CpG DNA induces stronger immune responses with less toxicity than other adjuvants

Lipid Nanoparticle with 1,2-Di-O-octadecenyl-3-trimethylammonium-propane as a Component Lipid Confers Potent Responses of Th1 Cells and Antibody against Vaccine Antigen

Adjuvants are effective tools to enhance vaccine efficacy and control the type of immune responses such as antibody and T helper 1 (Th1)- or Th2-type responses. Several studies suggest that interferon (IFN)-γ-producing Th1 cells play a significant role against infections caused by intracellular bacteria and viruses; however, only a few adjuvants can induce a strong Th1-type immune response. Recently, several studies have shown that lipid nanoparticles (LNPs) can be used as vaccine adjuvants and that each LNP has a different adjuvant activity. In this study, we screened LNPs to develop an adjuvant that can induce Th1 cells and antibodies using a conventional influenza split vaccine (SV) as an antigen in mice. We observed that LNP with 1,2-di-O-octadecenyl-3-trimethylammonium-propane (DOTMA) as a component lipid (DOTMA-LNP) elicited robust SV-specific IgG1 and IgG2 responses compared with SV alone in mice and was as efficient as SV adjuvanted with other adjuvants in mice. Furthermore, DOTMA-LNPs induced robust IFN-γ-producing Th1 cells without inflammatory responses compared to those of other adjuvants, which conferred strong cross-protection in mice. We also demonstrated the high versatility of DOTMA-LNP as a Th1 cell-inducing vaccine adjuvant using vaccine antigens derived from severe acute respiratory syndrome coronavirus 2 and Streptococcus pneumoniae. Our findings suggest the potential of DOTMA-LNP as a safe and effective Th1 cell-inducing adjuvant and show that LNP formulations are potentially potent adjuvants to enhance the effectiveness of other subunit vaccines.

Dual-Antigen-Displaying Nanovaccines Elicit Synergistic Immunoactivation for Treating Cancer and Preventing Infectious Complications

As one of the most common complications, infection causes the majority of mortality in cancer patients. However, therapeutic strategies that can simultaneously suppress tumors and protect patients from infection have been rarely reported. Here, the use of dual-antigen-displaying nanovaccines (DADNs) is described to elicit synergistic immunoactivation for treating cancer and preventing infectious complications. DADNs are prepared by wrapping immunoadjuvant-loaded nanoparticles with a hybrid coating, which is fused from cell membranes that are separately genetically engineered to express tumor and infectious pathogenic antigens. Due to the presence of a dual-antigen combination, DADNs are able to promote the maturation of dendritic cells and more importantly to trigger cross-presentation of both combined antigens. During in vivo investigations, we find that DADNs can reverse immunosuppression by stimulating tumor-associated antigen-specific T-cell responses, resulting in significantly delayed tumor growth in mice. These nanovaccines also elicit effective protective immunity against tumor challenges and induce robust production of pathogenic antigen-specific immunoglobulin G antibody in a prophylactic study. This work offers a unique approach to develop dual-mode vaccines, which are promising for synchronously treating cancer and preventing infection.

Advances in Vaccine Adjuvants: Nanomaterials and Small Molecules

Adjuvants have been extensively and essentially formulated in subunits and certain inactivated vaccines for enhancing and prolonging protective immunity against infections and diseases. According to the types of infectious diseases and the required immunity, adjuvants with various acting mechanisms have been designed and applied in human vaccines. In this chapter, we introduce the advances in vaccine adjuvants based on nanomaterials and small molecules. By reviewing the immune mechanisms induced by adjuvants with different characteristics, we aim to establish structure-activity relationships between the physicochemical properties of adjuvants and their immunostimulating capability for the development of adjuvants for more effective preventative and therapeutic vaccines.

Nanoalum Formulations Containing Aluminum Hydroxide and CpG 1018TM Adjuvants: The Effect on Stability and Immunogenicity of a Recombinant SARS-CoV-2 RBD Antigen

Aluminum-salt vaccine adjuvants (alum) are commercially available as micron-sized particles with varying chemical composition and crystallinity. There are reports of enhanced adjuvanticity when the alum's particle size is reduced to the nanometer range. Previously, we demonstrated that a recombinant receptor-binding domain (RBD)-based COVID-19 vaccine candidate (RBD-J; RBD-L452K-F490W) formulated with aluminum hydroxide (Alhydrogel^®; AH) and CpG 1018™ (CpG) adjuvants induced potent neutralizing antibody responses in mice yet displayed instability during storage. In this work, we evaluated whether sonication of AH to the nanometer size range (nanoAH) could further enhance immunogenicity or improve storage stability of the above formulation. The addition of CpG to nanoAH (at mouse doses), however, caused re-agglomeration of nanoAH. AH-CpG interactions were evaluated by Langmuir binding isotherms and zeta potential measurements, and stabilized nanoAH + CpG formulations of RBD-J were then designed by (1) optimizing CpG:Aluminum dose ratios or (2) adding a small-molecule polyanion (phytic acid, PA). Compared with the micron-sized AH + CpG formulation, the two stabilized nanoAH + CpG formulations of RBD-J demonstrated no enhancement in SARS-CoV-2 pseudovirus neutralizing titers in mice, but the PA-containing nanoAH + CpG formulation showed improved RBD-J storage stability trends (at 4, 25, and 37 °C). The formulation protocols presented herein can be employed to evaluate the potential benefits of the nanoAH + CpG adjuvant combination with other vaccine antigens in different animal models.

Use of adjuvant ISA VG 71 to produce neutralizing egg yolk antibodies against bothropic venom

The use of egg yolk antibodies-IgY technology-represents an alternative to the production of mammalian immunoglobulins and has several advantages regarding animal welfare and lower costs of production. The use of adjuvants to achieve the hyperimmunization of laying hens plays a key role in the success of the production of high levels of the antibodies. In the present work, two different adjuvant systems (Freund's adjuvants and Montanide^TM ISA 71 VG) were compared to produce IgY anti-Bothrops alternatus. For the first immunization, formalin-inactivated Salmonella was added to Montanide^TM ISA 71 VG to emulate Freund's complete adjuvant which includes a mycobacteria antigen. After eight immunizations, IgY produced by using either adjuvant was able to neutralize the lethal activity of the venom in a mouse model, but differences were found regarding the recognition of components of the venom between the two adjuvants tested. Overall, Montanide^TM adjuvant used in this work could be a good alternative choice to produce antibodies capable of neutralizing the lethality of complex antigens. This adjuvant is commercially available and used in the formulation of several poultry vaccines and could be used for the IgY technology instead of traditional immunomodulators such as Freund's adjuvants. Key points • IgY extracts recognized major components of the venom.• Avidity indexes of the IgY extracts increased after the successive immunizations.• IgY obtained by two adjuvant systems neutralized the lethal activity of the venom.

In vivo assessment of triazine lipid nanoparticles as transfection agents for plasmid DNA

Non-viral vectors for in vivo delivery of plasmid DNA rely on optimized formulations to achieve robust transgene expression. Several cationic lipids have been developed to deliver nucleic acids, but most recent literature has focused on mRNA due to its increased expression profile and excluded plasmid DNA, which may have the advantage of being less immunogenic. In this study, we describe the in vivo evaluation of cationic triazine based lipids, previously prepared by our group. We identify one lipid with limited in vivo toxicity for studies to optimize the lipid formulations, which include an evaluation of the influence of PEG and helper lipids on transgene expression. We then demonstrate that lipoplexes, but not lipid nanoparticles, formed from triazine lipids achieve similar transgene expression levels as AAV vectors and offer enhanced expression as compared to a commercially available cationic lipid, DOTAP. Importantly, the lipid nanoparticles and lipoplexes induce minimal antibody profiles toward the expressed protein, while serving as a platform to induce robust antibody responses when directly delivering the protein. Collectively, these data demonstrate the potential for triazine based lipids as non-viral vectors for gene delivery, and highlights the need to optimize each formulation based on the exact contents to achieve enhanced transgene expression with plasmid DNA constructs.

A Precision Adjuvant Approach to Enhance Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Vaccines Optimized for Immunologically Distinct Vulnerable Populations

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has caused significant mortality, especially among older adults whose distinct immune system reflects immunosenescence. Multiple SARS-CoV-2 vaccines have received emergency use authorization and/or licensure from the US Food and Drug Administration and throughout the world. However, their deployment has heighted significant limitations, such by age-dependent immunogenicity, requirements for multiple vaccine doses, refrigeration infrastructure that is not universally available, as well as waning immunity. Thus, there was, and continues to be a need for continued innovation during the pandemic given the desire for dose-sparing, formulations stable at more readily achievable temperatures, need for robust immunogenicity in vulnerable populations, and development of safe and effective pediatric vaccines. In this context, optimal SARS-CoV-2 vaccines may ultimately rely on inclusion of adjuvants as they can potentially enhance protection of vulnerable populations and provide dose-sparing effects enabling single shot protection.

Systemic antiviral immunization by virus-mimicking nanoparticles-decorated erythrocytes

New vaccine technologies are urgently needed to produce safe and effective vaccines in a more timely manner to prevent future infectious disease pandemics. Here, we describe erythrocyte-mediated systemic antiviral immunization, a versatile vaccination strategy that boosts antiviral immune responses by using erythrocytes decorated with virus-mimetic nanoparticles carrying a viral antigen and a Toll-like receptor (TLR) agonist. As a proof of concept, polydopamine nanoparticles were synthesized via a simple in situ polymerization in which the nanoparticles were conjugated with the SARS-CoV-2 spike protein S1 subunit and the TLR7/8 agonist R848. The resulting SARS-CoV-2 virus-mimetic nanoparticles were attached to erythrocytes via catechol groups on the nanoparticle. Erythrocytes naturally home to the spleen and interact with the immune system. Injection of the nanoparticle-decorated erythrocytes into mice resulted in greater maturation and activation of antigen-presenting cells, humoral and cellular immune responses in the spleen, production of S1-specific immunoglobulin G (IgG) antibodies, and systemic antiviral T cell responses than a control group treated with the nanoparticles alone, with no significant negative side effects. These results show that erythrocyte-mediated systemic antiviral immunization using viral antigen- and TLR agonist-presenting polydopamine nanoparticles-a generalizable method applicable to many viral infections-is effective new approach to developing vaccines against severe infectious diseases.

The Synergistic Effects of Sulfated Lactosyl Archaeol Archaeosomes When Combined with Different Adjuvants in a Murine Model

Archaeosomes, composed of sulfated lactosyl archaeol (SLA) glycolipids, have been proven to be an effective vaccine adjuvant in multiple preclinical models of infectious disease or cancer. SLA archaeosomes are a promising adjuvant candidate due to their ability to strongly stimulate both humoral and cytotoxic immune responses when simply admixed with an antigen. In the present study, we evaluated whether the adjuvant effects of SLA archaeosomes could be further enhanced when combined with other adjuvants. SLA archaeosomes were co-administered with five different Toll-like Receptor (TLR) agonists or the saponin QS-21 using ovalbumin as a model antigen in mice. Both humoral and cellular immune responses were greatly enhanced compared to either adjuvant alone when SLA archaeosomes were combined with either the TLR3 agonist poly(I:C) or the TLR9 agonist CpG. These results were also confirmed in a separate study using Hepatitis B surface antigen (HBsAg) and support the further evaluation of these adjuvant combinations.

Toll-like Receptor 9 Agonists as Adjuvants for Nanoparticle-Based Nicotine Vaccine

Nicotine vaccine was considered a promising therapy against smoking addiction. The level of immune response that a nicotine vaccine can induce is pivotal to its efficacy. In this study, Toll-like receptor 9 agonists, namely, CpG ODN 1555 and CpG ODN 1826, were incorporated into a nanoparticle-based nicotine vaccine (NanoNicVac) to enhance its immunogenicity. The results showed that NanoNicVac containing either CpG ODN 1555 or CpG ODN 1826 could be rapidly internalized by dendritic cells. In mice trials, it was found that NanoNicVac with CpG ODN 1555 and CpG ODN 1826 induced 3.3- and 3.2-fold higher anti-nicotine antibody titer than that by the native NanoNicVac after two injections, respectively. Instead of enhancing the immunogenicity of the vaccine, however, mixtures of the two CpG ODNs were observed to exert an immune-suppressing effect on NanoNicVac. Finally, the histopathological examination on major organs of the mice immunized with the NanoNicVacs proved that NanoNicVac with either CpG ODN 1555 or CpG ODN 1826 as adjuvants did not cause detectable toxicity to the mice.

Broad and systemic immune-modulating capacity of plant-derived dsRNA

Double-stranded RNA (dsRNA) is well characterized as an inducer of anti-viral interferon responses. We previously reported that dsRNA extracted from a specific edible plant possesses an immune-modulating capacity to confer, in mice, resistance against respiratory viruses, including the H1N1 strain of the influenza A virus (IAV). We report here that the systemic immune-activating capacity of the plant-derived dsRNA protected mice from infection by a highly virulent H5N1 strain of the IAV. In addition, subcutaneous inoculation of the dsRNA together with the inactivated virion of the H5N1 strain of the IAV suppressed the lethality of the viral infection as compared with individual inoculation of either dsRNA or HA protein, suggesting its potential usage as a vaccination adjuvant. Moreover, intra-peritoneal inoculation of the dsRNA limited the growth of B16-F10 melanoma cells through the activation of NK cells in murine models. Taken together, this study demonstrated the systemic immune-modulating capacity of a plant-derived dsRNA and its potential for nucleic acid-based clinical applications.

Toward precision adjuvants: optimizing science and safety

PURPOSE OF REVIEW

The gradual replacement of inactivated whole cell and live attenuated vaccines with subunit vaccines has generally reduced reactogenicity but in many cases also immunogenicity. Although only used when necessary, adjuvants can be key to vaccine dose/antigen-sparing, broadening immune responses to variable antigens, and enhancing immunogenicity in vulnerable populations with distinct immunity. Licensed vaccines contain an increasing variety of adjuvants, with a growing pipeline of adjuvanted vaccines under development.

RECENT FINDINGS

Most adjuvants, including Alum, Toll-like receptor agonists and oil-in-water emulsions, activate innate immunity thereby altering the quantity and quality of an adaptive immune response. Adjuvants activate leukocytes, and induce mediators (e.g., cytokines, chemokines, and prostaglandin-E2) some of which are biomarkers for reactogenicity, that is, induction of local/systemic side effects. Although there have been safety concerns regarding a hypothetical risk of adjuvants inducing auto-immunity, such associations have not been established. As immune responses vary by population (e.g., age and sex), adjuvant research now incorporates principles of precision medicine. Innovations in adjuvant research include use of human in vitro models, immuno-engineering, novel delivery systems, and systems biology to identify biomarkers of safety and adjuvanticity.

SUMMARY

Adjuvants enhance vaccine immunogenicity and can be associated with reactogenicity. Novel multidisciplinary approaches hold promise to accelerate and de-risk targeted adjuvant discovery and development. VIDEO ABSTRACT: http://links.lww.com/MOP/A53.

Characterization and Protective Activity of Monoclonal Antibodies Directed against Streptococcus suis Serotype 2 Capsular Polysaccharide Obtained Using a Glycoconjugate

Streptococcus suis serotype 2 is an encapsulated bacterium and an important swine pathogen. Opsonizing antibody responses targeting capsular polysaccharides (CPSs) are protective against extracellular pathogens. To elucidate the protective activity of monoclonal antibodies (mAbs) directed against S. suis serotype 2 CPS, mice were immunized with a serotype 2 CPS-glycoconjugate and three hybridomas were isolated; of which, two were murine IgMs and the other a murine IgG1. Whereas the IgMs (mAbs 9E7 and 13C8) showed different reactivity levels with S. suis serotypes 1, 1/2, 2 and 14, the IgG1 (mAb 16H11) was shown to be serotype 2-specific. All mAbs targeted the sialylated chain of the CPSs. Using an opsonophagocytosis assay, the IgMs were opsonizing towards the S. suis serotypes to which they cross-react, while the IgG1 failed to induce bacterial elimination. In a model of mouse passive immunization followed by a lethal challenge with S. suis serotype 2, the IgG1 and IgM cross-reacting only with serotype 14 (mAb 13C8) failed to protect, while the IgM cross-reacting with serotypes 1, 1/2, and 14 (mAb 9E7) was shown to be protective by limiting bacteremia. These new mAbs show promise as new S. suis diagnostic tools, as well as potential for therapeutic applications.

Potentiating Antigen-Specific Antibody Production with Peptides Obtained from In Silico Screening for High-Affinity against MHC-II

Monoclonal antibodies with high affinity and specificity are essential for research and clinical purposes, yet remain difficult to produce. Agretope peptides that can potentiate antigen-specific antibody production have been reported recently. Here, we screened in silico for peptides with higher affinity against the agretope binding pocket in the MHC-II. The screening was based on the 3D crystal structure of a complex between MHC-II and a 14-mer peptide consisting of ovalbumin residues 323-339. Using this 14-mer peptide as template, we constructed a library of candidate peptides and screened for those that bound tightly to MHC-II. Peptide sequences that exhibited a higher binding affinity than the original ovalbumin peptide were identified. The peptide with the highest binding affinity was synthesized and its ability to boost antigen-specific antibody production in vivo and in vitro was assessed. In both cases, antigen-specific IgG antibody production was potentiated. Monoclonal antibodies were established by in vitro immunization using this peptide as immunostimulant, confirming the usefulness of such screened peptides for monoclonal antibody production.

B cell epitopes in the intrinsically disordered regions of neuraminidase and hemagglutinin proteins of H5N1 and H9N2 avian influenza viruses for peptide-based vaccine development

Avian influenza viruses (AIV) are very active in several parts of the globe and are the cause of huge economic loss for the poultry industry and also human fatalities. Three dimensional modeling was carried out for neuraminidase (NA) and hemagglutinin (HA) proteins of AIV. The C-score, estimated TM-Score, and estimated root-mean-square deviation (RMSD) score for NA of H5N1 were -1.18, 0.57 ± 0.15, and 9.8 ± 7.6, respectively. The C-score, estimated TM-Score, and estimated RMSD score for NA of H9N2 were -1.43, 0.54 ± 0.15, and 10.5 ± 4.6, respectively. The C-score, estimated TM-Score, and estimated RMSD score for HA of H5N1 were -0.03, 0.71 ± 0.12, and 7.7 ± 4.3, respectively. The C-score, estimated TM-Score, and estimated RMSD score for HA of H9N2 were -0.57, 0.64 ± 0.13, and 8.9 ± 4.6, respectively. Intrinsically disordered regions were identified for the NA and HA proteins of H5N1 and H9N2 with the use of PONDR program. Linear B cell epitope was predicted using BepiPred 2 program for NA and HA of H5N1 and H9N2 avian influenza strains. Discontinuous epitopes were predicted by Discotope 2 program. The linear epitopes that were considered likely to be immunogenic and within the intrinsically disordered region for the NA of H5N1 was TKSTNSRSGFEMIWDPNGWTGTDSSFSVK, and for H9N2 it was VGDTPRNDDSSSSSNCRDPNNERGAP. In the case of HA of H5N1, it was QRLVPKIATRSKVNGQSG and ATGLRNSPQRERRRKK; for H9N2 it was INRTFKPLIGPRPLVNGLQG and SLKLAVGLRNVPARSSR. The discontinuous epitopes of NA of H5N1 and H9N2 were identified at various regions of the protein structure spanning from amino acid residue positions 90 to 449 and 107 to 469, respectively. Similarly, the discontinuous epitopes of HA of H5N1 and H9N2 were identified in the amino acid residue positions 27 to 517 and 136 to 521, respectively. This study has identified potential and highly immunogenic linear and conformational B-cell epitopes towards developing a vaccine against AIV both for human and poultry use.

Novel adjuvants derived from attenuated lipopolysaccharides and lipid As of purple non-sulfur photosynthetic bacteria

Adjuvants are substances that enhance adaptive immune response to antigen. Development of a safe and effective immunostimulant adjuvant is essential for the efficacy of a vaccine to protect against infectious pathogens. Purple non-sulfur photosynthetic bacteria exhibited nontoxic natural lipid A variants that are distinct in their chemical structures from that of the Escherichia coli-type lipid A. In this study, the adjuvant efficacy of attenuated lipid A variants and their corresponding lipopolysaccharides (LPSs), derived from purple photosynthetic bacteria (Rhodocyclus tenuis and Rhodobacter sphaeroides) were evaluated. LPS was extracted using modified phenol-chloroform-petroleum ether method and lipid A was separated by mild acid hydrolysis. Trinitrophenol (TNP) was conjugated to hen egg albumin (TNP-HEA) and used as haptenic antigen. The LPS and lipid A adjuvant candidates were formulated in oil-in-water emulsion (OIWE) and evaluated to elicit anti-TNP IgG against TNP-HEA conjugate in BALB/c female mice. The anti-TNP IgG titers were measured using ELISA. The intact LPS-based adjuvants present in OIWE formulation showed significantly higher efficacy to elicit anti-TNP IgG titers against TNP-HEA conjugate compared to their corresponding lipid A-based adjuvants. As expected, the OIWE formulations of all LPS- and lipid A-based adjuvant candidates showed higher activities compared to the aqueous formulations. Slow reduction in the levels of anti-TNP IgG antibodies in the serum was observed over 4 months after immunization using the LPS- and lipid A-based adjuvant candidates which may provide a long protection against pathogens. The attenuated LPSs and lipid A's from the photosynthetic bacteria showed promising results to develop novel safe and effective adjuvants that can evoke the immune response. The most promising adjuvant candidate was the LPS-based adjuvant from R. tenuis.

Recent Advances in Polymeric Nanomedicines for Cancer Immunotherapy

Immunotherapy has emerged as a promising approach to treat cancer, since it facilitates eradication of cancer by enhancing innate and/or adaptive immunity without using cytotoxic drugs. Of the immunotherapeutic approaches, significant clinical potentials are shown in cancer vaccination, immune checkpoint therapy, and adoptive cell transfer. Nevertheless, conventional immunotherapies often involve immune-related adverse effects, such as liver dysfunction, hypophysitis, type I diabetes, and neuropathy. In an attempt to address these issues, polymeric nanomedicines are extensively investigated in recent years. In this review, recent advances in polymeric nanomedicines for cancer immunotherapy are highlighted and thoroughly discussed in terms of 1) antigen presentation, 2) activation of antigen-presenting cells and T cells, and 3) promotion of effector cells. Also, the future perspectives to develop ideal nanomedicines for cancer immunotherapy are provided.

Fingolimod can act as a facilitator to establish the primary T-cell response with reduced need of adjuvants

The CD8⁺ T-cell response is an essential part of the adaptive immunity. Adjuvants are routinely required for priming of T cells against antigens encountered in lymph nodes (LNs) to generate antigen-specific immunity but may concomitantly trigger unexpected inflammatory responses. Sphingosine-1-phosphate (S1P) induces transient desensitization of S1P receptors on LN T cells and temporarily blocks their egress, leading to prolonged intranodal retention that allows effective immunosurveillance and increases the chance of priming. In light of the regulatory role of S1P in T-cell migration, we here develop a strategic approach to the T-cell priming with protein vaccine containing low-dose TLR-based adjuvants (LDAV) to induce antigen-specific CD8⁺ T cell responses as efficiently as using regular dose adjuvants in vaccine (RDAV). We found that when combined with one low dose of the S1P analog fingolimod administered into the same vaccination site posteriorly at a specific time, LDAV can elicit a primary response that reaches the level of that induced by RDAV with respect to the response magnitude and functionality. Time-course studies indicate that LDAV and fingolimod in combination act to mimic the expansion kinetics of RDAV-primed antigen-specific CD8⁺ T cells. Further, intranodal accumulation of cDC1 is markedly enhanced in mice receiving the combination vaccination despite the decrease in adjuvant use. Of particular note is the marginal cutaneous inflammation at the injection site, indicating an added benefit of using fingolimod. Therefore, fingolimod as a nonadjuvant agent essentially facilitates antigen-specific T-cell priming with reduced need of adjuvants and minimized adverse reactions.

Investigations into the efficacy of multi-component cocaine vaccines

Although cocaine addiction remains a serious health and societal problem in the United States, no FDA-approved treatment has been developed. Vaccines offer an exciting strategy for the treatment of cocaine addiction; however, vaccine formulations need to be optimized to improve efficacy. Herein, we examine the effectiveness of a tricomponent cocaine vaccine, defined as having its hapten (GNE) and adjuvant (cytosine-guanine oligodeoxynucleotide 1826, CpG ODN 1826) covalently linked via the immunogenic protein ovalbumin (OVA). The tricomponent vaccine (GNE-OVA-CpG 1826) and a vaccine of analogous, individual components (GNE-OVA+CpG ODN 1826) were found to similarly induce highly specific anticocaine antibody production in mice and block cocaine's stimulant effects in hyperlocomotor testing.

CpG ODN1826 as a Promising Mucin1-Maltose-Binding Protein Vaccine Adjuvant Induced DC Maturation and Enhanced Antitumor Immunity

Mucin 1 (MUC1), being an oncogene, is an attractive target in tumor immunotherapy. Maltose binding protein (MBP) is a potent built-in adjuvant to enhance protein immunogenicity. Thus, a recombinant MUC1 and MBP antitumor vaccine (M-M) was constructed in our laboratory. To enhance the antitumor immune activity of M-M, CpG oligodeoxynucleotides 1826 (CpG 1826), a toll-like receptor-9 agonist, was examined in this study as an adjuvant. The combination of M-M and CpG 1826 significantly inhibited MUC1-expressing B16 cell growth and prolonged the survival of tumor-bearing mice. It induced MUC1-specific antibodies and Th1 immune responses, as well as the Cytotoxic T Lymphocytes (CTL) cytotoxicity in vivo. Further studies showed that it promoted the maturation and activation of the dendritic cell (DC) and skewed towards Th1 phenotype in vitro. Thus, our study revealed that CpG 1826 is an efficient adjuvant, laying a foundation for further M-M clinical research.

Subcutaneous administration CpG-ODNs acts as a potent adjuvant for an HIV-1-tat-based vaccine candidate to elicit cellular immunity in BALB/c mice

OBJECTIVE

To evaluate the combined effects of CpG oligodeoxynucleotides (CpG-ODNs) adjuvant and subcutaneous injection route on efficacy of a HIV-1-tat DNA vaccine candidate using BALB/c mice as an animal model.

RESULTS

Evaluation of cellular and humoral immunity of mice injected subcutaneously with HIV-1-tat gene cloned into a pcDNA3.1 vector indicated that significant levels of IFN-γ cytokine secretion (900 pg/ml), lymphocyte proliferation (2.5 stimulation index) and IgG_2a (1.45 absorbance 450 nm) production could be achieved. These indicators of stimulated cellular immunity were elicited 2 weeks after the last injection (P < 0.05).

CONCLUSIONS

Formulation of HIV-1-tat DNA vaccine candidate with CpG-ODNs as an adjuvant while administrated subcutaneously are a promising approach to induce effective cellular immunity responses against HIV-1 infection.

CpG-oligodeoxynucleotides developed for grouper toll-like receptor (TLR) 21s effectively activate mouse and human TLR9s mediated immune responses

Synthetic phosphorothiolate-modified CpG-oligodeoxynucleotides (CpG-ODNs) are potent immune stimuli. Toll-like receptor (TLR) 9 and TLR21 are their cellular receptors in different species. The structural requirements for CpG-ODN to strongly activate TLR9 have been relatively well studied, but studies on TLR21 are in their infancy. Therefore, in this study, we investigated the interaction between CpG-ODNs and TLR21s from groupers (Epinephelus spp.), which are economically important fish species. We cloned the cDNA of giant grouper (E. lanceolatus) TLR21, and compared its sequence with orange-spotted grouper (E. coioides) TLR21A and TLR21B. These three receptors were activated by CpG-ODNs containing the GTCGTT motif but not by those containing the GACGTT motif. We developed two CpG-ODNs that contained 19 phosphorothiolated deoxynucleotides with one or two GTCGTT motifs. These CpG-ODNs had better activity on grouper TLR21s than currently developed CpG-ODNs, and produced similar immune stimulatory profiles when applied to cells isolated from orange-spotted grouper. The developed CpG-ODNs also effectively activated both human and mouse TLR9-mediated NF-κB activation and cytokine productions. These findings suggest that the GTCGTT motif is required for CpG-ODNs to activate grouper TLR21s, and that the CpG-ODNs that were developed for grouper TLR21s contain structures that effectively activate human and mouse TLR9s.

Synergistic oligodeoxynucleotide strongly promotes CpG-induced interleukin-6 production

Background

Bacterial genomes span a significant portion of diversity, reflecting their adaptation strategies; these strategies include nucleotide usage biases that affect chromosome configuration. Here, we explore an immuno-synergistic oligodeoxynucleotide (iSN-ODN, named iSN34), derived from Lactobacillus rhamnosus GG (LGG) genomic sequences, that exhibits a synergistic effect on immune response to CpG-induced immune activation.

Methods

The sequence of iSN34 was designed based on the genomic sequences of LGG. Pathogen-free mice were purchased from Japan SLC and maintained under temperature- and light-controlled conditions. We tested the effects of iSN34 exposure in vitro and in vivo by assessing effects on mRNA expression, protein levels, and cell type in murine splenocytes.

Results

We demonstrate that iSN34 has a significant stimulatory effect when administered in combination with CpG ODN, yielding enhanced interleukin (IL)-6 expression and production. IL-6 is a pleotropic cytokine that has been shown to prevent epithelial apoptosis during prolonged inflammation.

Conclusions

Our results are the first report of a bacterial-DNA-derived ODN that exhibits immune synergistic activity. The potent over-expression of IL-6 in response to treatment with the combination of CpG ODN and iSN34 suggests a new approach to immune therapy. This finding may lead to novel clinical strategies for the prevention or treatment of dysfunctions of the innate and adaptive immune systems.

Electronic supplementary material

The online version of this article (10.1186/s12865-017-0227-7) contains supplementary material, which is available to authorized users.

A plasmid containing CpG ODN as vaccine adjuvant against grass carp reovirus in grass carp Ctenopharyngodon idella

CpG oligodeoxynucleotides (ODNs) are proved to have strong immune stimulatory activity. Plasmids containing CpG ODNs could be conveniently and low-costly used as vaccine adjuvant. However, they are different among various plasmids, motif repeats, species, etc. In the present study, plasmid pcDNA3.1 (+) containing five repetitions of CpG ODN 1670A named pcDNA3.1-1670A*5 with strong immunostimulation was screened out from twelve recombinant plasmids and three empty vectors by cell proliferation activity, interferon promoter activities and immune related gene expressions in CIK cells. It works through TLR9-mediated signaling pathway, triggering the immune related genes expression. Furthermore, the potentiality of pcDNA3.1-1670A*5 as adjuvant was tested in vivo. pcDNA3.1-1670A*5 was co-inoculated with inactivated GCRV vaccine on grass carp fingerlings. Immunoglobulins (IgM, IgD, IgZ), TLR9, IFNγ2, IFN1, TNF-α, Mx2 and VP4 were examined. Ultimately, pcDNA3.1-1670A*5 significantly enhanced the expressions of IgM in serum, head kidney and spleen, recognition receptor TLR9 as well as antiviral effector molecule Mx2, and inhibited GCRV proliferation in head kidney and spleen tissues. The present study explored the application and mechanism of plasmid containing CpG ODN as high-efficient adjuvant to promote efficiency of vaccine and control disease in grass carp, which will contribute to the development of new type CpG ODN adjuvant in aquaculture industry.

Nanoliposomes carrying HER2/neu-derived peptide AE36 with CpG-ODN exhibit therapeutic and prophylactic activities in a mice TUBO model of breast cancer

This study was designed to prepare and characterize nanoliposomal vaccine formulation encapsulating AE36 HER2/neu-derived peptide with or without CpG and evaluate the immunologic and therapeutic responses of that in BALB/c mice model of Her2 overexpressing breast cancer. AE36 was encapsulated in liposomes composed of DOTAP, DOPE and Cholesterol (DDC) or DD with. The formulations could induce both CD8+ and CD4+ responses and stimulate production of cytokines which was detected by Enzyme-linked immunospot assay (ELISpot) kits, cytotoxicity test and intracellular cytokine assay by flow cytometry. The formulation showed both therapeutic and prophylactic effects in BALB/c mice bearing Her2⁺ breast cancer. DDC+CpG showed the best effect in prophylactic study and DD+pG showed the best effect in therapeutic study, which both of them decreased the size of tumors significantly. The engineered nanoliposomes containing AE36 could be a candidate vaccine for the treatment or prophylaxis of HER2⁺ breast cancer and merits further investigation.

Adjuvants for Animal Vaccines

Vaccines are essential tools for the prevention and control of infectious diseases in animals. One of the most important steps in vaccine development is the selection of a suitable adjuvant. The focus of this review is the adjuvants used in vaccines for animals. We will discuss current commercial adjuvants and experimental formulations with attention to mineral salts, emulsions, bacterial-derived components, saponins, and several other immunoactive compounds. In addition, we will also examine the mechanisms of action for different adjuvants, examples of adjuvant combinations in one vaccine formulation, and challenges in the research and development of veterinary vaccine adjuvants.

Influence of adjuvant formulation on inducing immune response in mice immunized with a recombinant serpin from Trichinella spiralis

Nematodes of the genus Trichinella are one of the most widespread zoonotic pathogens on the world, and they can still cause major public health problems in many parts of the world. Vaccination against the helminth nematode Trichinella could be a good strategy to reduce the risk of human and animal infection. It was our aim to evaluate three adjuvants, which could be used as an efficient vaccine for animals in combination with rTs-Serpin antigen. In this study, BALB/c mice were vaccinated by an intramuscular route with rTs-Serpin antigen from the parasite Trichinella spiralis in combination with three different adjuvant formulations: Montanide ISA201, Montanide IMS 1313 N PR VG and Freund's complete adjuvant/Freund's incomplete adjuvant (FCA/FIA). The dynamics of IgG, IgM, IgE and cytokine production from spleen cells and worm reduction rate of the vaccinated mice were analysed. The results showed that rTs-serpin can induce partial protection against Trichinella larvae challenge in mice, when compared to the FCA-/FIA-formulated vaccination, the IMS1313 plus rTs-serpin mixture showed higher humoral immunity and similar levels of cellular immunity and worm reduction rate. The study suggested that Montanide IMS nanoparticles 1313 are as effective as FCA but less toxic; thus, Montanide IMS nanoparticles 1313 can be used as a good candidate of adjuvant for developing vaccine against Trichinella spiralis.

Porcine Dendritic Cells as an In Vitro Model to Assess the Immunological Behaviour of Streptococcus suis Subunit Vaccine Formulations and the Polarizing Effect of Adjuvants

An in vitro porcine bone marrow-derived dendritic cell (DC) culture was developed as a model for evaluating immune polarization induced by adjuvants when administered with immunogens that may become vaccine candidates if appropriately formulated. The swine pathogen Streptococcus suis was chosen as a prototype to evaluate proposed S. suis vaccine candidates in combination with the adjuvants Poly I:C, Quil A ®, Alhydrogel ®, TiterMax Gold ® and Stimune ®. The toll-like receptor ligand Poly I:C and the saponin Quil A ® polarized swine DC cytokines towards a type 1 phenotype, with preferential production of IL-12 and TNF-α. The water-in-oil adjuvants TiterMax Gold ® and Stimune ® favoured a type 2 profile as suggested by a marked IL-6 release. In contrast, Alhydrogel ® induced a type 1/type 2 mixed cytokine profile. The antigen type differently modified the magnitude of the adjuvant effect, but overall polarization was preserved. This is the first comparative report on swine DC immune activation by different adjuvants. Although further swine immunization studies would be required to better characterize the induced responses, the herein proposed in vitro model is a promising approach that helps assessing behaviour of the vaccine formulation rapidly at the pre-screening stage and will certainly reduce numbers of animals used while advancing vaccinology science.

Construction and Immunological Evaluation of CpG-Au@HBc Virus-Like Nanoparticles as a Potential Vaccine

Different types of vaccines have been developed to elicit active immunization to treat various diseases, while suffer from limitation of efficacy. Herein, a novel immunostimulatory nanocomposite (CpG-Au@HBc VLP) was rationally designed by self-assembling engineered virus-like particles encapsulating CpG-gold nanoparticle conjugates through electrostatic interactions. The monodispersed and uniformly sized CpG-Au@HBc VLP showed increased CD4(+), CD8(+) T cell numbers and stronger secretion of cytokine interferon-gamma than HBc VLPs adjuvanted with conventional Freund's adjuvant. Furthermore, the use of Au nanoparticles also generated enhanced immunogenicity of CpG and VLPs on both humoral and cellular immune pathways, as followed from increased expressions of total HBc-specific antibody titer, CD4(+) T cells, CD8(+) T cells, cytokine interleukin-4, and interferon-gamma. These findings demonstrated that CpG-Au@HBc VLP nanocomposite could induce robust cellular and humoral immune response, which could be a potential vaccine for future prophylactic and therapeutic application.

The next-generation nicotine vaccine: a novel and potent hybrid nanoparticle-based nicotine vaccine

Owing to the urgent need for more effective treatment against nicotine addiction, a hybrid nanoparticle-based nicotine vaccine (NanoNiccine) was developed in this study. NanoNiccine was composed of a poly(lactide-co-glycolide) acid (PLGA) core, keyhole limpet hemocyanin (KLH) as an adjuvant protein enclosed within the PLGA core, a lipid layer, and nicotine haptens conjugated to the outer surface of the lipid layer. In contrast to the traditional nicotine vaccine, NanoNiccine is not a nicotine-protein conjugate vaccine. Instead, the nicotine hapten and protein are separately located in the nanostructure to minimize antibody production towards KLH. The cellular uptake study demonstrated that NanoNiccine was ideal for internalization and processing by dendritic cells (DCs). Mice immunized with NanoNiccine produced much lower IgG level against KLH as compared to that immunized with the traditional nicotine-KLH (Nic-KLH) vaccine. In addition, NanoNiccine achieved up to a 400% higher titer of anti-nicotine IgG than the positive control, Nic-KLH. Additionally, the Th1/Th2 index of NanoNiccine suggested that the immune response induced by NanoNiccine was antibody response dominant. Furthermore, NanoNiccine was found to be safe in mice.

Cytotoxic T cell responses are enhanced by antigen design involving the presentation of MUC1 peptide on cholera toxin B subunit

Induction of cytotoxic T lymphocytes (CTL) is critical to cancer vaccine based immunotherapy. Efforts to elicit CTLs against tumor MUC1 with peptide based vaccine have not been successful in clinical application. We have design a MUC1 vaccine by replacing B cell epitope of CTB with MUC1 VNTR peptide. Immunization with hybrid CTB-MUC1 plus aluminum hydroxide and CpG adujuvant (CTB-MUC1-Alum-CpG) induce MUC1-specific CTLs in mice. Moreover, this vaccination can prevent tumor growth and reduce tumor burden in MUC1⁺B16 mice model. Meanwhile, CTB-MUC1-Alum-CpG vaccination can promote Th1 cells and CD8+ T cells inflate to tumor tissue. Our approach might be applicable to other cancer vaccine design.

A critical role of T follicular helper cells in human mucosal anti-influenza response that can be enhanced by immunological adjuvant CpG-DNA

T Follicular helper cells (TFH) are considered critical for B cell antibody response, and recent efforts have focused on promoting TFH in order to enhance vaccine efficacy. We studied the frequency and function of TFH in nasopharynx-associated lymphoid tissues (NALT) from children and adults, and its role in anti-influenza antibody response following stimulation by a live-attenuated influenza vaccine (LAIV) or an inactivated seasonal virus antigen (sH1N1). We further studied whether CpG-DNA promotes TFH and by which enhances anti-influenza response. We showed NALT from children aged 1.5-10 years contained abundant TFH, suggesting efficient priming of TFH during early childhood. Stimulation by LAIV induced a marked increase in TFH that correlated with a strong production of anti-hemagglutinin (HA) IgA/IgG/IgM antibodies in tonsillar cells. Stimulation by the inactivated sH1N1 antigen induced a small increase in TFH which was markedly enhanced by CpG-DNA, accompanied by enhanced anti-HA antibody responses. In B cell co-culture experiment, anti-HA responses were only seen in the presence of TFH, and addition of plasmacytoid dendritic cell to TFH-B cell co-culture enhanced the TFH-mediated antibody production following CpG-DNA and sH1N1 antigen stimulation. Induction of TFH differentiation from naïve T cells was also shown following the stimulation. Our results support a critical role of TFH in human mucosal anti-influenza antibody response. Use of an adjuvant such as CpG-DNA that has the capacity to promote TFH by which to enhance antigen-induced antibody responses in NALT tissue may have important implications for future vaccination strategies against respiratory pathogens.

Synthetic innate defense regulator peptide combination using CpG ODN as a novel adjuvant induces long‑lasting and balanced immune responses

Vaccines are critical tools for the prevention and treatment of several diseases. Adjuvants have been traditionally used to enhance immunity to vaccines and experimental antigens. In the present study, the adjuvant combination of CpG oligodeoxynucleotides (CpG ODN) and the innate defense regulator (IDR) peptide, IDR‑HH2, was evaluated for its ability to enhance and modulate the immune response when formulated with alum and the recombinant hepatitis B surface antigen (HBsAg). The CpG‑HH2 complex enhanced the secretions of tumor necrosis factor‑α, monocyte chemotactic protein 1 and interferon‑γ by human peripheral blood mononuclear cells and promoted murine bone marrow dentritic cell maturation. In addition, the present study demonstrated that IDR‑HH2 was chemotactic for human neutrophils, THP‑1 cells and RAW264.7 cells at concentrations between 2.5 and 40 µg/ml. The present study also observed that significantly higher anti‑HBs antibody titers, which were sustained at high levels for as long as 35 weeks following the boost immunization, were induced by the combination adjuvant, even when co‑administered with a commercial hepatitis B vaccine at a low antigen dose (0.1 µg HBsAg). Notably, the level of IgG2a was almost equal to the level of IgG1, indicating that a balanced T helper (Th)1/Th2 immune response was elicited by the novel vaccine, which was consistent with the ELISpot results. These data suggest that the CpG‑HH2 complex may be a potential effective adjuvant, which facilitates a reduction in the dose of antigen and induces long‑lasting, balanced immune responses.

Modulatory effect of CpG oligodeoxynucleotide on a DNA vaccine against nervous necrosis virus in orange-spotted grouper (Epinephelus coioides)

We report the development of a DNA vaccine pcMGNNV2 against nervous necrosis virus (NNV), a leading cause of mass mortality in grouper larvae. In addition, the modulatory effect of CpG oligodeoxynucleotide (ODN), a Toll-like receptor 9 agonist, on the DNA vaccine was evaluated. The DNA vaccine alone elicited the production of NNV-specific antibodies, indicating that the vaccine was capable of triggering adaptive humoral response. Furthermore, significant induction of TLR9, Mx and IL-1β was observed in the spleen on day 7 post-vaccination, supporting that the vaccine could trigger TLR9 signaling. The incorporation of CpG ODN at high dose did not significantly affect the level of NNV-specific antibodies, but was able to moderately enhance the expression of Mx and IL-1β on day 7, indicating its ability in modulating innate response. After challenge with NNV, the vaccine alone enhanced the survival rate in infected larvae at both 1 and 2 weeks post-vaccination. The combination of CpG ODN further increased the survival rate at week 1 but not week 2. Interestingly, at week 2 the ODN appeared to induce a Th1-like response, as indicated by upregulation of T-bet (a Th1 marker) and downregulation of GATA-3 (a Th2 marker). Thus, the results suggest that the boosted Th1 response by CpG ODN does not augment the protection efficacy of pcMGNNV2 vaccine. To our best knowledge, this is the first report of a successful DNA vaccine against NNV in grouper.

CpG-ODN Class C Mediated Immunostimulation in Rabbit Model of Trypanosoma evansi Infection

CpG oligodeoxynucleotides (CpG-ODN) stimulate immune cells from a wide spectrum of mammalian species. Class C CpG-ODN is relatively stable and has the combined immune effects of both A and B classes of CpG-ODN. Trypanosoma evansi produces the state of immuno-suppression in the infected hosts. The current chemotherapeutic agents against this parasite are limited in number and usually associated with severe side effects. The present work aimed to determine the immunostimulatory effects of CpG-ODN class C in T. evansi infected rabbits. Rabbits inoculated with CpG C and challenged with T. evansi resulted in delayed onset of clinical signs with reduced severity in comparison to that of T. evansi infected rabbits. The treatment also enhanced humoral immune responses. Histopathological findings in liver and spleen revealed enhancement of mononuclear cell infiltration and secondary B cell follicles. These results demonstrate that CpG-ODN class C, has immunostimulatory properties in rabbit model of trypanosomosis. The use of booster doses or sustained delivery of CpG-ODN will further elucidate the prolonged CpG-ODN generated immune responses.

Non-clinical safety evaluation of repeated intramuscular administration of the AS15 immunostimulant combined with various antigens in rabbits and cynomolgus monkeys

Combination of tumor antigens with immunostimulants is a promising approach in cancer immunotherapy. We assessed animal model toxicity of AS15 combined with various tumor antigens: WT1 (rabbits), or p501, dHER2 and recPRAME (cynomolgus monkeys), administered in seven or 20 dose regimens versus a saline control. Clinical and ophthalmological examinations, followed by extensive post‐mortem pathological examinations, were performed on all animals. Blood hematology and biochemistry parameters were also assessed. Antigen‐specific antibody titers were determined by enzyme‐linked immunosorbent assay. Additional assessments in monkeys included electrocardiography and immunohistochemical evaluations of the p501 expression pattern. Transient increases in body temperature were observed 4 h or 24 h after injections of recPRAME + AS15 and dHER2 + AS15. Edema and erythema were observed up to 1 week after most injections of recPRAME + AS15 and all injections of dHER2 + AS15. No treatment‐related effects were observed for electrocardiography parameters. Mean fibrinogen levels were significantly higher in all treated groups compared to controls, but no differences could be observed at the end of the treatment‐free period. Transient but significant differences in biochemistry parameters were observed post‐injection: lower albumin/globulin ratios (p501 + AS15), and higher bilirubin, urea and creatinine (dHER2 + AS15). Pathology examinations revealed significant increases in axillary lymph node mean weights (recPRAME + AS15) compared to controls. A 100% seroconversion rate was observed in all treated groups, but not in controls. p501 protein expression was observed in prostates of all monkeys from studies assessing p501 + AS15. These results suggest a favorable safety profile of the AS15‐containing candidate vaccines, supporting the use of AS15 for clinical development of potential anticancer vaccines. Copyright © 2015 The Authors. Journal of Applied Toxicology Published by John Wiley & Sons Ltd.

The aim of the current paper was to assess the safety profile of vaccine candidates containing the AS15 immunostimulant combined with different antigens in two animal models. Several antigens were tested for this purpose: WT1 (rabbits), p501, dHER2 and recPRAME (cynomolgus monkeys). Only transient differences in hematology and biochemical parameters could be observed, while pathology testing revealed no safety concerns. Our findings support the use of AS15 for clinical development of potential immunotherapeutic cancer vaccines.

Design and Structural Requirements of the Potent and Safe TLR-9 Agonistic Immunomodulator MGN1703

Single-stranded oligodeoxynucleotides (ODN), containing nonmethylated cytosine–guanine motifs (CpG ODN), are recognized by the innate immune system as “danger signals.” CpG ODN are efficacious immunomodulators but require phosphorothioate (PT) or other backbone modifications for metabolic stability, which cause toxicities in mice and primates. We therefore designed a covalently closed DNA molecule (dSLIM^®) where two single-stranded loops containing CG motifs are connected through a double-stranded stem in the absence of any nonnatural DNA component. The most promising immunomodulator, MGN1703, comprises two loops of 30 nucleotides containing three CG motifs each, and a connecting stem stem of 28 base pairs. MGN1703 stimulates cytokine secretion [interferon (IFN)-α, IFN-γ, interleukin (IL)-12, IL-6, and IL-2] and activates immune cells by increased expression of CD80, CD40, human leukocyte antigen (HLA)-DR and ICAM-1. Efficacy of immunomodulation strictly depends on the descriptive dumbbell shape and size of the molecule. Variations in stem length and loop size lead to reduced potency of the respective members of the dSLIM^® class. In a representative mouse model, toxicities from injections of high amounts of a CpG ODN-PT and of MGN1703 were evaluated. The CpG ODN-PT group showed severe organ damage, whereas no such or other pathologies were found in the MGN1703 group. Oncological clinical trials of MGN1703 already confirmed our design.

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).

TLR9 and STING agonists synergistically induce innate and adaptive type-II IFN

Agonists for TLR9 and Stimulator of IFN Gene (STING) act as vaccine adjuvants that induce type-1 immune responses. However, currently available CpG oligodeoxynucleotide (ODN) (K-type) induces IFNs only weakly and STING ligands rather induce type-2 immune responses, limiting their potential therapeutic applications. Here, we show a potent synergism between TLR9 and STING agonists. Together, they make an effective type-1 adjuvant and an anticancer agent. The synergistic effect between CpG ODN (K3) and STING-ligand cyclic GMP-AMP (cGAMP), culminating in NK cell IFN-γ (type-II IFN) production, is due to the concurrent effects of IL-12 and type-I IFNs, which are differentially regulated by IRF3/7, STING, and MyD88. The combination of CpG ODN with cGAMP is a potent type-1 adjuvant, capable of inducing strong Th 1-type responses, as demonstrated by enhanced antigen-specific IgG2c and IFN-γ production, as well as cytotoxic CD8(+) T-cell responses. In our murine tumor models, intratumoral injection of CpG ODN and cGAMP together reduced tumor size significantly compared with the singular treatments, acting as an antigen-free anticancer agent. Thus, the combination of CpG ODN and a STING ligand may offer therapeutic application as a potent type-II IFN inducer.

Immune responses associated with homologous protection conferred by commercial vaccines for control of avian pathogenic Escherichia coli in turkeys

Avian pathogenic Escherichia coli (APEC) infections are a serious impediment to sustainable poultry production worldwide. Licensed vaccines are available, but the immunological basis of protection is ill-defined and a need exists to extend cross-serotype efficacy. Here, we analysed innate and adaptive responses induced by commercial vaccines in turkeys. Both a live-attenuated APEC O78 ΔaroA vaccine (Poulvac® E. coli) and a formalin-inactivated APEC O78 bacterin conferred significant protection against homologous intra-airsac challenge in a model of acute colibacillosis. Analysis of expression levels of signature cytokine mRNAs indicated that both vaccines induced a predominantly Th2 response in the spleen. Both vaccines resulted in increased levels of serum O78-specific IgY detected by ELISA and significant splenocyte recall responses to soluble APEC antigens at post-vaccination and post-challenge periods. Supplementing a non-adjuvanted inactivated vaccine with Th2-biasing (Titermax® Gold or aluminium hydroxide) or Th1-biasing (CASAC or CpG motifs) adjuvants, suggested that Th2-biasing adjuvants may give more protection. However, all adjuvants tested augmented humoral responses and protection relative to controls. Our data highlight the importance of both cell-mediated and antibody responses in APEC vaccine-mediated protection toward the control of a key avian endemic disease.

Potentiation of antigen-specific antibody production by peptides derived from Ag85B of Mycobacterium tuberculosis

To generate high-titer monoclonal antibodies, strong immuno-stimulation must be used for eliciting an intense cellular immune response. Here, we report that antigen-specific antibody production was potentiated by Peptide-25 derived from Ag85B of Mycobacterium tuberculosis, and that the production of antigen-specific IgG1 in particular was markedly potentiated; specifically, this occurred because the use of Peptide-25 resulted in an increase in the number of antigen-specific antibody-producing cells. We studied the activation of T cells by the peptide by examining gene expression. The observed expression pattern of GATA-3 and T-bet suggests that the peptide modulates the Th1/Th2 balance during immunization. This potentiation, which was remarkably high in BALB/c mice, could be applied in the immunization performed for monoclonal antibody production in vivo and in vitro.

Mechanistic insight into the TH1-biased immune response to recombinant subunit vaccines delivered by probiotic bacteria-derived outer membrane vesicles

Recombinant subunit vaccine engineering increasingly focuses on the development of more effective delivery platforms. However, current recombinant vaccines fail to sufficiently stimulate protective adaptive immunity against a wide range of pathogens while remaining a cost effective solution to global health challenges. Taking an unorthodox approach to this fundamental immunological challenge, we isolated the TLR-targeting capability of the probiotic E. coli Nissle 1917 bacteria (EcN) by engineering bionanoparticlate antigen carriers derived from EcN outer membrane vesicles (OMVs). Exogenous model antigens expressed by these modified bacteria as protein fusions with the bacterial enterotoxin ClyA resulted in their display on the surface of the carrier OMVs. Vaccination with the engineered EcN OMVs in a BALB/c mouse model, and subsequent mechanism of action analysis, established the EcN OMV’s ability to induce self-adjuvanted robust and protective humoral and T_H1-biased cellular immunity to model antigens. This finding appears to be strain-dependent, as OMV antigen carriers similarly engineered from a standard K12 E. coli strain derivative failed to generate a comparably robust antigen-specific T_H1 bias. The results demonstrate that unlike traditional subunit vaccines, these biomolecularly engineered “pathogen-like particles” derived from traditionally overlooked, naturally potent immunomodulators have the potential to effectively couple recombinant antigens with meaningful immunity in a broadly applicable fashion.

Development of CpG-oligodeoxynucleotides for effective activation of rabbit TLR9 mediated immune responses

CpG-oligodeoxynucleotides (CpG-ODN) are potent immune stimuli being developed for use as adjuvants in different species. Toll-like receptor 9 (TLR9) is the cellular receptor for CpG-ODN in mammalian cells. The CpG-ODN with 18–24 deoxynucleotides that are in current use for human and mouse cells, however, have low activity with rabbit TLR9. Using a cell-based activation assay, we developed a type of CpG-ODN containing a GACGTT or AACGTT motif in 12 phosphorothioate-modified deoxynucleotides with potent stimulatory activity for rabbit TLR9. The developed CpG-ODN have higher activities than other developed CpG-ODN in eliciting antigen-nonspecific immune responses in rabbit splenocytes. When mixed with an NJ85 peptide derived from rabbit hemorrhagic disease virus, they had potent activities to boost an antigen-specific T cell activation and antibody production in rabbits. Compared to Freund’s adjuvant, the developed CpG-ODN are capable of boosting a potent and less toxic antibody response. The results of this study suggest that both the choice of CpG-motif and its length are important factors for CpG-ODN to effectively activate rabbit TLR9 mediated immune responses.

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.

Nucleic acid-mediated intracellular protein delivery by lipid-like nanoparticles

Intracellular protein delivery has potential biotechnological and therapeutic application, but remains technically challenging. In contrast, a plethora of nucleic acid carriers have been developed, with lipid-based nanoparticles (LNPs) among the most clinically advanced reagents for oligonucleotide delivery. Here, we validate the hypothesis that oligonucleotides can serve as packaging materials to facilitate protein entrapment within and intracellular delivery by LNPs. Using two distinct model proteins, horseradish peroxidase and NeutrAvidin, we demonstrate that LNPs can yield efficient intracellular protein delivery in vitro when one or more oligonucleotides have been conjugated to the protein cargo. Moreover, in experiments with NeutrAvidin in vivo, we show that oligonucleotide conjugation significantly enhances LNP-mediated protein uptake within various spleen cell populations, suggesting that this approach may be particularly suitable for improved delivery of protein-based vaccines to antigen-presenting cells.