Development of a Novel CD4+ TCR Transgenic Line That Reveals a Dominant Role for CD8+ Dendritic Cells and CD40 Signaling in the Generation of Helper and CTL Responses to Blood-Stage Malaria

Abstract

We describe an MHC class II (I-Ab)–restricted TCR transgenic mouse line that produces CD4+ T cells specific for Plasmodium species. This line, termed PbT-II, was derived from a CD4+ T cell hybridoma generated to blood-stage Plasmodium berghei ANKA (PbA). PbT-II cells responded to all Plasmodium species and stages tested so far, including rodent (PbA, P. berghei NK65, Plasmodium chabaudi AS, and Plasmodium yoelii 17XNL) and human (Plasmodium falciparum) blood-stage parasites as well as irradiated PbA sporozoites. PbT-II cells can provide help for generation of Ab to P. chabaudi infection and can control this otherwise lethal infection in CD40L-deficient mice. PbT-II cells can also provide help for development of CD8+ T cell–mediated experimental cerebral malaria (ECM) during PbA infection. Using PbT-II CD4+ T cells and the previously described PbT-I CD8+ T cells, we determined the dendritic cell (DC) subsets responsible for immunity to PbA blood-stage infection. CD8+ DC (a subset of XCR1+ DC) were the major APC responsible for activation of both T cell subsets, although other DC also contributed to CD4+ T cell responses. Depletion of CD8+ DC at the beginning of infection prevented ECM development and impaired both Th1 and follicular Th cell responses; in contrast, late depletion did not affect ECM. This study describes a novel and versatile tool for examining CD4+ T cell immunity during malaria and provides evidence that CD4+ T cell help, acting via CD40L signaling, can promote immunity or pathology to blood-stage malaria largely through Ag presentation by CD8+ DC.

Transcriptome Dynamics Reveals Progressive Transition from Effector to Memory in CD4+T cells

“…Mice exhibit a protective CD4 + T cell response dominated by Th1 and Tfh cells (Meding et al, 1990; Perez-Mazliah et al, 2015). Given that TCR sequence influences effector fate decisions (Tubo et al, 2013), we controlled for this using PbTII cells (Fernandez-Ruiz et al, 2017), a CD4 + TCR transgenic T cell line that differentiates simultaneously into T-bet hi IFNγ + Th1 cells and Bcl6 hi CXCR5 hi Tfh effector cells by the end of the first week of Pc AS infection (Lonnberg et al, 2017), but whose long term kinetics were unknown. The PbTII/ Pc AS model permitted tracking of two independent CD4 + T cell effector types in one infection.…”

“…Instead, we noted substantial heterogeneity in the micro-anatomical location of PbTIIs at peak, relative to T and B cell zones. Given that B cells and myeloid cells control PbTII effector fate (Fernandez-Ruiz et al, 2017; James et al, 2018; Lonnberg et al, 2017) we hypothesize that cell-cell interactions are primary drivers of memory fate. Assuming that progeny from a naïve CD4 + T cell stay within the same vicinity after clonal expansion, at least before and during effector differentiation, it is possible that similar T cell-extrinsic signals and cell-cell interactions in the area will promote the same effector and memory fate amongst a family.…”

“…C57BL/6J mice were purchased from Animal Resources Centre (Canning Vale), PbTII (Fernandez-Ruiz et al, 2017) and nzEGFP (Bhat et al, 2014) mice were bred in-house. nzEGFP mice express enhanced green fluorescent protein (EGFP) from the ubiquitously expressed CMV early enhancer/chicken beta actin promotor.…”

A virus hosted in malaria-infected blood protects against T cell-mediated inflammatory diseases by impairing DC function in a type I IFN-dependent manner

“…It has now become clear that IL-12p35 65 , IFN-γ and IL-17 66 are dispensable for the development of MOG-induced EAE while the key pathogenic cytokines are GM-CSF produced by CD4 + Th cells and IL-23, which may be produced by multiple sources 66,67 . Also, in contrast to ECM pathology in which cDC are required for the priming and polarization of Th1 CD4 + T cells [49][50][51] , cDC are not necessary for the priming of encephalitogenic CD4 + Th cells in MOG protein-induced EAE 68 and mice lacking cDC even display an aggravated disease 69 . Based on this, we propose that LDV-mediated protection against EAE is due to the global effect of IFN-I signaling, which inhibits IL-23 production by several different cell types of the dLN, including cDC, and that this prevents the differentiation of GM-CSF-secreting CD4 + T cells.…”

“…To study how LDV impedes the Th1 CD4 + T cell response, we analyzed splenic conventional DC (cDC), which are primarily responsible for Th1 priming and polarization in this context [49][50][51] . Two days following Pb ANKA / LDV co-infection, we observed a strong reduction in the proportion and numbers of total CD11c + MHCII + cDC, which was not observed in Ifnar1 KO mice ( Fig.…”