NK cells infiltrating in the central nervous system aggravate brain injury of mice caused by Angiostrongylus cantonensis infection

Abstract

Background Angiostrongylus cantonensis (A. cantonensis), is a food-borne zoonotic parasite that can cause central nervous system (CNS) injury characterized by eosinophilic meningitis. However, the pathogenesis of the neurological impairments caused by A. cantonensis infection has not been well elucidated. Natural killer cells (NK cells) are unique innate lymphocytes important in early defense against pathogens. It was reported that NK cells could migrate to the CNS after brain injury. The aim of the present study was to investigate the role of NK cells in brain injury caused by A. cantonensis infection.Methods Mouse model of A. cantonensis infection was established by intragastric administration of third-stage larvae. Neurological impairments were evaluated by Longa’s score, Clark’s general score and Clark’s focal score. Histopathological changes were observed by hematoxylin and eosin staining. The expression of cytokines at gene and protein levels was analyzed by PCR and ELISA, respectively. Infiltration of NK cells in the CNS was detected by immunohistochemistry and flow cytometry. Depletion of NK cells in infected mice was caused by tail vein injection of anti-asialo GM1 rabbit serum, and adoptive transfer of NK cells was performed by tail vein injection of purified splenic NK cells. NK cell-mediated cytotoxicity against YAC-1 cells was detected by LDH release assay. The cytokine production ability was determined by intracellular flow cytometry and ELISA.Results Mice developed brain inflammation and neurological impairment after A. cantonensis infection. The infiltration of NK cells in the CNS of A. cantonensis-infected mice was observed on 14 dpi and reached the peak on 22 dpi. Compared with the normal splenic NK cells, the CNS-infiltrated NK cells of infected mice expressed lower levels of CD69, NKp46 and NKG2D, but higher levels of NKG2A, and showed enhanced cytotoxicity and increased IFN-γ and TNF-α production ability. Depletion of NK cells alleviated brain injury, whereas adoptive transfer of NK cells exacerbated brain damage in A. cantonensis-infected mice.Conclusions Our results demonstrate that NK cells infiltrate into the CNS and aggravate the brain damage after A. cantonensis infection. The findings improve the understanding the pathogenesis of angiostrongyliasis and expand the therapeutic intervention in CNS disease.