Cytokines and adhesion molecules expression in the brain in human cerebral malaria

Abstract

Although the role of systemic proinflammatory cytokines, IL-1beta and TNF-alpha, and their up-regulation of adhesion molecules, ICAM-1, VCAM-1 and E-Selectin, in the pathogenesis of cerebral malaria (CM) is well established, the role of local cytokine release remain unclear. Immunohistochemistry (IHC) was used to compare the expression of ICAM-1, VCAM-1, E-Selectin, IL-1beta, TNF-a and TGF-beta at light microscopic level in cerebral, cerebellar and brainstem postmortem cryostat sections from 10 CM, 5 severe malarial anemia (SMA), 1 purulent bacterial meningitis (PBM), 2 non-central nervous system infections (NCNSI) and 3 non-infections (NI) deaths in Ghanaian children. Fatal malaria and Salmonella sepsis showed significantly higher vascular expression of all 3 adhesion molecules, with highly significant co-localization with sequestration in the malaria cases. However, there was negligible difference between CM and SMA. TGF-beta showed intravascular and perivascular distribution in all cases, but expression was most intense in the PBM case and CM group. TNF-alpha and IL-1beta showed prominent brain parenchymal staining, in addition to intravascular and perivascular staining, in only the PBM case and CM group. The maximal expression of all 6 antigens studied was in the cerebellar sections of the malaria cases. Endothelial activation is a feature of fatal malaria and Salmonella sepsis, with adhesion molecule expression being highly correlated with sequestration. IL-1beta and TNF-alpha are upregulated in only cases with neurodegenerative lesions, whilst TGF-beta is present in all cases. Both cytokines and adhesion molecules were maximally upregulated in the cerebellar sections of the malaria cases.

Figure 1A–F

(original magnification, X400): Immunohistology for ICAM-1, VCAM-1 & E-selectin. (A–B) Sections of non-malaria cases: (A) Staining for ICAM-1: positive in < 25% of brain microvessel (average score +/−). (B) Staining for VCAM-1: positive in < 25% of brain microvessels (average score +/−). (C) Section of typhoid perforation and septicaemia case: Staining for ICAM-1: positive in 25 to 50% of microvessels (average score +). (D–F) Sections of malaria cases: (D) Staining for ICAM-1: positive in > 75% of microvessels (average score +++). (E) Staining for ICAM-1: positive in > 75% of microvessels (average score +++). Note the more extreme heterogeneity between sequestration and receptor expression in the SMA case in 1E than the CM case in 1D. (F) Staining for ICAM-1: Positive in > 75% of microvessels (average score +++). Note the more intense staining of the CM cerebellar section in 1F compared to the CM cerebral section in 1D.

Figure 2A–F

(original magnification, X100): Immunohistology for TGFβ, IL-1β & TNFα. (A–B) TGFβ staining (intravascular & perivascular). (A) NCNSI section: moderate in some fields (average score +). (A) CM/PBM section: strong in all fields (average score +++). (C–E) IL-1β staining (intravascular, perivascular & parenchymal). (C) PBM section: moderate in some fields (average score +). (D) CM section: strong in all fields (average score +++). (E) NCNSI section: no staining in all fields (average score −). TNFα staining (intravascular, perivascular & parenchymal). CM/PBM section: strong in all fields (average score +++).