Stimulation of innate immune responses by CpG oligodeoxynucleotide in newborn lambs can reduce bovine herpesvirus-1 shedding

Adjuvants: What a Difference 15 Years Makes!

Vaccination is a critical tool in modern animal production and key to maintaining animal health. Adjuvants affect the immune response by increasing the rate, quantity, or quality of the protective response generated by the target antigens. Although adjuvant technology dates back to the nineteenth century, there was relatively little improvement in adjuvant technology before the late twentieth century. With the discovery of molecular pathways that regulate the timing, quantity, and quality of the immune response, new technologies are focused on bringing safer, more effective, and inexpensive adjuvants to commercial use.

The effect of the TLR9 ligand CpG-oligodeoxynucleotide on the protective immune response to alcelaphine herpesvirus-1-mediated malignant catarrhal fever in cattle

We wished to determine the effect of of CpG ODN adjuvant on the magnitude and duration of protective immunity against alcelaphine herpesvirus-1 (AlHV-1) malignant catarrhal fever (MCF), a fatal lymphoproliferative disease of cattle. Immunity was associated with a mucosal barrier of virus-neutralising antibody. The results showed that CpG ODN included either with emulsigen adjuvant and attenuated AlHV-1 (atAlHV-1) or alone with atAlHV-1 did not affect the overall protection from clinical disease or duration of immunity achieved using emulsigen and atAlHV-1. This is in contrast to other similar studies in cattle with BoHV-1 or cattle and pigs with various other immunogens. In addition to this, several other novel observations were made, not reported previously. Firstly, we were able to statistically verify that vaccine protection against MCF was associated with virus-neutralising antibodies (nAbs) in nasal secretions but was not associated with antibodies in blood plasma, nor with total virus-specific antibody (tAb) titres in either nasal secretions or blood plasma. Furthermore, CpG ODN alone as adjuvant did not support the generation of virus-neutralising antibodies. Secondly, there was a significant boost in tAb in animals with MCF comparing titres before and after challenge. This was not seen with protected animals. Finally, there was a strong IFN-γ response in animals with emulsigen and atAlHV-1 immunisation, as measured by IFN-γ secreting PBMC in culture (and a lack of IL-4) that was not affected by the inclusion of CpG ODN. This suggests that nAbs at the oro-nasal-pharyngeal region are important in protection against AlHV-1 MCF.

Immunotherapeutic potential of CpG oligodeoxynucleotides in veterinary species

Innate immunity plays a critical role in host defense against infectious diseases by discriminating between self and infectious non-self. The recognition of infectious non-self involves germ-line encoded pattern recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs). The PAMPs are the components of pathogenic microbes which include not only the cell wall constituents but also the unmethylated 2'-deoxy-ribo-cytosine-phosphate-guanosine (CpG) motifs. These CpG motifs present within bacterial and viral DNA are recognized by toll-like receptor 9 (TLR9), and signaling by this receptor triggers a proinflammatory cytokine response which, in turn, influences both innate and adaptive immune responses. The activation of TLR9 with synthetic CpG oligodeoxynucleotides (ODNs) induces powerful Th1-like immune responses. It has been shown to provide protection against infectious diseases, allergy and cancer in laboratory animal models and some domestic animal species. With better understanding of the basic biology and immune mechanisms, it would be possible to exploit the potential of CpG motifs for animal welfare. The research developments in the area of CpG and TLR9 and the potential applications in animal health have been reviewed in this article.

Stimulation with a class A CpG oligonucleotide enhances resistance to infection with feline viruses from five different families

Domestic cats are commonly affected by viral pathogens that induce lengthy infections with fatal outcomes. Prevention of viral propagation is of primordial importance in shelters and catteries, where cats from different backgrounds have narrow contacts. Oligonucleotides (ODN) containing cytosine-phosphate-guanosine motifs of class A (CpG-A) are highly potent synthetic inducers of innate antiviral mechanisms. The aim of this study was to test their ability to modulate innate immune responses and prevent viral replication as stand-alone agents in the domestic cat. CpG-A stimulation of feline peripheral blood mononuclear cells (PBMCs) enhanced their proliferation, increased the presence of co-stimulatory molecules on their surface and influenced their gene expression profiles in an antiviral orientation. Incubation of the supernatants of CpG-A stimulated PBMCs with feline cell lines of epithelial and fibroblastic origin induced expression of the antiviral myxovirus resistance (Mx) gene in these target cells, which also showed enhanced resistance to feline viruses from five distinct families, namely Coronaviridae, Herpesviridae, Caliciviridae, Parvoviridae, and Retroviridae. Most importantly, subcutaneous administration of CpG-A in domestic cats systemically increased the expression of Mx, reaching maximal levels within 24 h. Plasma from treated cats could furthermore inhibit viral replication in vitro. Altogether, our data highlight the promising potential of CpG-A to induce a preventive antiviral state in the cat and to protect feline populations against a broad range of virus infections.

Identification of a lineage negative cell population in bovine peripheral blood with the ability to mount a strong type I interferon response

Lineage negative dendritic cells, or natural interferon-producing cells (NIPC), also referred to as plasmacytoid dendritic cells (pDC) constitute a small population of leukocytes secreting high levels of type I interferon (IFNα/β) in response to certain danger signals. Here, we provide initial data towards the identification of so far uncharacterised circulating bovine pDC like cells. A lineage negative cell population (LIN(-) cells) was isolated from PBMC which showed characteristics similar to that of pDC in other species. Isolated LIN(-) cells presented lymphoid morphology with a semi-crescent nucleus, extensive ER and Golgi network; indicative of pDC. In addition phenotypic analysis of LIN(-) cells described them as distinct from other bovine DC subsets; expressing both lymphoid and myeloid surface markers. LIN(-) cells did not express lineage specific markers, but were MHC class II(+), CD45RO(+), CD80/86(+), CD6(+), WC1(+), CD26(+) and expressed the myeloid markers CD205, CD172a and CD11a. In keeping with pDC, LIN(-) cells express TLR7 mRNA transcripts; however, in a resting state do not express TLR8 or TLR9. Functionally, LIN(-) cells, but not PBMC, monocytes and monocyte derived DC produce large amounts of IFNα/β in response to different CpG oligonucleotides. Taken together, we present data suggesting that an enriched circulating population of bovine LIN(-) cells are uniquely capable of producing IFNα/β in response to CpG oligonucleotides and thus this population likely contain the functional equivalent of bovine pDC.

TLR9 agonists: immune mechanisms and therapeutic potential in domestic animals

Toll like receptors (TLRs) are transmembrane glycoproteins that recognize conserved microbial molecules. Engagement of TLRs activates innate and adaptive immunity. TLR-mediated activation of immune cells results in upregulation of cytokines, chemokines and costimulatory molecules. These early innate responses control pathogen spread and initiates adaptive immune responses. Synthetic CpG oligodeoxynucleotides (ODN), agonists for TLR9, had shown great promise as immunotherapeutic agents and vaccine adjuvants in laboratory animal models of infectious disease, allergy and cancer. However, it has become apparent that CpG ODN are less potent immune activators in domestic animals and humans. The disparity in immune responses between rodents and mammals has been mainly attributed to differences in cellular expression of TLR9 in the various species. In this article, our current understanding of the immune mechanisms, as well as the potential applications of CpG ODN will be reviewed, with particular emphasis on domestic animals.

Mesenteric lymph node cells from neonates present a prominent IL-12 response to CpG oligodeoxynucleotide via an IL-15 feedback loop of amplification

At birth, the immune system is still in development making neonates more susceptible to infections. The recognition of microbial ligands is a key step in the initiation of immune responses. It can be mimicked to stimulate the immune system by the use of synthetic ligands recognising pattern recognition receptors. In human and mouse, it has been found that neonatal cytokine responses to toll-like receptor (TLR) ligands differ in many ways from those of adults but the relevant studies have been limited to cord blood and spleen cells. In this study, we compared the responses in neonate and adult sheep to CpG oligodeoxynucleotides (ODN), a TLR9 ligand, in both a mucosal and a systemic organ. We observed that in response to CpG-ODN more IL-12 was produced by neonatal than adult sheep cells from mesenteric lymph nodes (MLN) and spleen. This higher IL-12 response was limited to the first 20 days after birth for MLN cells but persisted for a longer period for spleen cells. The major IL-12-producing cells were identified as CD14⁺CD11b⁺. These cells were poor producers of IL-12 in response to direct stimulation with CpG-ODN and required the cooperation of other MLN cells. The difference in response to CpG-ODN between neonates and adults can be attributed to both a higher proportion of CD14⁺CD11b⁺ cells in neonate lambs and their higher capacity to produce IL-15. The IL-15 increases IL-12 production by an amplifying feedback loop involving CD40.

CpG oligodeoxynucleotide promotes protective immunity in the enteric mucosa and suppresses enterotoxigenic E. coli in the weaning piglets

CpG oligodeoxynucleotide (CpG ODN) has been described as an effective activator of the innate immune system, with potential to protect against infection caused by a range of pathogens in a non-specific manner. We therefore investigated if intranasal (IN), oral (OR)-mucosal, and intramuscular (IM)-systemic administrations of CpG ODN without antigen codelivery could all enhance innate immunity in the enteric mucosa and control the extent of enterotoxigenic Escherichia coli (ETEC) infection in weaning piglets. Here our data showed that CpG ODN dosed by IN, OR or IM routes protected weaning piglets against a subsequent challenge with ETEC. The level of protection was greater when CpG ODN was administered IN and OR than IM, demonstrating a clear relationship between the route of CpG dosing and protection. IN and OR treatments with CpG ODN reduced bacterial load in the phases at days 3-5 post challenge. The CXC chemokine (CXCL10 and CXCL11) and CC chemokine (CCL4 and CCL5) mRNA expressions were elevated in the intestinal tissues from animals treated IN or OR with CpG ODN compared to untreated controls. Significantly enhanced mRNA expressions for cathelicidins (PR-39 and protegrin-1), but moderately for β-defensin (pBD1 and pBD2), were observed in IN or OR CpG-treatments. Also, significant production of cytokines (IL-12, IFN-γ, and MCP-1) and F4-specific antibodies (IgG/IgA) was detected in intestinal washings following IN and OR CpG-treatments. In contrast, IM delivery induced marked production of sera F4-specific antibodies. It was possible that these chemokines, cytokines, cathelicidins and antibodies played a role in the clearance of ETEC. These findings suggested that IN or OR administration of CpG ODN without antigen codelivery might represent a valuable strategy for induction of innate immunity against ETEC infection.

Subcutaneous, but not intratracheal administration of the TLR9 agonist, CpG DNA transiently reduces parainfluenza-3 virus shedding in newborn lambs

Synthetic oligodeoxynucleotides (ODN) containing CpG motifs signal through TLR9 and activate innate immunity resulting in protection against a variety of parasitic, bacterial and viral pathogens in mouse models. However, few studies have demonstrated protection in humans and large animals. In the present investigations, we evaluated protection by CpG ODN in a parainfluenza-3 (PI-3) virus infection in neonatal lambs. Subcutaneous (SC) injection of CpG ODN induced high levels of 2'5'-A synthetase and significantly reduced PI-3 virus shedding in newborn lambs. Furthermore, pre-treatment of newborn lambs with SC CpG ODN 2 days, but not 6 days prior to the virus challenge was protective. In contrast, intratracheal (IT) administration of CpG ODN induced 2'5'-A synthetase but had no significant impact on PI-3 virus shedding in nasal secretions. We conclude that a systemic administration of CpG ODN and the timing of the treatment are critical for the protection of neonatal lambs against a respiratory viral infection.

All three classes of CpG ODNs up-regulate IP-10 gene in pigs

The analysis of CpG ODN induced innate immune responses in different animal species has shown substantial similarities and differences in levels and types of induced cytokines profile. The objectives of these studies were to identify innate immune biomarkers activated by three classes of CpG ODNs in pigs. For this purpose, we investigated the kinetics of innate immune responses in immune cells from pigs following in vitro and in vivo stimulation with CpG ODNs. The mRNA expression of cytokine and chemokine genes were assayed by SYBR green based quantitative real time PCR. A-class CpG ODN induced significant but transient levels of IFN-gamma, IL-12 (P40), IL-6, IL-4 and TNF-alpha mRNA, C-class CpG ODN induced significant level of IFN-gamma, IFN-alpha and IL-12 mRNA and the lowest level of IL-4 (Th-2 type) mRNA. A very low level of some cytokines stimulation was observed by GC ODNs. It is noteworthy, that IL-12 (P35) mRNA was significantly stimulated by B-class GpC ODN 7909. Interestingly, all classes of CpG ODNs induced significant level of IP-10 at 12h post stimulation. These in vitro and in vivo observations suggest that interferon-gamma inducible protein 10 (IP-10) may be a reliable biomarker for immune activity induced by CpG ODNs in pigs.

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.

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.

Strategies to link innate and adaptive immunity when designing vaccine adjuvants

Adjuvants are important components of vaccine formulations. Their functions include the delivery of antigen, recruitment of specific immune cells to the site of immunization, activation of these cells to create an inflammatory microenvironment, and maturation of antigen-presenting cells for enhancement of antigen-uptake and -presentation in secondary lymphoid tissues. Adjuvants include a large family of molecules and substances, many of which were developed empirically and without knowledge of their specific mechanisms of action. The discovery of pattern recognition receptors including Toll-like-, nucleotide-binding oligomerization domain (NOD)- and mannose-receptors, has significantly advanced the field of adjuvant research. It is now clear that effective adjuvants link innate and adaptive immunity by signaling through a combination of pathogen recognition receptors (PRRs). Research in our lab is focused towards the development of novel adjuvants and immunomodulators that can be used to improve neonatal vaccines for humans and animals. Using a neonatal pig model for pertussis, we are currently analyzing the effectiveness of host defence peptides (HDPs), bacterial DNA and polyphosphazenes as vaccine adjuvants.

Plasmacytoid dendritic cells migrate in afferent skin lymph

Conventional dendritic cells enter lymph nodes by migrating from peripheral tissues via the lymphatic route, whereas plasmacytoid dendritic cells (pDC), also called IFN-producing cells (IPC), are described to gain nodes from blood via the high endothelial venules. We demonstrate here that IPC/pDC migrate in the afferent lymph of two large mammals. In sheep, injection of type A CpG oligodinucleotide (ODN) induced lymph cells to produce type I IFN. Furthermore, low-density lymph cells collected at steady state produced type I IFN after stimulation with type A CpG ODN and enveloped viruses. Sheep lymph IPC were found within a minor B(neg)CD11c(neg) subset expressing CD45RB. They presented a plasmacytoid morphology, expressed high levels of TLR-7, TLR-9, and IFN regulatory factor 7 mRNA, induced IFN-gamma production in allogeneic CD4(pos) T cells, and differentiated into dendritic cell-like cells under viral stimulation, thus fulfilling criteria of bona fide pDC. In mini-pig, a CD4(pos)SIRP(pos) subset in afferent lymph cells, corresponding to pDC homologs, produced type I IFN after type A CpG-ODN triggering. Thus, pDC can link innate and acquired immunity by migrating from tissue to draining node via lymph, similarly to conventional dendritic cells.

Neonatal goats display a stronger TH1-type cytokine response to TLR ligands than adults

In mammals, Toll-like receptors play a critical role in initiating innate immune responses and modulating adaptive immunity, by recognizing conserved microbial molecular patterns. This study was undertaken to identify specific features of the responses to synthetic toll-like receptor (TLR) agonists in goats, for the definition of tailored immunostimulation strategies. We show here, in contrast to what has been shown in mice, that mesenteric lymph nodes (MLNs) cells and splenocytes from neonatal goats produce much higher levels of TH1-type cytokines than adults in response to various TLR agonists. IL-12 was identified as a critical cytokine for IFNgamma production by CD8(+) neonatal cells. The higher level of IL-12 production by neonatal MLN and spleen cells than by adult cells was not correlated with a higher level of TLR expression or lower levels of production of the regulatory cytokine IL-10. In neonates, two cell populations-class II(+) CD8(+) and class II(+) CD8(-) cells-produce IL-12 in response to R848 and Poly I:C, respectively. Thus, goat kids have characteristics that could be exploited to favor development of the TH1-type responses critical for the control of intracellular pathogens.

Therapeutic applications of synthetic CpG oligodeoxynucleotides as TLR9 agonists for immune modulation

Vertebrate toll-like receptors (TLRs) sense invading pathogens by recognizing bacterial and viral structures and, as a result, activate innate and adaptive immune responses. Ten human functional TLRs have been reported so far; three of these (TLR7, 8, and 9) are expressed in intracellular compartments and respond to single-stranded nucleic acids as natural ligands. The pathogen structure selectively recognized by TLR9 in bacterial or viral DNA was identified to be CpG dinucleotides in specific sequence contexts (CpG motifs). Short phosphorothioate-stabilized oligodeoxynucleotides (ODNs) containing such motifs are used as synthetic TLR9 agonists, and different classes of ODN TLR9 agonists have been identified with distinct immune modulatory profiles. The TLR9-mediated activation of the vertebrate immune system suggests using such TLR9 agonists as effective vaccine adjuvants for infectious disease, and for the treatment of cancer and asthma/allergy. Immune activation by CpG ODNs has been demonstrated to be beneficial in animal models as a vaccine adjuvant and for the treatment of a variety of viral, bacterial, and parasitic diseases. Antitumor activity of CpG ODNs has also been established in numerous mouse models. In clinical vaccine trials in healthy human volunteers or in immunocompromised HIV-infected patients, CpG ODNs strongly enhanced vaccination efficiency. Most encouraging results in the treatment of cancers have come from human phase I and II clinical trials using CpG ODNs as a tumor vaccine adjuvant, monotherapy, or in combination with chemotherapy. Therefore, CpG ODNs represent targeted immune modulatory drugs with a broad range of potential applications.

Protective cancer immunotherapy: what can the innate immune system contribute?

Despite significant efforts to induce protection against malignant diseases, the clinical effects of antitumour vaccines are poor. However, recent studies on a quadrivalent human papilloma virus vaccine suggest that protection against secondary tumour development is feasible. While this scenario benefits rather from antiviral protection than from direct antitumour responses, immunisation against cancers of non-viral origin demands strategies that rely on the circumvention of intrinsic regulatory mechanisms. Strong activation of innate immune cells seems to be key and, thus, the choice of adjuvant determines vaccination efficacy. The recently acquired knowledge about molecular and cellular recognition of microbial molecules suggests how one can modulate innate and adaptive immune reactions to potentially induce robust T- and B-cell reactions capable of prohibiting tumour development and progression. Here, the authors review the present knowledge of innate immune reactions, which may help to define rationales on the design of novel antitumour vaccines.

Antiinfective applications of toll-like receptor 9 agonists

The innate immune system detects pathogens by the presence of highly conserved pathogen-expressed molecules, which trigger host immune defenses. Toll-like receptor (TLR) 9 detects unmethylated CpG dinucleotides in bacterial or viral DNA, and can be stimulated for therapeutic applications with synthetic oligodeoxynucleotides containing immune stimulatory "CpG motifs." TLR9 activation induces both innate and adaptive immunity. The TLR9-induced innate immune activation can be applied in the prevention or treatment of infectious diseases, and the adaptive immune-enhancing effects can be harnessed for improving vaccines. This article highlights the current understanding of the mechanism of action of CpG oligodeoxynucleotides, and provides an overview of the preclinical data and early human clinical trial results, applying these TLR9 agonists in the field of infectious diseases.

The effect of CpG-ODN on antigen presenting cells of the foal

Background

Cytosine-phosphate-guanosine oligodeoxynucleotide (CpG-ODN) has been used successfully to induce immune responses against viral and intracellular organisms in mammals. The main objective of this study was to test the effect of CpG-ODN on antigen presenting cells of young foals.

Methods

Peripheral blood monocytes of foals (n = 7) were isolated in the first day of life and monthly thereafter up to 3 months of life. Adult horse (n = 7) monocytes were isolated and tested once for comparison. Isolated monocytes were stimulated with IL-4 and GM-CSF (to obtain dendritic cells, DC) or not stimulated (to obtain macrophages). Macrophages and DCs were stimulated for 14–16 hours with either CpG-ODN, LPS or not stimulated. The stimulated and non-stimulated cells were tested for cell surface markers (CD86 and MHC class II) using flow cytometry, mRNA expression of cytokines (IL-12, IFNα, IL-10) and TLR-9 using real time quantitative RT-PCR, and for the activation of the transcription factor NF-κB p65 using a chemiluminescence assay.

Results

The median fluorescence of the MHC class II molecule in non-stimulated foal macrophages and DCs at birth were 12.5 times and 11.2 times inferior, respectively, than adult horse cells (p = 0.009). That difference subsided at 3 months of life (p = 0.3). The expression of the CD86 co-stimulatory molecule was comparable in adult horse and foal macrophages and DCs, independent of treatment. CpG-ODN stimulation induced IL-12p40 (53 times) and IFNα (23 times) mRNA expression in CpG-ODN-treated adult horse DCs (p = 0.078), but not macrophages, in comparison to non-stimulated cells. In contrast, foal APCs did not respond to CpG-ODN stimulation with increased cytokine mRNA expression up to 3 months of age. TLR-9 mRNA expression and NF-kB activation (NF-kB p65) in foal DCs and macrophages were comparable (p > 0.05) to adult horse cells.

Conclusion

CpG-ODN treatment did not induce specific maturation and cytokine expression in foal macrophages and DCs. Nevertheless, adult horse DCs, but not macrophages, increased their expression of IL-12 and IFNα cytokines upon CpG-ODN stimulation. Importantly, foals presented an age-dependent limitation in the expression of MHC class II in macrophages and DCs, independent of treatment.

Bovine herpesvirus 1 infection and infectious bovine rhinotracheitis

Bovine herpesvirus 1 (BoHV-1), classified as an alphaherpesvirus, is a major pathogen of cattle. Primary infection is accompanied by various clinical manifestations such as infectious bovine rhinotracheitis, abortion, infectious pustular vulvovaginitis, and systemic infection in neonates. When animals survive, a life-long latent infection is established in nervous sensory ganglia. Several reactivation stimuli can lead to viral re-excretion, which is responsible for the maintenance of BoHV-1 within a cattle herd. This paper focuses on an updated pathogenesis based on a molecular characterization of BoHV-1 and the description of the virus cycle. Special emphasis is accorded to the impact of the latency and reactivation cycle on the epidemiology and the control of BoHV-1. Several European countries have initiated BoHV-1 eradication schemes because of the significant losses incurred by disease and trading restrictions. The vaccines used against BoHV-1 are described in this context where the differentiation of infected from vaccinated animals is of critical importance to achieve BoHV-1 eradication.

Systemic innate immune responses following intrapulmonary delivery of CpG oligodeoxynucleotides in sheep

Mucosal delivery of CpG oligodeoxynucleotide (ODN) in mice has been shown to induce potent innate immunostimulatory responses and protection against infection. We evaluated the efficacy of CpG ODN in stimulating systemic innate immune responses in sheep following delivery to the pulmonary mucosa. Intrapulmonary (IPM) administration of B-Class CpG ODN in saline induced transient systemic responses which included increased rectal temperatures, elevated serum 2'5'-A synthetase and haptoglobin concentrations. The ODN dose required to induce detectable systemic responses following IPM delivery could be reduced by approximately 80% if the CpG ODN was administered in 30% emulsigen instead of saline. Intrapulmonary B-Class CpG ODN formulated in 30% emulsigen produced similar effects when compared to those seen following SC injection. These responses were CpG ODN-specific since control GpC ODN did not induce any detectable response. Intrapulmonary administration of both B-Class and the newly described C-Class CpG ODN produced similar effects indicating that both classes of CpG ODN were comparably effective in stimulating innate immune system following mucosal delivery. Administration of CpG ODN directly into the lungs or delivery of CpG ODN via an intratracheal (IT) infusion also produced similar systemic responses. These observations support the conclusion that mucosal delivery of CpG ODN is an effective route for induction of systemic acute phase responses and antiviral effector molecules in large animals, and may be helpful in controlling systemic infections.

Formulation with CpG ODN enhances antibody responses to an equine influenza virus vaccine

Previous studies have shown that protection against equine influenza virus (EIV) is partially mediated by virus-specific IgGa and IgGb. In this study we tested whether addition of a CpG ODN formulation to a commercial killed virus vaccine would enhance EIV-specific IgGa and IgGb antibody responses, and improve protection against an experimental EIV challenge. Thirty naïve horses were assigned to one of three groups and vaccinated as follows: 10 were given vaccine (Encevac TC4, Intervet Inc.) alone, 10 were given vaccine plus 0.25 mg CpG ODN 2007 formulated with 30% Emulsigen (CpG/Em), and 10 controls were given saline. All horses were challenged with live virus 12 weeks after the final vaccination. Antibody responses were tested by single radial hemolysis (SRH) and ELISA, and protection was evaluated by determination of temperature, coughing, and clinical scores. Killed virus vaccine combined with CpG/Em induced significantly greater serologic responses than did the vaccine alone. All antibody isotypes tested increased after the addition of CpG/Em, although no shift in relative antibody isotypes concentrations was detected. Vaccination significantly improved protection against challenge but the differences between the two vaccine groups were not statistically significant. This study is the first demonstration that CpG/Em enhances antigen-specific antibody responses in horses and supports its potential to be used as an adjuvant for vaccines against equine infections.