Apolipoprotein A-I Truncations in Chagas Disease Are Caused by Cruzipain, the Major Cysteine Protease of Trypanosoma cruzi

Apolipoprotein A1 and Fibronectin Fragments as Markers of Cure for the Chagas Disease

Chagas disease (CD), endemic from Latin America, affects more than 8 million people, and the disease keeps spreading around the world due to population migrations. The treatment options for CD are currently limited to two drugs, benznidazole (BZ) and nifurtimox (Nfx), which are often unsatisfactory in chronically infected patients. To date, the only accepted marker of the cure is seroconversion (the disappearance of Trypanosoma cruzi antibodies in the patient's serum), which can take decades to occur, if ever. The lack of posttreatment test-of-cure often prevents appropriate patient counseling and limits the development of new drugs. Without a doubt, reliable biomarkers for parasitological cure are urgently needed. Several pieces of evidence suggest that apolipoprotein A1 and fibronectin fragments are produced during the infection as part of the process of T. cruzi cell invasion and can thus be used as its surrogate biomarkers. In this chapter, we present a standardized method to evaluate these fragments in serum using mass spectrometry and immunoblotting in CD patients for diagnosis, prognosis, and treatment assessment purposes.

Validation of Apolipoprotein A-1 and Fibronectin Fragments as Markers of Parasitological Cure for Congenital Chagas Disease in Children Treated With Benznidazole

Background

No reliable tests or validated biomarkers exist to ensure parasitological cure following treatment of Chagas disease (CD) patients chronically infected with Trypanosoma cruzi. As seroreversion, the only marker of cure, happens more quickly in children, we investigated the correlation between previously identified biomarkers and seroreversion in children.

Methods

Thirty CD children (age 1 month to 10 years) diagnosed as T. cruzi positive (time point S0) were treated with benznidazole (BZ) 5–8 mg/kg/d for 60 days. At least 2 serological tests were used to evaluate treatment efficacy from the end of treatment (S1) until seroreversion (S2). Thirty children (age 1 month to 10 years) and 15 adults were used as healthy controls (HCs). Immunoblot and a proteomic-based assay were used to validate previously identified fragments of apolipoprotein A-1 (ApoA1) and fibronectin (FBN) as CD biomarkers.

Results

Correlation between seroreversion and absence of ApoA1 and FBN fragments by immunoblot was observed in 30/30 (100%) and 29/30 (96.6%) CD children, respectively. ApoA1 and FBN fragments were absent at the end of BZ treatment in 20/30 (66.6%) and 16/30 (53.3%) children, respectively. Absence of fragments in serum profiles was confirmed by mass spectrometry. Using intact protein analysis, a 28 109-Da protein identified as full-length ApoA1 by tandem mass spectrometry was detected in HC serum samples.

Conclusions

These data confirm that ApoA1 and FBN fragments can discriminate between healthy and T. cruzi–infected samples. Correlation with seroreversion was shown for the first time; results suggest predictive capacity potentially superior to serology, making them potentially useful as surrogate biomarkers.

Recent clinical trials for the etiological treatment of chronic chagas disease: advances, challenges and perspectives

Chagas disease, a chronic systemic parasitosis caused by the Kinetoplastid protozoon Trypanosoma cruzi, is the first cause of cardiac morbidity and mortality in poor rural and suburban areas of Latin America and the largest parasitic disease burden in the continent, now spreading worldwide due to international migrations. A recent change in the scientific paradigm on the pathogenesis of chronic Chagas disease has led to a consensus that all T. cruzi-seropositive patients should receive etiological treatment. This important scientific advance has spurred the rigorous evaluation of the safety and efficacy of currently available drugs (benznidazole and nifurtimox) as well as novel anti-T. cruzi drug candidates in chronic patients, who were previously excluded from such treatment. The first results indicate that benznidazole is effective in inducing a marked and sustained reduction in the circulating parasites' level in the majority of these patients, but adverse effects can lead to treatment discontinuation in 10-20% of cases. Ergosterol biosynthesis inhibitors, such as posaconazole and ravuconazole, are better tolerated but their efficacy at the doses and treatment duration used in the initial studies was significantly lower; such results are probably related to suboptimal exposure and/or treatment duration. Combination therapies are a promising perspective but the lack of validated biomarkers of response to etiological treatment and eventual parasitological cures in chronic patients remains a serious challenge.

Recent advances in clinical parasitology diagnostics

Microscopy has several limitations in the diagnosis of parasitic infection. New technologies have emerged to address some of these limitations. We review recent advances in three key areas. The detection of enteric protozoa is a commonly requested test, particularly with increasing travel to and migration from endemic countries. Microscopy is slow and labor intensive and requires a high level of technical expertise. It also lacks both sensitivity and specificity. Recently developed nucleic acid amplification tests are automated and rapid and show superior accuracy. Proteomics shows promise for both the diagnosis of infections where parasite detection is difficult and the potential for accurate assessment of cure in these cases. Finally, rapid and simple diagnostic tests suitable for use in low-resource settings are now allowing for improved study and control of infection in endemic regions.

Trypanosoma cruzi infection and host lipid metabolism

Trypanosoma cruzi is the causative agent of Chagas disease. Approximately 8 million people are thought to be affected worldwide. Several players in host lipid metabolism have been implicated in T. cruzi-host interactions in recent research, including macrophages, adipocytes, low density lipoprotein (LDL), low density lipoprotein receptor (LDLR), and high density lipoprotein (HDL). All of these factors are required to maintain host lipid homeostasis and are intricately connected via several metabolic pathways. We reviewed the interaction of T. cruzi with each of the relevant host components, in order to further understand the roles of host lipid metabolism in T. cruzi infection. This review sheds light on the potential impact of T. cruzi infection on the status of host lipid homeostasis.