Interleukin-10 downregulates proliferation and expression of interleukin-2 receptor p55 chain and interferon-gamma, but not interleukin-2 or interleukin-4, by parasite-specific helper T cell clones obtained from cattle chronically infected with Babesia bovis or Fasciola hepatica

Dual neutralization of TNFR-2 and MMP-2 regulates the severity of S. aureus induced septic arthritis correlating alteration in the level of interferon gamma and interleukin-10 in terms of TNFR2 blocking. Immunol Res. 2018;66:97-119. [PMID: 29218573 DOI: 10.1007/s12026-017-8979-y]

Severity of S. aureus septic arthritis is correlated to prolonged inflammation by inflammatory cytokines like TNF-α, IL-1β, and IL-6 even after successful elimination of bacteria. Role of TNF-α via TNFR2 is not well established in this aspect. IFN-γ induces TNF-α release from the macrophages augmenting the inflammatory arthritis. IL-10 modulates the levels of pro-inflammatory cytokines promoting resolution of inflammation. TNF-α-TNFR2 signaling upregulates both of these cytokines. Higher level of MMP-2 induction by inflammatory cytokines during arthritis promotes tissue destruction. Whether dual neutralization of TNFR-2 and MMP-2 regulates the severity of S. aureus arthritis by modulating local and systemic cytokine milieu mainly due to TNFR-2 blocking was an obvious question. Here, we attempted the effects of neutralization of MMP-2 and TNFR2 on S. aureus arthritis and its impact on pro-inflammatory cytokines and some other parameters related to tissue destruction. Reduction in arthritis index was noticed in infected mice treated with both MMP-2 inhibitor and TNFR2 antibody. Lowest levels of inflammatory cytokines, iNOS, RANKL, NF-κb, JNK kinase, ROS, and MPO, and lysozyme activity were observed in combined neutralization group at 9 and 15 dpi, but at 3 dpi, most of the above parameters remained elevated due to TNFR2 neutralization. Diminished IL-10 and IFN-γ levels as a result of TNFR2 neutralization at early and later phase of infection respectively might be responsible for these contrasting effects. Overall, it can be suggested that administration of MMP-2 inhibitor and TNFR2 antibody in combination is protective against the inflammation and tissue destruction associated with S. aureus infection during the arthritic episode.

Neutralization of TNFR-1 and TNFR-2 modulates S. aureus induced septic arthritis by regulating the levels of pro inflammatory and anti inflammatory cytokines during the progression of the disease

Staphylococcal septic arthritis remains a serious medical concern due to rapid and sustained production of inflammatory cytokines that leads to progressive and irreversible joint destruction with high mortality rate in patients despite adequate antibiotics treatment. TNF-α signalling via TNFR-1 contributes to arthritic destruction by aggravating inflammation. Impact of TNFR-2 signalling is not well established in this aspect. Hence the objective of our study was to evaluate the role of dual neutralization TNFR-1 and TNFR-2 in the pathogenesis of S. aureus infection induced septic arthritis. Mice were infected with live S. aureus (5 × 10⁶ cells/ml) followed by administration of TNFR-1and TNFR-2 neutralizing antibody. To measure arthritis index and osteoclastogenesis, histology result in joint tissue and TRAP staining images of arthritis joints have been performed respectively. Maximum reduction in the joint and paw swelling was observed in infected mice treated with both TNFR-1 and TNFR-2 antibody. NF-κB signalling was found to be mainly regulated by TNFR-1 whereas TNFR-2 significantly modulated JNK pathway. Lowest levels of inflammatory cytokines like TNF-α, IL-1β, IL-6, and IFN-γ were observed in both serum and synovial tissues signifying maximum protection in S. aureus arthritis during combination treatment. However IFN-γ and IL-10 levels were significantly altered by TNFR-2 neutralization that indicates both pro and anti inflammatory role of TNFR-2 respectively. Highest decrement in ROS concentration, iNOS expression with least MPO and lysozyme activity was detected in case of combined neutralization. During the early phase of infection all the aforesaid inflammatory parameters remained elevated due to lack of IL-10 as a result of TNFR-2 neutralization as IL-10 negatively modulates pro inflammatory cytokines. Increase in inflammatory cytokines during early phase might also be responsible for decreased bacterial count in TNFR-2 neutralized groups. Thus it can be suggested that combined administration of TNFR-1 and TNFR-2 antibody has a beneficial effect against the severity of S. aureus induced arthritis.

Free exopolysaccharide from Mycoplasma mycoides subsp. mycoides possesses anti-inflammatory properties

In this study we explored the immunomodulatory properties of highly purified free galactan, the soluble exopolysaccharide secreted by Mycoplasma mycoides subsp. mycoides (Mmm). Galactan was shown to bind to TLR2 but not TLR4 using HEK293 reporter cells and to induce the production of the anti-inflammatory cytokine IL-10 in bovine macrophages, whereas low IL-12p40 and no TNF-α, both pro-inflammatory cytokines, were induced in these cells. In addition, pre-treatment of macrophages with galactan substantially reduced lipopolysaccharide (LPS)-induced production of pro-inflammatory cytokines TNF- and IL-12p40 while increasing LPS-induced secretion of immunosuppressive IL-10. Also, galactan did not activate naïve lymphocytes and induced only low production of the Th1 cytokine IFN-γ in Mmm-experienced lymphocytes. Finally, galactan triggered weak recall proliferation of CD4+ T lymphocytes from contagious bovine pleuropneumonia-infected animals despite having a positive effect on the expression of co-stimulatory molecules on macrophages. All together, these results suggest that galactan possesses anti-inflammatory properties and potentially provides Mmm with a mechanism to evade host innate and adaptive cell-mediated immune responses.

Effect of blood transfusion during radiotherapy on the immune function of patients with cancer of the uterine cervix: role of interleukin-10

PURPOSE

To analyze prospectively the effects of blood transfusion administered during radiotherapy (RT) on the immune function of patients with locally advanced cervical cancer.

METHODS AND MATERIALS

In a total of 15 patients, 7 transfused and 8 untransfused, lymphocyte populations, including CD3+, CD4+, and CD8+ T-cell subsets, B cells (CD19+), and natural killer (NK) cells (CD56+, CD16+, CD3-) were studied before (i.e., time 0), during (i.e., times 1 and 2), and after (i.e., time 3) therapy. Expression of the early (CD25) and late (HLA-DR) activation markers on CD3+ T cells, the intracellular levels of perforin in CD8+ and CD56+ cells, and interferon (IFN)-gamma, interleukin (IL)-2, and IL-4 in CD4+ and CD8+ T cells were also measured. NK cell cytotoxicity against the NK-sensitive target K-562 cells and CD8+ T-cell-directed cytotoxicity against OKT3 hybridoma cells were also assessed. Finally, the plasma levels of the immunoregulatory cytokine IL-10 were analyzed by enzyme-linked immunosorbent assay.

RESULTS

The mean absolute number of all lymphocyte subsets compared with pretreatment levels decreased significantly during RT of both transfused and untransfused patients (p >0.001), with no detectable differences between the two groups in terms of total lymphocytes or relative numbers of CD3+ and CD4+ T cells, CD56+ NK cells, or CD19+ B cells. In contrast, concomitant with an inversion of the CD4/CD8 ratio, a significant increase in the number of CD8+ T cells at time 2 and CD3+ T cells, CD8+ T cells, and NK cells at time 3 was found in the transfused patients compared with the untransfused group. The percentages of CD25+/CD3+ T cells and HLA-DR+/CD3+ T cells increased during RT of the untransfused patients, but CD3+ T cells showed decreased CD25 expression and increased HLA-DR expression in the transfused group. An increase of CD8+ IFN-gamma+ T cells with a concomitant decrease in CD8+ IL-2+ T cells was found in the transfused vs. untransfused group, and no differences were noted in the percentage of CD4+ IFN-gamma+ T cells and CD4+ IL-2+ T cells. The proportion of perforin-positive CD8+ and CD56+ cells was higher in the transfused group than in the untransfused group. However, CD56+ cells and CD8+ T cells from the transfused patients showed markedly diminished cytotoxic function. Finally, IL-10 was detected only in the plasma of the transfused patients.

CONCLUSION

Blood transfusion during primary RT for cervical cancer profoundly alters the magnitude and characteristics of radiation-induced immunosuppression. Elevated serum IL-10 in transfused patients may play a role in the disregulation of lymphocyte function, in particular, the depression of NK- and T-cell cytotoxicity. Investigation of alternatives to blood transfusion during RT that do not diminish host immunity is warranted.

Platelet factor 4 inhibits proliferation and cytokine release of activated human T cells

Platelet factor 4 (PF-4), a platelet-derived CXC chemokine, has been shown to induce the differentiation of monocytes into a subset of macrophages that lack the expression of HLA-DR Ag. This suggests a potential role for PF-4 in the modulation of monocyte-dependent T cell activation. Using an Ag-specific stimulation model in which T cells were cocultured with monocytes in the presence of recall Ags, we could show that under these conditions PF-4-treatment caused a strong decrease of T cell proliferation as well as of IFN-gamma release. However, inhibition of T cell functions such as proliferation, IL-2 release, and IL-2 mRNA production did also occur when isolated T cells were activated in the absence of monocytes with immobilized Abs directed against CD3 in combination with cross-linked anti-CD28 Abs. The effect could be reversed when low concentrations of exogenous IL-2 instead of anti-CD28 were used as a costimulus in combination with anti-CD3 Abs. Further evidence for direct modulation of T cell function by PF-4 was obtained by the detection of specific binding sites for the chemokine on the surface of these cells. Taken together, our results show that specific binding of PF-4, resulting in the down-regulation of the IL-2-release correlates with the inhibition of functions in activated T cells.

Development of an ELISA for bovine IL-10

The objective of the study was to develop an assay for bovine IL-10 that could be applied to analyses of immune responses and advance understanding of a variety of diseases of cattle. Recombinant bovine IL-10 (rbo IL-10) was transiently expressed in Cos-7 cells and shown to inhibit the synthesis of IFN gamma by bovine cells stimulated with antigen in vitro. Mice were immunised with a plasmid containing a cDNA insert encoding rbo IL-10 and inoculated with rbo IL-10. A number of monoclonal antibodies (mAb) were generated that reacted with rbo IL-10 in an ELISA. Some of these mAb neutralised the ability of rbo IL-10 to inhibit IFN gamma synthesis by antigen-stimulated bovine cells. A pair of mAb was identified that together could be used to detect both recombinant and natural bovine IL-10 present in supernatant of PBMC stimulated with ConA. A luminescent detection method was applied to the ELISA making it more sensitive. Using this method native IL-10 was detected in supernatants of PBMC, diluted blood and undiluted blood from cattle immunised with Mycobacterium bovis BCG or ovalbumin and incubated in vitro with antigen indicating the applicability of the assay to a number of in vitro culture systems.

The age-related immunity in cattle to Babesia bovis infection involves the rapid induction of interleukin-12, interferon-gamma and inducible nitric oxide synthase mRNA expression in the spleen

Young calves possess a strong innate immunity against Babesia bovis infection that lasts for approximately 6 months after birth and is abrogated with the removal of the spleen. This immunity is characterized as cellular involving a soluble mediator. Nitric oxide has been implicated by virtue of its babesiacidal affects in vitro, but questioned to be as effective in vivo, due to its ability to downregulate type-1 immunity. Spleen cells were obtained from 4-month-old calves and adult steers and processed for monitoring cytokine and inducible nitric oxide synthase (iNOS) mRNA expression during the response to initial B. bovis infection. The data provided evidence of a transient role for nitric oxide in innate immunity, characterized by brief iNOS induction in the spleen of calves that was not detectable in the spleens of adults. The iNOS message followed the early induction of interleukin (IL)-12 and interferon (IFN)-gamma message in calves. The induction of IL-12 and IFN-gamma message in adults was delayed until IL-10 message was induced. Transformation growth factor-beta mRNA expression levels were greater in spleen cells from adults early in infection and then declined, whereas expression levels increased in spleen cells from calves later in the infection process. Together, the data support the concept of 'first come, first serve' cytokine influence over cellular activities, the importance of a type-1 response in the control of an initial infection and the need for tight regulation in order to prevent pathology associated with over production of nitric oxide and inflammatory cytokines.

Comparative effects of interleukin-12 and interleukin-4 on cytokine responses by antigen-stimulated memory CD4+ T cells of cattle: IL-12 enhances IFN-gamma production, whereas IL-4 has marginal effects on cytokine expression

Interleukin-12 (IL-12) and IL-4 are important immunoregulatory cytokines that determine the fate of naive T cells during antigen priming in mice and also influence cytokine synthesis by differentiated murine and human T cells. The roles of these cytokines in regulating the differentiation and effector function of bovine T cells are less well studied. We investigated the ability of human IL-12 and bovine IL-4 to modify cytokine expression by antigen-stimulated T cells from cattle immune to the protozoal parasites Babesia bovis and Babesia bigemina or reactive with Mycobacterium bovis purified protein derivative. Peripheral blood mononuclear cells (PBMC) were cultured with specific antigen and IL-4 or IL-12 for 1 week. Then viable lymphoblasts consisting of predominantly CD4+ T cells were restimulated with antigen and antigen-presenting cells (APC) with or without cytokine. Cell lines were cultured for several weeks, and following restimulation with antigen and APC in the absence of exogenous cytokine, the cell lines were analyzed for proliferation, interferon-gamma (IFN-gamma) production, and expression of IL-2, IL4-, IL-10, or IFN-gamma transcript levels using a quantitative competitive RT-PCR. IL-12 and IL-4 had no effect on the composition of CD4, CD8, or gammadelta T cells in the cell lines or on the level of antigen-induced proliferation. IL-12 stimulated enhanced levels of IFN-gamma protein and transcript expression in all cell lines, with no consistent effects on IL-2 or IL-4 expression. In two B. bovis-specific cell lines, IL-12 suppressed IL-10 expression. IL-4 had no consistent effect on expression of any cytokine. These results indicate the use of IL-12 as an adjuvant to enhance type 1 cytokine responses in cattle during antigen priming.

Innate resistance to experimental Trypanosoma congolense infection: differences in IL-10 synthesis by macrophage cell lines from resistant and susceptible inbred mice

BALB/c and C57Bl/6 mice differ in resistance to T. congolense infections. We investigated the production of various cytokines (IL-10, IL-6, TNF-alpha and TGF-beta) by macrophages from these mice. Macrophage cell lines (BALB.BM cells) of BALB/c mice but not (ANA-I cells)of C57BL/6 mice constitutively produced IL-10. Challenge of these cells with trypanosomes induced the production of 50-100 times more IL-10 in BALB.BM cells than in ANA-1 cells. Pre-incubation of the cell lines with IFN-gamma. prior to the trypanosome challenge, further upregulated this IL-10 production in BALB.BM but not in ANA-1 cells. Primary cultures of bone marrow-derived macrophages (BMDM) from BALB/c mice also produced more IL-10 following challenge with IFN-gamma and opsonized trypanosomes than did the C57Bl/6 BMDM. Similarly after challenge with trypanosomes, BALB.BM and BALB/c BMDM produced significantly more IL-6 than did the analogous cells from the C57Bl/6 mice following such challenges. Higher steady state levels of TNF-alpha mRNA accumulated in ANA-1 cells than in BALB.BM cells following challenge with IFN-gamma and opsonized trypanosomes. Findings of this study for the first time indicate a differential regulation of cytokines (IL-10, IL-6 and TNF-alpha) in macrophages of mice that significantly differ in their susceptibility to infections with T. congolense.

Immune response of cattle infected with African trypanosomes

Trypanosomosis is the most economically important disease constraint to livestock productivity in sub-Saharan Africa and has significant negative impact in other parts of the world. Livestock are an integral component of farming systems and thus contribute significantly to food and economic security in developing countries. Current methods of control for trypanosomosis are inadequate to prevent the enormous socioeconomic losses resulting from this disease. A vaccine has been viewed as the most desirable control option. However, the complexity of the parasite's antigenic repertoire made development of a vaccine based on the variable surface glycoprotein coat unlikely. As a result, research is now focused on identifying invariant trypanosome components as potential targets for interrupting infection or infection-mediated disease. Immunosuppression appears to be a nearly universal feature of infection with African trypanosomes and thus may represent an essential element of the host-parasite relationship, possibly by reducing the host's ability to mount a protective immune response. Antibody, T cell and macrophage/monocyte responses of infected cattle are depressed in both trypanosusceptible and trypanotolerant breeds of cattle. This review describes the specific T cell and monocyte/macrophage functions that are altered in trypanosome-infected cattle and compares these disorders with those that have been described in the murine model of trypanosomosis. The identification of parasite factors that induce immunosuppression and the mechanisms that mediate depressed immune responses might suggest novel disease intervention strategies.

Upregulation of interleukin-4 and IFN-gamma expression by IFN-tau, a member of the type I IFN family

Trophoblast interferon-tau (IFN-tau) is a new member of the type I IFN family that is produced in large quantities by the ruminant conceptus. Like other type I IFN, IFN-tau inhibits viral replication and activates natural killer (NK)-mediated cytotoxicity. In mice and humans, type I IFN enhances type 1 T helper (Th) cell responses, but the effects of type I IFN, including IFN-tau, on cytokine expression by bovine Th cells have not been described. The present study determined the effects of IFN-tau on interleukin-4 (IL-4), IFN-gamma, and IL-10 expression by antigen-specific, CD4+ T cell lines derived from cattle immune to either Babesia bovis, Babesia bigemina rhoptry-associated protein-1, or Anaplasma marginale. IFN-tau upregulated IFN-gamma secretion and steady-state levels of IFN-gamma and IL-4 mRNA by cell lines cultured for 3-6 weeks. In contrast, the steady-state levels of IL-10 mRNA were either not changed or inhibited at these times. Similar effects were obtained with human IFN-alpha. Comparison of the quantities of IFN-gamma, IL-4, and IL-10 transcripts in IFN-tau-treated or IFN-alpha-treated cultures revealed that even though IFN-gamma was the predominant cytokine expressed by all T cell lines, both IFN-gamma and IL-4 steady-state transcript levels were upregulated by a comparable degree. Thus, these studies demonstrate that IFN-tau is an immunomodulatory cytokine that promotes enhanced IL-4 and IFN-gamma responses by effector T cells but not, strictly speaking, Thl-biased responses in cattle. These results indicate the potential use of this cytokine as an adjuvant in ruminants to boost cell-mediated immune responses.

A Cryptosporidium parvum oocyst low molecular mass fraction evokes a CD4+ T-cell-dependent IFN-gamma response in bovine peripheral blood mononuclear cell cultures

T-Cell antigens that induce the in-vitro interferon-gamma response during Cryptosporidium parvum infection of neonatal calves were identified. A total oocyst extract was separated into a high and a low Mr fraction by a microfiltration technique. Both the high and low Mr fractions evoked an in-vitro interferon-gamma response in naturally infected animals, although strong individual differences between the hosts were observed. Using a complement-mediated technique CD4+ T-cells or WC1+gammadelta T-cells were depleted, whereupon the remaining lymphocyte cultures were stimulated with the different antigen preparations. It was shown that the in-vitro interferon-gamma response of Cryptosporidium-infected calves is CD4+ T-cell-dependent.

Trypanosoma congolense infection of trypanotolerant N'Dama (Bos taurus) cattle is associated with decreased secretion of nitric oxide by interferon-gamma-activated monocytes and increased transcription of interleukin-10

The mechanisms whereby trypanotolerant N'Dama cattle control infection with Trypanosoma congolense are unknown. Previous studies have suggested that the monocytes of N'Dama cattle are more highly activated during infection than those of trypanosusceptible Boran cattle. However, we have recently reported that the monocytes of Boran cattle have a reduced capacity to secrete nitric oxide during trypanosome infection. We therefore evaluated the production of nitric oxide by monocytes of trypanotolerant N'Dama cattle infected with T. congolense in response to interferon-gamma, bacterial lipopolysaccharide or trypanosome antigens. Interferon-gamma-induced nitric oxide production was decreased between days 25 and 76 of infection, while lipopolysaccharide-induced secretion of nitric oxide was increased at days 13 and again at day 76 post-infection. Trypanosome antigens did not elicit nitric oxide production. Analysis of interleukin-10 mRNA transcription in peripheral blood leucocytes revealed an increase at time points that coincided with decreased interferon-gamma-induced nitric oxide synthesis. In contrast, interferon-gamma mRNA expression was not changed during infection while tumour necrosis factor-alpha was slightly reduced at day 32 post-infection. Recombinant interleukin-10 suppressed interferon-gamma-induced nitric oxide and tumour necrosis factor-alpha secretion, but not lipopolysaccharide-induced nitric oxide secretion in cultures of peripheral blood mononuclear cells and monocytes of uninfected cattle. These results suggest that the nitric oxide response of monocytes to IFN-gamma but not lipopolysaccharide, is suppressed during infection. The kinetics of the upregulation of interleukin-10 and its biological activity indicate a possible association with the depression of nitric oxide production and control of tumour necrosis factor-alpha.

Babesia bovis immunity. In vitro and in vivo evidence for IL-10 regulation of IFN-gamma and iNOS

IL-10 has been shown to have profound immunoregulatory attributes and in the bovine appears to downregulate both Th1- and Th2-like responses. Using RT-PCR, we demonstrate IL-10 in vitro down-regulation of mRNA expression of iNOS, the cytokines involved in nitric oxide signal transduction initiation (IFN-gamma and TNF-alpha), and other mononuclear phagocyte associate cytokines. In addition, using RT-PCR with peripheral blood leukocytes and spleen leukocytes, the Griess reaction, and a killing assay, we provide evidence for the importance of iNOS in a successful immune response to B. bovis infection and for high and persistent IL-10 mRNA expression when the immune response is unsuccessful. We also provide evidence that antibody developed early after an initial infection appears to lack protective attributes (neutralizing and opsonic). Together, the data suggests that IL-10 and IFN-gamma are critical molecules involved in the response to this intraerythrocytic protozoan infection.

Bovine type 1 and type 2 responses

The Th1/Th2 paradigm has provided a useful framework for understanding the observed bias in immune responses that are often dominated by either cell-mediated or humoral responses, and for devising therapeutic strategies to stimulate T cell- or antibody-mediated immunity. However this paradigm is an oversimplification of a much more complex immunoregulatory network. Studies with bovine Th cell clones and immunoregulatory cytokines support this viewpoint. This paper highlights the progress that has been made in defining type 1 and type 2 responses in cattle. Evidence is presented for the presence of different subtypes of antigen-specific Th cell clones of cattle which constitute a spectrum of cell phenotypes, and for cytokine-mediated regulation of Th cell responses that differs from that observed in mice. The majority of over 60 parasite antigen-specific Th cell clones coexpress IL-4 and IFN-gamma, and polarized cytokine profiles were rarely observed. Furthermore, IL-2 and IL-10 expression was not restricted to IFN-gamma or IL-4-producing cells, respectively. This lack of coordinate regulation of "Th1" and "Th2" cytokines strengthens the emerging viewpoint that Th1 and Th2 responses, per se, do not typify the immune response to most pathogens. In addition, we provide evidence that major regulatory cytokines, IL-4, IL-10, and IL-12, do not selectively exert their negative (IL-4 and IL-10) or positive (IL-12) effects on Th1-like cells.

B-lymphocyte proliferation during bovine leukemia virus-induced persistent lymphocytosis is enhanced by T-lymphocyte-derived interleukin-2

Bovine leukemia virus (BLV)-induced persistent lymphocytosis is characterized by a polyclonal expansion of CD5+ B lymphocytes. To examine the role of the cytokine microenvironment in this virus-induced B-lymphocyte expansion, the expression of interleukin-2 (IL-2), IL-4, IL-10, and gamma interferon (IFN-gamma) mRNA, was measured in stimulated peripheral blood mononuclear cells from persistently lymphocytotic BLV-infected cows, nonlymphocytotic BLV-infected cows, and uninfected cows. IL-2 and IL-10 mRNA expression and IL-2 functional activity were significantly increased when peripheral blood mononuclear cells from persistently lymphocytotic cows were stimulated with concanavalin A (ConA). Additionally, during persistent lymphocytosis, peak IL-2 and IL-10 mRNA expression was delayed, and elevated expression was prolonged. To determine the potential biologic importance of increased IL-2 and IL-10 expression, the response of isolated B lymphocytes from persistently lymphocytotic cows to human recombinant cytokines and to cytokine-containing supernatants from isolated T lymphocytes was examined. While recombinant human IL-10 (rhIL-10) did not consistently induce detectable changes, rhIL-2 increased viral protein (p24) and IL-2 receptor expression in isolated B lymphocytes from persistently lymphocytotic cows. Additionally, rhIL-2 and supernatant from ConA-stimulated T lymphocytes enhanced B-lymphocyte proliferation. The stimulatory activity of the T-lymphocyte supernatant could be completely inhibited with a polyclonal anti-rhIL-2 antibody. Finally, polyclonal anti-rhIL-2 antibody, as well as anti-BLV antibody, inhibited spontaneous proliferation of peripheral blood mononuclear cells from persistently lymphocytotic cows, demonstrating that the spontaneous lymphoproliferation characteristic of BLV-induced persistent lymphocytosis is IL-2 dependent and antigen dependent. Collectively, these findings strongly suggest that increased T-lymphocyte expression of IL-2 in BLV-infected cows contributes to development and/or maintenance of persistent B lymphocytosis.

The role of IL-10 in iNOS and cytokine mRNA expression during in vitro differentiation of bovine mononuclear phagocytes

In the study reported here, we used RT-PCR with primers specific for interleukin-1 (IL-1), IL-6, IL-10, tumor necrosis factor-alpha (TNF-alpha), and nitric oxide synthase (iNOS) to assess the cytokine mRNA expression associated with bovine blood monocytes during their differentiation to macrophages cultured on plastic (1 week). In addition, we used RT-PCR to assess the contribution of gammadelta T cells as a source of interferon-gamma (IFN-gamma), the induction signal for iNOS. Further, we evaluated cytocentrifuge preparations from the cultures for the production of IL-10 using specific antibody. We previously demonstrated that iNOS can be induced in cultured bovine monocytes in response to IFN-gamma and TNF-alpha but lose this capability in a short period of time. However, we demonstrate here that iNOS induction from monocytes cultured with IFN-gamma secreting gammadelta T cells is prolonged, suggesting that this source of IFN-gamma primes the monocytes before exogenous stimulation. Based on mRNA expression, placement of monocytes in culture resulted in activation, followed by quiescence. By 6 days in culture, the iNOS message was reduced below the basal level. In addition, the TNF-alpha message was substantially reduced, and IL-1 and IL-6 messages were reduced below detectable levels. This correlated with an increase in IL-10 message. Downregulation of these same cytokine messages as well as IFN-gamma message occurred within a 20-h period when IL-10 was added exogenously to cultures of total leukocytes. At the same time, there was an increase in the number of IL-10-positive cells and an increase in the intensity of anti-IL-10 staining within adherent cells. These results provide evidence for IL-10 regulation of some bovine mononuclear phagocyte effector functions.

The immunomodulator AS101 restores T(H1) type of response suppressed by Babesia rodhaini in BALB/c mice

The immunomodulator AS101 has been previously shown to confer protection upon BALB/c mice infected with the intraerythrocytic parasite Babesia rodhaini (B. rodhaini). The present study focuses on the effect of AS101 administration on the acute phase of babesial infection where T helper cell subset patterns-TH1/TH2-were assessed in heavily infected mice. Secretion of cytokines of the TH1 subset (IL-2, IFN-gamma, IL-12) and of the TH2 subset (IL-10, IL-4) as well as TGF-beta was measured following the administration of AS101 2 weeks before parasite infection. Our results demonstrate that the parasites suppress IL-2 protein and IL-12 mRNA and that AS101 upregulates their secretion: IL-2, 8 u/ml vs 34 u/ml, respectively; IFN-gamma protein, 2370 pg/ml vs 4777 pg/ml, respectively. Conversely, babesial infection results in the upregulation of IL-10 and IL-4 proteins and TGF-beta transcripts, whereas AS101 downregulates their production: IL-10, 1800 pg/ml vs 360 pg/ml, respectively; IL-4, 58.3 pg/ml vs 24.5 pg/ml, respectively. A possible escape mechanism induced by B. rodhaini is suggested, starting with IL-10 inhibition of macrophage activities leading to a suppression of the TH1 response and of IL-2 in particular. It is therefore possible that AS101 may protect infected mice by activating cellular-mediated immunity and concurrently balancing the TH subset responses. It is suggested that AS101 may be effective as an antiparasitic drug.

Mechanisms of inflammation and leukocyte activation

This article reviews the current status of the knowledge of mechanisms of activating inflammatory responses. It also describes inflammatory mediators, adhesion proteins, the inflammatory process itself, and the molecular mechanisms controlling inflammatory cell activation and regulation.

Immunization with Babesia bigemina rhoptry-associated protein 1 induces a type 1 cytokine response

Rhoptry-associated protein-1 (RAP-1) homologues of Babesia bigemina and Babesia bovis are promising candidates for inclusion in subunit vaccines against these hemoprotozoan parasites. Partial protection against challenge infection has been achieved with native forms of these antigens, but the mechanism of immunity has not been thoroughly defined. We previously demonstrated that a panel of antigen-specific T helper cell clones derived from B. bigemina RAP-1-immunized cattle expressed relatively high levels of interferon-gamma (IFN-gamma) protein and transcript and low levels of interleukin-4 (IL-4), indicative of a type 1 immune response. In the current study we present evidence that subcutaneous immunization with native B. bigemina RAP-1 protein in RIBI adjuvant induces a predominant type 1 immune response in vivo, characterized by relatively high levels of IFN-gamma and IL-2 and low levels of IL-4 and IL-10 mRNA in the draining prescapular lymph node. Ex vivo restimulation of draining lymph node lymphocytes with specific antigen resulted in proliferation and enhanced expression of IL-2 and IFN-gamma, whereas IL-4 and IL-10 transcript levels remained relatively low. These findings show that our previously described cytokine profiles of antigen-specific cloned T cell lines are representative of autologous in vivo responses and confirm that type 1 recall responses to B. bigemina RAP-1 can be evoked in immunized animals by native parasite antigen.

Babesia bovis rhoptry-associated protein 1 is immunodominant for T helper cells of immune cattle and contains T-cell epitopes conserved among geographically distant B. bovis strains

The ability of rhoptry-associated protein 1 (RAP-1) of Babesia bovis and Babesia bigemina to confer partial protective immunity in cattle has stimulated interest in characterizing both B-cell and T-cell epitopes of these proteins. It was previously shown that B. bovis RAP-1 associates with the merozoite surface as well as rhoptries and expresses B-cell epitopes conserved among otherwise antigenically different B. bovis strains. An amino-terminal 307-amino-acid domain of the molecule that is highly conserved in the B. bigemina RAP-1 homolog did not contain cross-reactive B-cell epitopes. The studies reported here demonstrate that B. bovis RAP-1 is strongly immunogenic for T helper (Th) cells from B. bovis-immune cattle and that like B-cell epitopes, Th-cell epitopes are conserved in different B. bovis strains but not in B. bigemina RAP-1. Lymphocytes from cattle immune to challenge with the Mexico strain of B. bovis proliferated against recombinant B. bovis RAP-1 protein derived from the Mexico strain. T-cell lines established by stimulating lymphocytes with recombinant RAP-1 protein responded against B. bovis, but not B. bigemina, merozoites. T-cell lines established by repeated stimulation of lymphocytes with B. bovis membrane antigen proliferated strongly against RAP-1, demonstrating the immunodominant nature of this protein. RAP-1-specific CD4+ T cell clones recognized Mexico, Texas, Australia, and Israel strains of B. bovis but neither B. bigemina merozoites nor recombinant B. bigemina RAP- 1. Analysis of cytokine mRNA in RAP-1-specific Th cell clones revealed strong expression of gamma interferon but little or no expression of interleukin-2 (IL-2), IL-4, or IL-10. Gamma interferon production was confirmed by enzyme-linked imunosorbent assay. These results indicate the potential to use selected B. bovis RAP-1 peptides as immunogens to prime for strong, anamnestic, strain-cross-reactive type 1 immune responses upon exposure to B. bovis.

CD4+ T-helper lymphocyte responses against Babesia bigemina rhoptry-associated protein I

A multigene family of 58- to 60-kDa proteins, which are designated rhoptry-associated protein 1 (RAP-1) and which come from the parasites Babesia bigemina and Babesia bovis, is a target for vaccine development. The presence of multiple gene copies and conserved sequences and epitopes of RAP-1 implies that these proteins are functionally important for the survival of these parasites. Furthermore, it was previously shown that B. bigemina RAP-1 induced partial protection against challenge infection. However, the lack of correlation between protective immunity to B. bigemina infection and antibody titers against a merozoite surface-exposed, neutralization-sensitive epitope of B. bigemina RAP-1 indicated the potential importance of RAP-1-specific T helper (Th) cells in the observed protection. To begin to understand the mechanism of RAP-1-induced protective immunity, RAP-1-specific T-cell responses were characterized in cattle. Vigorous and sustained proliferative responses of peripheral blood mononuclear cells from native RAP-1-immunized cattle were observed. The anamnestic response in immunized cattle was specific for B. bigemina RAP-1 and predominantly comprised CD4+ T cells, which upon cloning expressed type 1 cytokine mRNA profiles and high levels of gamma interferon protein. The T cells responded to both native and recombinant forms of RAP-1, indicating the potential to use recombinant protein or epitopes derived therefrom as a vaccine that could evoke specific recall responses after exposure to natural infection. The differential responses of peripheral blood mononuclear cells and seven Th-cell clones derived from RAP-1-immunized cattle to different Central American strains of B. bigemina indicated the presence of at least one conserved and one variable Th-cell epitope. The lack of response to B. bovis RAP-1 indicated that a strictly conserved 14-amino-acid peptide shared by the two babesial species was not immunogenic for Th cells in these experiments. However, the Th-cell epitope conserved among strains of B. bigemina may be a useful component of a RAP-1 subunit vaccine.