CpG-containing oligodeoxynucleotides, in combination with conventional adjuvants, enhance the magnitude and change the bias of the immune responses to a herpesvirus glycoprotein

Humoral Immune Response of Mice against a Vaccine Candidate Composed of a Chimera of gB of Bovine Alphaherpesviruses 1 and 5

Infectious bovine rhinotracheitis (IBR) and bovine meningoencephalitis are caused by Bovine alphaherpesvirus (BoHV) types 1 and 5, which seriously threaten the global cattle industry. Vaccination to improve immunity is the most direct and effective means to prevent these conditions. Glycoprotein B (gB) is essential for the attachment of both viruses to permissive cells, and is a major target of the host immune system, inducing a strong humoral response. The aim of this study was to evaluate, in a murine model, the immune response of a candidate vaccine formulation composed of a chimeric BoHV-1 and BoHV-5 gB (DgB), expressed in Komagataella phaffii. The chimeric DgB vaccine adjuvanted with Montanide 50 ISA V2 or aluminum hydroxide was administered intramuscularly or subcutaneously. A control group and a group that received a commercial vaccine were inoculated subcutaneously. Higher titers of neutralizing antibodies against BoHV-1, BoHV-5, and a natural BoHV-1/5 recombinant strain were obtained with the oil-based candidate vaccine formulation administered intramuscularly. The results demonstrated that the chimeric DgB conserved important epitopes that were able to stimulate a humoral immune response capable of neutralizing BoHV-1, BoHV-5, and the recombinant strain, suggesting that the vaccine antigen is a promising candidate to be further evaluated in cattle.

A protein-based subunit vaccine with biological adjuvants provides effective protection against Pasteurella multocida in pigs

Streptococcus suis (S. suis) and Pasteurella multocida (P. multocida) are pathogens that can cause zoonotic diseases. P. multocida toxin (PMT) is an important virulence factor that causes atrophic rhinitis in pigs. Suilysin (Sly) is an extracellular protein of S. suis and has been shown to be a potential adjuvant. Previous studies have indicated that subunit vaccines containing several fragments of PMT as antigens are safer than traditional inactivated or live-attenuated vaccines. However, protein-based vaccines need strong adjuvants to enhance their immunogenicity. In this study, recombinant PMT-NC (rPMT-NC) protein antigen was formulated with either recombinant Sly (rSly) or CpG oligodeoxynucleotides (CpG) as the adjuvant. The immune responses elicited by these vaccines and the protective efficacy after challenge with live P. multocida were evaluated in piglets. In the dose-dependent test, piglets immunized with the low dose (100 µg) of rSly had increased antigen-specific total IgG, interferon (IFN)-γ gene expression, and CD4⁺ and CD8⁺ T-cell populations. Compared to piglets in the commercial (Al-gel) adjuvant and the control groups (p < 0.05), piglets in the biological adjuvant groups showed significantly reduced turbinate atrophy, nasal distortion, and lung lesion scores after challenge with P. multocida serotype A. Vaccines containing rSly or CpG adjuvant enhanced humoral and cellular immune responses and protection against P. multocida. This combination of a protein-based antigen formulated with a biological adjuvant showed synergistic and protective effects against atrophic rhinitis and has potential to be developed as part of a bivalent vaccine.

CpG Oligonucleotides as Vaccine Adjuvants

CpG Oligonucleotides (ODN) are immunomodulatory synthetic oligonucleotides specifically designed to stimulate Toll-like receptor 9. TLR9 is expressed on human plasmacytoid dendritic cells and B cells and triggers an innate immune response characterized by the production of Th1 and pro-inflammatory cytokines. This chapter reviews recent progress in understanding the mechanism of action of CpG ODN and provides an overview of human clinical trial results using CpG ODN to improve vaccines for the prevention/treatment of cancer, allergy, and infectious disease.

Effects of rotavirus NSP4 protein on the immune response and protection of the SR69A-VP8* nanoparticle rotavirus vaccine

Rotavirus causes severe diarrhea and dehydration in young children. Even with the implementation of the current live vaccines, rotavirus infections still cause significant mortality and morbidity, indicating a need for new rotavirus vaccines with improved efficacy. To this end, we have developed an SR69A-VP8*/S60-VP8* nanoparticle rotavirus vaccine candidate that will be delivered parenterally with Alum adjuvant. In this study, as parts of our further development of this nanoparticle vaccine, we evaluated 1) roles of rotavirus nonstructural protein 4 (NSP4) that is the rotavirus enterotoxin, a possible vaccine target, and an immune stimulator, and 2) effects of CpG adjuvant that is a toll-like receptor 9 (TLR9) ligand and agonist on the immune response and protection of our SR69A-VP8*/S60-VP8* nanoparticle vaccine. The resulted vaccine candidates were examined for their IgG responses in mice. In addition, the resulted mouse sera were assessed for i) blocking titers against interactions of rotavirus VP8* proteins with their glycan ligands, ii) neutralization titers against rotavirus replication in cell culture, and iii) passive protection against rotavirus challenge with diarrhea in suckling mice. Our data showed that the Alum adjuvant appeared to work better with the SR69A-VP8*/S60-VP8* nanoparticles than the CpG adjuvant, while an addition of the NSP4 antigen to the SR69A-VP8*/S60-VP8* vaccine may not help to further increase the immune response and protection of the resulted vaccine.

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

Muramyl dipeptide is the minimal structure of peptidoglycan with adjuvant properties. Replacement of the N-acetylmuramyl moiety and increase of lipophilicity are important approaches in the preparation of muramyl dipeptide analogues with improved pharmacological properties. Mannose receptors present on immunocompetent cells are pattern-recognition receptors and by mannose ligands binding they affect the immune system. Here we present the design, synthesis and biological evaluation of novel mannosylated desmuramyl peptide derivatives. Mannose was coupled to dipeptides containing a lipophilic adamantane on N- or C-terminus through a glycolyl or hydroxyisobutyryl linker. Adjuvant activities of synthesized compounds were investigated in the mouse model using ovalbumin as an antigen. Their activities were compared to the previously described mannosylated adamantane-containing desmuramyl peptide and peptidoglycan monomer. Tested compounds exhibited adjuvant activity and the strongest enhancement of IgG production was stimulated by compound 21 (Man-OCH₂-ᴅ-(1-Ad)Gly-ʟ-Ala-ᴅ-isoGln).

Effect of a DNA-based immunostimulant on growth, performance, and expression of inflammatory and immune mediators in beef calves abruptly weaned and introduced to a complete ration

The effect of a DNA immunostimulant on inflammatory and immune responses, performance, and health in calves following abrupt weaning and introduction to a concentrate diet was tested. Sixty-four single source Angus crossbred steers were weaned on day 1 and assigned to receive a DNA immunostimulant (TRT) or saline (CON) on days 0, 2, 4, and 6. On day 0, steers received clostridial and respiratory vaccines and anthelmintic; they were then transported 2 h, allocated to pens (n = 8 per pen), and introduced to total mixed ration. Daily intake, ADG, and feed efficiency were measured. Serum haptoglobin, tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β) were assayed by ELISA or AlphaLISA on days 0, 2, 4, 6, 14, and 28; serum-neutralizing antibodies (SNA) to bovine herpesvirus-1 and bovine viral diarrhea virus-1 (BVDV-1) were quantified on days 0, 28, 68, and 135. In a subset of cattle (n = 6 to 8 per treatment group), the percent macrophages and activated gamma delta (γδ) T cells in blood was determined by flow cytometry on days 2 and 6, and expression of mRNA for TNF-α, interferon-gamma (IFN-γ), IL-4, and IL-10 by stimulated blood mononuclear cells was assessed by real-time reverse transcriptase PCR on day 6. After 70 d, cattle were shipped 1,205 km to a feedlot and performance and health were followed. There was a significant effect of time on serum TNF-α, IL-1β, haptoglobin, and SNA (P < 0.001); the range in concentration among cattle on each day was large. The ratio of IFN-γ to IL-4 expression was significantly higher (P = 0.03) for TRT cattle, suggesting that treatment activated T-helper type 1 cells. There was a trend toward an improved feed conversion (P = 0.10) for TRT steers over the 70-d backgrounding period. There was no effect of treatment on feedlot performance or carcass merit (P > 0.10). During backgrounding, 1 TRT steer died of enterocolitis. In spite of backgrounding, cattle experienced an outbreak of bovine respiratory disease (BRD) in the feedlot and 1 of 31 TRT cattle and 5 of 32 CON cattle died of BRD. The immunostimulant modified some immune responses during backgrounding. Large variability in inflammatory responses during backgrounding indicated that events around weaning induce systemic inflammation that varies substantially among cattle.

Anti-leishmanial activity of Brevinin 2R and its Lauric acid conjugate type against L. major: In vitro mechanism of actions and in vivo treatment potentials

Leishmaniasis, as a major health problem in tropical and sub-tropical areas in the world, needs novel, safe, nontoxic and plausible therapeutic solutions for its control. As a part of innate immune system, natural antimicrobial peptides have a potential to be used as new generation of antibiotics especially after persistent resistance of conventional antimicrobial agents. Brevinin 2R, a member of Defensin families of host defense peptides, showed promising effects against bacterial and fungal infections as well as cancerous cell lines. In the current research, the anti-leishmanial effect of Brevinin 2R and its lauric acid conjugate was investigated against Leishmania major (L. major) parasite. The data revealed that, conjugation of fatty acid to Brevinin 2R, strengthen its effect on L. major promastigotes as well as toxicity and hemolytic effect. These peptides showed anitleishmanial activity through cell membrane disruption and changes in the electrical and mitochondrial membrane potential. No signs of apoptosis induction or caspase activation were detected. Despite its hemolytic and cytotoxic effect in in vitro conditions, lauric acid- Brevinin 2R (L- Brevinin 2R) did not show site specific adverse reactions in animal model. Treatment course with L- Brevinin 2R in the L. major infected mice exhibited decreased parasite load in the lymph nodes adjacent to the infected site despite cytokine production profile and footpad swelling data.

Seeking novel drugs against leishmaniasis is a necessity due to inefficiency of current medications. Brevinin 2R, as a non-hemolytic natural antimicrobial peptide, was effective against vast majority of bacterial and fungal infections as well as cancerous cell lines. In this regard in the current study, the efficacy of Brevinin 2R and its lauric acid conjugate version were studied against L. major parasite growth inhibition at in vitro and in animal model. The results exhibited that, conjugation of fatty acid to Brevinin 2R exacerbated anti-leishmanial effect. L- Brevinin 2R resolved the promastigotes through membrane disruption and changes in the membrane and mitochondrial potential. Also, L- Brevinin 2R was able to limit successfully the parasite load in the lymph nodes of L. major infected animals.

MPL and CpG combination adjuvants promote homologous and heterosubtypic cross protection of inactivated split influenza virus vaccine

Annual vaccination is not effective in conferring cross-protection against antigenically different influenza viruses. Therefore, it is of high priority to improve the cross protective efficacy of influenza vaccines. We investigated the adjuvant effects of monophosphoryl lipid A (MPL) and oligodeoxynucleotide CpG (CpG) on promoting homologous protection and cross-protection after vaccination of C57BL/6 and BALB/c mice with inactivated split virus. Combination adjuvant effects of MPL and CpG on improving homologous and cross protective vaccine efficacy were evident as shown by higher levels of homologous and cross-reactive binding IgG and hemagglutination inhibiting antibodies. Combination adjuvant effects on enhancing the protective efficacy against homologous and heterosubtypic virus were demonstrated by less weight loss, lower airway inflammatory disease, and better control of viral loads as well as prevention of inflammatory cytokines and cellular infiltrates. Overall, the findings in this study suggest that a combination adjuvant of different toll-like receptor ligands exhibits a unique pattern of innate and adaptive immune responses, contributing to improved homologous and heterosubtypic cross-protection by inactivated split virion influenza vaccination.

Protective humoral and CD4+ T cellular immune responses of Staphylococcus aureus vaccine MntC in a murine peritonitis model

Staphylococcus aureus can cause different types of diseases from mild skin infections to life-threatening sepsis worldwide. Owing to the emergence and transmission of multidrug-resistant strains, developing an impactful immunotherapy especially vaccine control approach against S. aureus infections is increasingly encouraged and supported. S. aureus manganese transport protein C (MntC), which is a highly-conserved cell surface protein, can elicit protective immunity against S. aureus and Staphylococcus epidermidis. In this study, we evaluated the humoral immune response and CD4⁺ T cell-mediated immune responses in a mouse peritonitis model. The results showed that MntC-specific antibodies conferred an essential protection for mice to reduce invasion of S. aureus, which was corroborated via the opsonophagocytic killing assay and passive immunization experiment in mice, and moreover MntC-induced Th17 played a remarkable part in preventing S. aureus infection since the MntC-induced protective immunity decreased after neutralization of IL-17 by antibody in vivo and the Th17 adoptive transferred-mice could partly resist S. aureus challenge. In conclusion, we considered that the MntC-specific antibodies and MntC-specific Th17 cells play cooperative roles in the prevention of S. aureus infection.

Human Neutrophil Peptide 1 as immunotherapeutic agent against Leishmania infected BALB/c mice

Human Neutrophil Peptide 1 (HNP1) produced by neutrophils, is a well-known antimicrobial peptide which plays a role both in innate as well as in adaptive immunity and is under intensive investigation as a potential therapeutic agent. Previous in vitro experiments have indicated the leishmaniacidal effect of recombinant HNP1 on Leishmania major (L. major) promastigotes and amastigotes. In the current study, we further extended the idea to explore the remedial effect of HNP1 in the two modalities of peptide therapy (folded HNP1) and gene therapy in L. major infected BALB/c mice. To this end, mice in five different groups received synthetic folded HNP1 (G1), pcDNA-HNP1-EGFP (G2), pcDNA-EGFP (G3), Amphotericin B (G4) and PBS (G5), which was started three weeks after infection for three consecutive weeks. Footpad swelling was monitored weekly and a day after the therapy ended, IFN-γ, IL-4, IL-10, IL-6 and nitric oxide produced by splenocytes were analyzed together with the parasite load in draining lymph nodes. Arginase activity and dermal histopathological changes were also analyzed in the infected footpads. We demonstrated that both therapeutic approaches effectively induced Th1 polarization and restricted parasite burden. It can control disease progression in contrast to non-treated groups. However, pcDNA-HNP1-EGFP is more promising in respect to parasite control than folded HNP1, but less effective than AmB treatment. We concluded with the call for a future approach, that is, a DNA-based expression of HNP1 combined with AmB as it can improve the leishmaniacidal efficacy.

The outbreak level of cutaneous leishmaniasis is approximated between one and 1.5 million individuals per year. Owning to several disadvantages of current therapies, special attention to expand novel and efficient therapies has been demanded. Among Anti-Microbial Peptides (AMPs), Human Neutrophil Peptide 1 (HNP1) is one of the most potential defensins. Our promising in vitro experiments have shown the leishmaniacidal effect of recombinant HNP1. Here, we displayed the remedial effect of HNP1 in two approaches including peptide therapy and gene therapy in susceptible mice infected with L. major. Our investigation showed that although both approaches could decrease the parasite load and induce Th1 immune response compared to the control group, pcDNA-HNP1-EGFP has a better effect compared to the folded HNP1. Hence, immunotherapy by HNP1 can help elicit proper immunity despite the direct effect on promastigotes and amastigotes forms of parasite.

Distinct Effects of Monophosphoryl Lipid A, Oligodeoxynucleotide CpG, and Combination Adjuvants on Modulating Innate and Adaptive Immune Responses to Influenza Vaccination

Monophosphoryl lipid A (MPL) and oligodeoxynucleotide CpG are toll-like receptor (TLR) 4 and 9 agonist, respectively. Here, we investigated the effects of MPL, CpG, and combination adjuvants on stimulating in vitro dendritic cells (DCs), in vivo innate and adaptive immune responses, and protective efficacy of influenza vaccination. Combination of MPL and CpG was found to exhibit distinct effects on stimulating DCs in vitro to secrete IL-12p70 and tumor necrosis factor (TNF)-α and proliferate allogeneic CD8 T cells. Prime immunization of mice with inactivated split influenza vaccine in the presence of low dose MPL+CpG adjuvants increased the induction of virus-specific IgG and IgG2a isotype antibodies. MPL and CpG adjuvants contribute to improving the efficacy of prime influenza vaccination against lethal influenza challenge as determined by body weight monitoring, lung function, viral titers, and histology. A combination of MPL and CpG adjuvants was effective in improving vaccine efficacy as well as in reducing inflammatory immune responses locally and in inducing cellular immune responses upon lethal influenza virus challenge. This study demonstrates unique adjuvant effects of MPL, CpG, and combination adjuvants on modulating innate and adaptive immune responses to influenza prime vaccination.

Efficacy comparison of adjuvants in PcrV vaccine against Pseudomonas aeruginosa pneumonia

Vaccination against the type III secretion system of P. aeruginosa is a potential prophylactic strategy for reducing the incidence and improving the poor prognosis of P. aeruginosa pneumonia. In this study, the efficacies of three different adjuvants, Freund's adjuvant (FA), aluminum hydroxide (alum) and CpG oligodeoxynucleotide (ODN), were examined from the viewpoint of inducing PcrV-specific immunity against virulent P. aeruginosa. Mice that had been immunized intraperitoneally with recombinant PcrV formulated with one of the above adjuvants were challenged intratracheally with a lethal dose of P. aeruginosa. The PcrV-FA immunized group attained a survival rate of 91%, whereas the survival rates of the PcrV-alum and PcrV-CpG groups were 73% and 64%, respectively. In terms of hypothermia recovery after bacterial instillation, PcrV-alum was the most protective, followed by PcrV-FA and PcrV-CpG. The lung edema index was lower in the PcrV-CpG vaccination group than in the other groups. PcrV-alum immunization was associated with the greatest decrease in myeloperoxidase in infected lungs, and also decreased the number of lung bacteria to a similar number as in the PcrV-FA group. There was less neutrophil recruitment in the lungs of mice vaccinated with PcrV-alum or PcrV-CpG than in those of mice vaccinated with PcrV-FA or PcrV alone. Overall, in terms of mouse survival the PcrV-CpG vaccine, which could be a relatively safe next-generation vaccine, showed a comparable effect to the PcrV-alum vaccine.

The Hen's Egg Test on Chorioallantoic Membrane: An Alternative Assay for the Assessment of the Irritating Effect of Vaccine Adjuvants

Local reactions are the most frequent adverse event associated with vaccines. Adjuvants are major constituents of many vaccines and they are frequently involved in these reactions, associated with their irritating effect and the stimulation of local inflammation. The hen's egg test on chorioallantoic membrane (HET-CAM) is an alternative toxicological method widely used to determine ocular irritation potential, but very few studies have demonstrated the utility of this method for assessing the irritant properties of vaccine adjuvants. In this work, known/experimental adjuvants were evaluated by both HET-CAM and an in vivo local toxicity study in mice to compare irritation scores to determine whether there was a correlation (Pearson test). Based on these data (r = 0.9034; P < 0.0001), the HET-CAM assay can be used as an alternate method for the prediction of the local toxicity potential of adjuvant candidates to be used in vaccines.

CpG-mediated augmentation of CD8+ T-cell responses in mice is attenuated by a water-in-oil emulsion (Montanide ISA-51) but enhanced by an oil-in-water emulsion (IDRI SE)

Adjuvants are a key component in enhancing immunogenicity of vaccines and play a vital role in facilitating the induction of the correct type of immunity required for each vaccine to be optimally efficacious. Several different adjuvants are found in licensed vaccines, and many others are in pre-clinical or clinical testing. Agonists for TLRs are potent activators of the innate immune system and some, such as CpG (TLR9 agonist), are particularly good for promoting cellular immunity because of the induction of Th1 cytokines. Emulsions that have both delivery and adjuvant properties are classified as water-in-oil (W/O) or oil-in-water (O/W) formulations. The W/O emulsion Montanide ISA-51, often combined with CpG, has been widely tested in cancer vaccine clinical trials. Squalene-based O/W emulsions are in licensed influenza vaccines, and T-cell responses have been assessed pre-clinically. No clinical study has compared the two types of emulsions, and the continued use of W/O with CpG in cancer vaccines may be because the lack of single adjuvant controls has masked the interference issue. These findings may have important implications for the development of vaccines where T-cell immunity is considered essential, such as those for cancer and chronic infections. Using particulate (hepatitis B surface antigen) and soluble protein (ovalbumin) antigen, we show in mice that a W/O emulsion (ISA-51) abrogates CpG-mediated augmentation of CD8(+) T-cell responses, whereas a squalene-based O/W emulsion significantly enhanced them.

Nanocarriers for DNA Vaccines: Co-Delivery of TLR-9 and NLR-2 Ligands Leads to Synergistic Enhancement of Proinflammatory Cytokine Release

Adjuvants enhance immunogenicity of vaccines through either targeted antigen delivery or stimulation of immune receptors. Three cationic nanoparticle formulations were evaluated for their potential as carriers for a DNA vaccine, and muramyl dipeptide (MDP) as immunostimulatory agent, to induce and increase immunogenicity of Mycobacterium tuberculosis antigen encoding plasmid DNA (pDNA). The formulations included (1) trimethyl chitosan (TMC) nanoparticles, (2) a squalene-in-water nanoemulsion, and (3) a mineral oil-in-water nanoemulsion. The adjuvant effect of the pDNA-nanocomplexes was evaluated by serum antibody analysis in immunized mice. All three carriers display a strong adjuvant effect, however, only TMC nanoparticles were capable to bias immune responses towards Th1. pDNA naturally contains immunostimulatory unmethylated CpG motifs that are recognized by Toll-like receptor 9 (TLR-9). In mechanistic in vitro studies, activation of TLR-9 and the ability to enhance immunogenicity by simultaneously targeting TLR-9 and NOD-like receptor 2 (NLR-2) was determined by proinflammatory cytokine release in RAW264.7 macrophages. pDNA in combination with MDP was shown to significantly increase proinflammatory cytokine release in a synergistic manner, dependent on NLR-2 activation. In summary, novel pDNA-Ag85A loaded nanoparticle formulations, which induce antigen specific immune responses in mice were developed, taking advantage of the synergistic combinations of TLR and NLR agonists to increase the adjuvanticity of the carriers used.

Immune response in domestic ducks following intradermal delivery of inactivated vaccine against H5N1 highly pathogenic avian influenza virus adjuvanted with oligodeoxynucleotides containing CpG motifs

Ducks are a natural reservoir for H5N1 highly pathogenic avian influenza (HPAI) viruses, which produces a range of clinical outcomes from asymptomatic infections to severe disease with mortality. Vaccination against HPAI is one of the few methods available for controlling avian influenza virus (AIV) infection in domestic ducks; therefore, it is necessary to improve vaccine efficacy against HPAI in domestic ducks. However, few studies have focused on enhancing the immune response by testing alternative administration routes and adjuvants. While attempting to maximize the efficacy of a vaccine, it is important to select an appropriate vaccine delivery route and adjuvant to elicit an enhanced immune response. Although several studies have indicated that the vaccination of ducks against HPAI viruses has offered protection against lethal virus challenge, the immunogenicity of the vaccine still requires improvement. In this study, we characterized the immune response following a novel vaccination strategy against H5N1 HPAI virus in domestic ducks. Our novel intradermal delivery system and the application of the cytosine-phosphodiester-guanine (CpG) oligodeoxynucleotide (ODN) adjuvant allowed us to obtain information regarding the sustained vaccine immunity. Compared with the intramuscular route of vaccination, the intradermal route resulted in higher antibody titer as well as lower antibody deviation following secondary vaccination. In addition, the use of a CpG-ODN adjuvant had a dose-sparing effect on antibody titer. Furthermore, when a high dose of antigen was used, the CpG-ODN-adjuvanted vaccine maintained a high mean antibody titer. This data demonstrates that intradermal immunization combined with administration of CpG-ODN as an adjuvant may be a promising strategy for improving vaccine efficacy in domestic ducks.

Improving adjuvant systems for polyclonal egg yolk antibody (IgY) production in laying hens in terms of productivity and animal welfare

The antibody production in the egg yolks of immunized laying hens is seen as a way of improving animal welfare compared with conventional production by mammals. Immunoglobulin Y (IgY) technology, however, has still to address welfare issues linked to the widespread use of an adjuvant in vaccines. Currently, Freund's adjuvants, complete (FCA) or incomplete (FIA), remain the standard. This study sought to evaluate various approaches used to enhance egg yolk antibody production in terms of both productivity and avian welfare. The outer membrane protein (OMP) of Salmonella Typhimurium was used as the prototype antigen. At 20 weeks of age, 56 ISA Brown hens, with specific-Salmonella-free status, were divided into seven groups (n=8) and received an initial intramuscular immunization. Hens in the two negative control groups received phosphate buffered saline (PBS) or FIA alone. Hens in the other groups received 80μg of Salmonella OMP emulsified with one of the following adjuvants: 200μl of FIA alone (T1); 200μl of FIA supplemented with 8μg of C-phosphate-guanosine oligodeoxynucleotides (CpG-ODN) (T2); and 280μl of Montanide ISA 70 VG (T4). Birds in the T3 group received the antigen in emulsion with FIA and were given the tested immunostimulatory component (l-carnitine) via their feed (100mg/kg). A positive control group (PC) received FCA for the first and final immunizations and FIA for the other boosters. Immunization was repeated after 20, 46, 82 and 221 days. Eggs were collected regularly until 242 days after the first immunization and the anti-Salmonella Typhimurium activities in the yolk were determined by ELISA. After 242 days, the birds were euthanized and the injection sites were evaluated for gross and microscopic lesions. Among the tested immunostimulatory approaches, supplementation of FIA with CpG-ODN led to a significant and long-lasting enhancement of the specific antibody response. This treatment was even higher than the positive benchmark using FCA in the first immunization. The study results showed that a clinical examination of injection sites is insufficient for drawing conclusions about the local tolerance of vaccines. Tissue damage was noticeable in all treatment groups. The birds receiving the Montanide adjuvant, however, had fewer and less severe lesions. Given these limited side-effects, Montanide ISA 70 VG could provide the depot effect needed to ensure the immunomodulatory efficiency of CpG-ODN. The association of these two adjuvants could prove a promising alternative to Freund's adjuvants (FA).

Bovine herpesvirus glycoprotein D: a review of its structural characteristics and applications in vaccinology

The viral envelope glycoprotein D from bovine herpesviruses 1 and 5 (BoHV-1 and -5), two important pathogens of cattle, is a major component of the virion and plays a critical role in the pathogenesis of herpesviruses. Glycoprotein D is essential for virus penetration into permissive cells and thus is a major target for virus neutralizing antibodies during infection. In view of its role in the induction of protective immunity, gD has been tested in new vaccine development strategies against both viruses. Subunit, DNA and vectored vaccine candidates have been developed using this glycoprotein as the primary antigen, demonstrating that gD has the capacity to induce robust virus neutralizing antibodies and strong cell-mediated immune responses, as well as protection from clinical symptoms, in target species. This review highlights the structural and functional characteristics of BoHV-1, BoHV-5 and where appropriate, Human herpesvirus gD, as well as its role in viral entry and interactions with host cell receptors. Furthermore, the interactions of gD with the host immune system are discussed. Finally, the application of this glycoprotein in new vaccine design is reviewed, taking its structural and functional characteristics into consideration.

CpG oligodeoxynucleotide protect neonatal piglets from challenge with the enterotoxigenic E. coli

CpG motifs activates mammalian lymphocytes and macrophages to produce cytokines and polyclonal Ig. These include IFN-γ, IL-12, TNF-a, which are important in the control of bacterial infection. But thus far, the innate immunostimulatory effects of CpG ODN against pathogen have been established mainly in mouse, monkey, sheep, chicken, but not in neonatal piglets. The purpose of this study is to determine the potential protection of CpG ODN against enterotoxigenic Escherichia coli (ETEC) (with which neonatal piglets were susceptible to infection in our lab) in neonatal piglets. Here, we show intranasal (IN)-mucosal and intramuscularly (IM) systemic administration of CpG ODN could enhance innate cellular (cytokine) immunity in the sera and intestine mucosa post challenge, and thereafter the development of antigen-specific antibodies in piglets. IN and IM immunizations of neonatal piglets without antigen both reduced the ETEC excretion and alleviated diarrhoea symptoms upon challenge, and IN route had better protection effects than IM route. Protection in this study was linked to induction of a Th1 response which induced by CpG ODN. Co-delivery with Emulsigen (EM), could improve protection mediated by CpG ODN. These observations indicate that IN administration of 100 μg/kg CpG ODN with 20% EM codelivery may represent a valuable strategy for induction of innate immunity against ETEC infection in neonatal piglets.

The effect of TLR9 agonist CpG oligodeoxynucleotides on the intestinal immune response of cobia (Rachycentron canadum)

Cytosine-guanine oligodeoxynucleotide (CpG ODN) motifs of bacterial DNA are recognized through toll-like receptor 9 (TLR9) and are potent activators of innate immunity. However, the interaction between TLR9 and CpG ODN in aquatic species has not been well characterized. Hence, cobia TLR9 isoform B (RCTLR9B) was cloned and its expression and induction in intestine were investigated. RCTLR9B cDNA consists of 3113bp encoding 1009 amino acids containing three regions, leucine rich repeats, transmembrane domain, and toll/interleukin-1 receptor (TIR) domain. Intraperitoneal injection of CpG ODN 2395 upregulated RCTLR9 A and B and MyD88 and also induced the expressions of Mx, chemokine CC, and interleukin IL-1β. Cobia intraperitoneally injected with CpG ODN 1668 and 2395 had increased survival rates after challenge with Photobacterium damselae subsp. piscicida. In addition, formulation of CpG ODN with formalin-killed bacteria (FKB) and aluminum hydroxide gel significantly increased expressions of RCTLR9 A (50 folds) and B (30 folds) isoforms at 10 dpi (CpG ODN 1668) and MyD88 (21 folds) at 6 dpv (CpG ODN 2395). Subsequently, IL-1β increased at 6 dpv in 1668 group. No histopathological damage and inflammatory responses were observed in the injected cobia. Altogether, these results facilitate CpG ODNs as an adjuvant to increase bacterial disease resistance and efficacy of vaccines in cobia.

Immune responses of mice against recombinant bovine herpesvirus 5 glycoprotein D

Glycoprotein D (gD) is essential for attachment and penetration of Bovine herpesvirus 5 (BoHV-5) into permissive cells, and is a major target of the host immune system, inducing strong humoral and cellular immune responses. The aim of this study was to evaluate in mice the immunogenicity of recombinant BoHV-5 gD (rgD5) expressed in Pichia pastoris. Vaccines formulated with rgD5 alone or adjuvanted with Montanide 50 ISA V2; Emulsigen or Emulsigen-DDA was administered intramuscularly or subcutaneously. Almost all formulations stimulated a humoral immune response after the first inoculation. The only exception was observed when the rgD5 was administered subcutaneously without adjuvant, in this case, the antibodies were observed after three doses. Higher titers of neutralizing antibodies were obtained with the three oil-based adjuvant formulations when compared to non-adjuvanted vaccine formulations. The rgD5 vaccine stimulated high mRNA expression levels of Th1 (INF-γ) and pro-inflammatory cytokines (IL-17, GM-CSF). The results demonstrated that the recombinant gD from BoHV-5 conserved important epitopes for viral neutralization from native BoHV-5 gD and was able to elicit mixed Th1/Th2 immune response in mice.

Vaccination with the RSV fusion protein formulated with a combination adjuvant induces long-lasting protective immunity

Respiratory syncytial virus (RSV) is one of the primary causative agents of upper and lower respiratory tract infections in young children, in particular infants. Recently, we reported the protective efficacy of a RSV vaccine formulation consisting of a truncated version of the fusion (F) protein formulated with a Toll-like receptor (TLR) agonist and an immunostimulatory peptide in a carrier system (ΔF/TriAdj). To evaluate the duration of immunity induced by this vaccine candidate, we carried out long-term trials. The ΔF was formulated with triple adjuvant (TriAdj) containing either polyinosinic : polycytidylic acid (polyI : C) or cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODNs) and administered intranasally to mice. One year after the second vaccination all mice were challenged with RSV. Both ΔF/TriAdj formulations mediated the induction of high levels of IgG1, IgG2a and virus-neutralizing antibodies, and IgA in the lungs. Based on the numbers of IFN-γ- and IL-5-secreting cells in the spleen, the immune response was slightly T-helper cell type 1 (Th1)-biased. This was confirmed by the presence of F85-93-specific CD8(+) effector T cells in the lungs of both ΔF/TriAdj(polyI : C)- and ΔF/TriAdj(CpG)-immunized mice. Both ΔF/TriAdj formulations induced RSV-specific CD8(+) T cells. However, ΔF/TriAdj(polyI : C) generated significantly higher IgG affinity maturation and higher numbers of RSV-specific CD8(+) effector memory T cells in lungs and CD8(+) central memory T cells in spleen and lymph nodes than ΔF/TriAdj(CpG). After RSV challenge, no virus replication and no evidence of vaccine-induced pathology were detected in mice immunized with either of the ΔF/TriAdj formulations, demonstrating that the duration of immunity induced with these vaccines is at least one year.

Recent progress concerning CpG DNA and its use as a vaccine adjuvant

CpG Oligonucleotides (ODN) are immunomodulatory synthetic oligonucleotides designed to specifically agonize Toll-like receptor 9. Here, we review recent progress in understanding the mechanism of action of CpG ODN and provide an overview of human clinical trial results using CpG ODN to improve the vaccines for cancer, allergy and infectious disease.

Vaccination of feedlot cattle with extracts and membrane fractions from two Mycoplasma bovis isolates results in strong humoral immune responses but does not protect against an experimental challenge

Mycoplasma bovis is one of the most significant contributors to the bovine respiratory syndrome (BRD) that causes major losses in feedlot and dairy farms. Current experimental vaccines against M. bovis are ineffective and in some cases seem to enhance disease. Experimental infection with M. bovis induces a predominantly Th2 response and high levels of IgG1, which is an inferior opsonin and hence lacks protective capacity. In an attempt to induce a balanced (Th1/Th2) immune response, we have used CpG ODN 2007 as an adjuvant in a trial involving vaccination of cattle with M. bovis total extracts and/or membrane fractions and subsequent intranasal inoculation with an infective dose of M. bovis prepared from two different clinical isolates. Significant IgG1 serum responses were observed against both, extracts and fractions while IgG2 responses were significant against the extracts only. Proliferation of peripheral blood mononuclear cells (PBMC) after incubation with M. bovis cells was only observed in post-challenge samples of cattle vaccinated with both extracts and fractions but not in samples of cattle immunized with the membrane fractions alone. All groups showed transient weight losses and increased temperatures however, there were no significant differences in clinical parameters and survival rates between the groups.

Influence of mannosylation on immunostimulating activity of adamant-1-yl tripeptide

The mannosylated derivative of adamant-1-yl tripeptide (D-(Ad-1-yl)Gly-L-Ala-D-isoGln) was prepared to study the effects of mannosylation on adjuvant (immunostimulating) activity. Mannosylated adamant-1-yl tripeptide (Man-OCH(2) CH(Me)CO-D-(Ad-1-yl)Gly-L-Ala-D-isoGln) is a non-pyrogenic, H(2) O-soluble, and non-toxic compound. Adjuvant activity of mannosylated adamantyl tripeptide was tested in the mouse model with ovalbumin as an antigen and in comparison to the parent tripeptide and peptidoglycan monomer (PGM, β-D-GlcNAc-(1→4)-D-MurNAc-L-Ala-D-isoGln-mesoDAP(εNH(2) )-D-Ala-D-Ala), a well-known effective adjuvant. The mannosylation of adamantyl tripeptide caused the amplification of its immunostimulating activity in such a way that it was comparable to that of PGM.

Effects on immunogenicity by formulations of emulsion-based adjuvants for malaria vaccines

New malaria vaccines are urgently needed to improve vaccine protective efficacy. PfCelTOS is a recombinant malaria vaccine antigen that has shown protective efficacy in a small-animal challenge model when combined with a water-in-oil emulsion adjuvant (Montanide ISA 720). In this report, we show that PfCelTOS vaccines containing GLA-SE (a stable oil-in-water emulsion combined with a Toll-like receptor 4 [TLR4] agonist) elicit strong Th1-type immune responses in BALB/c mice. These responses include higher antigen-specific IgG2a antibody titers and more gamma interferon (IFN-γ) production than those seen with a PfCelTOS vaccine containing Montanide ISA 720. Furthermore, reducing the emulsion dose from 2% to 1% or 0.5% (vol/vol) squalene in GLA-SE did not compromise immunogenicity. Emulsion dose titration in the absence of formulated GLA caused some reduction in humoral and cellular immune responses compared to those with the 2% squalene emulsion dose.

Synthesis and immunostimulating properties of novel adamant-1-yl tripeptides

The aim of this work was to prepare L- and D-(adamant-1-yl)-Gly-L-Ala-D-isoGln peptides in order to study their adjuvant (immunostimulating) activities. Adjuvant activity of adamant-1-yl tripeptides was tested in the mouse model using ovalbumin as an antigen and in comparison to the peptidoglycan monomer (PGM; β-D-GlcNAc-(1→4)-D-MurNAc-L-Ala-D-isoGln-mesoDAP(εNH(2) )-D-Ala-D-Ala) and structurally related adamant-2-yl tripeptides.

Immunoprotective activity of a Salmonid Alphavirus Vaccine: comparison of the immune responses induced by inactivated whole virus antigen formulations based on CpG class B oligonucleotides and poly I:C alone or combined with an oil adjuvant

CpG oligonucleotides and polyinosinic:polycytidylic acid (poly I:C) are toll-like receptor (TLR) agonists that mimic the immunostimulatory properties of bacterial DNA and double-stranded viral RNA respectively, and which have exhibited potential to serve as vaccine adjuvants in previous experiments. Here, a combination of CpGs and poly I:C together with water- or oil-formulated Salmonid Alphavirus (SAV) antigen preparations has been used for a vaccine in Atlantic salmon and tested for protection in SAV challenge trial. The results demonstrate that vaccination with a high dose of the SAV antigen induced protection against challenge with SAV which correlated with production of neutralizing antibodies (NAbs). As the high antigen dose alone induced full protection, no beneficial effect from the addition of CpG and poly I:C could be observed. Nevertheless, these TLR ligands significantly enhanced the levels of NAbs in serum of vaccinated fish. Interestingly, gene expression analysis demonstrated that while addition of oil suppressed the CpG/poly I:C-induced expression of IFN-γ, the upregulation of IFNa1 was substantially enhanced. A low dose of the SAV antigen combined with oil did not induce any detectable levels of NAbs either with or without TLR ligands present, however the addition of CpG and poly I:C to the low SAV antigen dose formulation significantly enhanced the protection against SAV suggesting that CpG/poly I:C may have enhanced a cytotoxic response - a process which is dependent on the up-regulation of type I IFN. These results highlight the immunostimulatory properties of the tested TLR ligands and will serve as a ground for further, more detailed studies aimed to investigate their capacity to serve as adjuvants in vaccine formulations for Atlantic salmon.

Efficacy of QCDCR formulated CpG ODN 2007 in Nile tilapia against Streptococcus iniae and identification of upregulated genes

The potential of using a QCDCR (quilA:cholesterol:dimethyl dioctadecyl ammonium bromide:carbopol:R1005 glycolipid) formulated CpG oligodeoxynucleotide (ODN), ODN 2007, to confer protection in Nile tilapia against Streptococcus iniae infection was evaluated in this study. At two days post treatment, QCDCR formulated ODN 2007 elicited significant (P<0.05) protection to Nile tilapia, with relative percent survival of 63% compared to fish treated by QCDCR alone. To understand the molecular mechanisms involved in the protective immunity elicited by ODN 2007, suppression subtractive cDNA hybridization technique was used to identify upregulated genes induced by ODN 2007. A total of 69 expressed sequence tags (ESTs) were identified from the subtractive cDNA library. Quantitative PCR revealed that 44 ESTs were significantly (P<0.05) upregulated by ODN 2007, including 29 highly (>10-fold) and 15 moderately (<10-fold) upregulated ESTs. Of all ESTs, putative peroxisomal sarcosine oxidase was upregulated the highest. The 69 ESTs only included six genes that had putative functions related to immunity, of which only two (putative glutaredoxin-1 and carboxypeptidase N catalytic chain) were confirmed to be significantly upregulated. Our results suggest that the protection elicited by ODN 2007 is mainly through innate immune responses directly or indirectly related to immunity.

CpG oligodeoxynucleotide and montanide ISA 206 adjuvant combination augments the immune responses of a recombinant FMDV vaccine in cattle

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals. To prevent the spread of FMDV, inactivated virus vaccines are used to immunize animals in developing countries. However, there are safety concerns. In addition, it is difficult to distinguish the vaccinated animals from those naturally infected ones. In our lab, we have developed a recombinant FMDV vaccine named A7. A7 contained multiple B cell and T cell epitopes, which reside in a capsid protein (VP1) of FMDV. To enhance its immunogenicity, A7 was formulated with CpG ODN RW03 in combination with Montanide ISA 206 (ISA), and the resultant vaccine (A7+ISA+CpG ODN RW03) was used to immunize mice and cattle. It was found that CpG ODN RW03 and ISA combination could facilitate A7 to induce a vigorous and long-lasting specific antibody response in mice and cattle. After FMDV challenge, 80% (4/5) of the calves immunized with A7+ISA+CpG ODN RW03 were protected, which was superior to those immunized with A7+ISA (25%, 1/4) or inactivated FMDV vaccine (50%, 2/4). These findings suggest that CpG ODN RW03 could be used with Montanide ISA 206 as a potent adjuvant for recombinant FMDV in cattle.

Improvement of the immunity of pig to Hog cholera vaccine by recombinant plasmid with porcine interleukin-6 gene and CpG motifs

In order to observe the dosage-effect of recombinant pig interleukin-6 gene and CpG motifs on the immune responses of swine to vaccine, a novel recombinant eukaryotic VPIL6C plasmid was packed with chitosan nanoparticles (CNP) prepared by ionic cross linkage, which contains pig interleukin-6 gene and immunostimulatory sequence consisted of 11 CpG motifs. CNP-VRIL6C was then utilized to inoculate 30-day-old piglets intramuscularly at the dosage of 0.5, 1.0 and 1.5mg/per capita, respectively. Meanwhile, the piglets were injected with attenuated classical Hog cholera vaccine and designated as A1, A2 and A3 group. The blood was weekly collected from the piglets after vaccination to detect the changes of immunoglobulins, specific antibody, interleukins, IFN-γ and immune cells. The results were found that compared to those of the control piglets injected with VR1020-CNP, the content of IgG, IgA and IgM, specific antibodies, IL-2, IL-6 and IFN-γ significantly increased in the sera from the treated three groups from 14 to 70 days after vaccination (P<0.05); the number of T(H), T(C) and CD3(+) positive T cells raised obviously in the blood of VPIL6C treated piglets (P<0.05). Also the above immune indexes of A1 group were significantly lower to different extent in comparison with those of A2 and A3 group from 14 to 56 days post inoculation (P>0.05). Moreover, the lymphocytes also remarkably elevated in the treated groups (P<0.05). These indicate that VPIL6C entrapped with CNP is a novel effective adjuvant to boost the humoral and cellular immunity of pig to Hog cholera, implying it's potentiality to enhance the resistance of pig against infectious diseases.

A novel triple adjuvant formulation promotes strong, Th1-biased immune responses and significant antigen retention at the site of injection

Ovalbumin (OVA) was labeled with a near infra-red dye (*OVA) and formulated with the host defense peptide indolicidin (Indol), CpG oligodeoxynucleotide (ODN) 1826 (CpG) and/or poly(p-dicarboxylatophenoxy)-phosphazene (PP4). The immunogenicity of these *OVA formulations was evaluated in mice. All double and triple adjuvant combinations elicited strong antibody responses. *OVA formulated with CpG ODN in combination with indolicidin, PP4 or both induced only IFN-γ, while formulations with indolicidin and/or PP4 promoted predominantly IL-5 production. Overall, both IgG and IFN-γ production was superior when *OVA was combined with CpG/Indol/PP4. Furthermore, mice injected with *OVA formulated with CpG/Indol/PP4 contained detectable *OVA in the injection site two months post immunization. These results indicate that the CpG/Indol/PP4 combination promotes prolonged antigen retention and strong, antigen-specific Th1-biased immune responses.

Comparative study of structurally related peptidoglycan monomer and muramyl dipeptide on humoral IgG immune response to ovalbumin in mouse

Structurally related peptidoglycan monomer (PGM) and muramyl dipeptide (MDP) differ in several aspects of biological activity but have in common immunostimulating properties. Comparative study of the effects of these adjuvants on humoral IgG immune response specific for protein antigen ovalbumin (OVA) was carried out in two inbred mouse strains, CBA and NIH/OlaHsd, and their ability to modulate the bias of immune response towards Th1/Th2 was evaluated. MDP had better adjuvant activity at some points than PGM, whereas both adjuvants stimulated Th2-biased immune response specific for OVA. In comparison to Complete Freund's adjuvant (CFA), as a golden standard of adjuvant action, both PGM and MDP exhibited considerably lower activity. Addition of PGM to Incomplete Freund's adjuvant (IFA) on humoral immune response was studied also, and the effect of such adjuvant formulation was compared to the effect of CFA. While CFA induced the switch towards Th1-biased immune response, the addition of PGM into IFA did have no impact on modulating the immune response towards more pronounced Th2-type of immune response, defined by IFA itself.

A novel canine favored CpG oligodeoxynucleotide capable of enhancing the efficacy of an inactivated aluminum-adjuvanted rabies vaccine of dog use

In order to develop novel canine CpG ODNs as adjuvant for rabies vaccine of dog use, a panel of CpG ODNs containing different CpG motifs was designed and screened for their ability to induce the proliferation of canine splenocytes. Three AACGTT motif-containing CpG ODNs, designated as YW07, YW08 and YW09, respectively, were outshined with stronger ability to activate canine immune cells. The CpG ODNs were tested for their adjuvant activity for rabies vaccine in mice and dogs. It was found that YW07 could facilitate the rabies vaccine to induce more vigorous and long-lasting specific antibody response in mice and dogs, respectively. These findings suggest that YW07, a canine favored CpG ODN, could be used as a novel adjuvant for developing more efficient rabies vaccine of dog use.

Intranasal immunization of mice with a bovine respiratory syncytial virus vaccine induces superior immunity and protection compared to those by subcutaneous delivery or combinations of intranasal and subcutaneous prime-boost strategies

Bovine respiratory syncytial virus (BRSV) infects cells of the respiratory mucosa, so it is desirable to develop a vaccination strategy that induces mucosal immunity. To achieve this, various delivery routes were compared for formalin-inactivated (FI) BRSV formulated with CpG oligodeoxynucleotide (ODN) and polyphosphazene (PP). Intranasal delivery of the FI-BRSV formulation was superior to subcutaneous delivery in terms of antibody, cell-mediated, and mucosal immune responses, as well as reduction in virus replication after BRSV challenge. Although intranasal delivery of FI-BRSV also induced higher serum and lung antibody titers and gamma interferon (IFN-gamma) production in the lungs than intranasal-subcutaneous and/or subcutaneous-intranasal prime-boost strategies, no significant differences were observed in cell-mediated immune responses or virus replication in the lungs of challenged mice. Interleukin 5 (IL-5), eotaxin, and eosinophilia were enhanced after BRSV challenge in the lungs of subcutaneously immunized mice compared to unvaccinated mice, but not in the lungs of mice immunized intranasally or through combinations of the intranasal and subcutaneous routes. These results suggest that two intranasal immunizations with FI-BRSV formulated with CpG ODN and PP are effective and safe as an approach to induce systemic and mucosal responses, as well to reduce virus replication after BRSV challenge. Furthermore, intranasal-subcutaneous and subcutaneous-intranasal prime-boost strategies were also safe and almost as efficacious. In addition to the implications for the development of a protective BRSV vaccine for cattle, formulation with CpG ODN and PP could also prove important in the development of a mucosal vaccine that induces protective immunity against human RSV.

Immune Mechanisms and Therapeutic Potential of CpG Oligodeoxynucleotides

Unmethylated CpG motifs in bacterial DNA and synthetic oligodeoxynucleotides activate immune cells that express Toll-like Receptor 9. Activation through this receptor triggers cellular signaling that leads to production of a proinflammatory and a Th1-type, antigen-specific immune response. The immunostimulatory effects of CpG oligodeoxynucleotides confer protection against infectious disease, allergy and cancer in animal models, and clinical trials have been initiated. However, CpG oligodeoxynucleotides may exacerbate disease in some situations. We will review current concepts in the mechanisms of activating Toll-like Receptor 9 with CpG oligodeoxynucleotides and highlight opportunities for using large animal models to better determine the mechanisms of action.

Formulation of bovine respiratory syncytial virus fusion protein with CpG oligodeoxynucleotide, cationic host defence peptide and polyphosphazene enhances humoral and cellular responses and induces a protective type 1 immune response in mice

Respiratory syncytial virus (RSV) is the leading cause of serious respiratory tract disease in children and calves; however, RSV vaccine development has been slow due to early observations that formalin-inactivated vaccines induced Th2-type immune responses and led to disease enhancement upon subsequent exposure. Hence, there is a need for novel adjuvants that will promote a protective Th1-type or balanced immune response against RSV. CpG oligodeoxynucleotides (ODNs), indolicidin, and polyphosphazene were examined for their ability to enhance antigen-specific immune responses and influence the Th-bias when co-formulated with a recombinant truncated bovine RSV (BRSV) fusion protein (DeltaF). Mice immunized with DeltaF co-formulated with CpG ODN, indolicidin, and polyphosphazene (DeltaF/CpG/indol/PP) developed higher levels of DeltaF-specific serum IgG, IgG1 and IgG2a antibodies when compared with DeltaF alone, and displayed an increase in the frequency of gamma interferon-secreting cells and decreased interleukin (IL)-5 production by in vitro restimulated splenocytes, characteristic of a Th1 immune response. These results were observed in both C57BL/6 and BALB/c strains of mice. When evaluated in a BRSV challenge model, mice immunized with DeltaF/CpG/indol/PP developed significantly higher levels of BRSV-neutralizing serum antibodies than mice immunized with the DeltaF protein alone, and displayed significantly less pulmonary IL-4, IL-5, IL-13 and eotaxin and reduced eosinophilia after challenge. These results suggest that co-formulation of DeltaF with CpG ODN, host defence peptide and polyphosphazene may result in a safe and effective vaccine for the prevention of BRSV and may have implications for the development of novel human RSV vaccines.

Approaches to enhancing immune responses stimulated by CpG oligodeoxynucleotides

CpG oligodeoxynucleotides (ODN) activate the immune system and are promising immunotherapeutic agents against infectious diseases, allergy/asthma and cancer. It has become apparent that while CpG ODN are potent immune activators in mice, their immune stimulatory effects are often less dramatic in humans and large animals. This disparity between rodents and mammals has been attributed to the differences in TLR9 expression in different species. This along with the sometimes transient activity of ODN may limit its potential immunotherapeutic applications. Several approaches to enhance the activity of CpG ODN have been explored including formulation of ODN in depot-forming adjuvants, and more recently, coadministration with polyphosphazenes, inhibitors of cytokines that downregulate TLR9 activation, and simultaneous activation with multiple TLR agonists. We will discuss these approaches and the mechanisms involved, with emphasis on what we have learned from large animal models.

Veterinary vaccines: alternatives to antibiotics?

The prevention of infectious diseases of animals by vaccination has been routinely practiced for decades and has proved to be one of the most cost-effective methods of disease control. However, since the pioneering work of Pasteur in the 1880s, the composition of veterinary vaccines has changed very little from a conceptual perspective and this has, in turn, limited their application in areas such as the control of chronic infectious diseases. New technologies in the areas of vaccine formulation and delivery as well as our increased knowledge of disease pathogenesis and the host responses associated with protection from disease offer promising alternatives for vaccine formulation as well as targets for the prevention of bacterial disease. These new vaccines have the potential to lessen our reliance on antibiotics for disease control, but will only reach their full potential when used in combination with other intervention strategies.

CpG oligonucleotide, host defense peptide and polyphosphazene act synergistically, inducing long-lasting, balanced immune responses in cattle

Vaccines consisting of subunit or protein antigens are less immunogenic than traditional vaccines, and therefore require formulation with an adjuvant. Conventional adjuvants, however, often cause undesirable injection site reactions and Th2-biased immune responses. Therefore, novel vaccine adjuvants which can safely enhance and selectively bias the resulting immune response are required. Here the adjuvant combination of CpG ODN, indolicidin and polyphosphazene (CpG+indol+PP) was evaluated for its ability to enhance and modulate the immune response when formulated with the antigen hen egg lysozyme (HEL). Cattle immunized with HEL co-adjuvanted with CpG+indol+PP developed higher antigen-specific humoral responses, and long-lasting cell-mediated immune responses, as evidenced by elevated levels of IFN-gamma secretion by re-stimulated PBMCs, that were superior even to EMULSIGEN((R)), an oil-in-water based adjuvant that was used as positive control. Physical characterization of the vaccines indicated that formulation of HEL with CpG+indol+PP resulted in the formation of antigen-adjuvant complexes, which may have contributed to their enhanced immunogenicity. Furthermore, the addition of polyphosphazene to CpG ODN and indolicidin dose-dependently enhanced the secretion of the cytokines IFN-alpha, TNF-alpha and IFN-gammain vitro, indicating that polyphosphazene can also synergize with CpG ODN and indolicidin to stimulate innate immune responses.

The novel adjuvant combination of CpG ODN, indolicidin and polyphosphazene induces potent antibody- and cell-mediated immune responses in mice

The need to enhance the immunogenicity of purified subunit antigens and modulate resulting immune responses has prompted the development of new adjuvants. Here, the ability of CpG oligodeoxynucleotides (ODN), a bovine host defence peptide indolicidin, and polyphosphazene to synergistically combine and enhance innate and adaptive immune responses was examined in mice. In vitro, the adjuvant combination of CpG ODN, indolicidin and polyphosphazene (CpG/indol/PP) enhanced the secretion of TNF-alpha, IL-12p40, and IL-6 by bone marrow-derived DCs (BMDCs) when compared to the individual components. When co-formulated with ovalbumin (OVA), CpG/indol/PP formed antigen-adjuvant complexes, and enhanced antibody and cell-mediated responses in mice, via both MHC I and II pathways, promoting a more balanced antibody-mediated and type 1-biased cell-mediated immune response. Furthermore, substitution of the proline residues of indolicidin with arginine increased the synergistic adjuvant effect of the peptide, and induced significantly higher IgG1 and IgG2a titers and IFN-gamma secretion, as well as increased uptake by antigen presenting cells. These results clearly demonstrate that the use of a combination of CpG ODN, indolicidin, and polyphosphazene as adjuvant can significantly enhance an antigen-specific immune response.

Co-administration of polyphosphazenes with CpG oligodeoxynucleotides strongly enhances immune responses in mice immunized with Hepatitis B virus surface antigen

An emerging paradigm in vaccinology is that multiple adjuvant combinations may be more effective than individual adjuvants in enhancing immune responses to vaccine antigens. We investigated whether the polyphosphazenes used in combination with CpG oligodeoxynucleotides (ODN) were potent adjuvant formulations. BALB/c mice were immunized subcutaneously with Hepatitis B surface antigen (HBsAg) alone, or in various combinations with poly[di(sodium carboxylatophenoxy)phosphazene] (PCPP), poly[di(sodium carboxylatoethylphenoxy)phosphazene] (PCEP) or CpG ODN. All three adjuvants enhanced HBsAg-specific IgG1 antibody responses with PCEP inducing the highest responses. PCEP and CpG ODN significantly enhanced the Th1-associated antibody isotype IgG2a. As expected CpG ODN induced predominantly Th1-type immune responses while PCEP was associated with mixed Th1/Th2 immune responses. Interestingly, PCEP and PCPP synergized with CpG ODN to further enhance antibody responses. Since the mechanisms which mediate the adjuvant activity of polyphosphazenes are not fully understood, we investigated whether PCEP and PCPP could stimulate innate immune responses. Incubation of mouse splenocytes with PCEP or PCPP (in the absence of antigen) stimulated production of IL-4 and IL-12, but only PCEP induced significant IFNgamma production. Additionally, IL-12 was not required for PCEP induced IFNgamma response. We conclude that the polyphosphazene-CpG ODN combination is a potent adjuvant formulation that is more effective in enhancing immune responses than either of the individual adjuvants. In addition, we provide evidence that PCEP and PCPP can stimulate innate cytokine production, suggesting a potential mechanism by which polyphosphazenes achieve their potent adjuvant effects.

Intranasal immunization of mice with a formalin-inactivated bovine respiratory syncytial virus vaccine co-formulated with CpG oligodeoxynucleotides and polyphosphazenes results in enhanced protection

As respiratory syncytial virus (RSV) targets the mucosal surfaces of the respiratory tract, induction of both systemic and mucosal immunity will be critical for optimal protection. In this study, the ability of an intranasally delivered, formalin-inactivated bovine RSV (FI-BRSV) vaccine co-formulated with CpG oligodeoxynucleotides (ODN) and polyphosphazenes (PP) to induce systemic and mucosal immunity, as well as protection from BRSV challenge, was evaluated. Intranasal immunization of mice with FI-BRSV formulated with CpG ODN and PP resulted in both humoral and cell-mediated immunity, characterized by enhanced production of BRSV-specific serum IgG, as well as increased gamma interferon and decreased interleukin-5 production by in vitro-restimulated splenocytes. These mice also developed mucosal immune responses, as was evident from increased production of BRSV-specific IgG and IgA in lung-fragment cultures. Indeed, the increases in serum and mucosal IgG, and in particular mucosal IgA and virus-neutralizing antibodies, were the most critical differences observed between FI-BRSV formulated with both CpG ODN and PP in comparison to formulations with CpG ODN, non-CpG ODN or PP individually. Finally, FI-BRSV/CpG/PP was the only formulation that resulted in a significant reduction in viral replication upon BRSV challenge. Co-formulation of CpG ODN and PP is a promising new vaccine platform technology that may have applications in mucosal immunization in humans.

Strategies for induction of protective immunity to bovine herpesvirus-1 in newborn calves with maternal antibodies

The objective of this study was to evaluate Th1 promoting strategies for vaccination of neonates against bovine herpesvirus-1 (BHV-1). A plasmid encoding a secreted truncated version of glycoprotein D (tgD) and tgD protein formulated with CpG oligodeoxynucleotide (ODN) effectively primed the immune system of newborn lambs, whereas without CpG ODN the tgD protein was less effective. Furthermore, a heterologous DNA prime-protein/CpG boost induced stronger and more balanced immune responses than either the DNA vaccine or a protein/CpG prime-DNA boost. Three of these strategies were compared as an approach to induce protective immunity in newborn calves with BHV-1-specific maternal antibodies. Whereas the DNA vaccine induced minimal protection, the DNA prime-protein boost resulted in reduced temperature response, weight loss and virus shedding in comparison to the placebo group. Close to complete protection against BHV-1 challenge was elicited in the calves immunized with the protein/CpG formulation, as these animals lost very little weight, had only slightly elevated temperatures and shed almost no virus.

Structure, Immunopathogenesis and Vaccines Against SARS Coronavirus

A new disease, severe atypical respiratory syndrome (SARS), emerged in China in late 2002 and developed into the first epidemic of the 21st century. The disease was caused by an unknown animal coronavirus (CoV) that had crossed the species barrier through close contact of humans with infected animals, and was identified as the etiological agent for SARS. This new CoV not only became readily transmissible between humans but also was also more pathogenic. The disease spread across the world rapidly due to the air travel, and infected 8096 people and caused 774 deaths in 26 countries on 5 continents. The disease is characterized by flu-like symptoms, including high fever, malaise, cough, diarrhea, and infiltrates visible on chest radiography. The overall mortality was about 10%, but varied profoundly with age; the course of disease seemed to be milder in the pediatric age group and resulted rarely in a fatal outcome, but the mortality in the elderly was as high as 50%. Aggressive quarantine measures taken by the health authorities have successfully contained and terminated the disease transmission. As a result there are no SARS cases recorded recently. Nevertheless there is a possibility that the disease may emerge in the population with high vigor. Significant progress has been made in understanding the disease biology, pathogenesis, development of animal models, and design and evaluation of different vaccines, and these are the focus of this chapter.