ANKA Infection Research Articles

Interleukin-1b and Interferon-g are Associated with Malaria-Induced Hypoinsulinemic Hypoglycemia in Plasmodium berghei Anka-Infected Mice

Malaria-induced hypoglycemia is recognized as a serious complication of malaria and has one of the strongest associations with mortality in children. It has been speculated that oxidative stress and pro-inflammatory response during parasite infection were involved in its pathophysiology. Hence, this study aimed to investigate the development of malaria-induced hypoglycemia during Plasmodium berghei ANKA (PbANKA) infection with particular attention to the involvement of c-peptide, interleukin-1b (IL-1b), and interferon-g (IFN-g). ICR mice were infected with 1×107 parasitized erythrocytes of PbANKA, and parasitemia was monitored, and the development of hypoglycemia was assessed by measuring plasma glucose levels. The change of c-peptide level was evaluated. The pro-inflammatory response of IL-1b and IFN-g were also quantified in plasma. It was found that PbANKA infection resulted in hypoglycemia as indicated by a significantly (P < 0.05) decrease in plasma glucose levels on day 4 post-infection and associated with parasitemia. The c-peptide was slightly increased at day 2 post-infection, and then significantly (P < 0.05) decreased since day 4. Furthermore, we observed a significantly (P < 0.05) increased IL-1b, firstly responded, at day 2 post-infection followed by increasing the IFN-g level at day 4 in PbANKA-induced hypoglycemia. Our findings support the idea that hypoinsulinemic hypoglycemia in the PbANKA infected mice may be involved in the high IL-1b and IFN-g against the parasite infection.

Memory CD8+ T cells exhibit tissue imprinting and non-stable exposure-dependent reactivation characteristics following blood-stage Plasmodium berghei ANKA infections.

Experimental cerebral malaria (ECM) is a severe complication of Plasmodium berghei ANKA (PbA) infection in mice, characterized by CD8+ T‐cell accumulation within the brain. Whilst the dynamics of CD8+ T‐cell activation and migration during extant primary PbA infection have been extensively researched, the fate of the parasite‐specific CD8+ T cells upon resolution of ECM is not understood. In this study, we show that memory OT‐I cells persist systemically within the spleen, lung and brain following recovery from ECM after primary PbA‐OVA infection. Whereas memory OT‐I cells within the spleen and lung exhibited canonical central memory (Tcm) and effector memory (Tem) phenotypes, respectively, memory OT‐I cells within the brain post‐PbA‐OVA infection displayed an enriched CD69+CD103− profile and expressed low levels of T‐bet. OT‐I cells within the brain were excluded from short‐term intravascular antibody labelling but were targeted effectively by longer‐term systemically administered antibodies. Thus, the memory OT‐I cells were extravascular within the brain post‐ECM but were potentially not resident memory cells. Importantly, whilst memory OT‐I cells exhibited strong reactivation during secondary PbA‐OVA infection, preventing activation of new primary effector T cells, they had dampened reactivation during a fourth PbA‐OVA infection. Overall, our results demonstrate that memory CD8+ T cells are systemically distributed but exhibit a unique phenotype within the brain post‐ECM, and that their reactivation characteristics are shaped by infection history. Our results raise important questions regarding the role of distinct memory CD8+ T‐cell populations within the brain and other tissues during repeat Plasmodium infections.

Pathogenesis of Plasmodium berghei ANKA infection in the gerbil (Meriones unguiculatus) as an experimental model for severe malaria.

Background: As the quest to eradicate malaria continues, there remains a need to gain further understanding of the disease, particularly with regard to pathogenesis. This is facilitated, apart from in vitro and clinical studies, mainly via in vivo mouse model studies. However, there are few studies that have used gerbils (Meriones unguiculatus) as animal models. Thus, this study is aimed at characterizing the effects of Plasmodium berghei ANKA (PbA) infection in gerbils, as well as the underlying pathogenesis. Methods: Gerbils, 5-7 weeks old were infected by PbA via intraperitoneal injection of 1 × 106 (0.2 mL) infected red blood cells. Parasitemia, weight gain/loss, hemoglobin concentration, red blood cell count and body temperature changes in both control and infected groups were monitored over a duration of 13 days. RNA was extracted from the brain, spleen and whole blood to assess the immune response to PbA infection. Organs including the brain, spleen, heart, liver, kidneys and lungs were removed aseptically for histopathology. Results: Gerbils were susceptible to PbA infection, showing significant decreases in the hemoglobin concentration, RBC counts, body weights and body temperature, over the course of the infection. There were no neurological signs observed. Both pro-inflammatory (IFNγ and TNF) and anti-inflammatory (IL-10) cytokines were significantly elevated. Splenomegaly and hepatomegaly were also observed. PbA parasitized RBCs were observed in the organs, using routine light microscopy and in situ hybridization. Conclusion: Gerbils may serve as a good model for severe malaria to further understand its pathogenesis.

Late-stage systemic immune effectors inPlasmodium bergheiANKA infection: biopterin and oxidative stress

AbstractTo investigate the involvement of systemic oxidative stress in the pathogenesis of murine cerebral malaria, mice were infected with thePlasmodium berghei(P. berghei) ANKA 6653 strain. Serum tryptophan (Trp), kynurenine and urinary biopterin, liver, brain, spleen and serum superoxide dismutase (SOD), glutathione peroxidase (GPx), malondialdehyde (MDA) and nitrite and nitrate (NOx) levels were measured on day 7 post-inoculation. Our data showed a significant decrease in SOD and an increase in GPx activity and MDA level in all the examined biological materials (p<0.05), except spleen. Conversely, GPx activities in spleen were depleted, while SOD and MDA levels remained unchanged. Increased MDA levels might indicate increased peroxynitrite production, lipid peroxidation and oxidative stress. Also, elevated urinary biopterin, which was accompanied by increased NOx (p<0.05), may support the inhibition of Trp degradation (p>0.05). The excessive NO synthesis inP. bergheiinfection may be related to the up-regulation of inducible NO synthase, which was in accordance with the increased biopterin excretion. Thus, the large quantities of released toxic redox active radicals attack cell membranes and induce lipid peroxidation. AlthoughP. bergheiinfection did not demonstrate systemic Trp degradation and related indoleamine-2,3-dioxygenase activity, it may cause multi-organ failure and death, owing to host-derived severe oxidative stress.

Protective effects of Andrographis paniculata leaf extract on liver and renal damage and hypoglycemia during Plasmodium berghei infection

Liver and renal damage are some causes of deaths in malaria disease. Moreover, hypoglycemia and hypoglycemic shock during malaria infection have also been reported. Therefore, finding new plant extracts to have the activities to protect liver and renal damage as well as hypoglycemia during malaria infection is urgently needed. In this study was aimed to investigate the protective effects of Andrographis paniculata leaf extract on liver and renal damage as well as hypoglycemia induced by Plasmodium berghei ANKA (PbANKA) infection in mice. Aqueous crude extract of A. paniculata leaves was freshly prepared using hot water method. For efficacy test, standard 4-day suppressive test was used. ICR mice were inoculated with 1x107 parasitized erythrocytes of PbANKA by intraperitoneal infected, and given the extract (500, 1000, and 2000 mg/kg) orally by gavage for 4 consecutive days. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), albumin, blood urea nitrogen (BUN), creatinine, and glucose were measured. It was found that liver and renal damage were developed during malaria infection as indicated by markedly increasing of AST, ALT, BUN, and creatinine, and decreasing of albumin levels. Additionally, hypoglycemia was also found during the infection. Interestingly, A. paniculata extract showed protective effects on liver and renal damage, and presented anti-hypoglycemia in a dose-dependent manner against infected mice treated with this extract. The highest effect was found at dose of 2000 mg/kg. Moreover, no any side effects were observed in normal mice treated with the extract. It can be concluded that A. paniculata leaf extract can be used as alternative drug to protect liver and renal damage as well as hypoglycemia during malaria infection

Cross‐presentation of malaria antigen by brain microvessels: why CD8+ T cells are critical for the pathogenesis of experimental cerebral malaria

Cross‐presentation of malaria antigen by brain microvessels: why <scp>CD</scp>8⁺ T cells are critical for the pathogenesis of experimental cerebral malaria

The murine cerebral malaria phenomenon

P.berghei ANKA infection in CBA or CB57BL/6 mice is used widely as a murine ‘model’ of human cerebral malaria (HCM), despite markedly different histopathological features. The pathology of the murine model is characterised by marked inflammation with little or no intracerebral sequestration of parasitised erythrocytes, whereas HCM is associated with intense intracerebral sequestration, often with little inflammatory response. There are now more than ten times as many studies each year of the murine model than on HCM. Of 48 adjunctive interventions evaluated in the murine model, 44 (92%) were successful, compared with only 1 (6%) of 17 evaluated in HCM during the same period. The value of the mouse model in identifying pathological processes or therapeutic interventions in human cerebral malaria is questionable.

Plasmodium berghei ANKA infection causes brain damage in mice resistant to cerebral malaria

Severe malaria is a complex multisystem disorder includ-ing complications such as cerebral malaria, anemia, aci-dosis, jaundice, respiratory distress, renal insufficiency,coagulation anomalies and hyperparasitemia. We previ-ously characterized the experimental cerebral syndromeusing in vivo MRI and MRS techniques and proved thepreponderant role of edema in the fatal outcome of exper-imental cerebral malaria (CM) [1]. The purpose of the cur-rent study was to examine the cerebral effects ofPlasmodium berghei ANKA (PbA) infection in a mousestrain resistant to CM. We tested the hypothesis that PbAinfection could elicit brain injury, despite the absence ofexperimental CM, and by mechanisms different fromthose involved in CM.