Systemic inflammatory Th1 cytokines during Trypanosoma cruzi infection disrupt the typical anatomical cell distribution and phenotypic/functional characteristics of various cell subsets within the thymus.

The thymus plays a crucial role in T cell differentiation, a complex process influenced by various factors such as antigens, the microenvironment and thymic architecture. The way the thymus resolves infections is critical, as chronic persistence of microbes or inflammatory mediators can obstruct the differentiation. Here, we illustrate that following inflammatory T helper 1 infectious processes like those caused by Candida albicans or Trypanosoma cruzi, single positive thymocytes adopt a mature phenotype. Further investigations focused on T. cruzi infection, reveal a substantial existence of CD44+ cells in both the cortical and medullary areas of the thymus at the onset of infection. This disturbance coincides with heightened interferon gamma (IFNγ) production by thymocytes and an increased cytotoxic capacity against T. cruzi-infected macrophages. Additionally, we observe a reduced exportation capacity in T. cruzi-infected mice. Some alterations can be reversed in IFNγ knockout mice (KO). Notably, the majority of these effects can be replicated by systemic expression of interleukin (IL)-12+IL-18, underlining the predominantly inflammatory rather than pathogen-specific nature of these phenomena. Understanding the mechanisms through which systemic inflammation disrupts normal T cell development, as well as subsequent T cell exportation to secondary lymphoid organs (SLO) is pivotal for comprehending susceptibility to diseases in different pathological scenarios.

The high identity of the Trypanosoma cruzi Group-I of trans-sialidases points them as promising vaccine immunogens.

Trans-sialidase (TS) superfamily of proteins comprises eight subgroups, being the proteins of Group-I (TS-GI) promising immunogens in vaccine approaches against Trypanosoma cruzi. Strikingly, TS-GI antigenic variability among parasite lineages and their influence on vaccine development has not been previously analyzed. Here, a search in GenBank detects 49 TS-GI indexed sequences, whereas the main infecting human different parasite discrete typing units (DTU) are represented. In silico comparison among these sequences indicate that they share an identity above 92%. Moreover, the antigenic regions (T-cell and B-cell epitopes) are conserved in most sequences or present amino acid substitutions that scarcely may alter the antigenicity. Additionally, since the generic term TS is usually used to refer to different immunogens of this broad family, a further in silico analysis of the TS-GI-derived fragments tested in preclinical vaccines was done to determine the coverage and identity among them, showing that overall amino acid identity of vaccine immunogens is high, but the segment coverage varies widely. Accordingly, strong H-2K, H-2I, and B-cell epitopes are dissimilarly represented among vaccine TS-derived fragments depending on the extension of the TG-GI sequence used. Moreover, bioinformatic analysis detected a set of 150 T-cell strong epitopes among the DTU-indexed sequences that strongly bind human HLA-I supertypes. In all currently reported experimental vaccines based on TS-GI fragments, mapping these 150 epitopes showed that they are moderately represented. However, despite vaccine epitopes do not present all the substitutions observed in the DTUs, these regions of the proteins are equally recognized by the same HLAs.  Interestingly, the predictions regarding global and South American population coverage estimated in these 150 epitopes are similar to the estimations in experimental vaccines when the complete sequence of TS-GI is used as an antigen. In silico prediction also shows that a number of these MHC-I restricted T-cell strong epitopes could be also cross-recognized by HLA-I supertypes and H-2Kb or H-2Kd backgrounds, indicating that these mice may be used to improve and facilitate the development of new TS-based vaccines and suggesting an immunogenic and protective potential in humans. Further molecular docking analyses were performed to strengthen these results. Taken together, different strategies that would cover more or eventually fully of these T-cell and also B-cell epitopes to reach a high level of coverage are considered.

Immunization With Lipopolysaccharide-Activated Dendritic Cells Generates a Specific CD8+ T Cell Response That Confers Partial Protection Against Infection With Trypanosoma cruzi.

Lipopolysaccharide (LPS) induces the activation of dendritic cells (DCs) throughout the engagement of toll-like receptor 4. LPS-activated DCs show increased capacity to process and present pathogen-derived antigens to activate naïve T cells. DCs-based vaccines have been successfully used to treat some cancer types, and lately transferred to the field of infectious diseases, in particular against HIV. However, there is no vaccine or DC therapy for any parasitic disease that is currently available. The immune response against Trypanosoma cruzi substantially relies on T cells, and both CD4+ and CD8+ T lymphocytes are required to control parasite growth. Here, we develop a vaccination strategy based on DCs derived from bone marrow, activated with LPS and loaded with TsKb20, an immunodominant epitope of the trans-sialidase family of proteins. We extensively characterized the CD8+ T cell response generated after immunization and compared three different readouts: a tetramer staining, ELISpot and Activation-Induced Marker (AIM) assays. To our knowledge, this work shows for the first time a proper set of T cell markers to evaluate specific CD8+ T cell responses in mice. We also show that our immunization scheme confers protection against T. cruzi, augmenting survival and reducing parasite burden in female but not male mice. We conclude that the immunization with LPS-activated DCs has the potential to prime significant CD8+ T cell responses in C57BL/6 mice independently of the sex, but this response will only be effective in female, possibly due to mice sexual dimorphisms in the response generated against T. cruzi.

Nasal immunization with a L. lactis-derived trans-sialidase antigen plus c-di-AMP protects against acute oral T. cruzi infection.

The new generation of vaccines for Chagas disease, are focused to induce both humoral and cellular response to effectively control Trypanosoma cruzi parasites. The administration of vaccine formulations intranasally has the advantage over parenteral routes that can induce a specific response at mucosal and systemic levels. This study aimed to evaluate and compare the immunogenicity and prophylactic effectiveness of two Trans-sialidase (TS)-based mucosal vaccines against T. cruzi administered intranasally. Vaccines consisted of a recombinant fragment of TS expressed in Lactococcus lactis formulated in two different adjuvants. The first, was an immunostimulant particle (ISPA, an ISCOMATRIX-like adjuvant), while the second was the dinucleotide c-di-AMP, which have shown immunostimulant properties at the mucosal level. BALB/c mice were immunized intranasally (3 doses, one every two weeks) with each formulation (TS + ISPA or TS + c-di-AMP) and with TS alone or vehicle (saline solution) as controls. Fifteen days after the last immunization, both TS + ISPA or TS + c-di-AMP induced an evident systemic humoral and cellular response, as judged by the increased plasma anti-TS IgG2a titers and IgG2a/IgG1 ratio and enhanced cellular response against TS. Plasma derived antibodies from TS + c-di-AMP also inhibit in vitro the invasion capacity of T. cruzi. Furthermore, specific secretory IgA was more enhanced in TS + c-di-AMP group. Protective efficacy was proved in vaccinated animals by an oral T. cruzi-challenge. Parasitemia control was only achieved by animals vaccinated with TS + c-di-AMP, despite all vaccinates groups showed enhanced CD8+IFN-γ+ T cell numbers. In addition, it was reflected during the acute phase in a significant reduction of tissue parasite load, clinical manifestations and diminished tissue damage. The better prophylactic capacity elicited by TS + c-di-AMP was related to the induction of neutralizing plasma antibodies and augmented levels of mucosal IgA since TS + ISPA and TS + c-di-AMP groups displayed similar immunogenicity and CD8+IFN-γ+ T-cell response. Therefore, TS + c-di-AMP formulation appears as a promising strategy for prophylaxis against T. cruzi.

Assessment of a combined treatment with a therapeutic vaccine and benznidazole for the Trypanosoma cruzi chronic infection.

The difficulties encountered in achieving treatments for chronic Chagas disease have promoted the investigation of new therapeutic strategies. In this study, we used two murine models of Trypanosoma cruzi chronic infection to determine the usefulness of applying a therapeutic vaccine alone or followed by benznidazole (Bz) chemotherapy. A vaccine formulation based on an N-terminal fragment of Trans-sialidase (TS) and Immunostimulant Particle Adjuvant (ISPA) - TSNt-ISPA was obtained. Firstly, the immunogenicity and protective capacity of TSNt-ISPA was demonstrated as a prophylactic formulation in an acute model of infection. Later, the formulation was assessed as a therapeutic vaccine alone or combined with (Bz) using two models of chronic infection. BALB/c mice chronically infected with Sylvio X10/4 or Tulahuen cl2 T. cruzi strains were not treated as control or treated only with the therapeutic vaccine TSNt-ISPA, with a combined treatment TSNt-ISPA+Bz (Bz applied after the vaccine), or only with Bz. The vaccination schedule consisted of TSNt-ISPA administration at days110, 120, and 130 post-infection (pi) and Bz administration was performed daily from day 140 to 170 pi. At day 273 pi, electrocardiographic (ECG) parameters, heart parasite load, myocarditis, and heart fibrosis were assessed. In both models, therapeutic administration of TSNt-ISPA reduced ECG alterations and the cardiac tissue damage observed in the chronic phase. Moreover, vaccine treatment significantly decreased heart parasite load in both Sylvio X10/4 and Tulahuen cl2 infected mice. The combined treatment, but not Bz or vaccine administration alone, allowed to restore ECG parameters in Tulahuen cl2 infected mice. The results indicate the usefulness of the therapeutic TSNt-ISPA formulation in BALB/c mice chronically infected with Sylvio X10/4 or Tulahuen cl2 strain. For the mice infected with T. cruzi Tulahuen cl2 strain, the combined treatment with the vaccine and Bz had a more positive effect on the course of heart disease than the individual treatments with the vaccine or Bz alone.

Chagas disease reactivation in rheumatologic patients: association with immunosuppressive therapy and humoral response.

Evidence for Chagas disease reactivation (CDR) in rheumatologic patients under rheumatologic treatments (RTs) is scarce. To screen and follow-up patients with rheumatic diseases and concomitant Chagas disease under RT to detect CDR and to describe a possible relationship between CDR and specific RT. An observational, longitudinal, prospective, consecutive study was carried out between 2018 and 2020. Included patients were evaluated during the follow-up for clinical and laboratorial manifestations of CDR. Direct blood parasitological examination (Strout method) and polymerase chain reaction (PCR) were employed to diagnose CDR. The dynamic of anti-T. cruzi-specific antibodies was also assessed by IHA and ELISA (total IgG and Anti-SAPA). Fifty-one patients were included (86% women). Rheumatoid arthritis was the predominant disease (57%). Classic DMARDs (86.3%) and corticosteroids (61%) were the most frequent RT. CDR was developed in 6 patients (11.7%), exhibiting both positive Strout and PCR. Symptomatic reactivation of CD (fever, asthenia, arthralgias, myalgias) occurred in two patients who had previously been diagnosed with it. Regardless of the different RT, all patients who experienced CDR had previously received more than ≥ 20 mg/day of prednisone equivalent. Despite immunosuppression, patients with CDR exhibited increased levels of specific anti-T. cruzi and anti-SAPA antibodies, which decreased after anti-parasitic treatment. CDR is possible in rheumatologic patients, especially after receiving high doses of corticosteroids. Since CDR symptoms may mimic rheumatic disease activity, monitoring of Chagas disease is highly recommended before, during and after immunosuppression. Key Points • Chagas disease reactivation (CDR) in the context of rheumatological treatment was associated to high doses of corticosteroids. • CDR was associated with an increase in anti-T. cruzi antibodies despite the immunosuppressive treatment. • Suspecting and anticipating CDR is mandatory in this patient population to diagnose and treat it.

Activation of PPARγ reduces N-acetyl-cysteine -induced hypercorticoidism by down-regulating MC2R expression into adrenal glands.

We previously demonstrated that oral supplementation with antioxidants induced hyperactivity of hypothalamus-pituitary-adrenal (HPA) axis, attested by hypercorticoidism, through an up-regulation of adrenocorticotrophic hormone (ACTH) receptors (MC2R) in adrenal. This study analyzed the role of peroxisome proliferator-activated receptor (PPAR)-γ on HPA axis hyperactivity induced by N-acetyl-cysteine (NAC). Male Swiss-Webster mice were orally treated with NAC for 1, 3, 5, 10, 15, or 18 consecutive days. The PPAR-γ agonist rosiglitazone and/or antagonist GW9662 were daily-injected i.p. for 5 consecutive days, starting concomitantly with NAC treatment. Rosiglitazone treatment inhibited NAC-induced adrenal hypertrophy and hypercorticoidism. Rosiglitazone also significantly reversed the NAC-induced increase in the MC2R expression in adrenal, but not steroidogenic acute regulatory protein (StAR). NAC treatment reduces the expression of PPARγ in the adrenals, but rosiglitazone did not restore the expression of this cytoprotective gene. In addition, GW9662 blocked the ability of rosiglitazone to decrease plasma corticosterone levels in NAC-treated mice. In conclusion, our findings showed that antioxidant supplementation induced a state of hypercorticoidism through down-regulation of PPARγ expression in the adrenals, in a mechanism probably related to a down-regulation of ACTH receptor expression.