Activation and IL-10 production of specific CD4+ T cells are regulated by IL-27 during chronic infection with Plasmodium chabaudi

Regulation of memory CD4+ T-cell generation by intrinsic and extrinsic IL-27 signaling during malaria infection

The generation and maintenance of memory T cells are regulated by various factors, including cytokines. Previous studies have shown that IL-27 is produced during the early acute phase of Plasmodium chabaudi chabaudi AS (Pcc) infection and inhibits the development of Th1-type memory CD4+ T cells. However, whether IL-27 acts directly on its receptor on Plasmodium-specific CD4+ T cells or indirectly via its receptor on other immune cells remains unclear. We aimed to determine the role of IL-27 receptor signaling in different immune cell types in regulating the generation and phenotype of memory CD4+ T cells during Plasmodium infection. We utilized Plasmodium-specific T-cell antigen receptor (TCR) transgenic mice, PbT-II, and Il27rα-/- mice to assess the direct and indirect effects of IL-27 signaling on memory CD4+ T-cell generation. Mice were transferred with PbT-II or Il27rα-/- PbT-II cells and infected with Pcc. Conditional knockout mice lacking the IL-27 receptor in T cells or dendritic cells were employed to discern the specific immune cell types involved in IL-27 receptor signaling. High levels of memory in PbT-II cells with Th1-shift occurred only when both PbT-II and host cells lacked the IL-27 receptor, suggesting the predominant inhibitory role of IL-27 signaling in both cell types. Furthermore, IL-27 receptor signaling in T cells limited the number of memory CD4+ T cells, while signaling in both T and dendritic cells contributed to the Th1 dominance of memory CD4+ T cells. These findings underscore the complex cytokine signaling network regulating memory CD4+ T cells during Plasmodium infection.

Cytokine gene polymorphisms implicated in the pathogenesis of Plasmodium falciparum infection outcome

Cytokines play a critical role in the immune mechanisms involved in fighting infections including malaria. Polymorphisms in cytokine genes may affect immune responses during an infection with Plasmodium parasites and immunization outcomes during routine administration of malaria vaccines. These polymorphisms can increase or reduce susceptibility to this deadly infection, and this may affect the physiologically needed balance between anti-inflammatory and pro-inflammatory cytokines. The purpose of this review is to present an overview of the effect of selected cytokine gene polymorphisms on immune responses against malaria.

IL-27 produced during acute malaria infection regulates Plasmodium-specific memory CD4+ T cells

Malaria infection elicits both protective and pathogenic immune responses, and IL-27 is a critical cytokine that regulate effector responses during infection. Here, we identified a critical window of CD4+ T cell responses that is targeted by IL-27. Neutralization of IL-27 during acute infection with Plasmodium chabaudi expanded specific CD4+ T cells, which were maintained at high levels thereafter. In the chronic phase, Plasmodium-specific CD4+ T cells in IL-27-neutralized mice consisted mainly of CD127+ KLRG1- and CD127- KLRG1+ subpopulations that displayed distinct cytokine production, proliferative capacity, and are maintained in a manner independent of active infection. Single-cell RNA-seq analysis revealed that these CD4+ T cell subsets formed independent clusters that express unique Th1-type genes. These IL-27-neutralized mice exhibited enhanced cellular and humoral immune responses and protection. These findings demonstrate that IL-27, which is produced during the acute phase of malaria infection, inhibits the development of unique Th1 memory precursor CD4+ T cells, suggesting potential implications for the development of vaccines and other strategic interventions.

The interleukin-10 family: Major regulators of the immune response against Plasmodium falciparum infections

Malaria caused by the Plasmodium falciparum strain is more severe because of this protozoan's ability to disrupt the physiology of host cells during the blood stages of development by initiating the production of the interleukin-10 (IL-10) family of cytokines. P. falciparum feeds on hemoglobin and causes host cells to adhere to the walls of blood vessels by remodeling their composition. IL-10 is produced by CD4+ T cells that inhibits antigen-presenting cells' activity to prevent inflammation. This cytokine and its family members are crucial in promoting malarial infection by inhibiting the host's protective immune response, thus initiating Plasmodium parasitemia. IL-10 is also responsible for preventing severe pathology during Plasmodium infection and initiates several signaling pathways to alter the physiology of host cells during malarial infection. This review summarizes the critical aspects of P. falciparum infection, including its role in signaling pathways for cytokine exudation, its effect on microRNA, the human immune response in malaria, and the role played by the liver hormone hepcidin. Moreover, future aspects of vaccine development and therapeutic strategies to combat P. falciparum infections are also discussed in detail.

Mouse Models for Unravelling Immunology of Blood Stage Malaria

Malaria comprises a spectrum of disease syndromes and the immune system is a major participant in malarial disease. This is particularly true in relation to the immune responses elicited against blood stages of Plasmodium-parasites that are responsible for the pathogenesis of infection. Mouse models of malaria are commonly used to dissect the immune mechanisms underlying disease. While no single mouse model of Plasmodium infection completely recapitulates all the features of malaria in humans, collectively the existing models are invaluable for defining the events that lead to the immunopathogenesis of malaria. Here we review the different mouse models of Plasmodium infection that are available, and highlight some of the main contributions these models have made with regards to identifying immune mechanisms of parasite control and the immunopathogenesis of malaria.

The Role of MIF and IL-10 as Molecular Yin-Yang in the Modulation of the Host Immune Microenvironment During Infections: African Trypanosome Infections as a Paradigm

African trypanosomes are extracellular flagellated unicellular protozoan parasites transmitted by tsetse flies and causing Sleeping Sickness disease in humans and Nagana disease in cattle and other livestock. These diseases are usually characterized by the development of a fatal chronic inflammatory disease if left untreated. During African trypanosome infection and many other infectious diseases, the immune response is mediating a see-saw balance between effective/protective immunity and excessive infection-induced inflammation that can cause collateral tissue damage. African trypanosomes are known to trigger a strong type I pro-inflammatory response, which contributes to peak parasitaemia control, but this can culminate into the development of immunopathologies, such as anaemia and liver injury, if not tightly controlled. In this context, the macrophage migration inhibitory factor (MIF) and the interleukin-10 (IL-10) cytokines may operate as a molecular “Yin-Yang” in the modulation of the host immune microenvironment during African trypanosome infection, and possibly other infectious diseases. MIF is a pleiotropic pro-inflammatory cytokine and critical upstream mediator of immune and inflammatory responses, associated with exaggerated inflammation and immunopathology. For example, it plays a crucial role in the pro-inflammatory response against African trypanosomes and other pathogens, thereby promoting the development of immunopathologies. On the other hand, IL-10 is an anti-inflammatory cytokine, acting as a master regulator of inflammation during both African trypanosomiasis and other diseases. IL-10 is crucial to counteract the strong MIF-induced pro-inflammatory response, leading to pathology control. Hence, novel strategies capable of blocking MIF and/or promoting IL-10 receptor signaling pathways, could potentially be used as therapy to counteract immunopathology development during African trypanosome infection, as well as during other infectious conditions. Together, this review aims at summarizing the current knowledge on the opposite immunopathological molecular “Yin-Yang” switch roles of MIF and IL-10 in the modulation of the host immune microenvironment during infection, and more particularly during African trypanosomiasis as a paradigm.

Recent Advances in Understanding the Inflammatory Response in Malaria: A Review of the Dual Role of Cytokines

Malaria is a serious and, in some unfortunate cases, fatal disease caused by a parasite of the Plasmodium genus. It predominantly occurs in tropical areas where it is transmitted through the bite of an infected Anopheles mosquito. The pathogenesis of malaria is complex and incompletely elucidated. During blood-stage infection, in response to the presence of the parasite, the host's immune system produces proinflammatory cytokines including IL-6, IL-8, IFN-γ, and TNF, cytokines which play a pivotal role in controlling the growth of the parasite and its elimination. Regulatory cytokines such as transforming growth factor- (TGF-) β and IL-10 maintain the balance between the proinflammatory and anti-inflammatory responses. However, in many cases, cytokines have a double role. On the one hand, they contribute to parasitic clearance, and on the other, they are responsible for pathological changes encountered in malaria. Cytokine-modulating strategies may represent a promising modern approach in disease management. In this review, we discuss the host immune response in malaria, analyzing the latest studies on the roles of pro- and anti-inflammatory cytokines.

Type I interferon production elicits differential CD4 + T-cell responses in mice infected with Plasmodium berghei ANKA and P. chabaudi

Plasmodium parasites that infect humans are highly polymorphic, and induce various infections ranging from asymptomatic state to life-threatening diseases. However, how the differences between the parasites affect host immune responses during blood-stage infection remains largely unknown. We investigated the CD4 + T-cell immune responses in mice infected with P. berghei ANKA (PbA) or P. chabaudi chabaudi AS (Pcc) using PbT-II cells, which recognize a common epitope of these parasites. In the acute phase of infection, CD4 + T-cell responses in PbA-infected mice showed a lower involvement of Th1 cells and a lower proportion of Ly6C lo effector CD4 + T cells than those in Pcc-infected mice. Transcriptome analysis of PbT-II cells indicated that type I interferon (IFN)-regulated genes were expressed at higher levels in both Th1- and Tfh-type PbT-II cells from PbA-infected mice than those from Pcc-infected mice. Moreover, IFN-α levels were considerably higher in PbA-infected mice than in Pcc-infected mice. Inhibition of type I IFN signaling increased PbT-II and partially reversed the Th1 over Tfh bias of the PbT-II cells in both PbA- and Pcc-infected mice. In the memory phase, PbT-II cells in PbA-primed mice maintained higher numbers and exhibited better recall response to the antigen. However, recall responses were not significantly different between the infection groups after re-challenge with PbA, suggesting the effect of inflammatory environment by the infection. These observations suggest that the differences in Plasmodium-specific CD4 + T-cell responses between PbA- and Pcc-infected mice were associated with the difference in type I IFN production during the early phase of the infection.

Host-pathogen interaction in the tissue environment during Plasmodium blood-stage infection

Human malarial infection occurs after an infectious Anopheles mosquito bites. Following the initial liver-stage infection, parasites transform into merozoites, infecting red blood cells (RBCs). Repeated RBC infection then occurs during the blood-stage infection, while patients experience various malarial symptoms. Protective immune responses are elicited by this systemic infection, but excessive responses are sometimes harmful for hosts. As parasites infect only RBCs and their immediate precursors during this stage, direct parasite-host interactions occur primarily in the environment surrounded by endothelial lining of blood vessels. The spleen is the major organ where the immune system encounters infected RBCs, causing immunological responses. Its tissue structure is markedly altered during malarial infection in mice and humans. Plasmodium falciparum parasites inside RBCs express proteins, such as PfEMP-1 and RIFIN, transported to the RBC surfaces in order to evade immunological attack by sequestering themselves in the peripheral vasculature avoiding spleen or by direct immune cell inhibition through inhibitory receptors. Host cell production of regulatory cytokines IL-10 and IL-27 limits excessive immune responses, avoiding tissue damage. The regulation of the protective and inhibitory immune responses through host-parasite interactions allows chronic Plasmodium infection. In this review, we discuss underlying interaction mechanisms relevant for developing effective strategies against malaria.

Altered Frequency of NK Cells and Treg Cells by Astragalus Polysaccharide Combined with Budesonide in Asthma Model Mice

Objective. We investigated the efficacy of astragalus polysaccharide (APS) combined with budesonide and the effect on expressions of peripheral NK cells and Treg cells and the molecular mechanism in mice with bronchial asthma. Methods. In this study, we established a mouse model of asthma. Four groups of BaLB/C mice were developed; control group had no asthma induction, and the other three groups of mice were sensitized by OVA (Ovalbumin), OVA + budesonide, and OVA + APS + budesonide. Flow cytometry was used to determine the proportion of NK cells and Treg cells. Levels of cytokines IL-4 and IL-10 were detected using RT-PCR and ELISA. Results. Asthma mice treated with APS + budesonide showed alleviated airway resistance compared to model mice (P<0.05). The percentage of dendritic cells (DCs) was reduced (P<0.05), while anti-inflammatory NK cells and Treg cells significantly increased after APS + budesonide treatment (P<0.05). Further, APS + budesonide treatment resulted in improvements in IL-4 and IL-10 mRNA and protein levels (P<0.05). Conclusion. APS combined with budesonide medication may regulate expressions of DCs cells and related cytokines, reliving clinical symptom of bronchial asthma.

A Critical Blimp-1-Dependent IL-10 Regulatory Pathway in T Cells Protects From a Lethal Pro-inflammatory Cytokine Storm During Acute Experimental Trypanosoma brucei Infection

In many infectious diseases, the immune response operates as a double-edged sword. While required for protective immunity, infection-induced inflammation can be detrimental if it is not properly controlled, causing collateral body damage and potentially leading to death. It is in this context that the potent anti-inflammatory cytokine interleukin-10 (IL-10) is required to dampen the pro-inflammatory immune response that hallmarks trypanosomosis. Effective control of this infection requires not just the action of antibodies specific for the parasite's variable surface glycoprotein (VSG) coat antigens, but also a pro-inflammatory immune response mediated mainly by IFNγ, TNF, and NO. However, strict control of inflammation is mandatory, as IL-10-deficient mice succumb from an unrestrained cytokine storm within 10 days of a Trypanosome brucei infection. The relevant cellular source of IL-10 and the associated molecular mechanisms implicated in its trypanosomosis associated production are poorly understood. Using an IL-10 reporter mouse strain (Vert-X), we demonstrate here that NK cells, CD8⁺ T cells and CD4⁺ T cells as well as B cells and plasma cells constitute potential cellular sources of IL-10 within the spleen and liver during acute infection. The IL-10 wave follows peak pro-inflammatory cytokine production, which accompanied the control of peak parasitemia. Similar results were observed following conventional experimental needle infection and physiological infections via T. brucei-infected tsetse flies. Our results show that conditional T cell-specific ablation of the IL-10 regulating Prdm1 gene (encoding for the Blimp-1 transcription factor), leads to an uncontrolled trypanosome-induced pro-inflammatory syndrome like the one observed in infected IL-10-deficient mice. This result indicates that the biological role of IL-10-derived from non-T cells, including NK cells, is of minor importance when considering host survival. The cytokine IL-27 that is also considered to be an IL-10 regulator, did not affect IL-10 production during infection. Together, these data suggest that T. brucei activates a Blimp-1-dependent IL-10 regulatory pathway in T cells that acts as a critical anti-inflammatory rheostat, mandatory for host survival during the acute phase of parasitemia.