Leukocyte entry into the CNS of Leishmania chagasi naturally infected dogs

Abstract

In dogs, there is an association of chronic visceral leishmaniasis with neurological symptoms, and very few publications have investigated whether these neurological manifestations correlate with specific alterations in brain. A total of 42 mixed-breed adult dogs were selected from the Veterinary Hospital of UNESP-Araçatuba and the Control Zoonosis Center in Araçatuba, São Paulo State, Brazil, which is an endemic area for visceral leishmaniasis. Animals presenting positive ELISA and/or positive parasitological diagnosis of Leishmania were enrolled in the group of infected dogs (n=32). Animals with negative ELISA results and parasitological tests for Leishmania, including a negative immunofluorescence test for toxoplasmosis and neosporosis, were included as the control group (n=10). Brain samples were collected, stored in 10% buffered formalin and subjected to routine histological procedures, following by staining with haematoxylin-eosin (HE) and immunohistochemical examination for T and B lymphocytes and phagocytic cells. Cerebrospinal fluid was collected to determine the anti-Leishmania antibody titers. Histological examination of HE stains demonstrated intense inflammatory infiltrate, primarily in the choroid plexus, which was composed of mononuclear cells with no detectable parasites. Immunohistochemistry revealed that CD3(+) T lymphocytes were the major components of the inflammatory infiltrate at the choroid plexus and in the brain. Infected dogs had more CD3(+) T cells than uninfected animals (P=0.0002). Cerebrospinal fluid from infected dogs contained high titers of anti-Leishmania antibodies in comparison with control animals (P<0.0001), which suggests a compromise of the blood-cerebrospinal fluid barrier. Leukocyte entry into the brain suggests the participation of these cells in the pathogenesis of neurological disorders during the advanced stages of leishmaniasis and confirms that the choroid plexus is an important structure for T cell influx.

Occurrence of Leishmania infantum in the central nervous system of naturally infected dogs: Parasite load, viability, co-infections and histological alterations

“…Analysis of the CNS of dogs infected with L . infantum revealed the presence of anti- Leishmania antibodies in cerebrospinal fluid (CSF) [6, 8, 14, 16, 18, 20] and of L . infantum DNA in the brain [13, 20–22] and CSF [11].…”

Neurologic Manifestations ofLeishmania spp.Infection

“…Although the most common CNS finding is infiltration of inflammatory cells during VL infection of dogs [33], there are reports of presence of amastigotes in both choroid plexus [37] and meninges [49] (which was confirmed via immunohistochemistry in experimental infection [48]). It is also reported to be not uncommon to see ocular changes with canine VL [30].…”

“…Reports of neuro-inflammation associated with natural and experimental VL infection [1,33], as well as the presence of Immunoglobulin in aqueous humor and cerebrospinal fluid (CSF) [15] suggest a disruption of the blood-brain barrier (BBB), and the bloodcerebrospinal fluid barrier underlies the CNS manifestation of disease. The BBB functions to exclude microscopic objects and large hydrophilic molecules, and is achieved by endothelial cell specializations including tight junctions between cells, a specialized basal lamina surrounding the vessels in the brain, and an ensheathment of the vessels made of astrocytic endfeet [11].…”

Main lesions in the central nervous system of dogs due to Leishmania infantum infection

“…Other studies, despite the observation of histopathological alterations in the CNS of dogs during visceral leishmaniasis, failed to verify the presence of Leishmania amastigotes [11, 19, 20, 23–25]. Some authors explain these contradictory findings by the chronicity of the disease, arguing that the presence of Leishmania in the CNS has generally been demonstrated in dogs with an earlier infection, either because of delayed diagnosis or by the choice of treatment for the infected dogs, as in two studies in the Mediterranean region [11, 24]. In fact, here we observed that animals that presented amastigote forms in the CNS had clinical signs such as cachexia and the presence of skin lesions, observed in the chronic phase.…”