Location and expression kinetics of Tc24 in different life stages of Trypanosoma cruzi

Abstract

Tc24-C4, a modified recombinant flagellar calcium-binding protein of Trypanosoma cruzi, is under development as a therapeutic subunit vaccine candidate to prevent or delay progression of chronic Chagasic cardiomyopathy. When combined with Toll-like receptor agonists, Tc24-C4 immunization reduces parasitemia, parasites in cardiac tissue, and cardiac fibrosis and inflammation in animal models. To support further research on the vaccine candidate and its mechanism of action, murine monoclonal antibodies (mAbs) against Tc24-C4 were generated. Here, we report new findings made with mAb Tc24-C4/884 that detects Tc24-WT and Tc24-C4, as well as native Tc24 in T. cruzi on ELISA, western blots, and different imaging techniques. Surprisingly, detection of Tc24 by Tc24-C/884 in fixed T. cruzi trypomastigotes required permeabilization of the parasite, revealing that Tc24 is not exposed on the surface of T. cruzi, making a direct role of antibodies in the induced protection after Tc24-C4 immunization less likely. We further observed that after immunostaining T. cruzi–infected cells with mAb Tc24-C4/884, the expression of Tc24 decreases significantly when T. cruzi trypomastigotes enter host cells and transform into amastigotes. However, Tc24 is then upregulated in association with parasite flagellar growth linked to re-transformation into the trypomastigote form, prior to host cellular escape. These observations are discussed in the context of potential mechanisms of vaccine immunity.

Localized cardiac metabolic trajectories and post-infectious metabolic sequelae in experimental Chagas disease

“…Building on the knowledge that a balanced immune response correlates with reduced disease symptoms, we developed a vaccine containing recombinant Tc24-C4 protein combined with a TLR4 agonist adjuvant 23,24 . The Tc24 antigen is a T. cruzi flagellar calcium-binding antigen that is conserved across multiple discrete typing units of T. cruzi, and is expressed in extracellular trypomastigote and early intracellular amastigote stages 25,26 . When used as an immunotherapy in experimentally infected mice, the vaccine increased levels of antigen-specific CD8 + cells as well as the key cytokines IFNγ, IL-10, and IL-17A 24,27,28 .…”

Vaccine-linked chemotherapy improves cardiac structure and function in a mouse model of chronic Chagas disease

“…One promising vaccine candidate is the T. cruzi flagellar calcium binding protein designated Tc24 ( Dumonteil et al., 2012 ). This antigen is located along the inner leaflet of the flagellar membrane and is highly expressed in the extracellular trypomastigote form as well as in the non-dividing intracellular amastigote form of T. cruzi ( Versteeg et al., 2021 ). Several studies have demonstrated that recombinant protein based vaccines containing Tc24 antigens induce strong immune responses, with increased production of antigen specific CD8+ T cells as well as production of IFN-γ, IL-10 and IL-17A ( Barry et al., 2016 ; Seid et al., 2016 ; Jones et al., 2018 ; Cruz-Chan et al., 2021 ).…”

Harnessing RNA Technology to Advance Therapeutic Vaccine Antigens against Chagas Disease

“…A successful vaccine profile is expected to yield a T-helper 1 cell (Th1-type) response, characterized by the production of the pro-inflammatory cytokines IFN-γ, TNF-α, and IL-2, which are crucial for controlling T. cruzi infection, involved in activating immune cells, promoting inflammation, and enhancing the generation of a specific immune response. 46,47 In detail, IFN-γ and TNF-α promote the activation of macrophages and other immune cells.…”