CpG ODN 2006 and IL-12 are comparable for priming Th1 lymphocyte and IgG responses in cattle immunized with a rickettsial outer membrane protein in alum

Introduction of an Ultraviolet C-Irradiated 4T1 Murine Breast Cancer Whole-Cell Vaccine Model

The advent of immunotherapy has revolutionized cancer treatments. However, the application of immune checkpoint inhibitors may entail severe side effects, with the risk of therapeutic resistance. The generation of chimeric antigen receptor (CAR) T-cells or CAR-NK cells requires specialized molecular laboratories, is costly, and is difficult to adapt to the rapidly growing number of cancer patients. To provide a simpler but effective immune therapy, a whole-cell tumor vaccine protocol was established based on ultraviolet C (UCV)-irradiated 4T1 triple-negative breast cancer cells. The apoptosis of tumor cells after UVC irradiation was verified using resazurin and Annexin V/propidium iodide flow cytometric assays. Protective immunity was achieved in immunized BALB/c mice, showing partial remission. Adoptive transfer of splenocytes or plasma from the mice in remission showed a protective effect in the naive BALB/c mice that received a living 4T1 tumor cell injection. 4T1-specific IgG antibodies were recorded in the plasma of the mice following immunization with the whole-cell vaccine. Interleukin-2 (IL-2) and oligonucleotide 2006 (ODN2006) adjuvants were used for the transfer of splenocytes from C57BL/6 mice into cyclophosphamide-treated BALB/c mice, resulting in prolonged survival, reduced tumor growth, and remission in 33% of the cases, without the development of the graft-versus-host disease. Our approach offers a simple, cost-effective whole-cell vaccine protocol that can be administered to immunocompetent healthy organisms. The plasma or the adoptive transfer of HLA-matching immunized donor-derived leukocytes could be used as an immune cell therapy for cancer patients.

Mannan-binding lectin reduces CpG DNA-induced inflammatory cytokine production by human monocytes

Mannan-binding lectin (MBL) belongs to the collectin family and functions as an opsonin that can also initiate complement activation. Our previous study showed that MBL serves as a double-stranded RNA binding protein that attenuates polyriboinosinic-polyribocytidylic acid-induced TLR3 activation. Prompted by these findings, in the present study cross-talk between MBL and CpG-DNA-induced TLR9 activation was investigated. Here, it was found that MBL also interacts with the TLR9 agonist, CpG oligodeoxynucleotide (CpG-ODN), in a calcium-dependent manner. Purified MBL protein suppressed activation of nuclear factor-kappa B signaling and subsequent production of proinflammatory cytokines from human monocytes induced by CpG-ODN 2006. These observations indicate that MBL can down-regulate CpG DNA-induced TLR9 activation, emphasizing the importance of understanding the interaction of MBL with TLR agonist in host immune defense.

Soluble human TLR2 ectodomain binds diacylglycerol from microbial lipopeptides and glycolipids

TLRs are key innate immune receptors that recognize conserved features of biological molecules that are found in microbes. In particular, TLR2 has been reported to be activated by different kinds of microbial ligands. To advance our understanding of the interaction of TLR2 with its ligands, the recombinant human TLR2 ectodomain (hTLR2ED) was expressed using a baculovirus/insect cell expression system and its biochemical, as well as ligand binding, properties were investigated. The hTLR2ED binds synthetic bacterial and mycoplasmal lipopeptides, lipoteichoic acid from Staphylococcus aureus, and synthetic lipoarabinomannan precursors from Mycobacterium at extracellular physiological conditions, in the absence of its co-receptors TLR1 and TLR6. We also determined that lipopeptides and glycolipids cannot bind simultaneously to hTLR2ED and that the phosphatidyl inositol mannoside 2 (Pim2) is the minimal lipoarabinomannan structure for binding to hTLR2ED. Binding of hTLR2ED to Pim4, which contains a diacylglycerol group with one of its acyl chains containing 19 carbon atoms, indicates that hTLR2ED can bind ligands with acyl chains longer than 16 carbon atoms. In summary, our data indicate that diacylglycerol is the ligand moiety of microbial glycolipids and lipoproteins that bind to hTLR2ED and that both types of ligands bind to the same binding site of hTLR2ED.

Duration of immunity against Mycobacterium bovis following neonatal vaccination with bacillus Calmette-Guérin Danish: significant protection against infection at 12, but not 24, months

Vaccination of neonatal calves with Mycobacterium bovis bacillus Calmette-Guérin (BCG) induces a significant degree of protection against bovine tuberculosis, caused by infection with virulent M. bovis. In two independent experiments, we assessed the duration of the protective immunity induced in calves by neonatal vaccination with BCG Danish. Protection from disease was assessed at 12 and 24 months postvaccination in cattle challenged via the endotracheal route with M. bovis. We also assessed antigen-specific immune responses to assess their utility as correlates of protection. At 12 months postvaccination, significant reductions in lung and lymph node pathologies were observed compared to nonvaccinated M. bovis-challenged control cattle. At 24 months post-BCG vaccination, there was a reduction in lung and lymph node pathology scores and in bacterial burden. However, when comparing vaccinated and control groups, this did not reach statistical significance. Vaccination induced long-lived antigen (purified protein derivative [PPD])-specific gamma interferon (IFN-γ) release in whole-blood cultures, which remained above baseline levels for more than 20 months (approximately 90 weeks). The number of antigen-specific IFN-γ-secreting central memory T cells present at the time of M. bovis challenge was significantly higher in vaccinated than in control animals at 12 months postvaccination, but not at 24 months. Vaccination of neonatal calves with BCG Danish induced protective immune responses against bovine TB which were maintained for at least 12 months postvaccination. These studies provide data on the immunity induced by BCG vaccination in calves; the results could inform vaccination strategies for the control of bovine TB in United Kingdom cattle herds.

CD4 T cell antigens from Staphylococcus aureus Newman strain identified following immunization with heat-killed bacteria

Staphylococcus aureus is a commensal bacterium associated with the skin and mucosal surfaces of humans and animals that can also cause chronic infection. The emergence of antibiotic-resistant strains such as methicillin-resistant S. aureus (MRSA) and strains causing chronic intramammary infections (IMI) in cows results in severe human and livestock infections. Conventional approaches to vaccine development have yielded only a few noneffective vaccines against MRSA or IMI strains, so there is a need for improved vaccine development. CD4 T lymphocytes are required for promoting gamma interferon (IFN-γ) mediated immunoglobulin isotype switching in B lymphocytes to produce high-affinity IgG antibodies and IFN-γ-mediated phagocyte activation for an effective resolution of bacterial infection. However, the lack of known CD4 T cell antigens from S. aureus has made it difficult to design effective vaccines. The goal of this study was to identify S. aureus proteins recognized by immune CD4 T cells. Using a reverse genetics approach, 43 antigens were selected from the S. aureus Newman strain. These included lipoproteins, proteases, transcription regulators, an alkaline shock protein, conserved-domain proteins, hemolysins, fibrinogen-binding protein, staphylokinase, exotoxin, enterotoxin, sortase, and protein A. Screening of expressed proteins for recall T cell responses in outbred, immune calves identified 13 proteins that share over 80% sequence identity among MRSA or IMI strains. These may be useful for inclusion in a broadly protective multiantigen vaccine against MRSA or IMI.

Cytosine-phosphate-guanine oligodeoxynucleotides containing GACGTT motifs enhance the immune responses elicited by keyhole limpet hemocyanin antigen in dairy cattle

Adjuvants are important components of vaccine formulations. Effective adjuvants line innate and adaptive immunity by signaling through pathogen recognition receptors. Synthetic cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs) have been shown to have potentials as adjuvants for vaccines. However, the immunostimulatory effect of CpG is species-specific and depends on the sequence of CpG motifs. A CpG ODN (2135), containing 3 identical copies of GTCGTT motif, was previously reported to have the strongest effects on bovine peripheral blood mononuclear cells (PBMC). Based on the sequence of 2135, we replaced the GTCGTT motif with 11 other sequences containing CG and investigated their effects on bovine lymphocyte proliferation. Results showed that the CpG ODNs containing 3 copies of GACGTT motif had the highest lymphocyte stimulation index (7.91±1.18), which was significantly (P<0.05) higher than that of 2135 (4.25±0.56). The CpG ODNs containing 3 copies of GACGTT motif also significantly increased the mRNA expression of interferon (IFN)-α, interleukin (IL)-12, and IL-21 in bovine PBMC. When dairy cows were immunized with the keyhole limpet hemocyanin (KLH) antigen formulated with CpG ODNs containing 3 copies of GACGTT, production of KLH-specific antibodies in serum and in milk whey was significantly (P<0.05) enhanced. IFN-γ in whole blood stimulated by KLH was also significantly (P<0.05) increased in cows immunized with KLH plus CpG ODNs. Our results indicate that CpG ODNs containing 3 copies of the GACGTT motifs is a potential adjuvant for bovine vaccines.

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

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

Identification of surrogates and correlates of protection in protective immunity against Mycobacterium bovis infection induced in neonatal calves by vaccination with M. bovis BCG Pasteur and M. bovis BCG Danish

Vaccination of neonatal calves with Mycobacterium bovis bacillus Calmette-Guérin (BCG) induces a significant degree of protection against infection with virulent M. bovis, the causative agent of bovine tuberculosis (bTB). We compared two strains of BCG, Pasteur and Danish, in order to confirm that the current European human vaccine strain (BCG Danish) induced protective immunity in calves, and we assessed immune responses to determine correlates of protection that could assist future vaccine evaluation in cattle. Both vaccine strains induced antigen (purified protein derivate [PPD])-specific gamma interferon (IFN-γ) in whole-blood cultures. These responses were not significantly different for BCG Pasteur and BCG Danish and peaked at week 2 to 4 postvaccination. Vaccination with either BCG Danish or BCG Pasteur induced significant protection against bTB, with reductions in both lesion score and bacteriological burden evident in both groups of vaccinated calves compared with nonvaccinated control calves. Measurement of IFN-γ-expressing T lymphocytes postvaccination and postchallenge revealed both correlates and surrogates of protective efficacy. The frequency of central memory T lymphocytes present at 12 weeks postvaccination (at the time of M. bovis challenge) correlated significantly with protection. Conversely, the number of IFN-γ-expressing effector T cells present after M. bovis challenge was correlated with disease. These results demonstrate that vaccination of neonatal calves with either BCG Pasteur or BCG Danish induces protective immune responses against TB. In addition, we show that measurement of antigen-specific T lymphocyte populations may provide a reliable means for identifying protective vaccine candidates.

Kinome analysis of Toll-like receptor signaling in bovine monocytes

The Toll-like receptors (TLRs) are a family of pathogen recognition receptors that alert the host to the presence of microbial challenge. Each TLR responds to a specific microbial associated ligand. For example, TLR4 is activated by lipopolysaccharide (LPS), whereas TLR9 responds to microbial DNA (CpGs). In this report signal transduction responses of bovine monocytes to stimulation with LPS and CpG are described through a bovine-specific peptide array. In addition to confirming activation of the defined TLR pathway in bovine cells, unique phosphorylation events not previously attributed to TLR signaling are described and validated. For example, array data predicts phosphorylation of Tyr40 of Etk in response to LPS, but not CpG, stimulation as well as the activation of oxidative burst in CpG, but not LPS. This investigation confirms interspecies conservation of the TLR pathway in bovine as well as providing insight into the complexity and mechanisms of TLR signaling.

CpG motif-based adjuvant as a replacement for Freund's complete adjuvant in a recombinant LHRH vaccine

This study compared: (1) Freund's complete adjuvant and CpG oligodeoxynucleotide (ODN) 2006 in water-in-oil emulsion as adjuvants; and (2) increasing doses of a recombinant ovalbumin-LHRH (ova-LHRH) fusion protein as an antigen for a contraceptive vaccine. Treatment groups (n=8 heifers/group) were: one untreated control group; five groups receiving CpG ODN with different doses of ova-LHRH (1.5; 2.3; 3.4; 5.1; and 7.6 mg); and one group receiving 3.4 mg ova-LHRH in Freund's. Heifers were immunized at weeks 0 and 14. All vaccine treatments caused gonadal regression and estrus suppression. CpG ODN is a suitable replacement for Freund's for LHRH immunization.

Aluminum is a potential environmental factor for Crohn's disease induction: extended hypothesis

Aluminum (Al) is a common environmental compound with immune-adjuvant activity and granulomatous inflammation inducer. Al exposure in food, additives, air, pharmaceuticals, and water pollution is ubiquitous in Western culture. Crohn's disease (CD) is a chronic relapsing intestinal inflammation in genetically susceptible individuals and is influenced by yet unidentified environmental factors. It is hypothesized, in the present review, that Al is a potential factor for induction or maintaining the inflammation in CD. Epidemiologically, CD incidence is higher in urban areas, where microparticle pollution is prevalent. Al immune activities share many characteristics with the immune pathology of CD: increased antigen presentation and APCs activation, many luminal bacterial or dietary compounds can be adsorbed to the metal and induce Th1 profile activity, promotion of humoral and cellular immune responses, proinflammatory, apoptotic, oxidative activity, and stress-related molecule expression enhancement, affecting intestinal bacterial composition and virulence, granuloma formation, colitis induction in an animal model of CD, and terminal ileum uptake. The Al-bacterial interaction, the microparticles homing the intestine together with the extensive immune activity, put Al as a potential environmental candidate for CD induction and maintenance.

CpG-ODN enhances mammary gland defense during mastitis induced by Escherichia coli infection in goats

Seven healthy native goats in early lactation, weighing 30-40 kg, were used in this study. The right mammary gland of the seven does were infused with CpG-ODN at a dosage of 100 microg kg(-1) body weight on the day 5 postpartum (PP). The left glands were used as controls and infused with sterile phosphate-buffered saline (PBS). On day 8 PP, the same dosage of CpG-ODN or PBS was again infused. On day 9 PP, the mammary glands (both right and left) of the seven does were infused with 6 x 10(6) colony-forming units (CFU) Escherichia coli and, at 0, 8, 16, 24, 48 and 72 h postinfection (PI), milk samples were collected from all glands. Goats were euthanized at 72 h PI and the mammary tissue harvested. Infusion with 6 x 10(6)CFU ml(-1)E. coli induced acute mastitis. Histopathological evaluations showed that polymorphonuclear neutrophils (PMNs) were still present in alveoli at 72 h PI, but PMNs in the CpG-ODN-treated glands has disappeared. Bacteria counts in milk peaked at 16 h PI and CpG-ODN induced a significant decrease in viable bacteria from 16 h PI until the end of the experiment. This study showed that CpG-ODN promoted the expression of its specific receptor (TLR-9 mRNA) in mammary tissue, stimulated IL-6 production, reduced bacteria counts in milk, attenuated the impact of inflammation mediators on cells and significantly shortened the inflammation course. These results suggest that the CpG-ODN improved mammary gland defense and, thereby, had a beneficial effects against mastitis caused by E. coli infection in goats.

The effectiveness of a CpG motif-based adjuvant (CpG ODN 2006) for LHRH immunization

A recombinant ovalbumin-luteinizing hormone-releasing hormone (ova-LHRH) antigen has been developed for immunocontraception. In this study, a novel immunostimulant for ova-LHRH immunization, CpG oligodeoxynucleotide (ODN) 2006, was compared against Mycobacterium butyricum. Also, the immunogenicity of ova-LHRH after lyophilization and exposure to organic solvents was assessed. Rats received either ova-LHRH solubilized in urea; lyophilized ova-LHRH; lyophilized ova-LHRH exposed to methylene chloride; or lyophilized ova-LHRH exposed to ethyl acetate. Immunogenicity of lyophilized ova-LHRH was reduced compared with solubilized ova-LHRH. Exposure to ethyl acetate further decreased immunogenicity of ova-LHRH. CpG ODN 2006 was a more effective immunostimulant than M. butyricum for LHRH immunization.

An ESAT-6:CFP10 DNA vaccine administered in conjunction with Mycobacterium bovis BCG confers protection to cattle challenged with virulent M. bovis

The potency of genetic immunization observed in the mouse has demonstrated the utility of DNA vaccines to induce cell-mediated and humoral immune responses. However, it has been relatively difficult to generate comparable responses in non-rodent species. The use of molecular adjuvants may increase the magnitude of these suboptimal responses. In this study, we demonstrate that the co-administration of plasmid-encoded GM-CSF and CD80/CD86 with a novel ESAT-6:CFP10 DNA vaccine against bovine tuberculosis enhances antigen-specific cell-mediated immune responses. ESAT-6:CFP10+GM-CSF+CD80/CD86 DNA vaccinated animals exhibited significant (p<0.01) antigen-specific proliferative responses compared to other DNA vaccinates. Increased expression (p< or =0.05) of CD25 on PBMC from ESAT-6:CFP10+GM-CSF+CD80/CD86 DNA vaccinates was associated with increased proliferation, as compared to control DNA vaccinates. Significant (p<0.05) numbers of ESAT-6:CFP10-specific IFN-gamma producing cells were evident from all ESAT-6:CFP10 DNA vaccinated animals compared to control DNA vaccinates. However, the greatest increase in IFN-gamma producing cells was from animals vaccinated with ESAT-6:CFP10+GM-CSF+CD80/CD86 DNA. In a low-dose aerosol challenge trial, calves vaccinated as neonates with Mycobacterium bovis BCG and ESAT-6:CFP10+GM-CSF+CD80/CD86 DNA exhibited decreased lesion severity in the lung and lung-associated lymph nodes following viruluent M. bovis challenge compared to other vaccinated animals or non-vaccinated controls. These data suggest that a combined vaccine regimen of M. bovis BCG and a candidate ESAT-6:CFP10 DNA vaccine may offer greater protection against tuberculosis in cattle than vaccination with BCG alone.

Immunogenicity of Anaplasma marginale type IV secretion system proteins in a protective outer membrane vaccine

Rickettsial pathogens in the genera Anaplasma and Ehrlichia cause acute infection in immunologically naive hosts and are major causes of tick-borne disease in animals and humans. Immunization with purified outer membranes induces protection against acute Anaplasma marginale infection and disease, and a proteomic and genomic approach recently identified 21 proteins within the outer membrane immunogen in addition to the well-characterized major surface proteins MSP1 to MSP5. Among the newly described proteins were the type IV secretion system (TFSS) proteins VirB9, VirB10, and conjugal transfer protein (CTP). In other gram-negative bacteria, TFSS proteins form channels, facilitate secretion of molecules, and are required for intracellular survival. However, TFSS proteins have not been explored as vaccine antigens. In this study we demonstrate that in Anaplasma marginale outer membrane-vaccinated cattle, VirB9, VirB10, and CTP are recognized by serum immunoglobulin G2 (IgG2) and stimulate memory T-lymphocyte proliferation and gamma interferon secretion. VirB9 induced the greatest proliferation in CD4+ T-cell lines, and VirB9-specific CD4+ T-cell clones responded to three A. marginale strains, confirming the VirB9-specific T-cell responses are directed against epitopes in the native protein. The three TFSS proteins are highly conserved with orthologous proteins in Anaplasma phagocytophilum, Ehrlichia chaffeensis, and Ehrlichia canis. Recognition of TFSS antigens by CD4+ T cells and by IgG2 from cattle immunized with the protective outer membrane fraction provides a rationale for including these proteins in development of vaccines against A. marginale and related pathogens.

DNA vaccine construct incorporating intercellular trafficking and intracellular targeting motifs effectively primes and induces memory B- and T-cell responses in outbred animals

We developed a vaccine construct in which a BVP22 domain and an invariant-chain major histocompatibility complex class II-targeting motif capable of enhancing dendritic cell antigen uptake and presentation were fused to a sequence encoding a B- and T-cell antigen from the Anaplasma marginale major surface protein 1a and tested whether this construct would prime and expand immune responses in outbred calves. A single inoculation with this construct effectively primed the immune responses, as demonstrated by a significant enhancement of CD4(+) T-cell proliferation compared to that in calves identically inoculated but inoculated with a DNA construct lacking the targeting domains and compared to that in calves inoculated with an empty vector. These proliferative responses were mirrored by priming and expansion of gamma interferon-positive CD4(+) T cells and immunoglobulin G responses against the linked B-cell epitope. Priming by the single immunization induced memory that underwent rapid recall following reexposure to the antigen. These results demonstrate that DNA vaccines targeting key intercellular and intracellular events significantly enhance priming and expansion and support the feasibility of single-dose DNA immunization in outbred populations.

Immunostimulatory CpG oligodeoxynucleotides enhance the induction of bovine CD4+ cytotoxic T-lymphocyte responses against the polymorphic immunodominant molecule of the protozoan parasite Theileria parva

Enhancement of the induction of cytotoxic T-cell responses by immunostimulatory CpG oligodeoxynucleotides has been described in humans and mouse models. The present study attempted to address whether CpG has a similar effect in cattle. Immunisation of cattle with a recombinant form of the polymorphic immunodominant molecule from Theileria parva emulsified with immunostimulatory CpG oligodeoxynucleotides in adjuvant had no effect on the induction of antibody responses including the isotype profile, but significantly enhanced the induction of cytolytic responses that were mediated by CD4+CD3+ T cells utilizing the perforin-granzyme pathway.

Quantitation of Anaplasma marginale major surface protein (MSP)1a and MSP2 epitope-specific CD4+ T lymphocytes using bovine DRB3*1101 and DRB3*1201 tetramers

Antigen-specific CD4+ T cells play a critical role in protective immunity to many infectious pathogens. Although the antigen-specific CD4+ T cells can be measured by functional assays such as proliferation or cytokine enzyme-linked immunospot, such assays are limited to a specific function and cannot quantify anergic or suppressed T cells. In contrast, major histocompatiblity complex (MHC) class II tetramers can enumerate epitope-specific CD4+ T cells independent of function. In this paper, we report the construction of bovine leukocyte antigen MHC class II tetramers using a novel mammalian cell system to express soluble class II DRA/DRB3 molecules and defined immunodominant peptide epitopes of Anaplasma marginale major surface proteins (MSPs). Phycoerythrin-labeled tetramers were either loaded with exogenous peptide or constructed with the peptide epitope linked to the N terminus of the DRB3 chain. A DRB3*1101 tetramer loaded with MSP1a peptide F2-5B (ARSVLETLAGHVDALG) and DRB3*1201 tetramers loaded with MSP1a peptide F2-1-1b (GEGYATYLAQAFA) or MSP2 peptide P16-7 (NFAYFGGELGVRFAF) specifically stained antigen-specific CD4+ T cell lines and clones. Tetramers constructed with the T-cell epitope linked to the DRB3 chain were slightly better at labeling CD4+ T cells. In one cell line, the number of tetramer-positive T cells increased to approximately 94% of the CD4+ T cells after culture for 21 weeks with specific antigen. This novel technology should be useful to track the fate of antigen-specific CD4+ T-cell responses in cattle after immunization or infection with persistent pathogens, such as A. marginale, that modulate the host immune response.

Immune control of Babesia bovis infection

Babesia bovis causes an acute and often fatal infection in adult cattle, which if resolved, leads to a state of persistent infection in otherwise clinically healthy cattle. Persistently infected cattle are generally resistant to reinfection with related parasite strains, and this resistance in the face of infection is termed concomitant immunity. Young animals are generally more resistant than adults to B. bovis infection, which is dependent on the spleen. Despite the discovery of B. bovis over a century ago, there are still no safe and effective vaccines that protect cattle against this most virulent of babesial pathogens. Immunodominant antigens identified by serological reactivity and dominant T-cell antigens have failed to protect cattle against challenge. This review describes the innate and acquired immune mechanisms that define resistance in young calves and correlate with the development of concomitant immunity in older cattle following recovery from clinical disease. The first sections will discuss the innate immune responses by peripheral blood- and spleen-derived macrophages in cattle induced by B. bovis merozoites and their products that limit parasite replication, and comparison of natural killer cell responses in the spleens of young (resistant) and adult (susceptible) cattle. Later sections will describe a proteomic approach to discover novel antigens, especially those recognized by immune CD4+ T lymphocytes. Because immunodominant antigens have failed to stimulate protective immunity, identification of subdominant antigens may prove to be important for effective vaccines. Identification of CD4+ T-cell immunogenic proteins and their epitopes, together with the MHC class II restricting elements, now makes possible the development of MHC class II tetramers and application of this technology to both quantify antigen-specific lymphocytes during infection and discover novel antigenic epitopes. Finally, with the imminent completion of the B. bovis genome-sequencing project, strategies using combined genomic and proteomic approaches to identify novel vaccine candidates will be reviewed. The availability of an annotated B. bovis genome will, for the first time, enable identification of non-immunodominant proteins that may stimulate protective immunity.

Recombinant bovine interleukin 2 enhances immunity and protection induced by Brucella abortus vaccines in cattle

Augmentation of immunization of cattle Brucella abortus S19 or a B. abortus soluble protein extract (SPEBA) vaccine through administration of recombinant bovine IL 2 (rBoIL 2) was evaluated. Seventy-five heifers were divided among 6 groups that were treated with the following: Group 1, no treatment; Group 2, rBoIL 2 (1microg/kg) on day 0; Group 3, SPEBA (2 mg) on day 0 and week 9; Group 4, SPEBA + rBoIL 2 on day 0, SPEBA on week 9; Group 5, S19 (10(7) CFU) on day 0 and week 9; Group 6, S19 + rBoIL 2 on day 0, S19 only on week 9. Approximately, 6 months after vaccination, cattle were bred by natural service, and at mid-gestation pregnant cattle were challenged intraconjunctivally with 9.1 x 10(5) CFU of virulent B. abortus S2308. Pre- and post-challenge antibody responses were measured by an enzyme-linked immunosorbent assay, a particle concentration fluorescence assay, and the card test. Lymphoproliferation (LP) responses to gamma-irradiated B. abortus and SPEBA antigens were measured in peripheral blood mononuclear cells. After vaccination, antibody responses to B. abortus elevated rapidly in SPEBA- and S19-vaccinates with and without rBoIL 2, however, these responses were significantly (P < 0.05) higher in vaccinates which also received rBoIL 2. Antibody levels for all vaccinated groups had returned to those of negative control groups by the challenge date with the exception of the SPEBA/rBoIL 2 group. In general, LP responses were higher in vaccinated or rBoIL 2-treated cattle than for unvaccinated controls. Challenge of 48 pregnant heifers resulted in abortions in 4/9 of Group 1, 0/9 of Group 2, 4/8 of Group 3, 2/9 of Group 4, 1/7 of Group 5, and 0/6 of Group 6 cattle. Treatment with rBoIL 2 alone (Group 2) provided significant (P < 0.05) protection from infection, abortions and induction of sero-positive status compared to untreated (Group 1) cattle. Co-administration of rBoIL 2 with S19 resulted in significant (P < 0.05) augmentation in onset, duration and magnitude of LP responses to B. abortus antigens following challenge. Characterization of the cytokine response of bovine monocyte-derived macrophages by real-time polymerase chain reaction indicated that in vitro stimulation of these cells with rBoIL 2 resulted in a profound up-regulation of genes encoding tumor necrosis factor-alpha, IL 12p40, and interferon-gamma reflecting activation of the cells. Overall, rBoIL 2-treatment was associated with fewer infections, sero-conversions and a significant (P = 0.02) level of protection against abortion as compared to vaccination alone or no treatment.

Immunostimulatory DNA activates production of type I interferons and interleukin-6 in equine peripheral blood mononuclear cells in vitro

This study aimed to evaluate different nucleic acid preparations as cytokine inducers in equine cells. To induce cytokine production, bacterial plasmid DNA or short synthetic oligodeoxyribonucleotides (ODN), with or without the transfection reagent lipofectin, were added to cultures of purified equine peripheral blood mononuclear cells (PBMC). Cytokine activity was detected with bioassays in cell culture supernatants after 24h of induction and cytokine mRNA expression was detected using RT-PCR at 6h post induction. For IFN-alpha/beta it was found that both plasmid DNA and phosphodiester ODN, containing an unmethylated CpG-motif, were able to induce IFN production in the presence of lipofectin but not without. The levels of IFN varied with individuals and were often quite low. Moreover, methylation or removal of the CpG sequence completely abolished IFN induction. CpG-containing ODN with poly-guanine (G) sequences in the 5' and 3' ends induced considerably higher levels of IFN, especially when the poly-G sequences had a phosphorothioate backbone. ODN with poly-G sequences also had the ability to induce IFN in the absence of lipofectin but the levels of IFN induced were radically reduced compared to those induced with lipofectin. In contrast to IFN, which was only detected upon induction, low spontaneous IL-6 production was observed in unstimulated control cultures. Nevertheless, plasmid DNA and CpG-containing ODN were able to increase the IL-6 production threefold. All the IFN inducing ODN also induced IL-6 production and the levels of IL-6 induced seemed influenced by addition of lipofectin and presence of poly-G sequences in the same way as was observed for the IFN-production. However, a complete phosphorothioate ODN with a central CpG-motif and poly-C sequences, that did not induce IFN, readily induced IL-6 both in the presence and absence of lipofectin. In addition, there was also evidence that some ODN induced increased expression of IL-12p40 mRNA. To conclude, equine PBMC were able to recognize CpG-DNA and respond with both IFN-alpha/beta and/or IL-6 production. The levels of cytokine induced, and sometimes which cytokine induced, varied with, e.g., CpG-motifs used, the presence of poly-G sequences, ODN backbone chemistry and presence of lipofectin.

A combined nucleocapsid vaccine induces vigorous SARS-CD8+ T-cell immune responses

Several studies have shown that cell-mediated immune responses play a crucial role in controlling viral replication. As such, a candidate SARS vaccine should elicit broad CD8+ T-cell immune responses. Several groups of mice were immunized alone or in combination with SARS-nucleocapsid immunogen. A high level of specific SARS-CD8+ T-cell response was demonstrated in mice that received DNA encoding the SARS-nucleocapsid, protein and XIAP as an adjuvant. We also observed that co-administration of a plasmid expressing nucleocapsid, recombinant protein and montanide/CpG induces high antibody titers in immunized mice. Moreover, this vaccine approach merits further investigation as a potential candidate vaccine against SARS.

Rapid and long-term disappearance of CD4+ T lymphocyte responses specific for Anaplasma marginale major surface protein-2 (MSP2) in MSP2 vaccinates following challenge with live A. marginale

In humans and ruminants infected with Anaplasma, the major surface protein 2 (MSP2) is immunodominant. Numerous CD4(+) T cell epitopes in the hypervariable and conserved regions of MSP2 contribute to this immunodominance. Antigenic variation in MSP2 occurs throughout acute and persistent infection, and sequentially emerging variants are thought to be controlled by variant-specific Ab. This study tested the hypothesis that challenge of cattle with Anaplasma marginale expressing MSP2 variants to which the animals had been immunized, would stimulate variant epitope-specific recall CD4(+) T cell and IgG responses and organism clearance. MSP2-specific T lymphocyte responses, determined by IFN-gamma ELISPOT and proliferation assays, were strong before and for 3 wk postchallenge. Surprisingly, these responses became undetectable by the peak of rickettsemia, composed predominantly of organisms expressing the same MSP2 variants used for immunization. Immune responsiveness remained insignificant during subsequent persistent A. marginale infection up to 1 year. The suppressed response was specific for A. marginale, as responses to Clostridium vaccine Ag were consistently observed. CD4(+)CD25(+) T cells and cytokines IL-10 and TGF-beta1 did not increase after challenge. Furthermore, a suppressive effect of nonresponding cells was not observed. Lymphocyte proliferation and viability were lost in vitro in the presence of physiologically relevant numbers of A. marginale organisms. These results suggest that loss of memory T cell responses following A. marginale infection is due to a mechanism other than induction of T regulatory cells, such as peripheral deletion of MSP2-specific T cells.

Therapeutic vaccination with papillomavirus E6 and E7 long peptides results in the control of both established virus-induced lesions and latently infected sites in a pre-clinical cottontail rabbit papillomavirus model

This study was performed to test the therapeutic efficacy of overlapping long E6 and E7 peptides, containing both CD4+ T-helper and CD8+ CTL epitopes, on CRPV-induced lesions, which is an appropriate pre-clinical model for HPV diseases, including recurrent respiratory papillomatosis (RRP). Therapeutic peptide vaccination was able to significantly control wart growth (p < 0.01) and abrogate latent CRPV infection (p = 0.0006) compared to controls. Vaccination was associated with a T(H)1 T cell response, as suggested by a strong DTH skin test, antigen-specific proliferation of PBMC and a minimal IgG antibody response. Thus, this study shows promise for treatment of RRP by vaccination with long peptides.

Development of detection methods for ruminant interleukin (IL)-4

Recombinant bovine IL-4 (rbo IL-4) was transiently expressed in COS-7 cells. Mice were immunised with a plasmid encoding rbo IL-4 and boosted with rbo IL-4. A number of monoclonal antibodies (mAb) were generated that reacted with rbo IL-4 in an ELISA and these cloned hybridomas were termed CC311, CC312, CC313 and CC314. A pair of mAb (CC313 and CC314) was identified that together could be used to detect both recombinant and native bovine IL-4 by ELISA and a luminometric detection method was applied to the ELISA. Using this method native bovine IL-4 was detected in supernatants of PBMC stimulated with mitogens. In addition, high level secretion of IL-4 by Fasciola hepatica specific Th2 clones, but not by a Babesia bovis specific Th1 clone, was confirmed. The ELISA was also able to detect recombinant ovine IL-4. The pair of mAb used for ELISA could also be used for the detection of IL-4 spot forming cells by ELISPOT. In addition intracytoplasmic expression of IL-4 could be detected. The ability to detect ruminant IL-4 by three methods: ELISA, ELISPOT and by flow cytometric analysis of intracytoplasmic expression will permit studies of the role of this important cytokine in the immunology and pathogenesis of animal diseases.

Identification of vaccine candidate peptides in the NcSRS2 surface protein of Neospora caninum by using CD4+ cytotoxic T lymphocytes and gamma interferon-secreting T lymphocytes of infected holstein cattle

Previously, our laboratory showed that Holstein cattle experimentally infected with Neospora caninum develop parasite-specific CD4+ cytotoxic T lymphocytes (CTL) that lyse infected, autologous target cells through a perforin-granzyme pathway. To identify specific parasite antigens inducing bovine CTL and helper T-lymphocyte responses for vaccine development against bovine neosporosis, the tachyzoite major surface proteins NcSAG1 and NcSRS2 were targeted. In whole tachyzoite antigen-expanded bovine T-lymphocyte lines, recombinant NcSRS2 induced potent memory CD4+- and CD8+-T-lymphocyte activation, as indicated by proliferation and gamma interferon (IFN-gamma) secretion, while recombinant NcSAG1 induced a minimal memory response. Subsequently, T-lymphocyte epitope-bearing peptides of NcSRS2 were mapped by using overlapping peptides covering the entire NcSRS2 sequence. Four experimentally infected cattle with six different major histocompatibility complex (MHC) class II haplotypes were the source of immune cells used to identify NcSRS2 peptides presented by Holstein MHC haplotypes. NcSRS2 peptides were mapped by using IFN-gamma secretion by rNcSRS2-stimulated, short-term T-lymphocyte cell lines, IFN-gamma enzyme-linked immunospot (ELISPOT) assay with peripheral blood mononuclear cells, and 51Cr release cytotoxicity assay of rNcSRS2-stimulated effector cells. Four N. caninum-infected Holstein cattle developed NcSRS2 peptide-specific T lymphocytes detected ex vivo in peripheral blood by IFN-gamma ELISPOT and in vitro by measuring T-lymphocyte IFN-gamma production and cytotoxicity. An immunodominant region of NcSRS2 spanning amino acids 133 to 155 was recognized by CD4+ T lymphocytes from the four cattle. These findings support investigation of subunit N. caninum vaccines incorporating NcSRS2 gene sequences or peptides for induction of NcSRS2 peptide-specific CTL and IFN-gamma-secreting T lymphocytes in cattle with varied MHC genotypes.

Vaccination of neonatal calves with Mycobacterium bovis BCG induces protection against intranasal challenge with virulent M. bovis

Vaccination of neonates with Mycobacterium bovis bacillus Calmette-Guerin (BCG) may be a strategy that overcomes reduced vaccine efficacy associated with exposure to environmental mycobacteria in humans and cattle. Preliminary comparisons indicated that 2-week-old calves produced an immune response to vaccination at least as intense as that observed in adults. Subsequently, five gnotobiotic hysterotomy derived calves aged 1 day were inoculated with BCG and 3 months later were challenged intranasally with virulent M. bovis. The number of tissues with lesions and the pathological extent of these lesions was reduced significantly in vaccinates. Furthermore, lesions were evident in the lung or associated chest lymph nodes of four of five controls but none of five vaccinates. BCG vaccination reduced significantly the level of bacterial colonization. However, lesions in the head associated lymph nodes were observed in three of five BCG-vaccinated cattle. Levels of interferon gamma (IFN-gamma) detected by enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunospot (ELISPOT) in individual vaccinated animals at challenge did not correlate with subsequent resistance and in general immune responses post-challenge were lower in vaccinated calves. Low IL-10 responses were evident but IL-4 was not detected. Responses to ESAT-6 and/or CFP-10 were evident in four of four control calves that had lesions. Two of the BCG vaccinates with lesions did not produce a response to ESAT-6 and CFP-10, indicating that these antigens did not distinguish vaccinated immune animals from vaccinated animals with lesions. Overall, vaccination of neonatal calves with BCG induced significant protection against disease and has potential as a strategy for the reduction of the incidence of bovine tuberculosis.

Anaplasma marginale major surface protein 2 CD4+-T-cell epitopes are evenly distributed in conserved and hypervariable regions (HVR), whereas linear B-cell epitopes are predominantly located in the HVR

Organisms in the genus Anaplasma express an immunodominant major surface protein 2 (MSP2), composed of a central hypervariable region (HVR) flanked by highly conserved regions. Throughout Anaplasma marginale infection, recombination results in the sequential appearance of novel MSP2 variants and subsequent control of rickettsemia by the immune response, leading to persistent infection. To determine whether immune evasion and selection for variant organisms is associated with a predominant response against HVR epitopes, T-cell and linear B-cell epitopes were localized by measuring peripheral blood gamma interferon-secreting cells, proliferation, and antibody binding to 27 overlapping peptides spanning MSP2 in 16 cattle. Similar numbers of MSP2-specific CD4(+) T-cell epitopes eliciting responses of similar magnitude were found in conserved and hypervariable regions. T-cell epitope clusters recognized by the majority of animals were identified in the HVR (amino acids [aa] 171 to 229) and conserved regions (aa 101 to 170 and 272 to 361). In contrast, linear B-cell epitopes were concentrated in the HVR, residing within hydrophilic sequences. The pattern of recognition of epitope clusters by T cells and of HVR epitopes by B cells is consistent with the influence of protein structure on epitope recognition.

CD80 and CD86, but not CD154, augment DNA vaccine-induced protection in experimental bovine tuberculosis

DNA vaccination is known to elicit robust cellular and humoral responses to encoded antigen. The co-administration of costimulatory molecules CD80 (B7-1), CD86 (B7-2) and CD154 (CD40L) has been shown to enhance immune responses in several murine models. The role of specific costimulatory molecules in non-rodent species remains incompletely characterized. In these studies, we demonstrate that the co-administration of CD80 and CD86, but not CD154, to an existing candidate subunit DNA vaccine (ESAT-6) against bovine tuberculosis, enhances protection after aerosol challenge with virulent Mycobacterium bovis. Additionally, we have shown that vaccination with M. bovis BCG is protective against tuberculosis following aerosol challenge in cattle. Two independent trials were conducted in cattle to determine the adjuvant effect of encoded antigen + CD80/CD86 and directly compare the adjuvant activities of CD80/CD86 to those of CD154. Co-administration of either CD80/CD86 or CD154 enhanced ESAT-6-specific IFN-gamma responses as compared to animals vaccinated with ESAT-6 DNA alone. However, following aerosol challenge, only animals vaccinated with CD80/CD86 possessed decreased pathology of the lungs and associated lymph nodes, as measured by gross examination, radiographic lesion morphometry and bacterial recovery. Collectively, these results demonstrate that the co-administration of costimulatory molecules with a protective antigen target enhances bovine immune responses to DNA vaccination, and that CD80/CD86 is superior to CD154 in augmenting DNA vaccine-induced protection in experimental bovine tuberculosis.

Toll-like receptor 9 is expressed on follicle-associated epithelia containing M cells in swine Peyer's patches

The precise distribution and expression of Toll-like receptor (TLR) 9 in gut-associated lymphoid tissues (GALTs) has not been elucidated. In this study, we investigated the expression pattern of TLR9 in adult and neonatal swine GALTs by real-time quantitative PCR, western blot, confocal laser microscopy and flow cytometric analysis. The swine TLR9 gene was preferentially expressed in adult Peyer's patches (Pps) and mesenteric lymph nodes (MLNs), which contained approximately three times higher TLR9 than the spleen. Other tissues exhibited only weak expression of TLR9. In neonatal swine, elevated expression of TLR9 was detected only in MLNs. We firstly showed that highly expressive (TLR9(+)) cells were formed in Pps and MLNs. In addition, TLR9(+) cells were present not only in immune cells such as dendritic cells and B cells but also in follicle-associated epithelia (FAE) including membranous cells (M cells) in Pps. These results suggest that Pps and MLNs provide the host defense with the ability to respond to a variety of bioactive oligonucleotides (ODNs) from bacteria at a conductive site of initial immune responses.

The CD4 + T cell immunodominant Anaplasma marginale major surface protein 2 stimulates γδ T cell clones that express unique T cell receptors

Major surface protein 2 (MSP2) of the bovine rickettsial pathogen Anaplasma marginale is an abundant, serologically immunodominant outer membrane protein. Immunodominance partially results from numerous CD4+ T cell epitopes in highly conserved amino and carboxy regions and the central hypervariable region of MSP2. However, in long-term cultures of lymphocytes stimulated with A. marginale, workshop cluster 1 (WC1)+ gammadelta T cells and CD4+ alphabeta T cells proliferated, leading to a predominance of gammadelta T cells. As gammadelta T cells proliferate in A. marginale-stimulated lymphocyte cultures, this study hypothesized that gammadelta T cells respond to the abundant, immunodominant MSP2. To test this hypothesis, gammadelta T cell clones were isolated from MSP2 vaccinates and assessed for antigen-specific proliferation and interferon-gamma secretion. Seven WC1+ gammadelta T cell clones responded to A. marginale and MSP2, and three of these proliferated to overlapping peptides from the conserved carboxy region. The gammadelta T cell response was not major histocompatibility complex-restricted, although it required antigen-presenting cells and was blocked by addition of antibody specific for the T cell receptor (TCR). Sequence analysis of TCR-gamma and -delta chains of peripheral blood lymphocytes identified two novel TCR-gamma chain constant (Cgamma) regions. It is important that all seven MSP2-specific gammadelta T cell clones used the same one of these novel Cgamma regions. The TCR complementarity-determining region 3 was less conserved than those of MSP2-specific CD4+ alphabeta T cell clones. Together, these data indicate that WC1+ gammadelta T cells recognize A. marginale MSP2 through the TCR and contribute to the immunodominant response to this protein.

Adjuvant synergy: The effects of nasal coadministration of adjuvants

Modern peptide and protein subunit vaccines suffer from poor immunogenicity and require the use of adjuvants. However, none of the currently licensed adjuvants can elicit cell-mediated immunity or are suitable for mucosal immunization. In this study we explored the immunological effect of nasal co-administration of adjuvants with distinct functions: cholera toxin subunit B, a potent mucosal adjuvant that induces strong humoral responses, muramy di-peptide (MDP), an adjuvant known to elicit cell mediated immunity but rarely used nasally, and chitosan, an adjuvant that achieves specific physiological effects on mucosal membranes that improve antigen uptake. Groups of five female BALB/c mice received on days 1 and 56 nasal instillations of the recombinant Helicobacter pylori antigen urease admixed to single or multiple adjuvant combinations. Serum IgG kinetics were followed over 24 weeks. At the conclusion of the experiment, local antibody responses were determined and antigen-specific recall responses in splenocyte cultures were assayed for proliferation and cytokine production. The combination of adjuvants was shown to further contribute to the increased antigenicity of recombinant H. pylori urease. The data presented here outline and support facilitation of increased immunomodulation by an adjuvant previously defined as an effective mucosal adjuvant (chitosan) for another adjuvant (MDP) that is not normally effective via this route.

Conservation of Babesia bovis small heat shock protein (Hsp20) among strains and definition of T helper cell epitopes recognized by cattle with diverse major histocompatibility complex class II haplotypes

Babesia bovis small heat shock protein (Hsp20) is recognized by CD4+ T lymphocytes from cattle that have recovered from infection and are immune to challenge. This candidate vaccine antigen is related to a protective antigen of Toxoplasma gondii, Hsp30/bag1, and both are members of the alpha-crystallin family of proteins that can serve as molecular chaperones. In the present study, immunofluorescence microscopy determined that Hsp20 is expressed intracellularly in all merozoites. Importantly, Hsp20 is also expressed by tick larval stages, including sporozoites, so that natural tick-transmitted infection could boost a vaccine-induced response. The predicted amino acid sequence of Hsp20 from merozoites is completely conserved among different B. bovis strains. To define the location of CD4+ T-cell epitopes for inclusion in a multiepitope peptide or minigene vaccine construct, truncated recombinant Hsp20 proteins and overlapping peptides were tested for their ability to stimulate T cells from immune cattle. Both amino-terminal (amino acids [aa] 1 to 105) and carboxy-terminal (aa 48 to 177) regions were immunogenic for the majority of cattle in the study, stimulating strong proliferation and IFN-gamma production. T-cell lines from all individuals with distinct DRB3 haplotypes responded to aa 11 to 62 of Hsp20, which contained one or more immunodominant epitopes for each animal. One epitope, DEQTGLPIKS (aa 17 to 26), was identified by T-cell clones. The presence of strain-conserved T helper cell epitopes in aa 11 to 62 of the ubiquitously expressed Hsp20 that are presented by major histocompatibility complex class II molecules represented broadly in the Holstein breed supports the inclusion of this region in vaccine constructs to be tested in cattle.

Stimulation of T-helper cell gamma interferon and immunoglobulin G responses specific for Babesia bovis rhoptry-associated protein 1 (RAP-1) or a RAP-1 protein lacking the carboxy-terminal repeat region is insufficient to provide protective immunity against virulent B. bovis challenge

Rhoptry-associated protein 1 (RAP-1) is a targeted vaccine antigen for Babesia bovis and Babesia bigemina infections of cattle. The 60-kDa B. bovis RAP-1 is recognized by antibodies and T lymphocytes from cattle that recovered from infection and were immune to subsequent challenge. Immunization with native or recombinant protein was reported to reduce parasitemias in challenged animals. We recently reported that the NT domain of B. bovis RAP-1 contained immunodominant T-cell epitopes, whereas the repeat-rich CT domain was less immunostimulatory for T lymphocytes from cattle immune to B. bovis. The present study was therefore designed to test the hypothesis that the NT region of RAP-1, used as a vaccine with interleukin-12 and RIBI (catalog no. R-730; RIBI Immunochem Research, Inc., Hamilton, Mont. [now Corixa, Seattle, Wash.]) adjuvant to induce a type 1 response, would prime calves for antibody and T-helper cell responses comparable to or greater than those induced by full-length RAP-1 containing the C-terminal repeats. Furthermore, a type 1 immune response to RAP-1 was hypothesized to induce protection against challenge. Following four inoculations of either recombinant full-length RAP-1 or RAP-1 NT protein, RAP-1-specific immunoglobulin G (IgG) titers, T-lymphocyte proliferation, and gamma interferon production were similar. Similar numbers of NT region peptides were recognized. However, in spite of the presence of strong RAP-1-specific IgG and CD4(+)-T-lymphocyte responses that were recalled upon challenge, neither antigen stimulated a protective immune response. We conclude that successful priming of calves with recombinant RAP-1 and adjuvants that elicit strong Th1 cell and IgG responses is insufficient to protect calves against virulent B. bovis challenge.