ CFU/ml of r-SP for 3 h, while the protein levels of IL-6 and IL-8 were approximately five-fold higher after stimulation with 3 × 10⁷ CFU/ml of r-SP for 24 h. Furthermore, r-SP exhibited potent activation of Toll-like receptor 2 compared with h-SP or f-SP. The expression of IL-6 and IL-8 induced by r-SP was mediated through the activation of mitogen-activated protein kinases. Remarkably, when r-SP was further treated with heat or formalin, there was a decrease in the aforementioned activities. Taken together, we suggest that r-SP stimulates the human respiratory epithelial cells to produce the cytokines IL-6 and IL-8, which might influence the induction of adaptive immune responses.

Seasonal influenza vaccine in immunocompromised persons

Immunocompromised persons are at high risk of complications from influenza infection. This population includes those with solid organ transplants, hematopoietic stem cell transplants, solid cancers and hematologic malignancy as well as those with autoimmune conditions receiving biologic therapies. In this review, we discuss the impact of influenza infection and evidence for vaccine effectiveness and immunogenicity. Overall, lower respiratory disease from influenza is common; however, vaccine immunogenicity is low. Despite this, in some populations, influenza vaccine has demonstrated effectiveness in reducing severe disease. Various strategies to improve influenza vaccine immunogenicity have been attempted including two vaccine doses in the same influenza season, intradermal, adjuvanted, and high-dose vaccines. The timing of influenza vaccine is also important to achieve optimal immunogenicity. Given the suboptimal immunogenicity, family members and healthcare professionals involved in the care of these populations should be vaccinated. Health care professional recommendation for vaccination is an important factor in vaccine coverage.

Opinion: Making Inactivated and Subunit-Based Vaccines Work

Empirically derived vaccines have in the past relied on the isolation and growth of disease-causing microorganisms that are then inactivated or attenuated before being administered. This is often done without prior knowledge of the mechanisms involved in conferring protective immunity. Recent advances in scientific technologies and in our knowledge of how protective immune responses are induced enable us to rationally design novel and safer vaccination strategies. Such advances have accelerated the development of inactivated whole-organism- and subunit-based vaccines. In this review, we discuss ideal attributes and criteria that need to be considered for the development of vaccines and some existing vaccine platforms. We focus on inactivated vaccines against influenza virus and ways by which vaccine efficacy can be improved with the use of adjuvants and Toll-like receptor-2 signaling.

Deinococcus Mn2+-peptide complex: A novel approach to alphavirus vaccine development

Over the last ten years, Chikungunya virus (CHIKV), an Old World alphavirus has caused numerous outbreaks in Asian and European countries and the Americas, making it an emerging pathogen of great global health importance. Venezuelan equine encephalitis virus (VEEV), a New World alphavirus, on the other hand, has been developed as a bioweapon in the past due to its ease of preparation, aerosol dispersion and high lethality in aerosolized form. Currently, there are no FDA approved vaccines against these viruses. In this study, we used a novel approach to develop inactivated vaccines for VEEV and CHIKV by applying gamma-radiation together with a synthetic Mn-decapeptide-phosphate complex (MnDpPi), based on manganous-peptide-orthophosphate antioxidants accumulated in the extremely radiation-resistant bacterium Deinococcus radiodurans. Classical gamma-irradiated vaccine development approaches are limited by immunogenicity-loss due to oxidative damage to the surface proteins at the high doses of radiation required for complete virus-inactivation. However, addition of MnDpPi during irradiation process selectively protects proteins, but not the nucleic acids, from the radiation-induced oxidative damage, as required for safe and efficacious vaccine development. Previously, this approach was used to develop a bacterial vaccine. In the present study, we show that this approach can successfully be applied to protecting mice against viral infections. Irradiation of VEEV and CHIKV in the presence of MnDpPi resulted in substantial epitope preservation even at supra-lethal doses of gamma-rays (50,000Gy). Irradiated viruses were found to be completely inactivated and safe in vivo (neonatal mice). Upon immunization, VEEV inactivated in the presence of MnDpPi resulted in drastically improved protective efficacy. Thus, the MnDpPi-based gamma-inactivation approach described here can readily be applied to developing vaccines against any pathogen of interest in a fast and cost-effective manner.

Dose sparing and the lack of a dose-response relationship with an influenza vaccine in adult and elderly patients - a randomized, double-blind clinical trial

AIMS

The currently licensed seasonal trivalent influenza vaccines contain 15 μg haemagglutinin per strain for adult, and up to 60 μg for elderly patients. However, due to recent shortages, dose sparing to increase production capacity would be highly desirable. In the present study, we attempted to find a dose-response relationship for immunogenicity and, thus, the optimal dose for seasonal influenza vaccines in adult and elderly patients.

METHODS

A total of 256 subjects, including adult (aged 18-60 years) and elderly (aged over 60 years) individuals, were enrolled. Subjects were randomly assigned in a 1:1:1:1 ratio to receive a whole-virion, aluminium-adjuvanted trivalent influenza vaccine containing 3.5, 6, 9 or 15 μg haemagglutinin of seasonal A/H1N1, A/H3N2 and B influenza antigens manufactured by Omninvest Ltd., Hungary. Serum antibody titres against the vaccine virus strains were measured by haemagglutination inhibition.

RESULT

All vaccines were well tolerated. All four vaccines fulfilled all three immunogenicity licensing criteria, as determined by the European Committee for Proprietary Medicinal Products (CPMP)/Biotechnology Working Party (BWP)/214/96 guideline for all three virus strains and both age groups. The 3.5 μg vaccine showed 28% less seroconversion compared to the 15 μg dose in terms of influenza AH3N2 in the adult group (95% confidence interval -51, -3; P < 0.05). All other doses showed no significant difference in immunogenicity compared with the licensed vaccine containing 15 μg haemagglutinin.

CONCLUSIONS

Our data suggested that significant dose sparing is possible with the use of whole-virion vaccines and aluminium adjuvants, without compromising safety. This could have significant economic and public health impacts.

Pathogens Inactivated by Low-Energy-Electron Irradiation Maintain Antigenic Properties and Induce Protective Immune Responses

Inactivated vaccines are commonly produced by incubating pathogens with chemicals such as formaldehyde or β-propiolactone. This is a time-consuming process, the inactivation efficiency displays high variability and extensive downstream procedures are often required. Moreover, application of chemicals alters the antigenic components of the viruses or bacteria, resulting in reduced antibody specificity and therefore stimulation of a less effective immune response. An alternative method for inactivation of pathogens is ionizing radiation. It acts very fast and predominantly damages nucleic acids, conserving most of the antigenic structures. However, currently used irradiation technologies (mostly gamma-rays and high energy electrons) require large and complex shielding constructions to protect the environment from radioactivity or X-rays generated during the process. This excludes them from direct integration into biological production facilities. Here, low-energy electron irradiation (LEEI) is presented as an alternative inactivation method for pathogens in liquid solutions. LEEI can be used in normal laboratories, including good manufacturing practice (GMP)- or high biosafety level (BSL)-environments, as only minor shielding is necessary. We show that LEEI efficiently inactivates different viruses (influenza A (H3N8), porcine reproductive and respiratory syndrome virus (PRRSV), equine herpesvirus 1 (EHV-1)) and bacteria (Escherichia coli) and maintains their antigenicity. Moreover, LEEI-inactivated influenza A viruses elicit protective immune responses in animals, as analyzed by virus neutralization assays and viral load determination upon challenge. These results have implications for novel ways of developing and manufacturing inactivated vaccines with improved efficacy.

Self-Amplifying mRNA Vaccines Expressing Multiple Conserved Influenza Antigens Confer Protection against Homologous and Heterosubtypic Viral Challenge

Current hemagglutinin (HA)-based seasonal influenza vaccines induce vaccine strain-specific neutralizing antibodies that usually fail to provide protection against mismatched circulating viruses. Inclusion in the vaccine of highly conserved internal proteins such as the nucleoprotein (NP) and the matrix protein 1 (M1) was shown previously to increase vaccine efficacy by eliciting cross-reactive T-cells. However, appropriate delivery systems are required for efficient priming of T-cell responses. In this study, we demonstrated that administration of novel self-amplifying mRNA (SAM^®) vectors expressing influenza NP (SAM(NP)), M1 (SAM(M1)), and NP and M1 (SAM(M1-NP)) delivered with lipid nanoparticles (LNP) induced robust polyfunctional CD4 T helper 1 cells, while NP-containing SAM also induced cytotoxic CD8 T cells. Robust expansions of central memory (T_CM) and effector memory (T_EM) CD4 and CD8 T cells were also measured. An enhanced recruitment of NP-specific cytotoxic CD8 T cells was observed in the lungs of SAM(NP)-immunized mice after influenza infection that paralleled with reduced lung viral titers and pathology, and increased survival after homologous and heterosubtypic influenza challenge. Finally, we demonstrated for the first time that the co-administration of RNA (SAM(M1-NP)) and protein (monovalent inactivated influenza vaccine (MIIV)) was feasible, induced simultaneously NP-, M1- and HA-specific T cells and HA-specific neutralizing antibodies, and enhanced MIIV efficacy against a heterologous challenge. In conclusion, systemic administration of SAM vectors expressing conserved internal influenza antigens induced protective immune responses in mice, supporting the SAM^® platform as another promising strategy for the development of broad-spectrum universal influenza vaccines.

A heat-inactivated H7N3 vaccine induces cross-reactive cellular immunity in HLA-A2.1 transgenic mice

BACKGROUND

Cross-reactive immunity against heterologous strains of influenza virus has the potential to provide partial protection in individuals that lack the proper neutralizing antibodies. In particular, the boosting of memory CD8+ T cell responses to conserved viral proteins can attenuate disease severity caused by influenza virus antigenic variants or pandemic strains. However, little is yet known about which of these conserved internal antigens would better induce and/or recall memory CD8+ T cells after in vivo administration of an inactivated whole virus vaccine.

METHODS

We explored the CD8 + T cell responses to selected epitopes of the internal proteins of an H7N3 influenza virus that were cross-reactive with A/PR/8/34 virus in HLA-A2.1 transgenic (AAD) mice.

RESULTS

CD8+ T cells against dominant and subdominant epitopes were detected upon infection of mice with live H7N3 virus, whereas immunization with non-replicating virus elicited CD8+ T cell responses against mostly immunodominant epitopes, which were rapidly recalled following infection with A/PR/8/34 virus. These vaccine-induced T cell responses were able to reduce the lung viral load in mice challenged intranasally with the heterologous influenza virus.

CONCLUSIONS

A single immunization with non-replicating influenza virus vaccines may be able to elicit or recall cross-reactive CD8+ T cell responses to conserved immunodominant epitopes and, to some extent, counteract an infection by heterologous virus.

Administration of Poly[di(sodium carboxylatoethylphenoxy)phosphazene] (PCEP) and Avian Beta Defensin as Adjuvants in Inactivated Inclusion Body Hepatitis Virus and its Hexon Protein-Based Experimental Vaccine Formulations in Chickens

Inclusion body hepatitis (IBH) is one of the major infectious diseases adversely affecting the poultry industry of the United States and Canada. Currently, no effective and safe vaccine is available for the control of IBH virus (IBHV) infection in chickens. However, based on the excellent safety and immunogenic profiles of experimental veterinary vaccines developed with the use of new generation adjuvants, we hypothesized that characterization of vaccine formulations containing inactivated IBHV or its capsid protein hexon as antigens, along with poly[di(sodium carboxylatoethylphenoxy)phosphazene] (PCEP) and avian beta defensin 2 (ABD2) as vaccine adjuvants, will be helpful in development of an effective and safe vaccine formulation for IBH. Our data demonstrated that experimental administration of vaccine formulations containing inactivated IBHV and a mixture of PCEP with or without ABD2 as an adjuvant induced significantly higher antibody responses compared with other vaccine formulations, while hexon protein-based vaccine formulations showed relatively lower levels of antibody responses. Thus, a vaccine formulation containing inactivated IBHV with PCEP or a mixture of PCEP and ABD2 (with a reduced dosage of PCEP) as an adjuvant may serve as a potential vaccine candidate. However, in order to overcome the risks associated with whole virus inactivated vaccines, characterization of additional viral capsid proteins, including fiber protein and penton of IBHV along with hexon protein in combination with more new generation adjuvants, will be helpful in further improvements of vaccines against IBHV infection.

Prospects for Broadly Protective Influenza Vaccines

The development of vaccines that could provide broad protection against antigenically variant influenza viruses has long been the ultimate prize in influenza research. Recent developments have pushed us closer to this goal, and such vaccines may now be within reach. This brief review outlines the current approaches to broadly protective vaccines, and the probable hurdles and roadblocks to achieving this goal.

A New Adjuvant Combined with Inactivated Influenza Enhances Specific CD8 T Cell Response in Mice and Decreases Symptoms in Swine Upon Challenge

Vaccination is the most effective way to control swine influenza virus (SIV) in the field. Classical vaccines are based on inactivated antigens formulated with an oil emulsion or a polymeric adjuvant. Standard adjuvants enhance the humoral response and orient the immune response toward a Th2 response. An important issue is that current vaccines do not protect against new strains. One approach to improve cross-protection is to enhance Th1 and cytotoxic responses. The development of adjuvants orienting the immune response of inactivated vaccines toward Th1/Cytotoxic responses would be highly beneficial. This study shows that the water in oil in water emulsion adjuvant Montanide™ ISA 201 VG allows the induction of anti-influenza CD8 T cell in mice and induces homologous protection against an H1N1 challenge in swine. Such adjuvants that induce both humoral and cell-mediated immunity could improve the protection conferred by SIV vaccines in the field.

Laser vaccine adjuvants. History, progress, and potential

Immunologic adjuvants are essential for current vaccines to maximize their efficacy. Unfortunately, few have been found to be sufficiently effective and safe for regulatory authorities to permit their use in vaccines for humans and none have been approved for use with intradermal vaccines. The development of new adjuvants with the potential to be both efficacious and safe constitutes a significant need in modern vaccine practice. The use of non-damaging laser light represents a markedly different approach to enhancing immune responses to a vaccine antigen, particularly with intradermal vaccination. This approach, which was initially explored in Russia and further developed in the US, appears to significantly improve responses to both prophylactic and therapeutic vaccines administered to the laser-exposed tissue, particularly the skin. Although different types of lasers have been used for this purpose and the precise molecular mechanism(s) of action remain unknown, several approaches appear to modulate dendritic cell trafficking and/or activation at the irradiation site via the release of specific signaling molecules from epithelial cells. The most recent study, performed by the authors of this review, utilized a continuous wave near-infrared laser that may open the path for the development of a safe, effective, low-cost, simple-to-use laser vaccine adjuvant that could be used in lieu of conventional adjuvants, particularly with intradermal vaccines. In this review, we summarize the initial Russian studies that have given rise to this approach and comment upon recent advances in the use of non-tissue damaging lasers as novel physical adjuvants for vaccines.

Development of cross-protective influenza a vaccines based on cellular responses

Seasonal influenza vaccines provide protection against matching influenza A virus (IAV) strains mainly through the induction of neutralizing serum IgG antibodies. However, these antibodies fail to confer a protective effect against mismatched IAV. This lack of efficacy against heterologous influenza strains has spurred the vaccine development community to look for other influenza vaccine concepts, which have the ability to elicit cross-protective immune responses. One of the concepts that is currently been worked on is that of influenza vaccines inducing influenza-specific T cell responses. T cells are able to lyse infected host cells, thereby clearing the virus. More interestingly, these T cells can recognize highly conserved epitopes of internal influenza proteins, making cellular responses less vulnerable to antigenic variability. T cells are therefore cross-reactive against many influenza strains, and thus are a promising concept for future influenza vaccines. Despite their potential, there are currently no T cell-based IAV vaccines on the market. Selection of the proper antigen, appropriate vaccine formulation and evaluation of the efficacy of T cell vaccines remains challenging, both in preclinical and clinical settings. In this review, we will discuss the current developments in influenza T cell vaccines, focusing on existing protein-based and novel peptide-based vaccine formulations. Furthermore, we will discuss the feasibility of influenza T cell vaccines and their possible use in the future.

Inactivated Viral Vaccines

Inactivated vaccines have been used for over a century to induce protection against viral pathogens. This established approach of vaccine production is relatively straightforward to achieve and there is an augmented safety profile as compared to their live counterparts. Today, there are six viral pathogens for which licensed inactivated vaccines are available with many more in development. Here, we describe the principles of viral inactivation and the application of these principles to vaccine development. Specifically emphasized are the manufacturing procedure and the accompanying assays, of which assays used for monitoring the inactivation process and preservation of neutralizing epitopes, are pivotal. Novel inactivated vaccines in development and the hurdles they face for licensure are also discussed as well as the (dis)advantages of inactivation over the other vaccine production methodologies.

Membrane-bound IL-12 and IL-23 serve as potent mucosal adjuvants when co-presented on whole inactivated influenza vaccines

BACKGROUND

Potent and safe adjuvants are needed to improve the efficacy of parenteral and mucosal vaccines. Cytokines, chemokines and growth factors have all proven to be effective immunomodulatory adjuvants when administered with a variety of antigens. We have previously evaluated the efficacy of membrane-anchored interleukins (IL) such as IL-2 and IL-4 co-presented as Cytokine-bearing Influenza Vaccines (CYT-IVACs) using a mouse model of influenza challenge.

FINDINGS

Here, we describe studies evaluating the parenteral and mucosal adjuvanticity of membrane-bound IL-12 and IL-23 CYT-IVACs in young adult mice. Mucosal immunization using IL-12 and IL-23 bearing whole influenza virus vaccine (WIV) was more effective at eliciting virus-specific nasal IgA and reducing viral lung burden following challenge compared to control WIV vaccinated animals. Both IL-12 and IL-23 bearing WIV elicited the highest anti-viral IgA levels in serum and nasal washes.

CONCLUSIONS

This study highlights for the first time the mucosal adjuvant potential of IL-12 and IL-23 CYT-IVAC formulations in eliciting mucosal immune responses and reducing viral lung burden. The co-presentation of immunomodulators in direct context with viral antigen in whole inactivated viral vaccines may provide a means to significantly lower the dose of vaccine required for protection.

Near-infrared laser adjuvant for influenza vaccine

Safe and effective immunologic adjuvants are often essential for vaccines. However, the choice of adjuvant for licensed vaccines is limited, especially for those that are administered intradermally. We show that non-tissue damaging, near-infrared (NIR) laser light given in short exposures to small areas of skin, without the use of additional chemical or biological agents, significantly increases immune responses to intradermal influenza vaccination without augmenting IgE. The NIR laser-adjuvanted vaccine confers increased protection in a murine influenza lethal challenge model as compared to unadjuvanted vaccine. We show that NIR laser treatment induces the expression of specific chemokines in the skin resulting in recruitment and activation of dendritic cells and is safe to use in both mice and humans. The NIR laser adjuvant technology provides a novel, safe, low-cost, simple-to-use, potentially broadly applicable and clinically feasible approach to enhancing vaccine efficacy as an alternative to chemical and biological adjuvants.

Ebolavirus nucleoprotein C-termini potently attract single domain antibodies enabling monoclonal affinity reagent sandwich assay (MARSA) formulation

BACKGROUND

Antigen detection assays can play an important part in environmental surveillance and diagnostics for emerging threats. We are interested in accelerating assay formulation; targeting the agents themselves to bypass requirements for a priori genome information or surrogates. Previously, using in vitro affinity reagent selection on Marburg virus we rapidly established monoclonal affinity reagent sandwich assay (MARSA) where one recombinant antibody clone was both captor and tracer for polyvalent nucleoprotein (NP). Hypothesizing that the closely related Ebolavirus genus may share the same Achilles' heel, we redirected the scheme to see whether similar assays could be delivered and began to explore their mechanism.

METHODS AND FINDINGS

In parallel we selected panels of llama single domain antibodies (sdAb) from a semi-synthetic library against Zaire, Sudan, Ivory Coast, and Reston Ebola viruses. Each could perform as both captor and tracer in the same antigen sandwich capture assay thereby forming MARSAs. All sdAb were specific for NP and those tested required the C-terminal domain for recognition. Several clones were cross-reactive, indicating epitope conservation across the Ebolavirus genus. Analysis of two immune shark sdAb revealed they also targeted the C-terminal domain, and could be similarly employed, yet were less sensitive than a comparable llama sdAb despite stemming from immune selections.

CONCLUSIONS

The C-terminal domain of Ebolavirus NP is a strong attractant for antibodies and enables sensitive sandwich immunoassays to be rapidly generated using a single antibody clone. The polyvalent nature of nucleocapsid borne NP and display of the C-terminal region likely serves as a bountiful affinity sink during selections, and a highly avid target for subsequent immunoassay capture. Combined with the high degree of amino acid conservation through 37 years and across wide geographies, this domain makes an ideal handle for monoclonal affinity reagent driven antigen sandwich assays for the Ebolavirus genus.