Histopathological study in cardiac tissue of rodents infected with Trypanosoma cruzi, captured in suburbs of Mérida, México

Mycobacterium bovis BCG as immunostimulating agent prevents the severe form of chronic experimental Chagas disease

Introduction

There is currently no vaccine against Chagas disease (ChD), and the medications available confer multiple side effects. Mycobacterium bovis Bacillus Calmette-Guérin (BCG) produces balanced Th1, Th2, and Th17 modulatory immune responses and has improved efficacy in controlling chronic infections through nonspecific immunity. We aimed to improve the response to infection by inducing a stronger immune response and greater protection against the parasite by trained immunity.

Methods

BALB/c mice were immunized with BCG subcutaneously, and 60 days later, they were infected with Trypanosoma cruzi intraperitoneally. An evaluation of the progression of the disease from the acute to the chronic stage, analyzing various aspects such as parasitemia, survival, clinical status, and humoral and cellular immune response, as well as the appearance of visceral megas and the histopathological description of target organs, was performed.

Results

Vaccination reduced parasitemia by 70%, and 100% survival was achieved in the acute stage; although the presentation of clinical signs was reduced, there was no increase in the antibody titer or in the differential production of the isotypes.

Conclusion

Serum cytokine production indicated a proinflammatory response in infected animals, while in those who received BCG, the response was balanced by inducing Th1/Th2-type cytokines, with a better prognosis of the disease in the chronic stage.

Pro-inflammatory cytokines are modified during the multiplication of Trypanosoma cruzi within the placental chorionic villi and are associated with the level of infection via the signaling pathway NF-κB

PROBLEM

Congenital Trypanosoma cruzi (T. cruzi) infection has been associated with changes in the levels of TNF-α and IFN-γ during the pregnancy. Therefore, we propose to study the participation and dynamics of proinflammatory cytokines in the infection process of placental explants infected by T. cruzi in vitro.

METHOD OF STUDY

Chorionic villous explants (CVE) obtained of human term placentas (n = 8) from normal pregnancies were cultured with 105 trypomastigotes/mL of Tulahuen strain DTU VI for 0, 2, 4, 16, 24, 48 and 72 h. Explants were treated with sulfasalazine (SULF) (5 mM) and N-acetyl-cysteine (NAC) (15 mM), as inhibitors molecules of NF-κB pathway, or LPS (1 μg/mL) for 24 and 72 h p.i. Motile trypomastigotes were counted in culture supernatants. Immunohistochemistry and ELISA for TNF-α, IFN-γ, IL-1β, IL-4, and IL-10 were performed in CVE and culture supernatants respectively. The parasite load was measured by RT-qPCR.

RESULTS

T. cruzi invades the chorionic villi from 4 h p.i. increasing significantly its DNA at 48 and 72 h p.i. of culture (parasite multiplication phase). They were detected in stromal cells, which was related to elevation of TNF-α, IL-1β, IFN-γ, and IL-10. The inhibition of NF-κB activity in the explants decreased the production of the analyzed cytokines, showing elevated levels of T. cruzi DNA during the multiplication phase of the parasite.

CONCLUSIONS

Placental tissue modifies the secretion of pro-inflammatory cytokines during the phase of parasite multiplication, but not during the invasion phase, which in turns modifies the level of infection via the signaling pathway NF-κB.

Signs of Urban Evolution? Morpho-Functional Traits Co-variation Along a Nature-Urban Gradient in a Chagas Disease Vector

Environmental change (i.e., urbanization) impacts species in contrasting ways, with some species experiencing benefits given their way of life (i.e., blood-sucking insects). How these species respond to such change is not well understood and for species involved in human diseases, this “how” question is particularly important. Most Triatominae bug species inhabit tropical and subtropical forests where their vertebrate hosts’ temporal abundance depends on climate seasonality. However, in human encroached landscapes, triatomines can benefit from resource stability which may lead to adaptive phenotypic change to track novel hosts. We tested for an association between different landscapes and morpho-functional traits linked to sensory, motion, and feeding functions in Triatoma dimidiata and compared fecundity (i.e., number of eggs) in each landscape as a proxy of fitness. Using geometric and traditional morphometric tools, we predicted a morphological simplification in bugs inhabiting urbanized areas. While wing morphology or proboscis were not influenced by landscape class, the opposite occurred for thorax morphology and number of sensilla. Wing and thorax morphology did not covary under modified landscape scenarios, yet we detected a morpho-functional convergence for thorax size and antennal phenotype in both sexes, with a simplification trend, from nature to urban settings. Given no fecundity differences across landscapes, there is no potential reproductive costs. Moreover, the convergence of thorax size and antennal phenotype suggests differences in flight/locomotion performance and host/environment perception, as a possible adaptive response to relaxed selective pressures of the bug’s native habitat. These results imply that T. dimidiata could be adapting to urbanized areas.

Mini-exon gene reveals circulation of TcI Trypanosoma cruzi (Chagas, 1909) (Kinetoplastida, Trypanosomatidae) in bats and small mammals in an ecological reserve in southeastern Mexico

A wide variety of mammals are involved in the sylvatic cycle of Trypanosomacruzi, the causative agent of Chagas disease. In many areas in Latin America where T.cruzi is endemic, this cycle is poorly known, and its main reservoirs have not been identified. In this study we analyzed T.cruzi infection in bats and other small mammals from an Ecological Reserve in southeastern Mexico. From January through March 2021, we captured wild individuals to extract cardiac and peripheral blood, and infection was detected by PCR of the mini-exon gene. In bats, the prevalence of infection was 16.36%, while in small mammals the prevalence was 28.57%. All of the samples that were positive for T.cruzi were identified as the TCI genotype. Our findings suggest that this zone, situated at the periphery of urban zones might have epidemiological relevance in the sylvatic cycle of T.cruzi and needs to be monitored. The infection of bats in this area is particularly concerning since the flight pattern of this populations overlaps with human settlements. Despite being subject to conservation protections, there continue to be anthropogenic actions that disturb the study area, which could exacerbate risks to public health.

Natural infection with Trypanosoma cruzi in bats captured in Campeche and Yucatán, México

INTRODUCTION

Bats have been reported as hosts of the Trypanosoma cruzi protozoan, the etiologic agent of American trypanosomiasis, an endemic zoonotic disease in México.

OBJECTIVE

To describe T. cruzi infection in bats from the states of Campeche and Yucatán, México.

MATERIALS AND METHODS

Captures were made from March to November, 2017, at three sites in Yucatán and one in Campeche. Up to four mist nets on two consecutive nights were used for the capture. The bats' species were identified and euthanasia was performed to collect kidney and heart samples for total DNA extraction. Trypanosoma cruzi infection was detected by conventional PCR with the amplification of a fragment belonging to the T. cruzi DNA nuclear.

RESULTS

Eighty-six bats belonging to five families (Vespertilionidae, Noctilionidae, Mormoopidae, Phyllostomidae, and Molossidae) and 13 species (Rhogeessa aeneus, Noctilio leporinus, Pteronotus davyi, P. parnellii, Artibeus jamaicensis, A. lituratus, A. phaeotis, Glossophaga soricina, Carollia sowelli, Chiroderma villosum, Uroderma bilobatum, Sturnira parvidens, and Molossus rufus) were captured. Infection frequency by PCR was 30,2% (26/86) detected only in the renal tissue. The infected species were P. parnellii, G. soricina, A. lituratus, A. jamaicensis, S. parvidens, C. villosum, and R. aeneus.

CONCLUSIONS

Our results confirmed the participation of several bat species as hosts in the T. cruzi transmission cycle in the region. Further studies are necessary to establish the importance of these animals in the zoonotic transmission of T. cruzi.