Caracterização de eventos imunopatológicos em sistema nervoso central de caprinos naturalmente infectados por Neospora caninum

Abstract

In this study, we have evaluated the microscopic lesions and cellular immune responses in the central nervous system of seven goat fetuses from abortions by N. caninum and six male, young and adult goats, naturally infected. As a negative control, three fetuses and one adult goat were used. For this purpose immunohistochemical staining with anti CD3, CD79α, GFAP, MHC- II antibodies was performed, RCA1 Lectinhistochemistry, besides the nuclear marker of proliferating cell antigen (PCNA). Lesions found in fetuses consisted of multifocal areas of necrosis surrounded by glial cells and perivascular cuffs that focused mainly in regions of cerebral cortex, thalamus and brainstem. These lesions were either, or not, related to the presence of parasitic structures. In the central nervous system of young and adult male goats, similar lesions were found in four of the six goats positive for N. caninum, although these animals did not manifest any clinical signs. In three adult goats there was also a few multinucleated giant cells associated. The presence of the parasite was assessed by analysis of histopathology, immunohistochemistry and the polymerase chain reaction (PCR) evidencing the infection in seven of 10 fetuses and six of seven adult goats. The immunohistochemical staining of cells in areas of gliosis allowed us to characterize them as astrogliosis and microgliosis in Neospora caninum infections in fetuses and adults; there is a bias towards the response of monocytic lineage cells (macrophages and microglia) with lower participation of astrocytes. In fetuses, astrocytes were present in lesions near the white matter, and adult astrocytic lesions were present in the gray matter of three goats representing glial scars. In addition, there was the expression of MHC-II in endothelium and microglia, especially in adult goats and probably stimulated by the presence of the parasite in the tissue. With this study, we describe the presence of cysts of N. caninum in adult male goats, which has not been demonstrated to date in adult animals of any species and we characterized the cell types involved in the immune response in the CNS of these animals.