Liver-Resident Memory CD8+ T Cells Form a Front-Line Defense against Malaria Liver-Stage Infection.

In recent years, various intervention strategies have reduced malaria morbidity and mortality, but further improvements probably depend upon development of a broadly protective vaccine. To better understand immune requirement for protection, we examined liver-stage immunity after vaccination with irradiated sporozoites, an effective though logistically difficult vaccine. We identified a population of memory CD8+ T cells that expressed the gene signature of tissue-resident memory T (Trm) cells and remained permanently within the liver, where they patrolled the sinusoids. Exploring the requirements for liver Trm cell induction, we showed that by combining dendritic cell-targeted priming with liver inflammation and antigen recognition on hepatocytes, high frequencies of Trm cells could be induced and these cells were essential for protection against malaria sporozoite challenge. Our study highlights the immune potential of liver Trm cells and provides approaches for their selective transfer, expansion, or depletion, which may be harnessed to control liver infections or autoimmunity.

The Australian New Zealand Consortium in Children, Adolescents, and Young Adults Oncofertility action plan.

International and national oncofertility networks, including the US-led Oncofertility Consortium, FertiProtekt, and the Danish Network, have played pivotal roles in advancing the discipline of oncofertility over the last decade. Many other countries lack a shared approach to pediatric oncofertility health service delivery. This study aims to describe baseline oncofertility practices at Australian New Zealand Children's Haematology/Oncology Group centers in 2019-2021, describe binational priorities for care, and propose a 5-year action plan for best practice to be implemented by the newly formed Australian New Zealand Consortium in Children, Adolescents, and Young Adults (CAYA) Oncofertility (ANZCO).

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.

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.

CD8+ T cells from a novel T cell receptor transgenic mouse induce liver-stage immunity that can be boosted by blood-stage infection in rodent malaria.

To follow the fate of CD8+ T cells responsive to Plasmodium berghei ANKA (PbA) infection, we generated an MHC I-restricted TCR transgenic mouse line against this pathogen. T cells from this line, termed PbT-I T cells, were able to respond to blood-stage infection by PbA and two other rodent malaria species, P. yoelii XNL and P. chabaudi AS. These PbT-I T cells were also able to respond to sporozoites and to protect mice from liver-stage infection. Examination of the requirements for priming after intravenous administration of irradiated sporozoites, an effective vaccination approach, showed that the spleen rather than the liver was the main site of priming and that responses depended on CD8α+ dendritic cells. Importantly, sequential exposure to irradiated sporozoites followed two days later by blood-stage infection led to augmented PbT-I T cell expansion. These findings indicate that PbT-I T cells are a highly versatile tool for studying multiple stages and species of rodent malaria and suggest that cross-stage reactive CD8+ T cells may be utilized in liver-stage vaccine design to enable boosting by blood-stage infections.

Blood-stage Plasmodium berghei infection generates a potent, specific CD8+ T-cell response despite residence largely in cells lacking MHC I processing machinery.

Murine cerebral malaria is a complex disease caused by Plasmodium berghei ANKA infection. Several cell types, including CD8(+) T cells, are essential effectors of disease. Although the use of transgenic parasites expressing model antigens has revealed the induction of cytotoxic T lymphocytes (CTL) specific for these model antigens, there is no direct evidence for a response to authentic blood-stage parasite antigens, nor any knowledge of its magnitude. Our studies show that there is a dramatic primary parasite-specific CTL response, akin to viral immunity, reaching approximately 30% of splenic CD8(+) T cells, with many producing interferon-γ and tumor necrosis factor-α. These cells express granzyme B and other markers of specific responders, are cytolytic, and respond to a broad array of major histocompatibility complex (MHC) I-restricted epitopes, 5 of which are identified here. Our studies indicate that vigorous CTL responses can be induced to pathogens even when they largely reside in red blood cells, which lack MHC I processing machinery.

SOCS-1 binding to tyrosine 441 of IFN-gamma receptor subunit 1 contributes to the attenuation of IFN-gamma signaling in vivo.

Suppressor of cytokine signaling (SOCS)-1 is a critical inhibitor of IFN-gamma signal transduction in vivo, but the precise biochemical mechanism of action of SOCS-1 is unclear. Studies in vitro have shown that SOCS-1 binds to Jaks and inhibits their catalytic activity, but recent studies indicate SOCS-1 may act in a similar manner to SOCS-3 by firstly interacting with cytokine receptors and then inhibiting Jak activity. Here, we have generated mice, termed Ifngr1(441F), in which a putative SOCS-1 binding site, tyrosine 441 (Y441), on the IFN-gamma receptor subunit 1 (IFNGR1) is mutated. We confirm that SOCS-1 binds to IFNGR1 in wild-type but not mutant cells. Mutation of Y441 results in impaired negative regulation of IFN-gamma signaling. IFN-gamma-induced STAT1 activation is prolonged in Ifngr1(441F) cells, but not to the extent seen in cells completely lacking SOCS-1, suggesting that SOCS-1 maintains activity to modulate IFN-gamma signaling via other mechanisms. Despite this, we show that hypersensitivity to IFN-gamma results in enhanced innate tumor protection in Ifngr1(441F) mice in vivo, and unregulated expression of an IFN-gamma-dependent chemokine, monokine-induced by IFN-gamma. Collectively, these data indicate that Y441 contributes to the regulation of signaling through IFNGR1 via the recruitment of SOCS-1 to the receptor.

Blood-stage Plasmodium infection induces CD8+ T lymphocytes to parasite-expressed antigens, largely regulated by CD8alpha+ dendritic cells.

Although CD8(+) T cells do not contribute to protection against the blood stage of Plasmodium infection, there is mounting evidence that they are principal mediators of murine experimental cerebral malaria (ECM). At present, there is no direct evidence that the CD8(+) T cells mediating ECM are parasite-specific or, for that matter, whether parasite-specific CD8(+) T cells are generated in response to blood-stage infection. To resolve this and to define the cellular requirements for such priming, we generated transgenic P. berghei parasites expressing model T cell epitopes. This approach was necessary as MHC class I-restricted antigens to blood-stage infection have not been defined. Here, we show that blood-stage infection leads to parasite-specific CD8(+) and CD4(+) T cell responses. Furthermore, we show that P. berghei-expressed antigens are cross-presented by the CD8alpha(+) subset of dendritic cells (DC), and that this induces pathogen-specific cytotoxic T lymphocytes (CTL) capable of lysing cells presenting antigens expressed by blood-stage parasites. Finally, using three different experimental approaches, we provide evidence that CTL specific for parasite-expressed antigens contribute to ECM.

Paxillin nuclear-cytoplasmic localization is regulated by phosphorylation of the LD4 motif: evidence that nuclear paxillin promotes cell proliferation.

Paxillin, a major focal-adhesion complex component belongs to the subfamily of LIM domain proteins and participates in cell adhesion-mediated signal transduction. It is implicated in cell-motility responses upon activation of cell-surface receptors and can recruit, among others, the GIT1 [GRK (G-protein-coupled-receptor kinase)-interacting ARF (ADP-ribosylation factor) GAP (GTPase-activating protein)]-PIX [PAK (p21-activated kinase)-interacting exchange factor]-PAK1 complex. Several adhesion proteins including zyxin, Hic5 and Trip6 are also nuclear and can exert transcriptional effects. In the present study we show that endogenous paxillin shuttles between the cytoplasm and nucleus, and we have used a variety of tagged paxillin constructs to map the nuclear export signal. This region overlaps an important LD(4) motif that binds GIT1 and FAK1 (focal-adhesion kinase 1). We provide evidence that phosphorylation of Ser(272) within LD(4) blocks nuclear export, and we show that this modification also reduces GIT1, but not FAK1, binding; however, Ser(272) phosphorylation does not appear to be mediated by PAK1 as previously suggested. Expression of nuclear-localized paxillin LIM domains stimulate DNA synthesis and cell proliferation. By real-time PCR analysis we have established that overexpression of either full-length paxillin or a truncated nuclear form suppresses expression of the parental imprinted gene H19, and modulation of this locus probably affects the rate of NIH-3T3 cell proliferation.