Intranasal flu vaccine protective against seasonal and H5N1 avian influenza infections

Mucosal immunization with a low-energy electron inactivated respiratory syncytial virus vaccine protects mice without Th2 immune bias

The respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections associated with numerous hospitalizations. Recently, intramuscular (i.m.) vaccines against RSV have been approved for elderly and pregnant women. Noninvasive mucosal vaccination, e.g., by inhalation, offers an alternative against respiratory pathogens like RSV. Effective mucosal vaccines induce local immune responses, potentially resulting in the efficient and fast elimination of respiratory viruses after natural infection. To investigate this immune response to an RSV challenge, low-energy electron inactivated RSV (LEEI-RSV) was formulated with phosphatidylcholine-liposomes (PC-LEEI-RSV) or 1,2-dioleoyl-3-trimethylammonium-propane and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DD-LEEI-RSV) for vaccination of mice intranasally. As controls, LEEI-RSV and formalin-inactivated-RSV (FI-RSV) were used via i.m. vaccination. The RSV-specific immunogenicity of the different vaccines and their protective efficacy were analyzed. RSV-specific IgA antibodies and a statistically significant reduction in viral load upon challenge were detected in mucosal DD-LEEI-RSV-vaccinated animals. Alhydrogel-adjuvanted LEEI-RSV i.m. showed a Th2-bias with enhanced IgE, eosinophils, and lung histopathology comparable to FI-RSV. These effects were absent when applying the mucosal vaccines highlighting the potential of DD-LEEI-RSV as an RSV vaccine candidate and the improved performance of this mucosal vaccine candidate.

Comparison of vaccination efficacy using live or ultraviolet-inactivated influenza viruses introduced by different routes in a mouse model

Influenza is a major cause of highly contagious respiratory illness resulting in high mortality and morbidity worldwide. Annual vaccination is an effective way to prevent infection and complication from constantly mutating influenza strains. Vaccination utilizes preemptive inoculation with live virus, live attenuated virus, inactivated virus, or virus segments for optimal immune activation. The route of administration also affects the efficacy of the vaccination. Here, we evaluated the effects of inoculation with ultraviolet (UV)-inactivated or live influenza A virus strains and compared their effectiveness and cross protection when intraperitoneal and intramuscular routes of administration were used in mice. Intramuscular or intraperitoneal inoculation with UV-inactivated Influenza A/WSN/1933 provided some protection against intranasal challenge with a lethal dose of live Influenza A/WSN/1933 but only when a high dose of the virus was used in the inoculation. By contrast, inoculation with a low dose of live virus via either route provided complete protection against the same intranasal challenge. Intraperitoneal inoculation with live or UV-inactivated Influenza A/Philippines/2/1982 and intramuscular inoculation with UV-inactivated Influenza A/Philippines/2/1982 failed to produce cross-reactive antibodies against Influenza A/WSN/1933. Intramuscular inoculation with live Influenza A/Philippines/2/1982 induced small amounts of cross-reactive antibodies but could not suppress the cytokine storm produced upon intranasal challenge with Influenza A/WSN/1993. None of the tested inoculation conditions provided observable cross protection against intranasal challenge with a different influenza strain. Taken together, vaccination efficacy was affected by the state and dose of the vaccine virus and the route of administration. These results provide practical data for the development of effective vaccines against influenza virus.

Carboxymethyl chitosan bounded iron oxide nanoparticles and gamma-irradiated avian influenza subtype H9N2 vaccine to development of immunity on mouse and chicken

BACKGROUND

Avian influenza virus (AIV) subtype H9N2 is a low pathogenic avian influenza virus (LPAIV).

OBJECTIVE

This study aims to evaluate the humoral and cellular immunity in vaccinated mice and broiler chicken by irradiated AIV antigen plus carboxymethyl chitosan bounded iron oxide nanoparticles (CMC-IO NPs) as an adjuvant.

METHODS

AIV subtype H9N2 with 108.5 EID50 /ml and haemagglutinin antigen assay about 10 log2 was irradiated by 30 kGy gamma radiation dose. Then, the gamma-irradiated AIV was used as an inactivated vaccine and conjugated with CMC-IO NPs to improve immune responses on mice. IO NPs must be applied in all activated tests using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysulfosuccinimide sodium salt (sulfo-NHS), and then functionalized by CMC as IO-CMC. Fourier transform infrared (FTIR) spectra on functionalized IO-CMC showed a peak of 638 cm-1 which is a band between metal and O (Fe-O).

RESULTS

Based on the comparison between the two X-ray diffraction (XRD) patterns on Fe2 O3 -NPs and IO-CMC, the characteristics of IO-NPs did not change after carboxymethylation. A CHN Analyzer was applied to measure the molecular weight of IO-CMC that was calculated as 1045 g. IO-CMC, irradiated AIV-IO-CMC and formalin AIV-IO-CMC were injected into 42 BALB/c mice in six groups. The fourth group was the negative control, and the fifth and sixth groups were inoculated by irradiated AIV-ISA70 and formalin AIV-ISA70 vaccines. An increase in haemagglutination inhibition (HI) antibody titration was observed in the irradiated AIV-IO-CMC and formalin AIV-IO-CMC groups (p < 0.05). In addition, increases in the lymphoproliferative activity of re-stimulated splenic lymphocytes, interfron-γ (IFN-γ) and interleukin-2 (IL-2) concentration in the irradiated AIV-IO-CMC group demonstrated the activation of Type 1 helper cells. The concentration of IL-4 was without any significant increases in non-group.

CONCLUSIONS

Accordingly, Th2 activation represented no increase. Finally, the finding showed that AIV-IO-CMC was effective on enhancing immunogenicity as irradiated AIV antigen administered with a clinically acceptable adjuvant (i.e. IO-CMC).

Ionizing Radiation Technologies for Vaccine Development - A Mini Review

Given the current pandemic the world is struggling with, there is an urgent need to continually improve vaccine technologies. Ionizing radiation technology has a long history in the development of vaccines, dating back to the mid-20th century. Ionizing radiation technology is a highly versatile technology that has a variety of commercial applications around the world. This brief review summarizes the core technology, the overall effects of ionizing radiation on bacterial cells and reviews vaccine development efforts using ionizing technologies, namely gamma radiation, electron beam, and X-rays.

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.

A formulated poly (I:C)/CCL21 as an effective mucosal adjuvant for gamma-irradiated influenza vaccine

BACKGROUND

Several studies on gamma-irradiated influenza A virus (γ-Flu) have revealed its superior efficacy for inducing homologous and heterologous virus-specific immunity. However, many inactivated vaccines, notably in nasal delivery, require adjuvants to increase the quality and magnitude of vaccine responses.

METHODS

To illustrate the impacts of co-administration of the gamma-irradiated H1N1 vaccine with poly (I:C) and recombinant murine CCL21, either alone or in combination with each other, as adjuvants on the vaccine potency, mice were inoculated intranasally 3 times at one-week interval with γ-Flu alone or with any of the three adjuvant combinations and then challenged with a high lethal dose (10 LD50) of A/PR/8/34 (H1N1) influenza virus. Virus-specific humoral, mucosal, and cell-mediated immunity, as well as cytokine profiles in the spleen (IFN-γ, IL-12, and IL-4), and in the lung homogenates (IL-6 and IL-10) were measured by ELISA. The proliferative response of restimulated splenocytes was also determined by MTT assay.

RESULTS

The findings showed that the co-delivery of the γ-Flu vaccine and CCL21 or Poly (I:C) significantly increased the vaccine immunogenicity compared to the non-adjuvanted vaccine, associated with more potent protection following challenge infection. However, the mice given a combination of CCL21 with poly (I:C) had strong antibody- and cell-mediated immunity, which were considerably higher than responses of mice receiving the γ-Flu vaccine with each adjuvant separately. This combination also reduced inflammatory mediator levels (notably IL-10) in lung homogenate samples.

CONCLUSIONS

The results indicate that adjuvantation with the CCL21 and poly (I:C) can successfully induce vigorous vaccine-mediated protection, suggesting a robust propensity for CCL21 plus poly (I:C) as a potent mucosal adjuvant.

Controlling the Colonization of Clostridium perfringens in Broiler Chickens by an Electron-Beam-Killed Vaccine

Clostridium perfringens (Cp) is a Gram-positive anaerobe that is one of the causative agents of necrotic enteritis (NE) in chickens, which leads to high mortality. Owing to the ban of administering antibiotics in feed to chickens, there has been an increase in the number of NE outbreaks all over the world, and the estimated loss is approximately 6 billion U.S. dollars. The best alternative method to control NE without antibiotics could be vaccination. In this study, we exposed three different strains of Cp to electron beam (eBeam) irradiation to inactivate them and then used them as a killed vaccine to control the colonization of Cp in broiler chickens. The vaccine was delivered to 18-day old embryos in ovo and the chickens were challenged with the respective vaccine strain at two different time points (early and late) to test the protective efficacy of the vaccine. The results indicate that an effective eBeam dose of 10 kGy inactivated all three strains of Cp, did not affect the cell membrane or epitopes, induced significant levels of IgY in the vaccinated birds, and further reduced the colonization of Cp strains significantly (p < 0.0001) in late challenge (JGS4064: 4 out of 10; JGS1473: 0 out of 10; JGS4104: 3 out of 10). Further studies are necessary to enhance the efficacy of the vaccine and to understand the mechanism of vaccine protection.

Protective cellular and mucosal immune responses following nasal administration of a whole gamma-irradiated influenza A (subtype H1N1) vaccine adjuvanted with interleukin-28B in a mouse model

The use of gamma-irradiated influenza A virus (γ-Flu), retains most of the viral structural antigens, represent a promising option for vaccine development. However, despite the high effectiveness of γ-Flu vaccines, the need to incorporate an adjuvant to improve vaccine-mediated protection seems inevitable. Here, we examined the protective efficacy of an intranasal gamma-irradiated HIN1 vaccine co-administered with a plasmid encoding mouse interleukin-28B (mIL-28B) as a novel adjuvant in BALB/c mice. Animals were immunized intranasally three times at one-week intervals with γ-Flu, alone or in combination with the mIL-28B adjuvant, followed by viral challenge with a high lethal dose (10 LD₅₀) of A/PR/8/34 (H1N1) influenza virus. Virus-specific antibody, cellular and mucosal responses, and the balance of cytokines in the spleen IFN-γ, IL-12, and IL-4) and in lung homogenates (IL-6 and IL-10) were measured by ELISA. The lymphoproliferative activity of restimulated spleen cells was also determined by MTT assay. Furthermore, virus production in the lungs of infected mice was estimated using the Madin-Darby canine kidney (MDCK)/hemagglutination assay (HA). Our data showed that intranasal immunization with adjuvanted γ-Flu vaccine efficiently promoted humoral, cellular, and mucosal immune responses and efficiently decreased lung virus titers, all of which are associated with protection against challenge. This combination also reduced IL-6 and IL-10 levels in lung homogenates. The results suggest that IL-28B can enhance the ability of the vaccine to elicit virus-specific immune responses and could potentially be used as an effective adjuvant.

Reduction of viral load of avian influenza A virus (H9N2) on SPF eggs and cell line by gamma irradiation

Avian influenza A H9N2 viruses are circulating in domestic poultry worldwide. In this research a low-pathogenic AIV H9N2 was multiplied on MDCK cell line and SPF eggs and irradiated by a Nordian gamma cell instrument. Irradiated and non-irradiated AIV samples were titrated by TCID50 and EID50 methods, respectively. Haemagglutinin antigen was analysed by Haemagglutinin test. Infectivi­ty of irradiated virus samples was determined by cell culture and egg inoculation methods. The virus titration decreased as the dose of gamma radiation increased. AIV proliferation on cell culture can be inactivated by gamma irradiation at a lower dose of gamma-ray (20 kGy) than the virus inactivation on embryonated eggs (30 kGy). The safety test showed complete inactivation of AIV on allantoic fluid with gamma-ray doses: 30 kGy and 20 kGy for virus on MDCK cells after four blind cultures.

Proteomic Analysis of Vesicle-Producing Pseudomonas aeruginosa PAO1 Exposed to X-Ray Irradiation

Ionizing irradiation kills pathogens by destroying nucleic acids without protein structure destruction. However, how pathogens respond to irradiation stress has not yet been fully elucidated. Here, we observed that Pseudomonas aeruginosa PAO1 could release nucleic acids into the extracellular environment under X-ray irradiation. Using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), X-ray irradiation was observed to induce outer membrane vesicle (OMV) formation in P. aeruginosa PAO1. The size distribution of the OMVs of the irradiated PAO1 was similar to that of the OMVs of the non-irradiated PAO1 according to nanoparticle tracking analysis (NTA). The pyocin-related proteins are involved in OMV production in P. aeruginosa PAO1 under X-ray irradiation conditions, and that this is regulated by the key SOS gene recA. The OMV production was significantly impaired in the irradiated PAO1 Δlys mutant, suggesting that Lys endolysin is associated with OMV production in P. aeruginosa PAO1 upon irradiation stress. Meanwhile, no significant difference in OMV production was observed between PAO1 lacking the pqsR, lasR, or rhlR genes and the parent strain, demonstrating that the irradiation-induced OMV biosynthesis of P. aeruginosa was independent of the Pseudomonas quinolone signal (PQS).

Sterility of gamma-irradiated pathogens: a new mathematical formula to calculate sterilizing doses

In recent years there has been increasing advocacy for highly immunogenic gamma-irradiated vaccines, several of which are currently in clinical or pre-clinical trials. Importantly, various methods of mathematical modelling and sterility testing are employed to ensure sterility. However, these methods are designed for materials with a low bioburden, such as food and pharmaceuticals. Consequently, current methods may not be reliable or applicable to estimate the irradiation dose required to sterilize microbiological preparations for vaccine purposes, where bioburden is deliberately high. In this study we investigated the applicability of current methods to calculate the sterilizing doses for different microbes. We generated inactivation curves that demonstrate single-hit and multiple-hit kinetics under different irradiation temperatures for high-titre preparations of pathogens with different genomic structures. Our data demonstrate that inactivation of viruses such as Influenza A virus, Zika virus, Semliki Forest virus and Newcastle Disease virus show single-hit kinetics following exposure to gamma-irradiation. In contrast, rotavirus inactivation shows multiple-hit kinetics and the sterilizing dose could not be calculated using current mathematical methods. Similarly, Streptococcus pneumoniae demonstrates multiple-hit kinetics. These variations in killing curves reveal an important gap in current mathematical formulae to determine sterility assurance levels. Here we propose a simple method to calculate the irradiation dose required for a single log10 reduction in bioburden (D10) value and sterilizing doses, incorporating both single- and multiple-hit kinetics, and taking into account the possible existence of a resistance shoulder for some pathogens following exposure to gamma-irradiation.

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.

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.

Development of Universal Influenza Vaccines Targeting Conserved Viral Proteins

Vaccination is still the most efficient way to prevent an infection with influenza viruses. Nevertheless, existing commercial vaccines face serious limitations such as availability during epidemic outbreaks and their efficacy. Existing seasonal influenza vaccines mostly induce antibody responses to the surface proteins of influenza viruses, which frequently change due to antigenic shift and or drift, thus allowing influenza viruses to avoid neutralizing antibodies. Hence, influenza vaccines need a yearly formulation to protect against new seasonal viruses. A broadly protective or universal influenza vaccine must induce effective humoral as well as cellular immunity against conserved influenza antigens, offer good protection against influenza pandemics, be safe, and have a fast production platform. Nanotechnology has great potential to improve vaccine delivery, immunogenicity, and host immune responses. As new strains of human epidemic influenza virus strains could originate from poultry and swine viruses, development of a new universal influenza vaccine will require the immune responses to be directed against viruses from different hosts. This review discusses how the new vaccine platforms and nanoparticles can be beneficial in the development of a broadly protective, universal influenza vaccine.

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.

Peritoneal Cells Mediate Immune Responses and Cross-Protection Against Influenza A Virus

Intraperitoneal inoculation with live influenza A virus confers protection against intranasal infections in mice and ferrets. However, the responses of peritoneal cells to influenza A virus have not been investigated. Here we show that intraperitoneal inoculation with A/WSN/1933 (H1N1) virus induced virus-reactive IgG production in the peritoneal cavity in mice. The infection resulted in substantial but transient B cell and macrophage depletion along with massive neutrophil infiltration, but virus growth was not detected. Influenza A viruses bound to α-2,6-linked sialic acids of B cells and macrophages and induced apoptotic death of peritoneal cavity cells. However, re-infection with A/WSN/1933 virus did not have adverse effects on immune cells most likely because of the neutralizing antibodies produced in response to the first exposure. Infection of BALB/c mice with A/WSN/1933 induced cross-protection against an otherwise lethal intraperitoneal dose of A/Hongkong/4801/2014 (H3N2) virus. This information suggests that immunological responses in the peritoneal cavity can induce effective defense against future virus infection. Considering the unexpected potent immunoregulatory activity of the peritoneal cells against influenza viruses, we suggest that comparative studies on various immune reactions after infection through different routes may contribute to better selection of vaccination routes in development of efficacious influenza vaccines.

Direct interaction of whole-inactivated influenza A and pneumococcal vaccines enhances influenza-specific immunity

The upper respiratory tract is continuously exposed to a vast array of potentially pathogenic viruses and bacteria. Influenza A virus (IAV) has particular synergism with the commensal bacterium Streptococcus pneumoniae in this niche, and co-infection exacerbates pathogenicity and causes significant mortality. However, it is not known whether this synergism is associated with a direct interaction between the two pathogens. We have previously reported that co-administration of a whole-inactivated IAV vaccine (γ-Flu) with a whole-inactivated pneumococcal vaccine (γ-PN) enhances pneumococcal-specific responses. In this study, we show that mucosal co-administration of γ-Flu and γ-PN similarly augments IAV-specific immunity, particularly tissue-resident memory cell responses in the lung. In addition, our in vitro analysis revealed that S. pneumoniae directly interacts with both γ-Flu and with live IAV, facilitating increased uptake by macrophages as well as increased infection of epithelial cells by IAV. These observations provide an additional explanation for the synergistic pathogenicity of IAV and S. pneumoniae, as well as heralding the prospect of exploiting the phenomenon to develop better vaccine strategies for both pathogens.

Gamma-irradiated rotavirus: A possible whole virus inactivated vaccine

Rotavirus (RV) causes significant morbidity and mortality in developing countries, where children and infants are highly susceptible to severe disease symptoms. While live attenuated vaccines are available, reduced vaccine efficacy in developing countries illustrates the need for highly immunogenic alternative vaccines. Here, we studied the possible inactivation of RV using gamma(γ)-irradiation, and assessed the sterility and immunogenicity of γ-irradiated RV (γ-RV) as a novel vaccine candidate. Interestingly, the inactivation curve of RV did not show a log-linear regression following exposure to increased doses of γ-rays, and consequently the radiation dose required to achieve the internationally accepted Sterility Assurance Level could not be calculated. Nonetheless, we performed sterility testing based on serial passages of γ-RV, and our data clearly illustrate the lack of infectivity of γ-RV preparations irradiated with 50 kGy. In addition, we tested the immunogenicity of 50 kGy γ-RV in mice and our data illustrate the induction of strong RV-specific neutralising antibody responses following administration of γ-RV without using adjuvant. Therefore, whilst γ-RV may not constitute a replacement for current RV vaccines, this study represents a proof-of-concept that γ-irradiation can be applied to inactivate RV for vaccine purposes. Further investigation will be required to address whether γ-irradiation can be applied to improve safety and efficacy of existing live attenuated vaccines.

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.

The effect of gamma-irradiation conditions on the immunogenicity of whole-inactivated Influenza A virus vaccine

Gamma-irradiation, particularly an irradiation dose of 50kGy, has been utilised widely to sterilise highly pathogenic agents such as Ebola, Marburg Virus, and Avian Influenza H5N1. We have reported previously that intranasal vaccination with a gamma-irradiated Influenza A virus vaccine (γ-Flu) results in cross-protective immunity. Considering the possible inclusion of highly pathogenic Influenza strains in future clinical development of γ-Flu, an irradiation dose of 50kGy may be used to enhance vaccine safety beyond the internationally accepted Sterility Assurance Level (SAL). Thus, we investigated the effect of irradiation conditions, including high irradiation doses, on the immunogenicity of γ-Flu. Our data confirm that irradiation at low temperatures (using dry-ice) is associated with reduced damage to viral structure compared with irradiation at room temperature. In addition, a single intranasal vaccination with γ-Flu irradiated on dry-ice with either 25 or 50kGy induced seroconversion and provided complete protection against lethal Influenza A challenge. Considering that low temperature is expected to reduce the protein damage associated with exposure to high irradiation doses, we titrated the vaccine dose to verify the efficacy of 50kGy γ-Flu. Our data demonstrate that exposure to 50kGy on dry-ice is associated with limited effect on vaccine immunogenicity, apparent only when using very low vaccine doses. Overall, our data highlight the immunogenicity of influenza virus irradiated at 50kGy for induction of high titre antibody and cytotoxic T-cell responses. This suggests these conditions are suitable for development of γ-Flu vaccines based on highly pathogenic Influenza A viruses.

Enhanced protective responses to a serotype-independent pneumococcal vaccine when combined with an inactivated influenza vaccine

Streptococcus pneumoniae and influenza are the world's foremost bacterial and viral respiratory pathogens. We have previously described a γ-irradiated influenza A virus (γ-FLU) vaccine that provides cross-protective immunity against heterosubtypic infections. More recently, we reported a novel non-adjuvanted γ-irradiated S pneumoniae (γ-PN) vaccine that elicits serotype-independent protection. Considering the clinical synergism of both pathogens, combination of a serotype-independent pneumococcal vaccine with a broad-spectrum influenza vaccine to protect against both infections would have a considerable clinical impact. In the present study, we co-immunized C57BL/6 mice intranasally (IN) with a mixture of γ-PN (whole inactivated cells) and γ-FLU (whole inactivated virions) and examined protective efficacy. Co-immunization enhanced γ-PN vaccine efficacy against virulent pneumococcal challenge, which was dependent on CD4⁺ T-cell responses. In contrast, vaccination with γ-PN alone, co-immunization enhanced pneumococcal-specific effector T-helper 17 cell (Th17) and Th1 memory cell, promoted development of CD4⁺ tissue-resident memory (TRM) cells and enhanced Pneumococcus-specific antibody responses. Furthermore, co-immunization elicited significant protection against lethal influenza challenge, as well as against co-infection with both influenza and S pneumoniae. This is the first report showing the synergistic effect of combining whole cell and whole virion vaccines to both S pneumoniae and influenza as a single vaccine to protect against individual and co-infection, without compromising pathogen-specific immunity.

Sterilizing immunity to influenza virus infection requires local antigen-specific T cell response in the lungs

Sterilizing immunity is a unique immune status, which prevents effective virus infection into the host. It is different from the immunity that allows infection but with subsequent successful eradication of the virus. Pre-infection induces sterilizing immunity to homologous influenza virus challenge in ferret. In our antigen-specific experimental system, mice pre-infected with PR8 influenza virus through nasal route are likewise resistant to reinfection of the same strain of virus. The virus is cleared before establishment of effective infection. Intramuscular influenza virus injection confers protection against re-infection with facilitated virus clearance but not sterilizing immunity. Pre-infection and intramuscular injection generates comparable innate immunity and antibody response, but only pre-infection induces virus receptor reduction and efficient antigen-specific T cell response in the lungs. Pre-infection with nH1N1 influenza virus induces virus receptor reduction but not PR8-specific T cell immune response in the lungs and cannot prevent infection of PR8 influenza virus. Pre-infection with PR8 virus induced PR8-specific T cell response in the lungs but cannot prevent infection of nH1N1 virus either. These results reveal that antigen-specific T cell immunity is required for sterilizing immunity.

Possible Impact of Yearly Childhood Vaccination With Trivalent Inactivated Influenza Vaccine (TIV) on the Immune Response to the Pandemic Strain H1N1

BACKGROUND

Annual vaccination of children against seasonal influenza with trivalent inactivated influenza vaccine (TIV) has shown to be beneficial. However, this yearly practice may have unintended effect. Studies have shown that infection with wild type influenza A viruses can stimulate protective heterotypic immunity against unrelated or new influenza subtypes. We hypothesized that a consequence of yearly TIV vaccination is lack of induction of heterotypic immunity against the recent H1N1 pandemic.

METHODS

This was a retrospective case-control study. We reviewed the medical records of polymerase chain reaction-confirmed cases of 2009 H1N1 influenza infection in children 6 months to 18 years and a matched control group seen during the pandemic.

RESULTS

We identified 353 polymerase chain reaction-confirmed H1N1 cases and 396 matching control subjects. Among the H1N1 group, 202/353 (57%) cases received a total of 477 doses of seasonal TIV compared with 218/396 (55%) in the control group who received a total of 435 doses. Seasonal TIV uptake was significantly higher in the H1N1 group 477/548 (87%) than in the control group, 435/532 (81%) (P = .017).

CONCLUSION

Seasonal TIV uptake was significantly higher in H1N1-infected group. The finding suggests that the practice of yearly vaccination with TIV might have negatively affected the immune response against the novel pandemic H1N1 strain. Given the rarity of pandemic novel influenza viruses, and the high predictability of seasonal influenza occurrence, the practice of yearly influenza vaccination should be continued. However, the use of live attenuated intranasal vaccine, as opposed to TIV, may allow for the desirable development of a vigorous heterotypic immune response against future pandemics.

X-ray Irradiated Vaccine Confers protection against Pneumonia caused by Pseudomonas aeruginosa

Pseudomonas aeruginosa is a gram-negative bacterium and one of the leading causes of nosocomial infection worldwide, however, no effective vaccine is currently available in the market. Here, we demonstrate that inactivation of the bacteria by X-ray irradiation inhibits its replication capability but retained antigenic expression functionally thus allowing its use as a potential vaccine. Mice immunized by this vaccine were challenged by the parental strain, the O-antigen-homologous strain PAO-1 (O2/O5) and heterologous strain PAO-6 (O6) in an acute pneumonia model. We further measured the protective effect of the vaccine, as well as host innate and cellular immunity responses. We found immunized mice could protect against both strains. Notably, the antiserum only had significant protective role against similar bacteria, while adoptive transfer of lymphocytes significantly controlled the spread of the virulent heterologous serogroup PAO-6 infection, and the protective role could be reversed by CD4 rather than CD8 antibody. We further revealed that vaccinated mice could rapidly recruit neutrophils to the airways early after intranasal challenge by PAO-6, and the irradiated vaccine was proved to be protective by the generated CD4(+) IL-17(+) Th17 cells. In conclusion, the generation of inactivated but metabolically active microbes is a promising strategy for safely vaccinating against Pseudomonas aeruginosa.

Development of Protective Immunity against Inactivated Iranian Isolate of Foot-and-Mouth Disease Virus Type O/IRN/2007 Using Gamma Ray-Irradiated Vaccine on BALB/c Mice and Guinea Pigs

OBJECTIVES

Foot-and-mouth disease virus (FMDV) causes a highly contagious disease in cloven-hoofed animals and is the most damaging disease of livestock worldwide, leading to great economic losses. The aim of this research was the inactivation of FMDV type O/IRN/1/2007 to produce a gamma ray-irradiated (GRI) vaccine in order to immunize mice and guinea pigs.

METHODS

In this research, the Iranian isolated FMDV type O/IRN/1/2007 was irradiated by gamma ray to prepare an inactivated whole virus antigen and formulated as a GRI vaccine with unaltered antigenic characteristics. Immune responses against this vaccine were evaluated on mice and guinea pigs.

RESULTS

The comparison of the immune responses between the GRI vaccine and conventional vaccine did not show any significant difference in neutralizing antibody titer, memory spleen T lymphocytes or IFN-γ, IL-4, IL-2 and IL-10 concentrations (p > 0.05). In contrast, there were significant differences in all of the evaluated immune factors between the two vaccinated groups of mice and negative control mice (p < 0.05). The protective dose 50 for the conventional and GRI vaccines obtained were 6.28 and 7.07, respectively, which indicated the high potency of both vaccines.

CONCLUSION

GRI vaccine is suitable for both routine vaccination and control of FMDV in emergency outbreaks.

Hemagglutinin-based polyanhydride nanovaccines against H5N1 influenza elicit protective virus neutralizing titers and cell-mediated immunity

H5N1 avian influenza is a significant global concern with the potential to become the next pandemic threat. Recombinant subunit vaccines are an attractive alternative for pandemic vaccines compared to traditional vaccine technologies. In particular, polyanhydride nanoparticles encapsulating subunit proteins have been shown to enhance humoral and cell-mediated immunity and provide protection upon lethal challenge. In this work, a recombinant H5 hemagglutinin trimer (H5₃) was produced and encapsulated into polyanhydride nanoparticles. The studies performed indicated that the recombinant H5₃ antigen was a robust immunogen. Immunizing mice with H5₃ encapsulated into polyanhydride nanoparticles induced high neutralizing antibody titers and enhanced CD4(+) T cell recall responses in mice. Finally, the H5₃-based polyanhydride nanovaccine induced protective immunity against a low-pathogenic H5N1 viral challenge. Informatics analyses indicated that mice receiving the nanovaccine formulations and subsequently challenged with virus were similar to naïve mice that were not challenged. The current studies provide a basis to further exploit the advantages of polyanhydride nanovaccines in pandemic scenarios.

Second generation inactivated eastern equine encephalitis virus vaccine candidates protect mice against a lethal aerosol challenge

Currently, there are no FDA-licensed vaccines or therapeutics for eastern equine encephalitis virus (EEEV) for human use. We recently developed several methods to inactivate CVEV1219, a chimeric live-attenuated eastern equine encephalitis virus (EEEV). Dosage and schedule studies were conducted to evaluate the immunogenicity and protective efficacy of three potential second-generation inactivated EEEV (iEEEV) vaccine candidates in mice: formalin-inactivated CVEV1219 (fCVEV1219), INA-inactivated CVEV1219 (iCVEV1219) and gamma-irradiated CVEV1219 (gCVEV1219). Both fCVEV1219 and gCVEV1219 provided partial to complete protection against an aerosol challenge when administered by different routes and schedules at various doses, while iCVEV1219 was unable to provide substantial protection against an aerosol challenge by any route, dose, or schedule tested. When evaluating antibody responses, neutralizing antibody, not virus specific IgG or IgA, was the best correlate of protection. The results of these studies suggest that both fCVEV1219 and gCVEV1219 should be evaluated further and considered for advancement as potential second-generation inactivated vaccine candidates for EEEV.

Gamma-Irradiated Influenza A Virus Provides Adjuvant Activity to a Co-Administered Poorly Immunogenic SFV Vaccine in Mice

Many currently available inactivated vaccines require “adjuvants” to maximize the protective immune responses generated against the antigens of interest. Recent studies in mice with gamma-irradiated influenza A virus (γ-FLU) have shown its superior efficacy compared to other forms of inactivated FLU vaccines and its ability to induce both potent interferon type-I (IFN-I) responses and the IFN-I-associated partial lymphocyte activation. Commonly, IFN-I responses induced by adjuvants, combined in vaccine preparations, have been shown to effectively enhance the immunogenicity of the antigens of interest. Therefore, we investigated the potential adjuvant activity of γ-FLU and the possible effect on antibody responses against co-administrated antigens, using gamma-irradiated Semliki Forest virus (γ-SFV) as the experimental vaccine in mice. Our data show that co-vaccination with γ-FLU and γ-SFV resulted in enhanced SFV-specific antibody responses in terms of increased titers by sixfold and greater neutralization efficacy, when compared to vaccination with γ-SFV alone. This study provides promising evidence related to the possible use of γ-FLU as an adjuvant to poorly immunogenic vaccines without compromising the vaccine efficacy of γ-FLU.

Asthma increases susceptibility to heterologous but not homologous secondary influenza

Asthma was the most common comorbidity observed among patients hospitalized with influenza A virus during the 2009 pandemic. However, little remains known about how the asthmatic phenotype influences protective immune responses against respiratory viral pathogens. Using the ovalbumin-induced allergic lung inflammation model, we found that asthmatic mice, unlike nonasthmatic mice, were highly susceptible to secondary heterologous virus challenge. While primary virus infection generated protective memory immune responses against homologous secondary virus challenge in both asthmatic and nonasthmatic mice, full protection against heterologous A/California/04/2009 (CA04) viral infection was observed only in nonasthmatic mice. Significant reductions in CA04-specific IgA, IgG, and IgM levels and in CA04-neutralizing activity of bronchoalveolar lavage fluid (BALF) was observed following secondary CA04 challenge of PR8-immunized asthmatic mice. Furthermore, transfer of immune BALF obtained from nonasthmatic, but not asthmatic, donors following secondary viral infection generated protection against CA04 in naive recipients. Nonspecific B-cell activation by CpG inoculation restored protection in PR8-immunized, CA04-challenged asthmatic mice. These results demonstrate a causal link between defective mucosal antibody responses and the heightened susceptibility of asthmatic mice to influenza infection and provide a mechanistic explanation for the observation that asthma was a major risk factor during the 2009 influenza pandemic.

IMPORTANCE

The prevalence of asthma worldwide is increasing each year. Unfortunately, there is no cure for asthma. Asthmatic individuals not only suffer from consistent wheezing and coughing but are also believed to be more prone to serious lung infections that result in bronchitis and pneumonia. However, little is known about the influence of asthma on host mucosal immunity. Here we show that antibody responses during secondary heterologous influenza infections are suboptimal and that this is responsible for the increased mortality in asthmatic mice from viral infections. Understanding the mechanism of increased susceptibility will aid in developing new antiviral therapies for asthmatic patients.

Full inactivation of human influenza virus by high hydrostatic pressure preserves virus structure and membrane fusion while conferring protection to mice against infection

Whole inactivated vaccines (WIVs) possess greater immunogenicity than split or subunit vaccines, and recent studies have demonstrated that WIVs with preserved fusogenic activity are more protective than non-fusogenic WIVs. In this work, we describe the inactivation of human influenza virus X-31 by high hydrostatic pressure (HHP) and analyze the effects on the structure by spectroscopic measurements, light scattering, and electron microscopy. We also investigated the effects of HHP on the glycoprotein activity and fusogenic activity of the viral particles. The electron microscopy data showed pore formation on the viral envelope, but the general morphology was preserved, and small variations were seen in the particle structure. The activity of hemagglutinin (HA) during the process of binding and fusion was affected in a time-dependent manner, but neuraminidase (NA) activity was not affected. Infectious activity ceased after 3 hours of pressurization, and mice were protected from infection after being vaccinated. Our results revealed full viral inactivation with overall preservation of viral structure and maintenance of fusogenic activity, thereby conferring protection against infection. A strong response consisting of serum immunoglobulin IgG1, IgG2a, and serum and mucosal IgA was also detected after vaccination. Thus, our data strongly suggest that applying hydrostatic pressure may be an effective method for developing new vaccines against influenza A as well as other viruses.

Heterosubtypic cross-protection induced by whole inactivated influenza virus vaccine in mice: influence of the route of vaccine administration

Background

Development of influenza vaccines capable of inducing broad protection against different virus subtypes is necessary given the ever‐changing viral genetic landscape. Previously, we showed that vaccination with whole inactivated virus (WIV) induces heterosubtypic protection against lethal virus infection in mice. Whole inactivated virus‐induced cross‐protection was found to be mediated primarily by flu‐specific CD8+ T cells.

Objectives

As it has been demonstrated that the route of vaccine administration strongly influences both the quantity and quality of vaccine‐induced immunity, in this study, we determined which route of WIV administration induces optimal heterosubtypic cross‐protection.

Methods

We compared the magnitude of the immune response and heterosubtypic protection against lethal A/PR/8/34 (H1N1) infection after subcutaneous (SC), intramuscular (IM), and intranasal (IN) vaccination with A/NIBRG‐14 (H5N1) WIV.

Results

Subcutaneous and IM administration was superior to IN administration of influenza WIV in terms of flu‐specific CD8+ T‐cell induction and protection of mice against lethal heterosubtypic challenge. Surprisingly, despite the very low flu‐specific CD8+ T‐cell responses detected in IN‐vaccinated mice, these animals were partially protected, most likely due to cross‐reactive IgA antibodies.

Conclusion

The results of this study show that the magnitude of WIV‐induced flu‐specific CD8+ T‐cell activity depends on the applied vaccination route. We conclude that parenteral administration of WIV vaccine, in particular IM injection, is superior to IN vaccine delivery for the induction of heterosubtypic cross‐protection and generally appears to elicit stronger immune responses than mucosal vaccination with WIV.

The role of nuclear technologies in the diagnosis and control of livestock diseases--a review

Nuclear and nuclear-related technologies have played an important role in animal health, particularly in relation to disease diagnosis and characterization of pathogenic organisms. This review focuses primarily on how and where nuclear technologies, both non-isotopic and isotopic methods, have made their impact in the past and where it might be expected they could have an impact in the future. The review outlines the extensive use of radiation attenuation in attempts to create vaccines for a multiplicity of pathogenic organisms and how the technology is being re-examined in the light of recent advances in irradiation techniques and cryopreservation/lyophilization that might obviate some of the problems of maintenance of viable, attenuate vaccines and their transport and use in the field. This approach could be used for a number of parasitic diseases where vaccination has been problematic and where investigations into the development of molecular vaccines have still failed to deliver satisfactory candidates for generating protective immune responses. Irradiation of antigens or serum samples also has its uses in diagnosis, especially when the samples need to be transported across international boundaries, or when handling the pathogens in question when carrying out a test presents serious health hazards to laboratory personnel. The present-day extensive use of enzyme immunoassays and molecular methods (e.g., polymerase chain reaction) for diagnosis and characterization of animal pathogens has its origins in the use of isotope-labeled antigens and antibodies. These isotopic techniques that included the use of 75Se, 32P, 125I, and 35S isotopes enabled a level of sensitivity and specificity that was hitherto unrealized, and it is prescient to remind ourselves of just how successful these technologies were, in spite of their infrequent use nowadays. Finally, the review looks at the potential for stable isotope analysis for a variety of applications--in the tracking of animal migrations, where the migrant are potential carriers of transboundary animal diseases, and where it would be useful to determine the origins of the carrier, e.g., Highly Pathogenic Avian Influenza and its dissemination by wild water fowl. Other applications could be in monitoring sequestered microbial culture (e.g., rinderpest virus) where in the case of accidental or deliberate release of infective culture it would be possible to identify the laboratory from which the isolate originated.

Microneedle and mucosal delivery of influenza vaccines

In recent years with the threat of pandemic influenza and other public health needs, alternative vaccination methods other than intramuscular immunization have received great attention. The skin and mucosal surfaces are attractive sites probably because of both noninvasive access to the vaccine delivery and unique immunological responses. Intradermal vaccines using a microinjection system (BD Soluvia(TM)) and intranasal vaccines (FluMist®) are licensed. As a new vaccination method, solid microneedles have been developed using a simple device that may be suitable for self-administration. Because coated microneedle influenza vaccines are administered in the solid state, developing formulations maintaining the stability of influenza vaccines is an important issue to be considered. Marketable microneedle devices and clinical trials remain to be developed. Other alternative mucosal routes such as oral and intranasal delivery systems are also attractive for inducing cross-protective mucosal immunity, but effective non-live mucosal vaccines remain to be developed.

Pseudotyped influenza A virus as a vaccine for the induction of heterotypic immunity

There is a need for vaccines that can protect broadly across all influenza A strains. We have produced a pseudotyped influenza virus based on suppression of the A/PR/8/34 hemagglutinin signal sequence (S-FLU) that can infect cells and express the viral core proteins and neuraminidase but cannot replicate. We show that when given by inhalation to mice, S-FLU is nonpathogenic but generates a vigorous T cell response in the lung associated with markedly reduced viral titers and weight loss after challenge with H1 and H3 influenza viruses. These properties of S-FLU suggest that it may have potential as a broadly protective A virus vaccine, particularly in the setting of a threatened pandemic before matched subunit vaccines become available.

Prospects for a novel ultrashort pulsed laser technology for pathogen inactivation

The threat of emerging pathogens and microbial drug resistance has spurred tremendous efforts to develop new and more effective antimicrobial strategies. Recently, a novel ultrashort pulsed (USP) laser technology has been developed that enables efficient and chemical-free inactivation of a wide spectrum of viral and bacterial pathogens. Such a technology circumvents the need to introduce potentially toxic chemicals and could permit safe and environmentally friendly pathogen reduction, with a multitude of possible applications including the sterilization of pharmaceuticals and blood products, and the generation of attenuated or inactivated vaccines.

Type I interferons in regulation of mucosal immunity

The mucosal system is the first line of defense against many pathogens. It is continuously exposed to dietary and microbial antigens, and thus the host must maintain a homeostatic environment between commensal microbiota and pathogenic infections. Following infections and inflammatory events, a rapid innate immune response is evoked to dampen the inflammatory processes. Type I interferons, a family of pleiotropic cytokines and major products of the innate immune response, have a key role in these early immune events at the mucosa, as reviewed here. With the emergence of new discoveries of immune cell types in mucosal tissues and their reactions to commensal and pathogenic organisms, we also review the opportunities for exciting research in this field.

Gamma-irradiated influenza virus uniquely induces IFN-I mediated lymphocyte activation independent of the TLR7/MyD88 pathway

Background

We have shown previously in mice, that infection with live viruses, including influenza/A and Semliki Forest virus (SFV), induces systemic partial activation of lymphocytes, characterized by cell surface expression of CD69 and CD86, but not CD25. This partial lymphocytes activation is mediated by type-I interferons (IFN-I). Importantly, we have shown that γ-irradiated SFV does not induce IFN-I and the associated lymphocyte activation.

Principal Findings

Here we report that, in contrast to SFV, γ-irradiated influenza A virus elicits partial lymphocyte activation in vivo. Furthermore, we show that when using influenza viruses inactivated by a variety of methods (UV, ionising radiation and formalin treatment), as well as commercially available influenza vaccines, only γ-irradiated influenza virus is able to trigger IFN-I-dependent partial lymphocyte activation in the absence of the TLR7/MyD88 signalling pathways.

Conclusions

Our data suggest an important mechanism for the recognition of γ-irradiated influenza vaccine by cytosolic receptors, which correspond with the ability of γ-irradiated influenza virus to induce cross-reactive and cross-protective cytotoxic T cell responses.

Cross-protective peptide vaccine against influenza A viruses developed in HLA-A*2402 human immunity model

Background

The virus-specific cytotoxic T lymphocyte (CTL) induction is an important target for the development of a broadly protective human influenza vaccine, since most CTL epitopes are found on internal viral proteins and relatively conserved. In this study, the possibility of developing a strain/subtype-independent human influenza vaccine was explored by taking a bioinformatics approach to establish an immunogenic HLA-A24 restricted CTL epitope screening system in HLA-transgenic mice.

Methodology/Principal Findings

HLA-A24 restricted CTL epitope peptides derived from internal proteins of the H5N1 highly pathogenic avian influenza A virus were predicted by CTL epitope peptide prediction programs. Of 35 predicted peptides, six peptides exhibited remarkable cytotoxic activity in vivo. More than half of the mice which were subcutaneously vaccinated with the three most immunogenic and highly conserved epitopes among three different influenza A virus subtypes (H1N1, H3N2 and H5N1) survived lethal influenza virus challenge during both effector and memory CTL phases. Furthermore, mice that were intranasally vaccinated with these peptides remained free of clinical signs after lethal virus challenge during the effector phase.

Conclusions/Significance

This CTL epitope peptide selection system can be used as an effective tool for the development of a cross-protective human influenza vaccine. Furthermore this vaccine strategy can be applicable to the development of all intracellular pathogens vaccines to induce epitope-specific CTL that effectively eliminate infected cells.

Return of inactivated whole-virus vaccine for superior efficacy

The swine, influenza, H1N1 outbreak in 2009 highlighted the inadequacy of the currently used antibody-based vaccine strategies as a preventive measure for combating influenza pandemics. The ultimate goal for successful control of newly arising influenza outbreaks is to design a single-shot vaccine that will provide long-lasting immunity against all strains of influenza A virus. A large amount of data from animal studies has indicated that the cross-reactive cytotoxic T (Tc) cell response against conserved influenza virus epitopes may be the key immune response needed for a universal influenza vaccine. However, decades of research have shown that the development of safe T-cell-based vaccines for influenza is not an easy task. Here, I discuss the overlooked but potentially highly advantageous inactivation method, namely, γ-ray irradiation, as a mean to reach the Holy Grail of influenza vaccinology.

Intranasal immunization with recombinant HA and mast cell activator C48/80 elicits protective immunity against 2009 pandemic H1N1 influenza in mice

Background

Pandemic influenza represents a major threat to global health. Vaccination is the most economic and effective strategy to control influenza pandemic. Conventional vaccine approach, despite being effective, has a number of major deficiencies including limited range of protection, total dependence on embryonated eggs for production, and time consuming for vaccine production. There is an urgent need to develop novel vaccine strategies to overcome these deficiencies.

Methodology/Principal Findings

The major objective of this work was to develop a novel vaccine strategy combining recombinant haemagglutinin (HA) protein and a master cell (MC) activator C48/80 for intranasal immunization. We demonstrated in BALB/c mice that MC activator C48/80 had strong adjuvant activity when co-administered with recombinant HA protein intranasally. Vaccination with C48/80 significantly increased the serum IgG and mucosal surface IgA antibody responses against HA protein. Such increases correlated with stronger and durable neutralizing antibody activities, offering protection to vaccinated animals from disease progression after challenge with lethal dose of A/California/04/2009 live virus. Furthermore, protected animals demonstrated significant reduction in lung virus titers, minimal structural alteration in lung tissues as well as higher and balanced production of Th1 and Th2 cytokines in the stimulated splenocytes when compared to those without C48/80.

Conclusions/Significance

The present study demonstrates that the novel vaccine approach of combining recombinant HA and mucosal adjuvant C48/80 is safe and effective in eliciting protective immunity in mice. Future studies on the mechanism of action of C48/80 and potential combination with other vaccine strategies such as prime and boost approach may help to induce even more potent and broad immune responses against viruses from various clades.

Heterosubtypic antibody response elicited with seasonal influenza vaccine correlates partial protection against highly pathogenic H5N1 virus

Background

The spread of highly pathogenic avian influenza (HPAI) H5N1 virus in human remains a global health concern. Heterosubtypic antibody response between seasonal influenza vaccine and potential pandemic influenza virus has important implications for public health. Previous studies by Corti et al. and by Gioia et al. demonstrate that heterosubtypic neutralizing antibodies against the highly pathogenic H5N1 virus can be elicited with a seasonal influenza vaccine in humans. However, whether such response offers immune protection against highly pathogenic H5N1 virus remained to be determined.

Methodology/Principal Findings

In this study, using a sensitive influenza HA (hemagglutinin) and NA (neuraminidase) pseudotype-based neutralization (PN) assay we first confirmed that low levels of heterosubtypic neutralizing antibody response against H5N1 virus were indeed elicited with seasonal influenza vaccine in humans. We then immunized mice with the seasonal influenza vaccine and challenged them with lethal doses of highly pathogenic H5N1 virus. As controls, we immunized mice with homosubtypic H5N1 virus like particles (VLP) or PBS and challenged them with the same H5N1 virus. Here we show that low levels of heterosubtypic neutralizing antibody response were elicited with seasonal influenza vaccine in mice, which were significantly higher than those in PBS control. Among them 2 out of 27 whose immune sera exhibited similar levels of neutralizing antibody response as VLP controls actually survived from highly pathogenic H5N1 virus challenge.

Conclusions/Significance

Therefore, we conclude that low levels of heterosubtypic neutralizing antibody response are indeed elicited with seasonal influenza vaccine in humans and mice and at certain levels such response offers immune protection against severity of H5N1 virus infection.

Cross-protective immunity to influenza A viruses

Antigenic changes in influenza virus occur gradually, owing to mutations (antigenic drift), and abruptly, owing to reassortment among subtypes (antigenic shift). Availability of strain-matched vaccines often lags behind these changes, resulting in a shortfall in public health. In animal models, cross-protection by vaccines based on conserved antigens does not completely prevent infection, but greatly reduces morbidity, mortality, virus replication and, thus, viral shedding and spread. Such immunity is especially effective and long-lasting with mucosal administration. Cross-protective immunity in humans is controversial, but is suggested by some epidemiological findings. 'Universal' vaccines protective against all influenza A viruses might substantially reduce severity of infection and limit spread of disease during outbreaks. These vaccines could be used 'off the shelf' early in an outbreak or pandemic, before strain-matched vaccines are available.

Preclinical efficacy studies of influenza A haemagglutinin precursor cleavage loop peptides as a potential vaccine

A universal influenza vaccine that does not require annual reformulation would have clear advantages over the currently approved seasonal vaccine. In this study, we combined the mucosal adjuvant alpha-galactosylceramide (αGalCer) and peptides designed across the highly conserved influenza precursor haemagglutinin (HA(0)) cleavage loop as a vaccine. Peptides designed across the HA(0) of influenza A/H3N2 viruses, delivered to mice via the intranasal route with αGalCer as an adjuvant, provided 100 % protection following H3N2 virus challenge. Similarly, intranasal inoculation of peptides across the HA(0) of influenza A/H5N1 with αGalCer completely protected mice against heterotypic challenge with H3N2 virus. Our data suggest that these peptide vaccines effectively inhibited subsequent influenza A/H3N2 virus replication. In contrast, only 20 % of mice vaccinated with αGalCer-adjuvanted peptides spanning the HA(0) of H5N1 survived homologous viral challenge, possibly because the HA(0) of this virus subtype is cleaved by intracellular furin-like enzymes. Results of these studies demonstrated that HA(0) peptides adjuvanted with αGalCer have the potential to form the basis of a synthetic, intranasal influenza vaccine.

Human immunodeficiency virus-1 vaccine design: where do we go now?

Numerous human immunodeficiency virus (HIV)-1 vaccines have been developed over the last three decades, but to date an effective HIV-1 vaccine that can be used for prophylactic or therapeutic purposes in humans has not been identified. The failures and limited successes of HIV-1 vaccines have highlighted the gaps in our knowledge with regard to fundamental immunity against HIV-1 and have provided insights for vaccine strategies that may be implemented for designing more effective HIV-1 vaccines in the future. Recent studies have shown that robust mucosal immunity, high avidity and polyfunctional T cells, and broadly neutralizing antibodies are important factors governing the induction of protective immunity against HIV-1. Furthermore, optimization of vaccine delivery methods for DNA or live viral vector-based vaccines, elucidating the immune responses of individuals who remain resistant to HIV-1 infections and also understanding the core immune responses mediating protection against simian immunodeficiency viruses (SIV) and HIV-1 in animal models following vaccination, are key aspects to be regarded for designing more effective HIV-1 vaccines in the future.

Cytotoxic T cells are the predominant players providing cross-protective immunity induced by {gamma}-irradiated influenza A viruses

We previously demonstrated that a single dose of nonadjuvanted intranasal gamma-irradiated influenza A virus can provide robust protection in mice against both homologous and heterosubtypic challenges, including challenge with an H5N1 avian virus strain. We investigated the mechanism behind the observed cross-protection to define which arms of the adaptive immune response are involved in mediating this protection. Studies with gene knockout mice showed the cross-protective immunity to be mediated mainly by T cells and to be dependent on the cytolytic effector molecule perforin. Adoptive transfer of memory T cells from immunized mice, but not of memory B cells, protected naïve recipients against lethal heterosubtypic influenza virus challenge. Furthermore, gamma-irradiated influenza viruses induced cross-reactive Tc-cell responses but not cross-neutralizing or cross-protective antibodies. In addition, histological analysis showed reduced lung inflammation in vaccinated mice compared to that in unvaccinated controls following heterosubtypic challenge. This reduced inflammation was associated with enhanced early recruitment of T cells, both CD4(+) and CD8(+), and with early influenza virus-specific cytotoxic T-cell responses. Therefore, cross-protective immunity induced by vaccination with gamma-irradiated influenza A virus is mediated mainly by Tc-cell responses.

Effect of inactivation method on the cross-protective immunity induced by whole 'killed' influenza A viruses and commercial vaccine preparations

We have recently shown that intranasal (i.n.) administration of gamma-irradiated A/PR/8 [A/Puerto Rico/8/34 (H1N1)] protects mice against lethal avian influenza A/Vietnam/1203/2004 (H5N1) and other heterosubtypic influenza A infections. Here, we used gamma-irradiated, formalin- and UV-inactivated A/PC [A/Port Chalmers/1/73 (H3N2)] virus preparations and compared their ability to induce both homologous and heterosubtypic protective immunity. Our data show that, in contrast to i.n. vaccination with formalin- or UV-inactivated virus, or the present commercially available trivalent influenza vaccine, a single dose of gamma-ray-inactivated A/PC (gamma-A/PC) conferred significant protection in mice against both homologous and heterosubtypic virus challenges. A multiple immunization regime was required for formalin-inactivated virus preparations to induce protective immunity against a homotypic virus challenge, but did not induce influenza A strain cross-protective immunity. The highly immunogenic gamma-A/PC, but not formalin- or UV-inactivated A/PC, nor the currently available subvirion vaccine, elicited cytotoxic T-cell responses that are most likely responsible for the cross-protective and long-lasting immunity against highly lethal influenza A infections in mice. Finally, freeze-drying of gamma-A/PC did not affect the ability to induce cross-protective immunity.

Induction of HIV-1-specific cellular and humoral immune responses following immunization with HIV-DNA adjuvanted with activated apoptotic lymphocytes

Delivery of DNA encoding foreign antigens into mammalian cells can induce adaptive immune responses. There are currently many DNA-based vaccines in clinical trials against infectious diseases and cancer but there is a lack of adjuvants for improvement of responses to DNA-based vaccines. Here, we show augmented systemic and mucosa-associated B cell responses after immunization with a cocktail of seven different plasmids (3 env, 2 gag, 1 rev, 1 RT) combined with mitogen activated apoptotic syngeneic lymphocytes in mice. In addition we show that apoptotic cells can function as adjuvant for induction of cellular immune responses in a magnitude comparable to the cytokine adjuvant GM-CSF in mice. These data suggest that activated apoptotic lymphocytes can act independent as adjuvants to improve antigen-specific DNA vaccines.

An update on swine-origin influenza virus A/H1N1: a review

Influenza viruses cause annual epidemics and occasional pandemics that have claimed the lives of millions. The emergence of new strains will continue to pose challenges to public health and the scientific communities. The recent flu pandemic caused by a swine-origin influenza virus A/H1N1 (S-OIV) presents an opportunity to examine virulence factors, the spread of the infection and to prepare for major influenza outbreaks in the future. The virus contains a novel constellation of gene segments, the nearest known precursors being viruses found in swine and it probably arose through reassortment of two viruses of swine origin. Specific markers for virulence can be evaluated in the viral genome, PB1-F2 is a molecular marker of pathogenicity but is not present in the new S-OIV. While attention was focused on a threat of an avian influenza H5N1 pandemic emerging from Asia, a novel influenza virus of swine origin emerged in North America, and is now spreading worldwide. However, S-OIV demonstrates that even serotypes already encountered in past human pandemics may constitute new pandemic threats. There are concerns that this virus may mutate or reassort with existing influenza viruses giving rise to more transmissible or more pathogenic viruses. The 1918 Spanish flu pandemic virus was relatively mild in its first wave and acquired more virulence when it returned in the winter. Thus preparedness on a global scale against a potential more virulent strain is highly recommended. Most isolates of the new S-OIVs are susceptible to neuraminidase inhibitors, and currently a vaccine against the pandemic strain is being manufactured and will be available this fall. This review summarizes the current information on the new pandemic swine-origin influenza virus A/H1N1.