Natural and inducible regulatory B cells are widely distributed in ovine lymphoid tissues

Regulatory B cells that produce IL-10 are now recognized as an important component of the immune system. We previously confirmed that IL-10 secreting CD21⁺ regulatory B cells (B_reg cells) were present in ovine jejunal Peyer's patches (JPP) and this IL-10 production suppressed IL-12 and IFN-γ secretion. It is not known, however, whether ovine B_reg cells are restricted to JPP or are present in other lymphoid tissues. Therefore, CD21⁺ B cells were purified from sheep JPP and from a variety of mucosal and systemic lymphoid tissues using magnetic cell sorting. Purified CD21⁺ B cells were stimulated with a TLR9-agonist, CpG oligodeoxynucleotide (CpG ODN), and the frequency of spontaneous and inducible (i) IL-10-secreting B cells was evaluated by ELISPOT. Spontaneous IL-10 secreting CD21⁺ B cells were present in mucosal (jejunal PP, parabronchial lymph nodes (LN), mesesnteric LN, and palatine tonsils) and systemic (spleen and blood) lymphoid tissues. Mucosal lymphoid tissues (parabronchial and mesenteric LNs and JPP) had the highest frequency of cells spontaneously secreting IL-10 while tonsils had the lowest. The frequency of B cells spontaneously secreting IL-10 was lowest in blood and spleen. There was large inter-animal variation in the frequency of CD21⁺ B cells spontaneously secreting IL-10 and no significant difference was detected following CpG ODN stimulation. When comparing within individual animals there was, however, a consistent increase in the frequency of CD21⁺ cells secreting IL-10 following CpG ODN stimulation versus stimulation with GpC control ODN. The presence of inducible (i)B_reg cells in ovine mucosal tissues supports previous evidence from mice indicating that B cells have the capacity to modulate inflammatory responses. The presence of iB_reg cells in ruminants may also provide a novel therapeutic target for both immunomodulatory drugs and vaccines designed to control antigen-specific mucosal inflammation.

Review: Capripoxvirus Diseases: Current Status and Opportunities for Control

Lumpy skin disease, sheeppox and goatpox are high-impact diseases of domestic ruminants with a devastating effect on cattle, sheep and goat farming industries in endemic regions. In this article, we review the current geographical distribution, economic impact of an outbreak, epidemiology, transmission and immunity of capripoxvirus. The special focus of the article is to scrutinize the use of currently available vaccines to investigate the resource needs and challenges that will have to be overcome to improve disease control and eradication, and progress on the development of safer and more effective vaccines. In addition, field evaluation of the efficacy of the vaccines and the genomic database available for poxviruses are discussed.

Human dendritic cells expressing hepatitis C virus core protein display transcriptional and functional changes consistent with maturation

Hepatitis C virus (HCV) causes a chronic liver infection, which may result in cirrhosis and hepatocellular carcinoma. Impairment of the maturation process in dendritic cells (DCs) may be one of the mechanisms responsible for immune evasion of HCV. The core and NS3 proteins are among the most conserved HCV proteins and play a key role in viral clearance. To evaluate the effects of these proteins on DCs, monocyte-derived immature DCs (iDCs) were transfected with in vitro transcribed (IVT) HCV core or NS3 RNA and treated with maturation factors. Neither core nor NS3 had an inhibitory effect on DC maturation; however, transfection of iDCs with IVT core RNA appeared to result in changes compatible with maturation. To investigate this in more detail, the transcriptional profiles of iDCs transfected with IVT core, NS3 or green fluorescent protein (GFP) RNA were examined using a DC-specific membrane array. Of the 288 genes on the array, 46 genes were distinctively up- or down-regulated by transfection with IVT core RNA in comparison with NS3 or GFP RNA treatments. Forty-two of these genes are involved in DC maturation. The effects of core on maturation of iDCs were confirmed with a significant increase in surface expression of CD83 and HLA-DR, a reduction of phagocytosis, as well as an increase in proliferation and IFN-γ secretion by T cells in a mixed lymphocyte reaction assay. These results show that HCV core does not have an inhibitory effect on human DC maturation, but could be a target for the immune system.

Effect of stress on viral-bacterial synergy in bovine respiratory disease: novel mechanisms to regulate inflammation

The severity of bovine respiratory infections has been linked to a variety of factors, including environmental and nutritional changes, transportation, and social reorganization of weaned calves. Fatal respiratory infections, however, usually occur when a primary viral infection compromises host defences and enhances the severity of a secondary bacterial infection. This viral–bacterial synergy can occur by a number of different mechanisms and disease challenge models have been developed to analyse host responses during these respiratory infections. A primary bovine herpesvirus-1 (BHV-1) respiratory infection followed by a secondary challenge with Mannheimia haemolytica results in fatal bovine respiratory disease (BRD) and host responses to these two pathogens have been studied extensively. We used this disease model to demonstrate that stress significantly altered the viral–bacterial synergy resulting in fatal BRD. Functional genomic analysis revealed that BHV-1 infection enhanced toll-like receptors (TLR) expression and increased pro-inflammatory responses which contribute to the severity of a Mannheimia haemolytica infection. TLRs play a critical role in detecting bacterial infections and inducing pro-inflammatory responses. It is difficult to understand, however, how stress-induced corticosteroids could enhance this form of viral–bacterial synergy. Nuclear translocation of the glucocorticoid receptor activates cell signalling pathways which inhibit both TLR signalling and pro-inflammatory responses. The apparent conundrum between stress-induced corticosteroids and enhanced BRD susceptibility is discussed in terms of present data and previous investigations of stress and respiratory disease.

A novel regulatory B-cell population in sheep Peyer's patches spontaneously secretes IL-10 and downregulates TLR9-induced IFNalpha responses

Peyer's patches (PPs) play an important role in the induction of immune responses in the intestine, but regulation of Toll-like receptor (TLR)-induced innate immune responses in PPs is not well understood. We investigated the responses of PPs and other immune cells to the TLR9 agonist, CpG oligodeoxynucleotide (ODN). Peripheral blood mononuclear cells and lymph node cells secreted significant amounts of interferon (IFN)-alpha, IFNgamma, and interleukin (IL)-12 following stimulation with CpG ODN. In contrast, PP cells exhibited poor cytokine responses, despite abundant expression of TLR9 mRNA. PP cells spontaneously secreted high levels of IL-10, and the primary source of the IL-10 was resting CD5(-)CD11c(-)CD21(+) B cells. Neutralization of the IL-10 or depletion of CD21(+) B cells resulted in a significant increase in CpG-induced IFNalpha-response in PPs, suggesting that IL-10 from B cells regulate innate responses in PPs. These IL-10-secreting PP B cells may represent a novel subset of the recently proposed regulatory B cells (B(regs)) in the intestine.

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

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

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

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

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

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

Strategies for loading dendritic cells with hepatitis C NS5a antigen and inducing protective immunity

Dendritic cell (DC)-based vaccination strategies are promising for the treatment of cancers and infectious diseases including hepatitis C virus (HCV). As the induction of T cell-mediated immune responses by DC vaccination is highly dependent on efficient antigen loading of the DCs, the purpose of this study was to identify an optimal nonviral DC loading strategy for HCV NS5a. Furthermore, the efficacy of immunization with the NS5a-loaded DCs in comparison to plasmid encoding NS5a and NS5a protein was evaluated. Transfection of DCs with mRNA was most efficient with close to 100% of DCs expressing NS5a, whereas approximately 10% of protein-pulsed DCs and <1% of plasmid-transfected DCs expressed NS5a, suggesting remarkably different loading efficiencies. Vaccination of mice with NS5a mRNA-transfected DCs or NS5a protein-pulsed DCs resulted in significantly stronger CD4(+) and CD8(+) T-cell responses and protection from challenge with vaccinia virus expressing NS3/NS4/NS5, in comparison to vaccination with NS5a DNA-transfected DCs, plasmid encoding NS5 or rNS5a protein formulated with alum. Furthermore, vaccination with NS5a mRNA-transfected DCs was superior to vaccination with rNS5a-pulsed DCs. These data have important clinical implications, with mRNA-transfected DCs providing a safe and effective vaccination strategy against hepatitis C and possibly other pathogens.

DNA prime protein boost strategies protect cattle from bovine viral diarrhea virus type 2 challenge

At present, infections with bovine viral diarrhea virus (BVDV) type 2 occur nearly as frequently as those with BVDV type 1, so development of vaccines that protect cattle from both type 1 and type 2 BVDV has become critical. In this study, we compared various DNA prime-protein boost vaccination strategies to protect cattle from challenge with BVDV-2 using the major protective antigen of BVDV, glycoprotein E2. Calves were immunized with a plasmid encoding either type 1 E2 (E2.1) or type 2 E2 (E2.2) or with both plasmids (E2.1+E2.2). This was followed by a heterologous boost with E2.1, E2.2 or E2.1 and E2.2 protein formulated with Emulsigen and a CpG oligodeoxynucleotide. Subsequently, the calves were challenged with BVDV-2 strain 1373. All vaccinated calves developed both humoral and cell-mediated immune responses, including virus-neutralizing antibodies and IFN-gamma-secreting cells in the peripheral blood. Depletion studies showed that CD4+ T cells were responsible for IFN-gamma production. Furthermore, the calves vaccinated with either the E2.2 or the E2.1+E2.2 vaccines were very well protected from challenge with BVDV-2, having little leukopenia and showing no weight loss or temperature response. In addition, the animals vaccinated with the E2.1 vaccine were partially protected, so there was a certain level of cross-protection. These data demonstrate that a vaccination strategy consisting of priming with E2.2 or E2.1+E2.2 DNA and boosting with E2.2 or E2.1+E2.2 protein fully protects cattle from BVDV-2 challenge.

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

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

Hepatitis C virus non-structural protein-2 activates CXCL-8 transcription through NF-kappaB

Hepatitis C is a devastating disease worldwide. Proteins encoded by the etiologic agent, hepatitis C virus (HCV), are believed to play important roles in HCV-associated pathogenesis. However, the biological functions of the non-structural protein-2 (NS2) encoded by HCV are not well characterized. Here, we show that HCV NS2 protein activates CXCL-8 (interleukin-8, IL-8) transcription in HepG2 cells as measured by reverse transcription-polymerase chain reaction and IL-8 promoter-luciferase reporter assays. Furthermore, when the kappaB site on the IL-8 promoter was eliminated by mutagenesis or when intracellular NF-kappaB activity was suppressed by an inhibitor, NS2 did not activate the IL-8 promoter, suggesting a role of NF-kappaB in this process. These results prompted us to hypothesize that HCV NS2 might be able to activate NF-kappaB. This hypothesis was tested by determination of NF-kappaB-driven reporter gene expression and NF-kappaB p65 subunit subcellular localization after HCV NS2 expression. Indeed, NS2 could up-regulate NF-kappaB-driven luciferase activity and was associated with p65 nuclear localization. These results demonstrate that HCV NS2 up-regulates IL-8 transcription through NF-kappaB. This newly identified function increases our understanding of the role of HCV NS2 protein in virus-host interactions.

Innate immunity and new adjuvants

Vaccination remains the most cost-effective biomedical approach to the control of infectious diseases in livestock. Vaccines based on killed pathogens or subunit antigens are safer but are often ineffective and require coadministration with adjuvants to achieve efficacy. Unfortunately, most conventional adjuvants are poorly defined, complex substances that fail to meet the stringent criteria for safety and efficacy desired in new generation vaccines. A new generation of adjuvants that work by activating innate immunity presents exciting opportunities to develop safer, more potent vaccines. In this review the authors highlight the role of innate immunity in protection against infectious disease and provide some examples of promising new adjuvants that activate innate immunity. They do not review the conventional adjuvants present in many vaccines since they have been reviewed extensively previously.

Transcription mapping and characterization of proteins produced from early region 4 of porcine adenovirus type 3

The early region 4 (E4) of porcine adenovirus 3 (PAdV-3) was characterized by Northern blot, rapid amplification of cDNA ends (RACE), RT-PCR and cDNA sequence analysis. Northern blot analysis revealed three different classes of transcripts, which appeared and peaked at different times post-infection. The RT-PCR, RACE and cDNA sequence analysis identified nine major E4 transcripts, all of which shared a 107-bp 5' leader sequence and a 126-bp 3' terminus. These transcripts have one to three introns removed. Interestingly, of the nine major transcripts, there was one fusion transcript of ORFp1 and ORFp7 (ORFp1/7), which codes for a protein of 119 amino acids. All transcripts initiated at nucleotide 33740 of the PAdV-3 genome. To identify proteins, rabbit antiserum was prepared using a bacterial fusion protein encoding p2, p3, p4 or p7 proteins. Serum against p2, p3 and p4 immunoprecipitated proteins of 13.5, 13.6 and 15.3 kDa, respectively, in in-vitro transcribed and translated mRNA and in PAdV-3-infected cells. Serum against p7 immunoprecipitated a protein of 19.8 kDa in in-vitro transcription and translation analysis but recognized two proteins of 19.8 kDa (encoded by ORFp7) and 14 kDa (encoded by the fusion transcript ORF1/7) in PAdV-3-infected cells. The protein encoded by ORFp2 was localized in the nucleus of PAdV-3-infected cells. The proteins encoded by ORFp3 and ORFp7\ORFp1/7 were detected in the cytoplasm of PAdV-3-infected cells. However, the protein encoded by ORFp4 was observed both in the cytoplasm and nucleus of PAdV-3-infected cells.

Intranasal immunization using biphasic lipid vesicles as delivery systems for OmlA bacterial protein antigen and CpG oligonucleotides adjuvant in a mouse model

The nasal mucosa is an important arm of the mucosal system since it is often the first point of contact for inhaled antigens. The ineffectiveness of the simple delivery of soluble antigens to mucosal membranes for immunization has stimulated extensive studies in appropriate delivery systems and adjuvants. We have evaluated biphasic lipid vesicles as a novel intranasal (i.n.) delivery system (designated as vaccine targeting adjuvant, VTA) containing bacterial antigens and CpG oligodeoxynucleotides (ODNs). Results show that administration of antigen and CpG ODNs in biphasic lipid vesicles resulted in greater induction of IgA levels in serum (P< 0.05) and mucosal antibody responses such as IgA in nasal secretions and lung (P< 0.01) after immunization with a combined subcutaneous (s.c.)/i.n. as compared to s.c./s.c. approach. Based on antibody responses, VTA formulations were found to be suitable as delivery systems for antigens and CpG ODNs by the intranasal route, resulting in a Th2-type of immune response, characterized by IgG1 and IL-4 production at the systemic level.

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.

The cell-mediated immune response induced by plasmid encoding bovine herpesvirus 1 glycoprotein B is enhanced by plasmid encoding IL-12 when delivered intramuscularly or by gene gun, but not after intradermal injection

Bovine herpesvirus 1 (BHV-1) causes respiratory and genital infections in cattle. Previously we demonstrated that a DNA vaccine encoding a truncated, secreted form of BHV-1 glycoprotein B (tgB) induces cytotoxic T lymphocyte (CTL) responses in C3H mice. In this study we investigated the potential of interleukin 12 (IL-12) to further enhance the CTL response. C3H mice were immunized with a plasmid encoding tgB or with plasmids encoding tgB and murine IL-12. When the plasmid encoding tgB was delivered intramuscularly or epidermally by a gene gun, co-administration with IL-12 plasmid stimulated the synthesis of more IgG2a, the production of higher levels of IFN-gamma, and more effective killing by CTLs. In contrast, after intradermal delivery no effect of co-administration of IL-12 encoding plasmid was observed. Further investigation suggested that antigen and IL-12 need to be expressed in the draining lymph nodes, where IL-12 can have a direct effect on T cells.

Intercellular trafficking of the major tegument protein VP22 of bovine herpesvirus-1 and its application to improve a DNA vaccine

Intercellular spread of bovine herpesvirus-1 (BHV-1) VP22 was demonstrated in living COS-7 cells transfected with a plasmid expressing VP22-YFP (yellow fluorescence protein) and CFP (cyan fluorescence protein) bicistronically. The intercellular trafficking property of VP22 was localized to the C-terminal portion of the molecule (amino acids 121-258; VP22-C). Plasmids encoding a truncated form of BHV-1 glycoprotein D (tgD) fused to VP22, VP22-C, or the N-terminal portion of VP22 (amino acids 1-120; VP22-N) were constructed. Mice immunized with plasmid encoding tgD-VP22 or tgD-VP22-C developed stronger immune responses when compared to animals immunized with plasmid encoding tgD or tgD fused to tgD-VP22-N.

Vaccination of cattle with Mycobacterium bovis culture filtrate proteins and CpG oligodeoxynucleotides induces protection against bovine tuberculosis

Culture filtrate protein (CFP) vaccines have been shown to be effective in small animal models for protecting against tuberculosis while immunisation with these types of vaccines in cattle has been less successful. A study was conducted in cattle to evaluate the ability of selected adjuvants and immunomodulators to stimulate protective immune responses to tuberculosis in animals vaccinated with Mycobacterium bovis CFP. Seven groups of cattle (n=5) were vaccinated with M. bovis CFP formulated with either Emulsigen or Polygen adjuvant alone or in combination with a specific oligodeoxynucleotides (ODN), polyinosinic acid: polycytidylic acid (poly I:C) or poly I:C and recombinant granulocyte-macrophage colony stimulating factor. Two additional groups were vaccinated subcutaneously with BCG or non-vaccinated. In contrast to the strong interferon-gamma (IFN-gamma) responses induced by BCG, the CFP vaccines induced strong antibody responses but weak IFN-gamma responses. The addition of CpG ODN to CFP significantly enhanced cell-mediated responses and elevated antibody responses to mycobacterial antigens. Of the CFP vaccinated groups, the strongest IFN-gamma responses to CFP vaccines were measured in animals vaccinated with CFP/Emulsigen+CpG or CFP/Polygen+CpG. The animals in these two groups, together with those in the BCG and non-vaccinated groups were challenged intratracheally with virulent M. bovis at 13 weeks after the first vaccination and protection was assessed, by examination for presence of tuberculous lesions in the lungs and lymph nodes, 13 weeks later at postmortem. While BCG gave the best overall protection against tuberculosis, significant protection was also seen in animals vaccinated with CFP/Emulsigen+CpG. These results establish an important role for CpG ODN in stimulating protective Th1 responses to tuberculosis in cattle and indicate that a sub-unit protein vaccine can protect these animals against tuberculosis.

Formulation with CpG oligodeoxynucleotides prevents induction of pulmonary immunopathology following priming with formalin-inactivated or commercial killed bovine respiratory syncytial virus vaccine

Commercial killed bovine respiratory syncytial virus (K-BRSV) and formalin-inactivated BRSV (FI-BRSV) tend to induce Th2-type immune responses, which may not be protective and may even be detrimental during subsequent exposure to the virus. In this study we assessed the ability of CpG oligodeoxynucleotides (ODNs) to aid in the generation of effective and protective BRSV-specific immune responses. Mice were immunized subcutaneously with FI-BRSV formulated with CpG ODN, Emulsigen (Em), CpG ODN and Em, or non-CpG ODN and Em. Two additional groups were immunized with K-BRSV or K-BRSV and CpG ODN. After two vaccinations, the mice were challenged with BRSV. FI-BRSV induced Th2-biased immune responses characterized by production of serum immunoglobulin G1 (IgG1) and IgE, as well as interleukin-4 (IL-4), by in vitro-restimulated splenocytes. Formulation of FI-BRSV with CpG ODN, but not with non-CpG ODN, enhanced serum IgG2a and IFN-gamma production by splenocytes, whereas serum IgE was reduced. Although the immune response induced by K-BRSV was not as strongly Th2 biased, the addition of CpG ODN to this commercial vaccine also resulted in a more Th1-type response. Furthermore, the addition of CpG ODN to the BRSV vaccine formulations resulted in enhanced neutralizing antibody responses. Significant production of IL-5, eotaxin, and eosinophilia was observed in the lungs of FI-BRSV- and K-BRSV-immunized mice. However, IL-5 and eotaxin levels, as well as the number of eosinophils, were decreased in the mice vaccinated with the CpG ODN-formulated vaccines. Finally, when formulated with CpG ODN, both FI-BRSV and K-BRSV significantly reduced virus production after challenge with BRSV.

siRNA targeting the leader sequence of SARS-CoV inhibits virus replication

SARS-CoV (the SARS-Associated Coronavirus) was reported as a novel virus member in the coronavirus family, which was the cause of severe acute respiratory syndrome. Coronavirus replication occurs through a unique mechanism employing Leader sequence in the transcripts when initiating transcription from the genome. Therefore, we cloned the Leader sequence from SARS-CoV(BJ01), which is identical to that identified from SARS-CoV(HKU-39849), and constructed specific siRNA targeting the Leader sequence. Using EGFP and RFP reporter genes fused with the cloned SARS-CoV Leader sequence, we demonstrated that the siRNA targeting the Leader sequence decreased the mRNA abundance and protein expression levels of the reporter genes in 293T cells. By stably expressing the siRNA in Vero E6 cells, we provided data that the siRNA could effectively and specifically decrease the mRNA abundance of SARS-CoV genes as analyzed by RT-PCR and Northern blot. Our data indicated that the siRNA targeting the Leader sequence inhibited the replication of SARS-CoV in Vero E6 cells by silencing gene expression. We further demonstrated, via transient transfection experiments, that the siRNA targeting the Leader sequence had a much stronger inhibitory effect on SARS-CoV replication than the siRNAs targeting the Spike gene or the antisense oligodeoxynucleotides did. This report provides evidence that targeting Leader sequence using siRNA could be a powerful tool in inhibiting SARS-CoV replication.

Infection of newborn piglets with Bordetella pertussis: a new model for pertussis

Bordetella pertussis is the causative agent of pertussis or whooping cough. This bacterium is a human pathogen that under experimental conditions also infects selected rodents and primates. Here, we show for the first time that newborn piglets can be infected with B. pertussis when it is delivered intrapulmonarily. Infected piglets displayed fever and respiratory symptoms, such as nasal discharge, nonparoxysmal coughing, and breathing difficulties. Eventually, all infected animals developed severe bronchopneumonia, which in some cases was combined with a fibrinous pleuritits. Immunohistochemical staining revealed the presence of large numbers of B. pertussis cells within airways, adhering to the epithelial lining or phagocytosed by macrophages and neutrophils. Viable bacteria were reisolated from bronchoalveolar lavages and lung lesions for more than 10 days postinfection. The systemic presence of pertussis toxin was shown by hypoglycemia, lymphocytosis, and induction of a clustered pattern of CHO cells by serum and bronchoalveolar lavage samples. Thus, a large-animal model for pertussis was developed, which should complement existing rodent models for identifying the immune responses relevant to the design of new vaccines. In particular, this model should help researchers analyze the roles of both maternal and mucosal immunity in disease protection against pertussis and should ultimately assist in the design of new vaccines for early life protection.

Immunization with a bovine herpesvirus 1 glycoprotein B DNA vaccine induces cytotoxic T-lymphocyte responses in mice and cattle

Virus-specific cytotoxic T lymphocytes (CTLs) are considered to be important in protection against and recovery from viral infections. In this study, several approaches to induce cytotoxicity against bovine herpesvirus 1 (BHV-1) were evaluated. Vaccination of C57BL/6 mice with BHV-1 induced a strong humoral, but no CTL, response, which may be due to downregulation of major histocompatibility complex class I molecules. In contrast, vaccinia virus expressing glycoprotein B (gB) elicited a weaker antibody response, but strong cytotoxicity, in mice. As an approach to inducing both strong humoral and cellular immune responses, a plasmid vector was then used to express gB. Both antibody and CTL responses were induced by the plasmid encoding gB in C57BL/6 and C3H mice, regardless of the type of vector backbone. This demonstrated that DNA immunization induces a broad-based immune response to BHV-1 gB. Interestingly, removal of the membrane anchor, which resulted in secretion of gB from transfected cells, did not result in reduced cytotoxicity. Here, it is shown that, compared with the cell-associated counterpart, plasmid-encoded secreted protein may induce enhanced immune responses in cattle. Therefore, calves were immunized intradermally with pMASIAtgB, a plasmid encoding the secreted form of gB (tgB), using a needle-free injection system. This demonstrated that pMASIAtgB elicited both humoral responses and activated gamma interferon-secreting CD8+ CTLs, suggesting that a DNA vaccine expressing tgB induces a CTL response in the natural host of BHV-1.

Novel vaccines from biotechnology

Vaccination continues to be the main approach to protecting animals from infectious diseases. Until recently, all licensed vaccines were developed using conventional technologies. However, the introduction of modern molecular biological tools and genomics, combined with a better understanding of not only which antigens are critical in inducing protection, but an appreciation of host defences that must be stimulated, has opened a new opportunity to develop safer and more effective vaccines. The authors describe the current and future trends in vaccine development and stress that in addition to identifying and producing the protective antigens, it is critical to formulate and deliver these vaccines appropriately to maximise the potential of modern advances in pathogenesis and vaccinology.

Passive protection to bovine rotavirus (BRV) infection induced by a BRV VP8* produced in plants using a TMV-based vector

We have previously reported on the use of a tobacco mosaic virus (TMV) vector TMV-30B to express foreign viral antigens for use as experimental immunogens. Here we describe the development of an improved TMV-30B vector that adds a sequence of 7 histidine residues to the C-terminus of recombinant proteins expressed in the vector. We used this TMV-30B-HISc vector to express the VP8* fragment of the VP4 protein from bovine rotavirus (BRV) strain C-486 in plants. Recombinant VP8* protein was purified from N. benthamiana leaves at 7 days post-inoculation by immobilized metal affinity chromatography. The plant-produced VP8* was initially detected using anti-His tag mAb and its antigenic nature was confirmed using both monoclonal and polyclonal specific antisera directed against BRV. Adult female mice, inoculated by the intraperinoteal route with an immunogen containing 4 microg of recombinant VP8*, developed a specific and sustained response to the native VP8* from the homologous BRV. Eighty five percent of suckling mice from immunized dams that were challenged with the homologous virus at the fifth day of age were protected from virus as compared to 35% of the pups from mothers immunized with a control protein. These results demonstrate that the plant-produced VP8* was able to induce passive protection in the new born through the immunization of dams. This suggests that the technology presented here provides a simple method for using plants as an inexpensive alternative source for production of recombinant anti-rotavirus antigens.

In vivo immunostimulatory effects of CpG oligodeoxynucleotide in cattle and sheep

Oligodeoxynucleotides (ODN) containing cytosine-phosphate-guanosine (CpG) motifs have been shown to activate the innate immune system and protect mice and chicken from bacterial and viral infections. Unfortunately, similar studies in other veterinary species are lacking. In this study we assessed the in vivo immunostimulatory effects of CpG ODN 2007, an ODN with previously demonstrated in vitro biological activity. The in vivo effects of ODN 2007 were compared in two closely related outbred species, sheep and cattle, to determine if there were common biological responses. We demonstrated that subcutaneous (s.c.) injection of the CpG ODN induces an acute phase response in the form of a transient fever, a mild transient increase in circulating neutrophils and elevated serum haptoglobin in both sheep and cattle. Sheep injected with CpG ODN also exhibited increased serum 2'5'-oligoadenylate (2'5'-A) synthetase activity, but no increase in serum 2'5'-A synthetase was detected in cattle. The ODN-induced responses were stronger in animals injected with CpG ODN formulated in 30% emulsigen than phosphate buffer saline (PBS) alone. These in vivo data demonstrate for the first time that a CpG ODN induces acute phase immunostimulatory responses in sheep and cattle. However, CpG ODN-induced antiviral effector molecule 2'5'-A synthetase was detected only in sheep but not in cattle.

Safety and efficacy of CpG-containing oligodeoxynucleotides as immunological adjuvants in rabbits

The efficacy of oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG ODN) as an adjuvant for rabbits was assessed alone and in combination with aluminum hydroxide (CpG/alum). The CpG/alum combination elicited a greater immune response to several antigens compared to Freund's adjuvant. A non-CpG/alum combination did not have the same effects as CpG/alum suggesting that the adjuvanticity was related to the CpG motifs. In addition, we formulated one of the antigens with combinations of CpG ODN and 30 or 10% Emulsigen (Em) [CpG/Em (30%) and CpG/Em (10%)]. Both CpG/Em (30%) and CpG/Em (10%) were more effective than Em, and equivalent to CpG/alum. The CpG/Em (10%) combination caused minimal tissue damage. Our results demonstrate that the addition of CpG ODN to aluminum hydroxide or to 10% Em significantly improves the efficiency of these adjuvants, without enhancing tissue reaction.

Safety of CpG oligodeoxynucleotides in veterinary species

Bacterial DNA and synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs in particular sequence contexts (CpG ODN) are recognized as a danger signal by the innate immune system of vertebrates. For this reason, CpG ODNs have a potential application as both an adjuvant and nonspecific immune modulator and are currently being evaluated in a number of human and veterinary clinical trials. Given their potent immunostimulatory activity, CpG ODNs could possibly induce adverse reactions. As all adjuvants and immune modulators must be nontoxic to meet safety requirements, it was essential to address the safety aspects of CpG ODNs. The current review summarizes experiments carried out to date to establish the safety of CpG ODNs in animals.

Molecular approaches to disease control

Recent advances in molecular biology, genomics, and immunology are revolutionizing our approach to managing infectious diseases of humans, livestock, and poultry. One of the most interesting additions to the armamentarium of research focusing on controlling infectious diseases has been a better understanding of how the host's innate immune system recognizes "danger" signals. Additionally, there has been recognition of the relationship between the innate and the specific arms of the immune system. For example, the recent discovery that CpG motifs can modulate immune responses has been used both as an adjuvant to enhance the responses to vaccines, as well as a direct immunostimulant to prevent infections. Using an Escherichia coli chicken model, we have been able to prevent cellulitis in chickens with CpG alone. Thus, CpG can be used immunoprophylactically to reduce infectious diseases. In addition, we will describe how CpG formulations with various antigens; recombinant proteins, peptides, and conventional vaccines can enhance immune responses to each of these different vaccine combinations. What is even more interesting is that CpG incorporation in vaccines can shift the immune response from a predominant T helper 2 (Th2)-like immune response generally induced by killed or subunit proteins to a much more balanced Th1-Th2 response. These immunomodulatory effects have significant implications for management of infectious diseases of all vertebrates.

Induction of protective immunity in pigs after immunisation with CpG oligodeoxynucleotides formulated in a lipid-based delivery system (Biphasix)

A large number of studies demonstrated the immunostimulatory effects of CpG oligonucleotides (ODN), particularly in mice. In the present study, we evaluated the ability of lipid-based delivery systems to enhance the adjuvant effect of CpG-ODN and protect against infection in a porcine pleuropneumonia model. Increased levels of OmlA-specific antibody were detected in animals immunised with OmlA and CpG-ODN formulated in the delivery system Biphasix-vaccine targeting adjuvant (VTA), compared to pigs immunised with VTA without CpG-ODN or CpG-ODN alone. In addition, the responses induced by VTA/CpG formulation were similar to those induced by the commercial adjuvant VSA; however, VTA formulations caused significantly less tissue damage than VSA.

Biological activity of immunostimulatory CpG DNA motifs in domestic animals

Bacterial DNA contains a much higher frequency of CpG dinucleotides than are present in mammalian DNA. Furthermore, bacterial CpG dinucleotides are often not methylated. It is thought that these two features in combination with specific flanking bases constitute a CpG motif that is recognized as a "danger" signal by the innate immune system of mammals and therefore an immune response is induced when these motifs are encountered. These immunostimulatory activities of bacterial CpG DNA can also be achieved with synthetic CpG oligodeoxynucleotides (ODN). Recognition of CpG motifs by the innate immune system requires engagement of Toll-like receptor 9 (TLR-9), which induces cell signaling and subsequently triggers a pro-inflammatory cytokine response and a predominantly Th1-type immune response. CpG ODN-induced innate and adaptive immune responses can result in protection in various mouse models of disease. Based on these observations, clinical trials are currently underway in humans to evaluate CpG ODN therapies for cancer, allergy and infectious disease. However, potential applications for immunostimulatory CpG ODN in species of veterinary importance are just being explored. In this review, we will highlight what is presently known about the immunostimulatory effects of CpG ODN in domestic animals.

Induction of immune responses by DNA vaccines in large animals

It is generally recognized that DNA vaccines are often less effective in large animals than in mice. One possible reason for this reduced effectiveness may be transfection deficiency and the low level of expression elicited by plasmid vectors in large animals. In our attempt to enhance transfection efficiency and, thereby, enhance immune responses, we employed a variety of methods inducing gene gun delivery or suppositories as delivery vehicles to mucosal surfaces, as well as electroporation for systemic immunization. To test these different systems, we used two different antigens-a membrane antigen from bovine herpesvirus glycoprotein (BHV-1) gD and a particulate antigen from hepatitis virus B. Gene gun and suppository delivery of BHV-1 gD to the vagina resulted in the induction of mucosal immunity not only in the vagina, but also at other mucosal surfaces. These data support the contention of a common mucosal immune system. In the case of electroporation, we were able to develop significant enhancement of gene expression following electroporation with surface electrodes (non-invasive electroporation) as well as invasive electroporation using single or six-needle electrodes. Various delivery systems such as bioject or needle delivery also influenced the immune response in both the presence and absence of electroporation. These studies also demonstrated that co-administration of plasmids coding for two different antigens (BHV-1 gD and hepatitis B surface antigen (HbsAg)) did not result in significant interference between the plasmids. These studies suggest that various combinations of delivery systems can enhance immunity to DNA-based vaccines and make them practical for administration of these vaccines in large animals.

Mucosal immune responses following oral immunization with rotavirus antigens encapsulated in alginate microspheres

Availability of effective oral vaccine delivery vehicles should contribute to the success of oral immunization in domestic animals. To achieve this goal, we evaluated alginate microspheres for their capacity to induce mucosal immune responses following oral and enteric immunizations. Mice were immunized with either live porcine rotavirus (PRV) or its recombinant VP6 protein, encapsulated in alginate microspheres or unencapsulated. VP6-specific IgG (but no IgA) antibodies were detected in the sera of mice after a single intraperitoneal (i.p.) immunization with either VP6 in Incomplete Freund's adjuvant (VP6-IFA), VP6 in alginate microspheres (VP6-MS) or with live PRV in incomplete Freund's adjuvant (PRV-IFA). In contrast, VP6-specific IgA (but no IgG) was detected in culture supernatants of mesenteric lymph nodes from mice immunized i.p. with either VP6-IFA or with PRV-IFA. Oral immunization with VP6-MS induced the highest level of VP6-specific fecal IgA antibody, similar to responses induced by oral immunization with live PRV. Furthermore, the VP6-specific fecal IgA could be boosted by a secondary i.p. immunization with VP6. Further experiments were performed in a sheep intestinal 'loop' model to evaluate uptake of microspheres by Peyer's patches. Microspheres containing colloidal carbon were specifically bound and transported by follicle-associated epithelium of Peyer's patches. Additionally, mucosal immune responses were detected following enteric immunization with porcine serum albumin (PSA) encapsulated in alginate microspheres. Our results confirm that alginate microspheres are an effective oral delivery vehicle for protein antigens and intestinal IgA antibody responses are induced by antigens encapsulated in alginate microspheres without any additional mucosal adjuvant. These investigations confirm that alginate microspheres have the potential as an effective delivery vehicle for oral immunization of ruminants.

Augmentation of cellular immune responses to bovine herpesvirus-1 glycoprotein D by vaccination with CpG-enhanced plasmid vectors

The potential of CpG-enhanced plasmid DNA vectors encoding a truncated secreted form of bovine herpesvirus-1 (BHV-1) glycoprotein D (tgD) to induce enhanced immune responses in cattle was investigated. We created tgD expression plasmids containing 0, 40 or 88 copies of the hexamer 5' GTCGTT 3', a known pan-activating CpG motif in several species. The total tgD-specific IgG titre of calves immunized with these plasmids did not correlate with the CpG content of the plasmid backbone. However, the pBISIA88-tgD-vaccinated group showed a significantly lower IgG1:IgG2 ratio than calves immunized with pBISIA40-tgD or pMASIA-tgD, which has no CpG motifs inserted. Antigen-specific lymphocyte proliferation and IFN-gamma secretion by peripheral blood mononuclear cells correlated positively with the CpG content of the vectors. In contrast, calves that received a killed BHV-1 vaccine had an IgG1-predominant isotype and low lymphocyte proliferation and IFN-gamma levels. Following challenge, the pBISIA88-tgD-immunized group developed the greatest anamnestic response, the highest BHV-1 neutralization titres in serum and a significantly lower level of virus shedding than the saline control group. However, there were no significant differences in clinical symptoms of infection between the DNA-immunized groups and the saline control group. These data indicate that CpG-enhanced plasmids induce augmented immune responses and could be used to vaccinate against pathogens requiring a strong cellular response for protection.

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

Vaccine adjuvants must have the capacity to increase protective immune responses with minimal side effects. Conventional adjuvants not only cause undesirable tissue site reactions, but often induce T-helper type 2 (Th2)-biased responses which may be undesirable in certain disease scenarios. Oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG ODN) are novel adjuvants known to promote Th1-type immune responses. In this study, we compared various mineral oil, metabolizable oil and non-oil adjuvants alone and in combination with CpG ODN for their ability to augment immune responses to a truncated secreted form of bovine herpesvirus (BHV) glycoprotein D (tgD). All adjuvants tested induced Th2-biased immune responses characterized by a predominance of serum IgG1 as well as interleukin-4 (IL-4) production by in vitro stimulated splenocytes. The inclusion of CpG ODN in these formulations not only increased immune responses, but more importantly enhanced serum IgG2a levels and production of interferon-gamma (IFN-gamma) by splenocytes, indicating a more balanced or Th1-type response. The use of a mineral oil-based adjuvant at reduced doses in combination with CpG ODN attenuated the tissue damage while not compromising the magnitude of the immune response in both mice and sheep. In addition, reduced amounts of mineral oil combined with CpG ODN induced a more balanced Th1/Th2 immune response than the mineral oil used alone. Our results clearly demonstrate that CpG ODN can be used to enhance magnitude and balance of an immune response while reducing the amount of mineral oil and hence undesirable side effects of vaccine adjuvants.

Vaccination: a management tool in veterinary medicine

Conventional vaccines have been used for some 200 years, primarily to control infectious diseases. It is envisaged that such vaccines will continue to be used and new ones developed using conventional technology. However, in addition to conventional vaccines, novel approaches using biotechnology are already in use and many more are in various stages of development. These novel vaccines are not only being used to control infectious diseases, but also to improve productivity of livestock by modulating hormones, for gender selection, as well as in controlling ectoparasites. The recent developments in vaccination technology in all of these areas are described.

Induction of mucosal immune responses following enteric immunization with antigen delivered in alginate microspheres

Oral immunization is the most effective way of inducing immune responses in the intestinal tract. Biodegradable microspheres have been used extensively for the delivery of antigens to the Peyer's patches (PPs) within the gut-associated lymphoid tissue (GALT). We evaluated various formulations of alginate microspheres for their capacity to induce mucosal immune responses in vivo. Multiple intestinal "loops" each containing a single PP, were surgically prepared in lambs. We have previously showed that PP in individual intestinal loops function as independent sites for the induction of immune responses. This animal model provides a system for directly comparing different antigen formulations within the same animal. Individual intestinal loops were injected with a model antigen, porcine serum albumin (PSA) encapsulated in three different formulations of alginate micropsheres. Three weeks after immunization, PSA-specific immune responses were assayed with antibody secreting cell (ASC) ELISPOT, lymphocyte proliferative responses (LPRs), IFN-gamma production and antibody secreted into intestinal loops. PSA encapsulated in alginate micropsheres or in saline induced humoral immune responses as indicated by the presence of numerous ASC. However, PSA-specific T-cell responses (LPR and IFN-gamma production) were not induced.

The immunogenicity and protective efficacy of bovine herpesvirus 1 glycoprotein D plus Emulsigen are increased by formulation with CpG oligodeoxynucleotides

The immunogenicity and protective efficacy of a bovine herpesvirus 1 (BHV-1) subunit vaccine formulated with Emulsigen (Em) and a synthetic oligodeoxynucleotide containing unmethylated CpG dinucleotides (CpG ODN) was determined in cattle. A truncated, secreted version of BHV-1 glycoprotein D (tgD) formulated with Em and CpG ODN at concentrations of 25, 2.5, or 0.25 mg/dose produced a more balanced immune response, higher levels of virus neutralizing antibodies, and greater protection after BHV-1 challenge compared to tgD adjuvanted with either Em or CpG ODN alone. In contrast, tgD formulated with Em and either 25 mg of a non-CpG ODN or another immunostimulatory compound, dimethyl dioctadecyl ammonium bromide, induced similar immunity and protection compared to tgD formulated with Em alone, a finding which confirms the immunostimulatory effect of ODN to be CpG motif mediated. Our results demonstrate the ability of CpG ODN to induce a strong and balanced immune response in a target species.

CpG-containing oligodeoxynucleotides augment and switch the immune responses of cattle to bovine herpesvirus-1 glycoprotein D

The adjuvanticity of a synthetic oligodeoxynucleotide containing unmethylated CpG motifs (CpG ODN) was determined in cattle. Calves were immunized with a truncated secreted version of glycoprotein D (tgD) of bovine herpes virus-1 (BHV-1) formulated with alum, CpG ODN, or a combination of both. BHV-1 tgD formulated with CpG ODN or with alum and CpG ODN induced a stronger and more balanced immune response than tgD in alum. This level of immunity was of sufficient magnitude to minimize weight loss and significantly reduce the duration of virus shedding after intranasal viral challenge. Local tissue reactions generated by CpG ODN were very mild and transient, whereas reactions induced by alum or a combination of CpG ODN and alum were moderate in severity and duration. These data demonstrate that CpG ODN causes minimal injection site reactions and yet acts as an effective adjuvant in cattle.

Veterinary applications of DNA vaccines

DNA immunization of livestock has proven to be more challenging than similar approaches in mice. To identify parameters, which could influence the magnitude and type of immune response generated by DNA immunization, we have assessed promoter strength, the role of introns, route of delivery as well as form of antigen. Our results indicate that all of these factors can have an impact on whether an immune response will occur or not, as well as influence the type of immune response generated. Finally we have demonstrated that DNA does have a significant effect on lymph node architecture, suggesting that the DNA does not remain exclusively at the site of injection.

Monocytes are required for optimum in vitro stimulation of bovine peripheral blood mononuclear cells by non-methylated CpG motifs

Bacterial DNA and synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs within certain flanking base pairs are recognized as a danger signal by the innate immune system of vertebrates. Using lymphocyte proliferative response (LPR) and IFN-gamma secretion assays, a panel of 38 ODN was screened for immunostimulatory activity on bovine peripheral blood mononuclear cells. ODN composed of a nuclease resistant phosphorothioate backbone and a leading 5'-TCGTCGTT-3' motif with two 5'-GTCGTT-3' motifs were highly stimulatory in both assays. Flow cytometric analysis and cell-specific surface marker labeling determined that B-cells (surface IgM(+)) were the primary cell population responding in the LPR assay. Depletion of T cells (CD3(+)) from the PBMC population did not affect IFN-gamma secretion or B-cell proliferation when cultured with CpG-ODN. However, depletion of monocytes (DH59B(+)) completely abrogated the ability of CpG-ODN to stimulate IFN-gamma secretion, and significantly reduced the B-cell proliferative response. These data establish the identity of an optimal immunostimulatory CpG motif for cattle and demonstrate that monocytes play a pivotal role in the ability of cell populations to respond to CpG-ODN. These data provide insight for future studies investigating the mechanism of CpG-ODN bioactivity and its application in novel vaccine formulations and immunotherapy.

Plasmid DNA induces increased lymphocyte trafficking: a specific role for CpG motifs

Bacterial DNA, primarily through immunostimulatory cytosine-guanine (CpG) motifs, induces the secretion of cytokines and activates a variety of effector cells. We investigated the possibility that CpG motifs might also modulate immunosurveillance by altering cell trafficking through a regional lymph node. Intradermal injection of plasmid DNA induced rapid and prolonged increases in the number of lymphocytes collected in efferent lymph. This effect on cell trafficking was not dependent on the expression of an encoded reporter gene but varied with plasmid construct and required a circular form. Injection of synthetic oligodeoxyribonucleotides containing CpG motifs did not alter lymphocyte trafficking but CpG-enhanced plasmid induced a dose-dependent increase in cell trafficking. Phenotypic analyses revealed that the increase in cell trafficking involved all lymphocyte subpopulations and represented a mass movement of cells. These observations reveal that bacterial DNA, through immunostimulatory CpG motifs, alters immunosurveillance by increasing cell recruitment to a regional lymph node.

Priming by DNA immunization augments T-cell responses induced by modified live bovine herpesvirus vaccine

DNA vaccines have several advantages over conventional vaccines. One of the most important characteristics is the presentation of antigen via both MHC class I and class II receptors. Although this generally results in strong T-cell responses, antibody production and protection achieved by DNA immunization are unfortunately not always adequate. In contrast, modified live virus (MLV) vaccines usually induce adequate antibody and moderate cellular responses, whereas killed vaccines tend to elicit weak immune responses in general. A DNA prime-MLV boost regimen should result in enhanced cellular immunity and possibly improved antibody production. To test this hypothesis, plasmids encoding bovine herpesvirus-1 (BHV-1) glycoproteins B and D were delivered by gene gun to the genital mucosa of cattle prior to immunization with modified live BHV-1 vaccine. The immune responses induced were compared to those of an MLV-vaccinated group and a negative control group. Although significantly enhanced T-cell responses were induced by priming with the DNA vaccine, there was no increase in antibody titres. Similar levels of protection were induced by the MLV vaccine alone and the DNA prime and MLV boost regimen, which suggests that there is no correlation between the induction of T-cell responses and protection from BHV-1 challenge.

Mutational analysis of early region 4 of bovine adenovirus type 3

The primary objective of characterizing bovine adenovirus type 3 (BAV3) in greater detail is to develop it as a vector for gene therapy and vaccination of humans and animals. A series of BAV3 early region 4 (E4) deletion-mutant viruses, containing deletions in individual E4 open reading frames (Orf) or combinations of Orfs, were generated by transfecting primary fetal bovine retinal cells with E4-modified genomic DNA. Each of these mutants was further analyzed for growth kinetics, viral DNA accumulation, and early-late protein synthesis. Mutant viruses carrying deletions in Orf1, Orf2, Orf3, or Orf4 showed growth characteristics similar to those of the E3-deleted BAV3 (BAV302). DNA accumulation and early/late protein synthesis were also indistinguishable from those of BAV302. However, mutant viruses carrying a deletion in Orf5, Orfs 1-3 (BAV429), or Orfs 3-5 (BAV430) were modestly compromised in their ability to grow in bovine cells and express early/late proteins. E4 mutants containing larger deletions, Orfs 1-3 (BAV429) and Orfs 3-5 (BAV430), were further tested in a cotton rat model. Both mutants replicated as efficiently as BAV3 or BAV302 in the lungs of cotton rats. BAV3-specific IgA and IgG responses were detected in serum and at the mucosal surfaces in cotton rats inoculated with mutant viruses. In vitro and in vivo characterization of these E4 mutants suggests that none of the individual E4 Orfs are essential for viral replication. Moreover, successful deletion of a 1.5-kb fragment in the BAV3 E4 region increased the available insertion capacity of replication-competent BAV3 vector (E3-E4 deleted) to approximately 4.5 kb and that of replication-defective BAV3 vector (E1a-E3-E4 deleted) to approximately 5.0 kb. This is extremely useful for the construction of BAV3 vectors that express multiple genes and/or regulatory elements for gene therapy and vaccination.

Fusion of C3d molecule with bovine rotavirus VP7 or bovine herpesvirus type 1 glycoprotein D inhibits immune responses following DNA immunization

The binding of the complement C3d molecule with receptors on B cells and/or follicular dendritic cells (FDCs) influences the induction of humoral immune responses. For example, C3d fused to an antigen has been shown to have a strong adjuvant effect on antibody production. We investigated the possibility that co-expression of antigen and C3d as a fusion protein could enhance antigen-specific immune responses, following plasmid immunization. One or two copies of murine C3d-cDNA, C3d or (C3d)(2), respectively, were cloned together with bovine rotavirus (BRV) VP7 or bovine herpesvirus type 1 (BHV-1) glycoprotein D (gD) genes. All constructs contained a signal peptide that resulted in the secretion of the expressed proteins. In vitro, the characterization of the chimeric proteins indicated that both VP7 and gD retained their antigenicity and the C3d remained biologically active. However, immunization with plasmids encoding VP7-C3d chimeras did not enhance rotavirus-specific antibody responses and the frequency of BRV-specific IFN-gamma secreting cells in the spleens were significantly lower in mice immunized with pVP7-(C3d)(2) when compared with mice immunized with plasmid encoding VP7. The same pattern of immune responses was observed for plasmids encoding gD-C3d. Both gD-specific antibody responses and the frequency of gD-specific IFN-gamma secreting cells were significantly lower in mice immunized with plasmid expressing gD-C3d chimeras when compared with mice immunized with plasmid encoding gD alone. These results indicate that co-expression of C3d with an antigen actually inhibit both humoral and cell-mediated antigen-specific immune responses.

New approaches for antigen discovery, production and delivery: vaccines for veterinary and human use

Vaccination of individuals has been practiced for many years and has been one of the most effective methods of controlling infectious diseases. Unfortunately, even with this success, society continues to suffer multi-billion dollar economic losses annually due to infectious diseases. These losses occur in all animal species as well as in humans. In order to further reduce these losses, academicians and companies are employing the multidisciplinary approach to develop better and safer vaccines. These include capitalizing on advances in molecular biology, chemistry, pharmacy, immunology, genomics, proteomics, and fermentation. Thus, we are moving from a more empirical approach to vaccine production to a more focused, and, hopefully, more logical approach to identification and production of protective antigens. Furthermore, formulation and delivery of these antigens in playing a major role in revolutionizing how we deliver vaccines to induce the most appropriate immune response and ensure protection. The current review summarizes some of these advances and speculates as to how future vaccines will be produced and delivered for the benefit of society.

Suppository-mediated DNA immunization induces mucosal immunity against bovine herpesvirus-1 in cattle

Mucosal surfaces are the primary sites for the transmission of infectious agents including viruses, so effective vaccines generally should induce mucosal immunity. Furthermore, noninvasive delivery is desirable because of the ease of application, the high degree of patient compliance, and the improved safety for patients and clinicians due to the elimination of needles. Unfortunately, most of the conventional vaccines are parenterally administered and result in systemic rather than mucosal immunity. Here we present the first report of mucosal immunity by noninvasive DNA immunization in a target species. As an approach to induce mucosal immunity against bovine herpesvirus-1, cows were immunized intravaginally with suppositories containing plasmid coding for glycoprotein D. Serum IgG, as well as IgA both in the serum and in the nasal fluids, were detected, which supports the contention of a common mucosal immune system. This level of immunity was of sufficient magnitude to minimize weight loss and significantly reduce the duration of virus shedding after intranasal viral challenge, which demonstrates the efficacy of suppository-based administration of DNA vaccines to target species. As this is a very practical method of delivery, it has great potential to be applied as vaccine or therapy in a variety of species.

CpG motif identification for veterinary and laboratory species demonstrates that sequence recognition is highly conserved

Oligodinucleotides containing CpG motifs stimulate vertebrate immune cells in vitro, have proven efficacy in murine disease models and are currently being tested in human clinical trials as therapies for cancer, allergy, and infectious disease. As there are no known immunostimulatory motifs for veterinary species, the potential of CpG DNA as a veterinary pharmaceutical has not been investigated. Here, optimal CpG motifs for seven veterinary and three laboratory species are described. The preferential recognition of a GTCGTT motif was strongly conserved across two vertebrate phyla, although a GACGTT motif was optimal for inbred strains of mice and rabbits. In a subsequent adjuvanticity trial, the in vitro screening methodology was validated in sheep, representing the first demonstration of CpG DNA efficacy in a veterinary species. These results should provide candidate immunostimulant and therapeutic drugs for veterinary use and enable the testing of CpG DNA in large animal models of human disease.

Multiple intestinal 'loops' provide an in vivo model to analyse multiple mucosal immune responses

Mucosal immunity plays an important role in preventing disease but the induction of protective mucosal immune responses remains a significant challenge. We describe a novel in vivo model to analyze the induction of multiple mucosal immune responses in the small intestine. A sterile segment of intestine ('intestinal-segment'; 2-3 m long) was surgically prepared in the jejunum of 4-6-month-old lambs. This 'intestinal-segment' was then subdivided into consecutive segments, designated as 'loops' (15-20 cm long), that included a Peyer's patch (PP), or 'interspaces' (15-70 cm long), that lacked a visible PP. All 'loops' were sterile when collected 1-4 weeks post-surgery and there was no macroscopic or histological evidence of altered lymph or blood flow. Flow cytometric analysis of cells isolated from PP, mucosal epithelium (IEL) and the lamina propria (LPL) revealed no significant alterations in the cell populations present in 'loop' tissues. The functional integrity of M-cell antigen uptake in sterile intestinal 'loops' was evaluated by comparing the immune response induced by varying doses of soluble versus particulate porcine serum albumin (PSA formulated in alginate microspheres). A dose-dependent, PSA-specific antibody-secreting cell response was restricted to PP present in 'loops' injected with particulate PSA. These observations suggested that PP present in sterile 'loops' were functional and this conclusion was confirmed by detecting cholera toxin-specific antibody-secreting cells and secreted antibody in PP and intestinal contents, respectively, of immunized 'loops.' Thus, each 'loop' provided an independent site to analyze antigen-uptake and the induction of mucosal immune responses by a variety of antigen or vaccine formulations.