N’Songo, Aurelie

Abstract The most severe clinical complication of Plasmodium falciparum infection is cerebral malaria (CM). Plasmodium berghei ANKA (PbA) infection of C57BL/6 mice is an established model of CM. Previous work has implied a role for CD8 T cells and perforin expression in fatal stages of PbA infection. We therefore infected C57BL/6 and C57BL/6 Perforin-/- mice with PbA and assessed the CNS for cerebral endothelial cell blood-brain barrier (BBB) disruption using FITC albumin leakage into tissue, confocal microscopy and 3D volumetric T2 and T1 gadolinium enhanced MRI. PbA infected C57BL/6 mice: 1.) had extensive disruption of BBB tight junction proteins Occludin and Claudin 5, 2.) developed severe CNS vascular permeability of FITC albumin and gadolinium leakage, and 3.) became moribund. We also observed increased VEGF cytokine expression coinciding with CNS vascular permeability in these animals. Despite having similar CD8 T cell infiltration into the brain, PbA infected C57BL/6 Perforin-/- mice had intact BBB tight junction, were devoid of CNS vascular permeability, presented with normal brain MRI, and had normal behavioral scores on the rotarod assay. This study is therefore the first to demonstrate the critical importance of perforin expression in promoting BBB tight junction alteration during PbA infection. Therefore, development of therapies to block factors related perforin mediated delivery could have significant benefit to the treatment of CM.

AbstractIntroductionMAPT H1 haplotype is implicated as a risk factor for neurodegenerative diseases including Alzheimer's disease (AD).MethodsUsing Alzheimer's Disease Genetics Consortium (ADGC) genome‐wide association study (GWAS) data (n = 18,841), we conducted a MAPT H1/H2 haplotype–stratified association to discover MAPT haplotype–specific AD risk loci.ResultsWe identified 11 loci—5 in H2‐non‐carriers and 6 in H2‐carriers—although none of the MAPT haplotype–specific associations achieved genome‐wide significance. The most significant H2 non‐carrier–specific association was with a NECTIN2 intronic (P = 1.33E‐07) variant, and that for H2 carriers was near NKX6‐1 (P = 1.99E‐06). The GABRG2 locus had the strongest epistasis with MAPT H1/H2 variant rs8070723 (P = 3.91E‐06). Eight of the 12 genes at these loci had transcriptome‐wide significant differential expression in AD versus control temporal cortex (q < 0.05). Six genes were members of the brain transcriptional co‐expression network implicated in “synaptic transmission” (P = 9.85E‐59), which is also enriched for neuronal genes (P = 1.0E‐164), including MAPT.DiscussionThis stratified GWAS identified loci that may confer AD risk in a MAPT haplotype–specific manner. This approach may preferentially enrich for neuronal genes implicated in synaptic transmission.

ABSTRACTHuman cerebral malaria (HCM) is a serious complication ofPlasmodium falciparuminfection. The most severe outcomes for patients include coma, permanent neurological deficits, and death. Recently, a large-scale magnetic resonance imaging (MRI) study in humans identified brain swelling as the most prominent predictor of fatal HCM. Therefore, in this study, we sought to define the mechanism controlling brain edema through the use of the murine experimental cerebral malaria (ECM) model. Specifically, we investigated the ability of CD8 T cells to initiate brain edema during ECM. We determined that areas of blood-brain barrier (BBB) permeability colocalized with a reduction of the cerebral endothelial cell tight-junction proteins claudin-5 and occludin. Furthermore, through small-animal MRI, we analyzed edema and vascular leakage. Using gadolinium-enhanced T1-weighted MRI, we determined that vascular permeability is not homogeneous but rather confined to specific regions of the brain. Our findings show that BBB permeability was localized within the brainstem, olfactory bulb, and lateral ventricle. Concurrently with the initiation of vascular permeability, T2-weighted MRI revealed edema and brain swelling. Importantly, ablation of the cytolytic effector molecule perforin fully protected against vascular permeability and edema. Furthermore, perforin production specifically by CD8 T cells was required to cause fatal edema during ECM. We propose that CD8 T cells initiate BBB breakdown through perforin-mediated disruption of tight junctions. In turn, leakage from the vasculature into the parenchyma causes brain swelling and edema. This results in a breakdown of homeostatic maintenance that likely contributes to ECM pathology.

We conducted a comprehensive screening of rare coding variants in an African American cohort to identify novel pathogenic mutations within the early-onset Alzheimer’s disease (EOAD) genes ( APP, PSEN1 , and PSEN2) in this understudied population. Whole-exome sequencing of 238 African American subjects identified 6 rare missense variants within the EOAD genes, which were observed in AD cases but never among controls. These variants were analyzed in an independent cohort of 300 African American subjects in which PSEN2 :NM_000447:exon5:c.T331C:p.Phe111Leu and PSEN1-minilin rs777923890 variants were again not observed, indicating that these novel rare variants, may contribute to AD risk in this population.