Jenny Miu

Chemokine Gene Expression during Fatal Murine Cerebral Malaria and Protection Due to CXCR3 Deficiency

Cerebral malaria (CM) can be a fatal manifestation of Plasmodium falciparum infection. Using murine models of malaria, we found much greater up-regulation of a number of chemokine mRNAs, including those for CXCR3 and its ligands, in the brain during fatal murine CM (FMCM) than in a model of non-CM. Expression of CXCL9 and CXCL10 RNA was localized predominantly to the cerebral microvessels and in adjacent glial cells, while expression of CCL5 was restricted mainly to infiltrating lymphocytes. The majority of mice deficient in CXCR3 were found to be protected from FMCM, and this protection was associated with a reduction in the number of CD8+ T cells in brain vessels as well as reduced expression of perforin and FasL mRNA. Adoptive transfer of CD8+ cells from C57BL/6 mice with FMCM abrogated this protection in CXCR3−/− mice. Moreover, there were decreased mRNA levels for the proinflammatory cytokines IFN-γ and lymphotoxin-α in the brains of mice protected from FMCM. These data suggest a role for CXCR3 in the pathogenesis of FMCM through the recruitment and activation of pathogenic CD8+ T cells.

Caspase-12 Dampens the Immune Response to Malaria Independently of the Inflammasome by Targeting NF-κB Signaling

Pathogen sensing by the inflammasome activates inflammatory caspases that mediate inflammation and cell death. Caspase-12 antagonizes the inflammasome and NF-κB and is associated with susceptibility to bacterial sepsis. A single-nucleotide polymorphism (T125C) in human Casp12 restricts its expression to Africa, Southeast Asia, and South America. Here, we investigated the role of caspase-12 in the control of parasite replication and pathogenesis in malaria and report that caspase-12 dampened parasite clearance in blood-stage malaria and modulated susceptibility to cerebral malaria. This response was independent of the caspase-1 inflammasome, as casp1−/− mice were indistinguishable from wild-type animals in response to malaria, but dependent on enhanced NF-κB activation. Mechanistically, caspase-12 competed with NEMO for association with IκB kinase-α/β, effectively preventing the formation of the IκB kinase complex and inhibiting downstream transcriptional activation by NF-κB. Systemic inhibition of NF-κB or Ab neutralization of IFN-γ reversed the increased resistance of casp12−/− mice to blood-stage malaria infection.

Predominance of Interferon-Related Responses in the Brain during Murine Malaria, as Identified by Microarray Analysis

ABSTRACT Cerebral malaria (CM) can be a fatal manifestation of Plasmodium falciparum infection. We examined global gene expression patterns during fatal murine CM (FMCM) and noncerebral malaria (NCM) by microarray analysis. There was differential expression of a number of genes, including some not yet characterized in the pathogenesis of FMCM. Some gene induction was observed during Plasmodium berghei infection regardless of the development of CM, and there was a predominance of genes linked to interferon responses, even in NCM. However, upon real-time PCR validation and quantitation, these genes were much more highly expressed in FMCM than in NCM. The observed changes included genes belonging to pathways such as interferon signaling, major histocompatibility complex processing and presentation, apoptosis, and immunomodulatory and antimicrobial processes. We further characterized differentially expressed genes by examining the cellular source of their expression as well as their temporal expression patterns during the course of malaria infection. These data identify a number of novel genes that represent interesting candidates for further investigation in FMCM.

Effect of indoleamine dioxygenase-1 deficiency and kynurenine pathway inhibition on murine cerebral malaria

Cerebral malaria (CM) can be a fatal manifestation of Plasmodium falciparum infection. In this study, two different approaches were used to examine the role of indoleamine 2,3-dioxygenase-1 (IDO-1) and its metabolites in the development of murine CM. Mice genetically deficient in IDO-1 were not protected against CM, but partial protection was observed in C57BL/6 mice treated with Ro 61-8048, an inhibitor of kynurenine-3-hydroxylase. This protection was associated with suppressed levels of picolinic acid (PA) within the brain, but not with changes in the levels of kynurenic acid (KA) or quinolinic acid (QA). These data suggest that although IDO-1 is not directly involved in the pathogenesis of CM in C57BL/6 mice, the production of the kynurenine pathway metabolite PA may contribute to the development of murine CM.

Factors associated with cognitive function in older adults in Mexico

Background As populations age, cognitive decline and dementia pose significant burdens for societies and health care systems, including low- and middle-income countries such as Mexico. Minor age-related declines in cognitive function appear to represent a stable but heterogeneous phase in the continuum between normal cognitive ageing and dementia. Loss of cognitive function has impacts at societal and individual levels and understanding the risk factors can help provide a framework for health policies and interventions to target at-risk groups. Design A cohort of older Mexican adults (50+) from the World Health Organizations Study on global AGEing and adult health (WHO SAGE) was used to examine cognitive function, including a total of 2315 respondents, with 325 respondents aged 80 years and older. Cognition was objectively evaluated using verbal recall, verbal fluency, forward digit span and backward digit span, with differences in an overall cognitive score assessed against sociodemographic variables, and associated factors using linear regression. Results The most significant predictors of poorer cognitive function were found to be older age (β=−13.88), rural living (β=−2.25), low income (β=−8.28), self-reported severe or extreme memory difficulties (β=−6.62), and difficulty with two or more activities of daily living (β=−2.02). Conclusions These findings can inform public health initiatives to address cognitive impairment in ageing populations in Mexico and other middle-income countries.