Morphological characteristics of intracerebral arterioles in clinical (Plasmodium falciparum) and experimental (Plasmodium berghei) cerebral malaria

Clinical Comparison of Retinopathy-Positive and Retinopathy-Negative Cerebral Malaria

AbstractCerebral malaria (CM) is a severe and often lethal complication of falciparum malaria. A classic malaria retinopathy is seen in some (retinopathy-positive [RP]) children but not others (retinopathy-negative [RN]), and is associated with increased parasite sequestration. It is unclear whether RN CM is a severe nonmalarial illness with incidental parasitemia or a less severe form of the same malarial illness as RP CM. Understanding the clinical differences between RP and RN CM may help shed light on the pathophysiology of malarial retinopathy. We compared clinical history, physical examination, laboratory findings, and outcomes of RP (N = 167) and RN (N = 87) children admitted to Mulago Hospital, Kampala, Uganda. Compared with RN children, RP children presented with a longer history of illness, as well as physical examination and laboratory findings indicative of more severe disease and organ damage. The hospital course of RP children was complicated by longer coma duration and a greater transfusion burden than RN children. Mortality did not differ significantly between RP and RN children (14.4% versus 8.0%, P = 0.14). Further, severity of retinal hemorrhage correlated with the majority of variables that differed between RP and RN children. The data suggest that RP and RN CM may reflect the spectrum of illness in CM, and that RN CM could be an earlier, less severe form of disease.

The evidence for a role of vasospasm in the pathogenesis of cerebral malaria

Due to delay in treatment, cerebral malaria (CM) remains a significant complication of Plasmodium falciparum infection and is a common cause of death from malaria. In addition, more than 10 % of children surviving CM have neurological and long-term cognitive deficits. Understanding the pathogenesis of CM enables design of supportive treatment, reducing neurological morbidity and mortality. Vaso-occlusion and brain swelling appear to be leading to clinical features, neuronal damage and death in CM. It is proposed that parasitized red blood cells (pRBC), due to cytoadhesion to the endothelium and vasospasm induced by reduced bioavailability of nitric oxide, are causes. Stasis of blood flow and accumulation of pRBC may allow, after schizont rupture, for high concentration of products of haemolysis to accumulate, which leads to localized nitric oxide depletion, inducing adhesion molecules and cerebral vasospasm. Features consistent with an involvement of vasospasm are rapid reversibility of neurological symptoms, intermittently increased or absent flow in medium cerebral artery detectable on Doppler ultrasound and hemispheric reversible changes on cerebral magnetic resonance imaging in some patients. Clinical trials of treatment that can rapidly reduce cerebral vasospasm, including nitric oxide donors, inhaled nitric oxide, endothelin or calcium antagonists, or tissue plasminogen activators, are warranted.

Vascular dysfunction as a target for adjuvant therapy in cerebral malaria

Cerebral malaria (CM) is a life-threatening complication of Plasmodium falciparum malaria that continues to be a major global health problem. Brain vascular dysfunction is a main factor underlying the pathogenesis of CM and can be a target for the development of adjuvant therapies for the disease. Vascular occlusion by parasitised red blood cells and vasoconstriction/vascular dysfunction results in impaired cerebral blood flow, ischaemia, hypoxia, acidosis and death. In this review, we discuss the mechanisms of vascular dysfunction in CM and the roles of low nitric oxide bioavailability, high levels of endothelin-1 and dysfunction of the angiopoietin-Tie2 axis. We also discuss the usefulness and relevance of the murine experimental model of CM by Plasmodium berghei ANKA to identify mechanisms of disease and to screen potential therapeutic interventions.

Vasospasm in cerebral inflammation

All forms of cerebral inflammation as found in bacterial meningitis, cerebral malaria, brain injury, and subarachnoid haemorrhage have been associated with vasospasm of cerebral arteries and arterioles. Vasospasm has been associated with permanent neurological deficits and death in subarachnoid haemorrhage and bacterial meningitis. Increased levels of interleukin-1 may be involved in vasospasm through calcium dependent and independent activation of the myosin light chain kinase and release of the vasoconstrictor endothelin-1. Another key factor in the pathogenesis of cerebral arterial vasospasm may be the reduced bioavailability of the vasodilator nitric oxide. Therapeutic trials in vasospasm related to inflammation in subarachnoid haemorrhage in humans showed a reduction of vasospasm through calcium antagonists, endothelin receptor antagonists, statins, and plasminogen activators. Combination of therapeutic modalities addressing calcium dependent and independent vasospasm, the underlying inflammation, and depletion of nitric oxide simultaneously merit further study in all conditions with cerebral inflammation in double blind randomised placebo controlled trials. Auxiliary treatment with these agents may be able to reduce ischemic brain injury associated with neurological deficits and increased mortality.

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.

Host susceptibility to malaria in human and mice: compatible approaches to identify potential resistant genes

There is growing evidence for human genetic factors controlling the outcome of malaria infection, while molecular basis of this genetic control is still poorly understood. Case-control and family-based studies have been carried out to identify genes underlying host susceptibility to malarial infection. Parasitemia and mild malaria have been genetically linked to human chromosomes 5q31-q33 and 6p21.3, and several immune genes located within those regions have been associated with malaria-related phenotypes. Association and linkage studies of resistance to malaria are not easy to carry out in human populations, because of the difficulty in surveying a significant number of families. Murine models have proven to be an excellent genetic tool for studying host response to malaria; their use allowed mapping 14 resistance loci, eight of them controlling parasitic levels and six controlling cerebral malaria. Once quantitative trait loci or genes have been identified, the human ortholog may then be identified. Comparative mapping studies showed that a couple of human and mouse might share similar genetically controlled mechanisms of resistance. In this way, char8, which controls parasitemia, was mapped on chromosome 11; char8 corresponds to human chromosome 5q31-q33 and contains immune genes, such as Il3, Il4, Il5, Il12b, Il13, Irf1, and Csf2. Nevertheless, part of the genetic factors controlling malaria traits might differ in both hosts because of specific host-pathogen interactions. Finally, novel genetic tools including animal models were recently developed and will offer new opportunities for identifying genetic factors underlying host phenotypic response to malaria, which will help in better therapeutic strategies including vaccine and drug development.

Transdermal glyceryl trinitrate as an effective adjunctive treatment with artemether for late-stage experimental cerebral malaria

Cerebral malaria (CM) is associated with low nitric oxide (NO) bioavailability, cerebrovascular constriction, occlusion, and hypoperfusion. Administration of exogenous NO partially prevents the neurological syndrome and associated vascular pathology in an experimental CM (ECM) mouse model. In this study, we evaluated the effects of transdermal glyceryl trinitrate in preventing ECM and, in combination with artemether, rescuing late-stage ECM mice from mortality. The glyceryl trinitrate and/or artemether effect on survival and clinical recovery was evaluated in C57BL/6 mice infected with P. berghei ANKA. NO synthase (NOS) expression in mouse brain was determined by Western blots. Mean arterial pressure (MAP) and pial arteriolar diameter were monitored using a tail-cuff blood pressure system and a cranial window preparation, respectively. Preventative administration of glyceryl trinitrate at 0.025 mg/h decreased ECM mortality from 67 to 11% and downregulated inducible NOS expression in the brain. When administered as adjunctive rescue therapy with artemether, glyceryl trinitrate increased survival from 47 to 79%. The adjunctive therapy caused a sustained reversal of pial arteriolar vasoconstriction in ECM mice, an effect not observed with artemether alone. Glyceryl trinitrate induced a 13% decrease in MAP in uninfected mice but did not further affect MAP in hypotensive ECM mice. Glyceryl trinitrate, when combined with artemether, was an effective adjunctive rescue treatment for ECM. This treatment ameliorated pial arteriolar vasospasm and did not significantly affect MAP. These results indicate that transdermal glyceryl trinitrate has potential to be considered as a candidate for adjunctive therapy for CM.

Expression of Tim-1 and Tim-3 in Plasmodium berghei ANKA infection

Cerebral malaria (CM) is a serious and often fatal complication of Plasmodium falciparum infections; however, the precise mechanisms leading to CM is poorly understood. Mouse malaria models have provided insight into the key events in pathogenesis of CM. T-cell immune response is known to play an important role in malaria infection, and members of the T-cell immunoglobulin- and mucin-domain-containing molecule (Tim) family have roles in T-cell-mediated immune responses. Tim-1 and Tim-3 are expressed on terminally differentiated Th2 and Th1 cells, respectively, and participate in the regulation of Th immune response. Until now, the role of Tim family proteins in Plasmodium infection remains unclear. In the present study, the mRNA levels of Tim-1, Tim-3, and some key Th1 and Th2 cytokines in the spleen of Kunming outbred mice infected with Plasmodium berghei ANKA (PbANKA) were determined using real-time polymerase chain reaction (qRT-PCR). Compared with uninfected controls, Tim-1 expression was significantly decreased in infected mice with CM at day 10 postinfection (p.i.) but significantly increased in infected mice with non-CM at day 22 p.i.; in contrast, Tim-3 expression was significantly increased in infected mice both with CM at day 10 p.i. and with non-CM at day 22 p.i. The expressions of IFN-γ, TNF-α, IL-10, and IL-12 were significantly increased but IL-4 was significantly decreased in infected mice with CM at days 10 p.i., whereas the expressions of IFN-γ, TNF-α, IL-4, IL-10, and TGF-β were significantly increased but IL-12 was significantly decreased in infected mice with non-CM at days 22 p.i. Furthermore, the expression of Tim-1 and Tim-3 could reflect Th2 and Th1 immune response in the spleen of PbANKA-infected mice, respectively. Our data suggest that PbANKA infection could inhibit the differentiation of T lymphocytes toward Th2 cells, promote the Th1 cell differentiation, and induce Th1-biased immune response in the early infective stage, whereas the infection could promote Th2 cell differentiation and induce Th2-biased immune response in the late infective stage. Our data indicate that both Tim-1 and Tim-3 may play a role in the process of PbANKA infection, which may represent a potential therapeutic target.

Neuroimmunological blood brain barrier opening in experimental cerebral malaria

Plasmodium falciparum malaria is responsible for nearly one million annual deaths worldwide. Because of the difficulty in monitoring the pathogenesis of cerebral malaria in humans, we conducted a study in various mouse models to better understand disease progression in experimental cerebral malaria (ECM). We compared the effect on the integrity of the blood brain barrier (BBB) and the histopathology of the brain of P. berghei ANKA, a known ECM model, P. berghei NK65, generally thought not to induce ECM, P. yoelii 17XL, originally reported to induce human cerebral malaria-like histopathology, and P. yoelii YM. As expected, P. berghei ANKA infection caused neurological signs, cerebral hemorrhages, and BBB dysfunction in CBA/CaJ and Swiss Webster mice, while Balb/c and A/J mice were resistant. Surprisingly, PbNK induced ECM in CBA/CaJ mice, while all other mice were resistant. P. yoelii 17XL and P. yoelii YM caused lethal hyperparasitemia in all mouse strains; histopathological alterations, BBB dysfunction, or neurological signs were not observed. Intravital imaging revealed that infected erythrocytes containing mature parasites passed slowly through capillaries making intimate contact with the endothelium, but did not arrest. Except for relatively rare microhemorrhages, mice with ECM presented no obvious histopathological alterations that would explain the widespread disruption of the BBB. Intravital imaging did reveal, however, that postcapillary venules, but not capillaries or arterioles, from mice with ECM, but not hyperparasitemia, exhibit platelet marginalization, extravascular fibrin deposition, CD14 expression, and extensive vascular leakage. Blockage of LFA-1 mediated cellular interactions prevented leukocyte adhesion, vascular leakage, neurological signs, and death from ECM. The endothelial barrier-stabilizing mediators imatinib and FTY720 inhibited vascular leakage and neurological signs and prolonged survival to ECM. Thus, it appears that neurological signs and coma in ECM are due to regulated opening of paracellular-junctional and transcellular-vesicular fluid transport pathways at the neuroimmunological BBB.

Plasmodium falciparum, the deadliest of all human malaria parasites, can cause cerebral malaria, a severe and frequently fatal complication of this devastating disease. Young children are predominantly at risk and may progress rapidly from the first signs of neurological involvement to coma and death. Here we used a murine model for high-resolution in vivo imaging to demonstrate that cerebral malaria, but not high parasitemia and severe anemia, is associated with extensive leakage of fluid from cerebral blood vessels into the brain tissue. This vascular leakage occurs downstream from the capillary bed, at the neuroimmunological blood brain barrier, a site recently recognized as the immune cell entry point into the brain during neuroinflammation. Vascular leakage is closely associated with the appearance of neurological signs suggesting that the ultimate cause of brain edema, coma and death in cerebral malaria is a widespread opening of the neuroimmunological blood brain barrier. Indeed, vascular leakage, neurological signs, and death from ECM can be prevented with endothelial barrier-stabilizing drugs. Based on the unique role of this anatomical feature in neuroinflammation, our findings are expected to have implications for other infectious diseases and autoimmune disorders of the central nervous system.

CNS hypoxia is more pronounced in murine cerebral than noncerebral malaria and is reversed by erythropoietin

Cerebral malaria (CM) is associated with high mortality and risk of sequelae, and development of adjunct therapies is hampered by limited knowledge of its pathogenesis. To assess the role of cerebral hypoxia, we used two experimental models of CM, Plasmodium berghei ANKA in CBA and C57BL/6 mice, and two models of malaria without neurologic signs, P. berghei K173 in CBA mice and P. berghei ANKA in BALB/c mice. Hypoxia was demonstrated in brain sections using intravenous pimonidazole and staining with hypoxia-inducible factor-1α-specific antibody. Cytopathic hypoxia was studied using poly (ADP-ribose) polymerase-1 (PARP-1) gene knockout mice. The effect of erythropoietin, an oxygen-sensitive cytokine that mediates protection against CM, on cerebral hypoxia was studied in C57BL/6 mice. Numerous hypoxic foci of neurons and glial cells were observed in mice with CM. Substantially fewer and smaller foci were observed in mice without CM, and hypoxia seemed to be confined to neuronal cell somas. PARP-1-deficient mice were not protected against CM, which argues against a role for cytopathic hypoxia. Erythropoietin therapy reversed the development of CM and substantially reduced the degree of neural hypoxia. These findings demonstrate cerebral hypoxia in malaria, strongly associated with cerebral dysfunction and a possible target for adjunctive therapy.

Murine cerebral malaria is associated with a vasospasm-like microcirculatory dysfunction, and survival upon rescue treatment is markedly increased by nimodipine

Brain hemodynamics in cerebral malaria (CM) is poorly understood, with apparently conflicting data showing microcirculatory hypoperfusion and normal or even increased blood flow in large arteries. Using intravital microscopy to assess the pial microvasculature through a closed cranial window in the murine model of CM by Plasmodium berghei ANKA, we show that murine CM is associated with marked decreases (mean: 60%) of pial arteriolar blood flow attributable to vasoconstriction and decreased blood velocity. Leukocyte sequestration further decreased perfusion by narrowing luminal diameters in the affected vessels and blocking capillaries. Remarkably, vascular collapse at various degrees was observed in 44% of mice with CM, which also presented more severe vasoconstriction. Coadministration of artemether and nimodipine, a calcium channel blocker used to treat postsubarachnoid hemorrhage vasospasm, to mice presenting CM markedly increased survival compared with artemether plus vehicle only. Administration of nimodipine induced vasodilation and increased pial blood flow. We conclude that vasoconstriction and vascular collapse play a role in murine CM pathogenesis and nimodipine holds potential as adjunctive therapy for CM.

Cytokines and adhesion molecules expression in the brain in human cerebral malaria

Although the role of systemic proinflammatory cytokines, IL-1β and TNF-α, and their up-regulation of adhesion molecules, ICAM-1, VCAM-1 and E-Selectin, in the pathogenesis of cerebral malaria (CM) is well established, the role of local cytokine release remain unclear. Immunohistochemistry (IHC) was used to compare the expression of ICAM-1, VCAM-1, E-Selectin, IL-1β, TNF-α and TGF- β at light microscopic level in cerebral, cerebellar and brainstem postmortem cryostat sections from 10 CM, 5 severe malarial anemia (SMA), 1 purulent bacterial meningitis (PBM), 2 non-central nervous system infections (NCNSI) and 3 non-infections (NI) deaths in Ghanaian children. Fatal malaria and Salmonella sepsis showed significantly higher vascular expression of all 3 adhesion molecules, with highly significant co-localization with sequestration in the malaria cases. However, there was negligible difference between CM and SMA. TGF-β showed intravascular and perivascular distribution in all cases, but expression was most intense in the PBM case and CM group. TNF-α and IL-1β showed prominent brain parenchymal staining, in addition to intravascular and perivascular staining, in only the PBM case and CM group. The maximal expression of all 6 antigens studied was in the cerebellar sections of the malaria cases. Endothelial activation is a feature of fatal malaria and Salmonella sepsis, with adhesion molecule expression being highly correlated with sequestration. IL-1β and TNF-α are upregulated in only cases with neurodegenerative lesions, whilst TGF-β is present in all cases. Both cytokines and adhesion molecules were maximally upregulated in the cerebellar sections of the malaria cases.

High-level cerebellar expression of cytokines and adhesion molecules in fatal, paediatric, cerebral malaria

Although the roles played by systemic tumour necrosis factor (TNF) and interleukin 1beta (IL-1beta), and their upregulation of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and E-selectin, in the pathogenesis of human cerebral malaria (CM) are well established, the role of local cytokine release, in the brain, remains unclear. Immunohistochemistry was therefore used to compare the expression of ICAM-1, VCAM-1, E-selectin, IL-1beta, TNF and transforming growth factor beta (TGF-beta) at light-microscope level, in cryostat sections of cerebral, cerebellar and brainstem tissues collected, post-mortem, from Ghanaian children. Among the 21 children investigated were 10 cases of CM, five of severe malarial anemia (SMA), one of purulent bacterial meningitis (PBM), two of non-central-nervous-system infection (NCNSI) and three children who had no infection (NI) when they died. Parasitised erythrocytes were detected in all of the sections from the cases of fatal malaria (CM and SMA), and sequestered leucocytes were present in most of the sections from the CM cases (but none of the sections from the SMA cases). Significantly elevated vascular expression of all three adhesion molecules investigated was detected in the brains of the 15 cases of fatal malaria and one of the cases of NCNSI (a child with Salmonella septicaemia), and in the malaria cases this showed highly significant co-localization with the areas of erythrocyte sequestration. In terms of the levels of expression of ICAM-1, VCAM-1 and E-selectin, there were, however, negligible differences between the CM and SMA cases. Although TGF-beta showed intravascular and perivascular distribution in all the subjects, its expression was most intense in the PBM case and the CM group. Only in the sections from the PBM and CM cases did TNF and IL-1beta show prominent brain parenchymal staining, in addition to the intravascular and perivascular staining seen in all subjects. The highest observed expression of each of the six antigens studied was in the cerebellar sections of the malaria cases. Endothelial activation in the brain therefore appears to be a feature of fatal malaria and Salmonella sepsis, and in cases of fatal malaria is closely associated with leucocyte sequestration. In the present study, IL-1beta and TNF were only up-regulated in the brains of children with neurodegenerative lesions, whereas TGF-beta was present in all cases.

Pathogenic role of P-selectin in experimental cerebral malaria: importance of the endothelial compartment

P-selectin is a leukocyte adhesion receptor expressed on the surface of activated platelets and endothelial cells. Its role in the pathogenesis of cerebral malaria was explored in a murine model of cerebral malaria. Infection of mice with Plasmodium berghei ANKA led to P-selectin up-regulation in brain vessels of cerebral malaria-susceptible mice but not of cerebral malaria-resistant mice. Treatment of susceptible mice with anti-mouse P-selectin mAb failed to prevent the development of the neurological syndrome. However, P-selectin-deficient mice infected with Plasmodium berghei ANKA had a cumulative incidence of cerebral malaria which was significantly reduced compared to wild-type animals (4.5% versus 80%, respectively), despite identical levels of parasitemia, platelet and leukocyte accumulation. To determine whether P-selectin on platelets and/or endothelium was responsible for the microvascular pathology, cerebral malaria was assessed in chimeric mice deficient in platelet or endothelial P-selectin, which were generated by bone marrow transplantation. Mice deficient only in endothelial P-selectin did not show any sign of cerebral malaria (vascular plugging, hemorrhages, or edema), while mice lacking only platelet P-selectin showed signs of cerebral malaria similar to that seen in wild-type mice. These results indicate that endothelial P-selectin plays an important role in the pathogenesis of cerebral malaria.

Pathophysiology of cerebral malaria: role of host cells in the modulation of cytoadhesion

Cerebral malaria (CM), one of the most serious complications of Plasmodium falciparum infection, is characterized by the sequestration of infected erythrocytes (IEs) in cerebral microvascular beds. The precise mechanisms involved in the onset of neuropathology remain unknown, but parasite sequestration in the brain, metabolic disturbances, and host immune responses all play a role. Studies in a murine model of CM showed a potential role for host cells, especially platelets, in the pathogenesis of CM. Indeed, urokinase plasminogen activator receptor (uPAR; CD87) deficiency attenuates the severity of CM, most likely by its important role in platelet kinetics and trapping. These results led us to evaluate whether platelets have a role in the human disease. By immunostaining of brain samples from Malawian patients, we determined that the surface of platelet accumulation and the proportion of vessels filled with platelets were significantly higher in patients who died of CM than in those who died of other causes. We then investigated the role of platelets in IE cytoadhesion in vitro, using CD36-binding IE (IECD36) and CD36-deficient (CD36DEF) brain microvascular endothelial cells (ECs). Coincubation studies indicated that platelets can induce strong IECD36 binding to CD36DEF ECs and, conversely, can hide constitutively expressed falciparum receptors such as chondroitin sulfate A. Thus, platelets may provide an adhesion receptor to microvascular beds originally devoid of it. This novel mechanism of cytoadhesion may reorient the sequestration of different parasite phenotypes and play an important role in the pathogenesis of severe malaria.

Susceptibility to experimental cerebral malaria induced by Plasmodium berghei ANKA in inbred mouse strains recently derived from wild stock

The neurological syndrome caused by Plasmodium berghei ANKA in rodents partially mimics the human disease. Several rodent models of cerebral malaria (CM) exist for the study of the mechanisms that cause the disease. However, since common laboratory mouse strains have limited gene pools, the role of their phenotypic variations causing CM is restricted. This constitutes an obstacle for efficient genetic analysis relating to the pathogenesis of malaria. Most common laboratory mouse strains are susceptible to CM, and the same major histocompatibility complex (MHC) haplotype may exhibit different levels of susceptibility. We analyzed the influence of the MHC haplotype on overcoming CM by using MHC congenic mice with C57BL/10 and C3H backgrounds. No correlation was found between MHC molecules and the development of CM. New wild-derived mouse strains with wide genetic polymorphisms were then used to find new models of resistance to CM. Six of the twelve strains tested were resistant to CM. For two of them, F(1) progeny and backcrosses performed with the reference strain C57BL/6 showed a high level of heterogeneity in the number and characteristics of the genetic factors associated with resistance to CM.

Cytokine profile suggesting that murine cerebral malaria is an encephalitis

Cerebral malaria (CM) remains a poorly understood and life-threatening complication of malaria caused by the parasite Plasmodium falciparum. The discovery that murine CM caused by Plasmodium berghei ANKA and human CM are both characterized by production of inflammatory cytokines, especially tumor necrosis factor alpha (TNF-alpha), led to a revival of the suggestion that P. berghei CM may have value as a model of the human disease. In this study, quantitative reverse transcription-PCR was used to measure levels of message for 18S rRNA of P. berghei and 10 cytokines in the brains, livers, and spleens of mice during the induction and course of CM. A coordinated increase in RNA of parasite and proinflammatory cytokines was observed in the brains of mice in parallel with onset of CM. Levels of message for parasite, TNF-alpha, and gamma interferon increased in the brains of mice from day 5 to death on day 7. These changes were observed only in the brain, and message for other cytokines remained near baseline levels. This demonstrated that parasite sequestration does take place in the brains of mice with CM. Histologically, CM was characterized by widespread damage to the microvasculature in the brain with focal infiltration of inflammatory cells. The pattern of cytokine production in the brain is characteristic of other murine encephalitides.

Deficits in delayed memory following cerebral malaria: a case study

Cerebral malaria is a common disease, but there have not been any reports or investigations of long-term neurological or neuropsychological outcome. We present a case in which severe deficits in delayed memory and naming ability are observed 10 years after the patient contracted cerebral malaria. Neuropsychological testing and medical imaging are both consistent with temporal lobe/hippocampal dysfunction, which corroborates earlier animal research that cerebral malaria is particularly likely to lead to interrupted blood circulation in this area.

Selective damage of hippocampal neurons in murine cerebral malaria prevented by pentoxifylline

The effect of pentoxifylline, a phosphodiesterase inhibitor, was investigated on the development of cerebral malaria in Plasmodium berghei K 173 infected C57/B16 mice. No significant differences occurred in the course of parasitemia and survival time after infection between control mice and pentoxifylline treated mice. Moreover, no differences were observed between the groups with respect to the occurrence of cerebral malaria. The only striking difference was that pentoxifylline treatment selectively prevented neuronal cell damage in the sector CA1 of the hippocampus. These findings are in contrast to previous studies, where pentoxifylline prevented cerebral malaria in P. berghei ANKA infected CBA/Ca mice, another widely used model of cerebral malaria. Obvious differences exist between these models.