Eosinophils Suppress the Migration of T Cells Into the Brain of Plasmodium berghei-Infected Ifnar1-/- Mice and Protect Them From Experimental Cerebral Malaria.

Cerebral malaria is a potentially lethal disease, which is caused by excessive inflammatory responses to Plasmodium parasites. Here we use a newly developed transgenic Plasmodium berghei ANKA (PbAAma1OVA) parasite that can be used to study parasite-specific T cell responses. Our present study demonstrates that Ifnar1-/- mice, which lack type I interferon receptor-dependent signaling, are protected from experimental cerebral malaria (ECM) when infected with this novel parasite. Although CD8+ T cell responses generated in the spleen are essential for the development of ECM, we measured comparable parasite-specific cytotoxic T cell responses in ECM-protected Ifnar1-/- mice and wild type mice suffering from ECM. Importantly, CD8+ T cells were increased in the spleens of ECM-protected Ifnar1-/- mice and the blood-brain-barrier remained intact. This was associated with elevated splenic levels of CCL5, a T cell and eosinophil chemotactic chemokine, which was mainly produced by eosinophils, and an increase in eosinophil numbers. Depletion of eosinophils enhanced CD8+ T cell infiltration into the brain and increased ECM induction in PbAAma1OVA-infected Ifnar1-/- mice. However, eosinophil-depletion did not reduce the CD8+ T cell population in the spleen or reduce splenic CCL5 concentrations. Our study demonstrates that eosinophils impact CD8+ T cell migration and proliferation during PbAAma1OVA-infection in Ifnar1-/- mice and thereby are contributing to the protection from ECM.

Tissue macrophages and interferon-gamma signalling control blood-stage Plasmodium chabaudi infections derived from mosquito-transmitted parasites.

Natural infection with Plasmodium parasites, the causative agents of malaria, occurs via mosquito vectors. However, most of our knowledge of the immune response to the blood stages of Plasmodium is from infections initiated by injection of serially blood-passaged infected red blood cells, resulting in an incomplete life cycle in the mammalian host. Vector transmission of the rodent malaria parasite, Plasmodium chabaudi chabaudi AS has been shown to give rise to a more attenuated blood-stage infection in C57Bl/6J mice, when compared to infections initiated with serially blood-passaged P. chabaudi-infected red blood cells. In mouse models, the host immune response induced by parasites derived from natural mosquito transmission is likely to more closely resemble the immune responses to Plasmodium infections in humans. It is therefore important to determine how the host response differs between the two types of infections. As the spleen is considered to be a major contributor to the protective host response to P. chabaudi, we carried out a comparative transcriptomic analysis of the splenic response to recently mosquito-transmitted and serially blood-passaged parasites in C57Bl/6J mice. The attenuated infection arising from recently mosquito-transmitted parasites is characterised by an earlier and stronger myeloid- and IFNγ-related response. Analyses of spleen lysates from the two infections similarly showed stronger or earlier inflammatory cytokine and chemokine production in the recently mosquito-transmitted blood-stage infections. Furthermore, tissue macrophages, including red pulp macrophages, and IFNγ-signalling in myeloid cells, are required for the early control of P. chabaudi recently mosquito-transmitted parasites, thus contributing to the attenuation of mosquito-transmitted infections. The molecules responsible for this early activation response to recently-transmitted blood-stage parasites in mice would be important to identify, as they may help to elucidate the nature of the initial interactions between blood-stage parasites and the host immune system in naturally transmitted malaria.

Effects of Personal Body Armor on Functional Movement Capability.

The Functional Movement Screen (FMS) is a tool used to assess fundamental movement patterns and has been utilized to determine movement readiness of tactical athletes. However, tactical athletes rarely perform tasks without load carriage, and limited research evaluating loaded tactical personnel via the FMS has been conducted. Therefore, the primary aim of this study was to determine if ballistic vest wear results in movement deficits as evaluated by the FMS. A convenience sample of college students (n = 31) completed test sessions in loaded and unloaded conditions. Subjects completed each FMS movement and indicated perceived effort on a Visual Analog Scale (VAS). The Sign test was used to determine difference between FMS composite and component scores collected under each condition. The level of significance was set at p < 0.05. A significant (p < 0.001) difference in FMS composite scores was identified between loading conditions. Significant FMS score changes between load conditions were identified in the dominant side in-line lunge (p < 0.01), non-dominant side in-line lunge (p < 0.01), dominant shoulder mobility (p < 0.01), non-dominant shoulder mobility (p < 0.01), and non-dominant rotary stability (p = 0.01). Our data indicate ballistic vest wear reduces overall functional movement capacity, as well as mobility related to certain individual FMS components in the population examined. Additionally, results suggest subjects may better tolerate additional load carriage when completing tasks on their dominant side. These results raise important questions regarding design, fit, and task completion for tactical athletes utilizing a ballistic vest.

A New Link between γδ T Cells and Myeloid Cells in Malaria?

In malaria, the immune responses leading to protective immunity versus immunopathology are unclear. Mamedov et al. (2018) identify a subset of clonally expanded γδ T cells in late-stage infection that produce M-CSF and may interact with myeloid cells to control recrudescent infection.

Follicular Helper T Cells are Essential for the Elimination of Plasmodium Infection.

CD4+ follicular helper T (Tfh) cells have been shown to be critical for the activation of germinal center (GC) B-cell responses. Similar to other infections, Plasmodium infection activates both GC as well as non-GC B cell responses. Here, we sought to explore whether Tfh cells and GC B cells are required to eliminate a Plasmodium infection. A CD4 T cell-targeted deletion of the gene that encodes Bcl6, the master transcription factor for the Tfh program, resulted in complete disruption of the Tfh response to Plasmodium chabaudi in C57BL/6 mice and consequent disruption of GC responses and IgG responses and the inability to eliminate the otherwise self-resolving chronic P. chabaudi infection. On the other hand, and contrary to previous observations in immunization and viral infection models, Signaling Lymphocyte Activation Molecule (SLAM)-Associated Protein (SAP)-deficient mice were able to activate Tfh cells, GC B cells, and IgG responses to the parasite. This study demonstrates the critical role for Tfh cells in controlling this systemic infection, and highlights differences in the signals required to activate GC B cell responses to this complex parasite compared with those of protein immunizations and viral infections. Therefore, these data are highly pertinent for designing malaria vaccines able to activate broadly protective B-cell responses.

Chemical attenuation of Plasmodium in the liver modulates severe malaria disease progression.

Cerebral malaria is one of the most severe complications of malaria disease, attributed to a complicated series of immune reactions in the host. The syndrome is marked by inflammatory immune responses, margination of leukocytes, and parasitized erythrocytes in cerebral vessels leading to breakdown of the blood-brain barrier. We show that chemical attenuation of the parasite at the very early, clinically silent liver stage suppresses parasite development, delays the time until parasites establish blood-stage infection, and provokes an altered host immune response, modifying immunopathogenesis and protecting from cerebral disease. The early response is proinflammatory and cell mediated, with increased T cell activation in the liver and spleen, and greater numbers of effector T cells, cytokine-secreting T cells, and proliferating, proinflammatory cytokine-producing T cells. Dendritic cell numbers, T cell activation, and infiltration of CD8(+) T cells to the brain are decreased later in infection, possibly mediated by the anti-inflammatory cytokine IL-10. Strikingly, protection can be transferred to naive animals by adoptive transfer of lymphocytes from the spleen at very early times of infection. Our data suggest that a subpopulation belonging to CD8(+) T cells as early as day 2 postinfection is responsible for protection. These data indicate that liver stage-directed early immune responses can moderate the overall downstream host immune response and modulate severe malaria outcome.

Plasmodium attenuation: connecting the dots between early immune responses and malaria disease severity.

Sterile attenuation of Plasmodium parasites at the liver-stage either by irradiation or genetic modification, or at the blood-stage by chemoprophylaxis, has been shown to induce immune responses that can protect against subsequent wild-type infection. However, following certain interventions, parasite attenuation can be incomplete or non-sterile. Instead parasites are rendered developmentally stunted but still capable of establishing an acute infection. In experiments involving Plasmodium berghei ANKA, a model of experimental cerebral malaria, it has been observed that several forms of attenuated parasites do not induce cerebral pathology. In this perspective we collect evidence from studies on murine malaria in particular, and attempt to "connect the dots" between early immune responses and protection from severe cerebral disease, highlighting potential parallels to human infection.

CD8(+) T cells mediate robust stage-specific immunity to P. berghei under chemoprophylaxis and this protective environment is not downregulated by the presence of blood-stage infection.

Sterile protection against malaria infection can be achieved by the inoculation of intact sporozoites while treating concomitantly with the 4-aminoquinoline chloroquine. We present an analysis of protective immunity elicited by successive immunization with Plasmodium berghei sporozoites under chemoprophylaxis. Immunization resulted in a protective, stage-specific immune response. Protection appeared to be mediated by CD8(+) T cells and was abrogated upon their specific depletion. Adoptive transfer of splenocytes rendered recipient animals resistant to sporozoite infection, but not to blood-stage challenge. Immunization with sporozoites under chemoprophylaxis results in robust immunity, and the presence of blood-stage infection at sporozoite immunization had no downregulating effect on the protective immune response.

A primaquine-chloroquine hybrid with dual activity against Plasmodium liver and blood stages.

We present a new class of hybrid molecules consisting of the established antiplasmodial drugs primaquine and chloroquine. No drug is known to date that acts comparably against all stages of Plasmodium in its life cycle. Starting from available precursors, we designed and synthesized a new-generation compound consisting of both primaquine and chloroquine components, with the intent to produce agents that exhibit bioactivity against different stages of the parasite's life cycle. In vitro, the hybrid molecule 3 displays activity against both asexual and sexual P. falciparum blood stages as well as P. berghei sporozoites and liver stages. In vivo, the hybrid elicits activity against P. berghei liver and blood stages. Our results successfully validate the concept of utilizing one compound to combine different modes of action that attack different Plasmodium stages in the mammalian host. It is our hope that the novel design of such compounds will outwit the pathogen in the spread of drug resistance. Based on the optimized synthetic pathway, the compound is accessible in a smooth and versatile way and open for potential further molecular modification.

Continuous oral chloroquine as a novel route for Plasmodium prophylaxis and cure in experimental murine models.

BACKGROUND: Chloroquine (CQ) is utilized as both cure and prophylaxis to Plasmodium infection. In animal studies, CQ administration to experimental animals is via intraperitoneal (i.p.) injection of a single dose that varies from daily to several times per week. Such daily administration can be distressing to the animals and provoke aggressive behaviors that may affect the immune responses of the animal and interfere with data read-outs. FINDINGS: We describe a novel, viable and efficacious prophylactic and curative administration route whereby chloroquine is continuously supplied in the drinking water to experimental animals. The prophylactic effect is robust and the curative effect against patent blood stage infection comparable to the traditional route of i.p. administration. Continuous drinking water administration may decrease animal stress responses and thus improve the reliability of experimental data.