Differential gene expression of virulence factors modulates infectivity of TcI Trypanosoma cruzi strains

A nucleus-encoded dynamin-like protein controls endosymbiont division in the trypanosomatid Angomonas deanei

Angomonas deanei is a trypanosomatid of the Strigomonadinae. All members of this subfamily contain a single β-proteobacterial endosymbiont. Intriguingly, cell cycles of host and endosymbiont are synchronized. The molecular mechanisms underlying this notable level of integration are unknown. Previously, we identified a nucleus-encoded dynamin-like protein, called ETP9, that localizes at the endosymbiont division site of A. deanei. Here, we found by comparative genomics that endosymbionts throughout the Strigomonadinae lost the capacity to autonomously form a division septum. We describe the cell cycle-dependent subcellular localization of ETP9 that follows accumulation of the bacterium-encoded division protein FtsZ at the endosymbiont division site. Furthermore, we found that ETP9 is essential in symbiotic but dispensable in aposymbiotic A. deanei that lost the endosymbiont. In the symbiotic strain, ETP9 knockdowns resulted in filamentous, division-impaired endosymbionts. Our work unveiled that in A. deanei an endosymbiont division machinery of dual genetic origin evolved in which a neo-functionalized host protein compensates for losses of endosymbiont division genes.

Nitazoxanide: A Drug Repositioning Compound with Potential Use in Chagas Disease in a Murine Model

Chagas disease (ChD), caused by Trypanosoma cruzi, is the most serious parasitosis in the western hemisphere. Benznidazole and nifurtimox, the only two trypanocidal drugs, are expensive, difficult to obtain, and have severe side effects. Nitazoxanide has shown to be effective against protozoa, bacteria, and viruses. This study aimed to evaluate the nitazoxanide efficacy against the Mexican T. cruzi Ninoa strain in mice. Infected animals were orally treated for 30 days with nitazoxanide (100 mg/kg) or benznidazole (10 mg/kg). The clinical, immunological, and histopathological conditions of the mice were evaluated. Nitazoxanide- or benznidazole-treated mice had longer survival and less parasitemia than those without treatment. Antibody production in the nitazoxanide-treated mice was of the IgG1-type and not of the IgG2-type as in the benznidazole-treated mice. Nitazoxanide-treated mice had significantly high IFN-γ levels compared to the other infected groups. Serious histological damage could be prevented with nitazoxanide treatment compared to without treatment. In conclusion, nitazoxanide decreased parasitemia levels, indirectly induced the production of IgG antibodies, and partially prevented histopathological damage; however, it did not show therapeutic superiority compared to benznidazole in any of the evaluated aspects. Therefore, the repositioning of nitazoxanide as an alternative treatment against ChD could be considered, since it did not trigger adverse effects that worsened the pathological condition of the infected mice.

The many faces of parasite calreticulin

Calreticulin from parasites and its vertebrate hosts share ~50% identity and many of its functions are equally conserved. However, the existing amino acid differences can affect its biological performance. Calreticulin plays an important role in Ca2+ homeostasis and as a chaperone involved in the correct folding of proteins within the endoplasmic reticulum. Outside the endoplasmic reticulum, calreticulin is involved in several immunological functions such as complement inhibition, enhancement of efferocytosis, and immune upregulation or inhibition. Several parasite calreticulins have been shown to limit immune responses and promote infectivity, while others are strong immunogens and have been used for the development of potential vaccines that limit parasite growth. Furthermore, calreticulin is essential in the dialogue between parasites and hosts, inducing Th1, Th2 or regulatory responses in a species-specific manner. In addition, calreticulin participates as initiator of endoplasmic reticulum stress in tumor cells and promotion of immunogenic cell death and removal by macrophages. Direct anti-tumoral activity has also been reported. The highly immunogenic and pleiotropic nature of parasite calreticulins, either as positive or negative regulators of the immune response, render these proteins as valuable tools to modulate immunopathologies and autoimmune disorders, as well as a potential treatment of neoplasms. Moreover, the disparities in the amino acid composition of parasite calreticulins might provide subtle variations in the mechanisms of action that could provide advantages as therapeutic tools. Here, we review the immunological roles of parasite calreticulins and discuss possible beneficial applications.

Trypanosoma cruzi blood trypomastigotes induce intense skeletal and cardiac muscle damage and Th1/ Th2 immune response in the acute phase of mice infected by the oral route

Oral acquisition of Trypanosoma cruzi is a foodborne transmission by juices and fruits contaminated with metacyclic trypomastigotes (MT) or by the ingestion of wild reservoirs infected with blood trypomastigotes (BT). In Mexico, hunting and food consumption of wild animals are current practices, which could represent a risk factor for oral infection in the rural population. In this work, Balb/c mice were inoculated by oral route with BT of a highly virulent T. cruzi Mexican strain (DTU I) to evaluate the establishment of the infection, and the humoral and cellular immune response in the acute phase of the infection. We show that BT induces blood and tissue parasitism producing an inflammatory process in the heart and skeletal muscle and low parasitism and inflammation in the digestive tract of orally infected mice. Besides, in the acute phase, the BT promotes splenomegaly, intense damage in skeletal and cardiac muscles, a humoral response dominated by the IgG isotype, and the expression of pro-inflammatory cytokines.

How to get away with murder: The multiple strategies employed by pathogenic protozoa to avoid complement killing

Parasitic protozoa are eukaryotic unicellular organisms that depend on a variety of living organisms and can develop intra- and extracellularly inside their hosts. In humans, these parasites cause diseases with a significant impact on public health, such as malaria, toxoplasmosis, Chagas disease, leishmaniasis and amebiasis. The ability of a parasite in establishing a successful infection depends on a series of intricate evolutionarily selected adaptations, which include the development of molecular and cellular strategies to evade the host immune system effector mechanisms. The complement system is one of the main effector mechanisms and the first humoral shield of hosts innate immunity against pathogens. For unicellular pathogens, such as protozoa, bacteria and fungi, the activation of the complement system may culminate in the elimination of the invader mainly via 1- the formation of a pore that depolarizes the plasma membrane of the parasite, causing cell lysis; 2- opsonization and killing by phagocytes; 3- increasing vascular permeability while also recruiting neutrophils to the site of activation. Numerous strategies to avoid complement activation have been reported for parasitic protozoa, such as 1- sequestration of complement system regulatory proteins produced by the host, 2- expression of complement system regulatory proteins, 3- proteolytic cleavage of different complement effector molecules, 4- formation of a physical glycolipid barrier that prevents deposition of complement molecules on the plasma membrane, and 5- removal, by endocytosis, of complement molecules bound to plasma membrane. In this review, we revisit the different strategies of blocking various stages of complement activation described for the main species of parasitic protozoa, present the most recent discoveries in the field and discuss new perspectives on yet neglected strategies and possible new evasion mechanisms.

Molecular and Clinical Aspects of Chronic Manifestations in Chagas Disease: A State-of-the-Art Review

Chronic manifestations of Chagas disease present as disabling and life-threatening conditions affecting mainly the cardiovascular and gastrointestinal systems. Although meaningful research has outlined the different molecular mechanisms underlying Trypanosoma cruzi’s infection and the host-parasite interactions that follow, prompt diagnosis and treatment remain a challenge, particularly in developing countries and also in those where the disease is considered non-endemic. This review intends to present an up-to-date review of the parasite’s life cycle, genetic diversity, virulence factors, and infective mechanisms, as well as the epidemiology, clinical presentation, diagnosis, and treatment options of the main chronic complications of Chagas disease.