Trypanosoma cruzi antigen immunization induces a higher B cell survival in BALB/c mice, a susceptible strain, compared to C57BL/6 B lymphocytes, a resistant strain to cardiac autoimmunity

Identification of phenotypic markers of B cells from patients with Chagas disease

Chagas disease was discovered more than a hundred years ago, but its pathogenesis is still not completely understood. Autoimmunity is one of the mechanisms shown to contribute to its pathogenesis, which may indicate an important participation of B lymphocytes. Patients with Chagas disease have shown increased percentage of B cells producing IL-10. However, there are no reports of the phenotypic markers of B cells producing IL-10 in patients with Chagas disease. For the first time in the literature, we evaluated the phenotypic profile of distinct markers of B cells from peripheral blood of noninfected individuals and patients with Chagas disease. Our results showed that patients with Chagas disease had a higher expression of CD21 and CD24 on the surface of CD19+ B cells, while CD43 and CD23 were expressed equally in all groups. Moreover, the expression of MHC-II (HLA-DR), CD80, CD86, caspase-3, granzyme B and intracellular IL-10 and TGF-β by CD19+ B cells was higher in patients with Chagas disease. The results of IL-10 production within CD19+ CD5+ CD1d+ B cells showed a higher percentage of this cytokine in patients with Chagas disease. Thus, our data bring a new knowledge about distinct markers of B cells in immune responses of Chagas disease.

Cardiac damage induced by immunization with heat-killed Trypanosoma cruzi is not antibody mediated

Cardiac inflammation that develops during infection with Trypanosoma cruzi may result in part from autoimmunity, which may occur after bystander activation, after parasite-induced cardiomyocyte damage, or molecular mimicry. A/J mice infected with T. cruzi or immunized with heat-killed T. cruzi (HKTC) develop strong autoimmunity accompanied by cardiac damage. To determine whether this cardiac damage occurs via an antibody-dependent mechanism, we analysed T. cruzi-infected and HKTC-immunized mice for the presence of autoantibodies, cardiac antibody deposition, and serum cardiac troponin I as a measure of cardiac damage. We also performed a serum transfer experiment in which sera from T. cruzi-infected and T. cruzi-immunized mice (and controls) were transferred into naïve recipients, which were then analysed for the presence of antibodies and serum troponin. Unlike T. cruzi-infected mice, T. cruzi-immunized mice did not show significant antibody deposition in the myocardium. These results indicate that antibody deposition does not precede cardiac damage and inflammation in mice immunized with or infected with T. cruzi. Serum adoptive transfer did not induce cardiac damage in any recipients. Based on these findings, we conclude that the cardiac damage induced by immunization with HKTC is not mediated by antibodies.

Slam haplotype 2 promotes NKT but suppresses Vγ4+ T-cell activation in coxsackievirus B3 infection leading to increased liver damage but reduced myocarditis

There are two major haplotypes of signal lymphocytic activation molecule (Slam) in inbred mouse strains, with the Slam haplotype 1 expressed in C57Bl/6 mice and the Slam haplotype 2 expressed in most other commonly used inbred strains, including 129 mice. Because signaling through Slam family receptors can affect innate immunity [natural killer T cell (NKT) and γ-δ T-cell receptor], and innate immunity can determine susceptibility to coxsackievirus B3 (CVB3) infection, the present study evaluated the response of C57Bl/6 and congenic B6.129c1 mice (expressing the 129-derived Slam locus) to CVB3. CVB3-infected C57Bl/6 male mice developed increased myocarditis but reduced hepatic injury compared with infected B6.129c1 mice. C57Bl/6 mice also had increased γδ(+) and CD8(+)interferon-γ(+) cells but decreased numbers of NKT (T-cell receptor β chain + mCD1d tetramer(+)) and CD4(+)FoxP3(+) cells compared with B6.129c1 mice. C57Bl/6 mice were infected with CVB3 and treated with either α-galactosylceramide, an NKT cell-specific ligand, or vehicle (dimethyl sulfoxide/PBS). Mice treated with α-galactosylceramide showed significantly reduced myocarditis. Liver injuries, as determined by alanine aminotransferase levels in plasma, were increased significantly, confirming that NKT cells are protective for myocarditis but pathogenic in the liver.

Different peripheral neuroendocrine responses to Trypanosoma cruzi infection in mice lacking adaptive immunity

Trypanosoma cruzi infection in mice triggers neuroendocrine responses that affect the course of the disease. To analyze the contribution of adaptive immunity to these responses, comparative studies between normal C57Bl/6J and recombinase activator gene 1 (RAG-1)-deficient mice, which lack mature B and T lymphocytes, were performed. There was no difference between both types of mice in basal body weight. Following infection, higher parasitemia, increased IL-1β and IL-6 blood levels, less marked changes in lymphoid organs weight, no cardiomegaly, and earlier mortality were observed in RAG-1-deficient, compared with normal mice. The response of the hypothalamus-pituitary-adrenal axis after infection occurred earlier and was more intense in RAG-1-deficient mice than in normal mice. Noradrenaline concentration and serotonergic metabolism in the spleen, lymph nodes, and heart differed between RAG-1-deficient and normal mice. Our studies indicate that the absence of adaptive immunity to T. cruzi influences the neuroendocrine response to the infection with this parasite.

Vaccine model of antiphospholipid syndrome induced by tetanus vaccine

Successful induction of antiphospholipid syndrome (APS) in two different non-autoimmune prone mouse strains, BALB/c and C57BL/6, was achieved by tetanus toxoid (TTd) hyperimmunization using different adjuvants (glycerol or aluminium hydroxide), and different adjuvant pretreatments (glycerol or Complete Freund’s Adjuvant (CFA)). APS had different manifestations of reproductive pathology in BALB/c and C57BL/6 mice: fetal resorption (as a consequence of extreme T-cell activation obtained in the course of pretreatment), and lowering of fecundity (as a consequence of polyclonal B-cell stimulation), respectively. In BALB/c mice fetal resorption coincided with glycerol and CFA pretreatments, while in C57BL/6 mice lowering of fecundity was most obvious in CFA-pretreated mice immunized with TTd in aluminium hydroxide. Both molecular mimicry and polyclonal B-cell activation occur in APS induction, with molecular mimicry effects being dominant in BALB/c mice, and polyclonal cell activation being dominant in C57BL/6 mice. Confirmation of molecular mimicry effects, which in the condition of T-cell stimulation generated fetal resorptions in the BALB/c strain, was achieved by passive infusion of monoclonal antibody (MoAb) T-26 specific for TTd and anti-β2-glycoprotein I obtained after TTd hyperimunization. High polyclonal B-cell activation in C57BL/6 mice prevented fetal resorption but induced fecundity lowering, as was the case in passive administration of MoAb T-26 in this mouse strain. Passive infusion of anti-idiotypic MoAb Y7 into C57BL/6 mice induced fetal resorptions and confirmed the above suggestion on the protective role of polyclonal B-cell stimulation in fetal resorptions.

The role of Toll-like receptors and adaptive immunity in the development of protective or pathological immune response triggered by the Trypanosoma cruzi protozoan

Trypanosoma cruzi, the causal agent of Chagas disease, is an intracellular protozoan parasite that predominantly invades macrophages and cardiomyocytes, leading to persistent infection. Several members of the Toll-like receptor family are crucial for innate immunity to infection and are involved in maintaining tissue homeostasis. This review focuses on recent experimental findings of the innate and adaptive immune response in controlling the parasite and/or in generating heart and liver tissue injury. We also describe the importance of the host’s genetic background in the outcome of the disease and emphasize the importance of studying the response to specific parasite antigens. Understanding the dual participation of the immune response may contribute to the design of new therapies for Chagas disease.