Search

Neurocysticercosis (NCC) is one of the most common helminth parasitic diseases of the central nervous system (CNS) and the leading cause of acquired epilepsy worldwide. NCC is caused by the presence of the metacestode larvae of the tapeworm Taenia solium within brain tissues. NCC patients exhibit a long asymptomatic phase followed by a phase of symptoms including increased intra-cranial pressure and seizures. While the asymptomatic phase is attributed to the immunosuppressive capabilities of viable T. solium parasites, release of antigens by dying organisms induce strong immune responses and associated symptoms. Previous studies in T. solium-infected pigs have shown that the inflammatory response consists of various leukocyte populations including eosinophils, macrophages, and T cells among others. Because the role of eosinophils within the brain has not been investigated during NCC, we examined parasite burden, disease susceptibility and the composition of the inflammatory reaction in the brains of infected wild type (WT) and eosinophil-deficient mice (ΔdblGATA) using a murine model of NCC in which mice were infected intracranially with Mesocestoides corti, a cestode parasite related to T. solium. In WT mice, we observed a time-dependent induction of eosinophil recruitment in infected mice, contrasting with an overall reduced leukocyte infiltration in ΔdblGATA brains. Although, ΔdblGATA mice exhibited an increased parasite burden, reduced tissue damage and less disease susceptibility was observed when compared to infected WT mice. Cellular infiltrates in infected ΔdblGATA mice were comprised of more mast cells, and αβ T cells, which correlated with an abundant CD8+ T cell response and reduced CD4+ Th1 and Th2 responses. Thus, our data suggest that enhanced inflammatory response in WT mice appears detrimental and associates with increased disease susceptibility, despite the reduced parasite burden in the CNS. Overall reduced leukocyte infiltration due to absence of eosinophils correlates with attenuated tissue damage and longer survival of ΔdblGATA mice. Therefore, our study suggests that approaches to clear NCC will require strategies to tightly control the host immune response while eradicating the parasite with minimal damage to brain tissue.

Neurocysticercosis (NCC) is a central nervous system (CNS) infection caused by the metacestode stage of the parasite Taenia solium. During NCC, the parasites release immunodominant glycan antigens in the CNS environment, invoking immune responses. The majority of the associated pathogenesis is attributed to the immune response against the parasites. Glycans from a number of pathogens, including helminths, act as pathogen-associated molecular pattern molecules (PAMPs), which are recognized by pattern recognition receptors (PRRs) known as C-type lectin receptors (CLRs). Using a mouse model of NCC by infection with the related parasite Mesocestoides corti, we have investigated the role of mannose receptor C type 1 (MRC1), a CLR which recognizes high-mannose-containing glycan antigens. Here we show that MRC1(-/-) mice exhibit increased survival times after infection compared with their wild-type (WT) counterparts. The decreased disease severity correlates with reduced levels of expression of markers implicated in NCC pathology, such as interleukin-1β (IL-1β), IL-6, CCL5, and matrix metalloproteinase 9 (MMP9), in addition to induction of an important repair marker, fibroblast growth factor 2 (FGF2). Furthermore, the immune cell subsets that infiltrate the brain of MRC1(-/-) mice are dramatically altered and characterized by reduced numbers of T cells and the accumulation of granulocytic cells with an immune phenotype resembling granulocytic myeloid-dependent suppressor cells (gMDSCs). The results suggest that MRC1 plays a critical role in myeloid plasticity, which in turn affects the adaptive immune response and immunopathogenesis during murine NCC.

In murine neurocysticercosis (NCC), caused by infection with the parasite Mesocestoides corti, the breakdown of the Blood Brain Barrier (BBB) and associated leukocyte infiltration into the CNS is dependent on the anatomical location and type of vascular bed. Prior studies of NCC show that the BBB comprised of pial vessels are most affected in comparison to the BBB associated with the vasculature of other compartments, particularly parenchymal vessels. Herein, we describe a comprehensive study to characterize infection-induced changes in the genome wide gene expression of pial vessels using laser capture microdissection microscopy (LCM) combined with microarray analyses. Of the 380 genes that were found to be affected, 285 were upregulated and 95 were downregulated. Ingenuity Pathway Analysis (IPA) software was then used to assess the biological significance of differentially expressed genes. The most significantly affected networks of genes were "inflammatory response, cell-to-cell signaling and interaction, cellular movement", "cellular movement, hematological system development and function, immune cell trafficking, and "antimicrobial response, cell-to-cell signaling and interaction embryonic development". RT-PCR analyses validated the pattern of gene expression obtained from microarray analysis. In addition, chemokines CCL5 and CCL9 were confirmed at the protein level by immunofluorescence (IF) microscopy. Our data show altered gene expression related to immune and physiological functions and collectively provide insight into changes in BBB disruption and associated leukocyte infiltration during murine NCC.

Sepsis is a complex immune disorder with a mortality rate of 20-50% and currently has no therapeutic interventions. It is thus critical to identify and characterize molecules/factors responsible for its development. We have recently shown that pulmonary infection with Francisella results in sepsis development. As extensive cell death is a prominent feature of sepsis, we hypothesized that host endogenous molecules called alarmins released from dead or dying host cells cause a hyperinflammatory response culminating in sepsis development. In the current study we investigated the role of galectin-3, a mammalian β-galactoside binding lectin, as an alarmin in sepsis development during F. novicida infection. We observed an upregulated expression and extracellular release of galectin-3 in the lungs of mice undergoing lethal pulmonary infection with virulent strain of F. novicida but not in those infected with a non-lethal, attenuated strain of the bacteria. In comparison with their wild-type C57Bl/6 counterparts, F. novicida infected galectin-3 deficient (galectin-3(-/-)) mice demonstrated significantly reduced leukocyte infiltration, particularly neutrophils in their lungs. They also exhibited a marked decrease in inflammatory cytokines, vascular injury markers, and neutrophil-associated inflammatory mediators. Concomitantly, in-vitro pre-treatment of primary neutrophils and macrophages with recombinant galectin-3 augmented F. novicida-induced activation of these cells. Correlating with the reduced inflammatory response, F. novicida infected galectin-3(-/-) mice exhibited improved lung architecture with reduced cell death and improved survival over wild-type mice, despite similar bacterial burden. Collectively, these findings suggest that galectin-3 functions as an alarmin by augmenting the inflammatory response in sepsis development during pulmonary F. novicida infection.

Background: Central nervous system (CNS) barriers play a pivotal role in the protection and homeostasis of the CNS by enabling the exchange of metabolites while restricting the entry of xenobiotics, blood cells and blood-borne macromolecules. While the blood-brain barrier and blood-cerebrospinal fluid barrier (CSF) control the interface between the blood and CNS, the ependyma acts as a barrier between the CSF and parenchyma, and regulates hydrocephalic pressure and metabolic toxicity. Neurocysticercosis (NCC) is an infection of the CNS caused by the metacestode (larva) of Taenia solium and a major cause of acquired epilepsy worldwide. The common clinical manifestations of NCC are seizures, hydrocephalus and symptoms due to increased intracranial pressure. The majority of the associated pathogenesis is attributed to the immune response against the parasite. The properties of the CNS barriers, including the ependyma, are affected during infection, resulting in disrupted homeostasis and infiltration of leukocytes, which correlates with the pathology and disease symptoms of NCC patients., Results: In order to characterize the role of the ependymal barrier in the immunopathogenesis of NCC, we isolated ependymal cells using laser capture microdissection from mice infected or mock-infected with the closely related parasite Mesocestoides corti, and analyzed the genes that were differentially expressed using microarray analysis. The expression of 382 genes was altered. Immune response-related genes were verified by real-time RT-PCR. Ingenuity Pathway Analysis (IPA) software was used to analyze the biological significance of the differentially expressed genes, and revealed that genes known to participate in innate immune responses, antigen presentation and leukocyte infiltration were affected along with the genes involved in carbohydrate, lipid and small molecule biochemistry. Further, MHC class II molecules and chemokines, including CCL12, were found to be upregulated at the protein level using immunofluorescence microscopy. This is important, because these molecules are members of the most significant pathways by IPA analyses., Conclusion: Thus, our study indicates that ependymal cells actively express immune mediators and likely contribute to the observed immunopathogenesis during infection. Of particular interest is the major upregulation of antigen presentation pathway-related genes and chemokines/cytokines. This could explain how the ependyma is a prominent source of leukocyte infiltration into ventricles through the disrupted ependymal lining by way of pial vessels present in the internal leptomeninges in murine NCC.

Neurocysticercosis is a serious zoonotic diseas, encountered worldwide, caused by the larval stage of Taenia solium. Due to the difficulties facing scientists to study the biological, histological and immunological effects of these larvae on the human brain, other cestodes with more or less similar larvae (Taenia crassiceps) were used. In brain infected mice, Th1 predominant cytokines were significantly detected.

In a murine model for neurocysticercosis (NCC), intracranial inoculation of the helminth parasite Mesocestoides corti induces multiple Toll-like receptors (TLRs), among which TLR2 is upregulated first and to a relatively high extent. Here, we report that TLR2(-/-) mice displayed significantly increased susceptibility to parasite infection accompanied by increased numbers of parasites in the brain parenchyma compared to infection in wild-type (WT) mice. This coincided with an increased display of microglial nodule formations and greater neuropathology than in the WT. Parasite-infected TLR2(-/-) brains exhibited a scarcity of lymphocytic cuffing and displayed reduced numbers of infiltrating leukocytes. Fluorescence-activated cell sorter (FACS) analyses revealed significantly lower numbers of CD11b(+) myeloid cells, γδ T cells, αβ T cells, and B cells in the brains of parasite-infected TLR2(-/-) mice. This correlated with significantly reduced levels of inflammatory mediators, including tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), CCL2, CCL3, and interleukin-6 (IL-6) in the central nervous system (CNS) of TLR2(-/-) mice. As TLR2 has been implicated in immune regulation of helminth infections and as alternatively activated macrophages (AAMs) are thought to play a profound regulatory role in such infections, induction of AAMs in infected TLR2(-/-) mice was compared with that in WT mice. Parasite-infected WT brains showed larger numbers of macrophages/microglia (CD11b(+) cells) expressing AAM-associated molecules such as YM1, Fizz1 (found in inflammatory zone-1 antigen), and arginase 1 than TLR2(-/-) brains, consistent with a protective role of AAMs during infection. Importantly, these results demonstrate that TLR2-associated responses modulate the disease severity of murine NCC.

The virulence mechanisms of Francisella tularensis, the causative agent of severe pneumonia in humans and a CDC category A bioterrorism agent, are not fully defined. As sepsis is the leading cause of mortality associated with respiratory infections, we determined whether, in the absence of any known bacterial toxins, a deregulated host response resulting in sepsis syndrome is associated with lethality of respiratory infection with the virulent human Type A strain SchuS4 of F. tularensis. The C57BL/6 mice infected intranasally with a lethal dose of SchuS4 exhibited high bacterial burden in systemic organs and blood indicative of bacteremia. In correlation, infected mice displayed severe tissue pathology and associated cell death in lungs, liver and spleen. Consistent with our studies with murine model strain Francisella novicida, infection with SchuS4 caused an initial delay in upregulation of inflammatory mediators followed by development of severe sepsis characterized by exaggerated cytokine release, upregulation of cardiovascular injury markers and sepsis mediator alarmins S100A9 and HMGB1. This study shows that pulmonary tularemia caused by the Type A strain of F. tularensis results in a deregulated host response leading to severe sepsis and likely represents the major cause of mortality associated with this virulent pathogen., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

In this study, using a murine model for neurocysticercosis, macrophage phenotypes and their functions were examined. Mesocestoides corti infection in the central nervous system (CNS) induced expression of markers associated with alternatively activated macrophages (AAMs) and a scarcity of iNOS, a classically activated macrophage marker. The infection in STAT6(-/-) mice resulted in significantly reduced accumulation of AAMs as well as enhanced susceptibility to infection coinciding with increased parasite burden and greater neuropathology. These results demonstrate that macrophages in the helminth infected CNS are largely of AAM phenotypes, particularly as the infection progresses, and that STAT6 dependent responses, possibly involving AAMs, are essential for controlling neurocysticercosis., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The macrophage is a versatile cell type that can sense and respond to a particular need based on the conditions of the microenvironment. Some studies have recently suggested that pathogens can directly influence the polarization of macrophages. As Francisella infections are characterized by intense necrotic infiltrates in the lung as well as in distal sites of infection, we sought to investigate whether pulmonary Francisella infections could cause the polarization of alternatively activated macrophages (M2/aaMs). Our results indicate that Francisella infections can cause the polarization of M2/aaM in vivo and that macrophages can be polarized toward an M2/aaM phenotype more potently if dead cell debris is used for stimulation in the presence and absence of Francisella infections. Finally, we also demonstrate that efferocytosis is inhibited in macrophages infected with Francisella, thus providing a potential explanation for the lack of clearance and eventual accumulation of dead cell debris associated with this disease.

The bacterial determinants of pulmonary Francisella induced inflammatory responses and their interaction with host components are not clearly defined. In this study, proteomic and immunoblot analyses showed presence of a cytoplasmic protein elongation factor Tu (EF-Tu) in the membrane fractions of virulent Francisella novicida, LVS and SchuS4, but not in an attenuated F. novicida mutant. EF-Tu was immunodominant in mice vaccinated and protected from virulent F. novicida. Moreover, recombinant EF-Tu induced macrophages to produce inflammatory cytokines in a TLR4 dependent manner. This study shows immune stimulatory properties of a cytoplasmic protein EF-Tu expressed on the membrane of virulent Francisella strains., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Background: Pneumonia and pulmonary infections are major causes of mortality among the growing elderly population. Age associated attenuations of various immune parameters, involved with both innate and adaptive responses are collectively known as immune senescence. These changes are likely to be involved with differences in host susceptibility to disease between young and aged individuals., Methodology/principal Findings: The objective of this study was to assess potential age related differences in the pulmonary host response in mice to the Gram-negative respiratory pathogen, Francisella novicida. We intranasally infected mice with F. novicida and compared various immune and pathological parameters of the pulmonary host response in both young and aged mice., Conclusions/significance: We observed that 20% of aged mice were able to survive an intranasal challenge with F. novicida while all of their younger cohorts died consistently within 4 to 6 days post infection. Further experiments revealed that all of the aged mice tested were initially able to control bacterial replication in the lungs as well as at distal sites of replication compared with young mice. In addition, the small cohort of aged survivors did not progress to a severe sepsis syndrome with hypercytokinemia, as did all of the young adult mice. Finally, a lack of widespread cell death in potential aged survivors coupled with a difference in cell types recruited to sites of infection within the lung confirmed an altered host response to Francisella in aged mice.

Neurocysticercosis (NCC) is the most common parasitic disease of the central nervous system (CNS) caused by the larval form of the tapeworm Taenia solium. NCC has a long asymptomatic period with little or no inflammation, and the sequential progression to symptomatic NCC depends upon the intense inflammation associated with degeneration of larvae. The mechanisms involved in these progressive events are difficult to study in human patients. Thus it was necessary to develop an experimental model that replicated NCC. In this review, we describe studies of a murine model of NCC in terms of the release/secretion of parasite antigens, immune responses elicited within the CNS environment and subsequent pathogenesis. In particular, the kinetics of leukocyte subsets infiltrating into the brain are discussed in the context of disruption of the CNS barriers at distinct anatomical sites and the mechanisms contributing to these processes. In addition, production of various inflammatory mediators and the mechanisms involved in their induction by the Toll-like receptor signaling pathway are described. Overall, the knowledge gained from the mouse model of NCC has provided new insights for understanding the kinetics of events contributing to different stages of NCC and should aid in the formulation of more effective therapeutic approaches.

Aging is a complex phenomenon that has been shown to affect many organ systems including the innate and adaptive immune systems. The current study was designed to examine the potential effect of immunosenescence on the pulmonary immune response using a Francisella tularensis live vaccine strain (LVS) inhalation infection model. F. tularensis is a Gram-negative intracellular pathogen that can cause a severe pneumonia. In this study both young (8-12 week old) and aged (20-24 month old) mice were infected intranasally with LVS. Lung tissues from young and aged mice were used to assess pathology, recruitment of immune cell types and cytokine expression levels at various times post infection. Bacterial burdens were also assessed. Interestingly, the lungs of aged animals harbored fewer organisms at early time points of infection (day 1, day 3) compared with their younger counterparts. In addition, only aged animals displayed small perivascular aggregates at these early time points that appeared mostly mononuclear in nature. However, the kinetics of infiltrating polymorphonuclear neutrophils (PMNs) and increased cytokine levels measured in the bronchial alveolar lavage fluid (BALF) were delayed in infected aged animals relative to young infected animals with neutrophils appearing at day 5 post infection (PI) in the aged animals as opposed to day 3 PI in the young infected animals. Also evident were alterations in the ratios of mononuclear to PMNs at distinct post infection times. The above evidence indicates that aged mice elicit an altered immune response in the lung to respiratory F. tularensis LVS infections compared to their younger counterparts., (Copyright (c) 2009 Elsevier Inc. All rights reserved.)

The symptomatic phase of neurocysticercosis (NCC), a parasitic disease of the central nervous system (CNS) in humans, is characterized by inflammatory responses leading to neuropathology and, in some cases, death. In an animal model of NCC in which mice were intracranially inoculated with the parasite Mesocestoides corti, the infection in mice lacking the myeloid differentiation primary response gene 88 (MyD88(-/-)) resulted in decreased disease severity and improved survival compared with that in wild-type (WT) mice. The CNS of MyD88(-/-) mice was more quiescent, with decreased microgliosis and tissue damage. These mice exhibited substantially reduced primary and secondary microglial nodule formations and lacked severe astrogliotic reactions, which were seen in WT mice. Significantly reduced numbers of CD11b(+) myeloid cells, alphabeta T cells, gammadelta T cells, and B cells were present in the brains of MyD88(-/-) mice in comparison with those of WT mice. This decrease in cellular infiltration correlated with a decrease in blood-brain barrier permeability, as measured by reduced fibrinogen extravasation. Comparisons of cytokine expression indicated a significant decrease in the CNS levels of several inflammatory mediators, such as tumor necrosis factor alpha, gamma interferon, CCL2, and interleukin-6, during the course of infection in MyD88(-/-) mice. Collectively, these findings suggest that MyD88 plays a prominent role in the development of the hyperinflammatory response, which in turn contributes to neuropathology and disease severity in NCC.

Background: Francisella tularensis is the causative agent of tularemia and is classified as a Category A select agent. Recent studies have implicated TLR2 as a critical element in the host protective response to F. tularensis infection, but questions remain about whether TLR2 signaling dominates the response in all circumstances and with all species of Francisella and whether F. tularensis PAMPs are predominantly recognized by TLR2/TLR1 or TLR2/TLR6. To address these questions, we have explored the role of Toll-like receptors (TLRs) in the host response to infections with F. tularensis Live Vaccine Strain (LVS) and F. tularensis subspecies (subsp.) novicida in vivo., Methodology/principal Findings: C57BL/6 (B6) control mice and TLR- or MyD88-deficient mice were infected intranasally (i.n.) or intradermally (i.d.) with F. tularensis LVS or with F. tularensis subsp. novicida. B6 mice survived >21 days following infection with LVS by both routes and survival of TLR1(-/-), TLR4(-/-), and TLR6(-/-) mice infected i.n. with LVS was equivalent to controls. Survival of TLR2(-/-) and MyD88(-/-) mice, however, was significantly reduced compared to B6 mice, regardless of the route of infection or the subspecies of F. tularensis. TLR2(-/-) and MyD88(-/-) mice also showed increased bacterial burdens in lungs, liver, and spleen compared to controls following i.n. infection. Primary macrophages from MyD88(-/-) and TLR2(-/-) mice were significantly impaired in the ability to secrete TNF and other pro-inflammatory cytokines upon ex vivo infection with LVS. TNF expression was also impaired in vivo as demonstrated by analysis of bronchoalveolar lavage fluid and by in situ immunofluorescent staining., Conclusions/significance: We conclude from these studies that TLR2 and MyD88, but not TLR4, play critical roles in the innate immune response to F. tularensis infection regardless of the route of infection or the subspecies. Moreover, signaling through TLR2 does not depend exclusively on TLR1 or TLR6 during F. tularensis LVS infection.

Francisella tularensis is the causative agent of zoonotic tularemia, a severe pneumonia in humans, and Francisella novicida causes a similarly severe tularemia in mice upon inhalation. The correlates of protective immunity, as well as the virulence mechanisms of this deadly pathogen, are not well understood. In the present study, we compared the host immune responses of lethally infected and vaccinated mice to highlight the host determinants of protection from this disease. Intranasal infection with an attenuated mutant (Mut) of F. novicida lacking a 58-kDa hypothetical protein protected C57BL/6 mice from a subsequent challenge with the fully virulent wild-type strain U112 via the same route. The protection conferred by Mut vaccination was associated with reduced bacterial burdens in systemic organs, as well as the absence of bacteremia. Also, there was reduced lung pathology and associated cell death in the lungs of vaccinated mice. Both vaccinated and nonvaccinated mice displayed an initial 2-day delay in upregulation of signature inflammatory mediators after challenge. Whereas the nonvaccinated mice developed severe sepsis characterized by hypercytokinemia and T-cell depletion, the vaccinated mice displayed moderated cytokine induction and contained increased numbers of alphabeta T cells. The recall response in vaccinated mice consisted of a characteristic Th1-type response in terms of cytokines, as well as antibody isotypes. Our results show that a regulated Th1 type of cell-mediated and humoral immunity in the absence of severe sepsis is associated with protection from respiratory tularemia, whereas a deregulated host response leading to severe sepsis contributes to mortality.

The bacterial or host determinants of lethality associated with respiratory Francisella infections are currently unknown. No exo- or endotoxins that contribute to the severity of this disease have been identified. However, a deregulated host immune response upon infection is characterized by an initial 36- to 48-h delay followed by a rapid and excessive inflammatory response prior to death at 72-120 h. Here, we extend these findings by comparing host immune responses between sublethal and lethal respiratory infections of mice with an attenuated transposon mutant (Mut) of F. novicida (F.n.) strain U112 (sublethal) versus the wild-type (WT) strain (lethal). Infection with WT bacteria, but not the Mut, was characterized by sustained bacteremia and systemic dissemination of the pathogen with temporal increases in bacterial burdens in liver and spleen. Severe pathology with large foci of infiltrates associated with extensive tissue damage was evident in WT-infected lungs, and Mut-infected mice displayed much reduced pathology with intact lung architecture. Similar to other experimental models of severe sepsis, WT- but not the Mut-infected mice exhibited a robust increase in numbers of Gr1+ and CD11b+ cells, while displaying a significant depletion of alphabeta T cells. Further, a dramatic up-regulation of multiple cytokines and chemokines was observed only in lethal WT infection. In addition, an earlier and larger increased expression of S100A9, a known mediator of sepsis, was observed in WT-infected mice. Taken together, these results show that a hyperinflammatory host immune response, culminating in severe sepsis, is responsible for the lethal outcome of respiratory tularemia.

Murine neurocysticercosis is a parasitic infection transmitted through the direct ingestion of Taenia solium eggs, which differentially disrupts the barriers that protect the microenvironment of the central nervous system. Among the host factors that are involved in this response, matrix metalloproteinases (MMPs) have been recently described as important players. Doxycycline is a commonly prescribed antimicrobial drug that acts as an anti-inflammatory agent with broad inhibitory properties against MMPs. In this study, we examined the effects of doxycycline treatment in a murine model of neurocysticercosis. Animals treated with doxycycline exhibited reduced morbidity and mortality throughout the course of infection. Although similar levels of leukocyte infiltration were observed with both treatment regimens, doxycycline appeared to provide improved conditions for host survival, as reduced levels of apoptosis were detected among infiltrates as well as in neurons. As an established MMP blocker, doxycycline reduced the degradation of junctional complex proteins in parenchymal vessels. In addition, doxycycline treatment was associated with an overall reduction in the expression and activity of MMPs, particularly in areas of leukocyte infiltration. These results indicate that a broad-range inhibitor of MMPs promotes host survival and suggest the potential of doxycycline as a therapeutic agent for the control of inflammatory responses associated with neurocysticercosis.

Parasite infections in the central nervous system (CNS) are a major cause of morbidity and mortality worldwide, second only to HIV infection. Finding appropriate therapeutic measures to control CNS parasite infections requires an understanding of the tissue-specific host response. CNS parasitic diseases are invariably associated with persistent T-helper 1 (Th1) cytokine-dependent proinflammatory responses. Although type 1 cytokine-dependent proinflammatory responses are essential to control several types of parasite infections, their persistent production contributes to the development of neuropathology with severe consequences. A family of proteins called Toll-like receptors (TLRs) plays a pivotal role in the induction of inflammatory cytokines during infections and tissue injury. Accumulating evidence indicates that in several CNS parasitic infections such as toxoplasmosis and sleeping sickness, host responses mediated through TLRs contribute to parasite clearance and host survival. However, TLR-mediated responses can also contribute to disease severity, as exemplified in cerebral malaria, neurocysticercosis and river blindness. Thus, TLRs influence the immunopathogenesis of CNS parasitic infections by mechanisms that can either benefit the host or further contribute to CNS pathology. This chapter discusses the immunopathogenesis of parasitic infections in the CNS and the role of TLRs in this process.

Respiratory Francisella infections induce a delayed innate immune response followed by a severe sepsis like condition. In this study, mice infected intranasally with Francisella novicida showed a depletion of alphabeta T cells in lungs while exhibiting large accumulations of other leukocytes correlating with disease severity. The depleted T cells were predominantly CD4(+). The alphabeta T cells in infected mice showed significantly higher levels of Annexin V binding than those in mock control mice suggesting increased apoptosis of T cells. These results suggest that lack of transition from an innate to adaptive host response is associated with lethality of respiratory tularemia.

The functions of Toll-like receptors (TLRs) 11-13 in central nervous system (CNS) infections are currently unknown. Using a murine model of neurocysticercosis, we investigated the expression and distribution of TLRs 11-13 by using both gene specific real-time PCR analysis and in situ immunofluorescence microscopy in both control and neurocysticercosis brains. In the mock infected brain, mRNAs of TLRs 11-13 were constitutively expressed. Parasite infection caused an increase of both mRNAs and protein levels of all three TLRs by several fold. All three TLR proteins were present in both CNS and immune cell types. Among them TLR13 was expressed the most in terms of number of positive cells and brain areas expressing it, followed by TLR11 and TLR12 respectively. Among the nervous tissue cells, TLRs 11-13 protein levels appeared highest in neurons. However, TLR13 expression was also present in ependymal cells, endothelial cells of pial blood vessels, and astrocytes. In contrast, infiltrating CD11b and CD11c positive myeloid cells predominantly produced TLR11 protein, particularly early during infection at 1 wk post infection (approximately 50% cells). TLRs 12 and 13 proteins were present on approximately 5% of infiltrating immune cells. The infiltrating cells positive for TLRs 11-13 were mostly of myeloid origin, CD11b+ cells. This report provides a comprehensive analysis of the expression of TLRs 11-13 in normal and parasite infected mouse brains and suggests a role for them in CNS infections.

Background: Francisella tularensis subsp. tularensis is classified as a Category A bioweapon that is capable of establishing a lethal infection in humans upon inhalation of very few organisms. However, the virulence mechanisms of this organism are not well characterized. Francisella tularensis subsp. novicida, which is an equally virulent subspecies in mice, was used in concert with a microPET scanner to better understand its temporal dissemination in vivo upon intranasal infection and how such dissemination compares with other routes of infection. Adult mice were inoculated intranasally with F. tularensis subsp. novicida radiolabeled with 64Cu and imaged by microPET at 0.25, 2 and 20 hours post-infection., Results: 64Cu labeled F. tularensis subsp. novicida administered intranasally or intratracheally were visualized in the respiratory tract and stomach at 0.25 hours post infection. By 20 hours, there was significant tropism to the lung compared with other tissues. In contrast, the images of radiolabeled F. tularensis subsp. novicida when administered intragastrically, intradermally, intraperitoneally and intravenouslly were more generally limited to the gastrointestinal system, site of inoculation, liver and spleen respectively. MicroPET images correlated with the biodistribution of isotope and bacterial burdens in analyzed tissues., Conclusion: Our findings suggest that Francisella has a differential tissue tropism depending on the route of entry and that the virulence of Francisella by the pulmonary route is associated with a rapid bacteremia and an early preferential tropism to the lung. In addition, the use of the microPET device allowed us to identify the cecum as a novel site of colonization of Francisella tularensis subsp. novicida in mice.

"Francisella tularensis subsp. novicida" intranasal infection causes a rapid pneumonia in mice with mortality at 4 to 6 days with a low dose of bacteria (10(2) bacteria). The short time to death suggests that there is a failure of the innate immune response. As the neutrophil is often the first cell type to infiltrate sites of infection, we focused on the emigration of neutrophils in this infection, as well as cytokines involved in their recruitment. The results indicated that there was a significant delay in the influx of neutrophils into the bronchoalveolar lavage fluid of F. tularensis subsp. novicida-infected mice. The delay in neutrophil recruitment in F. tularensis subsp. novicida-infected mice correlated with a delay in the upregulation of multiple proinflammatory cytokines and chemokines, as well as a delay in caspase-1 activation. Strikingly, the initial delay in the upregulation of cytokines through 1 day postinfection was followed by profound upregulation of multiple cytokines and chemokines to levels consistent with hypercytokinemia described for severe sepsis. This finding was further supported by a bacteremia and the cellular relocalization and release of high-mobility group box-1 and S100A9, both of which are damage-associated molecular pattern molecules and are known to be mediators of severe sepsis.

During the course of murine neurocysticercosis (NCC), disruption of the unique protective barriers in the central nervous system (CNS) is evidenced by extravasation of leukocytes. This process varies according to the anatomical sites and diverse vascular beds analyzed. To examine mechanisms involved in the observed differences, the expression and activity of eight matrix metalloproteinases (MMPs) were analyzed in a murine model of NCC. The mRNA expression of the MMPs studied was upregulated as a result of infection, and active MMPs were mainly detected in leukocytes migrating into the brain. Polarized expression and gelatinolytic activity of several MMPs were identified in immune cells extravasating pial vessels as early as 1 day post infection. In contrast, leukocytes expressing active MMPs and extravasating parenchymal vessels were not observed until 5 weeks post infection. In ventricular areas, most of the MMP activity was detected in leukocytes traversing the ependyma from leptomeningeal infiltrates. In addition, immune cells continued to express active MMPs after exiting vessels suggesting that enzymatic activity of MMPs is not just required for diapedesis. These results correlate with our previous studies showing differential kinetics in the disruption of the CNS barriers upon infection and help document the important role of MMPs during leukocyte infiltration and inflammation.

Neurocysticercosis (NCC) is an infection of the central nervous system (CNS) by the metacestode of the helminth Taenia solium. The severity of the symptoms is associated with the intensity of the immune response. First, there is a long asymptomatic period where host immunity seems incapable of resolving the infection, followed by a chronic hypersensitivity reaction. Since little is known about the initial response to this infection, a murine model using the cestode Mesocestoides corti (syn. Mesocestoides vogae) was employed to analyze morphological changes in the parasite early in the infection. It was found that M. corti material is released from the tegument making close contact with the nervous tissue. These results were confirmed by infecting murine CNS with ex vivo-labeled parasites. Because more than 95% of NCC patients exhibit humoral responses against carbohydrate-based antigens, and the tegument is known to be rich in glycoconjugates (GCs), the expression of these types of molecules was analyzed in human, porcine, and murine NCC specimens. To determine the GCs present in the tegument, fluorochrome-labeled hydrazides as well as fluorochrome-labeled lectins with specificity to different carbohydrates were used. All the lectins utilized labeled the tegument. GCs bound by isolectinB4 were shed in the first days of infection and not resynthesized by the parasite, whereas GCs bound by wheat germ agglutinin and concavalinA were continuously released throughout the infectious process. GCs bound by these three lectins were taken up by host cells. Peanut lectin-binding GCs, in contrast, remained on the parasite and were not detected in host cells. The parasitic origin of the lectin-binding GCs found in host cells was confirmed using antibodies against T. solium and M. corti. We propose that both the rapid and persistent release of tegumental GCs plays a key role in the well-known immunomodulatory effects of helminths, including immune evasion and life-long inflammatory sequelae seen in many NCC patients.

The delicate balance required to maintain homeostasis of the central nervous system (CNS) is controlled by the blood-brain barrier (BBB). Upon injury, the BBB is disrupted compromising the CNS. BBB disruption has been represented as a uniform event. However, our group has shown in a murine model of neurocysticercosis (NCC) that BBB disruption varies depending upon the anatomical site/vascular bed analyzed. In this study further understanding of the mechanisms of BBB disruption was explored in blood vessels located in leptomeninges (pial vessels) and brain parenchyma (parenchymal vessels) by examining the expression of junctional complex proteins in murine brain infected with Mesocestoides corti. Both pial and parenchymal vessels from mock infected animals showed significant colocalization of junctional proteins and displayed an organized architecture. Upon infection, the patterned organization was disrupted and in some cases, particular tight junction and adherens junction proteins were undetectable or appeared to be undergoing proteolysis. The extent and timing of these changes differed between both types of vessels (pial vessel disruption within days versus weeks for parenchymal vessels). To approach potential mechanisms, the expression and activity of matrix metalloproteinase-9 (MMP-9) were evaluated by in situ zymography. The results indicated an increase in MMP-9 activity at sites of BBB disruption exhibiting leukocyte infiltration. Moreover, the timing of MMP activity in pial and parenchymal vessels correlated with the timing of permeability disruption. Thus, breakdown of the BBB is a mutable process despite the similar structure of the junctional complex between pial and parenchymal vessels and involvement of MMP activity.

The blood brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCB) limit the influx of immune mediators and bloodstream compounds into the central nervous system (CNS). Upon injury or infection, the integrity of these barriers is compromised and leukocyte infiltration occurs. The BCB is located in the choroid plexuses (CPs) found within ventricles of the brain, and it is considered one of the main routes of cellular infiltration into the CNS into healthy individuals. Our group recently showed that in a murine model of neurocysticercosis (NCC), there is a moderate increase in infiltration of leukocytes into ventricles, but the BCB is hardly compromised. To elucidate the role played by CPs and surrounding ependyma in leukocyte infiltration at ventricular sites, we analyzed changes in the expression of junctional complex proteins in animals intracranially infected with Mesocestoides corti. The results indicate that infection does not change the expression pattern of junctional complex proteins in CPs, but structural alterations and disappearance of these proteins were evident in ependyma adjacent to the internal leptomeninges. The kinetics and magnitude of these changes directly correlated with the extent of leukocyte infiltration through ependyma and with the expression and activity of MMPs. The results of this study indicate that the anatomical elements of the BCB are minimally disrupted during the course of murine NCC. Thus, most of the leukocytes infiltrating ventricles appear to extravasate through pial vessels located in the internal leptomeninges juxtaposed to the ependyma layer and then traverse the ependyma cells. In addition, MMP activity seems to be involved in this process. These results provide evidence for a previously undescribed entry route for leukocytes into the CNS.

In a mouse model of neurocysticercosis, the expression and distribution of Toll-like receptors (TLRs) was investigated by using both gene array analyses and in situ immunofluorescence microscopy (IF). In the normal uninfected brain, mRNA of all the TLRs are constitutively expressed albeit TLR5, TLR7, TLR8 and TLR9 to a lesser extent. In these animals, however, expression of TLR1, TLR3, TLR4 and TLR9 proteins was not detected. In contrast, parasite infection increased both gene and protein level expression of all the TLRs several fold except TLR5 where only the mRNA was upregulated. Importantly, TLRs were differentially distributed among various central nervous system (CNS) cell types and infiltrating leukocytes. TLR2 was almost exclusively localized to nervous tissue cells, particularly astrocytes, while TLR1 and TLR9 proteins were essentially limited to infiltrating leukocytes. All other TLRs tested were detected in both CNS and immune cell types. Interestingly, ependymal cells and neurofilaments of the cerebellar white matter of infected mice exhibited a substantial upregulation of TLR7 and TLR8 proteins respectively. These data provide a comprehensive analysis of TLR expression in the normal and parasite infected brain and suggest a role for TLRs in the interplay of immune cells and CNS cells during infection.

Brain homeostasis is normally protected by the blood brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCB), barriers that function in distinct CNS compartments and consist of different types of blood vessels including pial (subarachnoid spaces, leptomeninges), parenchymal (cerebral cortex) and ventricular vessels. In this study, a mouse model of neurocysticercosis was used to distinguish between changes in the permeability of the BBB and the BCB and determine the association of such alterations on leukocyte infiltration. Mice were intracranially infected with the parasite Mesocestoides corti and sacrificed at various times post infection. Different anatomical areas of infected brain were analyzed by three color immunofluoresence utilizing antibodies against serum proteins to assess brain barrier permeability, glial fibrillary acidic protein (GFAP) to detect astrocytes, and specific cell surface markers to determine the subpopulations of leukocytes infiltrating the CNS at particular sites. The results indicate increased permeability of all three types of vessels/structural sites as a result of infection evidenced by serum proteins and leukocyte extravasation but with considerable differences in the timing and extent of these permeability changes. Parenchymal vessels were the most resilient to changes in permeability whereas pial vessels were the least. Choroid plexus vessels of the ventricles also appeared less susceptible to increased permeability compared with pial vessels. In addition, parenchymal vessels appeared impermeable to particular types of immune cells even after extended periods of infection. Additionally, alterations in reactive astrocytes juxtaposed to blood vessels that exhibited increased permeability displayed increased expression of cytokines known to regulate brain barrier function. The results suggest that access of leukocytes and serum derived factors into the infected brain depend on several parameters including the anatomical area, type of vascular bed, cell phenotype and cytokine microenvironment.

Francisella tularensis is a highly virulent facultative intracellular bacterium and is considered a potential biological warfare agent. Inhalation tularemia can lead to the development of bronchopneumonia, which is frequently fatal without medical intervention. Treatment strategies that directly target the respiratory mucosa may extend the efficacy of therapy, particularly for the medical management of acute aerosol exposure. To this end, we describe an intranasal (i.n.) strategy for the treatment of pulmonary Francisella infection in mice that uses a combinatorial approach with the conventional antibiotic gentamicin and interleukin 12 (IL-12). The i.n. administration of IL-12 alone promoted bacterial clearance and extended the time to death but did not prevent mortality against lethal pulmonary challenge with Francisella tularensis subsp. novicida. However, i.n. treatment with gentamicin and IL-12 therapeutically at 8 and 24 h after challenge markedly enhanced the rate of survival (70 to 100%) against pulmonary infection compared to the rates of survival for animals treated with antibiotic alone (17%) or IL-12 alone (0%). A delay in combinatorial therapy over a span of 4 days progressively decreased the efficacy of this treatment regimen. This combinatorial treatment was shown to be highly dependent upon the induction of endogenous gamma interferon and may also involve the activation of natural killer cells. Together, these findings suggest that IL-12 may be a potent adjunct for chemotherapy to enhance drug effectiveness against pulmonary Francisella infection.

Taenia solium has a complex life cycle. Its cysticercus can lodge in the brain, causing neurocysticercosis (NCC), and the adult tapeworm's survival in the intestine results in taeniasis. In this study, the in situ detection of previously described glycoprotein antigens used for serological diagnosis of NCC and the detection of other glycoconjugates was explored in cysticerci and the surrounding porcine tissue to understand their potential role in pathogenesis. Immunohistochemistry with an antiserum specific for glycoprotein antigens rich in N-linked carbohydrates and in situ histochemistry with a battery of lectins that have affinity to a variety of glycoconjugates were performed. The glycoconjugates rich in N-linked carbohydrates were detected in the vesicular fluid and tegument of the vesicular membrane and scolex, where the parasite has direct contact with the host tissues during cysticercosis and taeniasis, respectively. Additionally, as the inflammatory response progressed, the parasite's antigenic glycoproteins were also detected in the cytoplasm of inflammatory cells in the surrounding granuloma. In contrast, the spiral canal tegument, which will be exposed to intestinal enzymes in taeniasis, had N-acetyl-galactosamine-rich mucins. Thus, the differential saccharidic composition in T. solium metacestode structures may be important for the survival of the parasite in different host sites.

According to a previous report, the degree of the host immune response highly correlates with severity of the disease in the murine model for neurocysticercosis. In wild-type mice, Mesocestoides corti infection induced a rapid and extensive accumulation of gamma delta T cells and macrophages in the brain. NK cells, dendritic cells, alpha beta T cells, and B cells were also recruited to the brain but at lower levels. In contrast, gamma delta T-cell-deficient mice exhibited decreased cellular infiltration and reduced central nervous system (CNS) pathology. To understand the mechanisms of leukocyte recruitment into the CNS, chemokine expression was analyzed in infected brains in the present study. MCP-1 (CCL2), MIP-1 alpha (CCL3), and MIP-1 beta (CCL4) were up-regulated within 2 days after M. corti infection. Protein expression of RANTES (CCL5), eotaxin (CCL11), and MIP-2 was detected later, at 1 week postinfection. Correlating with the decreased cellular infiltration, delta chain T-cell receptor-deficient (TCR delta(-/-)) mice exhibited substantially reduced levels of most of the chemokines analyzed (with the exception of eotaxin). The results suggest that gamma delta T cells play an important role in the CNS immune response by producing chemokines such as MCP-1 and MIP-1 alpha, enhancing leukocyte trafficking into the brain during murine neurocysticercosis.

The detection of antibodies to Taenia solium metacestodes is very important in the differential diagnosis of neurocysticercosis (NCC). In this study, an electroimmunotransfer blot (EITB) assay that uses an elaborate protocol with metacestode glycoproteins as antigens was compared with two other Western blots that use glycoproteins obtained using simpler methods, including an eluate from a lectin column, or the vesicular fluid (VF) of the parasite. The concordance between the three assays was 91% in patients with active NCC and 100% in patients with suspected NCC and previous documentation of negative serology. The specificities for the Western blots and the EITB assay were 98% and 100%, respectively (98% concordance). These data suggest that the simplest of these immunoassays, the one that uses the VF of T. solium metacestodes in a Western blot format, can be reliably used for the serologic diagnosis of NCC in developing countries where access to the EITB assay is difficult.

In a recently developed mouse model for neurocysticercosis, the immune response was characterized by a massive influx of gammadelta T cells and a type 1 pathway of cytokine expression. To understand the role of gammadelta T cells during this infection, the cellular and cytokine response was analyzed in mice that lack gammadelta T cells (TCRdelta(-/-)). In TCRdelta(-/-) mice, Mesocestoides corti metacestodes preferentially invaded the extraparenchymal areas of the brain. Furthermore, parasites were able to escape from the brain and establish a systemic infection with liver and peritoneal involvement. Immunopathological studies indicated that TCRdelta(-/-) mice develop little inflammatory response and less neurological symptomatology. Significantly reduced numbers of T cells, macrophages, dendritic cells, and mast cells were present in the brain. The cytokine response in the brain of TCRdelta(-/-) mice appears to be a mixed type1/type 2 response with low levels of IL-2, IL-4, IL-10, IL-12, IL-13, IL-15, and IFN-gamma. To further investigate the immunological significance of this cell population, gammadelta T cells were adoptively transferred into intracranially infected TCRdelta(-/-) mice. gammadelta T cells were specifically recruited into the CNS in response to this parasitic infection, and they were able to target the infected brain within 12 h after transfer. These results suggest that gammadelta T cells are key players in the immune response elicited during this CNS infection and direct a type 1 response in wild-type mice upon infection.

In neurocysticercosis, the nervous tissue surrounding the brain lesion is affected as a consequence of the local immune response induced by a Taenia solium metacestode. In this study, a histological and immunohistochemical analysis of five brain specimens from patients with neurocysticercosis revealed a proinflammatory activity reflected by an apparently altered blood-brain barrier permeability, secretion of pro-inflammatory cytokines, and up-regulation of molecules associated with antigen presentation. There were also anti-inflammatory cytokines, as well as an active wound-healing process reflected by angiogenesis, collagen deposition and glial scar formation. This immune response displayed by the nervous tissue adjacent to chronic neurocysticercosis lesions appeared to be contributing to the local tissue damage, and hence, may be fundamental in the pathology of NCC.

TCRBV CDR3 repertoire diversity was analyzed in a cross-sectional study of HIV-infected individuals by CDR3 fingerprinting/spectratyping and single strand conformation polymorphism (SSCP). Most TCRBV families were detected in CD4+ cells of HIV-infected patients with CD4 counts ranging from 35 to 1103. In patients with CD4 counts >500, CD4+ TCRBV CDR3 fingerprinting profiles contained subtle variations with generally gaussian-distributed sizes. Lower CD4 counts coincided with more fragmented TCRBV CDR3 repertoires, containing dominant bands and bands missing from the CDR3 profiles. The CD8+ population of the same patients exhibited skewed CDR3 profiles of the majority of TCR BV families at CD4 counts >500. Irregularity of CD8+ CDR3 size distribution was most profound at low CD4 counts and suggested domination of the CD8+ TCRBV repertoire by a limited number of clones. Skewed patterns of CDR3 diversity probably reflect (oligo)clonal expansion of particular CD4+ and CD8+ cell populations during chronic infection with HIV. In addition, irregular CDR3 profiles of CD4+ and CD8+ at low CD4 counts suggest diminished TCR repertoire diversity, which may contribute to immunodeficiency.

In neurocysticercosis (NCC), it is thought that the long-term survival of the parasite within the human brain is due in part to the ability of the cestode to suppress the local immune response. When the parasite dies, the immunosuppression is apparently lost and a strong local inflammatory response then develops. In contrast, little is known about the immunologic response that may occur in the peripheral immune system of these patients. In this study, the status of the peripheral (extracerebral) cellular and humoral response was evaluated in patients with a history of NCC. The in vitro proliferation of peripheral blood mononuclear cells to mitogens and foreign antigens was similar in patients and controls. Importantly, a substantive response was elicited by two Taenia solium metacestode antigens. In addition, 8 of 10 patients had a detectable humoral response to the antigenic glycoproteins of the cestode. Considering both the cellular and humoral response, all of the patients with NCC presented an active peripheral immunity.

Infection with the protozoan Leishmania donovani in humans is usually subclinical. Parasites probably persist for the life of the host and the low-level infection is controlled by the cellular immune response. To better understand the mechanisms related to the control of infection, we studied the evolution and architecture of the splenic cellular immune response in a murine model that is most representative of human subclinical infection. Following systemic inoculation with L. donovani, the parasites were primarily localized to the macrophage-rich splenic red pulp. There was an initial increase in the numbers of T cells and dendritic cells in the periarteriolar lymphoid sheath and marginal zone, but the red pulp (where parasitized macrophages were prominent) remained free of these cells until later in the course of infection. Thus, T cells did not colocalize with parasitized red pulp macrophages until later in the course of infection. Early in the course of infection, IL-10 production within the marginal zone and TGF-beta production by cells in the red pulp were prominent. These macrophage-inhibitory cytokines may contribute to the establishment of the infection and early parasite replication. By day 28 of infection, when the visceral parasite burden began to decline, the number of IL-10-producing spleen cells was back to the baseline level, but IFN-gamma production was higher and the number of IL-12-producing cells was increased dramatically. At this time T cells and dendritic cells had moved out of the lymphoid follicle and marginal zone into the red pulp where the parasites were located. These findings therefore suggest that control of infection is associated with IFN-gamma and IL-12 production and migration of T cells and dendritic cells to the site of chronic parasitism., (Copyright 2001 Academic Press.)

Neurocysticercosis (NCC) is a common central nervous system (CNS) infection caused by Taenia solium metacestodes. Despite the well-documented importance of the granulomatous response in the pathogenesis of this infection, there is limited information about the types of cells and cytokines involved. In fact, there has been limited characterization of human brain granulomas with any infectious agent. In the present study a detailed histological and immunohistochemical analysis of the immune response was performed on eight craniotomy specimens where a granuloma surrounded each T. solium metacestode. The results indicated that in all the specimens there was a dying parasite surrounded by a mature granuloma with associated fibrosis, angiogenesis, and an inflammatory infiltrate. The most abundant cell types were plasma cells, B and T lymphocytes, macrophages, and mast cells. Th1 cytokines were prevalent and included gamma interferon, interleukin-18 (IL-18), and the immunosuppressive, fibrosis-promoting cytokine transforming growth factor beta. The Th2 cytokines IL-4, IL-13, and IL-10 were also present. These observations indicate that a chronic immune response is elicited in the CNS environment with multiple cell types that together secrete inflammatory and anti-inflammatory cytokines. In addition, both collagen type I and type III deposits were evident and could contribute to irreversible nervous tissue damage in NCC patients.

Objective: To evaluate dynamics in CD8 T cell expansions during highly active antiretroviral therapy (HAART)., Design: Various T cell subsets were isolated from blood and lymph nodes and analysed for T cell receptor (TCR) diversity., Methods: TCR complementarity determining region 3 (CDR3) spectratyping and single-strand conformation polymorphism (SSCP) analyses were performed in combination with sequencing to assess clonality of the subsets., Results: Strongly skewed CDR3 patterns in total CD8 cells and the CD8 subsets CD45RO+CD27+ and CD45RO-CD27+ showed substantial dynamics in dominant CDR3 sizes, resulting in relative improvement of CDR3 size diversity in the first months of therapy. During sustained treatment, TCR diversity changed only moderately. SSCP profiles confirmed oligoclonality of TCR CDR3 perturbations. Various dominant CDR3 sizes for CD4 and CD8 T cells present in lymph nodes, but not in peripheral blood mononuclear cells, before the start of therapy emerged in peripheral blood early during therapy., Conclusions: HAART induces substantial changes in CD8 TCR diversity, eventually resulting in improvement of the repertoire. Clonal expansions observed in lymph nodes before therapy were observed in peripheral blood after therapy, suggesting that recirculation of CD4 and CD8 T cells from lymph nodes contributes to the early T cell repopulation. Decreased immune activation and possibly naive T cell regeneration subsequently decreased clonal expansions and perturbations in the CD8 TCR repertoire.

The glycoproteins of 12-28 kD from Taenia solium metacestodes provide a high specificity and sensitivity for the serological diagnosis of the central nervous system infection, neurocysticercosis. Their widespread use as antigens for routine serological assays will require their production in large and reproducible amounts. Prior to determining the ideal strategy to produce these antigens at a large scale, it is important to determine the contribution of the carbohydrates to the antigenicity of these molecules, given the uncertainty of reproducing saccharidic epitopes in recombinant expression systems. In this study we examined this issue. The chemical oxidation of the carbohydrates of the 12-28 kD glycoproteins with sodium metaperiodate, reduced the antigenicity of the molecules to variable extents, with the more notable changes being detected for the 18 and 28 kD antigens. This approach was complemented by purification of the 12, 16 and 18 kD antigens, followed by the enzymatic deglycosylation of their abundant N-linked oligosaccharides. Silver-stained SDS-PAGE analysis indicated that the three deglycosylated antigens now migrated as 7 kD products, suggesting a protein backbone with a similar size, but different extents of glycosylation. By Western blot, the antigenicity of these antigens was diminished. This was more notable for the 18 kD antigen, which is more heavily glycosylated than the 12 or 16 kD glycoproteins. These data suggest that the antigenicity of the glycoproteins of T. solium is due to a combination of carbohydrate and protein epitopes.

The feasibility of using ex vivo-expanded hematopoietic progenitor cells to reconstitute hematopoiesis after high-dose chemotherapy is presently being examined. Early studies have shown that myeloid and erythroid hematopoiesis can be successfully reconstituted after high-dose chemotherapy and ex vivo-expanded hematopoietic cell transplantation. The lymphoid reconstitution, however, has not been addressed previously. In this study, we examined the diversity of the T cell receptor V beta chain (TCRBV) repertoires in 5 breast cancer patients who were transplanted with ex vivo-expanded bone marrow mononuclear cells as the only source of hematopoietic graft. Using the TCRBV third complementarity determining region (CDR3) fingerprinting methodology, it is shown that CD4(+) and CD8(+) T cell subsets after ex vivo-expanded hematopoietic cell graft transplants exhibit TCRBV diversities that are similar in complexity when compared to those seen after conventional autologous peripheral blood stem cell transplants (PBSCT). No apparent difference in the extent of CDR3 diversity was found between ex vivo expanded and conventional autologous PBSCT recipients when the CD4(+) and CD8(+) subsets were further separated into CD45RA(+) "naïve" and CD45RO(+) "memory" subsets. The diversity of the CD45RA(+) naïve subsets was as complex as that of the CD45RO(+) memory subsets. These results indicate that T cell repertoire diversification is not further compromised when ex vivo-expanded hematopoietic cells are used instead of autologous peripheral blood stem cells as the only source of graft.

Human neurocysticercosis is caused by Taenia solium metacestodes. It usually affects the central nervous system of humans and can be confused with other brain pathologies. The Lens culinaris-binding glycoproteins from this parasite have been shown to be ideal targets for the development of a highly specific immunoassay for the diagnosis of neurocysticercosis. In the present study we characterised the carbohydrates associated with five antigenic glycoproteins of T. solium metacestodes in the range of 12-28 kilodaltons. Lectin-affinities and enzymatic deglycosylations suggested that each of the five antigens contain various glycoforms of asparagine-linked carbohydrates of the hybrid, complex and probably high mannose type. These carbohydrates accounted for at least 30-66% of the apparent molecular mass of the glycoconjugates. In contrast, there was no evidence for the presence of O-linked carbohydrates. Lectin affinity patterns suggested that the sugars are short and truncated in their biosynthetic route, and that some contain terminal galactose moieties. Elucidating the precise structure of the carbohydrates and establishing their role in antigenicity will be essential to design strategies to produce them in large and reproducible amounts for the development of improved immunoassays.

Neurocysticercosis is the most common parasitic disease of the central nervous system worldwide. It is caused by the metacestode form of the helminth Taenia solium. Study of the immune response in the human brain has been limited by the chronic progression of the disease, the influence of corticosteroid treatment, and the scarcity of patients who undergo surgical intervention. To better understand the immune response and associated pathology in neurocysticercosis, a mouse model was developed by intracranial infection of BALB/c mice with Mesocestoides corti, a cestode organism related to T. solium. The immune response reveals the presence of abundant inflammatory infiltrates appearing as early as 2 days postinfection in extraparenchymal regions. In contrast, infiltration of immune cells into parenchymal tissue is significantly delayed. There is a natural progression of innate (neutrophils and macrophages), early induced (NK cells and gamma delta T cells), and adaptive immune responses (alpha beta T cells and B cells) in infected mice. Gamma delta T cells are the predominant T cell population. A cell-mediated Th1 pathway of cytokine expression is evident in contrast to the previously described Th2 phenotype induced in the periphery.

Objectives: Highly active antiretroviral therapy (HAART) induces a decline in viral load and a biphasic increase in peripheral blood CD4+ T-cell counts in HIV-infected patients. To evaluate the effect of HAART on T-cell receptor (TCR) diversity of repopulating naive and memory CD4+ T cells, complementarity determining region 3 (CDR3) spectratyping was performed., Design: For four patients treated with HAART, CD45RO+ (memory) and CD45RA+ (naive) CD4+ T cells were isolated from peripheral blood leukocyte samples obtained 1 week before, 1-2 months after, and 9-11 months after start of treatment., Methods: CDR3 regions were amplified by TCR-BV-specific nested PCR from CD4+ T-cell subsets. CDR3 size distributions and single-strand conformation polymorphism profiles were compared as an indication for TCR diversity., Results: Increasing blood CD4+ T-cell counts during the first 2 months of treatment coincided with increased perturbation of CDR3 patterns in CD4+ T-cell subsets, suggesting an early oligoclonal repopulation. At later timepoints, CDR3 size diversity increased when T-cell counts did not substantially decrease. Memory and naive CD4+ T cells generally showed comparable levels of perturbation., Conclusion: Diversity of the TCR repertoire reflected biphasic T-cell repopulation during HAART, compatible with initial redistribution and later CD4+ T-cell production. Sustained elevation of T-cell counts will in principle result in restoration of TCR diversity.

Size-diversity of Ig and T cell receptor antigen binding (CDR3) regions can be visualized by "CDR3 fingerprinting", and provides an estimate of B- or T-cell repertoire complexity. The method does not identify clonal diversity, however, which can only be determined by random sequencing of the CDR3s. In this study we demonstrate that a combination of fingerprinting and single strand conformation polymorphism (SSCP) analysis can be used for a rapid estimation of clonal diversity within mouse Ig antigen binding regions selected for size. This application may be useful in the analysis of clonal expansion within B- and T-cell repertoires.

Previous studies have suggested that the B-cell repertoire after stem cell transplantation resembles the developing repertoire in the fetus. Fetal and adult repertoires differ strikingly at the molecular level in Ig heavy chain third complementarity determining region (H CDR3) size distribution and Ig gene utilization. Previously, the posttransplant repertoire has not been studied fully in this regard. In this study, we analyzed H CDR3s posttransplant using CDR3 fingerprinting, single-strand conformation polymorphism (SSCP), and random sequencing. Eleven adult patients who received either autologous (n = 6) or allogeneic adult sibling (n = 5) hematopoietic stem cell transplants were studied. IgM H CDR3 repertoires demonstrated limited clonal diversity within the first 6 to 10 weeks posttransplant. By 3 to 4 months, the IgM H CDR3 repertoires were as diverse as those in healthy adults. Reconstitution of the IgM diversity correlated with the expansion of the multimember VH3 family. By contrast, the contribution of the single-member VH6 family was limited in most patients up to 6 to 9 months. No evidence was seen for greater contribution of VH6 posttransplant. IgG repertoires remained clonally restricted at all times. In all patients, H CDR3 sizes fell within adult limits. Direct nucleotide sequencing of H CDR3s showed adult-type N-nucleotide insertions and Ig gene utilization. These results indicate that the emerging repertoire posttransplant does not resemble the developing fetal repertoire at the molecular level., (Copyright 1998 by The American Society of Hematology.)