Therapeutic Efficacy of a Subunit Vaccine in Controlling Chronic Trypanosoma cruzi Infection and Chagas Disease Is Enhanced by Glutathione Peroxidase Over-Expression

Abstract

Trypanosoma cruzi-induced oxidative and inflammatory responses are implicated in chagasic cardiomyopathy. In this study, we examined the therapeutic utility of a subunit vaccine against T. cruzi and determined if glutathione peroxidase (GPx1, antioxidant) protects the heart from chagasic pathogenesis. C57BL/6 mice (wild-type (WT) and GPx1 transgenic (GPxtg) were infected with T. cruzi and at 45 days post-infection (dpi), immunized with TcG2/TcG4 vaccine delivered by a DNA-prime/Protein-boost (D/P) approach. The plasma and tissue-sections were analyzed on 150 dpi for parasite burden, inflammatory and oxidative stress markers, inflammatory infiltrate and fibrosis. WT mice infected with T. cruzi had significantly more blood and tissue parasite burden compared with infected/GPxtg mice (n = 5-8, p<0.01). Therapeutic vaccination provided >15-fold reduction in blood and tissue parasites in both WT and GPxtg mice. The increase in plasma levels of myeloperoxidase (MPO, 24.7%) and nitrite (iNOS activity, 45%) was associated with myocardial increase in oxidant levels (3-4-fold) and non-responsive antioxidant status in chagasic/WT mice; and these responses were not controlled after vaccination (n = 5-7). The GPxtg mice were better equipped than the WT mice in controlling T. cruzi-induced inflammatory and oxidative stress markers. Extensive myocardial and skeletal tissue inflammation noted in chagasic/WT mice, was significantly more compared with chagasic/GPxtg mice (n = 4-6, p<0.05). Vaccination was equally effective in reducing the chronic inflammatory infiltrate in the heart and skeletal tissue of infected WT and GPxtg mice (n = 6, p<0.05). Hypertrophy (increased BNP and ANP mRNA) and fibrosis (increased collagen) of the heart were extensively present in chronically-infected WT and GPxtg mice and notably decreased after therapeutic vaccination. We conclude the therapeutic delivery of D/P vaccine was effective in arresting the chronic parasite persistence and chagasic pathology; and GPx1 over-expression provided additive benefits in reducing the parasite burden, inflammatory/oxidative stress and cardiac remodeling in Chagas disease.

Antigen-Based Nano-Immunotherapy Controls Parasite Persistence, Inflammatory and Oxidative Stress, and Cardiac Fibrosis, the Hallmarks of Chronic Chagas Cardiomyopathy, in A Mouse Model of Trypanosoma cruzi Infection

“…We found that SIRT1 activity was decreased in Chagas mice, and treatment with SIRT1 agonist (SRT1720) or inhibition of PARP1 (poly (adenosine diphosphate-ribose) polymerase 1) that competes with SIRT1 for substrates reduced oxidative and inflammatory stress in infected cells and mice [42]. Moreover, we noted increased efficacy of a therapeutic vaccine in infected mice overexpressing glutathione peroxidase than was observed in infected/wild type mice under similar conditions [39]. Thus, it is possible that nano-immunotherapy designed to achieve a rapid, short-term stimulation of type 1 cellular immunity to attack the persistent parasites, if complemented with antioxidants (e.g., PBN or resveratrol), would offer better efficacy in preserving the tissue homeostasis in Chagas disease.…”

“…Treatment with the anti-parasitic drug benznidazole in early-to-late phase of chronic infection is shown to control parasite persistence; however, it did not avert cardiac remodeling and deterioration of left ventricular function in humans and experimental models of Chagas disease [34][35][36]. Adjuvanting the benznidazole with antioxidants, for instance, PBN (phenyl-alpha-tert-butylnitrone), vitamin A, or by genetic overexpression of MnSOD (manganese superoxide dismutase) or GPx (glutathione peroxidase) has been shown to restrain oxidative insult along with parasite burden, and to improve cardiac function [37][38][39]. Likewise, treatment with sildenafil, an inhibitor of phosphodiesterase 5, provided cardioprotection through the preservation of cGMP-PKG activity and antioxidant-oxidant balance in chronically infected mice [40].…”

Vaccine-Linked Chemotherapy Improves Benznidazole Efficacy for Acute Chagas Disease

“…Limitations of this model were observed. Survival and parasite burdens in mouse models of Chagas disease give clear signals of vaccine efficacy (30,31,(57)(58)(59)(60). However, low-virulence T. cruzi infection models, in which overall survival is high, can elucidate key aspects of disease pathogenesis (61,62).…”

Cruzipain and Its Physiological Inhibitor, Chagasin, as a DNA-Based Therapeutic Vaccine Against Trypanosoma cruzi

“…Our results are in line with diverse approaches exhibiting the efficacy of several T. cruzi antigens (ASP-2, enolase, TSA-1, and Tc24) to control T. cruzi infection when they are tested as a therapeutic vaccine during the acute phase of the parasite infection ( 47 , 48 , 52 – 54 ). Nevertheless, only a few groups evaluated the performance of a therapeutic vaccine when it is administered during the chronic phase of T. cruzi infection ( 38 , 43 , 55 – 57 ). In that regard, the effectiveness of the multicomponent therapeutic vaccine SChg+SCz, when it is orally administered during the chronic phase of the infection, becomes even more relevant.…”