Choroid plexus immune cell response in murine hydrocephalus induced by intraventricular hemorrhage.

BACKGROUND: Intraventricular hemorrhage (IVH) and associated hydrocephalus are significant complications of intracerebral and subarachnoid hemorrhage. Despite proximity to IVH, the immune cell response at the choroid plexus (ChP) has been relatively understudied. This study employs CX3CR-1GFP mice, which marks multiple immune cell populations, and immunohistochemistry to outline that response. METHODS: This study had four parts all examining male adult CX3CR-1GFP mice. Part 1 examined naïve mice. In part 2, mice received an injection 30 µl of autologous blood into right ventricle and were euthanized at 24 h. In part 3, mice underwent intraventricular injection of saline, iron or peroxiredoxin 2 (Prx-2) and were euthanized at 24 h. In part 4, mice received intraventricular iron injection and were treated with either control or clodronate liposomes and were euthanized at 24 h. All mice underwent magnetic resonance imaging to quantify ventricular volume. The ChP immune cell response was examined by combining analysis of GFP(+) immune cells and immunofluorescence staining. RESULTS: IVH and intraventricular iron or Prx-2 injection in CX3CR-1GFP mice all induced ventriculomegaly and activation of ChP immune cells. There were very marked increases in the numbers of ChP epiplexus macrophages, T lymphocytes and neutrophils. Co-injection of clodronate liposomes with iron reduced the ventriculomegaly which was associated with fewer epiplexus and stromal macrophages but not reduced T lymphocytes and neutrophils. CONCLUSION: There is a marked immune cell response at the ChP in IVH involving epiplexus cells, T lymphocytes and neutrophils. The blood components iron and Prx-2 may play a role in eliciting that response. Reduction of ChP macrophages with clodronate liposomes reduced iron-induced ventriculomegaly suggesting that ChP macrophages may be a promising therapeutic target for managing IVH-induced hydrocephalus.

The choroid plexus links innate immunity to CSF dysregulation in hydrocephalus.

The choroid plexus (ChP) is the blood-cerebrospinal fluid (CSF) barrier and the primary source of CSF. Acquired hydrocephalus, caused by brain infection or hemorrhage, lacks drug treatments due to obscure pathobiology. Our integrated, multi-omic investigation of post-infectious hydrocephalus (PIH) and post-hemorrhagic hydrocephalus (PHH) models revealed that lipopolysaccharide and blood breakdown products trigger highly similar TLR4-dependent immune responses at the ChP-CSF interface. The resulting CSF "cytokine storm", elicited from peripherally derived and border-associated ChP macrophages, causes increased CSF production from ChP epithelial cells via phospho-activation of the TNF-receptor-associated kinase SPAK, which serves as a regulatory scaffold of a multi-ion transporter protein complex. Genetic or pharmacological immunomodulation prevents PIH and PHH by antagonizing SPAK-dependent CSF hypersecretion. These results reveal the ChP as a dynamic, cellularly heterogeneous tissue with highly regulated immune-secretory capacity, expand our understanding of ChP immune-epithelial cell cross talk, and reframe PIH and PHH as related neuroimmune disorders vulnerable to small molecule pharmacotherapy.

Hydrocephalus Induced by Intraventricular Peroxiredoxin-2: The Role of Macrophages in the Choroid Plexus.

The choroid plexus (CP) is the primary source of cerebrospinal fluid in the central nervous system. Recent evidence indicates that inflammatory pathways at the CP may be involved in hydrocephalus development. Peroxiredoxin 2 (Prx2) is a major component of red blood cells. Extracellular Prx2 is proinflammatory, and its release after red blood cell lysis may contribute to hydrocephalus after intraventricular hemorrhage. This study aimed to identify alterations in CP macrophages and dendritic cells following intracerebroventricular Prx2 injection and investigate the relationship between macrophages/dendritic cells and hydrocephalus. There were two parts to this study. In the first part, adult male Sprague-Dawley rats received an intracerebroventricular injection of Prx2 or saline. In the second part, Prx2 was co-injected with clodronate liposomes or control liposomes. All animals were euthanized at 24 h after magnetic resonance imaging. Immunohistochemistry was used to evaluate macrophages in CP, magnetic resonance imaging to quantify hydrocephalus, and histology to assess ventricular wall damage. The intracerebroventricular injection of Prx2 not only increased the OX-6 positive cells, but it also altered their location in the CP and immunophenotype. Co-injecting clodronate liposomes with Prx2 decreased the number of macrophages and simultaneously attenuated Prx2-induced hydrocephalus and ventricular wall damage. These results suggest that CP macrophages play an essential role in CP inflammation-induced hydrocephalus. These macrophages may be a potential therapeutic target in post-hemorrhagic hydrocephalus.

Intracranial Fungal Infection After Solid-Organ Transplant.

Neurologic complications after solid-organ transplant reveal a great spectrum of pathologies. Intracranial hemorrhages, cerebral ischemic lesions, infarctions, lymphoproliferative disorders, and infections, including aspergillosis, have been observed after liver transplant. Fungi constitute nearly 5% of all central nervous system infections, mainly occurring in immunocompromised patients. The most common causative agent is Aspergillus species. It presents either as maxillary sinusitis or pulmonary infection. Brain involvement of Aspergillus carries a high rate of mortality. Aspergillosis presents in the forms of meningitis, mycotic aneurysms, infarctions, and mass lesions. Aspergillosis does not have a specific radiologic appearance. Parenchymal aspergillosis has heterogenous signal intensity (hypointense on T1-weighted and hyperintense on T2-weighted images). Here, we present 3 patients who underwent solid-organ transplant and developed central nervous system aspergillosis. Different modalities of neurosurgical intervention were performed in combination with chemotherapy as part of their fungal therapy.

Inflammation-dependent cerebrospinal fluid hypersecretion by the choroid plexus epithelium in posthemorrhagic hydrocephalus.

The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) than any other epithelium and simultaneously functions as the blood-CSF barrier to gate immune cell entry into the central nervous system. Posthemorrhagic hydrocephalus (PHH), an expansion of the cerebral ventricles due to CSF accumulation following intraventricular hemorrhage (IVH), is a common disease usually treated by suboptimal CSF shunting techniques. PHH is classically attributed to primary impairments in CSF reabsorption, but little experimental evidence supports this concept. In contrast, the potential contribution of CSF secretion to PHH has received little attention. In a rat model of PHH, we demonstrate that IVH causes a Toll-like receptor 4 (TLR4)- and NF-κB-dependent inflammatory response in the CPE that is associated with a ∼3-fold increase in bumetanide-sensitive CSF secretion. IVH-induced hypersecretion of CSF is mediated by TLR4-dependent activation of the Ste20-type stress kinase SPAK, which binds, phosphorylates, and stimulates the NKCC1 co-transporter at the CPE apical membrane. Genetic depletion of TLR4 or SPAK normalizes hyperactive CSF secretion rates and reduces PHH symptoms, as does treatment with drugs that antagonize TLR4-NF-κB signaling or the SPAK-NKCC1 co-transporter complex. These data uncover a previously unrecognized contribution of CSF hypersecretion to the pathogenesis of PHH, demonstrate a new role for TLRs in regulation of the internal brain milieu, and identify a kinase-regulated mechanism of CSF secretion that could be targeted by repurposed US Food and Drug Administration (FDA)-approved drugs to treat hydrocephalus.

Hydrocephalus and arthrogryposis in an immunocompetent mouse model of ZIKA teratogeny: A developmental study.

The teratogenic mechanisms triggered by ZIKV are still obscure due to the lack of a suitable animal model. Here we present a mouse model of developmental disruption induced by ZIKV hematogenic infection. The model utilizes immunocompetent animals from wild-type FVB/NJ and C57BL/6J strains, providing a better analogy to the human condition than approaches involving immunodeficient, genetically modified animals, or direct ZIKV injection into the brain. When injected via the jugular vein into the blood of pregnant females harboring conceptuses from early gastrulation to organogenesis stages, akin to the human second and fifth week of pregnancy, ZIKV infects maternal tissues, placentas and embryos/fetuses. Early exposure to ZIKV at developmental day 5 (second week in humans) produced complex manifestations of anterior and posterior dysraphia and hydrocephalus, as well as severe malformations and delayed development in 10.5 days post-coitum (dpc) embryos. Exposure to the virus at 7.5-9.5 dpc induces intra-amniotic hemorrhage, widespread edema, and vascular rarefaction, often prominent in the cephalic region. At these stages, most affected embryos/fetuses displayed gross malformations and/or intrauterine growth restriction (IUGR), rather than isolated microcephaly. Disrupted conceptuses failed to achieve normal developmental landmarks and died in utero. Importantly, this is the only model so far to display dysraphia and hydrocephalus, the harbinger of microcephaly in humans, as well as arthrogryposis, a set of abnormal joint postures observed in the human setting. Late exposure to ZIKV at 12.5 dpc failed to produce noticeable malformations. We have thus characterized a developmental window of opportunity for ZIKV-induced teratogenesis encompassing early gastrulation, neurulation and early organogenesis stages. This should not, however, be interpreted as evidence for any safe developmental windows for ZIKV exposure. Late developmental abnormalities correlated with damage to the placenta, particularly to the labyrinthine layer, suggesting that circulatory changes are integral to the altered phenotypes.

Soluble Toll-Like Receptors 2 and 4 in Cerebrospinal Fluid of Patients with Acute Hydrocephalus following Aneurysmal Subarachnoid Haemorrhage.

BACKGROUND: Toll-like receptor (TLR) signalling begins early in subarachnoid haemorrhage (SAH), and plays a key role in inflammation following cerebral aneurysm rupture. Available studies suggest significance of endogenous first-line blockers of a TLR pathway-soluble TLR2 and 4. METHODS: Eighteen patients with SAH and acute hydrocephalus underwent endovascular coiling and ventriculostomy; sTLR2 and 4 levels were assayed in cerebrospinal fluid (CSF) collected on post-SAH days 0-3, 5, and 10-12. Release kinetics were defined. CSF levels of sTLR2 and 4 were compared with a control group and correlated with the clinical status on admission, the findings on imaging, the degree of systemic inflammation and the outcome following treatment. RESULTS: None of study group showed detectable levels of sTLR2 and 4 on post-SAH day 0-3. 13 patients showed increased levels in subsequent samples. In five SAH patients sTLR2 and 4 levels remained undetectable; no distinctive features of this group were found. On post-SAH day 5 the strongest correlation was found between sTLR2 level and haemoglobin level on admission (cc = -0.498, P = 0.037). On post-SAH day 10-12 the strongest correlation was revealed between sTLR2 and treatment outcome (cc = -0.501, P = 0.076). Remaining correlations with treatment outcome, status at admission, imaging findings and inflammatory markers on post-SAH day 5 and 10-12 were negligible or low (-0.5 ≤ cc ≤ 0.5). CONCLUSIONS: In the majority of cases, rupture of a cerebral aneurysm leads to delayed release of soluble TLR forms into CSF. sTLR2 and 4 seem to have minor role in human post-SAH inflammation due to delayed release kinetics and low levels of these protein.

Bacillus Calmette-Guérin is a preventive factor in mortality of childhood tuberculous meningitis.

OBJECTIVES: Studies have been done that have focused on the efficacy of bacillus Calmette-Guérin (BCG) vaccination in the prevention of cases of childhood tuberculous meningitis (TBM). However the efficacy of the vaccination in the prevention of mortality has not been sufficiently evaluated. This study aimed to determine the main features of TBM cases in childhood and to evaluate the factors related to mortality, proving the protective effect of BCG vaccination in childhood TBM. METHODS: In a retrospective approach, all consecutive cases of TBM in children that occurred between 1997 and 2005, at Dicle University Hospital, were studied. The following data were evaluated: demographic aspects, admission symptoms, radiology and laboratory findings, BCG vaccination status, tuberculin skin test (TST) positivity, and mortality rates. RESULTS: In total, 172 cases of childhood TBM were evaluated (mean age 53.3±55.7 months; 109 boys (63.4%)). The majority of these cases (70.4%) had typical TBM symptoms on admission. BCG vaccination data were available for 152 (88.4%) cases and 29 of them (19.1%) were positive. The TST was performed for 143 patients (83.1%) and 28 (19.6%) were found positive. Hydrocephalus was identified in 118 patients (68.6%) on computed tomography examination. A shunt was placed in 79 cases (45.9%). In total, 24 patients (14.0%) died in the hospital. TST negativity was a significant factor for mortality (p=0.012). BCG positivity was found to be a preventive factor from mortality (p=0.05). CONCLUSIONS: BCG vaccination is effective in the prevention of TBM-associated mortality in childhood. TST negativity may be a sign of a poor prognosis in TBM cases.

External hydrocephalus and subdural bleeding in infancy associated with transplacental anti-Ro antibodies.

BACKGROUND: The isolated finding of an unexplained chronic subdural haematoma in an infant may suggest non-accidental head injury (NAHI). The authors report a previously undescribed cause of multifocal chronic subdural haematoma in infancy which could result in a misdiagnosis of previous NAHI. METHODS: Two infants, aged 3 and 4 months of age, presented with progressively increasing head circumference measurements from birth. There was no history of encephalopathy. Retinal haemorrhages were not present. CT and MRI demonstrated bilateral subdural fluid collections over the frontal regions that were consistent with either chronic subdural haematomas or haemorrhagic subdural effusions. In view of the possibility of NAHI, child protection investigations were initiated. FINDINGS: In neither case did the child protection investigations raise concerns. Comprehensive investigations for known haematological and metabolic disorders associated with subdural haematomas or effusions in infants were all normal. In both cases the infant's mother had a history of Sjögren's syndrome and both infants had positive anti-Ro antibody at presentation. CONCLUSIONS: Transplacental acquisition of anti-Ro antibodies has been associated with external hydrocephalus. External hydrocephalus has been recognised as a predisposing factor for subdural haemorrhage. These are the first reported cases linking the presence of anti-Ro antibodies and external hydrocephalus with subdural fluid collections in infancy.

Effect of specimen storage conditions on newborn dried blood spots used to assess Toxoplasma gondii immunoglobulin M (IgM).

BACKGROUND: Newborn screening programs store-under varying conditions-residual dried blood spots (DBS). Residual DBS were used to investigate the contribution of congenital infection with Toxoplasma gondii to the etiology of hydrocephalus and as a key step, we assessed the effect of storage conditions on the stability of newborn screening biomarkers. METHODS: Infants with hydrocephalus (410 cases) were identified using population-based birth defects surveillance systems in California, North Carolina, and Texas. Infants without birth defects (448 controls) were randomly selected from the same geographic areas and time periods. California stores DBS with controlled temperature, while North Carolina and Texas store DBS under ambient conditions. After removal of personal identifiers, DBS were tested for Toxo-specific immunoglobulin-M (Toxo-IgM). Because of poor elution of DBS stored in ambient conditions, additional biomarkers were tested on a specimen subset. RESULTS: Among 858 DBS tested, Toxo-IgM was found in 3 cases and no controls from California (N=515) and in no specimens from North Carolina or Texas (N=343). Among the 98 specimens tested for selected biomarkers, statistically significant differences were found for California vs. combined North Carolina and Texas DBS (thyroid stimulating hormone, phenylalanine, methionine, leucine and citrulline p<0.0001; tyrosine and valine p<0.001). CONCLUSIONS: Storage conditions for residual DBS had an effect on the ability to extract, recover, and accurately measure Toxo-IgM and other biomarkers from the filter paper matrix.

Eosinophil activation in the cerebrospinal fluid of children with shunt obstruction.

OBJECTIVE: To determine if eosinophils are activated to release the cationic proteins, eosinophil cationic protein (ECP) and eosinophil-derived neurotoxin (EDN) in shunt obstruction, and to find out if these proteins are associated with ventriculoperitoneal shunt failure. PATIENTS AND METHODS: This was a prospective observational study carried out in a 20-bed tertiary pediatric intensive care unit. Patients studied were children aged 0-18 years with suspected ventriculoperitoneal shunt malfunction requiring shunt revision. No interventions were performed. Cerebrospinal fluid (CSF) was analyzed for cell count and EDN and ECP concentrations. Patients were prospectively followed for 6 months to evaluate shunt failure. RESULTS: In a 2-month period, 56 shunt revisions were performed on 56 children. Three children had culture-proven infection. Eosinophilia, defined as ≥ 5% eosinophils in the CSF, was present in 9 out of 53 children (17%). The 3 patients with infection did not have eosinophilia and were excluded from further analysis. Patients with CSF eosinophilia had higher concentrations of ECP (1.38 ± 0.66 vs. 0.41 ± 0.15 ng/ml; p = 0.013) and EDN (16.94 ± 5.83 vs. 4.69 ± 1.33 ng/ml; p = 0.011). Patients with CSF eosinophilia did not have more ventriculoperitoneal shunt revisions within 6 months (6 of 9) compared to those who did not have eosinophilia (21 of 44; p = 0.50). However, patients with higher levels of ECP in the CSF required more shunt revisions within 6 months of their surgeries (p < 0.05). CONCLUSIONS: In patients with malfunctioning ventriculoperitoneal shunts, CSF eosinophils are activated and release ECP and EDN. The presence of ECP is associated with a shorter shunt life.

Congenital posthemorrhagic hydrocephalus: a case of fetomaternal alloimmune thrombocytopenia.

Fetal/neonatal alloimmune thrombocytopenia (NAIT) results from fetomaternal mismatch for human platelet alloantigens leading to antibody-mediated destruction of fetal platelets. This is one of the most common causes of severe thrombocytopenia in the newborn with an incidence of 1/800-1,000. In the most severe cases, NAIT may result in intracranial hemorrhage and may lead to death or neurologic sequelae. We report a case of fetal hydrocephalus caused by NAIT and discuss the importance of making an accurate prenatal diagnosis to improve the management of the current pregnancy and the outcome of subsequent pregnancies. Screening of female siblings of affected cases is recommended in order to detect at-risk individuals.

Effect of shunt catheter on the systemic immune response: evaluation of neutrophil count, function, and rate of chemotaxis.

OBJECT: The localized impairment of the host defense mechanism due to the presence of a shunt apparatus has been suggested as a risk factor for shunt infection. The purpose of this study was to evaluate the probable systemic effect of a shunt catheter on neutrophil phagocytosis and chemotaxis in vivo. METHODS: Twenty-four children with hydrocephalus who were referred to the Children's Hospital Medical Center in Tehran for ventriculoperitoneal shunt placement were included in this study. Neutrophil count, chemotaxis, and nitroblue tetrazolium (NBT) tests were performed before and 2 months after the operation. In comparing the preoperative neutrophil count, NBT percentage, and chemotaxis (with and without the addition of a chemoattractant factor) with these same factors postoperatively, the authors found no statistically significant differences. In four children, shunt infections developed during the follow-up period. There were no significant differences between the aforementioned parameters in children with infected shunts and those with uninfected shunts. CONCLUSIONS: The results of this study do not support the idea of systemic impairment of neutrophils after shunt insertion. Further studies with more specific methods are required to elaborate on this issue.

Changes in immune and glial markers in the CSF of patients with Complex Regional Pain Syndrome.

Complex Regional Pain Syndrome is a severe chronic pain condition characterized by sensory, autonomic, motor and dystrophic signs and symptoms. The pain in CRPS is continuous, it worsens over time, and it is usually disproportionate to the severity and duration of the inciting event. This study compares cerebrospinal fluid (CSF) levels of pro- and anti-inflammatory cytokines, chemokines and several biochemical factors (glial fibrillary acidic protein (GFAP), the nitric oxide metabolites (nitrate plus nitrite), the excitatory amino acid neurotransmitter glutamate, calcium, total protein and glucose) in patients afflicted with CRPS to levels found in patients suffering with other non-painful or painful conditions. The aim of the study is to determine the degree of involvement of glial cells and immune system mediators in the pathophysiology of CRPS. There was no elevation or reduction of a CSF marker that was specific for CRPS patients. However, there were several patterns of markers that could be helpful in both elucidating the mechanisms involved in the disease process and supporting the diagnosis of CRPS. The most common pattern was found in 50% (11 out of 22) of the CRPS patients and consisted of; elevated IL-6, low levels of IL-4 or IL-10, increased GFAP or MCP1 and increases in at least two of the following markers NO metabolites, calcium or glutamate. The results from this and other similar studies may aid in elucidating the mechanisms involved in the pathophysiology of CRPS. A better understanding of these mechanisms may lead to novel treatments for this very severe, life-altering illness.

Hydrocephalus in CINCA syndrome treated with anakinra.

INTRODUCTION: Chronic infantile neurologic, cutaneous, articular (CINCA) syndrome is a rare congenital autoinflammatory disease characterized by neonatal-onset chronic meningitis, hydrocephalus, sensorineural hearing loss, persistent urticarial rash, deforming arthritis, and recurrent fever. This clinical entity is believed to result from dysregulation of cytokine production. No recommended treatment protocol exists so far for CINCA syndrome. CASE REPORT: We report a 7-year-old child affected with CINCA syndrome in whom no therapy had resulted effective. Anakinra, an interleukin-1-receptor antagonist, was administered in a 1-year period with complete inflammatory symptom remission and dramatically ameliorated laboratory tests. This optimal response has been supported by the demonstration of a stabilized hydrocephalus upon magnetic resonance imaging and by an overall improvement of the neurodevelopmental issues. DISCUSSION: This paper emphasizes and discusses the medical approach with anakinra in CINCA syndrome presenting with hydrocephalus in which a consistent control of the neurological picture can be obtained.

Increased intracranial pressure induces a rapid systemic interleukin-10 release through activation of the sympathetic nervous system.

There is a bi-directional communication between the immune and central nervous system. In this context, it is known that patients with traumatic brain injury suffered from systemic immunodepression and an increased risk to develop infectious complications. We investigated the role of an increased intracranial pressure (ICP) and sympathetic activation on systemic immune changes. A sustained increase in ICP was achieved by inflation of a subdural balloon. At different time points, plasma levels of the anti-inflammatory cytokine, interleukin (IL)-10, were measured. Furthermore, the effect of a sympathetic blockade by co-administration of the beta2-adreoreceptor antagonist, propranolol, was evaluated. Finally, we examined the impact of epinephrine infusion on blood IL-10 levels. We showed that an increase in ICP with activation of the sympathetic nervous system was able to induce systemic release of IL-10. This effect was blocked by administration of the beta2-adreoreceptor antagonist. Furthermore, epinephrine infusion directly induced systemic release of IL-10. Our data suggested that sympathetic activation with release of epinephrine may induce systemic immunodepression with risk of infectious complications in brain-injured patients.

Immune reactions associated with silicone-based ventriculo-peritoneal shunt malfunctions in children.

The implantation of ventriculo-peritoneal (VP) shunting systems is the most commonly performed neurological procedure in children with hydrocephalus. Although the overall complication risk is low, the cumulative risk of shunt failure is high and unfortunately results in a high prevalence of revision surgeries. In this study, we explored the concept that some pediatric patients may develop an immune response to either the proteins attached to the silicone implant surface or to the biomaterial itself, and that this reaction may contribute to VP shunt failure in some individuals. The data displays that the sterile shunt malfunction group had a higher rate of protein deposition and increased levels of autoantibodies to the extracted surface proteins as compared to individuals with functioning shunting systems. The precise nature of the shunt-bound proteins that serve as antigens in this experiment have not yet been determined. The data also indicated that some individuals develop antibodies to polymeric substances that cross-react with partially polymerized acrylamide. The detection of significant amounts of shunt-bound protein, antibody responses to these proteins and to polymeric substances suggest that an immunological response to these proteins may play a role in the mechanism behind sterile shunt malfunctions.

Neuronal vacuolation in the basal nucleus of meynert caused by fetal hydrocephalus.

The basal nucleus of Meynert, which provides the major source of cholinergic input to the cerebral cortex, was investigated in fetal hydrocephalic brains (n = 5) in comparison to controls (n = 5). To detect alterations, the neurons of the basal nucleus were immunostained with an antibody against the calcium-binding protein calbindin. In the basal nucleus of hydrocephalic brains, a moderate number of vacuolated neurons were observed. Such vacuolation was not seen in control brains. Vacuolation is interpreted as a degenerative change after injury of basal nucleus axons in cases of fetal hydrocephalus. The neuronal alterations in the basal nucleus may account at least in part for residual deficits observed after shunt placement.

Hydrocephalus induced by immunological blockage of the subcommissural organ-Reissner's fiber (RF) complex by maternal transfer of anti-RF antibodies.

Stenosis of the cerebral aqueduct seems to be a key event for the development of congenital hydrocephalus. The causes of such a stenosis are not well known. Overholser et al. in 1954 (Anat Rec 120:917-933) proposed the hypothesis that a dysfunction of the subcommissural organ (SCO) leads to aqueductal stenosis and congenital hydrocephalus. The SCO is a brain gland, located at the entrance of the cerebral aqueduct, that secretes glycoproteins into the cerebrospinal fluid that, upon release, assemble into a fibrous structure known as Reissner's fiber (RF). By the permanent addition of new molecules to its rostral end, RF grows and extends along the aqueduct, fourth ventricle, and central canal of the spinal cord. The immunological blockage of the SCO-RF complex has been used to test Overholser's hypothesis. The following was the sequence of events occurring in pregnant rats that had been immunized with RF glycoproteins: the mother produced anti-RF antibodies and transferred them to the fetus through the placenta and to the pup through the milk, and the antibodies reached the brain of the fetus and pup and blocked the SCO-RF complex. This resulted in a permanent absence of RF that was followed by stenosis of the cerebral aqueduct, and then by the appearance of hydrocephalus. The latter was patent until the end of the 6-month observation period. The chronic hydrocephalic state appeared, in turn, to induce new alterations of the SCO. It is concluded that a selective immunological knock out of the SCO-RF complex leads to hydrocephalus.

HLA-class II genes modify outcome of Toxoplasma gondii infection.

Associations between Human Leukocyte Antigen (HLA) (i.e. human major histocompatibility complex [MHC]) genes and susceptibility to infections and inflammatory processes have been described, but causal relationships have not been proven. We characterized effects of HLA-DQ alleles on outcome of congenital toxoplasma infection and found that among Caucasians, the DQ3 gene frequency was significantly higher in infected infants with hydrocephalus (0.783) than infected infants without hydrocephalus (0.444) or published normal controls (0.487). We then developed a novel animal model to definitively determine the effect of these HLA DQ molecules on the severity of toxoplasmosis. Human MHC-Class II transgenes reduced parasite burden and necrosis in brains of mice infected with Toxoplasma gondii. Consistent with the observed association between DQ3 and hydrocephalus in human infants, in the murine model the DQ3(DQ8; DQB1*0302) gene protected less than DQ1 (DQ6; DQB1*0601). Our findings definitively prove a cause and effect relationship between human MHC genes and resistance to infection, provide novel means to characterise human immune responses that are protective or pathogenic in infections, and are important for vaccine development.