Effects of type I/type II interferons and transforming growth factor-beta on B-cell differentiation and proliferation. Definition of costimulation and cytokine requirements for immunoglobulin synthesis and expression

Elicitation of Highly Pathogenic Avian Influenza H5N1 M2e and HA2-Specific Humoral and Cell-Mediated Immune Response in Chicken Following Immunization With Recombinant M2e-HA2 Fusion Protein

The study was aimed to evaluate the elicitation of highly pathogenic avian influenza (HPAI) virus (AIV) M2e and HA2-specific immunity in chicken to develop broad protective influenza vaccine against HPAI H5N1. Based on the analysis of Indian AIV H5N1 sequences, the conserved regions of extracellular domain of M2 protein (M2e) and HA2 were identified. Synthetic gene construct coding for M2e and two immunodominant HA2 conserved regions was designed and synthesized after codon optimization. The fusion recombinant protein (~38 kDa) was expressed in a prokaryotic system and characterized by Western blotting with anti-His antibody and anti-AIV polyclonal chicken serum. The M2e–HA2 fusion protein was found to be highly reactive with known AIV-positive and -negative chicken sera by ELISA. Two groups of specific pathogen-free (SPF) chickens were immunized (i/m) with M2e synthetic peptide and M2e–HA2 recombinant protein along with one control group with booster on the 14th day and 28th day with the same dose and route. Pre-immunization sera and whole blood were collected on day 0 followed by 3, 7, 14, 21, and 28 days and 2 weeks after the second booster (42 day). Lymphocyte proliferation assay by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) method revealed that the stimulation index (SI) was increased gradually from days 0 to 14 in the immunized group (p < 0.05) than that in control chicken. Toll-like receptor (TLR) mRNA analysis by RT-qPCR showed maximum upregulation in the M2e–HA2-vaccinated group compared to M2e- and sham-vaccinated groups. M2e–HA2 recombinant protein-based indirect ELISA revealed that M2e–HA2 recombinant fusion protein has induced strong M2e and HA2-specific antibody responses from 7 days post-primary immunization, and then the titer gradually increased after booster dose. Similarly, M2e peptide ELISA revealed that M2e–HA2 recombinant fusion protein elicited M2e-specific antibody from day 14 onward. In contrast, no antibody response was detected in the chicken immunized with synthetic peptide M2e alone or control group. Findings of this study will be very useful in future development of broad protective H5N1 influenza vaccine targeting M2e and HA2.

Gene gun DNA immunization of cattle induces humoral and CD4 T-cell-mediated immune responses against the Theileria parva polymorphic immunodominant molecule

Theileria parva kills over one million cattle annually in sub-Saharan Africa. Parasite genetic complexity, cellular response immunodominance, and bovine MHC diversity have precluded traditional vaccine development. One potential solution is gene gun (GG) immunization, which enables simultaneous administration of one or more DNA-encoded antigens. Although promising in murine, porcine, and human vaccination trials, bovine GG immunization studies are limited. We utilized the model T. parva antigen, polymorphic immunodominant molecule (PIM) to test bovine GG immunization. GG immunization using a mammalian codon optimized PIM sequence elicited significant anti-PIM antibody and cell-mediated responses in 7/8 steers, but there was no difference between immunized and control animals following T. parva challenge. The results suggest immunization with PIM, as delivered here, is insufficient to protect cattle from T. parva. Nonetheless, the robust immune responses elicited against this model antigen suggest GG immunization is a promising vaccine platform for T. parva and other bovine pathogens.

Serum and colostral antibody production in cows immunized with recombinant human tumor necrosis factor

The use of hyper-immune bovine colostrum as a human therapeutic platform is an emerging technology with potential to deliver the efficacy of antibody therapeutics with the convenience and safety of oral or topical application. It is necessary to understand how the bovine immune system responds to immunization with foreign proteins, both in terms of the serum antibody response and the transfer of antigen-specific antibodies into the colostrum to enable efficient large-scale production of therapeutic antibodies. We have immunized 25 cows with recombinant human tumor necrosis factor (rhTNF) and measured the levels of rhTNF-specific antibodies in the serum and colostrum of these animals. We observed a decline of 84±9% in serum IgG1 concentrations in the final weeks of pregnancy that presumably reflects rapid transport of IgG1 into colostrum. The serum IgG2 levels remained constant, such that the serum IgG1 to IgG2 ratio was 1:20 at parturition. We observed substantial animal-to-animal variability in the levels of anti-rhTNF antibodies in both serum and colostrum samples. In particular, a subset of 4 cows had extraordinarily high colostral anti-rhTNF antibody production. Only a weak correlation was found between the peak serum anti-rhTNF activity and the colostral anti-rhTNF activity in these animals. The 4 cows with high colostral anti-rhTNF activities trended toward higher serum IgG1 loss relative to average colostral anti-rhTNF producers, but this difference was not statistically significant in this small sample. The high-anti-rhTNF-producing cows also exhibited a greater proportion of rhTNF-specific antibodies that bound to bovine IgG1- and IgG2-specific detection antibodies relative to the total anti-rhTNF immunoglobulin population. This finding suggests that the isotype distribution of the anti-rhTNF response is varied between individuals and genetic or environmental factors may increase the yield of antigen-specific colostral antibodies.

Resilience in farm animals: biology, management, breeding and implications for animal welfare

A capacity for the animal to recover quickly from the impact of physical and social stressors and disease challenges is likely to improve evolutionary fitness of wild species and welfare and performance of farm animals. Salience and valence of stimuli sensed through neurosensors, chemosensors and immunosensors are perceived and integrated centrally to generate emotions and engage physiological, behavioural, immune, cognitive and morphological responses that defend against noxious challenges. These responses can be refined through experience to provide anticipatory and learned reactions at lower cost than innate less-specific reactions. Influences of behaviour type, coping style, and affective state and the relationships between immune responsiveness, disease resistance and resilience are reviewed. We define resilience as the capacity of animals to cope with short-term perturbations in their environment and return rapidly to their pre-challenge status. It is manifested in response to episodic, sporadic or situation-specific attributes of the environment and can be optimised via facultative learning by the individual. It is a comparative measure of differences between individuals in the outcomes that follow exposure to potentially adverse situations. In contrast, robustness is the capacity to maintain productivity in a wide range of environments without compromising reproduction, health and wellbeing. Robustness is manifested in response to persistent or cyclical attributes of the environment and is effected via activity of innate regulatory pathways. We suggest that for farm animals, husbandry practices that incorporate physical and social stressors and interactions with humans such as weaning, change of housing, and introduction to the milking parlour can be used to characterise resilience phenotypes. In these settings, resilience is likely to be more readily identified through the rate of return of variables to pre-challenge or normal status rather than through measuring the activity of diverse stress response and adaptation mechanisms. Our strategy for phenotyping resilience of sheep and cattle during weaning is described. Opportunities are examined to increase resilience through genetic selection and through improved management practices that provide emotional and cognitive enrichment and stress inoculation.

Bacterial Ghosts of Escherichia coli Drive Efficient Maturation of Bovine Monocyte-Derived Dendritic Cells

Bacterial ghosts (BGs) are empty cell envelopes derived from Gram-negative bacteria. They not only represent a potential platform for development of novel vaccines but also provide a tool for efficient adjuvant and antigen delivery system. In the present study, we investigated the interaction between BGs of Escherichia coli (E. coli) and bovine monocyte-derived dendritic cells (MoDCs). MoDCs are highly potent antigen-presenting cells and have the potential to act as a powerful tool for manipulating the immune system. We generated bovine MoDCs in vitro from blood monocytes using E. coli expressed bovine GM-CSF and IL-4 cytokines. These MoDCs displayed typical morphology and functions similar to DCs. We further investigated the E. coli BGs to induce maturation of bovine MoDCs in comparison to E. coli lipopolysaccharide (LPS). We observed the maturation marker molecules such as MHC-II, CD80 and CD86 were induced early and at higher levels in BG stimulated MoDCs as compared to the LPS stimulated MoDCs. BG mediated stimulation induced significantly higher levels of cytokine expression in bovine MoDCs than LPS. Both pro-inflammatory (IL-12 and TNF-α) and anti-inflammatory (IL-10) cytokines were induced in MoDCs after BGs stimulation. We further analysed the effects of BGs on the bovine MoDCs in an allogenic mixed lymphocyte reaction (MLR). We found the BG-treated bovine MoDCs had significantly (p<0.05) higher capacity to stimulate allogenic T cell proliferation in MLR as compared to the LPS. Taken together, these findings demonstrate the E. coli BGs induce a strong activation and maturation of bovine MoDCs.

Gamma-Irradiated Influenza A Virus Provides Adjuvant Activity to a Co-Administered Poorly Immunogenic SFV Vaccine in Mice

Many currently available inactivated vaccines require “adjuvants” to maximize the protective immune responses generated against the antigens of interest. Recent studies in mice with gamma-irradiated influenza A virus (γ-FLU) have shown its superior efficacy compared to other forms of inactivated FLU vaccines and its ability to induce both potent interferon type-I (IFN-I) responses and the IFN-I-associated partial lymphocyte activation. Commonly, IFN-I responses induced by adjuvants, combined in vaccine preparations, have been shown to effectively enhance the immunogenicity of the antigens of interest. Therefore, we investigated the potential adjuvant activity of γ-FLU and the possible effect on antibody responses against co-administrated antigens, using gamma-irradiated Semliki Forest virus (γ-SFV) as the experimental vaccine in mice. Our data show that co-vaccination with γ-FLU and γ-SFV resulted in enhanced SFV-specific antibody responses in terms of increased titers by sixfold and greater neutralization efficacy, when compared to vaccination with γ-SFV alone. This study provides promising evidence related to the possible use of γ-FLU as an adjuvant to poorly immunogenic vaccines without compromising the vaccine efficacy of γ-FLU.

PPARγ Agonists in Adaptive Immunity: What Do Immune Disorders and Their Models Have to Tell Us?

Adaptive immunity has evolved as a very powerful and highly specialized tool of host defense. Its classical protagonists are lymphocytes of the T- and B-cell lineage. Cytokines and chemokines play a key role as effector mechanisms of the adaptive immunity. Some autoimmune and inflammatory diseases are caused by disturbance of the adaptive immune system. Recent advances in understanding the pathogenesis of autoimmune diseases have led to research on new molecular and therapeutic targets. PPARγ are members of the nuclear receptor superfamily and are transcription factors involved in lipid metabolism as well as innate and adaptive immunity. PPARγ is activated by synthetic and endogenous ligands. Previous studies have shown that PPAR agonists regulate T-cell survival, activation and T helper cell differentiation into effector subsets: Th1, Th2, Th17, and Tregs. PPARγ has also been associated with B cells. The present review addresses these issues by placing PPARγ agonists in the context of adaptive immune responses and the relation of the activation of these receptors with the expression of cytokines involved in adaptive immunity.

The gp41 epitope, QARVLAVERY, is highly conserved and a potent inducer of IgA that neutralizes HIV-1 and inhibits viral transcytosis

Mucosal surfaces are the predominant site of human immunodeficiency virus (HIV)-1 transmission. For prophylactic approaches to effectively prevent HIV infection and subsequent dissemination, the induction of mucosally relevant protective immunity will be critical. Here, we have characterized the antibody (Ab) response generated by a highly conserved gp41epitope, QARVLAVERY, in an optimized immunization model that elicits potent epitope-specific Abs in the serum, vaginal washes, and fecal secretions of immunized mice. Our results show that QARVLAVERY is indeed a potent inducer of IgA and importantly, QARVLAVERY-specific IgA was effective in neutralizing HIV and inhibiting viral transcytosis. Intriguingly, QARVLAVERY also generated an approximate 1:1 ratio of IgG:IgA in the serum of immunized mice, independent of the delivery regimen and produced early systemic IgA, even before IgG. In light of the significantly high IgA induction by QARVLAVERY and the functionality of epitope-specific Abs in the inhibition of HIV infection and transcytosis, QARVLAVERY is an attractive epitope to be considered in mucosal vaccination strategies against HIV.

Regulation of IgA responses in cattle, humans and mice

Secretory IgA (SIgA) constitutes the largest component of the humoral immune system of the body with gram quantities of this isotype produced by mammals on a daily basis. Secretory IgA (SIgA) antibodies function by both blocking pathogen/commensal entry at mucosal surfaces and virus neutralization. Several pathways of induction of IgA responses have been described which depend on T cells (T cell dependent or TD) pathways or are independent of T cells (T-independent or TI) and are mediated by dendritic cells (DCs) and/or epithelial cells. Many elements of IgA regulation readily cross species barriers (adjuvants, soluble and cognate factors) and are highly conserved whereas other pathways may be more specific to any given species and must be evaluated. Regulation of IgA production in cattle is not completely understood and thus we have focused in part on highly conserved factors such as transforming growth factor beta, Type I and Type 2 interferons, neuropeptides which interdigitate mucosal tissues (vasoactive intestinal peptide or VIP), and a small peptide (IgA inducing peptide or IGIP) which can serve as targets for modulation and increasing SIgA virus-specific antibodies. We have evaluated the potential utility of modulating these factors in vitro in regulation of qualitative aspects of antibodies of the IgM, IgG and IgA isotypes at mucosal surfaces and in secretions of the upper and lower respiratory tract to a virus of economic and public health importance, foot and mouth disease virus (FMDV). IgA responses in cattle are essential for host defense in response to various infectious agents. In cattle, IgA is not released into the colostrum, as is the case for other mammals but only IgG1 is selectively transported. In previous studies in cattle, IgA has been shown to be regulated by several cytokines including IFN-gamma, Type I interferons such as IFN-alpha and IFN-tau, transforming growth factor beta, IgA inducing peptide and other potential factors such as APRIL and BlyS which have not yet been fully evaluated in cattle. Many of these factors, namely TGF-beta and Type I interferons block cell cycle progression which is an essential component of Ig class switching and thus these factors require additional regulatory factors such as IL-2 to drive cells through cell cycle resulting in class switch recombination. Among these factors, IgA inducing peptide was originally identified from a bovine gut associated lymphoid tissue expression library and is highly conserved in pigs and humans at >90% at the amino acid level. The factor is regulated differently in various species but is consistently produced by dendritic cells.

Peroxisome proliferator-activated receptor gamma ligands enhance human B cell antibody production and differentiation

Protective humoral immune responses critically depend on the optimal differentiation of B cells into Ab-secreting cells. Because of the important role of Abs in fighting infections and in successful vaccination, it is imperative to identify mediators that control B cell differentiation. Activation of B cells through TLR9 by CpG-DNA induces plasma cell differentiation and Ab production. Herein, we examined the role of the peroxisome proliferator-activated receptor (PPAR)gamma/RXRalpha pathway on human B cell differentiation. We demonstrated that activated B cells up-regulate their expression of PPARgamma. We also show that nanomolar levels of natural (15-deoxy-Delta(12,14)-prostaglandin J(2)) or synthetic (rosiglitazone) PPARgamma ligands enhanced B cell proliferation and significantly stimulated plasma cell differentiation and Ab production. Moreover, the addition of GW9662, a specific PPARgamma antagonist, abolished these effects. Retinoid X receptor (RXR) is the binding partner for PPARgamma and is required to produce an active transcriptional complex. The simultaneous addition of nanomolar concentrations of the RXRalpha ligand (9-cis-retinoic acid) and PPARgamma ligands to CpG-activated B cells resulted in additive effects on B cell proliferation, plasma cell differentiation, and Ab production. Furthermore, PPARgamma ligands alone or combined with 9-cis-retinoic acid enhanced CpG-induced expression of Cox-2 and the plasma cell transcription factor BLIMP-1. Induction of these important regulators of B cell differentiation provides a possible mechanism for the B cell-enhancing effects of PPARgamma ligands. These new findings indicate that low doses of PPARgamma/RXRalpha ligands could be used as a new type of adjuvant to stimulate Ab production.

Interferon type I responses in primary and secondary infections

The mammalian host responds to a microbial infection with a rapid innate immune reaction that is dominated by type I interferon (IFN-I) release. Most cells of vertebrates can respond to microbial attack with IFN-I production, but the cell type responsible for most of the systemic IFN-I release is thought to be plasmacytoid dendritic cells (pDCs). Besides its anti-microbial and especially anti-viral properties IFN-I also exerts a regulatory role on many facets of the sequential adaptive immune response. One of these is being the recently described partial, systemic activation of the vast majority of B and T lymphocytes in mice, irrespective of antigen reactivity. The biological significance of this partial activation of lymphocytes is at present speculative. Secondary infections occurring within a short time span of a primary infection fail to elicit a similar lymphocyte activation response due to a refractory period in systemic IFN-I production. This period of exhaustion in IFN-I responses is associated with an increased susceptibility of the host to secondary infections. The latter correlates with well-established clinical observations of heightened susceptibility of patients to secondary microbial infections after viral episodes.

The bovine antibody repertoire

Cattle are able to produce a full range of Ig classes including the long-elusive IgD through rearrangement of their germline genes. Several IgL groupings have been reported but as in several other livestock species (e.g. sheep, rabbits, chickens), rearrangement per se fails to generate significant IgH diversity. This is largely because of the modest number of bovine VH segments that participate in rearrangement and their conserved sequences. Perhaps in compensation, bovine Ig heavy chains carry CDR3 sequences of exceptional length. Processes that operate post-rearrangement to generate diversity remain ill defined as are the location, timing and triggers to these events. Reagents are needed to understand better the maturation of B lymphocytes, their responses to antigens and cytokines, and to provide standards for the quantitation of Ig responses in cattle; recombinant methods may help meet this need as Ab engineering technologies become more widely used.

Prime-boost strategies combining DNA and inactivated vaccines confer high immunity and protection in cattle against bovine herpesvirus-1

DNA vaccines have frequently been associated with poor efficacy in large animals. In the present study, one administration of an inactivated marker vaccine to cattle considerably boosted both humoral and cellular arms of the immune response primed with Bovine herpesvirus-1 (BoHV-1) DNA vaccines encoding glycoprotein D (gD) or gC+gD. Calves vaccinated according to the DNA prime-inactivated boost also showed significantly enhanced virological protection as compared to controls. The 4-logarithms reduction of virus shedding observed in primed-boosted animals was comparable to the one previously reported in calves immunized twice with marker vaccines. Intradermal immunization of cattle with DNA vaccines promoted a Th2-biased immune response but also primed a cellular component that was further boosted by the inactivated vaccine. Individual IgG2 titers of vaccinated calves were significantly correlated to IFN-gamma production. The immunization protocol described in the present study demonstrates the complementarity between DNA and conventional marker vaccines.

Cytokine mRNA expression in B cells from bovine leukemia virus-infected cattle with persistent lymphocytosis

We have characterized the expression of six cytokine mRNAs in highly purified B cells from bovine leukemia virus (BLV)-infected cows with persistent lymphocytosis. Selected cytokine mRNAs included those encoding tumor necrosis factor (TNF), lymphotoxin-alpha (LT-alpha), transforming growth factor-beta1 (TGF-beta1), interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and interleukin-10 (IL-10). Fresh B cells from cows with persistent lymphocytosis constitutively transcribed TNF, LT-alpha and TGF-beta1 mRNAs. Although IL-1beta, IL-6 and IL-10 mRNAs were barely detectable in fresh B cells from cows with persistent lymphocytosis, transcripts encoding these cytokines were strongly and rapidly upregulated in B cells after cell culture. Results from this study provide the first evidence that B cells infected with BLV express specific cytokine mRNAs in vivo.

Modulation of immune responses to bovine herpesvirus-1 in cattle by immunization with a DNA vaccine encoding glycoprotein D as a fusion protein with bovine CD154

The objective of this study was to determine whether a DNA vaccine encoding bovine CD154 linked to a truncated version of bovine herpesvirus-1 (BHV-1) glycoprotein D (tgD-CD154) induces enhanced tgD-specific immune responses in cattle. In vitro characterization demonstrated that tgD and tgD-CD154 both bind to cultured bovine B cells, whereas only tgD-CD154 induces interleukin-4-dependent proliferation, suggesting that tgD-CD154 specifically binds the CD40 receptor and induces receptor signalling. Calves were immunized with plasmid encoding either tgD or tgD-CD154 by intradermal injection with a needle-free device. After two immunizations, tgD-specific immune responses were observed in both vaccinated groups and after challenge with BHV-1 these responses further increased. Animals immunized with plasmid encoding tgD-CD154 had significantly higher tgD-specific serum titres of immunoglobulins G and A but significantly lower numbers of tgD-specific interferon-gamma-secreting cells than animals immunized with plasmid encoding tgD after BHV-1 challenge. This suggests that the expression of an antigen as a chimeric protein with CD154 can qualitatively alter immune responses in cattle. Since we previously showed that plasmid encoding tgD-CD154 induces significantly enhanced secondary tgD-specific antibody responses in sheep, there appear to be interspecies differences in the immune responses induced by tgD-CD154, which suggests that both proteins in the chimeric molecule may influence protein targeting and the induction of an immune response.

Chromium Supplementation Enhances Antibody Response to Vaccination with Tetanus Toxoid in Cattle

Nineteen multiparous late-pregnant dairy cows were divided into an experimental group (n = 10) and a control group (n = 9). Animals in the experimental group were fed a diet supplemented with chromium chelate admixed into wheat meal at 5 mg per animal per day. The supplementation was started 4 weeks before calving and stopped by the end of week 3 after calving. All the cows were vaccinated with tetanus toxoid in the fifth and sixth week of lactation. Monitoring of the characteristics of non-specific immunity did not show any significant between-group differences in total and differential leucocyte counts, percentages of lymphocyte subpopulations, activities of lectin-stimulated lymphocytes, phagocytic activities, and the contents of total immunoglobulins and lysozyme in blood sera. Tetanus toxoid-specific antibody titres, those of the IgG2 isotype in particular, were higher in the experimental group than in the control animals. These results indicate that chromium supplementation at the level used in this experiment modulated the regulation of functions of the immune system.

Role of alpha/beta interferons in the attenuation and immunogenicity of recombinant bovine respiratory syncytial viruses lacking NS proteins

Alpha/beta interferons (IFN-alpha/beta) are not only a powerful first line of defense against pathogens but also have potent immunomodulatory activities. Many viruses have developed mechanisms of subverting the IFN system to enhance their virulence. Previous studies have demonstrated that the nonstructural (NS) genes of bovine respiratory syncytial virus (BRSV) counteract the antiviral effects of IFN-alpha/beta. Here we demonstrate that, in contrast to wild-type BRSVs, recombinant BRSVs (rBRSVs) lacking the NS proteins, and those lacking NS2 in particular, are strong inducers of IFN-alpha/beta in bovine nasal fibroblasts and bronchoalveolar macrophages. Furthermore, whereas the NS deletion mutants replicated to wild-type rBRSV levels in cells lacking a functional IFN-alpha/beta system, their replication was severely attenuated in IFN-competent cells and in young calves. These results suggest that the NS proteins block the induction of IFN-alpha/beta gene expression and thereby increase the virulence of BRSV. Despite their poor replication in the respiratory tract of young calves, prior infection with virus lacking either the NS1 or the NS2 protein induced serum antibodies and protection against challenge with virulent BRSV. The greater level of protection induced by the NS2, than by the NS1, deletion mutant, was associated with higher BRSV-specific antibody titers and greater priming of BRSV-specific, IFN-gamma-producing CD4(+) T cells. Since there were no detectable differences in the ability of these mutants to replicate in the bovine respiratory tract, the greater immunogenicity of the NS2 deletion mutant may be associated with the greater ability of this virus to induce IFN-alpha/beta.

Identification and characterization of a novel regulatory factor: IgA-inducing protein

IgA is the predominant Ig isotype in mucosal secretions and thus plays a pivotal role in host defense. The mechanisms by which IgA expression is regulated may differ among species and involve multiple pathways. Various cytokines and costimulators have been identified which regulate expression of this isotype, including IL-10, IL-2, vasoactive intestinal peptide, and TGF-beta. We have tested a wide array of known factors, but only under very limited conditions do these factors mediate substantial IgA production in vitro from bovine B cells. In response to these findings, we generated a cDNA library in a mammalian expression vector from activated cells derived from bovine gut-associated lymphoid tissues (Peyer's patch and mesenteric lymph node cells) as a source of soluble factor(s) that may regulate IgA production. We have identified a novel factor, IgA-inducing protein, which stimulates relatively high levels of IgA production in vitro following CD40 stimulation in coculture with IL-2. Our data suggest that IgA-inducing protein regulates IgA by acting as a switch or differentiation factor and is expressed in a variety of lymphoid and nonlymphoid tissues.

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

Immunostimulatory oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG ODN) stimulate IL-12-dependent Th1 dominated cytokine and enhanced IgG responses when co-delivered with antigen to mice. However, the CpG ODN sequences that are optimal for each mammalian species may differ. Previously, we demonstrated that a CpG ODN containing the GTCGTT motif was optimal for stimulating bovine B cell proliferation, and induced IL-6, IL-12 and IFN-gamma production by peripheral blood mononuclear cells (PBMC). The current study was designed to test the hypothesis that the nuclease resistant phosphorothioate modified ODN 2006 (TCGTCGTTTTGTCGTTTTGTCGTT) would induce antigen-specific type 1 cytokine and enhanced IgG responses similar to those induced by IL-12. To test this adjuvant effect, calves were immunized with Anaplasma marginale major surface protein 2 (MSP2) with alum alone or combined with CpG ODN 2006, non-CpG ODN R2006 or IL-12. MSP2-specific IgG1 and IgG2 responses developed more rapidly in calves given IL-12, ODN 2006 or ODN R2006, but the highest IgG1 titers were obtained in CpG ODN-immunized calves. Antigen-specific lymphocyte proliferation and frequency of IFN-gamma-secreting cells were significantly increased in CpG ODN 2006- or IL-12-treated calves, and antigen-stimulated PBMC from these calves also expressed higher levels of IFN-gamma transcripts and lower levels of IL-4 transcripts. No differences in IL-10 mRNA expression were detected among the groups. These results indicate that CpG ODN 2006 is an effective vaccine adjuvant for stimulating both antibody and IFN-gamma mediated cellular immune responses in cattle.

Bovine dendritic cells generated from monocytes and bone marrow progenitors regulate immunoglobulin production in peripheral blood B cells

We examined whether bovine monocyte-derived and bone marrow (BM) dendritic cells (DCs) regulate antibody production in activated peripheral blood B cells. DCs were generated from monocytes and BM progenitors in the presence of bovine recombinant granulocyte/macrophage colony-stimulating factor (GM-CSF) and interleukin 4 (IL-4). Monocyte-derived DCs promoted B cells activated by the anti-CD3 triggered CD4(+) T cells or through immunoglobulin M (IgM) receptor to increase the level of IgG secretion. Furthermore, the addition of DCs triggered B cells activated through IgM receptors to produce IgG2 and IgA, thus inducing an isotype switch. BM-derived DCs increased the production of IgG in B cells activated by the anti-CD3 triggered CD4(+) T cells, but unlike monocyte-derived DCs did not have any effect on B cells activated through surface IgM. These data suggest that the regulation of humoral immune responses in cattle depends on the origin of DCs and the mode of B cell activation.

Type I interferon differential therapy for erythroleukemia: specificity of STAT activation

Type I interferons (IFNs), pleiotropic cytokines with antiviral, antiproliferative, apoptotic, and immunoregulatory functions, are efficacious in the treatment of malignancies, viral infections, and autoimmune diseases. Binding of these cytokines to their cognate receptor leads to activation of the Jak-signal transducers and activators of transcription (STAT) signaling pathway and altered gene expression. This signal pathway has been intensely studied using human IFN-alpha 2 and IFN-beta. However, there are over 14 human IFN-alpha subtypes and over 10 murine IFN-alpha subtypes, with a single IFN-beta subtype in both species. J2E cells are immortalized at the proerythroblast stage of development and produce a rapid and fatal erythroleukemia in vivo. These cells retain the ability to respond to erythropoietin in vitro by proliferating, differentiating, and remaining viable in the absence of serum. Here, we show that J2E cells are also functionally regulated differentially by IFN subtype treatment in vitro. A novel finding was the selective activation of STAT and mitogen-activated protein kinase (MAPK) molecules by different subtypes binding the IFN receptor. These findings indicate distinct effects for individual type I IFN subtypes, which are able to differentially activate members of the STAT and MAPK family. Finally, we investigated the efficacy of IFN naked DNA therapy in treating J2E-induced erythroleukemia in athymic nude mice. IFN subtypes differentially regulated the onset of erythroleukemia with delayed onset and increased survival, possibly via a reduction in cell viability, and enhanced antiproliferative and apoptotic effects observed for IFNA6 and IFNA9 treatment, respectively. Moreover, these data highlight the necessity to choose the best IFN subtype in disease treatment.

Anti-tumour activity of interferon-alpha in multiple myeloma: role of interleukin 6 and tumor cell differentiation

Interferon-alpha (IFN-alpha) is a pleotropic cytokine that has clinical activity against a wide variety of malignancies, including multiple myeloma (MM). In vitro, IFN-alpha has diverse effects on both normal and malignant cells, however, the exact mechanisms responsible for its clinical anti-tumour activity remain unclear. We found that IFN-alpha inhibited MM cell proliferation in association with cell cycle arrest at G1 and limited the clonogenic growth of both MM cell lines and primary patient specimens. At the doses tested, IFN-alpha was not cytotoxic, but induced terminal plasma cell differentiation resulting in the loss of clonogenicity. These activities were markedly enhanced by the major MM growth factor interleukin 6 (IL-6). Moreover, IL-6 was required for this process, as neutralizing antibodies against IL-6 inhibited the effects of IFN-alpha. IL-6 also induced MM cell terminal differentiation when combined with a second, unrelated, antiproliferative agent bryostatin-1, suggesting that its differentiating activities are preferentially enhanced in the presence of agents that inhibit cell cycling. These results suggest that the differentiating activities of IFN-alpha may play a role in its clinical antimyeloma activity and provide the rationale for clinical differentiation therapy in MM.

Phenotyping of transgenic cloned piglets

Numerous reports list the abnormalities obtained from cloning sheep and cattle. To date, few reports provide detailed information regarding the overall health status and performance data of cloned animals. This report follows three litters totaling 10 transgenic cloned piglets from birth through puberty. Significant findings from physical examinations and response to treatments are included, as well as necropsy data from five of the piglets that died during the study. The birth weights, placental weights, and growth rates for this group of piglets were not different from that of control animals raised in the same environment. Hematology and serum chemistry data were collected at 2 days of age, and at 2, 4, 8, 12, 16, 20, and 24 weeks of age. Results indicated a mild anemia and hypoproteinemia in the cloned piglets from birth through 4 weeks of age, but both conditions were corrected by 8 weeks of age. Echocardiography was performed on seven of the piglets. No anatomical defects were detected, but three of the piglets had decreased cardiac output values. However, both animals are growing and show no evidence of clinical disease. The immune system was evaluated by quantification of serum IgM and IgG levels and by determining the population of B-cells, macrophages, helper T-cells (CD4), cytotoxic T-cell (CD8), and double positive T-cells (CD4/CD8). With the exception of one animal, no abnormalities were detected with the immune system of the examined piglets. During the course of this study, five of the 10 piglets were euthanized or died, indicating there is a high mortality rate among cloned piglets, but the remaining five cloned piglets are free from detectable defects.

Peripheral blood-derived bovine dendritic cells promote IgG1-restricted B cell responses in vitro

Regulation of humoral responses involves multiple cell types including the requirements for cognate interactions between T and B cells to drive CD40-dependent responses to T-dependent antigens. A third cell type has also been shown to play an essential role, the dendritic cell (DC). We demonstrate that bovine peripheral blood-derived (PB)-DC are similar in function to features described for human interstitial DC including the production of signature type 2 cytokines [interleukin (IL)-13, IL-10]. PB-DC express moderate-to-high costimulatory molecule expression, and major histocompatibility complex class II is negative for CD14 expression and has low or no expression of CD11c. Consistent with the interstitial phenotype is the ability of PB-DC to influence B cell activation and differentiation via direct expression of CD40L and type 2 cytokines. Collectively, these results suggest that direct B cell-DC interactions may promote an immunoglobulin-isotype expression pattern consistent with type 2 responses, independent of direct T cell involvement.

Type 1 and type 2 responses in regulation of Ig isotype expression in cattle

Regulation of humoral immune responses is multifactorial involving appropriate activation, costimulation and the presence of specific soluble factors. Polarized type 1 or type 2 humoral responses in the laboratory mouse have been linked to expression of specific cytokines and thus can be used to provide insight into the type of response generated by infection. For example, IFN-gamma has been linked to IgG2a and IgG3 production, IL-4 to IgG1 and IgE production and TGF-beta to IgA production. Unlike the laboratory mouse, generally housed under defined conditions, highly skewed isotype expression patterns generally occur in cattle in chronic infections. A few examples of polarized responses have been noted in chronic experimental or naturally occurring infections including F. hepatica, M. paratuberculosis, C. parvum and B. abortus. In vitro studies using purified bovine B cells and various forms of costimulation and cytokines have demonstrated that isotype responses can be polarized under certain experimental conditions in vitro. That is, IgG1 expression is positively regulated by IL-4 and IgG2 expression is positively regulated by IFN-gamma. Other as yet unidentified factors may play pivotal roles in regulating humoral immune responses in large ruminant species in vivo. This possibility is best exemplified by recent studies using DNA vaccines in cattle that have been demonstrated in the mouse to be generally polarizing to a type 1 response. Surprisingly, studies in cattle using plasmid DNA as vaccination material show an almost exclusive IgG1 response. Based on a number of studies using T cell clones and various biological assays, it is clear that the classical roles of many cytokines in the laboratory mouse do not extrapolate entirely or at all to cattle. Thus, the design of adjuvants and immune modulators should be based on studies done in cattle or using bovine cells. Based on studies to date, several "holes" in the cytokine repertoire exist and these roles may be assumed by unique factors or activities of other known cytokines.

Coimmunisation with type I IFN genes enhances protective immunity against cytomegalovirus and myocarditis in gB DNA-vaccinated mice

Viral DNA vaccines encoding the glycoprotein B (gB) of cytomegalovirus provide partial protective immunity upon challenge with infectious virus. Although it is known that type I IFN can stimulate the adaptive immune response, their direct use in vaccines has been limited. Here we show that coimmunisation of type I IFN and gB CMV DNA constructs enhances protective immunity in mice. In vivo expression of IFN transgenes ranged from 1.2 to 2.0 x 10(4) IU/g tibialis anterior muscle. Viral titre in major target organs and the severity of acute CMV-induced myocarditis was reduced preferentially with either IFN-alpha 9 or IFN-beta, but not with IFN-alpha 6, coimmunisation. However, all IFN subtypes investigated markedly reduced chronic myocarditis in gB-vaccinated mice. The early antiviral IgG1 and IgG2a titres were enhanced with IFN-beta coimmunisation. TNF and IL-10 was increased in response to MCMV infection in mice coimmunised with IFN subtypes and viral gB DNA. Indeed T cells from IFN-inoculated mice reduced myocarditis upon in vivo transfer. These results suggest that select type I IFNs may act as a natural adjuvant for the immune response against CMV infection. Type I IFN DNA coimmunisation may provide increased efficacy for viral vaccines and subsequently modulate post-viral chronic inflammatory disorders.

Synergy of type I interferon-A6 and interferon-B naked DNA immunotherapy for cytomegalovirus infection

Delivery of type I IFN transgenes by naked DNA immunization can protect against cytomegalovirus infection and myocarditis. Here, we investigate IFN transgene expression, antiviral efficacy, and immunomodulation of myocarditis using various treatment regimes in a mouse CMV model. In vivo expression of the IFN transgene was observed in the sera for 35 days post-DNA inoculation. Prophylactic IFN-A6 and IFN-B DNA treatment for 14 days prior to murine cytomegalovirus (MCMV) infection was more efficacious in significantly reducing viral titres, than 2 days prior to or 2 days post-virus infection. Similarly, IFN-A6 DNA treatment commencing 14 days prior to virus infection was superior in suppressing both acute and chronic myocarditis. Furthermore, reduction of autoantibody titres was more pronounced when IFN was administered 14 days prior to viral infection. Combinational IFN gene therapy was assessed for synergy between IFN subtypes. Combination treatment with either IFN-A6/A9 or IFN-A6/B greatly reduced spleen viral titres while IFN-A6/B and IFN-A9/B reduced virus replication in the liver. Only IFN-A6/A9 and IFN-A9/B reduced acute viral myocarditis, whereas IFNA6/B treatment was most efficacious for autoimmune chronic myocarditis. Finally, treatment with IFN-A6 DNA 2 weeks post-MCMV infection proved effective at inhibiting the development of chronic autoimmune myocarditis. These findings suggest that immunomodulation of both antiviral and autoimmune responses by IFN DNA immunization may be an avenue for improved viral immunotherapy.

Type-1 transforming growth factor-beta differentially modulates tumoricidal activity of murine peritoneal macrophages against metastatic variants of the B16 murine melanoma

Transforming growth factor-beta 1 (TGF-beta 1) renders mouse peritoneal macrophages tumoricidal against metastatic variants of the B16 mouse melanoma in vitro. Both direct cytotoxicity and indirect cytotoxicity were observed. A subthreshold concentration (10 U/ml) of recombinant murine interferon-gamma (rMuIFN-gamma) enhanced the direct tumoricidal activity of TGF-beta 1-activated macrophages from 29% to 88% but did not change their indirect tumoricidal profile. Data obtained from macrophages preincubated with either TGF-beta 1 or rMuIFN-gamma showed that TGF-b1 can initiate tumoricidal activity better than rMuIFN-gamma. These effects were plasma-membrane mediated because targeting macrophages with liposomal TGF-beta 1 was ineffective. The order of tumoricidal susceptibility of the B16 melanoma lines to activated macrophages was B16F1 > B16F10 > B16BL6, in inverse order of metastatic potential.

Type I interferon gene therapy protects against cytomegalovirus-induced myocarditis

Type I interferons (IFNs) are produced early in response to viral infection and modulate adaptive immunity. Previously we demonstrated localized protection against murine cytomegalovirus (MCMV) infection in IFN DNA-inoculated mice. Here we examine the effect of seven IFN subtypes (IFNA1, A2, A4, A5, A6, A9 and B), administered by DNA inoculation, on systemic MCMV infection and myocarditis. IFN transgene expression altered the pathogenesis of MCMV infection with regard to virus titre and myocarditis. IFNA6 treatment reduced MCMV replication whilst IFNA5 and A2 enhanced virus replication. IFNA6, A9, and B treatment inhibited acute myocarditis. A T helper type 1-like, antibody and cytokine, response correlated with decreased virus titre and myocarditis. In addition, IFNA6 was able to reduce chronic cardiac inflammation. This research into the effectiveness of seven type I IFNs, using DNA gene therapy, highlights the need for correct subtype usage in the treatment of disease. We demonstrate effective subtypes for treatment in both the acute and chronic phases of MCMV infection and the resultant development of myocarditis.

Stimulation of B lymphocytes, macrophages, and dendritic cells by protozoan DNA

This review summarizes recent work from our laboratory demonstrating the activation of B lymphocytes, macrophages and dendritic cells by DNA from three different protozoan parasites of cattle and humans that is qualitatively similar to the now well-described effects of CpG-containing bacterial DNA. This novel mechanism of protozoan parasite recognition by the innate immune system could facilitate recovery from acute infection or contribute to infection-related pathology.

Modulation of immune responses to Mycobacterium bovis in cattle depleted of WC1(+) gamma delta T cells

It is accepted that cell-mediated immune responses predominate in mycobacterial infections. Many studies have shown that CD4(+) T cells produce Th1 cytokines, such as gamma interferon (IFN-gamma), in response to mycobacterial antigens and that the cytolytic activity of CD8(+) cells toward infected macrophages is important. However, the extent and manner in which gamma delta T cells participate in this response remain unclear. In ruminants, gamma delta T cells comprise a major proportion of the peripheral blood mononuclear cell population. We have previously shown that WC1(+) gamma delta T cells are involved early in Mycobacterium bovis infection of cattle, but their specific functions are not well understood. Here we describe an in vivo model of bovine tuberculosis in which the WC1(+) gamma delta T cells were depleted from the peripheral circulation and respiratory tract, by infusion of WC1(+)-specific monoclonal antibody, prior to infection. While no effects on disease pathology were observed in this experiment, results indicate that WC1(+) gamma delta T cells, which become significantly activated (CD25(+)) in the circulation of control calves from 21 days postinfection, may play a role in modulating the developing immune response to M. bovis. WC1(+)-depleted animals exhibited decreased antigen-specific lymphocyte proliferative response, an increased antigen-specific production of interleukin-4, and a lack of specific immunoglobulin G2 antibody. This suggests that WC1(+) gamma delta TCR(+) cells contribute, either directly or indirectly, toward the Th1 bias of the immune response in bovine tuberculosis--a hypothesis supported by the decreased innate production of IFN-gamma, which was observed in WC1(+)-depleted calves.

Mechanisms of graft acceptance: evidence that plasminogen activator controls donor-reactive delayed-type hypersensitivity responses in cardiac allograft acceptor mice

We have used delayed-type hypersensitivity (DTH) responses to probe the mechanisms of drug-induced cardiac allograft acceptance in mice. DBA/2-->C57BL/6 cardiac allograft recipients treated transiently with gallium nitrate accept their grafts for >90 days and fail to display DBA/2-reactive DTH responses. These DTH responses are restored when anti-TGF-beta Abs are included at the challenge site, and cell depletion studies showed that this DTH inhibition is mediated by CD4+ cells. Real-time PCR analysis revealed that allograft acceptor mice produce no more than background levels of TGF-beta mRNA at DTH challenge sites. This suggests that DTH regulation in allograft acceptor mice may involve TGF-beta activation, rather than TGF-beta production. The protease, plasmin, can activate TGF-beta, and activated T cells can express a receptor for the plasmin-producing enzyme urokinase-type plasminogen activator (uPA), and can also produce both uPA and tissue-type plasminogen activator (tPA). We observed that Abs to tPA or uPA can replace anti-TGF-beta mAb for the restoration of donor-reactive DTH responses in allograft acceptor mice. Histologic analysis revealed that accepted cardiac allografts express uPA, tPA, and active TGF-beta, whereas accepted cardiac isografts express only tPA, but not uPA or activated TGF-beta. These data demonstrate that local tPA and uPA contribute to DTH regulation in allograft acceptor mice and suggest that these elements of the fibrinolytic pathway are used to control donor-reactive cell-mediated immunity in allograft acceptor mice.

Activation of bovine B cells via surface immunoglobulin M cross-linking or CD40 ligation results in different B-cell phenotypes

Experiments reported herein demonstrate that activation of bovine B cells via surface immunoglobulin M (sIgM) cross-linking, analogous to T-cell independent (TI-2) antigenic stimulation, results in the expression of CD5. Interestingly, in the presence of CD40 ligand, sIgM-mediated induction of CD5 on B cells was inhibited. These findings indicate that activation of bovine B cells via B-cell receptor (BCR) cross-linking results in a CD5+ B-cell phenotype and that CD40 signalling is inhibitory to this process. Analysis of cytokine mRNA indicates that bovine B cells constitutively express tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1beta transcripts in vitro, while IL-10 mRNA expression is induced following sIgM cross-linking. IL-12 p40 transcripts were produced by B cells activated by CD40, but not by BCR, ligation. Analysis of cytokine receptor mRNA indicates that activation through CD40, in the presence or absence of IgM cross-linking, results in increased IL-4 receptor-alpha (IL-4Ralpha), IL-13Ralpha1 and interferon-alpha receptor 1 (IFN-alphaR1) mRNA levels. Overall, these findings suggest that activation of bovine B cells through BCR cross-linking yields an activation phenotype that differs substantially from that of B cells activated through CD40.

Interleukin-12 as an adjuvant promotes immunoglobulin G and type 1 cytokine recall responses to major surface protein 2 of the ehrlichial pathogen Anaplasma marginale

Anaplasma marginale is a tick-transmitted pathogen of cattle closely related to the human ehrlichiae, Ehrlichia chaffeensis and the agent of human granulocytic ehrlichiosis (HGE). These pathogens have in common a structurally conserved outer membrane protein (OMP) designated the major surface protein 2 (MSP-2) in A. marginale and HGE and OMP-1 in E. chaffeensis. Protective immunity against ehrlichial pathogens is believed to require induction of gamma interferon (IFN-gamma) and opsonizing immunoglobulin (Ig) subclasses directed against OMP epitopes that, in concert, activate macrophages for phagocytosis and killing. Because interleukin-12 (IL-12) acts as an adjuvant for protein immunization to induce IFN-gamma and protective immunity against intracellular pathogens, we hypothesized that as an adjuvant with MSP-2, IL-12 would augment type 1 recall responses to A. marginale. IL-12 was coadsorbed with MSP-2 to alum and shown to significantly enhance IFN-gamma production by lymph node cells (LNC) and LNC-derived CD4(+) T-cell lines from immunized calves following recall stimulation with A. marginale. LNC proliferation and IL-2 production were also enhanced in IL-12-treated calves. Elevated recall proliferative responses by peripheral blood mononuclear cells were still evident 9 months after immunization. Serum IgG levels were consistently increased in IL-12 immunized calves, predominantly due to higher IgG1 responses. The results support the use of IL-12 coadsorbed with OMP of ehrlichial pathogens in alum to amplify both antibody and type-1 cytokine responses important for protective immunity.

Modulation of host immune responses by protozoal DNA

The pathology caused by acute Babesia bovis infection is similar to that seen in severe human malaria caused by Plasmodium falciparum infection, which is related to dysregulated production of inflammatory cytokines and nitric oxide (NO). We have observed induction of NO, inducible nitric oxide synthase (iNOS) and inflammatory cytokines in macrophages by B. bovis. Furthermore, proliferation of lymphocytes from individuals never exposed to certain protozoal pathogens can be induced by crude protozoal parasite extracts. We have repeatedly observed stimulation of naive PBMC from cattle to antigenic extracts of Babesia bovis. Based on recent studies demonstrating the mitogenicity of bacterial and other non-vertebrate DNAs for murine B cells and macrophages, the mitogenic properties of B. bovis DNA were examined. B. bovis and E. coli DNAs induced proliferation of PBMC and purified B cells from non-exposed cattle. Stimulatory activity was reduced by DNase treatment and methylation with CpG methylase, indicating the presence of stimulatory non-methylated CpG motifs in the B. bovis genome. B. bovis and E. coli DNAs enhanced IgG secretion by cultured B cells, stimulating IgG1 and more strongly, IgG2. Several hexameric CpG immunostimulatory sequences (ISS) active for murine B cells were identified in an 11 kb fragment of B. bovis DNA. An oligodeoxyribonucleotide containing one of these (AACGTT), located in the rhoptry associated protein-1 (rap-1) open reading frame, stimulated B cell proliferation. These studies identify a potential mechanism by which protozoal parasites may modulate host immune responses, leading to consequences such as hypergammaglobulinemia and splenomegaly. These results also support the use of ISS as vaccine adjuvants to enhance Type 1 immune responses in cattle.

Designing blood-stage vaccines against Babesia bovis and B. bigemina

The tick-transmitted apicomplexan parasites Babesia bovis and B. bigemina cause significant disease in cattle in many tropical and temperate areas of the world. These parasites present a challenge for vaccine development, and yet provide a system for studying the pathogenesis, mechanisms of protective immunity and regulation of host immune responses associated with intraerythrocytic protozoan parasites in a non-rodent species. In this article, Wendy Brown and Guy Palmer review strategies for identifying candidate vaccine antigens of B. bovis and B. bigemina and for priming immune responses to evoke strain crossprotective immunity.