Parasite load, iNOS and cytokine profiles, and histopathological aspects of Leishmania infantum infection in dogs with different clinical presentations

Tassia Cristina Bello De Vasconcelos,Vinícius Silva Belo,Sávio Freire Bruno,Fátima Conceição-Silva,Fabiano Borges Figueiredo,Luisa Helena Monteiro De Miranda

doi:10.1590/0103-8478cr20180984

Tassia Cristina Bello De Vasconcelos, Vinícius Silva Belo + Show 4 more

Open Access

https://doi.org/10.1590/0103-8478cr20180984

Copy DOI

Abstract

ABSTRACT: Visceral leishmaniasis (VL) is a zoonotic disease with a canine urban reservoir in South America. Dogs from an endemic area within Brazil, which were naturally infected with Leishmania infantum, and those presenting severe clinical (SC), mild, or no clinical (MNC) disease, were evaluated. Parasite load, histopathology, and cytokine and iNOS mRNA expressions were assessed in the spleen and liver in order to determine the potential markers for disease susceptibility or resistance. As a result, dogs with both SC and MNC had high parasite loads; IFN-γ was the most expressive cytokine in both organs, along with IL-6 and IL-4 being detected in the spleen and liver, and IL-10 only in liver. The hepatic tissue presented higher medians for IFN-γ and IL-10, and was the main organ to produce cytokines with hepatic IL-10 suggesting a regulatory follow up. Granulomas were detected in both organs; however, when absent in spleen, they were associated with elevated IL-6 levels, thus highlighting the anti-inflammatory role of IL-6. Microscopic lesions in the spleen were predominantly characterized by an extensively disorganized white pulp and splenic response was suggested as sub optimized. Parasite load, tissue damage, and immunological response may vary in the dogs with similar clinical symptoms, which may not be a good parameter for assessing the animal’s susceptibility to VL.

Highlights

Visceral leishmaniasis (VL) is the most severe form of all leishmaniasis types (Sundar & RAI, 2002)
Study design This is a cross-sectional study conducted with a convenience sample of 24 mongrel dogs from a Brazilian endemic area to assess the presence of canine visceral leishmaniasis (CVL) in the municipality of Barra Mansa, Southeastern Brazil
Moreira et al (2016), verified greater parasite density in the spleen in comparison with liver, our results revealed no significant difference, indicating a positive correlation between these organs and their parasite loads; a comprehensive study including the assessment of immunological markers in other target tissues and in the peripheral blood, as well as the investigation of overlapping diseases, is necessary to improve the understanding on the overall immune response in these animals

Summary

Introduction

Visceral leishmaniasis (VL) is the most severe form of all leishmaniasis types (Sundar & RAI, 2002). In South America, the disease has spread to the medium-sized and large urban areas revealing occurrence of zoonosis (Werneck, 2014), with Leishmania infantum (syn = Leishmania chagasi) as the main etiological agent involved (DantaSTorres, 2009). In this case, the dog (Canis familiaris) is the main urban source of infection for the vector and transmission occurs via the bite of infected phlebotomine sand flies (werneck, 2014). The spleen and liver play a pivotal role in VL, being evident sites of interaction between the immune system and the Leishmania parasite (MAIA & CAMPINO, 2012; srivastava et al, 2016). Several cells such as Kupffer (loeuillet et al, 2016; melo et al, 2009; moreira et al, 2016; rodrigues et al, 2016; sant’ana et al, 2007), T lymphocyte, and dendritic cells present interesting interactions (loeuillet et al, 2016; rodrigues et al, 2016)

Methods

Results

Discussion

Conclusion