CD8+ T Cells and IFN-γ Mediate the Time-Dependent Accumulation of Infected Red Blood Cells in Deep Organs during Experimental Cerebral Malaria

Background: Infection with Plasmodium berghei ANKA (PbA) in susceptible mice induces a syndrome called experimental cerebral malaria (ECM) with severe pathologies occurring in various mouse organs. Immune mediators such as T cells or cytokines have been implicated in the pathogenesis of ECM. Red blood cells infected with PbA parasites have been shown to accumulate in the brain and other tissues during infection. This accumulation is thought to be involved in PbA–induced pathologies, which mechanisms are poorly understood. Methods and Findings: Using transgenic PbA parasites expressing the luciferase protein, we have assessed by real-time in vivo imaging the dynamic and temporal contribution of different immune factors in infected red blood cell (IRBC) accumulation and distribution in different organs during PbA infection. Using deficient mice or depleting antibodies, we observed that CD8 + T cells and IFN-c drive the rapid increase in total parasite biomass and accumulation of IRBC in the brain and in different organs 6–12 days post-infection, at a time when mice develop ECM. Other cells types like CD4 + T cells, monocytes or neutrophils or cytokines such as IL-12 and TNF-a did not influence the early increase of total parasite biomass and IRBC accumulation in different organs. Conclusions: CD8 + T cells and IFN-c are the major immune mediators controlling the time-dependent accumulation of P. berghei-infected red blood cells in tissues

Identification and characterisation of novel human dendritic cell progenitors

Dendritic cells (DCs) are professional antigen presenting cells that initiate the immune response. They are heterogeneous and are broadly classified into three groups – two major subsets of conventional DCs (cDC) named cDC1 and cDC2, and plasmacytoid DC (pDC). Each subset has unique transcription factor dependency, and specialised functions. DCs are derived from a unique lineage of DC-restricted progenitors that are until now not yet fully characterised. Currently, there are limited genetic lineage fate mapping mice models available to track the development of DCs in steady state and inflammation. We have identified Uroplakin-1b (Upk1b) as uniquely expressed in DC-restricted progenitors. Surprisingly, this molecule is also expressed in microglia. We developed a fate mapping Upk1b-cre mouse, which was crossed to Rosa-YFP reporter mouse to generate Upk1b-cre:Rosa YFP. Contrary to our expectations, we observed low recombination in DC-restricted progenitors and DC subsets. However, the recombination level in the microglia was close to 80% in young adults, suggesting that it may be a useful model for microglial research. Upk1b is conserved across species and may serve as a potential marker to identify DC-restricted progenitors in humans. Although human DC-restricted progenitors were recently identified, here, we extended and further refined the definition of the precursor of cDC (pre-cDC). We showed that they share several common phenotypic markers such as CD303, CD123 and CD45RA with pDC, thereby contaminating the pDC fraction of the peripheral blood. Hence, this might explain why pDC when stimulated with IL-3 and CD40 ligand, were found to differentiate into cells with cDC-like morphology. We also demonstrated that pre-cDC but not pDC were able to differentiate into cDC subsets in MS5 stromal culture supplemented with the cytokines Flt3L, SCF and GM-CSF. We further interrogated the bulk pre-cDC population in peripheral blood and identified three populations of pre-cDC, namely early, uncommitted pre-cDC and committed pre-cDC1 and pre-cDC2. Early, uncommitted pre-cDC differentiated into both cDC subsets, while committed pre-cDC1 and pre-cDC2 differentiated into their respective cDC subsets. We also observed that they are responsive to Flt3L stimulation and were able to induce allogeneic naïve T cell proliferation in the absence of stimulation. Finally, we observed that pre-cDC was expanded in the blood of Systemic Lupus Erythematosus (SLE) patients, and are currently investigating the role of pre-cDC in this autoimmune disease.DOCTOR OF PHILOSOPHY (SBS

Cohort profile : Singapore Preconception Study of Long-Term Maternal and Child Outcomes (S-PRESTO)

The Singapore Preconception Study of Long-Term Maternal and Child Outcomes (S-PRESTO) is a preconception, longitudinal cohort study that aims to study the effects of nutrition, lifestyle, and maternal mood prior to and during pregnancy on the epigenome of the offspring and clinically important outcomes including duration of gestation, fetal growth, metabolic and neural phenotypes in the offspring. Between February 2015 and October 2017, the S-PRESTO study recruited 1039 Chinese, Malay or Indian (or any combinations thereof) women aged 18–45 years and who intended to get pregnant and deliver in Singapore, resulting in 1032 unique participants and 373 children born in the cohort. The participants were followed up for 3 visits during the preconception phase and censored at 12 months of follow up if pregnancy was not achieved (N = 557 censored). Women who successfully conceived (N = 475) were characterised at gestational weeks 6–8, 11–13, 18–21, 24–26, 27–28 and 34–36. Follow up of their index offspring (N = 373 singletons) is on-going at birth, 1, 3 and 6 weeks, 3, 6, 12, 18, 24 and 36 months and beyond. Women are also being followed up post-delivery. Data is collected via interviewer-administered questionnaires, metabolic imaging (magnetic resonance imaging), standardized anthropometric measurements and collection of diverse specimens, i.e. blood, urine, buccal smear, stool, skin tapes, epithelial swabs at numerous timepoints. S-PRESTO has extensive repeated data collected which include genetic and epigenetic sampling from preconception which is unique in mother–offspring epidemiological cohorts. This enables prospective assessment of a wide array of potential determinants of future health outcomes in women from preconception to post-delivery and in their offspring across the earliest development from embryonic stages into early childhood. In addition, the S-PRESTO study draws from the three major Asian ethnic groups that represent 50% of the global population, increasing the relevance of its findings to global efforts to address non-communicable diseases

The methyltransferase Ezh2 controls cell adhesion and migration through direct methylation of the extranuclear regulatory protein talin

A cytosolic role for the histone methyltransferase Ezh2 in regulating lymphocyte activation has been suggested, but the molecular mechanisms underpinning this extranuclear function have remained unclear. Here we found that Ezh2 regulated the integrin signaling and adhesion dynamics of neutrophils and dendritic cells (DCs). Ezh2 deficiency impaired the integrin-dependent transendothelial migration of innate leukocytes and restricted disease progression in an animal model of multiple sclerosis. Direct methylation of talin, a key regulatory molecule in cell migration, by Ezh2 disrupted the binding of talin to F-actin and thereby promoted the turnover of adhesion structures. This regulatory effect was abolished by targeted disruption of the interactions of Ezh2 with the cytoskeletal-reorganization effector Vav1. Our studies reveal an unforeseen extranuclear function for Ezh2 in regulating adhesion dynamics, with implications for leukocyte migration, immune responses and potentially pathogenic processes.NMRC (Natl Medical Research Council, S’pore)MOE (Min. of Education, S’pore)ASTAR (Agency for Sci., Tech. and Research, S’pore)Accepted versio