JE-ADVAX vaccine protection against Japanese encephalitis virus mediated by memory B cells in the absence of CD8(+) T cells and pre-exposure neutralizing antibody

Antibodies from dengue patients with prior exposure to Japanese encephalitis virus are broadly neutralizing against Zika virus

Exposure to multiple mosquito-borne flaviviruses within a lifetime is not uncommon; however, how sequential exposures to different flaviviruses shape the cross-reactive humoral response against an antigen from a different serocomplex has yet to be explored. Here, we report that dengue-infected individuals initially primed with the Japanese encephalitis virus (JEV) showed broad, highly neutralizing potencies against Zika virus (ZIKV). We also identified a rare class of ZIKV-cross-reactive human monoclonal antibodies with increased somatic hypermutation and broad neutralization against multiple flaviviruses. One huMAb, K8b, binds quaternary epitopes with heavy and light chains separately interacting with overlapping envelope protein dimer units spanning domains I, II, and III through cryo-electron microscopy and structure-based mutagenesis. JEV virus-like particle immunization in mice further confirmed that such cross-reactive antibodies, mainly IgG3 isotype, can be induced and proliferate through heterologous dengue virus (DENV) serotype 2 virus-like particle stimulation. Our findings highlight the role of prior immunity in JEV and DENV in shaping the breadth of humoral response and provide insights for future vaccination strategies in flavivirus-endemic countries.

The Japanese Encephalitis Antigenic Complex Viruses: From Structure to Immunity

In the last three decades, several flaviviruses of concern that belong to different antigenic groups have expanded geographically. This has resulted in the presence of often more than one virus from a single antigenic group in some areas, while in Europe, Africa and Australia, additionally, multiple viruses belonging to the Japanese encephalitis (JE) serogroup co-circulate. Morphological heterogeneity of flaviviruses dictates antibody recognition and affects virus neutralization, which influences infection control. The latter is further impacted by sequential infections involving diverse flaviviruses co-circulating within a region and their cross-reactivity. The ensuing complex molecular virus-host interplay leads to either cross-protection or disease enhancement; however, the molecular determinants and mechanisms driving these outcomes are unclear. In this review, we provide an overview of the epidemiology of four JE serocomplex viruses, parameters affecting flaviviral heterogeneity and antibody recognition, host immune responses and the current knowledge of the cross-reactivity involving JE serocomplex flaviviruses that leads to differential clinical outcomes, which may inform future preventative and therapeutic interventions.

Evaluation of the safety and efficacy of AdvaxTM as an adjuvant: A systematic review and meta-analysis

PURPOSE

Developing a vaccine with improved immunogenicity is still a growing priority for many diseases. Different types of adjuvants may be beneficial to initiate and maintain the long-lasting immunogenicity of vaccines. Evidence has shown that polysaccharide adjuvants are efficient in improving immunological mechanisms with their biocompatibility and biodegradability characteristics. In this study, we aimed to investigate the safety and efficacy of Advax^TM an adjuvant derived from delta inulin.

METHODS

A systematic research was performed in Pubmed, Web of Science, and Scopus databases for the following keywords; "Advax^TM" OR "delta inulin" until December 14th, 2020. RevMan 5.4.1 software was used for cumulative meta-analysis and bias analysis. We also used GraphPad Prism 6 software for the figures.

RESULTS

In the cumulative meta-analysis, it was found that seroconversion and geometric mean titers (GMT) levels significantly increased in Advax^TM-adjuvanted group (mean difference: 12.31, 95% Cl [4.14, 20.47], p ​= ​0.003; 17.10, 95% Cl [4.35, 29.85], p ​= ​0.009, respectively). We also observed that Advax^TM could be effective in improving immunogenicity by inducing T-cell responses and plasmablast generation in viral vaccines.

CONCLUSIONS

In this study, it was shown that Advax^TM is a safe and well-tolerated adjuvant. Advax^TM could be a potent adjuvant in increasing the protection and immunogenicity of different vaccines without safety issues. However, further studies are needed to verify these effects of Advax^TM adjuvant.

Intranasal powder live attenuated influenza vaccine is thermostable, immunogenic, and protective against homologous challenge in ferrets

Influenza viruses cause annual seasonal epidemics and sporadic pandemics; vaccination is the most effective countermeasure. Intranasal live attenuated influenza vaccines (LAIVs) are needle-free, mimic the natural route of infection, and elicit robust immunity. However, some LAIVs require reconstitution and cold-chain requirements restrict storage and distribution of all influenza vaccines. We generated a dry-powder, thermostable LAIV (T-LAIV) using Preservation by Vaporization technology and assessed the stability, immunogenicity, and efficacy of T-LAIV alone or combined with delta inulin adjuvant (Advax™) in ferrets. Stability assays demonstrated minimal loss of T-LAIV titer when stored at 25 °C for 1 year. Vaccination of ferrets with T-LAIV alone or with delta inulin adjuvant elicited mucosal antibody and robust serum HI responses in ferrets, and was protective against homologous challenge. These results suggest that the Preservation by Vaporization-generated dry-powder vaccines could be distributed without refrigeration and administered without reconstitution or injection. Given these significant advantages for vaccine distribution and delivery, further research is warranted.

Prefusion RSV F Immunization Elicits Th2-Mediated Lung Pathology in Mice When Formulated With a Th2 (but Not a Th1/Th2-Balanced) Adjuvant Despite Complete Viral Protection

Respiratory syncytial virus (RSV) remains the most common cause of lower respiratory tract infections in children worldwide. Development of a vaccine has been hindered by the risk of developing enhanced respiratory disease (ERD) upon natural exposure to the virus. Generation of higher quality neutralizing antibodies with stabilized pre-fusion F protein antigens has been proposed as a strategy to prevent ERD. We sought to test whether there was evidence of ERD in naïve BALB/c mice immunized with an unadjuvanted, stabilized pre-fusion F protein, and challenged with RSV line 19. We further sought to determine the extent to which formulation with a Th2-biased (alum) or a more Th1/Th2-balanced (Advax-SM) adjuvant influenced cellular responses and lung pathology. When exposed to RSV, mice immunized with pre-fusion F protein alone (PreF) exhibited increased airway eosinophilia and mucus accumulation. This was further exacerbated by formulation of PreF with Alum (aluminum hydroxide). Conversely, formulation of PreF with a Th1/Th2-balanced adjuvant, Advax-SM, not only suppressed RSV viral replication, but also inhibited airway eosinophilia and mucus accumulation. This was associated with lower numbers of lung innate lymphocyte cells (ILC2s) and CD4+ T cells producing IL-5+ or IL-13+ and increased IFNγ+ CD4+ and CD8+ T cells, in addition to RSV F-specific CD8+ T cells. These data suggest that in the absence of preimmunity, stabilized PreF antigens may still be associated with aberrant Th2 responses that induce lung pathology in response to RSV infection, and can be prevented by formulation with more Th1/Th2-balanced adjuvants that enhance CD4+ and CD8+ IFNγ+ T cell responses. This may support the use of stabilized PreF antigens with Th1/Th2-balanced adjuvants like, Advax-SM, as safer alternatives to alum in RSV vaccine candidates.

Adjuvant selection impacts the correlates of vaccine protection against Ebola infection

The establishment of correlates of protection is particularly relevant in the context of rare, highly lethal pathogens such as filoviruses. We previously demonstrated that an Ebola glycoprotein virus-like particle (VLP) vaccine, when given as two intramuscular doses, conferred protection from challenge in a murine challenge model. In this study, we compared the ability of Advax inulin-based adjuvant formulations (Advax1-4) to enhance Ebola VLP vaccine protection in mice. After two immunizations, Advax-adjuvants that included a TLR9 agonist component induced high IgG responses, with complete protection against Ebola virus challenge. Although anti-Ebola IgG levels waned over time, protection was durable and was still evident 150 days post-immunization. Mice were protected after just a single VLP immunization with Advax-2 or -4 adjuvants. Advax-adjuvanted VLPs induced a stronger IFN-γ, TNF and IL-12 signature and serum transferred from Advax-adjuvanted vaccinees was able to transfer protection to naïve animals, showing that Ebola protection can be achieved by antibodies in the absence of cellular immunity. By contrast, serum from vaccinees incorporating a pICLC adjuvant did not transfer protection despite high IgG levels on ELISA. These data highlight the importance of adjuvant selection for development of a successful Ebola VLP vaccine.

Japanese encephalitis - the prospects for new treatments

Japanese encephalitis is a mosquito-borne disease that occurs in Asia and is caused by Japanese encephalitis virus (JEV), a member of the genus Flavivirus. Although many flaviviruses can cause encephalitis, JEV causes particularly severe neurological manifestations. The virus causes loss of more disability-adjusted life years than any other arthropod-borne virus owing to the frequent neurological sequelae of the condition. Despite substantial advances in our understanding of Japanese encephalitis from in vitro studies and animal models, studies of pathogenesis and treatment in humans are lagging behind. Few mechanistic studies have been conducted in humans, and only four clinical trials of therapies for Japanese encephalitis have taken place in the past 10 years despite an estimated incidence of 69,000 cases per year. Previous trials for Japanese encephalitis might have been too small to detect important benefits of potential treatments. Many potential treatment targets exist for Japanese encephalitis, and pathogenesis and virological studies have uncovered mechanisms by which these drugs could work. In this Review, we summarize the epidemiology, clinical features, prevention and treatment of Japanese encephalitis and focus on potential new therapeutic strategies, based on repurposing existing compounds that are already suitable for human use and could be trialled without delay. We use our newly improved understanding of Japanese encephalitis pathogenesis to posit potential treatments and outline some of the many challenges that remain in tackling the disease in humans.

The Safety of an Adjuvanted Autologous Cancer Vaccine Platform in Canine Cancer Patients

Canine cancer rates are similar to humans, though the therapeutic options might be limited. Inducing a patient’s own immune system to have an anti-tumor response is an attractive approach to cancer therapy. In this safety study, autologous tumor vaccines produced specifically for each canine patient were combined with Advax™, a novel non-inflammatory immunomodulator and vaccine adjuvant and were tested for safety in a diverse range of patient presentations alone or in combination with other treatments. Canine patients had their tumor biopsied, debulked or resected and the tumor antigens were processed into an autologous vaccine formulated with Advax™ adjuvant with or without rhizavidin as an additional immune stimulant. Patients treated early in the trial received two intramuscular (IM) doses, 2 weeks apart. As the study progressed and no issues of safety were observed, the protocol was changed to weekly vaccinations for 4 weeks followed by monthly booster shots. Over the 150 I.M injections delivered to date, the vaccine was found to be very safe and no significant adverse reactions were observed. These results justify ongoing development and future controlled studies of this autologous vaccine approach.

Zika virus vaccines

The recent epidemic of Zika virus (ZIKV) in the Americas has revealed the devastating consequences of ZIKV infection, particularly in pregnant women. Congenital Zika syndrome, characterized by malformations and microcephaly in neonates as well as developmental challenges in children, highlights the need for the development of a safe and effective vaccine. Multiple vaccine candidates have been developed and have shown promising results in both animal models and phase I clinical trials. However, important challenges remain for the clinical development of these vaccines. In this Progress article, we discuss recent preclinical studies and lessons learned from first-in-human clinical trials with ZIKV vaccines.

Developing effective vaccines: Cues from natural infection

The ultimate goal of any vaccine is to generate a heterogeneous and stable pool of memory lymphocytes. Vaccine are designed with the hope to generate antigen specific long-lived T cell responses, as it may be the case in natural infection; however, inducing such response by sub-unit vaccine has been a challenge. Although significant progress has been made, there is lot of scope for designing novel vaccine strategies by taking cues from the natural infection. This review focuses upon the roadblocks and the possible ways to overcome them leading to developing effective vaccines. Here we propose that mimicking the natural course of infection as well as the inclusion of non-target antigens in vaccine formulations might generate heterogeneous pool of memory T cells to ensure long-lived protection.

Delta inulin-based adjuvants promote the generation of polyfunctional CD4+ T cell responses and protection against Mycobacterium tuberculosis infection

There is an urgent need for the rational design of safe and effective vaccines to protect against chronic bacterial pathogens such as Mycobacterium tuberculosis. Advax™ is a novel adjuvant based on delta inulin microparticles that enhances immunity with a minimal inflammatory profile and has entered human trials to protect against viral pathogens. In this report we determined if Advax displays broad applicability against important human pathogens by assessing protective immunity against infection with M. tuberculosis. The fusion protein CysVac2, comprising the M. tuberculosis antigens Ag85B (Rv1886c) and CysD (Rv1285) formulated with Advax provided significant protection in the lungs of M. tuberculosis-infected mice. Protection was associated with the generation of CysVac2-specific multifunctional CD4+ T cells (IFN-γ+TNF+IL-2+). Addition to Advax of the TLR9 agonist, CpG oligonucleotide (AdvaxCpG), improved both the immunogenicity and protective efficacy of CysVac2. Immunisation with CysVac2/AdvaxCpG resulted in heightened release of the chemoattractants, CXCL1, CCL3, and TNF, and rapid influx of monocytes and neutrophils to the site of vaccination, with pronounced early priming of CysVac2-specific CD4+ T cells. As delta inulin adjuvants have shown an excellent safety and tolerability profile in humans, CysVac2/AdvaxCpG is a strong candidate for further preclinical evaluation for progression to human trials.

DNA prime/protein boost vaccination elicits robust humoral response in rhesus macaques using oligomeric simian immunodeficiency virus envelope and Advax delta inulin adjuvant

The partial success of the RV144 trial underscores the importance of envelope-specific antibody responses for an effective HIV-1 vaccine. Oligomeric HIV-1 envelope proteins delivered with a potent adjuvant are expected to elicit strong antibody responses with broad neutralization specificity. To test this hypothesis, two SIV envelope proteins were formulated with delta inulin-based adjuvant (Advax) and used to immunize nonhuman primates. Oligomeric gp140-gp145 from SIVmac251 and SIVsmE660 was purified to homogeneity. Oligomers showed high-affinity interaction with CD4 and were highly immunogenic in rabbits, inducing Tier 2 SIV-neutralizing antibodies. The immunogenicity of an oligomeric Env DNA prime and protein boost together with Advax was evaluated in Chinese rhesus macaques. DNA administration elicited antibodies to both envelopes, and titres were markedly enhanced following homologous protein boosts via intranasal and intramuscular routes. Strong antibody responses were detected against the V1 and V2 domains of gp120. During peak immune responses, a low to moderate level of neutralizing activity was detected against Tier 1A/1B SIV isolates, with a moderate level noted against a Tier 2 isolate. Increased serum antibody affinity to SIVmac251 gp140 and generation of Env-specific memory B cells were observed in the immunized macaques. Animals were subjected to low-dose intravaginal challenge with SIVmac251 one week after the last protein boost. One out of three immunized animals was protected from infection. Although performed with a small number of macaques, this study demonstrates the utility of oligomeric envelopes formulated with Advax in eliciting broad antibody responses with the potential to provide protection against SIV transmission.

A New Clade of Insect-Specific Flaviviruses from Australian Anopheles Mosquitoes Displays Species-Specific Host Restriction

Flaviviruses like dengue, Zika, or West Nile virus infect millions of people each year and are transmitted to humans via infected-mosquito bites. A subset of flaviviruses can only replicate in the mosquito host, and recent studies have shown that some can interfere with pathogenic flaviviruses in mosquitoes and limit the replication and transmission of the latter. The insect-specific flaviviruses (ISFs) reported here form a new Anopheles mosquito-associated clade separate from the Aedes- and Culex-associated ISF clades. The identification of distinct clades for each mosquito genus provides new insights into the evolution and ecology of flaviviruses. One of these viruses was shown to replicate in the midgut of the mosquito host and exhibit the most specialized host restriction reported to date for ISFs. Understanding this unprecedented host restriction in ISFs could help identify the mechanisms involved in the evolution of flaviviruses and their emergence as mosquito-borne pathogens.

Flaviviruses are arthropod-borne viruses found worldwide and are responsible for significant human and veterinary diseases, including dengue, Zika, and West Nile fever. Some flaviviruses are insect specific and replicate only in mosquitoes. We report a genetically divergent group of insect-specific flaviviruses from Anopheles mosquitoes that do not replicate in arthropod cell lines or heterologous Anopheles species, exhibiting unprecedented specialization for their host species. Determination of the complete sequences of the RNA genomes of three of these viruses, Karumba virus (KRBV), Haslams Creek virus, and Mac Peak virus (McPV), that are found in high prevalence in some Anopheles mosquito populations and detection of virus-specific proteins, replicative double-stranded RNA, and small interfering RNA responses in the host mosquito species provided strong evidence of a functional replicating virus in the mosquito midgut. Analysis of nucleotide composition in the KRBV and McPV sequences also revealed a pattern consistent with the virus evolving to replicate only in insects. These findings represent a significant advance in our knowledge of mosquito-borne flavivirus ecology, host restriction, and evolution.

IMPORTANCE Flaviviruses like dengue, Zika, or West Nile virus infect millions of people each year and are transmitted to humans via infected-mosquito bites. A subset of flaviviruses can only replicate in the mosquito host, and recent studies have shown that some can interfere with pathogenic flaviviruses in mosquitoes and limit the replication and transmission of the latter. The insect-specific flaviviruses (ISFs) reported here form a new Anopheles mosquito-associated clade separate from the Aedes- and Culex-associated ISF clades. The identification of distinct clades for each mosquito genus provides new insights into the evolution and ecology of flaviviruses. One of these viruses was shown to replicate in the midgut of the mosquito host and exhibit the most specialized host restriction reported to date for ISFs. Understanding this unprecedented host restriction in ISFs could help identify the mechanisms involved in the evolution of flaviviruses and their emergence as mosquito-borne pathogens.

Investigation of the biodistribution, breakdown and excretion of delta inulin adjuvant

Insoluble, nanostructured delta inulin particles enhance the immunogenicity of co-administered protein antigens and consequently are used as a vaccine adjuvant (Advax™). To better understand their immunomodulatory properties, the in vitro hydrolysis and in vivo distribution of delta inulin particles were investigated. Delta inulin particle hydrolysis under bio-relevant acidic conditions resulted in no observable change to the bulk morphology using SEM, and HPLC results showed that only 6.1% of the inulin was hydrolysed over 21days. However, 65% of the terminal glucose groups were released, showing that acid hydrolysis relatively rapidly releases surface bound chemistries. This was used to explain in vivo biodistribution results in which delta inulin particles surface-labelled with fluorescein-5-thiosemicabizide were administered to mice using intramuscular (I.M.) or subcutaneous (S.C.) routes. Comparison analysis of the fluorescence of soluble inulin in the supernatants of homogenised tissues maintained at room temperature or heated to 100°C to solubilise particulate inulin was used to distinguish between fluorescent probe on soluble inulin and probe bound to inulin within particles. Following both I.M. and S.C. injection delta inulin exhibited a depot behaviour with local injection site residence for several weeks. Over this time, as injection site inulin reduced, there was measurable transport of intact delta inulin particles by macrophages to secondary lymphoid organs and the liver. Ultimately, the injected delta inulin became solubilised resulting in its detection in the plasma and in the urine. Thus injected delta inulin particles are initially taken up by macrophages at the site of injection, trafficked to secondary lymphoid tissue and the liver, and hydrolysed resulting in their becoming soluble and diffusing into the blood stream, from whence they are glomerularly filtered and excreted into the urine. These results provide important insights into the biodistribution of I.M. or S.C. injected delta inulin particles when used as vaccine adjuvants and their method of excretion.

A Japanese Encephalitis Virus Vaccine Inducing Antibodies Strongly Enhancing In Vitro Infection Is Protective in Pigs

The Japanese encephalitis virus (JEV) is responsible for zoonotic severe viral encephalitis transmitted by Culex mosquitoes. Although birds are reservoirs, pigs play a role as amplifying hosts, and are affected in particular through reproductive failure. Here, we show that a lentiviral JEV vector, expressing JEV prM and E proteins (TRIP/JEV.prME), but not JEV infection induces strong antibody-dependent enhancement (ADE) activities for infection of macrophages. Such antibodies strongly promoted infection via Fc receptors. ADE was found at both neutralizing and non-neutralizing serum dilutions. Nevertheless, in vivo JEV challenge of pigs demonstrated comparable protection induced by the TRIP/JEV.prME vaccine or heterologous JEV infection. Thus, either ADE antibodies cause no harm in the presence of neutralizing antibodies or may even have protective effects in vivo in pigs. Additionally, we found that both pre-infected and vaccinated pigs were not fully protected as low levels of viral RNA were found in lymphoid and nervous system tissue in some animals. Strikingly, the virus from the pre-infection persisted in the tonsils throughout the experiment. Finally, despite the vaccination challenge, viral RNA was detected in the oronasal swabs in all vaccinated pigs. These latter data are relevant when JEV vaccination is employed in pigs.

Vaccine Adjuvant Nanotechnologies

The increasing sophistication of vaccine adjuvant design has been driven by improved understanding of the importance of nanoscale features of adjuvants to their immunological function. Newly available advanced nanomanufacturing techniques now allow very precise control of adjuvant particle size, shape, texture, and surface chemistry. Novel adjuvant concepts include self-assembling particles and targeted immune delivery. These individual concepts can be combined to create a single integrated vaccine nanoparticle-combining antigen, adjuvants, and DC-targeting elements. In the process, the concept of an adjuvant has broadened to include not only immune-stimulatory substances but also any design features that enhance the immune response against the relevant vaccine antigen. The modern definition of an adjuvant includes not only classical immune stimulators but also any aspects of particle size, shape, and surface chemistry that enhance vaccine immunogenicity. It even includes purely physical processes such as texturing of particle surfaces to maximize immunogenicity. Looking forward, adjuvants will increasingly be seen not as separate add-on items but as wholly integrated elements of a complete vaccine delivery package. Hence, vaccine systems will increasingly approach the complexity and sophistication of pathogens themselves, incorporating highly specific particle properties, contents, and behaviors, all designed to maximize immune system recognition and drive the immune response in the specific direction that affords maximal protection.

Advax, a Delta Inulin Microparticle, Potentiates In-built Adjuvant Property of Co-administered Vaccines

Advax, a delta inulin-derived microparticle, has been developed as an adjuvant for several vaccines. However, its immunological characteristics and potential mechanism of action are yet to be elucidated. Here, we show that Advax behaves as a type-2 adjuvant when combined with influenza split vaccine, a T helper (Th)2-type antigen, but behaves as a type-1 adjuvant when combined with influenza inactivated whole virion (WV), a Th1-type antigen. In addition, an adjuvant effect was not observed when Advax-adjuvanted WV vaccine was used to immunize toll-like receptor (TLR) 7 knockout mice which are unable to respond to RNA contained in WV antigen. Similarly, no adjuvant effect was seen when Advax was combined with endotoxin-free ovalbumin, a neutral Th0-type antigen. An adjuvant effect was also not seen in tumor necrosis factor (TNF)-α knockout mice, and the adjuvant effect required the presences of dendritic cells (DCs) and phagocytic macrophages. Therefore, unlike other adjuvants, Advax potentiates the intrinsic or in-built adjuvant property of co-administered antigens. Hence, Advax is a unique class of adjuvant which can potentiate the intrinsic adjuvant feature of the vaccine antigens through a yet to be determined mechanism.

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Advax potentiates built-in adjuvant property of vaccine antigens.

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Advax does not change the T helper immune bias induced by the vaccine antigen.

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Dendritic cells, phagocytic macrophages, and tumor necrosis factor-α play a role in Advax adjuvant activity.

Adjuvants are indispensable agent to maximize the efficacy of vaccines. Most adjuvants consistently impart either T helper (Th)1, Th2 or Th17 bias to the vaccine response regardless of the properties of antigen. For example alum adjuvants consistently impart a Th2 bias regardless of the vaccine antigen. Here we show that a delta inulin-derived microparticle adjuvant, Advax, is an additional class of adjuvant that functions as an amplifier of in-built adjuvant activity within the antigens themselves. Advax enhances different types of adaptive immune response dependent on the antigen's own in-built adjuvant properties, confirming Advax's utility as a general purpose vaccine adjuvant.

Human Phase 1 trial of low-dose inactivated seasonal influenza vaccine formulated with Advax™ delta inulin adjuvant

Influenza vaccines are usually non-adjuvanted but addition of adjuvant may improve immunogenicity and permit dose-sparing, critical for vaccine supply in the event of an influenza pandemic. The aim of this first-in-man study was to determine the effect of delta inulin adjuvant on the safety and immunogenicity of a reduced dose seasonal influenza vaccine. Healthy male and female adults aged 18-65years were recruited to participate in a randomized controlled study to compare the safety, tolerability and immunogenicity of a reduced-dose 2007 Southern Hemisphere trivalent inactivated influenza vaccine formulated with Advax™ delta inulin adjuvant (LTIV+Adj) when compared to a full-dose of the standard TIV vaccine which does not contain an adjuvant. LTIV+Adj provided equivalent immunogenicity to standard TIV vaccine as assessed by hemagglutination inhibition (HI) assays against each vaccine strain as well as against a number of heterosubtypic strains. HI responses were sustained at 3months post-immunisation in both groups. Antibody landscapes against a large panel of H3N2 influenza viruses showed distinct age effects whereby subjects over 40years old had a bimodal baseline HI distribution pattern, with the highest HI titers against the very oldest H3N2 isolates and with a second HI peak against influenza isolates from the last 5-10years. By contrast, subjects >40years had a unimodal baseline HI distribution with peak recognition of H3N2 isolates from approximately 20years ago. The reduced dose TIV vaccine containing Advax adjuvant was well tolerated and no safety issues were identified. Hence, delta inulin may be a useful adjuvant for use in seasonal or pandemic influenza vaccines. Australia New Zealand Clinical Trial Registry: ACTRN12607000599471.

Development of a SARS Coronavirus Vaccine from Recombinant Spike Protein Plus Delta Inulin Adjuvant

Given periodic outbreaks of fatal human infections caused by coronaviruses, development of an optimal coronavirus vaccine platform capable of rapid production is an ongoing priority. This chapter describes the use of an insect cell expression system for rapid production of a recombinant vaccine against severe acute respiratory syndrome coronavirus (SARS). Detailed methods are presented for expression, purification, and release testing of SARS recombinant spike protein antigen, followed by adjuvant formulation and animal testing. The methods herein described for rapid development of a highly protective SARS vaccine are equally suited to rapid development of vaccines against other fatal human coronavirus infections, e.g., the MERS coronavirus.

Advax™, a novel microcrystalline polysaccharide particle engineered from delta inulin, provides robust adjuvant potency together with tolerability and safety

There is an ongoing need for new adjuvants to facilitate development of vaccines against HIV, tuberculosis, malaria and cancer, amongst many others. Unfortunately, the most potent adjuvants are often associated with toxicity and safety issues. Inulin, a plant-derived polysaccharide, has no immunological activity in its native soluble form but when crystallized into a stable microcrystalline particulate from (delta inulin) acquires potent adjuvant activity. Delta inulin has been shown to enhance humoral and cellular immune responses against a broad range of co-administered viral, bacterial, parasitic and toxin antigens. Inulin normally crystallizes as large heterogeneous particles with a broad size distribution and variable solubility temperatures. To ensure reproducible delta inulin particles with a consistent size distribution and temperature of solubility, a current Good Manufacturing Practice (cGMP) process was designed to produce Advax™ adjuvant. In its cCMP form, Advax™ adjuvant has proved successful in human trials of vaccines against seasonal and pandemic influenza, hepatitis B and insect sting anaphylaxis, enhancing antibody and T-cell responses while being safe and well tolerated. Advax™ adjuvant represents a novel human adjuvant that enhances both humoral and cellular immunity. This review describes the discovery and development of Advax™ adjuvant and research into its unique mechanism of action.

A Lentiviral Vector Expressing Japanese Encephalitis Virus-like Particles Elicits Broad Neutralizing Antibody Response in Pigs

Background

Japanese encephalitis virus (JEV) is the major cause of viral encephalitis in Southeast Asia. Vaccination of domestic pigs has been suggested as a “one health” strategy to reduce viral disease transmission to humans. The efficiency of two lentiviral TRIP/JEV vectors expressing the JEV envelope prM and E glycoproteins at eliciting protective humoral response was assessed in a mouse model and piglets.

Methodology/Principal Findings

A gene encoding the envelope proteins prM and E from a genotype 3 JEV strain was inserted into a lentiviral TRIP vector. Two lentiviral vectors TRIP/JEV were generated, each expressing the prM signal peptide followed by the prM protein and the E glycoprotein, the latter being expressed either in its native form or lacking its two C-terminal transmembrane domains. In vitro transduction of cells with the TRIP/JEV vector expressing the native prM and E resulted in the efficient secretion of virus-like particles of Japanese encephalitis virus. Immunization of BALB/c mice with TRIP/JEV vectors resulted in the production of IgGs against Japanese encephalitis virus, and the injection of a second dose one month after the prime injection greatly boosted antibody titers. The TRIP/JEV vectors elicited neutralizing antibodies against JEV strains belonging to genotypes 1, 3, and 5. Immunization of piglets with two doses of the lentiviral vector expressing JEV virus-like particles led to high titers of anti-JEV antibodies, that had efficient neutralizing activity regardless of the JEV genotype tested.

Conclusions/Significance

Immunization of pigs with the lentiviral vector expressing JEV virus-like particles is particularly efficient to prime antigen-specific humoral immunity and trigger neutralizing antibody responses against JEV genotypes 1, 3, and 5. The titers of neutralizing antibodies elicited by the TRIP/JEV vector are sufficient to confer protection in domestic pigs against different genotypes of JEV and this could be of a great utility in endemic regions where more than one genotype is circulating.

Japanese encephalitis virus is the etiologic agent of the most medically important viral encephalitis in South Asia with thousands of deaths per year. The virus is maintained in an enzootic cycle between Culex mosquitoes and amplifying vertebrate hosts, such as wild boars and pigs. Vaccination of domestic pigs has been suggested as a strategy to reduce viral disease transmission to humans, in line with the now-called “One Health” concept. Lentiviral gene transfer vectors represent a novel vaccination platform with an unprecedented ability to induce robust humoral immunity in various animal species. In our study, we demonstrated that immunization of pigs with a recombinant lentiviral vector expressing virus-like particles of Japanese encephalitis virus is particularly efficient at eliciting specific humoral immunity. The titers of neutralizing antibodies elicited by the lentiviral vector are sufficient to confer protection in domestic pigs against the different genotypes of Japanese encephalitis virus observed in Asia.

Advax delta inulin adjuvant overcomes immune immaturity in neonatal mice thereby allowing single-dose influenza vaccine protection

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A single dose of Advax-adjuvanted influenza vaccine in 7-day-old pups protected against lethal influenza infection.

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Advax adjuvant enhanced both B-cell and T-cell memory in neonates.

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Influenza protection in Advax-immunized neonates was dependent on memory B-cells.

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Advax adjuvant confirmed to be safe and well tolerated in neonates.

Neonates are at high risk for influenza morbidity and mortality due to immune immaturity and lack of priming by prior influenza virus exposure. Inactivated influenza vaccines are ineffective in infants under six months and to provide protection in older children generally require two doses given a month apart. This leaves few options for rapid protection of infants, e.g. during an influenza pandemic. We investigated whether Advax™, a novel polysaccharide adjuvant based on delta inulin microparticles could help overcome neonatal immune hypo-responsiveness. We first tested whether it was possible to use Advax to obtain single-dose vaccine protection of neonatal pups against lethal influenza infection. Inactivated influenza A/H1N1 vaccine (iH1N1) combined with Advax™ adjuvant administered as a single subcutaneous immunization to 7-day-old mouse pups significantly enhanced serum influenza-specific IgM, IgG1, IgG2a and IgG2b levels and was associated with a 3–4 fold increase in the frequency of splenic influenza-specific IgM and IgG antibody secreting cells. Pups immunized with Advax had significantly higher splenocyte influenza-stimulated IFN-γ, IL-2, IL-4, and IL-10 production by CBA and a 3–10 fold higher frequency of IFN-γ, IL-2, IL-4 or IL-17 secreting T cells by ELISPOT. Immunization with iH1N1 + Advax induced robust protection of pups against virus challenge 3 weeks later, whereas pups immunized with iH1N1 antigen alone had no protection. Protection by Advax-adjuvanted iH1N1 was dependent on memory B cells rather than memory T cells, with no protection in neonatal μMT mice that are B-cell deficient. Hence, Advax adjuvant overcame neonatal immune hypo-responsiveness and enabled single-dose protection of pups against otherwise lethal influenza infection, thereby supporting ongoing development of Advax™ as a neonatal vaccine adjuvant.

Delta Inulin Adjuvant Enhances Plasmablast Generation, Expression of Activation-Induced Cytidine Deaminase and B-Cell Affinity Maturation in Human Subjects Receiving Seasonal Influenza Vaccine

There is a major need for new adjuvants to improve the efficacy of seasonal and pandemic influenza vaccines. Advax is a novel polysaccharide adjuvant based on delta inulin that has been shown to enhance the immunogenicity of influenza vaccine in animal models and human clinical trials. To better understand the mechanism for this enhancement, we sought to assess its effect on the plasmablast response in human subjects. This pilot study utilised cryopreserved 7 day post-vaccination (7dpv) peripheral blood mononuclear cell samples obtained from a subset of 25 adult subjects from the FLU006-12 trial who had been immunized intramuscularly with a standard dose of 2012 trivalent inactivated influenza vaccine (TIV) alone (n=9 subjects) or combined with 5mg (n=8) or 10mg (n=8) of Advax adjuvant. Subjects receiving Advax adjuvant had increased 7dpv plasmablasts, which in turn exhibited a 2-3 fold higher rate of non-silent mutations in the B-cell receptor CDR3 region associated with higher expression of activation-induced cytidine deaminase (AID), the major enzyme controlling BCR affinity maturation. Together, these data suggest that Advax adjuvant enhances influenza immunity in immunized subjects via multiple mechanisms including increased plasmablast generation, AID expression and CDR3 mutagenesis resulting in enhanced BCR affinity maturation and increased production of high avidity antibody. How Advax adjuvant achieves these beneficial effects on plasmablasts remains the subject of ongoing investigation.

10-valent pneumococcal non-typeable Haemophilus influenzae protein-D conjugate vaccine (PHiD-CV) induces memory B cell responses in healthy Kenyan toddlers

Memory B cells are long‐lived and could contribute to persistence of humoral immunity by maintaining the plasma‐cell pool or making recall responses upon re‐exposure to an antigen. We determined the ability of a pneumococcal conjugate vaccine to induce anti‐pneumococcal memory B cells. Frequencies of memory B cells against pneumococcal capsular polysaccharides from serotypes 1, 6B, 14, 19F and 23F were determined by cultured B cell enzyme‐linked immunospot (ELISPOT) in 35 children aged 12–23 months who received pneumococcal non‐typeable Haemophilus influenzae protein‐D conjugate vaccine (PHiD‐CV). The relationships between plasma antibodies and memory B cell frequencies were also assessed. After two doses of PHiD‐CV, the proportion of subjects with detectable memory B cells against pneumococcal capsular polysaccharides increased significantly for serotypes 1 (3–45%; P < 0·01), 19F (21–66%; P < 0·01) and 23F (13–36%; P = 0·02), but not serotypes 6B (24–42%; P = 0·24) and 14 (21–40%; P = 0·06). Correlations between antibodies and memory B cells were weak. Carriage of serotype 19F at enrolment was associated with poor memory B cell responses against this serotype at subsequent time‐points (day 30: non‐carriers, 82% versus carriers, 0%, P < 0·01; day 210: non‐carriers, 72% versus carriers, 33%, P = 0·07). PHiD‐CV is capable of inducing memory B cells against some of the component pneumococcal capsular polysaccharides.

Identification and characterisation of T-cell epitopes for incorporation into dendritic cell-delivered Listeria vaccines

Dendritic cells loaded with antigenic peptides, because of their safety and robust immune stimulation, would be ideal for induction of immunity to protect against listeriosis. However, there is no currently accepted method to predict which peptides derived from the Listeria proteome might confer protection. While elution of peptides from MHC molecules after Listeria infection yields high-affinity immune-dominant epitopes, these individual epitopes did not reliably confer Listeria protection. Instead we applied bioinformatic predictions of MHC class I and II epitopes to generate antigenic peptides that were then formulated with Advax™, a novel polysaccharide particulate adjuvant able to enhance cross-presentation prior to being screened for their ability to induce protective T-cell responses. A combination of at least four intermediate strength MHC-I binding epitopes and one weak MHC-II binding epitope when expressed in a single peptide sequence and formulated with Advax adjuvant induced a potent T-cell response and high TNF-α and IL-12 production by dendritic cells resulting in robust listeriosis protection in susceptible mice. This T-cell vaccine approach might be useful for the design of vaccines to protect against listeriosis or other intracellular infections.

A gold glyco-nanoparticle carrying a Listeriolysin O peptide and formulated with Advax™ delta inulin adjuvant induces robust T-cell protection against listeria infection

In the search for an effective vaccine against the human pathogen, Listeria monocytogenes (Listeria), gold glyconanoparticles (GNP) loaded with a listeriolysin O peptide LLO91-99 (GNP-LLO) were used to immunise mice, initially using a dendritic cell (DC) vaccine approach, but subsequently using a standard parenteral immunisation approach. To enhance vaccine immunogenicity a novel polysaccharide adjuvant based on delta inulin (Advax™) was also co-formulated with the GNP vaccine. Confirming previous results, DC loaded in vitro with GNP-LLO provided better protection against listeriosis than DC loaded in vitro using free LLO peptide. The immunogenicity of GNP-LLO loaded DC vaccines was further increased by addition of Advax™ adjuvant. However, as DC vaccines are expensive and impracticable for prophylactic use, we next asked whether the same GNP-LLO antigen could be used to directly target DC in vivo. Immunisation of mice with GNP-LLO plus Advax™ adjuvant induced LLO-specific T-cell immunity and protection against Listeria challenge. Protection correlated with an increased frequency of splenic CD4(+) and CD8(+) T cells, NK cells and CD8α(+) DC, and Th1 cytokine production (IL-12, IFN-γ, TNF-α, and MCP-1), post-challenge. Enhanced T-cell epitope recruitment post-challenge was seen in the groups that received Advax™ adjuvant. Immunisation with GNP-LLO91-99 plus Advax™ adjuvant provided equally robust Listeria protection as the best DC vaccine strategy but without the complexity and cost, making this a highly promising strategy for development of a prophylactic vaccine against listeriosis.

CD8+ T cells complement antibodies in protecting against yellow fever virus

The attenuated yellow fever (YF) vaccine (YF-17D) was developed in the 1930s, yet little is known about the protective mechanisms underlying its efficiency. In this study, we analyzed the relative contribution of cell-mediated and humoral immunity to the vaccine-induced protection in a murine model of YF-17D infection. Using different strains of knockout mice, we found that CD4(+) T cells, B cells, and Abs are required for full clinical protection of vaccinated mice, whereas CD8(+) T cells are dispensable for long-term survival after intracerebral challenge. However, by analyzing the immune response inside the infected CNS, we observed an accelerated T cell influx into the brain after intracerebral challenge of vaccinated mice, and this T cell recruitment correlated with improved virus control in the brain. Using mice deficient in B cells we found that, in the absence of Abs, YF vaccination can still induce some antiviral protection, and in vivo depletion of CD8(+) T cells from these animals revealed a pivotal role for CD8(+) T cells in controlling virus replication in the absence of a humoral response. Finally, we demonstrated that effector CD8(+) T cells also contribute to viral control in the presence of circulating YF-specific Abs. To our knowledge, this is the first time that YF-specific CD8(+) T cells have been demonstrated to possess antiviral activity in vivo.

Safety and immunogenicity of a delta inulin-adjuvanted inactivated Japanese encephalitis virus vaccine in pregnant mares and foals

In 2011, following severe flooding in Eastern Australia, an unprecedented epidemic of equine encephalitis occurred in South-Eastern Australia, caused by Murray Valley encephalitis virus (MVEV) and a new variant strain of Kunjin virus, a subtype of West Nile virus (WNV_KUN). This prompted us to assess whether a delta inulin-adjuvanted, inactivated cell culture-derived Japanese encephalitis virus (JEV) vaccine (JE-ADVAX™) could be used in horses, including pregnant mares and foals, to not only induce immunity to JEV, but also elicit cross-protective antibodies against MVEV and WNV_KUN. Foals, 74–152 days old, received two injections of JE-ADVAX™. The vaccine was safe and well-tolerated and induced a strong JEV-neutralizing antibody response in all foals. MVEV and WNV_KUN antibody cross-reactivity was seen in 33% and 42% of the immunized foals, respectively. JE-ADVAX™ was also safe and well-tolerated in pregnant mares and induced high JEV-neutralizing titers. The neutralizing activity was passively transferred to their foals via colostrum. Foals that acquired passive immunity to JEV via maternal antibodies then were immunized with JE-ADVAX™ at 36–83 days of age, showed evidence of maternal antibody interference with low peak antibody titers post-immunization when compared to immunized foals of JEV-naïve dams. Nevertheless, when given a single JE-ADVAX™ booster immunization as yearlings, these animals developed a rapid and robust JEV-neutralizing antibody response, indicating that they were successfully primed to JEV when immunized as foals, despite the presence of maternal antibodies. Overall, JE-ADVAX™ appears safe and well-tolerated in pregnant mares and young foals and induces protective levels of JEV neutralizing antibodies with partial cross-neutralization of MVEV and WNV_KUN.

Severe acute respiratory syndrome-associated coronavirus vaccines formulated with delta inulin adjuvants provide enhanced protection while ameliorating lung eosinophilic immunopathology

Although the severe acute respiratory syndrome-associated coronavirus (SARS-CoV) epidemic was controlled by nonvaccine measures, coronaviruses remain a major threat to human health. The design of optimal coronavirus vaccines therefore remains a priority. Such vaccines present major challenges: coronavirus immunity often wanes rapidly, individuals needing to be protected include the elderly, and vaccines may exacerbate rather than prevent coronavirus lung immunopathology. To address these issues, we compared in a murine model a range of recombinant spike protein or inactivated whole-virus vaccine candidates alone or adjuvanted with either alum, CpG, or Advax, a new delta inulin-based polysaccharide adjuvant. While all vaccines protected against lethal infection, addition of adjuvant significantly increased serum neutralizing-antibody titers and reduced lung virus titers on day 3 postchallenge. Whereas unadjuvanted or alum-formulated vaccines were associated with significantly increased lung eosinophilic immunopathology on day 6 postchallenge, this was not seen in mice immunized with vaccines formulated with delta inulin adjuvant. Protection against eosinophilic immunopathology by vaccines containing delta inulin adjuvants correlated better with enhanced T-cell gamma interferon (IFN-γ) recall responses rather than reduced interleukin-4 (IL-4) responses, suggesting that immunopathology predominantly reflects an inadequate vaccine-induced Th1 response. This study highlights the critical importance for development of effective and safe coronavirus vaccines of selection of adjuvants based on the ability to induce durable IFN-γ responses.

IMPORTANCE

Coronaviruses such as SARS-CoV and Middle East respiratory syndrome-associated coronavirus (MERS-CoV) cause high case fatality rates and remain major human public health threats, creating a need for effective vaccines. While coronavirus antigens that induce protective neutralizing antibodies have been identified, coronavirus vaccines present a unique problem in that immunized individuals when infected by virus can develop lung eosinophilic pathology, a problem that is further exacerbated by the formulation of SARS-CoV vaccines with alum adjuvants. This study shows that formulation of SARS-CoV spike protein or inactivated whole-virus vaccines with novel delta inulin-based polysaccharide adjuvants enhances neutralizing-antibody titers and protection against clinical disease but at the same time also protects against development of lung eosinophilic immunopathology. It also shows that immunity achieved with delta inulin adjuvants is long-lived, thereby overcoming the natural tendency for rapidly waning coronavirus immunity. Thus, delta inulin adjuvants may offer a unique ability to develop safer and more effective coronavirus vaccines.

Immunogenicity and safety of Advax™, a novel polysaccharide adjuvant based on delta inulin, when formulated with hepatitis B surface antigen: a randomized controlled Phase 1 study

There is a need for additional safe and effective human vaccine adjuvants. Advax™ is a novel adjuvant produced from semi-crystalline particles of delta inulin. In animal studies Advax enhanced humoral and cellular immunity to hepatitis B surface antigen (HBsAg) without inducing local or systemic reactogenicity. This first-in-man Phase 1 clinical trial tested the safety and tolerability of three intramuscular doses of HBsAg formulated with Advax in a group of healthy adult subjects. Advax was well tolerated with injection site pain scores not significantly different to subjects receiving HBsAg alone and no adverse events were reported in subjects that received Advax. Seroprotection and HBsAb geometric mean titers (GMT) after three immunizations were higher in the Advax 5mg (seroprotection 5/6, 83.3%, GMT 40.7, 95% CI 11.9-139.1) and 10mg (seroprotection 4/5, 80%, GMT 51.6, 95% CI 10.0-266.2) groups versus HBsAg alone (seroprotection 1/5, 20%, GMT 4.1, 95% CI 1.3-12.8). Similarly the proportion of subjects with positive CD4 T-cell responses to HBsAg was higher in the Advax 5mg (4/6, 67%) and Advax 10mg (4/5, 80%) groups versus HBsAg alone (1/5, 20%). These results confirm the safety, tolerability and immunogenicity of Advax adjuvant observed in preclinical studies. Advax may represent a suitable replacement for alum adjuvants in prophylactic human vaccines subject to confirmation of current results in larger studies. Australia and New Zealand Clinical Trial Registry: ACTRN12607000598482.

Inulin crystal initiation via a glucose-fructose cross-link of adjacent polymer chains: atomic force microscopy and static molecular modelling

Semi-crystalline microparticles of inulin (MPI) have clinical utility as potent human vaccine adjuvants but their relevant surface structure and crystal assembly remain undefined. We show inulin crystal surfaces to resemble multi-layered, discoid radial spherulites resulting from very rapid formation of complex tertiary structures, implying directed crystal initiation. Physical and in silico molecular modelling of unit cells confirm steric feasibility of initiation by hydrogen-bonded cross-linking of terminal glucose to a fructose of another chain, mimicking bonding in sucrose crystals. A strong, chelate-like dual H-bond is proposed to compel the known antiparallel alignment of inulin chains. Such cross-linking would require one extra fructose per chain in the native inulin crystal, as observed. Completion of five H-bonded internal ring-domains would 'lock in' each new 6-fructose structural unit of each antiparallel helix pair to create a new isoform. All known properties of inulin isoforms follow readily from these concepts.

A single immunization with inactivated H1N1 influenza vaccine formulated with delta inulin adjuvant (Advax™) overcomes pregnancy-associated immune suppression and enhances passive neonatal protection

Pregnant women and neonates represent high-risk groups for influenza infection, and in general have suppressed responses to standard influenza vaccines due to pregnancy-associated immune suppression and immune system immaturity, respectively. We therefore wished to test whether addition of Advax™, a polysaccharide adjuvant based on delta inulin, to an inactivated influenza vaccine (A/H1N1/PR8) administered during pregnancy would safely enhance vaccine immunogenicity and thereby provide improved protection of pregnant mothers and their newborns. Pregnant mice received a single intramuscular injection of β-propiolactone-inactivated H1N1 antigen alone or with Advax adjuvant. Pregnant dams receiving Advax-adjuvanted vaccine exhibited significantly increased serum and breast milk anti-influenza IgG titers. This translated into higher serum anti-influenza IgG titers in the pups of these dams. Complete protection was seen in pups of dams that received Advax-adjuvanted vaccine whereas no survival was seen in pups of control mothers or mothers immunized with unadjuvanted influenza vaccine. Cross-fostering studies confirmed that enhanced protection of pups of dams that received Advax-adjuvanted vaccine was mediated by enhanced transfer of maternal IgG to the pups via breast-feeding. The delta inulin adjuvant was not associated with any reproductive or developmental adverse effects. This study shows that Advax adjuvant was safe when administered with influenza vaccine during pregnancy and provided protection of pups via enhanced breast milk transfer of anti-influenza antibodies, not seen with administration of unadjuvanted vaccine.

Gamma ray sterilization of delta inulin adjuvant particles (Advax™) makes minor, partly reversible structural changes without affecting adjuvant activity

We earlier identified a developmental series of seven isoforms/polymorphs of microparticulate inulin by comparing non-covalent bonding strengths. Their pharmaceutical utility lies in the modulation of cellular immunity, exploited as vaccine adjuvants (Advax™) especially for delta inulin (DI). As such particles cannot be sterilized by filtration we explore the effect of (60)Co gamma radiation (GR) on inulin isoforms, particularly DI. Its adjuvant activity and overt physical properties were unaffected by normal GR sterilizing doses (up to 25kGy). Heating irradiated isoform suspensions near their critical dissolution temperature revealed increased solubility deduced to reflect a single lethal event in one component of a multi-component structure. Local oxidative effects of GR on DI were not found. The observed DI loss was almost halved by re-annealing at the critical temperature: surviving inulin chains apparently reassemble into smaller amounts of the original type of structure. Colorimetric tetrazolium assay revealed increases in reducing activity after GR of raw inulin powder, which yielded DI with normal physical properties but only 25% normal recovery yet 4× normal reducing ability, implying final retention of some GR-changed inulin chains. These findings suggest minimal inulin chain cleavage and confirm that GR may be a viable strategy for terminal sterilization of microparticulate inulin adjuvants.

Inulin isoforms differ by repeated additions of one crystal unit cell

Inulin isoforms, especially delta inulin, are important biologically as immune activators and clinically as vaccine adjuvants. In exploring action mechanisms, we previously found regular increments in thermal properties of the seven-member inulin isoform series that suggested regular additions of some energetic structural unit. Because the previous isolates carried additional longer chains that masked defining ranges, these were contrasted with new isoform isolates comprising only inulin chain lengths defining that isoform. The new series began with 19 fructose units per chain (alpha-1 inulin), increasing regularly by 6 fructose units per isoform. Thus the 'energetic unit' equates to 6 fructose residues per chain. All isoforms showed indistinguishable X-ray diffraction patterns that were also identical with known inulin crystals. We conclude that an 'energetic unit' equates to one helix turn of 6 fructose units per chain as found in one unit cell of the inulin crystal. Each isoform chain comprised progressively more helix turns plus one additional fructose and glucose residues per chain.

Internal ribosome entry site-based attenuation of a flavivirus candidate vaccine and evaluation of the effect of beta interferon coexpression on vaccine properties

Infectious clone technologies allow the rational design of live attenuated viral vaccines with the possibility of vaccine-driven coexpression of immunomodulatory molecules for additional vaccine safety and efficacy. The latter could lead to novel strategies for vaccine protection against infectious diseases where traditional approaches have failed. Here we show for the flavivirus Murray Valley encephalitis virus (MVEV) that incorporation of the internal ribosome entry site (IRES) of Encephalomyocarditis virus between the capsid and prM genes strongly attenuated virulence and that the resulting bicistronic virus was both genetically stable and potently immunogenic. Furthermore, the novel bicistronic genome organization facilitated the generation of a recombinant virus carrying an beta interferon (IFN-β) gene. Given the importance of IFNs in limiting virus dissemination and in efficient induction of memory B and T cell antiviral immunity, we hypothesized that coexpression of the cytokine with the live vaccine might further increase virulence attenuation without loss of immunogenicity. We found that bicistronic mouse IFN-β coexpressing MVEV yielded high virus and IFN titers in cultured cells that do not respond to the coexpressed IFN. However, in IFN response-sufficient cell cultures and mice, the virus produced a self-limiting infection. Nevertheless, the attenuated virus triggered robust innate and adaptive immune responses evidenced by the induced expression of Mx proteins (used as a sensitive biomarker for measuring the type I IFN response) and the generation of neutralizing antibodies, respectively. IMPORTANCE The family Flaviviridae includes a number of important human pathogens, such as Dengue virus, Yellow fever virus, Japanese encephalitis virus, West Nile virus, and Hepatitis C virus. Flaviviruses infect large numbers of individuals on all continents. For example, as many as 100 million people are infected annually with Dengue virus, and 150 million people suffer a chronic infection with Hepatitis C virus. However, protective vaccines against dengue and hepatitis C are still missing, and improved vaccines against other flaviviral diseases are needed. The present study investigated the effects of a redesigned flaviviral genome and the coexpression of an antiviral protein (interferon) on virus replication, pathogenicity, and immunogenicity. Our findings may aid in the rational design of a new class of well-tolerated and safe vaccines.

Development of a small animal peripheral challenge model of Japanese encephalitis virus using interferon deficient AG129 mice and the SA14-14-2 vaccine virus strain

Japanese encephalitis virus (JEV) is the most common cause of viral encephalitis in Asia, and it is increasingly a global public health concern due to its recent geographic expansion. While commercial vaccines are available and used in some endemic countries, JEV continues to be a public health problem, with 50,000 cases reported annually. Research with virulent JEV in mouse models to develop new methods of prevention and treatment is restricted to BSL-3 containment facilities, confining these studies to investigators with access to these facilities. We have developed an adult small animal peripheral challenge model using interferon-deficient AG129 mice and the JEV live-attenuated vaccine SA14-14-2, thus requiring only BSL-2 containment. A low dose of virus (10PFU/0.1ml) induced 100% morbidity in infected mice. Increased body temperatures measured by implantable temperature transponders correlated with an increase in infectious virus and viral RNA in serum, spleen and brain as well as an increase in pro-inflammatory markers measured by a 58-biomarker multi-analyte profile (MAP) constructed during the course of infection. In the future, the MAP measurements can be used as a baseline for comparison in order to better assess the inhibition of disease progression by other prophylactic and therapeutic agents. The use of the AG129/JEV SA14-14-2 animal model makes vaccine and therapeutic studies feasible for laboratories with limited biocontainment facilities.

The polysaccharide inulin is characterized by an extensive series of periodic isoforms with varying biological actions

In studying the molecular basis for the potent immune activity of previously described gamma and delta inulin particles and to assist in production of inulin adjuvants under Good Manufacturing Practice, we identified five new inulin isoforms, bringing the total to seven plus the amorphous form. These isoforms comprise the step-wise inulin developmental series amorphous → alpha-1 (AI-1) → alpha-2 (AI-2) → gamma (GI) → delta (DI) → zeta (ZI) → epsilon (EI) → omega (OI) in which each higher isoform can be made either by precipitating dissolved inulin or by direct conversion from its precursor, both cases using regularly increasing temperatures. At higher temperatures, the shorter inulin polymer chains are released from the particle and so the key difference between isoforms is that each higher isoform comprises longer polymer chains than its precursor. An increasing trend of degree of polymerization is confirmed by end-group analysis using (1)H nuclear magnetic resonance spectroscopy. Inulin isoforms were characterized by the critical temperatures of abrupt phase-shifts (solubilizations or precipitations) in water suspensions. Such (aqueous) "melting" or "freezing" points are diagnostic and occur in strikingly periodic steps reflecting quantal increases in noncovalent bonding strength and increments in average polymer lengths. The (dry) melting points as measured by modulated differential scanning calorimetry similarly increase in regular steps. We conclude that the isoforms differ in repeated increments of a precisely repeating structural element. Each isoform has a different spectrum of biological activities and we show the higher inulin isoforms to be more potent alternative complement pathway activators.

Memory B cells: a proposed new immunological correlate for protective efficacy of Japanese encephalitis vaccine

Japanese encephalitis (JE) virus requires dissemination within the host via the circulation for disease development. Thus, a serum-neutralizing antibody is an effective factor to protect against disease. Current licensed JE vaccines induce neutralizing antibodies and titers of 1:10 or higher are the recommended immunological correlate of protection. In this paper, the authors demonstrated, using a highly susceptible knockout mouse model, that memory B cells are required for disease protection and that detectable neutralizing antibodies at the time of challenge are dispensable. The authors proposes that the extent of memory B cells would be an alternative and better immunological correlate for evaluating the efficacy of JE vaccine candidates in clinical trials.

An inactivated cell culture Japanese encephalitis vaccine (JE-ADVAX) formulated with delta inulin adjuvant provides robust heterologous protection against West Nile encephalitis via cross-protective memory B cells and neutralizing antibody

West Nile virus (WNV), currently the cause of a serious U.S. epidemic, is a mosquito-borne flavivirus and member of the Japanese encephalitis (JE) serocomplex. There is currently no approved human WNV vaccine, and treatment options remain limited, resulting in significant mortality and morbidity from human infection. Given the availability of approved human JE vaccines, this study asked whether the JE-ADVAX vaccine, which contains an inactivated cell culture JE virus antigen formulated with Advax delta inulin adjuvant, could provide heterologous protection against WNV infection in wild-type and β2-microglobulin-deficient (β2m(-/-)) murine models. Mice immunized twice or even once with JE-ADVAX were protected against lethal WNV challenge even when mice had low or absent serum cross-neutralizing WNV titers prior to challenge. Similarly, β2m(-/-) mice immunized with JE-ADVAX were protected against lethal WNV challenge in the absence of CD8(+) T cells and prechallenge WNV antibody titers. Protection against WNV could be adoptively transferred to naive mice by memory B cells from JE-ADVAX-immunized animals. Hence, in addition to increasing serum cross-neutralizing antibody titers, JE-ADVAX induced a memory B-cell population able to provide heterologous protection against WNV challenge. Heterologous protection was reduced when JE vaccine antigen was administered alone without Advax, confirming the importance of the adjuvant to induction of cross-protective immunity. In the absence of an approved human WNV vaccine, JE-ADVAX could provide an alternative approach for control of a major human WNV epidemic.