Perforin mediated apoptosis of cerebral microvascular endothelial cells during experimental cerebral malaria

Cerebral malaria is a serious complication of Plasmodium falciparum infection. We have investigated the role of perforin in the pathogenesis of cerebral malaria in a murine model (Plasmodium berghei ANKA (PbA) infection). C57BL/6 mice demonstrated the typical neuropathological symptoms of experimental cerebral malaria infection from day 5p.i. and became moribund on day 6p.i. This pathology was not seen in PbA-infected, perforin-deficient (pfp-/-) mice. From days 5-6p.i. onwards there was a significant increase in mRNA for granzyme B and CD8, but not CD4, in brain tissue from PbA-infected C57BL/6 and pfp-/- mouse brains. Perforin mRNA was strongly increased in the brains of PbA-infected C57BL/6 mice on day 6p.i. Immunohistochemistry revealed increased perforin staining and elevated numbers of CD8(+) cells within the cerebral microvessels in PbA-infected C57BL/6 at days 5 and 6p.i. compared with uninfected animals. At day 6p.i., there were TUNEL-positive cells and activated caspase-3 positive cells of endothelial morphology in the CNS of PbA-infected C57BL/6 mice. The TUNEL-positive cells were greatly reduced in pfp-/- mice. These results suggest that CD8(+)T lymphocytes induce apoptosis of endothelial cells via a perforin-dependent process, contributing to the fatal pathogenic process in murine cerebral malaria.     

Regulatory CD4+ CD25+ Foxp3+ T cells expand during experimental Plasmodium infection but do not prevent cerebral malaria

Pathogenic CD8+ T cells are implicated in the physiopathological mechanisms leading to experimental cerebral malaria (CM) in Plasmodium berghei ANKA (PbA) infected mice. Therefore, we hypothesised that in CM susceptible mice the neuropathology could be, at least in part, the result of an inefficient control of pathogenic effector T cells by CD4+ CD25+ Treg cells. Remarkably, the number of CD4+ CD25high T cells expressing Foxp3 increased in the spleen during the course of infection. These cells displayed an activated phenotype and consistent with that, CD4+ CD25high Treg cells isolated from PbA-infected mice showed an enhanced regulatory activity in vitro. Surprisingly, these cells do not migrate to the brain at the time of neurological symptoms as the conventional CD4+ T cells do. CM was not exacerbated in anti-CD25 treated mice when infected with PbA one month after treatment, even if splenic CD8+ T cells expressing CD69 increased in these mice. Taken together, these results show that P. berghei infection leads to an increase of the number of splenic CD4+ CD25high Treg cells exhibiting in vitro suppressive function, but they do not seem to be involved in vivo in the protection against CM.     

Cognitive Dysfunction Is Sustained after Rescue Therapy in Experimental Cerebral Malaria,and Is Reduced by Additive Antioxidant Therapy

Neurological impairments are frequently detected in children surviving cerebral malaria (CM), the most severe neurological complication of infection with Plasmodium falciparum. The pathophysiology and therapy of long lasting cognitive deficits in malaria patients after treatment of the parasitic disease is a critical area of investigation. In the present study we used several models of experimental malaria with differential features to investigate persistent cognitive damage after rescue treatment. Infection of C57BL/6 and Swiss (SW) mice with Plasmodium berghei ANKA (PbA) or a lethal strain of Plasmodium yoelii XL (PyXL), respectively, resulted in documented CM and sustained persistent cognitive damage detected by a battery of behavioral tests after cure of the acute parasitic disease with chloroquine therapy. Strikingly, cognitive impairment was still present 30 days after the initial infection. In contrast, BALB/c mice infected with PbA, C57BL6 infected with Plasmodium chabaudi chabaudi and SW infected with non lethal Plasmodium yoelii NXL (PyNXL) did not develop signs of CM, were cured of the acute parasitic infection by chloroquine, and showed no persistent cognitive impairment. Reactive oxygen species have been reported to mediate neurological injury in CM. Increased production of malondialdehyde (MDA) and conjugated dienes was detected in the brains of PbA-infected C57BL/6 mice with CM, indicating high oxidative stress. Treatment of PbA-infected C57BL/6 mice with additive antioxidants together with chloroquine at the first signs of CM prevented the development of persistent cognitive damage. These studies provide new insights into the natural history of cognitive dysfunction after rescue therapy for CM that may have clinical relevance, and may also be relevant to cerebral sequelae of sepsis and other disorders.     

CD8+ T cells and IFN-γ mediate the time-dependent accumulation of infected red blood cells in deep organs during experimental cerebral malaria

Background

Infection with Plasmodium berghei ANKA (PbA) in susceptible mice induces a syndrome called experimental cerebral malaria (ECM) with severe pathologies occurring in various mouse organs. Immune mediators such as T cells or cytokines have been implicated in the pathogenesis of ECM. Red blood cells infected with PbA parasites have been shown to accumulate in the brain and other tissues during infection. This accumulation is thought to be involved in PbA–induced pathologies, which mechanisms are poorly understood.

Methods and Findings

Using transgenic PbA parasites expressing the luciferase protein, we have assessed by real-time in vivo imaging the dynamic and temporal contribution of different immune factors in infected red blood cell (IRBC) accumulation and distribution in different organs during PbA infection. Using deficient mice or depleting antibodies, we observed that CD8⁺ T cells and IFN-γ drive the rapid increase in total parasite biomass and accumulation of IRBC in the brain and in different organs 6–12 days post-infection, at a time when mice develop ECM. Other cells types like CD4⁺ T cells, monocytes or neutrophils or cytokines such as IL-12 and TNF-α did not influence the early increase of total parasite biomass and IRBC accumulation in different organs.

Conclusions

CD8⁺ T cells and IFN-γ are the major immune mediators controlling the time-dependent accumulation of P. berghei-infected red blood cells in tissues.     

Induction of pro-inflammatory mediators in Plasmodium berghei infected BALB/c mice breaks blood-brain-barrier and leads to cerebral malaria in an IL-12 dependent manner

A severe complication of Plasmodium infection is cerebral malaria, a condition mainly attributed to overwhelming inflammatory immune reactions of the host. Murine models differing in susceptibility to experimental cerebral malaria (ECM) allow detailed studies of the host response. We show that ECM- resistant BALB/c mice were driven into interferon gamma- and IL-12-dependent ECM and subsequent death if they received CpG-oligonucleotides after Plasmodium berghei ANKA (PbA) infection. CpG application triggered production of pro-inflammatory cytokines systemically as well in spleen and brain and induced neuropathological symptoms, leading to increased mortality. Experiments with genetically deficient mice confirmed the role of IFN-γ and IL-12 during CpG-triggered immunopathology. Furthermore, the application of CpG and downstream production of pro-inflammatory cytokines contributed to the break down of the blood brain barrier visualized by Evan's Blue, comparable to PbA-infected C57BL/6 mice. Taken together, resistance of BALB/c mice towards ECM development could be altered through induction of pro-inflammatory cytokines by CpG. Therefore, approaches discussed earlier to induce pro-inflammatory immune reactions for malaria protection should be considered with caution.     

Role of ICAM-1 (CD54) in the development of murine cerebral malaria

In susceptible mouse strains, infection of mice with Plasmodium berghei ANKA (PbA) results in a lethal complication, cerebral malaria. Cerebral malaria is due to the immune response induced by the parasite, which results in an increased production of TNF, known to increase the expression of adhesion molecules on the endothelia. To investigate the role of the adhesion molecule ICAM-1 (CD54), we infected wild-type (+/+) and ICAM-1-deficient (-/-) mice with PbA. While +/+ mice died 6-8 days after infection, -/- mice survived > 15 days. Parasitaemia was similar in +/+ and -/- mice. Serum TNF concentration was increased by the infection and was significantly higher in infected +/+ than in -/- mice. However, TNF mRNA levels in spleen, lungs, and brain were elevated in both infected +/+ and -/- mice. For IFN-gamma, serum levels were similar in both groups. A breakdown of the blood-brain barrier was evident in infected +/+ mice only. Interestingly, thrombocytopenia was profound in infected +/+, but practically absent in -/- mice. Moreover, macrophage sequestration was evident in brain venules and lung capillaries of +/+ mice and was significantly less important in the alveolar capillaries of infected -/- mice. In contrast, neutrophil sequestration in the lung was similar in both +/+ and -/- mice. Sequestration of parasitized red blood cells was significantly greater in the alveolar capillaries from +/+ than -/- mice. These results indicate that while the immune response is similar in both +/+ and ICAM-1(-/-) mice, the absence of mortality in ICAM(-/-) mice correlates with a decrease of macrophage and parasitized RBC trapping and a less severe thrombocytopenia.     

CpG oligodeoxynucleotide induction of antiviral effector molecules in sheep

Immunostimulatory CpG oligodeoxynucleotide (ODN) can protect mice against infection by many pathogens but the mechanisms mediating disease protection are not well defined. Furthermore, the mechanisms of CpG ODN induced disease protection in vivo have not been investigated in other species. We investigated the induction of antiviral effector molecules in sheep treated with a class B CpG ODN (2007). Subcutaneous injection of ODN 2007 induced a dose-dependent increase in serum levels of the antiviral effector molecule, 2'5'-A synthetase. Peak levels of enzyme were observed 4 days following ODN injection and enzyme levels remained elevated for the following 3-5 days. Repeated ODN injections induced a more sustained elevation of serum 2'5'-A synthetase activity. Finally, formulation of ODN 2007 in emulsigen increased the level of serum 2'5'-A synthetase activity and this response was CpG-specific. Elevated serum 2'5'-A synthetase activity suggested that CpG ODN acted through the induction of either interferon (IFN)-alpha or IFN-gamma. ODN 2007 did not induce detectable levels of IFN-alpha or IFN-gamma when incubated with peripheral blood mononuclear cells, but both IFN-alpha and IFN-gamma were detected following stimulation of lymph node cells with ODN 2007. CpG ODN induction of 2'5'-A synthetase in vitro correlated with the secretion of both IFN-alpha and IFN-gamma. Furthermore, immunohistochemical staining of skin revealed a marked cellular infiltration at the site of ODN 2007 injection. This cellular infiltration was CpG-specific and consisted of primarily CD172(+) myeloid cells. Many of the cells recruited to the site of ODN 2007 injection expressed IFN-alpha and some IFN-gamma. These observations support the conclusion that localized cell recruitment and activation contribute to CpG ODN induction of antiviral effector molecules, such as interferon and 2'5'-A synthetase.     

Clonal derivatives of the RD-114 cell line differ in their antiviral and gene-inducing responses to interferons.

The human rhabdomyosarcoma cell line RD-114 is partially responsive to interferons (IFNs). In these cells, alpha interferon (IFN-alpha) or gamma interferon (IFN-gamma) inhibits the replication of some viruses but not of others. Similarly, some of the IFN-inducible mRNAs are induced poorly, whereas others are induced well. Here we report the isolation of clonal derivatives of this line which display different spectra of responses to IFNs. Among the eight extensively characterized clonal lines, one, C10, did not respond to IFN-alpha or IFN-gamma at all. Retrovirus production by each of the seven other lines was inhibited by both IFN-alpha and IFN-gamma. Replication of vesicular stomatitis virus was inhibited strongly by IFN-alpha in clone B1 but not in others, whereas it was not appreciably affected by IFN-gamma in any clone. Replication of encephalomyocarditis virus was inhibited strongly by IFN-gamma in clones A1, A2, A3, B3, and B8 and by IFN-alpha in clone A2. Neither IFN inhibited the multiplication of these clones greatly, although their doubling times were slightly increased. Five mRNAs were induced by IFNs to varying degrees in the seven clones. mRNA 2A was most strongly induced by IFN-gamma in clone A3. mRNA 1-8 was strongly induced by IFN-alpha in clone A1 and by either IFN in clones A2 and A3. The highest concentrations of 2',5'-oligoadenylate synthetase mRNA, mRNA 561, and mRNA 6-16 were in IFN-alpha-treated clones A1 and A2. These results demonstrated the existence of clonal heterogeneity in IFN responses in a cell line and strengthened the view that IFN treatment of cells generates multiple signals leading to a variety of IFN-induced phenotypes.     

IL-33-Mediated Protection against Experimental Cerebral Malaria Is Linked to Induction of Type 2 Innate Lymphoid Cells,M2 Macrophages and Regulatory T Cells

Cerebral malaria (CM) is a complex parasitic disease caused by Plasmodium sp. Failure to establish an appropriate balance between pro- and anti-inflammatory immune responses is believed to contribute to the development of cerebral pathology. Using the blood-stage PbA (Plasmodium berghei ANKA) model of infection, we show here that administration of the pro-Th2 cytokine, IL-33, prevents the development of experimental cerebral malaria (ECM) in C57BL/6 mice and reduces the production of inflammatory mediators IFN-γ, IL-12 and TNF-α. IL-33 drives the expansion of type-2 innate lymphoid cells (ILC2) that produce Type-2 cytokines (IL-4, IL-5 and IL-13), leading to the polarization of the anti-inflammatory M2 macrophages, which in turn expand Foxp3 regulatory T cells (Tregs). PbA-infected mice adoptively transferred with ILC2 have elevated frequency of M2 and Tregs and are protected from ECM. Importantly, IL-33-treated mice deleted of Tregs (DEREG mice) are no longer able to resist ECM. Our data therefore provide evidence that IL-33 can prevent the development of ECM by orchestrating a protective immune response via ILC2, M2 macrophages and Tregs.     

Experimental Cerebral Malaria Pathogenesis—Hemodynamics at the Blood Brain Barrier

Cerebral malaria claims the lives of over 600,000 African children every year. To better understand the pathogenesis of this devastating disease, we compared the cellular dynamics in the cortical microvasculature between two infection models, Plasmodium berghei ANKA (PbA) infected CBA/CaJ mice, which develop experimental cerebral malaria (ECM), and P. yoelii 17XL (PyXL) infected mice, which succumb to malarial hyperparasitemia without neurological impairment. Using a combination of intravital imaging and flow cytometry, we show that significantly more CD8+ T cells, neutrophils, and macrophages are recruited to postcapillary venules during ECM compared to hyperparasitemia. ECM correlated with ICAM-1 upregulation on macrophages, while vascular endothelia upregulated ICAM-1 during ECM and hyperparasitemia. The arrest of large numbers of leukocytes in postcapillary and larger venules caused microrheological alterations that significantly restricted the venous blood flow. Treatment with FTY720, which inhibits vascular leakage, neurological signs, and death from ECM, prevented the recruitment of a subpopulation of CD45^hi CD8+ T cells, ICAM-1+ macrophages, and neutrophils to postcapillary venules. FTY720 had no effect on the ECM-associated expression of the pattern recognition receptor CD14 in postcapillary venules suggesting that endothelial activation is insufficient to cause vascular pathology. Expression of the endothelial tight junction proteins claudin-5, occludin, and ZO-1 in the cerebral cortex and cerebellum of PbA-infected mice with ECM was unaltered compared to FTY720-treated PbA-infected mice or PyXL-infected mice with hyperparasitemia. Thus, blood brain barrier opening does not involve endothelial injury and is likely reversible, consistent with the rapid recovery of many patients with CM. We conclude that the ECM-associated recruitment of large numbers of activated leukocytes, in particular CD8+ T cells and ICAM+ macrophages, causes a severe restriction in the venous blood efflux from the brain, which exacerbates the vasogenic edema and increases the intracranial pressure. Thus, death from ECM could potentially occur as a consequence of intracranial hypertension.     

In vivo and in vitro regulation of type I IFN synthesis by synergistic effects of CD40 and type II IFN

During cognate interaction with CD40 ligand (CD154)-expressing T cells, Ag-presenting accessory cells are activated for increased cytokine synthetic and costimulatory function. We examined whether CD40 modulates in vivo innate immune function over time, hypothesizing that distinct cytokine responses evolve to delayed microbial exposure. C3H/HeN mice pretreated with activating anti-CD40 Ab (FGK45) produced 10-fold more serum IFN-gamma and IL-12 p70 to delayed, but not synchronous, challenge with LPS. A novel finding was that LPS-induced IFN-alpha increased by 20-fold in mice pretreated for 24 h, but not 6 h or less, with anti-CD40. Anti-CD40-pretreated C57BL/6 RAG-2(-/-) mice similarly increased IFN-alpha responses to delayed LPS challenge, confirming mediation by innate immunity. Type I IFNR- and IFN-gamma-deficient mice treated with anti-CD40 failed to expand serum IFN-alpha responses to LPS challenge. Combined pretreatment with anti-CD40 and anti-IFN-gamma mAb showed that IFN-gamma produced after anti-CD40 pretreatment, but before LPS challenge, was necessary for IFN-alpha synthetic enhancement. Anti-CD40 also increased polyinosinic-polycytidylic acid (poly(I:C))-inducible IFN-alpha by 5-fold in an IFN-gamma-dependent fashion, but did not significantly increase IFN-alpha production to CpG or Pam(3)Cys challenges. Poly(IC)-stimulated splenocytes from anti-CD40-pretreated mice produced 4-fold more IFN-alpha than controls and production associated with CD11c(+) cells. Finally, rIFN-gamma and anti-CD40 combined synergistically to increase poly(IC)-inducible IFN-alpha synthetic capacity in bone marrow dendritic cells. We conclude that innate immune production of IFN-alpha is cooperatively regulated by CD40 and IFN-gamma acting on dendritic cells, suggesting a unique mechanism by which innate immune function evolves in response to specific adaptive immune signals.     

Alternative induction of alpha/beta interferons and gamma interferon by listeria monocytogenes in mouse spleen cell cultures

Production of interferon (IFN) by Listeria monocytogenes (LM) in nonimmunized mouse spleen cell cultures was studied. IFN-gamma defined by virtue of its acid stability and antigenicity was produced in spleen cell cultures obtained from ddY mice, C57BL/6 mice, and BALB/c mice in response to heat-killed (HK) LM within 24 hr. On the other hand, production of IFN-alpha/beta was demonstrated in spleen cell cultures obtained from one of four nude mice (BALB/c, nu/nu). Therefore, it is important to know the reason why the spleen cells of mice other than nude mice did produce only IFN-gamma, but did not produce IFN-alpha/beta in response to HK-LM. Spleen cells obtained from ddY mice were fractionated, and the cellular source for IFN production of either IFN-alpha/beta or IFN-gamma induced by HK-LM was investigated. IFN-gamma was produced only by a mixture of T lymphocytes (nylon wool-nonadherent, Thy-1-positive cells) and macrophages by HK-LM. Neither T lymphocytes nor macrophages alone produced IFN by HK-LM. Macrophage-depleted spleen cells produced neither IFN-gamma nor IFN-alpha/beta, but these cells acquired the ability to produce IFN-alpha/beta, not IFN-gamma, only when they had been treated with IFN-alpha/beta. A possible mechanism of both IFN-gamma and IFN-alpha/beta induction by Listeria in mouse spleen cell cultures is discussed.     

Pegylated alpha interferon is an effective treatment for virulent venezuelan equine encephalitis virus and has profound effects on the host immune response to infection

Venezuelan equine encephalitis virus (VEEV) is a highly infectious alphavirus endemic in parts of Central and South America. The disease is transmitted by mosquitoes, and the natural reservoir is the small rodent population, with epidemics occurring in horses and occasionally humans. Following infection, VEEV replicates in lymphoid tissues prior to invasion of the central nervous system. Treatment of VEEV-infected BALB/c mice with polyethylene glycol-conjugated alpha interferon (PEG IFN-alpha) results in a greatly enhanced survival from either a subcutaneous or an aerosol infection. Virus is undetectable within PEG IFN-alpha-treated individuals by day 30 postinfection (p.i.). Treatment results in a number of changes to the immune response characteristics normally associated with VEEV infection. Increased macrophage activation occurs in PEG IFN-alpha-treated BALB/c mice infected with VEEV. The rapid activation of splenic CD4, CD8, and B cells by day 2 p.i. normally associated with VEEV infection is absent in PEG IFN-alpha-treated mice. The high tumor necrosis factor alpha production by macrophages from untreated mice is greatly diminished in PEG IFN-alpha-treated mice. These results suggest key immunological mechanisms targeted by this lethal alphavirus that can be modulated by prolonged exposure to IFN-alpha.     

Induction of antibody-dependent cellular cytotoxicity in vivo by IFN-alpha and its antitumor efficacy against established B16 melanoma liver metastases when combined with specific anti-B16 monoclonal antibody

We have previously shown the ability of different cytokines to induce antibody-dependent cellular cytotoxicity (ADCC) in murine cells in vitro. In addition we found that the administration to mice of IL-2-induced cells which mediated ADCC and that these cells were phenotypically similar to the cells induced in vitro. In the present study we tested the ability of various cytokines, including IL-1, TNF, IFN-alpha, and IFN-gamma to induce ADCC in vivo. We found that both IFN-alpha and IFN-gamma induced ADCC in the livers and spleens of C3H/Hen-treated mice and that these cytokines together with TNF enhanced the IL-2-induced ADCC in vivo. In C57BL/6 mice which, as previously shown, exhibit relatively low ADCC activity, IFN-alpha and IFN-gamma increased the IL-2-induced ADCC only when 100,000 U of IL-2 were used for priming. The effect of IFN-alpha on ADCC was dose dependent and was optimal after the administration of 200,000 U of the cytokine given three times a day for 3 days. Similar to the cells induced in vivo by IL-2, the precursors of the cells mediating ADCC were asialo GM1+ whereas the effectors were mainly nonadherent, Thy-1+ cells. IFN-alpha-generated cells mediating ADCC in the liver and spleen and, when combined with IL-2, ADCC was induced in the thymus as well. This effect of IFN-alpha on the induction of ADCC was exploited in an immunotherapy model in which we found that IFN-alpha significantly enhanced the antibody-mediated antitumor effect on established B16 melanoma liver micrometastases. Furthermore, when IL-2 and IFN-alpha administration was combined with the administration of mAb, a significantly reduced number of established 6- to 8-day B16 melanoma liver macrometastases and prolonged survival of tumor-bearing mice were seen. These studies imply that the administration of appropriate cytokine combinations may be a useful adjunct to the administration of mAb for the treatment of cancer in humans.     

The significance of alpha/beta interferons and gamma interferon produced in mice infected with Listeria monocytogenes

Interferon (IFN)-alpha/beta was induced in the circulation of mice infected intravenously with Listeria monocytogenes 24 to 72 hr after infection, but was not induced by the administration of heat-killed Listeria, listerial cell wall fraction (LCWF), or listerial soluble fraction. Appearance of IFN-alpha/beta showed a pattern similar to that of the growth of bacteria in the spleen and the liver of mice. IFN-alpha/beta production was abrogated by pretreatment of mice with anti-asialo GM1 antibody, antithymocyte serum, or hydrocortisone, but not with cyclophosphamide or carrageenan. Such treatments which suppressed IFN-alpha/beta production did not influence bacterial growth in the organs of mice in the early stage of Listeria infection. Administration of IFN-alpha/beta exogenously also did not. After 5 days of infection when the specific resistance against reinfection with Listeria was established, IFN-gamma but not IFN-alpha/beta was induced in the circulation 3 to 6 hr after stimulation with LCWF or reinfection with Listeria. IFN-gamma production was abrogated completely by cyclophosphamide and antithymocyte serum, and partially by hydrocortisone and carrageenan, but not by anti-asialo GM1 antibody in Listeria-infected mice treated with these agents before induction of IFN-gamma by LCWF. Presumably, IFN-alpha/beta might be produced by asialo GM1-bearing cells but IFN-gamma might not. However, IFN-gamma production was suppressed in Listeria-infected mice, when IFN-alpha/beta production had been inhibited by treatment with anti-asialo GM1 antibody or when the IFN produced had been neutralized with anti-mouse IFN-alpha/beta antibody. Therefore, it is conceivable that IFN-alpha/beta might be essential for the generation or the expression of antigen-specific T cells involving IFN-gamma production and acquired resistance during Listeria infection. In fact, the bacterial growth in the organs of mice in the early stage of infection was normal in IFN-alpha/beta-depleted mice but it resulted in the delay of T-cell-dependent elimination of bacteria from the organs of mice in the late stage.     

Coincident parasite and CD8 T cell sequestration is required for development of experimental cerebral malaria

Cerebral malaria (CM) is a fatal complication of Plasmodium falciparum infection. Using a well defined murine model, we observed the effect on disease outcome of temporarily reducing parasite burden by anti-malarial drug treatment. The anti-malarial treatment regime chosen decreased parasitaemia but did not cure the mice, allowing recrudescence of parasites. These mice were protected against CM, despite their parasitaemia having increased, following treatment cessation, to levels surpassing that associated with CM in mice not treated with the drug. The protection was associated with reduced levels of cytokines, chemokines, CD8⁺ T cells and parasites in the brain. The results suggest that the development of the immunopathological response that causes CM depends on a continuous stimulus provided by parasitised red blood cells, either circulating or sequestered in small vessels.     

Oral artesunate prevents Plasmodium berghei Anka infection in mice

Artesunate, a semi-synthetic derivative of a naturally occurring anti-malarial artemisinin was compared with chloroquine in C57BL/6 mice infected with Plasmodium berghei Anka (PbA). A 7-day oral administration of artesunate prevented parasitaemia at 10 mg/kg/day. However, recrudescence of parasitaemia and cerebral malaria occurred upon cessation of treatment followed by death within 28 days. However, a 14-day course of artesunate (100 mg/kg/day) prevented completely the development of parasitaemia and cerebral malaria with a survival of more than 60-days as did 10 mg/kg/day chloroquine. These data demonstrate that oral artesunate inhibits PbA and prevents cerebral malaria, but needs to be administered at high dose and for prolonged time to eradicate PbA infection in mice.