Carol Shoshkes Reiss

The role of IFN-γ in immune responses to viral infections of the central nervous system

Abstract Interferon (IFN)-γ, is not only a marker of T H 1 CD4, CD8 and natural killer (NK) cells, it is also a critical antiviral mediator which is central to the elimination of viruses from the CNS. In this review, we describe IFN-γ, its receptor, signal transduction from receptor engagement, and antiviral downstream mediators. We demonstrate that although neurons are post-mitotic and non-renewing, they respond to IFN-γ in a fashion similar to peripheral fibroblasts or lymphocytes. We have illustrated this review with details about studies on the role(s) of IFN-γ in the pathogenesis of measles virus (MV), herpes simplex virus (HSV) type 1, and vesicular stomatitis virus (VSV) infections of the CNS. For VSV infection, IFN-γ signals through Jaks 1 and 2 and STAT1 to activate (interferon regulatory factor) IRF-1; although viral protein synthesis is inhibited, PKR is not a critical mediator in the antiviral response to VSV in murine neurons. In contrast, induction of nitric oxide synthase (NOS) type 1 and its production of nitric oxide is essential in the elimination of viruses from neurons.

Interferon-γ induced type I nitric oxide synthase activity inhibits viral replication in neurons

Abstract Type I NOS expression increases in OB neurons during VSV infection. Immunocytochemical staining of NB41A3 cells indicates constitutive expression of interferon (IFN)-γ receptor and type I NOS. IFN-γ treatment of NB41A3 cells increased NO production and type 1 NOS protein. In vitro replication of VSV, polio virus type 1, and Herpes Simplex virus type 1 (HSV-1) is significantly inhibited by IFN-γ induced type I NOS and antagonized by NOS inhibitors. In contrast, while IFN-γ treatment inhibited influenza and Sindbis virus replication, a different pathway(s) was involved. The isoform-selective NOS inhibitor, 7-nitroindazole (7NI) was used to treat mice, resulting in a 10-fold higher titer of virus in brain homogenates, and abrogated the recovery-promoting effect of interleukin-12 treatment. Thus, IFN-γ induced type I NOS activity may play an important role in host immunity against neurotropic viral infections.

Distribution of vesicular stomatitis virus proteins in the brain of BALB/c mice following intranasal inoculation: an immunohistochemical analysis

Earlier studies have shown that intranasal instillation of vesicular stomatitis virus (VSV), a negative-sense RNA virus, in mice and rats can result in infection of the brain, hind-limb paralysis and death. Using an antiserum directed against VSV proteins, we sought to determine the potential neuronal and non-neuronal pathways VSV utilize, for central nervous system dissemination in BALB/c mice. Within 12 h following intranasal inoculation of VSV, VSV antigen could be detected in the olfactory nerve layer of the ipsilateral olfactory bulb. Within 3-4 days post-inoculation (p.i.), VSV had disseminated into the glomeruli of the olfactory bulb as well as the anterior olfactory nuclei that were ipsilateral to the VSV instillation. Within the glomeruli, VSV antigen was more prevalent in the granule cells than in the mitral cells. Correspondingly, the lateral olfactory tract, where axons of mitral cells course, remained VSV negative throughout 7 days p.i. By 7 days p.i., viral proteins were detected in several additional regions extending to the brainstem. These included regions involved in theta-rhythm generation during exploration and REM sleep, i.e. the septal nuclei, the supramammillary body, and the hippocampal formation, as well as the amygdaloid complex and brainstem neuromodulatory centers, such as the dorsal raphé and locus coeruleus. Structures abutting the ventricular surfaces, such as the dorsal cochlear nucleus, were also labeled. Tracts immunoreactive to VSV included the dorsal tegmental tract, fascia retroflexus, Probst tract, and mesencephalic tract of the trigeminal motor nerve. Besides the lateral olfactory tract, tracts that remained VSV negative included the anterior commissure, the corpus callosum and the mammillary peduncle. The pattern of VSV immunoreactivity supports the idea that following infection of the olfactory bulb glomeruli, VSV spreads via both ventricular surfaces and retrograde transport within axons of neuromodulatory transmitter systems innervating the olfactory bulb. Conversely, regions exhibiting low levels of VSV antigen are not likely to be involved in VSV dissemination. In particular, the paucity of VSV antigen in some of the terminal fields of neuromodulatory systems indicate that anterograde transport is more selective than retrograde transport. Surprisingly, the principal neurons of the olfactory glomeruli, thalamus, cerebral cortex and the hippocampus, all of which use L-glutamate as the excitatory neurotransmitter, are much less involved in viral dissemination.

Sex differences in susceptibility to viral infection of the central nervous system

We have characterized striking differences in recovery of male and female BALB/c and BALB/c-H-2dm2 (dm2) mice from an experimental neurotropic viral infection of the central nervous system (CNS). Following intranasal inoculation of vesicular stomatitis virus (VSV), assays of tissue homogenates from female mice produced lower viral titers. There was also a significant reduction in the spread of virus from the rostral to caudal end of the brain in female mice. Enhanced recovery by female mice of both strains in response to this viral insult correlates with increased levels of Nitric Oxide Synthase (NOS) types I, II, and III expression, an increased prevalence of reactive astrocytes, earlier and enhanced levels of expression of Major Histocompatibility Complex (MHC) class II molecules on astrocytes, endothelial and microglial cells, and increased T cell infiltration in the female BALB/c mouse. Taken together, these findings document sexual dimorphism in CNS immunity, and may provide an understanding of some of the mechanisms underlying many sex-biased diseases.

Evidence for genetic restriction in the suppression of erythropoiesis by a unique subset of T lymphocytes in man.

The suppression of erythropoiesis by lymphocytes from patients with a T cell lymphoproliferative syndrome and pure erythrocyte aplasia has been previously demonstrated. To study the nature of the suppressor cell and possible genetic restriction of this suppression, we investigated a patient with severe anemia, splenomegaly, lymphocytosis, and erythroid aplasia. A 3-mo course of low-dose daily oral cyclophosphamide achieved a complete remission for over 12 mo. The surface phenotype of his lymphocytes was analyzed by means of antibodies to lineage, differentiation, and activation-specific surface antigens. The cells expressed mature T cell antigens T3, T8, and T11, while lacking T1. Immature T cell, B cell, and the monocyte-specific antigen Mo2 were absent, while Mo1, a monocyte-associated antigen not normally expressed on T cells, was present. T10 and Ia expressed as activation antigens were also present. The cells, cryopreserved at diagnosis, were thawed and co-cultured in plasma clot with patient remission marrow samples at T cell/bone marrow ratios of 1:1 and 2:1. There was nearly 90% suppression of erythroid colony-forming unit expression and 60% suppression of erythroid burst-forming unit expression at 2:1 T cell to bone marrow ratios and somewhat less suppression at 1:1. Granulocyte/macrophage progenitor expression was unaffected. Erythroid progenitor differentiation in the marrows of two HLA identical siblings was similarly suppressed. The cells were co-cultured with the marrows of nine nonrelated donors to investigate the potential genetic restriction of this suppression. Colony suppression equal to that observed in the marrow of the patient and his siblings was found in studies of two partially HLA identical individuals. No suppression was detected in marrow co-cultures of two entirely HLA dissimilar individuals. These results show that suppression of erythropoiesis by a unique subset of T8, Mo1, Ia-positive lymphocytes isolated from a patient with lymphocytosis and erythrocyte aplasia is genetically restricted.

Interactions of T lymphocytes with human vascular endothelial cells: Role of endothelial cells surface antigens

We have studied the interactions of peripheral blood T lymphocytes with cultured human vascular endothelial cells, focusing upon endothelial cell surface antigens important for T cell recognition. Under standard culture conditions endothelial cells express class I but not class II major histocompatibility complex (MHC) antigens. However, class II antigens may be induced by activated T cells or T cell products, including the lymphokine immune interferon. Immune interferon concomitantly increases class I antigen expression and causes a change in cell shape. In addition to vascular endothelial cells, we have found that vascular smooth muscle cells and human dermal fibroblasts may also be induced by immune interferon to express class II antigens. All known human class II antigens are induced (i.e. HLA-DR, DC and SB) as is the associated invariant chain. Induced antigen expression in these cells is stable over several days, although mRNA levels decline rapidly upon withdrawal of interferon. Vascular and stromal cell class II antigens are functional, in that they can be recognized by cytolytic and helper T cell clones. Several non-MHC antigens are also involved in the recognition of endothelial and stromal cells by T cells. We propose a model for the role of inducible class II molecules on endothelium and stromal cells in vivo: The induction of class II MHC antigens on endothelial cells, locally mediated by activated T cells, enables endothelium to present an immunogenic cell surface structure, comprised of antigen plus self class II polymorphic determinants, which in turn, serves to recruit additional antigen-specific T cells from the circulation into the site of a developing cell mediated immune response. Class II molecules on stromal cells, also induced locally at the site of a developing response, confers immune accessory function on these cells and may serve to augment and sustain a T cell response.

Leukotrienes play protective roles early during experimental VSV encephalitis

Leukotrienes (LT) are potent lipid mediators of inflammation. 5-Lipoxygenase (5-LO) is the key enzyme in the conversion of arachidonic acid to LT. There are four LT: LTB(4), LTC(4), LTD(4) and LTE(4). LT have been extensively studied in airway inflammation but little is known about their roles in viral infection in the CNS. LTB(4) is a chemoattractant for neutrophils. In this work, we studied the roles of LT in acute vesicular stomatitis virus (VSV) encephalitis. Two methods were used to disrupt 5-LO activity: mice were treated with Zileuton, an enzyme antagonist, or 5-LO genetic knockout mice were used. We found that inhibition or deletion of 5-LO resulted in: (a) impaired process of neutrophil infiltration into the CNS early during viral infection; (b) fewer neurons expressed nitric oxide synthase-1 (NOS-1); (c) higher viral titers 1 day after viral infection; and (d) increased disruption of blood brain barrier (BBB). Our studies suggest that LT are important innate immune players during VSV pathogenesis and are beneficial to the host in early control of viral replication in the CNS.

Developmental brain abnormalities in tuberous sclerosis complex: A comparative tissue analysis of cortical tubers and perituberal cortex

Genetic loss of Tsc1/Tsc2 function in tuberous sclerosis complex (TSC) results in altered mammalian target of rapamycin (mTOR) signaling and abnormal brain development. Although earlier studies have focused on characterization of cortical tubers, in this study we sought to examine the unique cellular and molecular features of the perituberal cortex in order to better understand its contribution to epileptogenesis, cognitive dysfunction, and autism.

Human dermal fibroblasts present tetanus toxoid antigen to antigen-specific T cell clones.

Cultured human dermal fibroblasts treated with immune interferon express HLA-DR antigens. We report here that DR-positive fibroblasts present tetanus toxoid (TT) to autologous TT-specific monoclonal helper T cells vigorously depleted of monocytes by passage over Sephadex G10 columns followed by treatment with the monoclonal antibodies (mAb) OKM1 and Leu M1 plus complement. The extent of T cell proliferation in response to TT presented by DR-positive fibroblasts was similar to that elicited using monocytes as antigen-presenting cells. The proliferative response was TT dependent, antigen specific, depended upon DR expression by fibroblasts, appeared MHC restricted, and was completely blocked by mouse mAb to HLA-DR but not by mAb to HLA-A,B, or DQ. DR-positive fibroblasts pulsed with TT were similarly effective in antigen presentation. In summary, immune interferon-stimulated human dermal fibroblasts can substitute for classical antigen-presenting cells in antigen-specific proliferative responses. Since fibroblasts are a ubiquitous cell type in the body, they may play a significant role in the immunobiology of the host.

IL-12 and Viral Infections

Abstract Interleukin-12 activates natural killer cells and promotes the differentiation of Th1 CD4+ cells; it is a critical factor in viral immunity. IL-12 is secreted by antigen presenting cells including dendritic cells, macrophages and astrocytes, both in tissues and in secondary lymphoid organs. Experimental studies have shown that administration of the cytokine rapidly activates both innate and specific immune responses; this results in enhanced host cellular responses and generally, promotes clearance of virus and host recovery from infection. The observations of many laboratories, studying viral immunity to both RNA and DNA based pathogens, are summarized.