Frequency of co-seropositivities for certain pathogens and their relationship with clinical and histopathological changes and parasite load in dogs infected with Leishmania infantum

Correction: Frequency of co-seropositivities for certain pathogens and their relationship with clinical and histopathological changes and parasite load in dogs infected with Leishmania infantum

[This corrects the article DOI: 10.1371/journal.pone.0247560.].

A non-replicative antibiotic resistance-free DNA vaccine delivered by the intranasal route protects against canine leishmaniasis

Leishmania infantum is the etiological agent of zoonotic visceral leishmaniasis (ZVL). The disease is endemic in Central and South America, Central and South East Asia, and the Mediterranean basin. Dogs are the main reservoir, with an estimated prevalence of approximately 2.5 million dogs in Southern Europe. Current treatments cause side effects, disease recurrence, and drug resistance. Therefore, the development of vaccines against canine leishmaniasis is necessary. We have generated a DNA vaccine based on the non-replicative antibiotic resistance marker-free plasmid vector pPAL that contains the encoding gene for the L. infantum activated protein kinase C receptor analog (LACK). Homologous pPAL-LACK prime-boost intranasal administration confers efficacious protection in Beagle dogs with a reduction of clinical signs and a statistically significant reduction of the parasite burden in the bone marrow of more than 90% of dogs after experimental infection with highly infective promastigotes. This DNA vaccine elicits a robust cellular immune response skewed towards the Th1 profile.

Modulation of Macrophage Redox and Apoptotic Processes to Leishmania infantum during Coinfection with the Tick-Borne Bacteria Borrelia burgdorferi

Canine leishmaniosis (CanL) is a zoonotic disease caused by protozoan Leishmania infantum. Dogs with CanL are often coinfected with tick-borne bacterial pathogens, including Borrelia burgdorferi in the United States. These coinfections have been causally associated with hastened disease progression and mortality. However, the specific cellular mechanisms of how coinfections affect microbicidal responses against L. infantum are unknown. We hypothesized that B. burgdorferi coinfection impacts host macrophage effector functions, prompting L. infantum intracellular survival. In vitro experiments demonstrated that exposure to B. burgdorferi spirochetes significantly increased L. infantum parasite burden and pro-inflammatory responses in DH82 canine macrophage cells. Induction of cell death and generation of mitochondrial ROS were significantly decreased in coinfected DH82 cells compared to uninfected and L. infantum-infected cells. Ex vivo stimulation of PBMCs from L. infantum-seronegative and -seropositive subclinical dogs with spirochetes and/or total Leishmania antigens promoted limited induction of IFNγ. Coexposure significantly induced expression of pro-inflammatory cytokines and chemokines associated with Th17 differentiation and neutrophilic and monocytic recruitment in PBMCs from L. infantum-seropositive dogs. Excessive pro-inflammatory responses have previously been shown to cause CanL pathology. This work supports effective tick prevention and risk management of coinfections as critical strategies to prevent and control L. infantum progression in dogs.

Comparison between Colorimetric In Situ Hybridization, Histopathology, and Immunohistochemistry for the Diagnosis of New World Cutaneous Leishmaniasis in Human Skin Samples

New world cutaneous leishmaniasis (NWCL) is an anthropozoonosis caused by different species of the protozoan Leishmania. Colorimetric in situ hybridization (CISH) was shown to satisfactorily detect amastigote forms of Leishmania spp. in animal tissues, yet it was not tested for the diagnosis of human NWCL. The aim of this study was to compare CISH, histopathology (HP), and immunohistochemistry (IHC) techniques to diagnose NWCL in human cutaneous lesions. The sample comprised fifty formalin-fixed, paraffin-embedded skin biopsy specimens from patients with NWCL caused by L. (V.) braziliensis. These specimens were analyzed by CISH, using a generic probe for Leishmania, IHC, and HP to assess the sensitivity of these methods by using a parasitological culture as a standard reference. Additional specimens from three patients diagnosed with cutaneous mycoses were also included to evaluate cross-reactions between CISH and IHC. The sensitivities of IHC, CISH, and HP for detecting amastigotes was 66%, 54%, and 50%, respectively. IHC, unlike CISH, cross-reacted with different species of fungi. Together, these results demonstrate that CISH may be a complementary assay for the detection of amastigote in the laboratorial diagnosis routine of human NWCL caused by L. (V.) braziliensis.

Atypical Lesions in Canine Leishmaniosis: Description of New Cases

Simple Summary

Canine leishmaniosis is a zoonotic disease caused mainly by the protozoan Leishmania infantum that is endemic in the Mediterranean basin. The clinical signs and pathological characteristics have been extensively described; however, atypical lesions leading to clinical and pathological misdiagnosis have been sporadically reported. This study presents three cases of dogs experimentally infected with Leishmania infantum that showed gross lesions considered atypical of canine leishmaniosis and not previously reported. Macroscopic lesions were observed in the liver, spleen, and peritoneal cavity that corresponded to tan to whitish nodular lesions in all organs and multifocal irregular and linear whitish lesions in one of the livers that mimicked tumors. Microscopically, a marked granulomatous inflammation with a relative scarcity of parasites was observed in all the organs. In conclusion, microscopic and parasitological studies should be performed on atypical lesions observed in Leishmania-infected and non-infected dogs, especially in endemic regions. In addition, due to its zoonotic importance, leishmaniosis should be considered when atypical nodular lesions are observed in dogs from non-endemic regions with a history of travel to endemic regions.

Abstract

Pathological characteristics are well described in canine leishmaniosis (CanL). However, atypical lesions that can be confused with other pathologies or trigger unusual clinical signs are sporadically reported. Atypical lesions were observed during routine postmortem examination in three Leishmania-infected dogs and samples were taken for histopathological and immunohistochemical studies. Clinical signs, biochemical parameters, level of antibodies, and parasite detection by PCR were also evaluated. Atypical lesions were found in the peritoneal cavity, liver, and spleen. Splenomegalia and hepatomegalia were observed in all dogs. In addition, multifocal dark to white nodules of variable size were observed in the peritoneal cavity, liver, and spleen of one dog and in the spleen of the other two dogs. One dog presented diffuse irregular whitish lines with a threadlike appearance and another an intense fibrotic depression in the intermediate lobe. Microscopically, an intense granulomatous inflammation with abundant macrophages, a variable number of lymphocytes, and a low to moderate number of parasites was observed. This study represents the first description of granulomatous peritonitis associated with Leishmania in dogs. It also shows atypical macroscopic expression of hepatitis in CanL. In the absence of an adequate clinical history and laboratory analyses, certain lesions observed in CanL could admit alternative diagnoses.

Epidemiologic, Clinical and Immunological Consequences of Co-Infections during Canine Leishmaniosis

Simple Summary

Canine leishmaniosis (CanL), the most severe, visceralizing form of disease caused by Leishmania infantum transmitted by phlebotomine sand flies. CanL is frequently diagnosed in the Mediterranean basin and South America, although it is also found in other regions, including the United States (U.S.). Dogs in these regions are at risk for co-infections, prominently tick-borne diseases. Our review examines epidemiologic, clinical, and immunologic mechanisms found during the most common eight CanL co-infections reported in published literature. Co-infections alter immunologic processes and disease progression impacting CanL diagnosis, therapeutic responses, and prognosis.

Abstract

Canine leishmaniosis (CanL) is a vector-borne, parasitic disease. CanL is endemic in the Mediterranean basin and South America but also found in Northern Africa, Asia, and the U.S. Regions with both competent sand fly vectors and L. infantum parasites are also endemic for additional infectious diseases that could cause co-infections in dogs. Growing evidence indicates that co-infections can impact immunologic responses and thus the clinical course of both CanL and the comorbid disease(s). The aim for this review is to summarize epidemiologic, clinical, and immunologic factors contributing to eight primary co-infections reported with CanL: Ehrlichia spp., Anaplasma spp., Borrelia spp., Babesia spp., Trypanosoma cruzi, Toxoplasma gondii, Dirofilaria immitis, Paracoccidioides braziliensis. Co-infection causes mechanistic differences in immunity which can alter diagnostics, therapeutic management, and prognosis of dogs with CanL. More research is needed to further explore immunomodulation during CanL co-infection(s) and their clinical impact.