Nasal immunization with subunit proteosome influenza vaccines induces serum HAI, mucosal IgA and protection against influenza challenge

Advances in intranasal vaccine delivery: A promising non-invasive route of immunization

The importance of vaccination has been proven particularly significant the last three years, as it is revealed to be the most efficient weapon for the prevention of several infections including SARS-COV-2. Parenteral vaccination is the most applicable method of immunization, for the prevention of systematic and respiratory infections, or central nervous system disorders, involving T and B cells to a whole-body immune response. However, the mucosal vaccines, such as nasal vaccines, can additionally activate the immune cells localized on the mucosal tissue of the upper and lower respiratory tract. This dual stimulation of the immune system, along with their needle-free administration favors the development of novel nasal vaccines to produce long-lasting immunity. In recent years, the nanoparticulate systems have been extensively involved in the formulation of nasal vaccines as polymeric, polysaccharide and lipid ones, as well as in the form of proteosomes, lipopeptides and virosomes. Advanced delivery nanosystems have been designed and evaluated as carriers or adjuvants for nasal vaccination. To this end, several nanoparticulate vaccines are undergone clinical trials as promising candidates for nasal immunization, while nasal vaccines against influenza type A and B and hepatitis B have been approved by health authorities. This comprehensive literature review aims to summarize the critical aspects of these formulations and highlight their potential for the future establishment of nasal vaccination. Both preclinical (in vitro and in vivo) and clinical studies are incorporated, summarized, and critically discussed, as well as the limitations of nasal immunization.

Supplementation of Alhagi honey polysaccharides contributes to the improvement of the intestinal immunity regulating the structure of intestinal flora in mice

Alhagi honey polysaccharides (AH), a main active component of Alhagi honey, are known to possess excellent pharmacological activities and have been widely used as dietary supplements in traditional Chinese medicine for thousands of years. This study is aimed to investigate the heath effect of AH on murine intestinal mucosal immune function and composition of the gut microbiome. ICR mice received daily intragastric administration of AH (three dosages, 200 mg kg^-1, 400 mg kg^-1, and 800 mg kg^-1) or saline for 7 consecutive days. Results indicated an improvement in the intestinal barrier function through increases in secretory immunoglobulin A (sIgA) and β-defensins. Simultaneously, AH also significantly stimulated IL-2, IL-4, IL-6, IL-10, IL-17, IFN-γ, and TNF-α cytokine secretion as compared to the control samples. Moreover, hematoxylin and eosin staining showed that AH enhanced the number of intraepithelial lymphocytes (IELs) in the small intestine. An obvious increase in the ratio of IgA⁺ cells of AH-treatment samples in the lamina propria was also detected by immunohistochemical staining. In addition, the CD3⁺, CD4⁺ and CD8⁺ T-cell ratio in mesenteric lymph nodes and Peyer's patches in the AH-treatment was significantly higher than that in the control group. Furthermore, 16S rDNA gene sequencing was used to monitor the dynamic changes in the gut microbiota. The result revealed that AH significantly increased the indexes of Shannon and obviously decreased the indexes of Simpson, suggesting the enhancement of the diversity and richness of the intestinal microbiome. Moreover, AH modulated the gut microbiome via increasing the abundance of probiotics and decreasing the levels of pathogenic bacteria. In summary, these results indicated that AH could be used as a prebiotic to enhance murine intestinal mucosal immunity and to modulate the gut microbiome.

Potential adjuvants for the development of a SARS-CoV-2 vaccine based on experimental results from similar coronaviruses

The extensive efforts around the globe are being made to develop a suitable vaccine against COVID-19 (Coronavirus Disease-19) caused by SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus-2). An effective vaccine should be able to induce high titers of neutralizing antibodies to prevent the virus from attaching to the host cell receptors. However, to elicit the protective levels of antibodies, a vaccine may require multiple doses or assistance from other immunostimulatory molecules. Further, the vaccine should be able to induce protective levels of antibodies rapidly with the least amount of antigen used. This decreases the cost of a vaccine and makes it affordable. As the pandemic has hit most countries across the globe, there will be an overwhelming demand for the vaccine in a quick time. Incorporating a suitable adjuvant in a SARS-CoV-2 vaccine may address these requirements. This review paper will discuss the experimental results of the adjuvanted vaccine studies with similar coronaviruses (CoVs) which might be useful to select an appropriate adjuvant for a vaccine against rapidly emergingSARS-CoV-2. We also discuss the current progress in the development of adjuvanted vaccines against the disease.

Innovative Mucosal Vaccine Formulations Against Influenza A Virus Infections

Despite efforts made to develop efficient preventive strategies, infections with influenza A viruses (IAV) continue to cause serious clinical and economic problems. Current licensed human vaccines are mainly inactivated whole virus particles or split-virion administered via the parenteral route. These vaccines provide incomplete protection against IAV in high-risk groups and are poorly/not effective against the constant antigenic drift/shift occurring in circulating strains. Advances in mucosal vaccinology and in the understanding of the protective anti-influenza immune mechanisms suggest that intranasal immunization is a promising strategy to fight against IAV. To date, human mucosal anti-influenza vaccines consist of live attenuated strains administered intranasally, which elicit higher local humoral and cellular immune responses than conventional parenteral vaccines. However, because of inconsistent protective efficacy and safety concerns regarding the use of live viral strains, new vaccine candidates are urgently needed. To prime and induce potent and long-lived protective immune responses, mucosal vaccine formulations need to ensure the immunoavailability and the immunostimulating capacity of the vaccine antigen(s) at the mucosal surfaces, while being minimally reactogenic/toxic. The purpose of this review is to compile innovative delivery/adjuvant systems tested for intranasal administration of inactivated influenza vaccines, including micro/nanosized particulate carriers such as lipid-based particles, virus-like particles and polymers associated or not with immunopotentiatory molecules including microorganism-derived toxins, Toll-like receptor ligands and cytokines. The capacity of these vaccines to trigger specific mucosal and systemic humoral and cellular responses against IAV and their (cross)-protective potential are considered.

An Adenovirus-Vectored Influenza Vaccine Induces Durable Cross-Protective Hemagglutinin Stalk Antibody Responses in Mice

Currently licensed vaccines against the influenza A virus (IAV) need to be updated annually to match the constantly evolving antigenicity of the influenza virus glycoproteins, hemagglutinin (HA), and neuramidiase (NA). Attempts to develop universal vaccines that provide broad protection have resulted in some success. Herein, we have shown that a replication-deficient adenovirus expressing H5/M2e induced significant humoral immunity against the conserved HA stalk. Compared to the humoral responses induced by an inactivated influenza vaccine, the humoral responses induced by the adenovirus-vectored vaccine against the conserved stalk domain mediated cross-protection against heterosubtypic influenza viruses. Importantly, virus inactivation by formaldehyde significantly reduced the binding of monoclonal antibodies (mAbs) to the conserved nucleoprotein (NP), M2e, and HA stalk. These results suggest that inactivation by formaldehyde significantly alters the antigenicity of the HA stalk, and suggest that the conformation of the intact HA stalk provided by vector-based vaccines is important for induction of HA stalk-binding Abs. Our study provides insight into the mechanism by which a vector-based vaccine induces broad protection by stimulation of cross-protective Abs targeting conserved domains of viral proteins. The findings support further strategies to develop a vectored vaccine as a universal influenza vaccine for the control of influenza epidemics and unpredicted pandemics.

Nasal nanovaccines

Nasal administration of vaccines is convenient for the potential stimulation of mucosal and systemic immune protection. Moreover the easy accessibility of the intranasal route renders it optimal for pandemic vaccination. Nanoparticles have been identified as ideal delivery systems and adjuvants for vaccine application. Heterogeneous protocols have been used for animal studies. This complicates the understanding of the formulation influence on the immune response and the comparison of the different nanoparticles approaches developed. Moreover anatomical and immunological differences between rodents and humans provide an additional hurdle in the rational development of nasal nanovaccines. This review will give a comprehensive expertise of the state of the art in nasal nanovaccines in animals and humans focusing on the nanomaterial used.

An Intranasal Proteosome-Adjuvanted Trivalent Influenza Vaccine Is Safe, Immunogenic & Efficacious in the Human Viral Influenza Challenge Model. Serum IgG & Mucosal IgA Are Important Correlates of Protection against Illness Associated with Infection

INTRODUCTION

A Proteosome-adjuvanted trivalent inactivated influenza vaccine (P-TIV) administered intra-nasally was shown to be safe, well tolerated and immunogenic in both systemic and mucosal compartments, and effective at preventing illness associated with evidence of influenza infection.

METHODS

In two separate studies using the human viral challenge model, subjects were selected to be immunologically naive to A/Panama/2007/1999 (H3N2) virus and then dosed via nasal spray with one of three regimens of P-TIV or placebo. One or two doses, 15 μg or 30 μg, were given either once only or twice 14 days apart (1 x 30 μg, 2 x 30 μg, 2 x 15 μg) and subjects were challenged with A/Panama/2007/1999 (H3N2) virus. Immune responses to the vaccine antigens were measured by haemagglutination inhibition assay (HAI) and nasal wash secretory IgA (sIgA) antibodies.

RESULTS

Vaccine reactogenicity was mild, predictable and generally consistent with earlier Phase I studies with this vaccine. Seroconversion to A/Panama/2007/1999 (H3N2), following vaccination but prior to challenge, occurred in 57% to 77% of subjects in active dosing groups and 2% of placebo subjects. The greatest relative rise in sIgA, following vaccination but prior to challenge, was observed in groups that received 2 doses.

CONCLUSION

Intranasal vaccination significantly protected against influenza (as defined by influenza symptoms combined with A/Panama seroconversion) following challenge with A/Panama/2007/1999 (H3N2). When data were pooled from both studies, efficacy ranged from 58% to 82% in active dosing groups for any influenza symptoms with seroconversion, 67% to 85% for systemic or lower respiratory illness and seroconversion, and 65% to 100% for febrile illness and seroconversion. The two dose regimen was found to be superior to the single dose regimen. In this study, protection against illness associated with evidence of influenza infection (evidence determined by seroconversion) following challenge with virus, significantly correlated with pre-challenge HAI titres (p = 0.0003) and mucosal sIgA (p≤0.0001) individually, and HAI (p = 0.028) and sIgA (p = 0.0014) together. HAI and sIgA levels were inversely related to rates of illness.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02522754.

A vaccine consisting of Schistosoma mansoni cathepsin B formulated in Montanide ISA 720 VG induces high level protection against murine schistosomiasis

Background

Schistosomiasis is the most important human helminth infection due to its impact on public health. The clinical manifestations are chronic and significantly decrease an individual’s quality of life. Infected individuals suffer from long-term organ pathologies including fibrosis which eventually leads to organ failure. The development of a vaccine against this parasitic disease would contribute to a long-lasting decrease in disease spectrum and transmission.

Method

Our group has chosen Schistosoma mansoni (Sm) cathepsin B, a peptidase involved in parasite feeding, as a prospective vaccine candidate. Our experimental formulation consisted of recombinant Sm-cathepsin B formulated in Montanide ISA 720 VG, a squalene based adjuvant containing a mannide mono-oleate emulsifier. Parasitological burden was assessed by determining adult worm, hepatic egg, and intestinal egg numbers in each mouse. Serum was used in ELISAs to evaluate production of antigen-specific antibodies, and isolated splenocytes were stimulated with the antigen for the analysis of cytokine secretion levels.

Results

The Sm-cathepsin B and Montanide formulation conferred protection against a challenge infection by significantly reducing all forms of parasitological burdens. Worm burden, hepatic egg burden and intestinal egg burden were decreased by 60 %, 62 %, and 56 %, respectively in immunized animals compared to controls (P = 0.0002, P < 0.0001, P = 0.0009, respectively). Immunizations with the vaccine elicited robust production of Sm-cathepsin B specific antibodies (endpoint titers = 122,880). Both antigen-specific IgG1 and IgG2c titers were observed, with the former having more elevated titers. Furthermore, splenocytes isolated from the immunized animals, compared to control animals, secreted higher levels of key Th1 cytokines, IFN-γ, IL-12, and TNF-α, as well as the Th2 cytokines IL-5 and IL-4 when stimulated with recombinant Sm-cathepsin B. The Th17 cytokine IL-17, the chemokine CCL5, and the growth factor GM-CSF were also significantly increased in the immunized animals compared to the controls.

Conclusion

The formulation tested in this study was able to significantly reduce all forms of parasite burden, stimulate robust production of antigen-specific antibodies, and induce a mixed Th1/Th2 response. These results highlight the potential of Sm-cathepsin B/Montanide ISA 720 VG as a vaccine candidate against schistosomiasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1444-z) contains supplementary material, which is available to authorized users.

Bacillus amyloliquefaciens SQR9 induces dendritic cell maturation and enhances the immune response against inactivated avian influenza virus

The objective of this study was to evaluate the stimulatory effects of Bacillus amyloliquefaciens SQR9 on dendritic cells (DCs) and to verify its ability to enhance the immune response by modulating DC maturation. The results demonstrated that B. amyloliquefaciens SQR9 can adhere to the nasal epithelium and be taken up by DCs in the nasal mucosa, thereby inducing DC maturation and resulting in increased CD80, CD86, CD40 and MHCII expression and cytokine secretion. The frequencies of CD4(+) and CD8(+) T cells and CD69(+) memory T cells were increased in spleens after nasal immunization with virus plus B. amyloliquefaciens SQR9 compared to immunization with inactivated H9N2 AIV alone. Moreover, the levels of sIgA in the nasal cavity, the trachea, and the lung and the levels of IgG, IgG1, and IgG2a in serum were significantly increased in mice administered WIV plus SQR9 compared to mice administered H9N2 WIV alone. The results of this study demonstrated that B. amyloliquefaciens SQR9 can stimulate DC maturation to effectively induce an immune response. In conclusion, an effective immune response may result from the uptake of H9N2 by DCs in the nasal mucosa, thereby stimulating DC maturation and migration to cervical lymph nodes to initiate immune response.

Evaluation of the immune response and protective efficacy of Schistosoma mansoni Cathepsin B in mice using CpG dinucleotides as adjuvant

Schistosomiasis is the most important human helminth infection due to its impact on public health. Worldwide, schistosomiasis is estimated to infect at least 200 million individuals while 700 million are at risk. The clinical manifestations are chronic and significantly decrease an individual's quality of life. Infected individuals suffer from long-term organ pathologies including fibrosis which eventually leads to organ failure. The development of a vaccine against this parasitic disease would contribute to a long-lasting decrease in disease spectrum and transmission. Our group has chosen to target Schistosoma mansoni Cathepsin B as a prospective vaccine candidate. The recombinant protein was tested in the presence of synthetic oligodeoxynucleotides containing unmethylated CpG dinucleotides, which are Toll-like receptor 9 agonists known to stimulate a Th1 response. This formulation conferred a 59% decrease in worm burden as well as a reduction in egg burden. Hepatic egg burden and intestinal egg burden were decreased by 56% and 54% respectively. Immunizations with the formulation elicited robust production of Sm-Cathepsin B specific antibodies, both IgG1 and IgG2c but with the latter predominating. Furthermore, splenocytes isolated from the immunized animals, compared to control animals, had increased secretion levels of key Th1 cytokines, IFN-γ and TNF-α, as well as the chemokine CCL5 when stimulated with recombinant Sm-Cathepsin B. These results highlight the potential of Sm-Cathepsin B/CpG as a vaccine candidate against schistosomiasis.

The threat and prospects for control of an influenza pandemic

Influenza constitutes the most widespread and significant respiratory infectious disease in the world, resulting in increased morbidity, mortality and economic loss each epidemic year. Pandemic influenza is a worldwide epidemic usually caused by a new virus variant to which the majority of the population has no immunity. As demonstrated in the devastating pandemic of 1918 to 1919, a pandemic virus may infect 30 to 50% of the worlds population and kill 1 to 2% of those infected. Pandemic control must be a concerted and co-ordinated world strategy and under the auspices of the World Health Organization, pandemic preparedness plans have been formulated, including: intensified surveillance for more rapid identification of new reassortant viruses with potential human virulence and infectivity, laboratory characterization of the new viruses so that vaccine may be prepared, development of techniques for more rapid vaccine production and the manufacture and stock piling of antiviral drugs. The H5N1 outbreak of virulent chicken influenza in 1997 in Hong Kong which resulted in the deaths of six of 18 infected persons serves as a wake-up call. Should such a virus attain high transmissibility in humans, a pandemic of tragic proportions might ensue. Even though the timing of onset of the next pandemic cannot be precisely predicted, world governments must understand the urgency of the problem and increase funding for influenza pandemic control.

Effects of epimedium polysaccharide-propolis flavone oral liquid on mucosal immunity in chickens

A previous study found that epimedium polysaccharide (EP)-propolis flavonoid (PF) injection (EPI) produced reliable immunoenhancement. In this study, we investigate the effects of EP-PF oral liquid (EFO) on mucosal immunity in the chicken small intestine while using EPI, EP and PF as controls. Groups of fourteen-day-old chickens were given EFO orally at one of the three doses when they were vaccinated with ND vaccine. On days 7, 21 and 35 after the first vaccination, six chickens were selected randomly from each group for measurements of the sIgA and IL-17 contents of the washing liquors of the duodenum and jejunum, counts of the lymphocytes in the duodenal endothelium and counts of the IgA(+) cells in the jejunal endothelium and cecum tonsil. The results indicated that EFO significantly promoted the secretion of sIgA and IL-17 and increased the numbers of lymphocyte and IgA(+) cells. Furthermore, EFO was more efficient than EPI at the high and medium doses. These findings indicate that EPO may enhance intestinal mucosal immunity and may be exploited as an oral immunopotentiator.

Carbon nanotubes as vaccine scaffolds

Carbon nanotubes display characteristics that are potentially useful in their development as scaffolds for vaccine compositions. These features include stability in vivo, lack of intrinsic immunogenicity, low toxicity, and the ability to be appended with multiple copies of antigens. In addition, the particulate nature of carbon nanotubes and their unusual properties of rapid entry into antigen-presenting cells, such as dendritic cells, make them especially useful as carriers of antigens. Early attempts demonstrating carbon nanotube-based vaccines can be used in both infectious disease settings and cancer are promising.

Comparison of 3 kinds of Toll-like receptor ligands for inactivated avian H5N1 influenza virus intranasal immunization in chicken

To evaluate the effects of co-administration of inactivated avian influenza H5N1 virus (IAIV) and different Toll-like receptor (TLR) ligands in chickens, 10-d-old chickens were immunized intranasally with IAIV and TLR ligand [Bacillus subtilis spores, polyinosinic-polycytidylic acid, and CpG oligodeoxynucleotides (CpG-ODN), respectively]. The results showed that both anti-avian influenza virus (AIV) specific secretory IgA level in respiratory tract and anti-AIV specific IgG level in serum significantly increased, as well as the expressions of IL-12, interferon-γ, IL-6, and TLR in the nasal cavity and trachea after intranasal immunization with IAIV and TLR ligand. Among the used TLR ligands, B. subtilis spores as the adjuvant for nasal IAIV had the strongest effect on the expression of IL-6 and IL-12 (P < 0.01), whereas the CpG-ODN could present an advantageous effect on the induction of anti-AIV specific IgG and neutralization antibodies (P < 0.01). The chickens that were previously co-administrated with IAIV and B. subtilis spores could survive at an improved rate upon challenge by live AIV H5N1 virus. Our study suggested that B. subtilis spores, polyinosinic-polycytidylic acid, or CpG-ODN all could effectively enhance the local and systemic immune responses to IAIV in chickens. Considering of the effects and cost of these TLR ligands, we prospected that B. subtilis spores might serve as a more affordable and efficacious mucosal adjuvant for nasal IAIV in chickens.

Microneedle and mucosal delivery of influenza vaccines

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

ICOS-expressing CD4 T cells induced via TLR4 in the nasal mucosa are capable of inhibiting experimental allergic asthma

Modulation of adaptive immune responses via the innate immune pattern recognition receptors, such as the TLRs, is an emerging strategy for vaccine development. We investigated whether nasal rather than intrapulmonary application of Protollin, a mucosal adjuvant composed of TLR2 and TLR4 ligands, is sufficient to elicit protection against murine allergic lower airway disease. Wild-type, Tlr2(-/-), or Tlr4(-/-) BALB/c mice were sensitized to a birch pollen allergen extract (BPEx), then received either intranasal or intrapulmonary administrations of Protollin or Protollin admixed with BPEx, followed by consecutive daily BPEx challenges. Nasal application of Protollin or Protollin admixed with BPEx was sufficient to inhibit allergic lower airway disease with minimal collateral lung inflammation. Inhibition was dependent on TLR4 and was associated with the induction of ICOS in cells of the nasal mucosa and on both CD4+Foxp3+ and CD4+Foxp3- T cells of the draining lymph nodes (LNs), as well as their recruitment to the lungs. Adoptive transfer of cervical LN CD4+ICOS+, but not CD4+ICOS-, cells inhibited BPEx-induced airway hyperresponsiveness and bronchoalveolar lavage eosinophilia. Thus, our data indicate that expansion of resident ICOS-expressing CD4+ T cells of the cervical LNs by nasal mucosal TLR4 stimulation may inhibit the development of allergic lower airway disease in mice.

Immune responses in Atlantic salmon (Salmo salar) following protective vaccination against infectious salmon anemia (ISA) and subsequent ISA virus infection

Infectious salmon anemia (ISA) is an orthomyxoviral disease that has had devastating effects on farmed Atlantic salmon. ISA is still a disease resulting in continued loss of revenues and therefore development of effective vaccines is of great importance. Commercial vaccines against ISA are available, but the efficacy is poorly described. There is little information about vaccine-induced immune factors preventing ISA virus (ISAV) infection today. In this study we assessed the protective effects and immunogenicity of vaccines containing three different quantities of the inactivated ISAV antigen. Our findings indicated that immunization induced effective protection in Atlantic salmon with a relative percent survival (RPS) as high as 86. The level of protection was correlated to the amount of ISAV antigen in the vaccine, and fish immunized with high antigen amounts produced detectable ISAV-specific and neutralizing antibodies. While ISAV infection was detectable in non-vaccinated control fish challenged by cohabitation, no infection was detected in fish immunized with high antigen amounts. After challenge, transcriptional analysis of selected immune-related genes demonstrated activation of innate immune responses in ISAV-infected control fish, but not in vaccine protected fish. This study furthers the knowledge about vaccine efficacy and vaccine-induced immunity to ISAV challenge in Atlantic salmon.

Human influenza vaccines and assessment of immunogenicity

Influenza is responsible for the infection of approximately 20% of the population every season and for an annual death toll of approximately half a million people. The most effective means for controlling infection and thereby reducing morbidity and mortality is vaccination by injection with an inactivated vaccine, or by intranasal administration of a live-attenuated vaccine. Protection is not always optimal and there is a need for the development of new vaccines with improved efficacy and for the expansion of enrollment into vaccination programs. An overview of old and new vaccines is presented. Methods of monitoring immune responses such as hemagglutination-inhibition, ELISA and neutralization tests are evaluated for their accuracy in the assessment of current and new-generation vaccines.

Needle-free influenza vaccination

Vaccination is the cornerstone of influenza control in epidemic and pandemic situations. Influenza vaccines are typically given by intramuscular injection. However, needle-free vaccinations could offer several distinct advantages over intramuscular injections: they are pain-free, easier to distribute, and easier to give to patients, and their use could reduce vaccination costs. Moreover, vaccine delivery via the respiratory tract, alimentary tract, or skin might elicit mucosal immune responses at the site of virus entry and better cellular immunity, thus improving effectiveness. Although various needle-free vaccination methods for influenza have shown preclinical promise, few have progressed to clinical trials-only live attenuated intranasal vaccines have received approval, and only in some countries. Further clinical investigation is needed to help realise the potential of needle-free vaccination for influenza.

Nanodisc-incorporated hemagglutinin provides protective immunity against influenza virus infection

Every year, influenza virus infection causes significant mortality and morbidity in human populations. Although egg-based inactivated viral vaccines are available, their effectiveness depends on the correct prediction of the circulating viral strains and is limited by the time constraint of the manufacturing process. Recombinant subunit vaccines are easier to manufacture with a relatively short lead time but are limited in their efficacy partly because the purified recombinant membrane proteins in the soluble form most likely do not retain their native membrane-bound structure. Nanodisc (ND) particles are soluble, stable, and reproducibly prepared discoid shaped nanoscale structures that contain a discrete lipid bilayer bound by two amphipathic scaffold proteins. Because ND particles permit the functional reconstitution of membrane/envelope proteins, we incorporated recombinant hemagglutinin (HA) from influenza virus strain A/New Caledonia/20/99 (H1N1) into NDs and investigated their potential to elicit an immune response to HA and confer immunity to influenza virus challenge relative to the commercial vaccines Fluzone and FluMist. HA-ND vaccination induced a robust anti-HA antibody response consisting of predominantly the immunoglobulin G1 (IgG1) subclass and a high hemagglutination inhibition titer. Intranasal immunization with HA-ND induced an anti-HA IgA response in nasal passages. HA-ND vaccination conferred protection that was comparable to that of Fluzone and FluMist against challenge with influenza virus strain A/Puerto Rico/8/1934 (H1N1).

Intranasal delivery of influenza subunit vaccine formulated with GEM particles as an adjuvant

Nasal administration of influenza vaccine has the potential to facilitate influenza control and prevention. However, when administered intranasally (i.n.), commercially available inactivated vaccines only generate systemic and mucosal immune responses if strong adjuvants are used, which are often associated with safety problems. We describe the successful use of a safe adjuvant Gram-positive enhancer matrix (GEM) particles derived from the food-grade bacterium Lactococcus lactis for i.n. vaccination with subunit influenza vaccine in mice. It is shown that simple admixing of the vaccine with the GEM particles results in a strongly enhanced immune response. Already after one booster, the i.n. delivered GEM subunit vaccine resulted in hemagglutination inhibition titers in serum at a level equal to the conventional intramuscular (i.m.) route. Moreover, i.n. immunization with GEM subunit vaccine elicited superior mucosal and Th1 skewed immune responses compared to those induced by i.m. and i.n. administered subunit vaccine alone. In conclusion, GEM particles act as a potent adjuvant for i.n. influenza immunization.

Prolonged protection against Intranasal challenge with influenza virus following systemic immunization or combinations of mucosal and systemic immunizations with a heat-labile toxin mutant

Seasonal influenza virus infections cause considerable morbidity and mortality in the world, and there is a serious threat of a pandemic influenza with the potential to cause millions of deaths. Therefore, practical influenza vaccines and vaccination strategies that can confer protection against intranasal infection with influenza viruses are needed. In this study, we demonstrate that using LTK63, a nontoxic mutant of the heat-labile toxin from Escherichia coli, as an adjuvant for both mucosal and systemic immunizations, systemic (intramuscular) immunization or combinations of mucosal (intranasal) and intramuscular immunizations protected mice against intranasal challenge with a lethal dose of live influenza virus at 3.5 months after the second immunization.

Nanotechnology in vaccine delivery

With very few adjuvants currently being used in marketed human vaccines, a critical need exists for novel immunopotentiators and delivery vehicles capable of eliciting humoral, cellular and mucosal immunity. Such crucial vaccine components could facilitate the development of novel vaccines for viral and parasitic infections, such as hepatitis, HIV, malaria, cancer, etc. In this review, we discuss clinical trial results for various vaccine adjuvants and delivery vehicles being developed that are approximately nanoscale (< 1000 nm) in size. Humoral immune responses have been observed for most adjuvants and delivery platforms while only viral vectors, ISCOMs and Montanide™ ISA 51 and 720 have shown cytotoxic T cell responses in the clinic. MF59 and MPL® have elicited Th1 responses, and virus-like particles, non-degradable nanoparticles and liposomes have also generated cellular immunity. Such vaccine components have also been evaluated for alternative routes of administration with clinical successes reported for intranasal delivery of viral vectors and proteosomes and oral delivery of a VLP vaccine.

Development and preclinical evaluation of an alphavirus replicon vaccine for influenza

We used a propagation-defective, single-cycle, alphavirus replicon vector system to produce virus-like replicon particles (VRP) expressing the hemagglutinin (HA) and neuraminidase (NA) proteins from influenza A/Wyoming/03/2003 (H3N2). Efficient production methods were scaled to produce pilot lots of HA VRP and NA VRP and clinical lots of HA VRP. HA VRP-induced high-titered antibody responses in mice, rabbits and rhesus macaques, as measured by ELISA or hemagglutination inhibition (HI) assays, and robust cellular immune responses in mice and rhesus macaques, as measured by IFN-gamma ELISPOT. NA VRP also induced cellular immune responses in mice. A toxicology study with HA VRP and NA VRP in rabbits showed no adverse effects in any parameter. These studies support clinical testing of alphavirus replicon vaccines for influenza.

Induction of secretory immunity and memory at mucosal surfaces

Mucosal epithelia comprise an extensive vulnerable barrier which is reinforced by numerous innate defence mechanisms cooperating intimately with adaptive immunity. Local generation of secretory IgA (SIgA) constitutes the largest humoral immune system of the body. Secretory antibodies function both by performing antigen exclusion at mucosal surfaces and by virus and endotoxin neutralization within epithelial cells without causing tissue damage. SIgA is thus persistently containing commensal bacteria outside the epithelial barrier but can also target invasion of pathogens and penetration of harmful antigens. Resistance to toxin-producing bacteria such as Vibrio cholerae and enterotoxigenic Escherichia coli appears to depend largely on SIgA, and so does herd protection against horizontal faecal-oral spread of enteric pathogens under naïve or immunized conditions--with a substantial innate impact both on cross-reactivity and memory. Like natural infections, live mucosal vaccines or adequate combinations of non-replicating vaccines and mucosal adjuvants, give rise not only to SIgA antibodies but also to longstanding serum IgG and IgA responses. However, there is considerably disparity with regard to migration of memory/effector cells from mucosal inductive sites to secretory effector sites and systemic immune organs. Also, although immunological memory is generated after mucosal priming, this may be masked by a self-limiting response protecting the inductive lymphoid tissue in the gut. The intranasal route of vaccine application targeting nasopharynx-associated lymphoid tissue may be more advantageous for certain infections, but only if successful stimulation is achieved without the use of toxic adjuvants that might reach the central nervous system. The degree of protection obtained after mucosal vaccination ranges from reduction of symptoms to complete inhibition of re-infection. In this scenario, it is often difficult to determine the relative importance of SIgA versus serum antibodies, but infection models in knockout mice strongly support the notion that SIgA exerts a decisive role in protection and cross-protection against a variety of infectious agents. Nevertheless, relatively few mucosal vaccines have been approved for human use, and more basic work is needed in vaccine and adjuvant design, including particulate or live-vectored combinations.

TLR2 activation by proteosomes promotes uptake of particulate vaccines at mucosal surfaces

Proteosome-based vaccines have TLR2-based adjuvant activity and show promise for mucosal immunization. We examined the effects of proteosomes on mucosal uptake in Peyer's patches in vivo. Proteosomes accelerated transepithelial transport of microparticles by M cells and induced migration of dendritic cells (DCs) into the follicle-associated epithelium (FAE); both effects were dependent on TLR2. Proteosomes induced the release of the DC-attracting chemokine MIP3alpha from Caco-2 epithelial cells in vitro. In HEK cells, proteosome-mediated MIP3alpha release was dependent on TLR2 expression and matrix metalloproteinase activation. Thus, TLR2 activation by proteosomes may promote mucosal uptake of particulate vaccines, and this may contribute to their adjuvanticity.

Intranasal Protollin-formulated recombinant SARS S-protein elicits respiratory and serum neutralizing antibodies and protection in mice

The feasibility of developing a prophylactic vaccine against SARS was assessed by comparing the immune responses elicited by immunizing mice with a recombinant SARS spike glycoprotein (S-protein) formulated with different adjuvants, given by different routes. In both young and aged mice, an intranasal Protollin-formulated S-protein vaccine elicited high levels of antigen-specific IgG in serum, comparable to those elicited by an intramuscular Alum-adsorbed S-protein vaccine. Serum antibodies were shown to be virus neutralizing. Intranasal immunization of young mice with the Protollin-formulated vaccine elicited significant levels of antigen-specific lung IgA in contrast to mice immunized with the intramuscular vaccine in which no antigen-specific lung IgA was detected. Following live virus challenge of aged mice, no virus was detected in the lungs of intranasally immunized mice, in contrast to intramuscularly immunized mice whose lung virus titers were comparable to those observed in control mice.

Intranasal proteosome-based respiratory syncytial virus (RSV) vaccines protect BALB/c mice against challenge without eosinophilia or enhanced pathology

A safe and effective vaccine against respiratory syncytial virus (RSV) is still unavailable. Proteosome-based adjuvants are derived from the outer membrane proteins (OMP) of Neisseria species and are potent inducers of both mucosal and systemic immunity in humans and animals. Candidate RSV subunit vaccines comprising enriched RSV proteins (eRSV) formulated with proteosomes alone or with LPS (Protollin) were produced. Administered intranasally in BALB/c mice, both vaccines elicited long-lasting systemic and mucosal RSV-specific antibodies and fully protected against challenge. In vitro restimulation of lymphocytes from the Protollin-eRSV immunized mice with F (MHC-I) and G (MHC-II) peptides elicited F peptide-specific CD8(+) T cells and supernatant IFNgamma, TNFalpha, IL-2 and IL-10 while the formalin-inactivated RSV (FI-RSV) vaccine elicited predominantly IL-5. Pulmonary eosinophilia did not develop following immunization with either proteosome-based vaccine following challenge compared to mice immunized with FI-RSV. Proteosome-based eRSV vaccines can therefore protect against RSV challenge in mice without increasing the risk of pulmonary immunopathologic responses.

C57Bl/6 mice are protected from respiratory syncytial virus (RSV) challenge and IL-5 associated pulmonary eosinophilic infiltrates following intranasal immunization with Protollin-eRSV vaccine

The protective efficacy of an intranasal (IN) Protollin-eRSV vaccine has recently been demonstrated in the RSV-susceptible BALB/c mouse model. Here, we report the safety, immunogenicity and efficacy of Protollin-eRSV vaccine in the relatively resistant C57Bl/6 mouse model. C57Bl/6 mice immunized IN with either two or three doses of Protollin-eRSV produced significant systemic and mucosal RSV-specific antibodies. Mice immunized with the Protollin vaccine displayed polarized Th1 responses with augmented IFNgamma/IL-5 ratios in RSV-restimulated lung and spleen cell preparations compared with animals that received antigen alone. The Protollin-eRSV immunized C57Bl/6 mice were fully protected against challenge without eosinophilic pulmonary pathology observed in the animals immunized with the formalin-inactivated RSV vaccine. This new model will permit us to dissect the respective roles of the TLR2 and TLR4 ligands contained in the vaccine using TLR knock-out animals established on the C57Bl/6 background.

A vaccination strategy to enhance mucosal and systemic antibody and T cell responses against influenza

Influenza infections are a major cause of mortality and morbidity worldwide. Therefore, there is a need to establish vaccines and immunization protocols that can prevent influenza infections. Herein, we show that one intranasal (IN) followed by one intramuscular (IM) immunizations with a combination of cell culture produced hemagglutinin (HA) antigens derived from 3 different influenza strains induced significantly higher serum hemagglutination inhibition (HI) and serum IgG antibody titers as well as T cell responses, compared to 2 IM, 2 IN or 1 M followed by 1 IN immunizations. Moreover, while 2 IM immunizations did not induce any antibody responses in nasal secretions or cervical lymph nodes, which drain the nasal mucosa, IN immunizations alone or in combination with IM immunization induced mucosal and local responses. These data show that the IN followed by IM immunization strategy holds promise to significantly raise serum and local antibody and T cell responses against seasonal influenza strains, and possibly pandemic influenza strains, for which no pre-existing immunity exists.

Oral spray immunization may be an alternative to intranasal vaccine delivery to induce systemic antibodies but not nasal mucosal or cellular immunity

Sixty-five healthy adult volunteers were immunized four times at 1-week intervals with an inactivated whole-virus influenza vaccine based on the strain A/New Caledonia/20/99 (H1N1) without adjuvant. The vaccine was administered as nasal spray with a newly developed device to secure intranasal delivery (OptiMist, OptiNose AS, Oslo, Norway), as regular nasal spray, nasal drops or as an oral spray. Significant IgA-antibody responses in nasal secretions were induced in volunteers immunized intranasally but not after oral spray immunization. In saliva, IgA antibodies were only marginally amplified even after oral spray immunizations. At least 73% of the volunteers belonging to any group of vaccine delivery reached serum haemagglutination inhibition titres of 40 or higher, considered protective against influenza, after only two vaccine doses. Those who had the vaccine delivered intranasally also showed evidence from in vitro secretion of granzyme B that cytotoxic T cells had been stimulated. Although immunization with the breath-actuated OptiMist device and nasal drops were superior with respect to both mucosal and systemic immune responses, oral spray immunization might still be considered for studies of mucosal adjuvants that are not yet acceptable for intranasal use.

A novel intranasal Protollin-based measles vaccine induces mucosal and systemic neutralizing antibody responses and cell-mediated immunity in mice

Protollin-MV is a vaccine produced by mixing split measles virus (MV) antigen with the novel adjuvant Protollin (Neisseria meningitidis outer membrane proteins non-covalently complexed with Shigella flexneri 2a lipopolysaccharide). Intranasal immunization of mice with two or three doses of Protollin-MV induces both serum IgG and mucosal IgA with strong neutralizing activity. There is a dose-dependent shift towards lower IgG1:IgG2a ratios and MV-specific IFNgamma production in splenocytes. Intranasal Protollin-MV can therefore induce systemic and mucosal neutralizing antibody responses as well as elicit a balanced TH1/TH2-type response.

Intranasal administration of a proteosome-influenza vaccine is well-tolerated and induces serum and nasal secretion influenza antibodies in healthy human subjects

Two randomized, blinded, active comparator-controlled trials of a prototype monovalent A/Beijing/262/95 (H1N1) - proteosome vaccine delivered by intranasal spray were performed in healthy adults. Overall, the intranasal proteosome-adjuvanted vaccine was well-tolerated with only mild stuffy nose and rhinorrhea seen more frequently in recipients of vaccine than in recipients of intranasal saline, and there were no serious adverse events. The intranasal proteosome-adjuvanted vaccine induced serum hemagglutination inhibiting (HAI) and nasal secretory IgA (sIgA) responses specific for the influenza antigen. Serum HAI responses were most influenced by the dosage level, whereas mucosal sIgA responses, although demonstrable with both single-dose and two-dose vaccine regimens, appeared to be greater in response to two-dose regimens (regardless of dose level). Further evaluation of mucosal influenza immunization using the proteosome adjuvant/delivery system is clearly warranted.

Nasal vaccination with a proteosome-based adjuvant and glatiramer acetate clears beta-amyloid in a mouse model of Alzheimer disease

Amyloid beta-peptide (Abeta) appears to play a key pathogenic role in Alzheimer disease (AD). Immune therapy in mouse models of AD via Abeta immunization or passive administration of Abeta antibodies markedly reduces Abeta levels and reverses behavioral impairment. However, a human trial of Abeta immunization led to meningoencephalitis in some patients and was discontinued. Here we show that nasal vaccination with a proteosome-based adjuvant that is well tolerated in humans plus glatiramer acetate, an FDA-approved synthetic copolymer used to treat multiple sclerosis, potently decreases Abeta plaques in an AD mouse model. This effect did not require the presence of antibody, as it was observed in B cell-deficient (Ig mu-null) mice. Vaccinated animals developed activated microglia that colocalized with Abeta fibrils, and the extent of microglial activation correlated strongly with the decrease in Abeta fibrils. Activation of microglia and clearing of Abeta occurred with the adjuvant alone, although to a lesser degree. Our results identify a novel approach to immune therapy for AD that involves clearing of Abeta through the utilization of compounds that have been safely tested on or are currently in use in humans.

Immunoglobulin-A antibodies in upper airway secretions may inhibit intranasal influenza virus replication in mice but not protect against clinical illness

Mice immunized intranasally with a formalin-inactivated A/PR/8/34 (H1N1) influenza whole virus vaccine adjuvanted with cholera toxin, outer membrane vesicles from group B meningococci or formalin-inactivated whole cell Bordetella pertussis were protected against replication of the homologous virus in the nasal cavity. Only some mice were protected against clinical illness measured as weight loss and lowered body temperature. All mice immunized subcutaneously with one-tenth the intranasal vaccine dose without adjuvant were protected against clinical illness but not against local mucosal viral replication. Replicating virus was primarily found in animals with low concentrations of immunoglobulin (Ig)-A antibodies in saliva regardless of concentrations of IgG antibodies in serum. Clinical illness was seen only in those with low serum antibodies regardless of antibody levels in saliva. Nonreplicating nasal vaccines may not be sufficiently protective unless they also have a substantial influence on systemic immunity.

Influenza vaccines: recent advances in production technologies

In spite of ongoing annual vaccination programs, the seasonal influenza epidemics remain a major cause of high morbidity and mortality. The currently used "inactivated" vaccines provide very short-term and highly specific humoral immunity due to the frequent antigenic variations in the influenza virion. These intra-muscularly administered vaccines also fail to induce protective mucosal immunity at the portal of viral entry and destruction of the virally infected cells by induction of cytotoxic T lymphocytes. Therefore, it is necessary to develop immunologically superior vaccines. This article highlights some of the recent developments in investigational influenza vaccines. The most notable recent developments of interest include the use of immunopotentiators, development of DNA vaccines, use of reverse genetics, and the feasibility of mammalian cell-based production processes. Presently, due to their safety and efficacy, the cold-adapted "live attenuated" vaccines are seen as viable alternatives to the "inactivated vaccines". The DNA vaccines are gaining importance due to the induction of broad-spectrum immunity. In addition, recent advances in recombinant technologies have shown the possibility of constructing pre-made libraries of vaccine strains, so that adequately preparations can be made for epidemics and pandemics.

Mucosal (SIgA) and serum (IgG) immunologic responses in young adults following intranasal administration of one or two doses of inactivated, trivalent anti-influenza vaccine

Influenza morbidity affects the entire population and has an enormous impact upon the economic burden and the health care systems. Available vaccines are often unsatisfactory and many individuals are reluctant to receive injections. Intranasal immunization is painless, side effect free and may encourage a large number of individuals to participate in the vaccination programs. Ninety-two students were immunized intranasally once or twice, 21 days apart, with a trivalent inactivated whole influenza vaccine during three separate seasons (1996/1997, 1997/1998 and 1998/1999) with the recommended seasonal strains. The vaccine was well tolerated, without adverse effect and morbidity in the vaccinees during the winter season was low. Serum antibody response was determined by the hemagglutination inhibition (HI) test and nasal response by the enzyme-linked immunoadsorbant assay (ELISA). Following the second dose, mucosal antibody response was detected in 48.1-73.3% of immunized subjects. Serum and mucosal antibody levels (GMT) increased significantly to all the strains, with the exception of A/H3N2 in the mucosal response in 1997/1998. At the end of the trial, the percentage of immune subjects was over 93% to A/H1N1 strains, 60-71% to A/H3N2 and 64-66% to B/Harbin in 1996/1997 and 1997/1998, and 75-91% following one dose in 1998/1999. When serum and mucosal responses were combined, a higher percentage of responders was found (60-86%). Repeated vaccination does not seem to interfere with serum or mucosal response. The double barrier of mucosal and serum antibody may inhibit infection and decrease morbidity when infection occurs, thus limiting the spread of influenza in the community.

Vaccination with formalin-inactivated influenza vaccine protects mice against lethal influenza Streptococcus pyogenes superinfection

Intranasal infection with non-lethal influenza A virus (IAV) followed by infection with group A streptococci (GAS) induces invasive, lethal GAS infections, including necrotizing fasciitis, in mice. We demonstrate that subcutaneous immunization of formalin-inactivated IAV vaccine or intranasal immunization of IAV vaccine and cholera toxin protected more than 75% of mice from death by lethal IAV-GAS superinfection. The increased survival rate correlates with increase in IAV neutralizing activity and the levels of serum anti-IAV IgG. Moreover, elimination of IAV from the lungs of vaccinated mice led to depletion of GAS associated with alveolar epithelial cells. These findings suggest that formalin-inactivated IAV vaccine may be useful for prevention of secondary bacterial infections following prior IAV exposure.

Protollin™: a novel adjuvant for intranasal vaccines

Protollin is a novel adjuvant comprising Proteosomes non-covalently complexed with LPS. Intranasal immunization of mice with Protollin combined with detergent-split influenza antigens (HA) or recombinant influenza hemagglutinin (rHA) enhanced serum IgG and mucosal IgA levels by up to 250-fold compared with immunization with the antigens alone. IFN-gamma responses were also enhanced compared to the levels produced by splenocytes from mice immunized with antigen alone, while production of IL-5 was abrogated. Mice immunized with Protollin-rHA were completely protected against lethal challenge with influenza virus, demonstrating that Protollin is an effective mucosal adjuvant for prophylactic vaccines.

A nasal Proteosome influenza vaccine containing baculovirus-derived hemagglutinin induces protective mucosal and systemic immunity

The potential for enhancing the immunogenicity of recombinant (baculovirus-derived) influenza hemagglutinin (rHA) was investigated by comparing the immune responses elicited in mice by an intranasal (i.n.) rHA formulated with Proteosomes, with those induced by intramuscular (i.m.) or i.n. rHA alone. The Proteosome-rHA vaccine induced mucosal responses in the respiratory tract, as well as high serum IgG and hemagglutination inhibition (HAI) titers. In contrast, rHA alone given i.m. induced serum IgG without mucosal responses and was ineffective at inducing either mucosal or systemic responses when given i.n. Only mice immunized with the Proteosome-rHA vaccine were completely protected from both death and acute morbidity following live virus challenge, indicating that the i.n. Proteosome-rHA vaccine induced more complete protective immunity than the same doses of unformulated rHA given i.n. or i.m.

Role of secretory antibodies in the defence against infections

Adaptive immunity mediated by secretory antibodies is important in the defence against mucosal infections. Specific secretory immunoglobulin A (SIgA) can inhibit initial pathogen colonization by performing immune exclusion both on the mucosal surface and within virus-infected secretory epithelial cells without causing tissue damage. Resistance against toxin-producing bacteria such as Vibrio cholerae appears to be particularly dependent on SIgA antibodies. Like natural infections, live topical vaccines or adequate combinations of inactivated vaccines and mucosal adjuvants give rise not only to SIgA antibodies, but also to long-standing serum IgG and IgA responses. The intranasal route of vaccine application could be particularly attractive to achieve this result, but only if successful stimulation is obtained without the use of toxic adjuvants. The degree of protection after vaccination may range from complete inhibition of reinfection to reduction of symptoms. In this scenario it is generally difficult to determine unequivocally the relative importance of SIgA versus serum antibodies. However, infection models in knockout mice strongly support the notion that SIgA exerts a decisive role in protection and cross-protection against a variety of infectious agents.

Region-specific immunological response of the different laryngeal compartments: significance of larynx-associated lymphoid tissue

The occurrence of primary extranodal marginal-zone B-cell lymphoma [of the mucosa-associated lymphoid tissue (MALT) type] has only been described in the supraglottic region, implying that preexistent organized lymphoid tissue is present at that site only. To date, studies have not established clearly whether organized MALT shows a site-related distribution in the larynx. The supraglottic region of the false vocal folds and the subglottis from 87 unselected cadavers with no known history of nasal, oral, pharyngeal, laryngeal, tracheal, or esophageal disease were examined for the presence of organized MALT. Organized lymphoid tissue was found with the cytomorphological and immunophenotypic features of MALT in 100% of false vocal folds of children and in more than 90% of adolescents, decreasing to 7.1% in persons in their sixth decade, whereas MALT was completely absent in the subglottis in all age groups. The results explain why primary extranodal marginal-zone B-cell lymphoma has only been described in the supraglottic region but is absent in the subglottis. Moreover, the results suggest a region-specific immunological response of the different laryngeal areas as reflected in clinical observations and animal studies. However, the impact on presence or absence of laryngeal MALT awaits clarification.