T lymphocyte immunophenotypes in the cerebrospinal fluid of dogs with visceral leishmaniasis

Abstract

Visceral leishmaniasis (VL) is a disease causing several clinical manifestations in dogs, including neurological disorders. Nevertheless, there are few studies related to the evaluation of the brain alterations during VL. Evidences of the involvement of cerebral barriers in infected dogs was reported, including the presence of brain inflammatory infiltrate, with a predominance of CD3+ T cells. Therefore, the aim of this study was to determine the immunophenotypes of T lymphocytes in the cerebrospinal fluid (CSF), as well as in peripheral blood, and to correlate with brain alterations in dogs with VL. We detected elevated percentages of double negative (DN) and double positive (DP) T cells in the CSF, with a predominance of TCRαb. In the histopathological analysis, we observed a predominance of lymphoplasmacytic infiltrate, mainly in leptomeninges, ranging from mild to intense, and we observed a positive correlation between the intensity of inflammation in the subependymal area and the DN T cells of the CSF. Thus, the DN T cells seem be acting as villains of the immune system through pro-inflammatory mechanisms. Further, the proportion of the different population of CSF T cells did not differ from those observed in the blood, which provides us with more evidence of blood-CSF barrier breakdown. Together, the results provide more explanation to the inflammation observed in the brain of dogs with VL, which the DN T cells contribute to the origin and progression of the neurological disease. This study provides insight into the immunophenotypes of T lymphocytes in the CSF during canine visceral leishmaniasis.

Toll-like receptors and cytokines in the brain and in spleen of dogs with visceral leishmaniosis

“…Similarly, to previous reports, brain inflammation ranged from mild to intense in the present study (Viñuelas et al, 2001;Márquez et al, 2013;Melo et al, 2013;Grano et al, 2016;Gianuzzi et al, 2017;Oliveira et al, 2017). The presence of lymphocytes and plasma cells observed in the brains from the infected dogs in our study is probably related to blood-brain barrier breakdown (BBB), described previously during canine VL (Melo et al, 2015b), which could allow the entrance of cells and inflammatory mediators to the cerebral parenchyma, contributing to brain inflammation.…”

“…Whole parasites were not detected in the histopathological analysis of the brain, but we detected its DNA. The same was previously verified by our group in other dogs with VL (Melo et al, 2015a;Grano et al, 2016). Perhaps this can be occurring due to the use of a staining technique of low sensitivity.…”

“…One possible mechanism would be the presence of peripheral inflammatory mediators and cells stimulating the CNS. Evidence of blood-cerebrospinal fluid barrier breakdown has been reported during canine VL, in which T lymphocytes from the blood would somehow stimulate the development of brain inflammation (Grano et al, 2016). Another type of peripheral stimulation in the CNS could be through exosomes.…”

“…The brain inflammation was evaluated according to the intensity of the inflammatory infiltrate through the use of a ponderal index divided into four grades (grade 0-3), in accordance with Grano et al (2016): Grade 0 (no inflammation observed); Grade 1, mild inflammation (slight inflammatory cell infiltrate mainly in the choroid plexuses and leptomeninges); Grade 2, moderate inflammation (moderate inflammatory cell infiltrate mainly in the choroid plexuses, and leptomeninges, along with the presence of some perivascular lymphocytes in the brain tissue); and Grade 3, severe inflammation (remarkable inflammatory cell infiltrate mainly in the choroid plexuses and leptomeninges along with intense perivascular infiltration in the brain tissue).…”

“…Neurological clinical signs include walking in circles, seizures, paresis, tetraplegia, head tilt, motor incoordination, intention tremor, nystagmus, strabismus and myoclonia (Font et al, 2004;Ikeda et al, 2007;José-lópez et al, 2012;Márquez et al, 2013;Gianuzzi et al, 2017). In addition to neurological clinical signs, brain inflammation has also been reported in dogs with VL, where meningitis and choroiditis are the usual histopathological findings (Nieto et al, 1996;Viñuelas et al, 2001;Melo et al, 2009Melo et al, , 2013Melo et al, , 2015aGrano et al, 2016;Gianuzzi et al, 2017). Considering these findings, the focus of our research group in recent years has been to investigate the question about why infected dogs present neurological clinical signs and brain inflammation.…”