Behavioral alterations in long-term Toxoplasma gondii infection of C57BL/6 mice are associated with neuroinflammation and disruption of the blood brain barrier.

The Apicomplexa protozoan Toxoplasma gondii is a mandatory intracellular parasite and the causative agent of toxoplasmosis. This illness is of medical importance due to its high prevalence worldwide and may cause neurological alterations in immunocompromised persons. In chronically infected immunocompetent individuals, this parasite forms tissue cysts mainly in the brain. In addition, T. gondii infection has been related to mental illnesses such as schizophrenia, bipolar disorder, depression, obsessive-compulsive disorder, as well as mood, personality, and other behavioral changes. In the present study, we evaluated the kinetics of behavioral alterations in a model of chronic infection, assessing anxiety, depression and exploratory behavior, and their relationship with neuroinflammation and parasite cysts in brain tissue areas, blood-brain-barrier (BBB) integrity, and cytokine status in the brain and serum. Adult female C57BL/6 mice were infected by gavage with 5 cysts of the ME-49 type II T. gondii strain, and analyzed as independent groups at 30, 60 and 90 days postinfection (dpi). Anxiety, depressive-like behavior, and hyperactivity were detected in the early (30 dpi) and long-term (60 and 90 dpi) chronic T. gondii infection, in a direct association with the presence of parasite cysts and neuroinflammation, independently of the brain tissue areas, and linked to BBB disruption. These behavioral alterations paralleled the upregulation of expression of tumor necrosis factor (TNF) and CC-chemokines (CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1ß and CCL5/RANTES) in the brain tissue. In addition, increased levels of interferon-gamma (IFNγ), TNF and CCL2/MCP-1 were detected in the peripheral blood, at 30 and 60 dpi. Our data suggest that the persistence of parasite cysts induces sustained neuroinflammation, and BBB disruption, thus allowing leakage of cytokines of circulating plasma into the brain tissue. Therefore, all these factors may contribute to behavioral changes (anxiety, depressive-like behavior, and hyperactivity) in chronic T. gondii infection.

A study for precision diagnosing and treatment strategies in difficult-to-treat AIDS cases and HIV-infected patients with highly fatal or highly disabling opportunistic infections: Study protocol for antiretroviral therapy timing in AIDS patients with toxoplasma encephalitis.

BACKGROUND: Toxoplasma encephalitis (TE) is one of the main opportunistic infections in acquired immunodeficiency syndrome (AIDS) patients, and represents a social burden due to its high prevalence and morbidity. Concomitant antiretroviral therapy (ART), together with effective anti- toxoplasma combination therapy, is an effective strategy to treat AIDS-associated TE (AIDS/TE) patients. However, the timing for the initiation of ART after diagnosis of TE remains controversial. We therefore designed the present study to determine the optimal timing for ART initiation in AIDS/TE patients. METHODS/DESIGN: This trial is a 17-center, randomized, prospective clinical study with 2 parallel arms. A total of 200 participants will be randomized at a 1:1 ratio into the 2 arms: the early ART initiation (≤14 days after TE diagnosis) arm and the deferred ART (>14 days after TE diagnosis) arm. The primary outcome will be the difference of mortality between the 2 arms at 48 weeks. The secondary outcomes will be the differences between the 2 arms in the changes of CD4+ counts from baseline to week 48, the rate of virologic suppression (HIV ribonucleic acid <50 copies/mL) from baseline to week 48, the incidence of TE-associated immune reconstitution inflammatory syndrome during the study period, and the incidence of adverse effects during the study period. DISCUSSION: This present trial aims to evaluate the optimal timing for ART initiation in AIDS/TE patients, and will provide strong evidence for AIDS/TE treatment should it be successful. TRIAL REGISTRATION: This trial was registered as one of the 12 trials under the name of a general project at the chictr.gov (http://www.chictr.org.cn/showproj.aspx?proj=35362) on February 1, 2019, and the registration number of the general project is ChiCTR1900021195.

Metastatic Malignant Lymphoma Mimicking Cerebral Toxoplasmosis with the "Target Sign".

We herein report the case of a 60-year-old man with a "target sign" in the left frontal lobe on magnetic resonance imaging (MRI), which is thought to be a specific sign of cerebral toxoplasmosis. 18F-fluorodeoxyglucose-positron emission tomography showed no increased uptake, and 201Tl-single photon emission computed tomography showed the focal uptake in the left frontal lesion. On a brain biopsy, the patient was given a definitive diagnosis of brain metastasis from diffuse large B-cell lymphoma, and cerebral toxoplasmosis was excluded. In the present case, multilayer intensities on MRI may reflect the fast-growing nature of this tumor.

Galectin-3 and Galectin-9 May Differently Regulate the Expressions of Microglial M1/M2 Markers and T Helper 1/Th2 Cytokines in the Brains of Genetically Susceptible C57BL/6 and Resistant BALB/c Mice Following Peroral Infection With Toxoplasma gondii.

Toxoplasmic encephalitis (TE), an opportunistic infection, is a severe health problem in immunocompromised patients. Previous studies have revealed that C57BL/6 mice are susceptible and BALB/c mice are resistant to TE. To investigate the mechanisms involved in the immunopathogenesis of TE in susceptible C57BL/6 and resistant BALB/c mice, both strains of mice were perorally infected with the Prugniuad (Pru) strain of Toxoplasma gondii. Our results showed that compared with BALB/c mice, C57BL/6 mice infected with T. gondii Pru strain had more severe brain histopathological damage, and higher mRNA expression levels of tachyzoite-specific surface antigen 1, bradyzoite-specific antigen 1, interferon gamma (IFNγ), interleukin (IL)-10, arginase1 (Arg1) (M2 marker), galectin (Gal)-3, Gal-9, T. gondii microneme protein 1 (TgMIC1), TgMIC4, and TgMIC6 during the course of infection by using quantitative real-time reverse transcription-polymerase chain reaction. Further analysis displayed that BALB/c mice showed higher numbers of microglial cells and higher levels of IL-1ß, inducible nitric oxide synthase (iNOS) (M1 marker), and chitinase-3-like protein 3 (Ym1) (M2 marker) in the early infective stage [at day 14 or 35 post infection (p.i.)] compared with C57BL/6 mice, whereas C57BL/6 mice showed higher numbers of microglial cells and higher levels of IL-10, iNOS (M1 marker), and Ym1 (M2 marker) at days 35, 50, or 70 p.i. compared with BALB/c mice. Correlation analysis showed that significant positive correlations existed between Gal-3 and IL-4/IL-10/iNOS/Ym1 and between Gal-9 and IL-4/Ym1 in C57BL/6 mice; between Gal-3 and IFNγ/Arg1 and between Gal-9 and IFNγ/Arg1 in BALB/c mice. Together, our data demonstrated that different Gal-3 and Gal-9 expressions as well as different positive correlations were found between Gal-3 and T helper 1 (Th1)/Th2/M1/M2 cytokines or between Gal-9 and Th1/Th2/M2 cytokines in the brains of T. gondii Pru strain-infected C57BL/6 and BALB/c mice.

Taenia crassiceps antigens induce a Th2 immune response and attenuate injuries experimentally induced by neurotoxoplasmosis in BALB/c mice.

Toxoplasma gondii is a pathogenic agent responsible for causing both systemic and local disease which elicits a typically pro-inflammatory, Th1 immune response. Taenia crassiceps antigen induces a Th2 immune response that immunomodulates Th1 based infections. Therefore the aim of this study was to evaluate whether T. crassiceps cysticerci antigens are able to modulate the inflammatory response triggered in experimental neurotoxoplasmosis (NT). BALB/c mice were inoculated with T. gondii cysts and/or cysticerci antigens and euthanized at 60 and 90days after inoculation (DAI). The histopathology of the brains and cytokines produced by spleen cells culture were performed. The animals from the NT group, 90DAI (NT90), presented greater intensity of lesions such as vasculitis, meningitis and microgliosis and cytokines from Th1 profile characterized by high levels of IFN-gamma. While in the T. crassiceps antigens group, 60DAI, there were more discrete lesions and high levels of IL-4, a Th2 cytokine. In the NT co-inoculated with cysticerci antigens group the parenchyma lesions were more discrete with lower levels of IFN-gamma and higher levels of IL-4 when compared to NT90. Therefore the inoculation of T. crassiceps antigens attenuated the brain lesions caused by T. gondii inducing a Th2 immune response.

A delayed diagnosis of X-linked hyper IgM syndrome complicated with toxoplasmic encephalitis in a child: A case report and literature review.

INTRODUCTION: The X-linked hyper-immunoglobulin M syndrome (XHIGM) is an uncommon primary combined immunodeficiency disease caused by CD40L gene mutations. A delayed or missed diagnosis of XHIGM is common and concerning, owing to atypical immunoglobulin profile and phenotype of some patients, low recognition, and limited knowledge of clinicians on XHIGM in some underdeveloped areas. Opportunistic infections are a prominent clinical feature of XHIGM. However, toxoplasma encephalitis occurs sporadically and is extremely rare in patients with XHIGM. DIAGNOSTIC AND THERAPEUTIC PROCEDURE: A 2 years and 10 months' old male suffered from 3 times of serious infection since 1 year and 4 months of age. Although with history of recurrent respiratory infections, protracted diarrhea, persistent or intermittent neutropenia companioned with oral ulcer, and a typical immunoglobulin profile during his second disease attack, the consideration of XHIGM was still completely ignored because of our low recognition and limited knowledge of this disorder. The diagnosis of XHIGM was ultimately confirmed by detection of elevated serum IgM concentration, decreased serum IgG and IgE concentration, and identification of a mutation c.654C>A (p.C218X) in CD40L gene. Given clinical manifestation of lethargy, uncontrollable somnolence and ataxia, a cat/dog exposure history, positive serum Toxoplasma gondii (T gondii) IgM, positive cerebrospinal fluid T gondii PCR results, and typical characteristics of brain magnetic resonance imaging as multiple rings liked nodules lesions in bilateral cerebral hemisphere cortex, bilateral basal ganglia, and dorsal thalamus, the diagnosis of toxoplasmic encephalitis was considered during his third disease attack. Thereafter, oral administration of sulfadiazine and azithromycin, intravenous immunoglobulin, and subcutaneous injection of G-CSF were initiated. Regrettably, the patient abandoned the treatment because of economic factor and died 3 months after discharge. CONCLUSIONS: A more thorough clinical history and some features like recurrent respiratory infections, protracted diarrhea, and persistent or intermittent neutropenia companioned with oral ulcer could increase clinical suspicion of XHIGM. Cerebral toxoplasmosis is rare in patients with XHIGM, but still should be considered. The present study firstly reported a delayed diagnosed case of XHIGM with CD40L gene c.654C>A (p.C218X) mutant complicated with toxoplasma encephalitis in Chinese population, which highlighted the importance of CD40-CD40L interaction in cell-mediated immunity against T gondii.

Increased expressions of ADAMTS-13 and apoptosis contribute to neuropathology during Toxoplasma gondii encephalitis in mice.

Toxoplasma gondii (T. gondii) is a protozoan parasite with the potential of causing severe encephalitis among immunocompromised humans and animals. Our previous study showed that T. gondii induces high nitric oxide (NO) production, high glial activation (GFAP) and neurofilament expressions, leading to severe neurodegeneration in toxoplasma encephalitis (TE) in the central nervous system (CNS). The aim of this experimental study was to investigate ADAMTS-13 expression and apoptosis in CNS and to identify whether they have any correlation with toxoplasmosis neuropathology and neurodegeneration. Mice were infected with ME49 strain T. gondii and the levels of ADAMTS-13, caspase 3, caspase 8, caspase 9, TNFR1 and Bcl-xL expressions were examined in brain tissues by immunohistochemistry, during the development and establishment of chronic infections at 10, 30 and 60 days post-infection. Results of the study revealed that the levels of ADAMTS-13 (P < 0.005), caspase 3 (P < 0.05), caspase 8 (P < 0.05), caspase 9 (P < 0.005) and TNFR1 (P < 0.05) expressions in the brain markedly increased while Bcl-xL expression decreased (P < 0.005). The most prominent finding from our study was that 10, 30 and 60 days post-infection ADAMTS-13 increased significantly and this may play an important role in the regulation and protection of the blood-brain barrier integrity and CNS microenvironment in TE. These results also suggest that T. gondii-mediated apoptosis might play a pivotal role and a different type of role in the mechanism of neurodegeneration and neuropathology in the process of TE. Furthermore, expression of ADAMTS-13 might give an idea of the progress and is critical for diagnosis of this disease. To the best of the authors' knowledge, this is the first report on ADAMTS-13 expression in the CNS of T. gondii-infected mice.

Interferon gamma effect on immune mediator production in human nerve cells infected by two strains of Toxoplasma gondii.

Interferon gamma (IFN-γ) is the major immune mediator that prevents toxoplasmic encephalitis in murine models. The lack of IFN-γ secretion causes reactivation of latent T. gondii infection that may confer a risk for severe toxoplasmic encephalitis. We analyse the effect of IFN-γ on immune mediator production and parasite multiplication in human nerve cells infected by tachyzoites of two T. gondii strains (RH and PRU). IFN-γ decreased the synthesis of MCP-1, G-CSF, GM-CSF and Serpin E1 in all cell types. It decreased IL-6, migration inhibitory factor (MIF) and GROα synthesis only in endothelial cells, while it increased sICAM and Serpin E1 synthesis only in neurons. The PRU strain burden increased in all nerve cells and in contrast, RH strain replication was controlled in IFN-γ-stimulated microglial and endothelial cells but not in IFN-γ-stimulated neurons. The proliferation of the PRU strain in all stimulated cells could be a specific effect of this strain on the host cell.

Toxoplasma gondii Infections Alter GABAergic Synapses and Signaling in the Central Nervous System.

UNLABELLED: During infections with the protozoan parasite Toxoplasma gondii, gamma-aminobutyric acid (GABA) is utilized as a carbon source for parasite metabolism and also to facilitate parasite dissemination by stimulating dendritic-cell motility. The best-recognized function for GABA, however, is its role in the nervous system as an inhibitory neurotransmitter that regulates the flow and timing of excitatory neurotransmission. When this pathway is altered, seizures develop. Human toxoplasmosis patients suffer from seizures, suggesting that Toxoplasma interferes with GABA signaling in the brain. Here, we show that while excitatory glutamatergic presynaptic proteins appeared normal, infection with type II ME49 Toxoplasma tissue cysts led to global changes in the distribution of glutamic acid decarboxylase 67 (GAD67), a key enzyme that catalyzes GABA synthesis in the brain. Alterations in GAD67 staining were not due to decreased expression but rather to a change from GAD67 clustering at presynaptic termini to a more diffuse localization throughout the neuropil. Consistent with a loss of GAD67 from the synaptic terminals, Toxoplasma-infected mice develop spontaneous seizures and are more susceptible to drugs that induce seizures by antagonizing GABA receptors. Interestingly, GABAergic protein mislocalization and the response to seizure-inducing drugs were observed in mice infected with type II ME49 but not type III CEP strain parasites, indicating a role for a polymorphic parasite factor(s) in regulating GABAergic synapses. Taken together, these data support a model in which seizures and other neurological complications seen in Toxoplasma-infected individuals are due, at least in part, to changes in GABAergic signaling. IMPORTANCE: Infections of the central nervous system can cause seizures. While inflammation in the brain has been proposed to initiate the onset of the seizures, relatively little is known about how inflammation impacts the structure and function of the neurons. Here we used a parasite called Toxoplasma gondii that infects the brain and showed that seizures arise due to a defect in signaling of GABA, which is the neurotransmitter primarily responsible for preventing the onset of seizures.

An expanded task battery in the Morris water maze reveals effects of Toxoplasma gondii infection on learning and memory in rats.

Infection with the neurotropic parasite Toxoplasma gondii is widespread among human populations; however, the impacts of latent central nervous system (CNS) T. gondii infection have only recently come to light. Epidemiological evidence in humans and experimental studies in rodents have revealed a number of neurological and behavioral sequelae following the establishment of latent CNS toxoplasmosis. Here, we report alterations in learning and memory task performance in latently infected rats using the Morris water maze. While simple spatial reference learning was intact, infected rodents exhibited poor performance compared to controls in probe trials requiring spatial memory recall and progressively poorer performance with increasing time intervals before memory testing, but, surprisingly, enhanced performance in reversal learning tasks. Despite obvious changes to memory task performance, no cysts were detected in the hippocampi of infected rats. Instead, cysts were stochastically distributed across the entire brain, suggesting that behavioral alterations in this study were due to accumulated changes in neurophysiology across multiple anatomical regions. Together, these data provide new evidence that latent toxoplasmosis contributes to neurocognitive symptoms in mammalian hosts, and does so on a broad anatomical scale within the CNS.

Congenital infection of mice with Toxoplasma gondii induces minimal change in behavior and no change in neurotransmitter concentrations.

We examined the effect of maternal Toxoplasma gondii infection on behavior and the neurotransmitter concentrations of congenitally infected CD-1 mice at 4 and 8 wk of age when latent tissue cysts would be present in their brains. Because of sex-associated behavioral changes that develop during aging, infected female mice were compared with control females and infected male mice were compared with control males. Only the short memory behavior (distance between goal box and first hole investigated) of male mice congenitally infected with T. gondii was significantly different (P < 0.05) from that of uninfected control males at both 4 and 8 wk by using the Barnes maze test. The other parameters examined in the latter test, i.e., functional observational battery tests, virtual cliff, visual placement, and activity tests, were not significantly different (P > 0.05) at 4 and 8 wk. Concentrations of neurotransmitters and their metabolites (dopamine; 3,4-dihydroxyphenylacetic acid; homovanillic acid; norepinephrine; epinephrine; 3-methoxy-4-hydroxyphenylglycol; serotonin; and 5-hydroxyindoleacetic acid) in the frontal cortex and striatum were not different (P > 0.05) between infected and control mice at 8 wk of age. The exact mechanism for the observed effect on short-term memory in male mice is not known, and further investigation may help elucidate the molecular mechanisms associated with the proposed link between behavioral changes and T. gondii infection in animals. We were not able, however, to confirm the widely held belief that changes in neurotransmitters result from chronic T. gondii infection of the brain.

Red blood cell-coupled tissue plasminogen activator prevents impairment of cerebral vasodilatory responses through inhibition of c-Jun-N-terminal kinase and potentiation of p38 mitogen-activated protein kinase after cerebral photothrombosis in the newborn pig.

OBJECTIVE: Pediatric ischemic stroke is a poorly understood, yet clinically important, problem. The sole approved treatment for acute stroke is tissue-type plasminogen activator. However, tissue plasminogen activator vasoactivity aggravates hypoxia/ischemia-induced impairment of cerebrovasodilation in response to hypercapnia and hypotension in newborn pigs. Mitogen-activated protein kinase (a family of 3 kinases, extracellular signal-related kinase, p38, and c-Jun-N-terminal kinase) is upregulated after hypoxia/ischemia. Coupling of tissue plasminogen activator to red blood cells prevented hypoxia/ischemia-induced impairment of dilation and suppressed extracellular signal-related kinase mitogen-activated protein kinase activation. This study investigated the differential roles of mitogen-activated protein kinase isoforms in the effects of red blood cells-tissue plasminogen activator on cerebrovasodilation in a translationally relevant injury model, photothrombosis. DESIGN: Prospective, randomized animal study. SETTING: : University laboratory. SUBJECTS: Newborn (1- to 5-day-old) pigs. INTERVENTIONS: Cerebral blood flow and pial artery diameter were determined before and after photothrombotic injury (laser 532 nm and erythrosine B) was produced in piglets equipped with a closed cranial window. Cerebral blood flow extracellular signal-related kinase, p38, and c-Jun-N-terminal kinase mitogen-activated protein kinase were determined by enzyme-linked immunosorbent assay. MEASUREMENTS AND MAIN RESULTS: Tissue plasminogen activator and red blood cells-tissue plasminogen activator alleviated reduction of cerebral blood flow after photothrombotic injury. Cerebrovasodilation was blunted by photothrombotic injury, reversed to vasoconstriction by tissue plasminogen activator, but dilation was maintained by red blood cells-tissue plasminogen activator. Cerebral blood flow c-Jun-N-terminal kinase and p38 mitogen-activated protein kinase but not extracellular signal-related kinase mitogen-activated protein kinase was elevated by photothrombotic injury, an effect potentiated by tissue plasminogen activator. Red blood cells-tissue plasminogen activator blocked c-Jun-N-terminal kinase but potentiated p38 mitogen-activated protein kinase upregulation after photothrombotic injury. A c-Jun-N-terminal kinase mitogen-activated protein kinase antagonist prevented, a p38 mitogen-activated protein kinase antagonist potentiated, whereas an extracellular signal-related kinase mitogen-activated protein kinase antagonist had no effect on dilator impairment after photothrombotic injury. CONCLUSIONS: These data indicate that in addition to restoring perfusion, red blood cells-tissue plasminogen activator prevents impairment of cerebrovasodilation after photothrombotic injury through blockade of c-Jun-N-terminal kinase and potentiation of p38 mitogen-activated protein kinase. These data suggest tissue plasminogen activator coupling to red blood cells offers a novel approach to increase the benefit/risk ratio of thrombolytic therapy to treat central nervous system ischemic disorders.

Cerebral toxoplasmosis in Acquired Immunodeficiency Syndrome (AIDS) patients also provides unifying pathophysiologic hypotheses for Holmes tremor.

BACKGROUND: Holmes tremor is a rare symptomatic movement disorder. Currently suggested pathophysiological mechanisms of the disease are mostly derived from stroke cases. Although rare, cerebral toxoplasmosis may strengthen the pathophysiologic mechanism of disease. CASE PRESENTATION: A case of Holmes tremor secondary to cerebral toxoplasmosis in an AIDS patient is presented. A relevant literature search was performed, using pubmed and several entries for Holmes tremor as labelled in the literature. The unifying feature of our case and those of the literature is the involvement of either the cerebello-thalamo-cortical and/or the dentato-rubro-olivary pathways. The abscess or the extension of surrounding edema beyond these two circuits may account for the superimposed dysfunction of the nigrostriatal system in some but not all cases. The short delay observed in our observation and the dramatic response to treatment may indirectly support the secondary neuronal degeneration theory in the mechanism of Holmes tremor. CONCLUSION: Cases of cerebral toxoplasmosis in AIDS patients also provide arguments for the role of the thalamo-cortical and/or the dentato-rubro-olivary pathways dysfunction in the pathogenesis of Holmes tremor. Involvement of the nigro-striatal pathway may not be crucial in the development of this syndrome. Our case also brings additional indirect arguments for the role of secondary neuronal degeneration in the mechanism of Holmes tremor.

NF-kappaB1 contributes to T cell-mediated control of Toxoplasma gondii in the CNS.

In this study, the role of NF-kappaB1 was examined during toxoplasmosis. While wildtype BALB/c mice generated protective responses, NF-kappaB1(-/-) mice developed Toxoplasmic encephalitis, characterized by increased parasite burden and necrosis in the brain. Susceptibility was primarily associated with a local decrease in the number of CD8(+) T cells and IFN-gamma production, while accessory cell function appeared intact in NF-kappaB1(-/-) mice. Consistent with these findings, T cell transfer studies revealed that NF-kappaB1(-/-) T cells provided SCID mice less protection than wildtype T cells. These results demonstrate an intrinsic role for NF-kappaB1 in T cell-mediated immunity to Toxoplasmagondii.

Unusual cause of dementia in an immunocompetent host: toxoplasmic encephalitis.

A 69-year-old male was presented with a 2-month history of cognitive decline. The most profound deficit was observed in short-term verbal and visual memory and recognition. He was otherwise healthy, apart from atrial fibrillation diagnosed 5 months before. Brain MRI revealed T2 hyperintensities in the left thalamus, right pulvinar thalami, both putamina and right head of caudate nucleus without diffusion restriction on DWI sequences. CSF examination revealed elevated proteins. He was HIV negative. The course of the disease was complicated with gram negative sepsis and the patient died 14 days later. Autopsy revealed the brain lesions to have been caused by toxoplasmic encephalitis. Toxoplasmic encephalitis is an extremely rare cause of rapidly progressive dementia in immunocompetent patients. In patients with multiple lesions, hyperintense on T2 and hypointense on T1 weighted sequences, without diffusion restriction and some expansive effect, infectious causes should be considered, even in the absence of classical signs of infectious diseases and CSF pleocythosis.

Neurological and behavioral abnormalities, ventricular dilatation, altered cellular functions, inflammation, and neuronal injury in brains of mice due to common, persistent, parasitic infection.

BACKGROUND: Worldwide, approximately two billion people are chronically infected with Toxoplasma gondii with largely unknown consequences. METHODS: To better understand long-term effects and pathogenesis of this common, persistent brain infection, mice were infected at a time in human years equivalent to early to mid adulthood and studied 5-12 months later. Appearance, behavior, neurologic function and brain MRIs were studied. Additional analyses of pathogenesis included: correlation of brain weight and neurologic findings; histopathology focusing on brain regions; full genome microarrays; immunohistochemistry characterizing inflammatory cells; determination of presence of tachyzoites and bradyzoites; electron microscopy; and study of markers of inflammation in serum. Histopathology in genetically resistant mice and cytokine and NRAMP knockout mice, effects of inoculation of isolated parasites, and treatment with sulfadiazine or alphaPD1 ligand were studied. RESULTS: Twelve months after infection, a time equivalent to middle to early elderly ages, mice had behavioral and neurological deficits, and brain MRIs showed mild to moderate ventricular dilatation. Lower brain weight correlated with greater magnitude of neurologic abnormalities and inflammation. Full genome microarrays of brains reflected inflammation causing neuronal damage (Gfap), effects on host cell protein processing (ubiquitin ligase), synapse remodeling (Complement 1q), and also increased expression of PD-1L (a ligand that allows persistent LCMV brain infection) and CD 36 (a fatty acid translocase and oxidized LDL receptor that mediates innate immune response to beta amyloid which is associated with pro-inflammation in Alzheimer's disease). Immunostaining detected no inflammation around intra-neuronal cysts, practically no free tachyzoites, and only rare bradyzoites. Nonetheless, there were perivascular, leptomeningeal inflammatory cells, particularly contiguous to the aqueduct of Sylvius and hippocampus, CD4+ and CD8+ T cells, and activated microglia in perivascular areas and brain parenchyma. Genetically resistant, chronically infected mice had substantially less inflammation. CONCLUSION: In outbred mice, chronic, adult acquired T. gondii infection causes neurologic and behavioral abnormalities secondary to inflammation and loss of brain parenchyma. Perivascular inflammation is prominent particularly contiguous to the aqueduct of Sylvius and hippocampus. Even resistant mice have perivascular inflammation. This mouse model of chronic T. gondii infection raises questions of whether persistence of this parasite in brain can cause inflammation or neurodegeneration in genetically susceptible hosts.