Adjuvants for Pandemic Influenza Vaccines

Immunogenicity of Enhanced Influenza Vaccines Against Mismatched Influenza Strains in Older Adults: A Review of Randomized Controlled Trials

Antigenic drift is a major driver of viral evolution and a primary reason why influenza vaccines must be reformulated annually. Mismatch between vaccine and circulating viral strains negatively affects vaccine effectiveness and often contributes to higher rates of influenza-related hospitalizations and deaths, particularly in years dominated by A(H3N2). Several countries recommend enhanced influenza vaccines for older adults, who are at the highest risk of severe influenza complications and mortality. The immunogenicity of enhanced vaccines against heterologous A(H3N2) strains has been examined in nine studies to date. In six studies, an enhanced, licensed MF59-adjuvanted trivalent inactivated influenza vaccine (aIIV3) consistently increased heterologous antibody titers relative to standard influenza vaccine, with evidence of a broad heterologous immune response across multiple genetic clades. In one study, licensed high-dose trivalent inactivated influenza vaccine (HD-IIV3) also induced higher heterologous antibody titers than standard influenza vaccine. In a study comparing a higher dose licensed quadrivalent recombinant influenza vaccine (RIV4) with HD-IIV3 and aIIV3, no significant differences in antibody titers against a heterologous strain were observed, although seroconversion rates were higher with RIV4 versus comparators. With the unmet medical need for improved influenza vaccines, the paucity of studies especially with enhanced vaccines covering mismatched strains highlights a need for further investigation of cross-protection in older adults.

Global Pandemic Preparedness: Optimizing Our Capabilities and the Influenza Experience

The coronavirus disease 2019 (COVID-19) pandemic has prompted rapid investigation and deployment of vaccine platforms never before used to combat human disease. The severe impact on the health system and the high economic cost of non-pharmaceutical interventions, such as lockdowns and international border closures employed to mitigate the spread of COVID-19 prior to the arrival of effective vaccines, have led to calls for development and deployment of novel vaccine technologies as part of a “100-day response ambition” for the next pandemic. Prior to COVID-19, all of the pandemics (excluding HIV) in the past century have been due to influenza viruses, and influenza remains one of the most likely future pandemic threats along with new coronaviruses. New and emerging vaccine platforms are likely to play an important role in combatting the next pandemic. However, the existing well-established, proven platforms for seasonal and pandemic influenza manufacturing will also continue to be utilized to rapidly address the next influenza threat. The field of influenza vaccine manufacturing has a long history of successes, including approval of vaccines within approximately 100 days after WHO declaration of the A(H1N1) 2009 influenza pandemic. Moreover, many advances in vaccine science and manufacturing capabilities have been made in the past decade to optimize a rapid and timely response should a new influenza pandemic threat emerge.

Better Pandemic Influenza Preparedness through Adjuvant Technology Transfer: Challenges and Lessons Learned

Adequate global vaccine coverage during an influenza pandemic is essential to mitigate morbidity, mortality, and economic impact. Vaccine development and production needs to be sufficient to meet a vast global demand, requiring international cooperation and local vaccine production capacity, especially in resource-constrained countries. The use of adjuvants is one approach to augment the number of available vaccine doses and to overcome potential vaccine shortages. Appropriately selected adjuvant technologies can decrease the amount of vaccine antigen required per dose, may broaden or lengthen the conferred protection against disease, and may even allow protective single-dose vaccination. Here we describe a technology transfer collaboration between Switzerland and Indonesia that led to the establishment of a vaccine formulation platform in Surabaya which involved the transfer of equipment and expertise to enable research and development of adjuvanted vaccine formulations and delivery systems. This new Indonesian capability aims to facilitate local and regional access to know-how relating to adjuvanted vaccine formulations, thus promoting their application to local vaccine developers. In this review, we aim to share the “lessons learned” from this project to both support and inspire future scientific collaborations of a similar nature.

Respiratory Syncytial Virus F Subunit Vaccine With AS02 Adjuvant Elicits Balanced, Robust Humoral and Cellular Immunity in BALB/c Mice

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory illness, particularly in infants, the elderly, and immunocompromised adults. There is no licensed commercial vaccine against RSV. Importantly, formalin-inactivated RSV vaccines mediate enhanced respiratory disease. RSV fusion (F) protein with pre-fusion conformation is a promising candidate subunit vaccine. However, some problems remain to be solved, such as low immunogenicity and humoral immunity bias. Adjuvants can effectively enhance and adjust vaccine immune responses. In this study, we formulated pre-fusion RSV-F protein with the adjuvants, Alhydrogel, MF59, AS03, AS02, and glycol chitosan (GCS). We then conducted head-to-head comparisons of vaccine-induced immune responses in BALB/c mice. All adjuvanted vaccines enhanced antigen-specific and neutralizing antibody titers and viral clearance and gave an order of adjuvant activity: AS02 > AS03, MF59 > GCS, and Alhydrogel. Among them, AS02 elicited the highest antibody expression, which persisted until week 18. Moreover, AS02 significantly enhanced Th1 type immune response in immunized mice. Mice in the AS02 group also showed faster recovery from viral attacks in challenge tests. Further transcriptome analysis revealed that AS02 regulates immune balance by activating TLR-4 and promotes Th1-type immune responses. These results suggest that AS02 may be an excellent candidate adjuvant for RSV-F subunit vaccines. This study also provides valuable information regarding the effect of other adjuvants on immune responses of RSV-F subunit vaccines.

Inactivated pandemic 2009 H1N1 influenza A virus human vaccines have different efficacy after homologous challenge in the ferret model

Background

The 2009 pandemic H1N1 (A(H1N1)pdm09) influenza A virus (IAV) has replaced the previous seasonal H1N1 strain in humans and continues to circulate worldwide. The comparative performance of inactivated A(H1N1)pdm09 influenza vaccines remains of considerable interest. The objective of this study was to evaluate the efficacy of two licensed A(H1N1)pdm09 inactivated vaccines (AS03B adjuvanted split virion Pandemrix from GlaxoSmithKline and referred here as (V1) and non‐adjuvanted whole virion Celvapan from Baxter and referred here as (V2)) in ferrets as a pre‐clinical model for human disease intervention.

Methods

Naïve ferrets were divided into two groups (V1 and V2) and immunised intramuscularly with two different A/California/07/2009‐derived inactivated vaccines, V1 administered in a single dose and V2 administered in 2 doses separated by 21 days. Six weeks after the first immunisation, vaccinated animals and a non‐vaccinated control (NVC) group were intra‐nasally challenged with 10^6.5 TCID₅₀ of the isolate A/England/195/2009 A(H1N1)pdm09 with 99.1% amino acid identity to the vaccine strain. Clinical signs, lung histopathology, viral quantification and antibody responses were evaluated.

Results and Conclusions

Results revealed important qualitative differences in the performance of both inactivated vaccines in relation to protection against challenge with a comparable virus in a naive animal (ferret) model of human disease. Vaccine V1 limited and controlled viral shedding and reduced lower respiratory tract infection. In contrast, vaccine V2 did not control infection and animals showed sustained viral shedding and delayed lower respiratory infection, resulting in pulmonary lesions, suggesting lower efficacy of V2 vaccine.

[Adjuvants of influenza vaccines: new possibilities of using sulphated polysaccharides from marine brown algae.]

The review article presents the characteristics of the main adjuvant groups (mineral salts of aluminum, synthetic squalenebased adjuvants - MF59 and AS03, CpG-oligodeoxynucleotides, virosomes, polyoxidonium, sovidone) included in the licensed influenza vaccine. The main mechanisms of adjuvant action, advantages and disadvantages of these adjuvants are shown. The vaccines adjuvants in the phase of experimental studies and clinical trials (ISCOMs, Advax™, chitosan) are described too. Particular attention is paid to sulfated polysaccharides (fucoidans) from marine brown algae as vaccine adjuvants. Numerous results of their application in compositions of experimental vaccines are presented. The prospects of sulfated polysaccharides using in the design of influenza vaccines are estimated. These prospects are determined by high biocompatibility, low toxicity and good tolerance of the human body to fucoidans, as well as mechanisms of their adjuvant activity. Sulfated polysaccharides are agonists of toll-like receptors of innate immunity cells and powerful inducers of the cellular and humoral immune response, which is important for the development of influenza vaccines. The review is based on the information presented in the bibliographic and abstract databases of scientific publications, search engines and publishers: RSCI, Web of Science, Scopus, MEDLINE, Google Scholar, PubMed, Springer Nature, Elsevier and others.

Immunogenicity of Influenza Vaccines: Evidence for Differential Effect of Secondary Vaccination on Humoral and Cellular Immunity

While currently used influenza vaccines are designed to induce neutralizing antibodies, little is known on T cell responses induced by these vaccines. The 2009 pandemic provided us with the opportunity to evaluate the immune response to vaccination in a unique setting. We evaluated both antibody and T cell responses in a cohort of public health care workers (18–52 years) during two consecutive influenza seasons from 2009 to 2011 and compared the MF59-adjuvanted pandemic vaccine with the unadjuvanted seasonal subunit vaccine that included the pandemic strain [The study was registered in the Netherlands Trial Register (NTR2070)]. Antibody responses were determined in serum by a hemagglutination inhibition assay. Vaccine-specific T cell responses were evaluated by detecting IFN-γ producing peripheral blood mononuclear cells using whole influenza virus or vaccine-specific peptide pools as stimulating antigens. Mixed effects regression models were used to correct the data for influenza-specific pre-existing immunity due to previous infections or vaccinations and for age and sex. We show that one dose of the pandemic vaccine induced antibody responses sufficient for providing seroprotection and that the vaccine induced T cell responses. A second dose further increased antibody responses but not T cell responses. Nonetheless, both could be boosted by the seasonal vaccine in the subsequent season. Furthermore, we show that the seasonal vaccine alone is capable of inducing vaccine-specific T cell responses, despite the fact that the vaccine did not contain an adjuvant. In addition, residual antibody levels remained detectable for over 15 months, while T cell levels in the blood had contracted to baseline levels by that time. Hereby, we show that pandemic as well as seasonal vaccines induce both humoral and cellular responses, however, with a different profile of induction and waning, which has its implications for future vaccine design.

The parasite-derived rOv-ASP-1 is an effective antigen-sparing CD4+ T cell-dependent adjuvant for the trivalent inactivated influenza vaccine, and functions in the absence of MyD88 pathway

Vaccination remains the most cost-effective biomedical approach for controlling influenza disease. In times of pandemics, however, these vaccines cannot be produced in sufficient quantities for worldwide use by the current manufacturing capacities and practices. What is needed is the development of adjuvanted vaccines capable of inducing an adequate or better immune response at a decreased antigen dose. Previously we showed that the protein adjuvant rOv-ASP-1 augments influenza-specific antibody titers and survival after virus challenge in both young adult and old-age mice when administered with the trivalent inactivated influenza vaccine (IIV3). In this study we show that a reduced amount of rOv-ASP-1, with 40-times less IIV3 can also induce protection. Apparently the potency of the rOv-ASP-1 adjuvanted IIV3 vaccine is independent of the IIV3-specific Th1/Th2 associated antibody responses, and independent of the presence of HAI antibodies. However, CD4⁺ T helper cells were indispensable for the protection. Further, rOv-ASP-1 with or without IIV3 elicited the increased level of various chemokines, which are known chemoattractant for immune cells, into the muscle 4 h after immunization, and significantly induced the recruitment of monocytes, macrophages and neutrophils into the muscles. The recruited monocytes had higher expression of the activation marker MHCII on their surface as well as CXCR3 and CCR2; receptors for IP-10 and MCP-1, respectively. These results show that the rOv-ASP-1 adjuvant allows substantial antigen sparing of IIV3 by stimulating at the site of injection the accumulation of chemokines and the recruitment of immune cells that can augment the activation of CD4⁺ T cell immune responses, essential for the production of antibody responses. Protection elicited by the rOv-ASP-1 adjuvanted IIV3 vaccine also appears to function in the absence of MyD88-signaling. Future studies will attempt to delineate the precise mechanisms by which the rOv-ASP-1 adjuvanted IIV3 vaccine works.

Immunizing the Immune: Can We Overcome Influenza's Most Formidable Challenge?

The first human influenza virus was isolated more than 85 years ago, and several vaccine candidates were developed and tested soon after. Yet, controlling infections mediated by this respiratory pathogen continues to present a formidable challenge. Development of an effective influenza vaccine has been undermined by the dynamic nature of influenza viruses: these viruses have the unique capacity to escape pre-existing immunity. In this perspective, I highlight pre-existing immunity as a different, but related, hurdle that may actually lessen the effectiveness of influenza vaccine-induced immune responses. Specifically, I discuss the impact of pre-existing immunity on the generation of de novo B cell responses to influenza vaccination. As the influenza virus changes its major antigenic determinants, it creates new ones in the process. Our immune system adapts by targeting the new determinants. However, pre-existing antibodies and memory B cells interfere with the generation of de novo responses against these newly formed epitopes, rendering vaccines less effective. Overcoming such interference is essential for the development of more effective influenza vaccines.

Comparative effectiveness of H7N9 vaccines in healthy individuals

BACKGROUND

Avian H7N9 influenza viruses possess a potential pandemic threat to public health worldwide, and have caused severe infection and high mortality in humans. A series of clinical trials of H7N9 vaccines have been completed. Meta-analyses need to be performed to assess the immunogenicity and safety of H7N9 vaccines.

METHODS

Database research with defined selection criteria was conducted in PubMed, Cochrane Central Register of Controlled Trials, the World Health Organization's International Clinical Trials Registry Platform, ClinicalTrials.gov, etc. Data from randomized clinical trials regarding the immunogenicity and safety of H7N9 vaccines were collected and meta-analyzed.

RESULTS

For non-adjuvanted H7N9 vaccines, high dose formulations induced limited immunogenicity and increased the risk of local and systemic adverse events, simultaneously. For adjuvanted H7N9 vaccines, on the one hand, ISCOMATRIX, MF59, AS03 and aluminium adjuvants applied in H7N9 vaccines could improve immune responses effectively, and non-aluminium adjuvants had superior performance in saving vaccine dose; on the other hand, aluminium adjuvant had the advantages of safety amongst these adjuvants applied in H7N9 vaccines.

CONCLUSION

H7N9 influenza vaccines with adjuvant might represent the optimal available option in an influenza pandemic, at present.

Aluminum salts as an adjuvant for pre-pandemic influenza vaccines: a meta-analysis

Avian-origin H5/H7 influenza has the potential to cause the next influenza pandemic. Availability of effective vaccines is an essential part of pre-pandemic preparedness. However, avian influenza surface antigens are poorly immunogenic to humans, which necessitates the use of adjuvants to augment the immunogenicity of pre-pandemic influenza vaccines. Aluminum salts are approved, safe, and affordable adjuvants, but their adjuvanticity for influenza vaccines remains unverified. We conducted the first meta-analysis on this issue. A total of nine randomized controlled trials (2006-2013, 22 comparisons, 2,467 participants in total) compared aluminum-adjuvanted H5N1 vaccines versus non-adjuvanted counterparts. The weighted estimate for the ratio of the seroprotection rate after a single dose of H5N1 vaccine is 0.66 (95% CI: 0.53 to 0.83) by hemagglutination-inhibition assay or 0.56 (95% CI: 0.42 to 0.74) by neutralizing titer assay. The weighted estimate for the risk ratio of pain/tenderness at injection sites is 1.85 (95% CI: 1.56 to 2.19). The quality of evidence is low to very low for seroprotection (due to indirectness and potential reporting bias) and moderate for pain/tenderness (due to potential reporting bias), respectively. The significantly lower seroprotection rate after aluminum-adjuvanted H5N1 vaccines and the significantly higher risk of pain at injection sites indicate that aluminum salts decrease immunogenicity but increase local reactogenicity of pre-pandemic H5N1 vaccines in humans.

Cell-Based Systems Biology Analysis of Human AS03-Adjuvanted H5N1 Avian Influenza Vaccine Responses: A Phase I Randomized Controlled Trial

Background

Vaccine development for influenza A/H5N1 is an important public health priority, but H5N1 vaccines are less immunogenic than seasonal influenza vaccines. Adjuvant System 03 (AS03) markedly enhances immune responses to H5N1 vaccine antigens, but the underlying molecular mechanisms are incompletely understood.

Objective and Methods

We compared the safety (primary endpoint), immunogenicity (secondary), gene expression (tertiary) and cytokine responses (exploratory) between AS03-adjuvanted and unadjuvanted inactivated split-virus H5N1 influenza vaccines. In a double-blinded clinical trial, we randomized twenty adults aged 18–49 to receive two doses of either AS03-adjuvanted (n = 10) or unadjuvanted (n = 10) H5N1 vaccine 28 days apart. We used a systems biology approach to characterize and correlate changes in serum cytokines, antibody titers, and gene expression levels in six immune cell types at 1, 3, 7, and 28 days after the first vaccination.

Results

Both vaccines were well-tolerated. Nine of 10 subjects in the adjuvanted group and 0/10 in the unadjuvanted group exhibited seroprotection (hemagglutination inhibition antibody titer > 1:40) at day 56. Within 24 hours of AS03-adjuvanted vaccination, increased serum levels of IL-6 and IP-10 were noted. Interferon signaling and antigen processing and presentation-related gene responses were induced in dendritic cells, monocytes, and neutrophils. Upregulation of MHC class II antigen presentation-related genes was seen in neutrophils. Three days after AS03-adjuvanted vaccine, upregulation of genes involved in cell cycle and division was detected in NK cells and correlated with serum levels of IP-10. Early upregulation of interferon signaling-related genes was also found to predict seroprotection 56 days after first vaccination.

Conclusions

Using this cell-based systems approach, novel mechanisms of action for AS03-adjuvanted pandemic influenza vaccination were observed.

Trial Registration

ClinicalTrials.gov NCT01573312

Comparative assessment of humoral immune responses of aluminum hydroxide and oil-emulsion adjuvants in Influenza (H9N2) and Newcastle inactive vaccines to chickens

Context Adjuvants are compounds used in the preparation of inactive vaccines to enhance the immune response. Aluminum hydroxide (alum) is one of the first compounds approved by the Food and Drug Administration, which is used as adjuvants in vaccine products for humans. Montanide ISA 70 is an oil-emulsion adjuvant and is used in poultry inactive vaccines. Objective In this study, the effects of alum adjuvant on the efficiency and induction of immune response in inactive vaccines of Influenza and Newcastle are compared with those of ISA 70. Materials and methods Six groups of 7-d-old specific-pathogen-free chickens were inoculated with 0.3 ml of the prepared vaccines via the subcutaneous route in the neck. Immune response in each group after 7, 14, 21, 31, 41, and 45 d was evaluated using the technique of hemagglutination inhibition. Results The results were compared using SPSS software. Results showed that vaccines containing adjuvant ISA 70 depicted a higher increase in the immune response and adjuvant of 20% alum is similar to adjuvant of ISA 70 in boosting the immune system. There was no statistically significant difference between 10% and 20% alum, but these adjuvants are visibly different from ISA 70. Conclusion In conclusion, alum can be used as an easily accessible, harmless, and effective adjuvant; however, to increase the immune period using the inactive vaccines for poultry, more research would be necessary.

Enhanced Influenza Virus-Like Particle Vaccination with a Structurally Optimized RIG-I Agonist as Adjuvant

The molecular interaction between viral RNA and the cytosolic sensor RIG-I represents the initial trigger in the development of an effective immune response against infection with RNA viruses, resulting in innate immune activation and subsequent induction of adaptive responses. In the present study, the adjuvant properties of a sequence-optimized 5'-triphosphate-containing RNA (5'pppRNA) RIG-I agonist (termed M8) were examined in combination with influenza virus-like particles (VLP) (M8-VLP) expressing H5N1 influenza virus hemagglutinin (HA) and neuraminidase (NA) as immunogens. In combination with VLP, M8 increased the antibody response to VLP immunization, provided VLP antigen sparing, and protected mice from a lethal challenge with H5N1 influenza virus. M8-VLP immunization also led to long-term protective responses against influenza virus infection in mice. M8 adjuvantation of VLP increased endpoint and antibody titers and inhibited influenza virus replication in lungs compared with approved or experimental adjuvants alum, AddaVax, and poly(I·C). Uniquely, immunization with M8-VLP stimulated a TH1-biased CD4 T cell response, as determined by increased TH1 cytokine levels in CD4 T cells and increased IgG2 levels in sera. Collectively, these data demonstrate that a sequence-optimized, RIG-I-specific agonist is a potent adjuvant that can be utilized to increase the efficacy of influenza VLP vaccination and dramatically improve humoral and cellular mediated protective responses against influenza virus challenge.

IMPORTANCE

The development of novel adjuvants to increase vaccine immunogenicity is an important goal that seeks to improve vaccine efficacy and ultimately prevent infections that endanger human health. This proof-of-principle study investigated the adjuvant properties of a sequence-optimized 5'pppRNA agonist (M8) with enhanced capacity to stimulate antiviral and inflammatory gene networks using influenza virus-like particles (VLP) expressing HA and NA as immunogens. Vaccination with VLP in combination with M8 increased anti-influenza virus antibody titers and protected animals from lethal influenza virus challenge, highlighting the potential clinical use of M8 as an adjuvant in vaccine development. Altogether, the results describe a novel immunostimulatory agonist targeted to the cytosolic RIG-I sensor as an attractive vaccine adjuvant candidate that can be used to increase vaccine efficacy, a pressing issue in children and the elderly population.

Activation of human T cells by CD1 and self-lipids

Over two decades ago, it was discovered that the human T-cell repertoire contains T cells that do not recognize peptide antigens in the context of MHC molecules but instead respond to lipid antigens presented by CD1 antigen-presenting molecules. The ability of T cells to 'see' lipid antigens bound to CD1 enables these lymphocytes to sense changes in the lipid composition of cells and tissues as a result of infections, inflammation, or malignancies. Although foreign lipid antigens have been shown to function as antigens for CD1-restricted T cells, many CD1-restricted T cells do not require foreign antigens for activation but instead can be activated by self-lipids presented by CD1. This review highlights recent developments in the field, including the identification of common mammalian lipids that function as autoantigens for αβ and γδ T cells, a novel mode of T-cell activation whereby CD1a itself rather than lipids serves as the autoantigen, and various mechanisms by which the activation of CD1-autoreactive T cells is regulated. As CD1 can induce T-cell effector functions in the absence of foreign antigens, multiple mechanisms are in place to regulate this self-reactivity, and stimulatory CD1-lipid complexes appear to be tightly controlled in space and time.

Modulation of influenza vaccine immune responses using an epidermal growth factor receptor kinase inhibitor

Systemic use of epidermal growth factor receptor inhibitors (EGFRIs) has been shown to alter MHC expression and that of several chemokines, and to enhance immune cell recruitment into human skin. We hypothesized that EGFRIs may have value as cutaneous immune response modifiers, and determined the effects of topical application of an irreversible EGFRI on a well-established murine model of influenza vaccination. We found that a single topical application of an EGFRI led to increased levels of antibodies that inhibit influenza mediated hemagglutination and viral cytopathic effects. The topically applied EGFRI significantly enhanced the generation of vaccine-specific IL-4 and IFN-γ producing cells within skin-draining lymph nodes as early as one week following vaccination. The EGFRI/vaccine group showed a twelve-fold reduction in detectable pulmonary viral load four days after infection as compared to the vaccine alone control group. The reduction in the lung viral titers correlated with the survival rate, which demonstrated 100% protection in the EGFRI/vaccine immunized group but only 65% protection in the mice immunized with vaccine alone. These findings are significant because they demonstrate that inhibition of defined signaling pathways within the skin using small molecule kinase inhibitors provides a novel approach to enhance immune responses to vaccines.

Recent advances of vaccine adjuvants for infectious diseases

Vaccines are the most effective and cost-efficient method for preventing diseases caused by infectious pathogens. Despite the great success of vaccines, development of safe and strong vaccines is still required for emerging new pathogens, re-emerging old pathogens, and in order to improve the inadequate protection conferred by existing vaccines. One of the most important strategies for the development of effective new vaccines is the selection and usage of a suitable adjuvant. Immunologic adjuvants are essential for enhancing vaccine potency by improvement of the humoral and/or cell-mediated immune response to vaccine antigens. Thus, formulation of vaccines with appropriate adjuvants is an attractive approach towards eliciting protective and long-lasting immunity in humans. However, only a limited number of adjuvants is licensed for human vaccines due to concerns about safety and toxicity. We summarize current knowledge about the potential benefits of adjuvants, the characteristics of adjuvants and the mechanisms of adjuvants in human vaccines. Adjuvants have diverse modes of action and should be selected for use on the basis of the type of immune response that is desired for a particular vaccine. Better understanding of current adjuvants will help exploring new adjuvant formulations and facilitate rational design of vaccines against infectious diseases.

Safety, Reactogenicity, and Immunogenicity of Inactivated Monovalent Influenza A(H5N1) Virus Vaccine Administered With or Without AS03 Adjuvant

BACKGROUND

The national stockpile for influenza pandemic preparedness includes vaccines against an array of strains and adjuvants that could be utilized to induce immunologic priming as a pandemic wave emerges. We assessed the feasibility of a strategy that allows the flexibility of postmanufacture mixture of vaccine and adjuvant at the point of care.

METHODS

We conducted a randomized, double-blind, multicenter trial among healthy adults aged 18-49 years who received 2 doses of inactivated influenza A/Indonesia/05/2005 (H5N1 clade 2.2.3) virus vaccine containing either 3.75, 7.5, or 15 µg of hemagglutinin (HA) with or without AS03 adjuvant, administered 21 days apart. Subjects were observed for local (injection site) and systemic reactogenicity and adverse events. Sera were tested for hemagglutination inhibition (HAI) and microneutralization (MN) antibody levels against the homologous strain and 4 heterologous avian strains.

RESULTS

Vaccine containing ASO3 adjuvant was associated with significantly more local reactions compared with nonadjuvanted vaccine, but these were short-lived and resolved spontaneously. Although the immune response to nonadjuvanted vaccine was poor, 2 doses of AS03-adjuvanted vaccine containing as little as 3.75 µg of HA elicited robust immune responses resulting in seroprotective titers (≥1:40) to the homologous strain in ≥86% of subjects by HAI and in 95% of subjects by MN. Cross-clade antibody responses were also observed with AS03-adjuvanted vaccine, but not nonadjuvanted vaccine.

CONCLUSIONS

AS03 adjuvant formulated with inactivated vaccine at the administration site significantly enhanced the immune responses to H5N1 vaccine and has the potential to markedly improve vaccine responses and accelerate delivery during an influenza pandemic.

CLINICAL TRIALS REGISTRATION

NCT01317758.

Assessment of mOMV adjuvant efficacy in the pathogenic H1N1 influenza virus vaccine

Purpose

Since the pandemic (H1N1) 2009 virus has been a seasonal flu which still poses great human health concerns worldwide, vaccination would be considered as the most effective strategy to control the influenza virus spreading. Here, we assessed adjuvant efficacy of modified outer membrane vesicle (mOMV) towards the pandemic H1N1 split antigen.

Materials and Methods

For this study, mice were vaccinated twice with various amount of antigen (0.05, 0.1, and 0.5 µg/dose hemagglutinin [HA]) that were mixed with mOMV, aluminum hydroxide (alum), and MF59, as well as the combined adjuvant comprising the mOMV plus alum.

Results

We found that all the adjuvanted vaccines of A/California/04/09 (CA04, H1N1) containing HA antigen more than 0.1 µg/dose protected effectively from lethal challenge (maCA04, H1N1) virus, compared to the antigen only group. Furthermore, vaccinated mice received as low as 0.05 µg/dose of the split vaccine containing the combined adjuvant (10 µg of mOMV plus alum) showed a full protection against lethal challenge with H1N1 virus. Taken together, these results suggest that mOMV can exert not only the self-adjuvanticity but also a synergy effect for the vaccine efficacy when combined with alum.

Conclusion

Our results indicate that mOMV could be a promising vaccine adjuvant by itself and it could be used as a vaccine platform for development of various vaccine formulations to prepare future influenza pandemic.

ELPylated haemagglutinins produced in tobacco plants induce potentially neutralizing antibodies against H5N1 viruses in mice

Reducing the cost of vaccine production is a key priority for veterinary research, and the possibility of heterologously expressing antigen in plants provides a particularly attractive means of achieving this. Here, we report the expression of the avian influenza virus haemagglutinin (AIV HA) in tobacco, both as a monomer and as a trimer in its native and its ELPylated form. We firstly presented evidence to produce stabilized trimers of soluble HA in plants. ELPylation of these trimers does not influence the trimerization. Strong expression enhancement in planta caused by ELPylation was demonstrated for trimerized H5-ELP. ELPylated trimers could be purified by a membrane-based inverse transition cycling procedure with the potential of successful scale-up. The trimeric form of AIV HA was found to enhance the HA-specific immune response compared with the monomeric form. Plant-derived AIV HA trimers elicited potentially neutralizing antibodies interacting with both homologous virus-like particles from plants and heterologous inactivated AIV. ELPylation did not influence the functionality and the antigenicity of the stabilized H5 trimers. These data allow further developments including scale-up of production, purification and virus challenge experiments with the final goal to achieve suitable technologies for efficient avian flu vaccine production.

Broader neutralizing antibodies against H5N1 viruses using prime-boost immunization of hyperglycosylated hemagglutinin DNA and virus-like particles

BACKGROUND

Highly pathogenic avian influenza (HPAI) H5N1 viruses and their transmission capability from birds to humans have raised global concerns about a potential human pandemic. The inherent nature of antigenic changes in influenza viruses has not been sufficiently taken into account in immunogen designs for broadly protective HPAI H5N1 vaccines.

METHODS

We designed a hyperglycosylated HA vaccine using N-linked glycan masking on highly variable sequences in the HA1 globular head. Immunization of these hyperglycosylated HA DNA vaccines followed by a flagellin-containing virus-like particle booster in mice was conducted to evaluate neutralizing antibody responses against various clades of HPAI H5N1 viruses.

RESULTS

We introduced nine N-X-S/T motifs in five HA1 regions: 83NNT, 86NNT, 94NFT, 127NSS, 138NRT, 156NTT, 161NRS, 182NDT, and 252NAT according to sequence alignment analyses from 163 HPAI H5N1 human isolates. Although no significant differences of anti-HA total IgG titers were found with these hyperglycosyalted HA compared to the wild-type control, the 83NNT and 127NSS mutants elicited significantly potent cross-clade neutralizing antibodies against HPAI H5N1 viruses.

CONCLUSIONS

This finding may have value in terms of novel immunogen design for developing cross-protective H5N1 vaccines.

Delta inulin polysaccharide adjuvant enhances the ability of split-virion H5N1 vaccine to protect against lethal challenge in ferrets

BACKGROUND

The reduced immunogenicity of the H5 hemagglutinin (HA), compared to seasonal HA serotypes, has stimulated searches for effective adjuvants to improve H5 vaccine efficacy. This study examined the immunogenicity and protective efficacy in ferrets immunized with a split-virion H5N1 vaccine combined with Advax™, a novel delta inulin-based polysaccharide adjuvant technology that has previously demonstrated ability to augment humoral and cellular immunity to co-administered antigens.

METHODS

Ferrets were vaccinated twice 21 days apart with 7.5 μg or 22.5 μg of a split-virion preparation of A/Vietnam/1203/2004 with or without adjuvant. An additional group received just one immunization with 22.5 μg HA plus adjuvant. Serum antibodies were measured by hemagglutination inhibition and microneutralization assays. Vaccinated animals were challenged intranasally 21 days after the last immunization with 10(6) EID(50) of the homologous strain. Morbidity was assessed by observed behavior, weight loss, temperature, cytopenias, histopathology, and viral load.

RESULTS

No serum neutralization antibody was detected after two immunizations with unadjuvanted vaccine. Two immunizations with high or low dose adjuvanted vaccine stimulated high neutralizing antibody titers. Survival was 100% in all groups receiving adjuvanted-vaccine including the single dose group, compared to 67% survival with unadjuvanted vaccine, and 0% survival in saline or adjuvant-alone controls. Minimal morbidity was seen in all animals receiving adjuvanted vaccine, and was limited to rhinorrhea and mild thrombocytopenia, without fever, weight loss, or reduced activity. H5N1 virus was cleared from the nasal wash by day 4 post-challenge only in animals receiving adjuvanted vaccine which also prevented viral invasion of the brain in most animals.

CONCLUSIONS

In this initial study, Advax™ adjuvant formulations improved the protective efficacy of a split-virion H5N1 vaccine as measured by significantly enhanced immunogenicity, survival, and reduced morbidity.

Influenza vaccine responses in older adults

The most profound consequences of immune senescence with respect to public health are the increased susceptibility to influenza and loss of efficacy of the current split-virus influenza vaccines in older adults, which are otherwise very effective in younger populations. Influenza infection is associated with high rates of complicated illness including pneumonia, heart attacks and strokes in the 65+ population. Changes in both innate and adaptive immune function not only converge in the reduced response to vaccination and protection against influenza, but present significant challenges to new vaccine development. In older adults, the goal of vaccination is more realistically targeted to providing clinical protection against disease rather sterilizing immunity. Correlates of clinical protection may not be measured using standard techniques such as antibody titres to predict vaccine efficacy. Further, antibody responses to vaccination as a correlate of protection may fail to detect important changes in cellular immunity and enhanced vaccine-mediated protection against influenza illness in older people. This article will discuss the impact of influenza in older adults, immunologic targets for improved efficacy of the vaccines, and alternative correlates of clinical protection against influenza that are needed for more effective translation of novel vaccination strategies to improved protection against influenza in older adults.

Improvement of the trivalent inactivated flu vaccine using PapMV nanoparticles

Commercial seasonal flu vaccines induce production of antibodies directed mostly towards hemaglutinin (HA). Because HA changes rapidly in the circulating virus, the protection remains partial. Several conserved viral proteins, e.g., nucleocapsid (NP) and matrix proteins (M1), are present in the vaccine, but are not immunogenic. To improve the protection provided by these vaccines, we used nanoparticles made of the coat protein of a plant virus (papaya mosaic virus; PapMV) as an adjuvant. Immunization of mice and ferrets with the adjuvanted formulation increased the magnitude and breadth of the humoral response to NP and to highly conserved regions of HA. They also triggered a cellular mediated immune response to NP and M1, and long-lasting protection in animals challenged with a heterosubtypic influenza strain (WSN/33). Thus, seasonal flu vaccine adjuvanted with PapMV nanoparticles can induce universal protection to influenza, which is a major advancement when facing a pandemic.

Enhanced immunogenicity, mortality protection, and reduced viral brain invasion by alum adjuvant with an H5N1 split-virion vaccine in the ferret

Background

Pre-pandemic development of an inactivated, split-virion avian influenza vaccine is challenged by the lack of pre-existing immunity and the reduced immunogenicity of some H5 hemagglutinins compared to that of seasonal influenza vaccines. Identification of an acceptable effective adjuvant is needed to improve immunogenicity of a split-virion avian influenza vaccine.

Methods and Findings

Ferrets (N = 118) were vaccinated twice with a split-virion vaccine preparation of A/Vietnam/1203/2004 or saline either 21 days apart (unadjuvanted: 1.9 µg, 7.5 µg, 30 µg, or saline), or 28 days apart (unadjuvanted: 22.5 µg, or alum-adjuvanted: 22.5 or 7.5 µg). Vaccinated animals were challenged intranasally 21 or 28 days later with 10⁶ EID₅₀ of the homologous strain. Immunogenicity was measured by hemagglutination inhibition and neutralization assays. Morbidity was assessed by observed behavior, weight loss, temperature, cytopenias, histopathology, and viral load.

No serum antibodies were detected after vaccination with unadjuvanted vaccine, whereas alum-adjuvanted vaccination induced a robust antibody response. Survival after unadjuvanted dose regimens of 30 µg, 7.5 µg and 1.9 µg (21-day intervals) was 64%, 43%, and 43%, respectively, yet survivors experienced weight loss, fever and thrombocytopenia. Survival after unadjuvanted dose regimen of 22.5 µg (28-day intervals) was 0%, suggesting important differences in intervals in this model. In contrast to unadjuvanted survivors, either dose of alum-adjuvanted vaccine resulted in 93% survival with minimal morbidity and without fever or weight loss. The rarity of brain inflammation in alum-adjuvanted survivors, compared to high levels in unadjuvanted vaccine survivors, suggested that improved protection associated with the alum adjuvant was due to markedly reduced early viral invasion of the ferret brain.

Conclusion

Alum adjuvant significantly improves efficacy of an H5N1 split-virion vaccine in the ferret model as measured by immunogenicity, mortality, morbidity, and brain invasion.

Inflammasome-independent role of the apoptosis-associated speck-like protein containing CARD (ASC) in the adjuvant effect of MF59

Clinical studies have indicated that subvirion inactivated vaccines against avian influenza viruses, particularly H5N1, are poorly immunogenic in humans. As a consequence, the use of adjuvants has been championed for the efficient vaccination of a naïve population against avian influenza. Aluminum salts (alum) and the oil-in-water emulsion MF59 are safe and effective adjuvants that are being used with influenza vaccines, but the mechanism underlying their stimulation of the immune system remains poorly understood. It was shown recently that activation of a cytosolic innate immune-sensing complex known as "NLR-Pyrin domain containing 3" (NLRP3) inflammasome, also known as "cryopyrin," "cold-induced autoinflammatory syndrome 1" (CIAS1), or nacht domain-, leucine-rich repeat-, and PYD-containing protein 3 (Nalp3), is essential for the adjuvant effect of alum. Here we show that the inflammasome component apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), an adapter protein within the NLRP3 inflammasome, is a crucial element in the adjuvant effect of MF59 when combined with H5N1 subunit vaccines. In the absence of ASC, H5-specific IgG antibody responses are significantly reduced, whereas the responses are intact in NLRP3(-/-) and caspase-1(-/-) mice. This defect is caused mainly by the failure of antigen-specific B cells to switch from IgM to IgG production. We conclude that ASC plays an inflammasome-independent role in the induction of antigen-specific humoral immunity after vaccination with MF59-adjuvanted influenza vaccines. These findings have important implications for the rational design of next-generation adjuvants.

Plant viral epitope display systems for vaccine development

The 'easiest' vaccines, base on production of neutralizing antibodies, have been made. With the emergence of chronic diseases, vaccine developers have understood the importance to trigger an efficient cellular mediated immune response (CTL response) to respond to this medical need. Several options are currently in development and the utilization of plant virus as vaccine platform for the trigger of a CTL response is considered as an interesting avenue. The highly ordered structures of plant viruses are good triggers of the innate immune system, which in turn, is used to initiate an immune response to a vaccine target. It is likely that plant viruses will play an important role in the development of the vaccine of the futures even if there is still several challenges to face.

Cationic lipid/DNA complex-adjuvanted influenza A virus vaccination induces robust cross-protective immunity

Influenza A virus is a negative-strand segmented RNA virus in which antigenically distinct viral subtypes are defined by the hemagglutinin (HA) and neuraminidase (NA) major viral surface proteins. An ideal inactivated vaccine for influenza A virus would induce not only highly robust strain-specific humoral and T-cell immune responses but also cross-protective immunity in which an immune response to antigens from a particular viral subtype (e.g., H3N2) would protect against other viral subtypes (e.g., H1N1). Cross-protective immunity would help limit outbreaks from newly emerging antigenically novel strains. Here, we show in mice that the addition of cationic lipid/noncoding DNA complexes (CLDC) as adjuvant to whole inactivated influenza A virus vaccine induces significantly more robust adaptive immune responses both in quantity and quality than aluminum hydroxide (alum), which is currently the most widely used adjuvant in clinical human vaccination. CLDC-adjuvanted vaccine induced higher total influenza virus-specific IgG, particularly for the IgG2a/c subclass. Higher levels of multicytokine-producing influenza virus-specific CD4 and CD8 T cells were induced by CLDC-adjuvanted vaccine than with alum-adjuvanted vaccine. Importantly, CLDC-adjuvanted vaccine provided significant cross-protection from either a sublethal or lethal influenza A viral challenge with a different subtype than that used for vaccination. This superior cross-protection afforded by the CLDC adjuvant required CD8 T-cell recognition of viral peptides presented by classical major histocompatibility complex class I proteins. Together, these results suggest that CLDC has particular promise for vaccine strategies in which T cells play an important role and may offer new opportunities for more effective control of human influenza epidemics and pandemics by inactivated influenza virus vaccine.

Adjuvants for cancer vaccines

The recent FDA approval of sipuleucel-T (Provenge), a patient-specific immunotherapy for androgen-independent prostate cancer developed by Dendreon Corporation, has provided support for the concept of cellular immunotherapy as an approach to cancer treatment. Adjuvants are compounds that enhance the potency of the antigen-specific immune response and can be an essential component of an efficacious vaccine. Cervarix is a prophylactic vaccine against human papilloma virus (HPV) types 16 and 18, which can cause cervical cancer, and recently received approval from the FDA, due in part to the protective immunity it conferred against not only HPV types contained in the vaccine but in addition to oncogenic HPV strains that were not contained in the vaccine. Cervarix is formulated with MPL (monophosphoryl lipid A), a TLR-4 targeted adjuvant shown to promote immune response broadening. The recent FDA approvals of these pioneering vaccines are landmark events, and will likely usher in renewed interest and investment in the development of new therapeutic cancer vaccine candidates. In this review, we examine new molecularly defined adjuvants and formulations and its application to cancer vaccines under development.

Influenza vaccines: the good, the bad, and the eggs

Outbreaks of influenza A viruses continue to cause morbidity and mortality worldwide. The global disease burden of influenza is substantial. While antiviral therapies are available, influenza vaccines are the mainstay of efforts to reduce the substantial health burden from seasonal influenza. Inactivated influenza vaccines have been available since the 1940s, with live attenuated, cold-adapted vaccines becoming available in the United States in 2003. In spite of the successes, more research is needed to develop more effective seasonal influenza vaccines that provide long-lasting immunity and broad protection against strains that differ antigenically from vaccine viruses. This review introduces the virus and its disease, the current state of seasonal and pandemic influenza vaccines, and the challenges we face in the future.