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.

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.