Susceptibility of TNF-alpha-deficient mice to Trypanosoma congolense is not due to a defective antibody response

Immunomodulatory potential of Sarcophaga argyostoma larval hemolymph as a natural alternative to berenil in treating Trypanosoma evansi in vivo

This study compared effects of diminazene aceturate (berenil), commonly used to treat domestic animals infected with Trypanosoma evansi, with the hemolymph of Sarcophaga argyostoma larva. The hemolymph may be acting as a possible natural alternative to berenil, based on immunomodulation mediated inflammatory response. Inflammatory mediators and histopathological changes in liver, kidney, and spleen of albino mice experimentally infected with T. evansi were studied. Mice were divided into five groups: G1, uninfected, untreated (negative control); G2, T. evansi infected (positive control); G3, infected and treated with berenil; G4, infected and treated with hemolymph; G5, infected and treated with hemolymph 3 days before infection (prophylactic group). Animals in (G4) and (G5) exhibited a significant overall reduction in serum levels of IFN-γ. However, the reduction in TNF-α and IL-6 levels was more limited compared to (G2) and (G3). Notably, an elevation in IL-10 levels was observed compared to animals in other groups. Furthermore, the groups treated with hemolymph demonstrated an alleviation of T. evansi infection in contrast to the other groups. This study highlights that the administration of Sarcophaga argyostoma larval hemolymph at a dosage of 0.5 ml/kg significantly inhibited T. evansi organisms in vivo, showcasing a pronounced trypanocidal effect.

A review on acute phase response in parasitic blood diseases of ruminants

Parasitic blood diseases (theileriosis, babesiosis, anaplasmosis, and trypanosomiasis) are common in regions where the distributions of the hosts, parasites, and vectors are convergent. They endanger animal production, and a few are also harmful to public health. The acute phase reaction (APR) is a complex, non-specific reaction that occurs in various events, including surgical trauma, infection, stress, inflammation, and neoplasia. To understand pathogenesis, we must study APR effects and acute phase proteins (APPs) alterations in naturally occurring and experimental infections. The elevation of haptoglobin (Hp), Serum amyloid A (SAA), and fibrinogen concentrations was markedly significant in bovine and ovine theileriosis. Hp, SAA, ceruloplasmin, and fibrinogen concentrations in anaplasmosis were dramatically elevated. A significant increase in SAA was observed in bovine babesiosis, while ovine babesiosis showed a significant rise in sialic acid levels. In cases of trypanosomiasis caused by T. vivax, there have been reports of elevated levels of Hp, complement C3, and antitrypsin. Improving our understanding of APR could result in more effective methods for diagnosis, treatment, control, and eradication of diseases. The article provides an overview of APPs alterations and other inflammation-related parameters (some cytokines, adenosine deaminase, and sialic acids) in parasitic blood diseases of ruminants.

A Preliminary Study on the Relationship between Parasitaemia and Cytokine Expression of Peripheral Blood Cells in Trypanosoma vivax-Experimentally Infected Cattle

Simple Summary

Infections by Trypanosoma vivax in livestock have been reported with increasing frequency worldwide. Nevertheless, information regarding the immune response during the infection is scarce. Regarding that, cytokines play an important role as inflammation modulators, influencing the outcome of trypanosomosis. This study aimed to evaluate host cytokine production during T. vivax infection, in order to assess the increase or decrease of selected cytokines with the cattle’s ability to control the infection. While animals that showed an increase in IL-6 and IFNγ managed T. vivax parasitaemia satisfactorily, cattle that showed reduction of IL-1β, IL-2 and TNFα did not control the parasite multiplication. The presented results are preliminary and shed some light on the role of cytokines during T. vivax-infection.

Abstract

Trypanosoma vivax outbreaks have been reported with increasing frequency worldwide, causing significant economic losses in livestock. Though several studies have suggested that cytokine responses may influence infection caused by Trypanosoma sp., their exact role remains unclear and may vary according to the animal species and parasite strain. The present study aimed to evaluate cytokine expression of peripheral blood cells from three Girolando dairy cows experimentally infected with T. vivax. For this purpose, blood samples were collected prior to the inoculation on the day of inoculation (D0), the day after inoculation (D1), and then every seven days up to 119 days after infection (DAI). Each animal presented a unique pattern of cytokine expression. While a tendency of a Th1 cytokine response was observed during the patent phase (presence of circulating parasites), an increase of Th2 cytokine expression was found at the beginning of the sub-patent phase (low parasitaemia or aparasitaemic periods). In animals that presented a better control of parasitaemia, IL-6 and IFNγ increased during most of the trial period. On the other hand, the cow that presented reduction of IL-1β, IL-2, and TNFα during the entire period did not control parasitaemia properly. A balance between the Th1 and Th2 profile is beneficial for parasite control and animal health. The results found in the present study are a first step towards elucidating the dynamics of cattle’s inflammatory response against T. vivax, requiring future studies focusing on the role of key cytokines on the controlling of parasitaemia in different stages of bovine trypanosomosis.

Comparative pathology of mice infected with high and low virulence of Indonesian Trypanosoma evansi isolates

Mice infected with T. evansi cause various clinical manifestations and histopathological changes. The aim of this study was to compare the histopathological lesions of mice infected with T. evansi Bang 87 isolates (high virulence) and Pml 287 isolates (low virulence). A total of 15 susceptible mice (DDY) were divided into three groups (five mice/group): Groups I and II each were infected with 10⁴ T. evansi of high virulence (Bang87) and low virulence (Pml 287), respectively, whereas group III served as a control group. A total of three mice from group I, and one mouse from each group II and III were killed at 4 dpi. A total of two mice from each group II and III were killed at 24 dpi. Two remaining mice from each group were observed until succumb. Mice of group I and group II at 4 dpi showed no gross lesions. However, mice of group I showed very acute animal death at 5 dpi and showed mild to moderate histopathological lesions at 4 dpi, namely non-suppurative encephalitis, non-suppurative pneumonia, hepatitis non-suppurative with intravascular trypanosomiasis, tubular degeneration and necrosis. Group II showed chronic death at 26 dpi with significant gross pathological changes at 24 dpi in spleen (swelling 10 times than normal size) accompanied by severe non-suppurative encephalitis, cholangiohepatitis non-suppurative and bile duct proliferation, diffused splenic necrosis. The result of this study is expected to be used as a basis for improved treatment management in cattle infected with high virulence T. evansi isolates that are need to be handled appropriately to avoid fatal consequences.

Cytokine gene expression and pathology in mice experimentally infected with different isolates of Trypanosoma evansi

Aim of the present study was to assess the cytokine gene expression in liver, kidney and spleen and histopathological changes in mice infected with buffalo and dog isolates of Trypanosoma evansi. Forty-four Swiss albino mice was divided into eleven groups of four mice each and injected subcutaneously with 1 × 10⁵ trypanosomes of buffalo and dog isolate to twenty mice each, four mice served as control. Mice were examined for clinical signs, blood smear for trypanosome counts. Blood for PCR, liver, kidney, spleen, heart, lung, testis and abdominal muscle for histopathology and liver, kidney, spleen for cytokine gene expression studies, were collected. Mice showed dullness, lethargy, hunched back, sluggish movements on D4 and D5 in buffalo and dog isolate, respectively. Parasite count in blood varied between the two isolates of T. evansi. By PCR, trypanosome DNA was detected on D1 and D2 for buffalo and dog isolate, respectively. Splenomegaly was observed in mice infected with buffalo isolate but not with dog isolate. Histopathological changes were observed in liver, kidney, spleen and heart of mice but no changes in testis and abdominal muscles. Blood vessels of liver, heart, lung showed presence of trypanosomes in mice infected with buffalo isolate but not for dog isolate. Cytokine gene expression of IL-2, IL-4, IL-6, IL-12, TNF-α and IFN-γ increased in liver, kidney and spleen in both these isolates. However, the buffalo isolate exhibited pronounced increase in cytokine gene expression when compare to dog isolate of T. evansi. Anti-inflammatory cytokine gene IL-10 showed 50-60 and 10-20 folds increment in buffalo and dog isolates, respectively. This is the first report of IL-4, IL-6, IL-10 and IL-12 cytokine changes in mice infected with T. evansi. A variation in pathogenicity between buffalo and dog isolates was recorded indicating buffalo isolate of T. evansi remained more pathogenic in mice.

Expression of regulatory dendritic cell-related cytokines in cattle experimentally infected with Trypanosoma evansi

Trypanosoma evansi causes wasting disease in many livestock. T. evansi infection gives rise to inflammatory immune responses, which contribute to the development of inflammation-associated tissue injury. We previously reported that regulatory dendritic cells (DCs), which act as potential regulators of inflammation, were activated in infected mice and transfer of regulatory DCs to infected mice prolonged their survival. However, the kinetics of regulatory DCs in cattle, which are natural hosts of T. evansi, remained unclear. In this study, we report that the expressions of CCL8 and IL-10, which promote the development of regulatory DCs, were up-regulated in cattle experimentally infected with T. evansi. This finding is potentially useful for studying the control strategy of T. evansi infection in cattle.

CpG-ODN class C-mediated immunostimulation and its potential against Trypanosoma evansi in equines

Trypanosoma evansi is the causative agent of surra, which is the most common and widespread trypansomal disease. The infection is mainly restricted to animals, but it has also been documented in human. Trypanosomes possess the thick immunogenic surface coat known as variant surface glycoprotein (VSG). The parasite modifies the VSG constantly resulting in continuous antigenic variations and thus evades the host immune response. Due to antigenic variations, vaccination against trypanosomosis is not useful. Therefore, alternate strategies to augment the immune response are required. CpG-ODN class-C has combined immune effects of both A and B classes of CpG-ODN. In this study, we observed that CpG-ODN class-C stimulated horse peripheral blood mononuclear cells (PBMC) induce the expression of interferon-α (IFN-α), tumor necrosis factor-α (TNF-α), IL-12 and nitric oxide (NO) indicating enhanced innate immune response. We have for the first time demonstrated that co-culture of CpG-ODN with T. evansi antigen induces lymphocyte proliferative responses and result in a synergistic effect in eliciting the immune response.

Comparative in vitro toll-like receptor ligand induced cytokine profiles of Toda and Murrah buffaloes-Identification of tumour necrosis factor alpha promoter polymorphism

The objective of this study was to assess cytokine production upon activation of pattern recognition receptors responsible for sensing bacterial and viral pathogen associated molecular patterns in two genetically diverse buffalo breeds, Toda and Murrah. A very limited molecular-epidemiological analysis showed a higher prevalence of Anaplasma and Theileria in Murrah than Toda buffaloes. Toda buffalo peripheral blood mononuclear cells (PBMC) produced significantly higher levels of IFN γ and/or TNF α mRNAs in response to peptidoglycan, poly I:C, lipopolysaccharide, imiquimod and CpG. Flagellin stimulation did not result in any significant differences in the expression levels of the cytokines tested between these breeds. The levels of ligand induced IFN γ and TNF α mRNA and proteins also correlated except when induced with CpG. The proximal promoter region of TNF α across these two breeds were also sequenced to detect SNPs and promoter assay performed to determine their role in altering the transcriptional activity. Two polymorphisms were identified at -737 (T/A) and -1092 (G/T) positions in Toda buffalo TNF α promoter and promoter assay revealed higher transcription activity in Toda buffalos than in Murrah. This suggests that disease tolerance of these buffalo breeds could be due to the differences in their cytokine transcription levels in response to the respective PAMPs that may be at least in part determined by polymorphisms in the cytokine promoter regions.

Cytokines in rats experimentally infected with Trypanosoma evansi

The aim of this study was to measure the levels of interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), interleukin 1 (IL-1) and interleukin 6 (IL-6) in the serum of rats experimentally infected with Trypanosoma evansi and to correlate these levels with hematological parameters. Initially, 48 rats (group T) were intraperitoneally inoculated with cryopreserved blood containing 1×10(6) trypomastigotes per animal. Twenty-eight animals (group C) were used as negative controls and received 0.2 mL of saline by the same route. The experimental groups were formed according to the time after infection and the degree of parasitemia as follows: four control subgroups (C3, C5, C10 and C20) with seven non-inoculated animals each and four test subgroups (T3, T5, T10 and T20) with 10 animals each inoculated with T. evansi. The blood samples were collected by cardiac puncture at days 3 (C3, T3), 5 (C5, T5), 10 (C10, T10) and 20 (C20, T20) post-infection (PI) to perform the complete blood count and the determination of IFN-γ, TNF-α, IL-1 and IL-6 levels using an ELISA quantitative sandwich. Infected rats showed normocytic normochromic anemia during the experimental period. T. evansi infection in rats caused a serum increase (P<0.01) of IFN-γ, TNF-α, IL-1 and IL-6 levels at days 3, 5, 10 and 20 PI compared to the controls. The multiple linear regressions showed a reduction of 24% in the hematocrit as a consequence of the increased IFN-γ, TNF-α and IL-1. Therefore, we conclude that the infection caused by T. evansi causes an increase in the pro-inflammatory cytokines. These results suggest a synergism among IL-1, TNF-α and IFN-γ contributing to the development of anemia. This increase is associated with the regulation of immune responses against the parasite.

Clinical chemistry of congenic mice with quantitative trait loci for predicted responses to Trypanosoma congolense infection

Trypanosoma congolense is a protozoan parasite that causes severe diseases in livestock. Three major quantative trait loci (QTL), Tir1, Tir2, and Tir3, control the survival time of mice after infection with T. congolense. Congenic mice carrying the C57BL/6 resistance alleles on the A/J background were developed for each of these loci. The congenic mice were used to physically map the regions containing the QTL gene(s) and to investigate the physiological effect of each locus. Clinical chemistry data for infected A/J, C57BL/6, and BALB/c mice were obtained for 15 analytes at five time points. Congenic mice were assessed for survival, parasitemia, and anemia as well as seven clinical-chemical analytes. The survival times were significantly increased in the Tir1 and Tir2 mice but not Tir3 congenic mice. The survival time of the parental inbred mice correlated negatively with parasitemia but positively with alanine aminotransferase activities in serum, suggesting that inflammatory reactions in the liver had a beneficial effect possibly associated with reduced parasitemia. However, there was no difference in parasitemia or liver enzyme activities of Tir1 and Tir2 congenic mice relative to their controls, showing that survival, parasitemia, and degree of liver damage are not associated with each other, despite the correlation in the parental lines. These data suggest that the congenic loci affect survival but do not affect control of parasite number. They may therefore act by limiting the pathological consequences of T. congolense infection.

Interleukin-12p70 deficiency increases survival and diminishes pathology in Trypanosoma congolense infection

To determine the immunological role played by interleukin (IL)-12 family members in Trypanosoma congolense infection, IL-12p35(-/-), IL-12p40(-/-), and IL-12p35(-/-)/p40(-/-) mice were used. While the latter 2 strains lack all IL-12 homologues, IL-12p35(-/-) mice still produce IL-12p80 homodimers and IL-23. Compared with wild-type mice, all infected IL-12-deficient mouse strains showed prolonged survival, whereas parasitemia levels were unaltered. Interferon (IFN)-gamma production in IL-12-deficient mice was strikingly reduced during the acute and chronic stages of infection, coinciding with significantly reduced chronic-stage hepatocellular damage, as demonstrated by histological analysis and plasma aspartate transaminase measurements. In contrast, IL-10 production was not affected by the absence of IL-12. Taken together, these results show that, during T. congolense infection, the absence of IL-12, but not the IL-12p80 homodimer or IL-23, leads to a reduction in IFN-gamma production, which reduces hepatic pathology and improves host survival in conjunction with IL-10 without negatively affecting parasitemia control.

African Trypanosomiasis: Naturally Occurring Regulatory T Cells Favor Trypanotolerance by Limiting Pathology Associated with Sustained Type 1 Inflammation

Tolerance to African trypanosomes requires the production of IFN-gamma in the early stage of infection that triggers the development of classically activated macrophages controlling parasite growth. However, once the first peak of parasitemia has been controlled, down-regulation of the type 1 immune response has been described. In this study, we have evaluated whether regulatory T cells (Tregs) contribute to the limitation of the immune response occurring during Trypanosoma congolense infection and hereby influence the outcome of the disease in trypanotolerant C57BL/6 host. Our data show that Foxp3+ Tregs originating from the naturally occurring Treg pool expanded in the spleen and the liver of infected mice. These cells produced IL-10 and limited the production of IFN-gamma by CD4+ and CD8+ effector T cells. Tregs also down-regulated classical activation of macrophages resulting in reduced TNF-alpha production. The Treg-mediated suppression of the type 1 inflammatory immune response did not hamper parasite clearance, but was beneficial for the host survival by limiting the tissue damages, including liver injury. Collectively, these data suggest a cardinal role for naturally occurring Tregs in the development of a trypanotolerant phenotype during African trypanosomiasis.

Pathology of Tnf-deficient mice infected with Plasmodium chabaudi adami 408XZ

Tumor necrosis factor alpha (Tnf) plays a pleiotropic role in murine malaria. Some investigations have correlated Tnf with hypothermia, hyperlactatemia, hypoglycemia, and a suppression of the erythropoietic response, although others have not. In this study, we have evaluated parasitemia, survival rate and several pathological features in C57BL/6JTnf(-/-) and C57BL/6JTnf(+/+) mice after infection with Plasmodium chabaudi adami 408XZ. Compared to the C57BL/6JTnf(+/+) mice, C57BL/6JTnf(-/-) mice showed increased parasitemia and decreased survival rate, whereas blood glucose, blood lactate and body weight were not significantly different. However, C57BL/6JTnf(-/-) mice suffered significantly more from severe anemia and hypothermia than C57BL/6JTnf(+/+) mice. These results suggest that Tnf is an important mediator of parasite control, but not of anemia development. We hypothesize that the high mortality observed in the Tnf knock-out mice is due to increased anemia and pathology as a direct result of increased levels of parasitemia.

Bovine trypanotolerance: A natural ability to prevent severe anaemia and haemophagocytic syndrome?

Trypanotolerance is the capacity of certain West-African, taurine breeds of cattle to remain productive and gain weight after trypanosome infection. Laboratory studies, comparing Trypanosoma congolense infections in trypanotolerant N'Dama cattle (Bos taurus) and in more susceptible Boran cattle (Bos indicus), confirmed the field observations. Experiments using haemopoietic chimeric twins, composed of a tolerant and a susceptible co-twin, and T cell depletion studies suggested that trypanotolerance is composed of two independent traits. The first is a better capacity to control parasitaemia and is not mediated by haemopoietic cells, T lymphocytes or antibodies. The second is a better capacity to limit anaemia development and is mediated by haemopoietic cells, but not by T lymphocytes or antibodies. Weight gain was linked to the latter mechanism, implying that anaemia control is more important for survival and productivity than parasite control. Anemia is a marker for a more complex pathology which resembles human haemophagocytic syndrome: hepatosplenomegaly, pancytopenia and a large number of hyperactivated phagocytosing macrophages in bone marrow, liver and other tissues. Thus, mortality and morbidity in trypanosome-infected cattle are primarily due to self-inflicted damage by disproportionate immune and/or innate responses. These features of bovine trypanotolerance differ greatly from those in murine models. In mice, resistance is a matter of trypanosome control dependent on acquired immunity. However, a model of anaemia development can be established using C57BL/6J mice. As in cattle, the induction of anaemia was independent of T cells but its development differed with different trypanosome strains. Identification of the molecular pathways that lead to anaemia and haemophagocytosis should allow us to design new strategies to control disease.

Protective effects of antimicrobial peptides derived from the beetle Allomyrina dichotoma defensin on endotoxic shock in mice

Synthetic peptides, Arg-Leu-Tyr-Leu-Arg-Ile-Gly-Arg-Arg-NH2 (peptide A) and Arg-Leu-Arg-Leu-Arg-Ile-Gly-Arg-Arg-NH2 (peptide B), derived from the beetle Allomyrina dichotoma defensin, have not only antimicrobial activities but also anti-inflammatory effects by inhibiting tumour necrosis factor-alpha(TNF-alpha) production. In the present study, we evaluated the lipopolysaccharide (LPS)-binding activities and the protective effects of these peptides on LPS-induced lethal shock in d-galactosamine (GalN)-sensitized mice. These peptides were shown to bind to erythrocytes coated with LPS and the binding activity of peptide A to LPS was significantly higher than those of peptide B and polymyxin B. Mice were injected intraperitoneally with peptide A or B at doses of 25, 50, 100 and 150 mg/kg before an injection of Salmonella abortusequi LPS (5 microg/kg) and GalN (1 g/kg) (LPS+GalN). All of wild-type mice died within 24 h after challenged with LPS+GalN. All of TNF-alpha-deficient mice challenged with LPS+GalN survived. An injection of peptide A immediately after challenge with LPS+GalN resulted in significantly improved survival rates in a dose dependent manner. Peptide B showed only minor protection. The levels of TNF-alpha in the ameliorated mice by peptide A were significantly lower than those of challenge control, suggesting a suppressive effect of peptide A on TNF-alpha production. Furthermore, peptide A-treated mice showed significantly lower levels of asparate aminotransferase and alanine aminotransferase when compared to challenge control. Concordantly, hemorrhage and necrosis in the liver of peptide A-treated mice were less apparent than those of untreated control mice. These results suggest that peptide A has a protective effect on LPS-induced mortality in this mouse model.

The secretion of acute phase proteins and inflammatory cytokines during Trypanosoma congolense infection is not affected by the absence of the TNF-alpha gene

Tumor necrosis factor-alpha (TNF-alpha) plays a role in the host's defence against infections with African trypanosomes. It helps to control the blood stream form of the parasite and in Trypanosoma congolense infections, it also prolongs survival. The mechanisms by which this cytokine can influence parasitemia and survival are unknown. Therefore, the levels of acute phase proteins and other inflammatory cytokines were monitored in trypano-tolerant wild-type and TNF-alpha-deficient mice during a T. congolense infection. The titres of ceruloplasmin (CP), alpha1-acid glycoprotein (AGP) and serum amyloid P (SAP) increased and reached their peaks at 11 days post-infection, when the first peak of parasitemia was observed. No significant differences were observed in the acute phase protein profiles between the two mouse strains. Also the profiles of serum titres of IFN-gamma, IL-1alpha, IL-6 and IL-10 were not significantly different. Our present results indicate that acute phase protein and cytokine responses can be induced in the absence of TNF-alpha during a T. congolense infection in mice, and that the susceptibility of the TNF-alpha-deficient mice is not due to modulation of expression of these molecules.