Interleukin-27 exhibited anti-inflammatory activity during Plasmodium berghei infection in mice

Interleukin-27 (IL-27) has a pleiotropic role either as a pro-inflammatory or anti-inflammatory cytokine in inflammatory related diseases. The role and involvement of IL-27 during malaria was investigated and the effects of modulating its release on the production of major inflammatory cytokines and the histopathological consequences in major affected organs during the infection were evaluated. Results showed that IL-27 concentration was significantly elevated throughout the infection but no positive correlation with the parasitaemia development observed. Augmentation of IL-27 significantly elevated the release of anti-inflammatory cytokine, IL-10 whereas antagonising and neutralising IL-27 produced the opposite. A significant elevation of pro-inflammatory cytokines (IFN-γ and IL-6) was also observed, both during augmentation and inhibition of IL-27. Thus, it is suggested that IL-27 exerts an anti-inflammatory activity in the Th1 type response by signalling the production of IL-10 during malaria. Histopathological examination showed sequestration of PRBC in the microvasculature of major organs in malarial mice. Other significant histopathological changes include hyperplasia and hypertrophy of the Kupffer cells in the liver, hyaline membrane formation in lung tissue, enlargement of the white and red pulp followed by the disappearance of germinal centre of the spleen, and tubular vacuolation of the kidney tissues. In conclusion, it is suggested that IL-27 may possibly acts as an anti-inflammatory cytokine during the infection. Modulation of its release produced a positive impact on inflammatory cytokine production during the infection, suggesting its potential in malaria immunotherapy, in which the host may benefit from its inhibition

Understanding innate immunity to Plasmodium falciparum malaria

© 2018 Dr. Marzieh JabbarzareThe malaria parasite Plasmodium falciparum still causes an incredibly high number of deaths in young children under the age of five and pregnant women annually. The pathogenesis of human malaria is due to a combination of several parasite and host factors that simultaneously influence the severity and outcome of disease. Thus, a better understanding of the roles played by innate immune cells in both pregnancy and non-pregnancy related malaria infection is crucial. In Aim 1, an in vitro model of human peripheral blood mononuclear cells (PBMCs) derived from non-immune individuals were exposed to infected erythrocytes (IEs) expressing different P. falciparum erythrocyte membrane protein 1 (PfEMP1) binding phenotypes. This included IT parasites lines (CS2, a placental parasite line expressing VAR2CSA which binds to chondroitin sulfate A (CSA) and E8B (CD36 binding)) and NF54 lines (3C (non-CD36 binding) and 3D7 (CD36 binding)). The objectives were to identify whether PfEMP1 binding phenotypes influence PBMCs cytokine response, and also to determine whether CD36 binding is parasite characteristic that influences the innate immune response. Higher cytokines secretions were observed when PBMCs were stimulated with non-CD36 binding IEs in comparison with CD36 binding IEs. Furthermore, γδ T cells represented the predominant source of IFNγ in PBMCs from naïve donors stimulated with P. falciparum IEs. The focus of Aim 2 was to investigate the ability of purified in vitro expanded γδ T cells to produce cytokines when exposed to P. falciparum IEs with different variant surface antigens. It was found that these cells can be directly activated by P. falciparum IEs. Furthermore, cytokine secretion was not substantially different in response to parasite lines expressing different PfEMP1 types. Moreover, the contribution of Vδ2+ γδ T cells to the production of IFNγ was significantly higher than that of Vδ2- γδ T cells. Nonetheless, the activation of Vδ2- γδ T cells represented an unanticipated and intriguing result in the present study. Examining the culture of Vδ2 depleted γδ T cells, a significant ability of them to produce cytokines (IFNγ, GMCSF and TNFα) was observed following exposure to P. falciparum IEs. Furthermore, activation of these cells by P. falciparum IEs for IFNγ production was highly dependent on the direct contact between the cells and the whole IEs. This activation was shown to be sensitive to trypsin digestion but not lack of expression of PfEMP1. Considering both complete and Vδ2 depleted γδ T cell cultures, it was found that the activation modes of γδ T cells subsets appeared to be different in presence or absence of Vδ2. Two different mechanisms of activation of Vδ1 and Vδ1-Vδ2- γδ T cell subsets in presence or absence of Vδ2 γδ T cells were also proposed in this study. The goal of Aim 3 was to assess the effect of various factors such as active malaria infection, life time malaria exposure and gravidity on the maternal innate immune responses. PBMCs derived from Papua New Guinea (PNG) (highly endemic area) pregnant women with and without current malaria infection and Melbourne pregnant women (non-endemic area) were exposed to P. falciparum CS2-IEs for 24 hours. The present study found that among PBMCs derived from PNG pregnant women, presence of microscopic malaria infection did not alter either secretion of IFNγ or proportion of innate immune cells positive for induction of IFNγ. With regard to malaria exposure, a significant increase in IFNγ production was observed in response to both P. falciparum CS2-IEs and Phytohaemagglutinin (PHA) in PNG samples compared to Melbourne samples. This observation was shown to be associated with significantly more active natural killer cells (NK cells) in pregnant women living in PNG. Considering the effect of gravidity, a significant elevation of IFNγ secretion in multigravidae group was observed compared to primigravidae group in PNG pregnant women (a similar, non-significant trend in Melbourne pregnant women) in response to P. falciparum CS2-IEs. This observation could be explained by the observed percentages of IFNγ producing γδ T cells and specially their Vδ2 subset being substantially higher in multigravidae women compared to primigravid women in PNG group. Together, these results suggested that the combination of exposure, not entirely specific to malaria, and gravidity significantly impacts innate immune response in pregnant women. The outcomes of these studies led to new insights that might contribute to development of new strategies in modulating the innate immune system and particularly to increasing proportions of IFNγ producing γδ T cells to safely prevent or diminish P. falciparum-induced immunopathology

Effects of interleukin-18 modulation on the pathogenesis of malaria infection

Malaria is an important parasitic infectious disease that afflicts mankind globally. The involvements of cytokines in the pathogenesis of malaria have well been documented and it has also been widely accepted that pro-inflammatory cytokines release plays crucial roles in the progression of severe pathology in malaria. Interleukin 18 (IL-18) is an important mediator which functions as an immune regulator and inducer of pro-inflammatory cytokines release. Activation of IL-18 in the immune system has been shown to amplify inflammatory responses in many disease conditions and may play a crucial role in the development of certain disease. This study is designed to determine the role and involvement of IL-18 during malaria infection and the effects of modulating its release on the course of the infection, the release of major pro- and anti-inflammatory cytokines and also the histopathological consequences in major affected organs during the infection. Male ICR mice infected with Plasmodium berghei (P. berghei) ANKA were used as malaria model in this study. Mice were injected intraperitoneally with 2 x 107 infected red blood cells. Plasma IL-18 concentrations in malaria-infected mice as measured by ELISA method, showed continuous increment from the beginning to the end of the infection. Release phase was found to be dependent on the level of severity of the infection. Modulation of the release of IL-18 was carried out by treating the malaria infected mice with recombinant mouse IL-18 (rmIL-18) and recombinant mouse IL-18 Fc chimera (rmIL-18 Fc chimera) intravenously. Inhibition of IL-18 release by rmIL-18 Fc chimera have delayed the emergence of the physical signs of infection and the development of parasitemia, subsequently prolonging the life span of mice infected with malaria. Augmentation of systemic IL-18 with rmIL-18 significantly decreased the release of anti-inflammatory cytokine (IL-10), whereas, inhibition of IL-18 with rmIL-18 Fc chimera showed increased level of IL-10. A significant elevation of pro-inflammatory cytokines (TNFα, IFNƴ, IL-1α and IL-6) was also observed during augmentation of IL-18 level. Nonetheless, these pro-inflammatory cytokines decreased during inhibition of IL-18 by rmIL-18 Fc chimera. From the pattern of cytokines release, it can be suggested that IL-18 exerts a pro-inflammatory activity in the Th1 type response by signaling the production of IFNƴ during malaria. Histopathological analysis performed on major organs known to be affected during malaria infection which include the brain, lungs, liver, spleen and kidneys of malarial mice showed significant histopathological changes in all organs of malarial mice. Treatment with rmIL-18 Fc chimera showed significant improvement on the histopathological conditions of the organs as compared to the malarial mice treated with PBS. However, mice treated with recombinant mouse IL-18 showed severe and worsening histopathology during the infection. In conclusion, the results from this study suggest that IL-18 may well play a crucial role in mediating the severity of malaria infection and it may play a key pro-inflammatory role throughout immune response against the disease. Antagonizing IL-18 activity has improved the histopathological conditions associated with the disease which may well suggest that targetting IL-18 would provide a potentially significant therapeutic benefit in malaria therapy

Innate immune responses to malaria-infected erythrocytes in pregnant women: Effects of gravidity, malaria infection, and geographic location.

BackgroundMalaria in pregnancy causes maternal, fetal and neonatal morbidity and mortality, and maternal innate immune responses are implicated in pathogenesis of these complications. The effects of malaria exposure and obstetric and demographic factors on the early maternal immune response are poorly understood.MethodsPeripheral blood mononuclear cell responses to Plasmodium falciparum-infected erythrocytes and phytohemagglutinin were compared between pregnant women from Papua New Guinea (malaria-exposed) with and without current malaria infection and from Australia (unexposed). Elicited levels of inflammatory cytokines at 48 h and 24 h (interferon γ, IFN-γ only) and the cellular sources of IFN-γ were analysed.ResultsAmong Papua New Guinean women, microscopic malaria at enrolment did not alter peripheral blood mononuclear cell responses. Compared to samples from Australia, cells from Papua New Guinean women secreted more inflammatory cytokines tumor necrosis factor-α, interleukin 1β, interleukin 6 and IFN-γ; pConclusionsGeographic location and, to some extent, gravidity influence maternal innate immunity to malaria

Interleukin-18 Antagonism Improved Histopathological Conditions of Malaria Infection in Mice

Background: Interleukin 18 (IL-18) exerts pleiotropic roles in many inflammatory-related diseases including parasitic infection. Previous studies have demonstrated the promising therapeutic potential of modulating IL-18 bioactivity in various pathologi­cal conditions. However, its involvement during malaria infection has yet to be established. In this study, we demonstrated the effect of modulating IL-18 on the histopathological conditions of malaria infected mice. Methods: Plasmodium berghei ANKA infection in male ICR mice was used as a model for malaria infection. Modulation of IL-18 release was carried out by treat­ment of malarial mice with recombinant mouse IL-18 (rmIL-18) and recombinant mouse IL-18 Fc chimera (rmIL-18Fc) intravenously. Histopathological study and analysis were performed on major organs including brain, liver, spleen, lungs and kidney. Results: Treatment with rmIL-18Fc resulted in significant improvements on the histopathological conditions of the organs in malaria-infected mice. Conclusion: IL-18 is an important mediator of malaria pathogenesis and targeting IL-18 could prove beneficial in malaria-infected host