Measles encephalomyelitis--clinical and immunologic studies

Immunopathological reactions in viral infections of the central nervous system

Viral infections of the central nervous system (CNS), as of any other organ, evoke humoral and cellular immune responses which enable the host to eliminate the pathogen. However, effective responses may themselves produce tissue damage sometimes exceeding that caused by the virus itself. The relative contribution of the various immunopathological mechanisms in human viral encephalitides remains mostly ill defined. Most of our understanding of the immunopathogenesis in viral CNS infections comes from studies on experimentally infected animals. The prototype model of a virus-induced, cell-mediated, immunopathological CNS disease is the neurological illness of mice that follows intracerebral inoculation with lymphocytic choriomeningitis virus. Virus-specific cytotoxic T cells are crucial to the pathogenesis but death of the animals only results when these cells are targeted into functionally essential brain structures like the circumventricular organs or the medulla oblongata and cervical spinal cord.

Autoimmunity in demyelinating diseases

Demyelinative diseases of the CNS and peripheral nervous system can be distinguished on the basis of primary mediation by antibody or T lymphocytes (or failure of the T-cell-mediated response) and on the basis of chronicity. The principal mechanisms are autoimmunization to myelin antigens after actual immunization with tissue or infection with cross-reactive viruses or, alternatively, persistent infection of the nervous system (viral or spirochetal) with an associated immune response to the pathogen.

Monoclonal antibody defines determinant between Theiler's virus and lipid-like structures

Theiler's murine encephalomyelitis virus is known to cause a chronic demyelinating disease in mice. The contributions of immunologic factors, i.e. humoral and cellular responses to virus and/or myelin components, and direct virus-cell interactions leading to demyelination are still unclear. One important factor could be antibody initiation of myelin destruction. Here we describe four monoclonal antibodies that react with Theiler's murine encephalomyelitis virus. Three of these neutralize the virus and one of these three could also bind to various lipid-like structures including galactocerebroside, a myelin component. Further, this monoclonal antibody reacted with oligodendrocyte-like cells in vitro. All four monoclonal antibodies reacted with VP-1 by Western blot analysis. Thus, an immune response generated by virus that cross-reacts with a myelin element such as galactocerebroside could play a role in directing autoimmune processes toward myelin destruction.

The pathophysiology of myelin basic protein-induced acute experimental allergic encephalomyelitis in the Lewis rat

Histological and electrophysiological studies were performed on Lewis rats with acute experimental allergic encephalomyelitis (EAE) induced by inoculation with guinea-pig myelin basic protein (MBP) and Freund's adjuvant. The histological studies showed demyelination in the lumbar, sacral and coccygeal dorsal and ventral spinal roots and to a lesser extent in the spinal cord, including the dorsal root entry and ventral root exit zones. The electrophysiological studies demonstrated reduced conduction velocities between the lumbar ventral roots and sciatic nerve. Conduction block was demonstrated at the ventral root exit zone of the lumbar spinal cord but was less severe than in rats with whole spinal cord-induced acute EAE. Recordings of the M wave and H reflex elicited in a hindfoot muscle by sciatic nerve stimulation showed a normal M wave, indicating normal peripheral nerve motor conduction, but a markedly reduced H reflex. The reduction in the H reflex is accounted for by demyelination-induced nerve conduction block in the dorsal and ventral spinal roots, intramedullary ventral roots and at the dorsal root entry and ventral root exit zones of the spinal cord. Demyelination and nerve conduction abnormalities were well established in the relevant lumbar segments on the day of onset of hindlimb weakness. It is concluded that demyelination in the lumbar ventral roots and to a lesser extent in the lumbar spinal cord, including the ventral root exit zone, is an important cause of hindlimb weakness in myelin basic protein-induced acute EAE in the Lewis rat.

Humoral and cellular immune responses to matrix protein of measles virus in subacute sclerosing panencephalitis

The immune response to matrix (M) protein of measles virus was examined in patients with subacute sclerosing panencephalitis (SSPE) and controls. Antibodies specific for M and nucleocapsid (NC) proteins in 11 serum and 8 cerebrospinal fluid (CSF) samples from patients with SSPE were quantitated by enzyme-linked immunosorbent assay by using affinity-purified measles virus proteins. Geometric mean anti-NC antibody titers were higher in the serum (6.58 +/- 0.98 [mean +/- standard deviation]) and CSF (4.38 +/- 0.74) of SSPE patients compared with controls. Anti-M antibodies were present in the serum and CSF of all SSPE samples tested but in titers lower than those of anti-NC antibodies. Geometric mean anti-M antibody titer was 3.35 +/- 0.53 in sera from patients with SSPE compared with 3.05 +/- 0.66 in sera from patients with other neurological diseases and 3.12 +/- 0.74 in sera from healthy individuals. Geometric mean anti-M antibody titer was 2.59 +/- 0.86 in the CSF of eight patients with SSPE compared with a mean less than 1.00 for patients with other neurological disease (controls). Intrathecal synthesis of anti-M or anti-NC antibodies was established in four patients with SSPE. The cellular immune responses to M, F, HA, and NC proteins were examined in four of the patients with SSPE by lymphoproliferation and were not significantly different from those in five healthy controls. The results demonstrate humoral and cellular immune responses to M protein in patients with SSPE and indicate that it is unlikely that a defect in the immune response to this virus component accounts for the disease process in the patients studied.

Myelin basic protein-specific CD4+ cytolytic T-lymphocyte clones isolated from multiple sclerosis patients

In the present report we describe the isolation and characterization of stable, long-term, human T-lymphocyte clones specific for myelin basic protein (MBP) from multiple sclerosis (MS) patients. Isolation of these clones appeared possible only by seeding peripheral blood mononuclear cells into a limiting dilution microculture system containing MBP, autologous irradiated cells and Interleukin-2 (IL-2), thereby minimizing effects of putative suppressor cell populations. All clones obtained were of the CD4+ phenotype. The majority was capable of MBP-specific cytolysis, tested with 51Chromium-labeled autologous Epstein-Barr virus (EBV)-transformed B-cells, coated with MBP, as targets. A few other clones had natural killer (NK) function. All clones produced Interleukin-2 (IL-2) upon adequate stimulation.

Immunologic study of human encephalitic and paralytic rabies. Preliminary report of 16 patients

Lymphocyte proliferation tests to rabies antigen and myelin basic protein were performed on peripheral blood lymphocytes from nine patients with the encephalitic form and on seven with the paralytic form of human rabies. Six of the nine patients with encephalitis had proliferative responses to rabies antigen, whereas all of the patients with paralysis had no response. Two patients in each group also had a proliferative response to myelin basic protein. The myelin basic protein-reactive patients had a more rapidly fatal disease than the non-reactive patients. This preliminary study suggests that host immune responses may influence the clinical manifestations and course in human rabies.

Acute encephalitis with intrathecal synthesis of measles antibodies

In two cases of acute encephalitis, there was an intrathecal antibody synthesis against measles virus, as determined with an enzyme-linked immunosorbent assay. The clinical findings were not consistent with a usual measles infection, subacute sclerosing panencephalitis or acute multiple sclerosis.

Interferon gamma in acute and subacute encephalitis

Intrathecal synthesis of interferon gamma was shown in 14 out of 16 samples of cerebrospinal fluid collected in the first days of disease in adults, children, and newborn infants with herpes encephalitis. This synthesis was concomitant with that of interferon alpha and was switched off when the specific antibodies in the central nervous system increased. No endogenous interferon gamma was detected in 11 serum samples or 13 samples of cerebrospinal fluid collected early in the course of the disease from patients with measles encephalitis and rubella encephalitis, or in serum and cerebrospinal fluid samples from seven patients with subacute sclerosing panencephalitis. In serum collected after the 10th day after the onset of neurological symptoms interferon gamma was present at low concentrations in only three out of 11 serum specimens from patients with measles encephalitis or rubella encephalitis. Interferon gamma was present in patients with acute herpes encephalitis and there was active virus replication, but it was not present in postinfectious encephalitis. Possibly the local production of specific antibodies masks the viral antigens and switches off the induction of interferons.

Neuromyelitis optica (Devic's syndrome): not always multiple sclerosis

A patient is presented with clinical signs and symptoms of neuromyelitis optica (Devic's syndrome). The clinical findings, the cerebrospinal fluid findings and the Magnetic Resonance Imaging findings in our patient demonstrate that neuromyelitis optica is not always a form of Multiple Sclerosis. It can also be a manifestation of other demyelinating diseases, for example Disseminated Encephalomyelitis.

Induction of autoimmune reactions to myelin basic protein in measles virus encephalitis in Lewis rats

Intracerebral inoculation of weanling Lewis rats with measles virus led to the development of subacute measles encephalomyelitis (SAME) 4-8 weeks after infection. The disease is characterized pathologically by an intense inflammatory infiltration within both the white and grey matter of the central nervous system (CNS) without apparent demyelination. Both during and after SAME splenic lymphocytes from these animals could be restimulated in vitro to proliferate in the presence of myelin base protein (MBP). MBP-specific class II MHC-restricted T cell lines were isolated from this cell population. They were shown to exhibit no cross-reactivity with measles virus and to induce experimental allergic encephalitis (EAE) in naive syngeneic recipients following adoptive transfer. The clinical and histopathological signs of this T cell-mediated disease were identical to that seen in classical T cell-mediated EAE. A humoral immune response to MBP was only detected in a limited number of those rats with SAME. These results indicate that autoimmune reactions to brain antigen can arise during measles virus infection which may contribute to the pathogenesis of measles virus-associated encephalomyelitis.

T cells in multiple sclerosis and inflammatory central nervous system diseases

Using murine monoclonal antibodies to mark total T cells, we have found rapid migration of T cells into the CSF in progressive multiple sclerosis patients, suggesting that the ongoing inflammatory responses in the CNS may depend on the continued movement of cells from the periphery into the target organ. Cloning experiments have indicated that the T cells present in the CSF during viral and post-viral encephalomyelitis represent sequestered populations of antigen-specific cells. In more chronic disease processes, these cells may also have restricted clonality as measured by the frequency of different T-cell receptor gene rearrangements on Southern blotting. It is known that there is restricted clonality of the B-cell immunoglobulin response in the CSF compartment with inflammatory CNS diseases, and with infections the majority of these so-called oligoclonal antibodies are directed against the exciting antigen and are synthesized in the CNS. Although we believe that T cells in the CNS originate from the blood, during the course of an inflammatory response the antigen and clonally-restricted populations found in the CSF may represent either selective migration or selective accumulation in the CNS. Selective migration might occur at the endothelial barrier as these cells can express Class II MHC antigens and act as antigen-presenting cells in the CNS (McCarron et al. 1985). Selective accumulation of T cells in the CNS might occur after non-specific migration of cells into the CNS followed by proliferation and expansion of T cells that have been induced by antigens in the brain. Antigen-presenting cells that are present in situ, such as astrocytes, may also play a role in the selective expansion of T cells in the CSF (Fontana et al. 1984). Alternatively, it is possible that T cells are induced to expand in the target CNS tissue non-specifically, e.g., via the CD2 pathway. In this regard, we have observed that CSF T cells exhibit alterations in stimulation by anti-T112 + anti-T113 monoclonal antibodies. The mechanism of damage to CNS tissue by immune cells is essentially unknown. For example there are no clear links between antibodies present in the CNS and CNS damage in SSPE where high titers of anti-measles antibodies are present. Whereas we did not observe high frequencies of measles-reactive cells in the CSF of a subject with SSPE, we did observe MHC non-restricted cytotoxic T cells which expressed TCR-gamma chains rather than alpha-beta chains.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of in vitro transcription and transcriptional products of measles virus

Ribonucleoprotein complexes isolated from measles virus-infected HeLa cells contained an RNA-dependent RNA polymerase activity that catalyzed the incorporation of ribonucleotides into ribonucleic acid. The ribonucleoprotein complexes were composed of measles virus nucleoprotein, phosphoprotein, and a large protein, as well as viral RNA. The kinetics of RNA synthesis at different temperatures, time intervals, and protein, ribonucleotide, and mono- and divalent cation concentrations were analyzed. Enzyme activity was maximum at 4 h at 25 degrees C in the presence of 100 mM Na+-2.5 mM Mg2+-1 mM ribonucleotides. Actinomycin D and alpha-amanitin had no effect on the enzyme activity. Addition of cytoplasmic extracts from uninfected HeLa cells to the reaction mixture did not increase the incorporation of ribonucleotides into RNA. The in vitro synthesized RNAs were characterize by slot blot analysis and quantitated by densitometer scanning. All mRNAs coding for the structural proteins of measles virus were synthesized. Nucleoprotein RNA was the most abundant species made, followed by phosphoprotein, hemagglutinin, fusion protein, matrix protein, and large-protein RNAs. The system described here resulted in the first efficient transcription of measles virus RNA and analysis of products.

Soluble IL-2 receptors in acute and subacute encephalitis

Elevated levels of soluble interleukin-2 receptors were present in the serum from patients with acute primary and postinfectious encephalitis and subacute sclerosing panencephalitis. In addition, soluble interleukin-2 receptors were detected in the cerebrospinal fluid from patients with acute primary encephalitis. Their presence in the cerebrospinal fluid was not explained by damage to the blood-brain barrier and our data attest to their local origin. This suggests that it may be possible in certain neurological diseases to detect cerebral T-lymphocyte activation through a specific marker in the cerebrospinal fluid.

Schizophreniform episode following measles infection

A case of schizophreniform episode following measles infection in a 27-year-old woman is presented. The possibility that the clinical picture is a first description in the literature of an association between a schizophreniform episode and possible measles-induced allergic encephalitis is discussed. Other possible connections between measles infection and schizophreniform episode are also mentioned.

Identification of a nonproductive, cell-associated form of measles virus by its resistance to inhibition by recombinant human interferon

Subacute sclerosing panencephalitis (SSPE) is a fatal disease in children and young adults that is caused by persistent infection of the central nervous system (CNS) by a nonproductive, cell-associated form of measles virus. Using an experimental model for SSPE (LEC viral strain in newborn hamsters), we have shown previously that establishment of such CNS infections involves selective elimination from the CNS of productively infected cells by host defensive mechanisms, coupled with the selective sparing of cells carrying nonproductive viral forms. That interferon (IFN) may play a role in this process was suggested by the disappearance of productively infected cells from the CNS tissues prior to the appearance of antiviral antibodies and by the demonstration of cell-associated, IFN-resistant viral variants in the virus stocks that were used. Results of this study support these conclusions by showing that similar IFN-resistant viral variants are present in the HBS strain of SSPE-derived measles virus and that these variants, in the presence of IFN, have properties that are similar to those of naturally occurring cell-associated strains of SSPE viruses, e.g., DR, IP3, and Biken. These IFN-resistant forms of HBS virus were isolated and were shown to maintain their resistance to inhibition by IFN after cloning. However, on removal of IFN, they reverted to productive forms similar to the parental HBS virus. The potential role of such viral forms in the pathogenesis of SSPE is discussed.

Immune responses in the central nervous system

Immune responses occurring within the central nervous system (CNS) have unique features attributable to the cellular and functional organization of the CNS and to the presence of the blood-brain barrier. Immune responses to viral infection of the CNS involve the participation of most immunologically important cells: T and B lymphocytes, monocytes, and natural killer cells. Normally, helper/inducer T lymphocytes are predominant in the cerebrospinal fluid (CSF) and in perivascular cuffs. After stimulation with antigen in tissue, these cells produce lymphokines, which stimulate mast cells to open capillary tight junctions, stimulate proliferation of lymphocytes, and attract monocytes and B lymphocytes. B lymphocytes mature into immunoglobulin-producing cells that secrete antibody locally which appears in the CSF. Cytotoxic/suppressor T lymphocytes, which damage antigen-containing cells, are predominant in immunopathologic reactions. In other situations the immune response targets normal CNS tissue rather than foreign antigens. Two general types of reactions may be seen: (1) vasculitis with destruction of vessel walls and infarction, and (2) perivascular inflammation with demyelination. The former is associated with immune complex deposition, and the cellular infiltrate includes polymorphonuclear leukocytes. The inflammation associated with perivenular demyelination is composed almost exclusively of mononuclear leukocytes. In the diseases for which pathogenetic mechanisms are understood, cells become sensitized to myelin constituents and induce local demyelinating lesions in which the damage is effected by macrophages. It is not clear whether macrophages are directed in this destructive effort by lymphokines or immunoglobulins or both.

Myelin basic protein as an encephalitogen in encephalomyelitis and polyneuritis following rabies vaccination

Encephalitis and polyneuritis occurring after rabies vaccination are believed to be immunologically mediated. We studied antibody responses to neural antigens in 36 patients with major neurologic complications, 25 with minor complications, and 39 with no complications after immunization with a brain-derived, Semple rabies vaccine. Patients with major complications had significantly elevated levels of antibody to brain white matter as compared with the other groups (P less than 0.001). Assays for antibody to selected central nervous system antigens showed that high levels of serum and cerebrospinal fluid antibody to myelin basic protein correlated with the presence of major neurologic complications (both central and peripheral nervous systems). The level of antibody to cerebroside correlated best with the number of injections of vaccine, but like antibody to myelin basic protein, the antibody to cerebroside was present in the cerebrospinal fluid of patients with major complications. Some patients with major complications also had antibodies directed to the gangliosides GD1b and GT1b. No antibodies to myelin-associated glycoprotein were detected in any of the samples. These data implicate myelin basic protein as an encephalitogen in these autoimmune diseases of the human nervous system, but suggest that immune responses to cerebroside and certain gangliosides may have an augmentative role in severe disease.

Chronic Theiler's virus infection in mice: appearance of myelin basic protein in the cerebrospinal fluid and serum antibody directed against MBP

Myelin basic protein (MBP) appears frequently in the cerebrospinal fluid (CSF) of mice with chronic demyelination following intracerebral infection with Theiler's murine encephalomyelitis virus (TMEV); antibody to MBP can frequently be found in the sera. The peaks of the immune responses to both MBP and TMEV coincide with the time course of the clinical signs of disease. Adsorption of mouse sera with TMEV or MBP indicate the non-identity of the antigens and the specificity of the antisera as measured by ELISA. Immunoblot analysis of sera confirmed the ELISA findings. The mechanism of induction of antibody directed against MBP and its role in TMEV-associated demyelination remain to be determined.

The pathogenesis of virus-associated encephalopathies: a prospective study of immunological mechanisms

Thirty-two patients, including 29 children, presenting with acute unexplained encephalopathies were studied prospectively for evidence of virus infection, immunodeficiency, and immunologic involvement in the pathogenesis of their illnesses. Twenty-five of these patients had a clinical diagnosis of encephalitis. Twenty-two of these 25 had laboratory evidence of active virus infection, the majority with viruses usually associated with self-limiting illness outside the central nervous system. In patients with encephalitis, immune competence, as reflected by T-cell numbers and subsets in peripheral blood, in vitro interferon production, natural killer activity, and specific antiviral antibody production, was normal. Transudation of albumin into the cerebrospinal fluid (CSF), a measure of blood-brain barrier breakdown, was seen in 40% of patients. Intrathecal antibody synthesis was suggested by an elevated IgG index in 9/20 CSF/serum pairs but was confirmed by an elevated specific IgG ratio in only 3. The serum IgG1 and IgG3 subclass levels were significantly elevated at the time of the illness and remained elevated 8 months later; IgG2 and IgG4 levels were normal. IgE levels were elevated in 50% of patients. Serum levels of IgM antibodies against Escherichia coli measured 8 months after the neurological illness were also significantly higher in encephalitis patients than in age-matched healthy controls. Human myelin basic protein did not induce proliferation in peripheral blood lymphocytes in any patient. We conclude that most encephalopathies associated with viral infections are not due to an underlying generalized immunodeficiency, and probably result from an inappropriately vigorous immune response.

Canine distemper virus: the early blood-brain barrier lesion

Experimental infection of gnotobiotic Beagle dogs with neurovirulent R252 canine distemper virus (CDV) resulted in hematogenous dissemination of virus to the central nervous system (CNS). Viral antigen was first detected within CNS capillary and venular endothelia and/or perivascular astrocytic foot processes and pericytes. The number of primary infection sites was evenly distributed throughout the neuraxis. Leukocytic infiltrations followed CNS endothelial cell infection by 1-2 days and were composed of both viral antigen-positive and -negative cells. These results indicate that CDV infection of the CNS is initiated by the interaction of circulating infectious virus with endothelial cells.

Neurological aspects of mycoplasmal infection

Mycoplasmal infections may be complicated by a wide variety of systemic syndromes, including neurological disorders. Circumstantial evidence suggests that these are immunologically-induced. A detailed study of five patients with proven mycoplasma pneumoniae and central nervous system signs showed that immunological factors were involved and suggested that the neurological symptoms were due to a vasculopathy.

Chronic relapsing experimental autoimmune encephalomyelitis. Transient presence in blood of lymphocytes sensitised to encephalitogen at onset of inflammatory relapses

Juvenile guinea pigs were immunised with homologous spinal cord and monitored daily over a 6-month period for neurological signs of chronic relapsing experimental autoimmune encephalomyelitis (CREAE). At various times animals were killed, numbers of leucocytes in their cerebrospinal fluid (CSF) quantified, and in vitro proliferative responses of blood lymphocytes to myelin basic protein (MBP) and its encephalitogenic nonapeptide (NP) determined. After recovering from initial acute clinical signs, animals suffered at least two major spontaneous relapses separated by remission periods of 4-5 weeks mean duration. In the early chronic phase, 5-12 weeks post-immunisation (pi), 63% of the animals recovered fully from relapses, whereas relatively irreversible neurological deficits predominated in the late chronic phase. During the acute and chronic phases, there was a highly significant correlation between clinical severity and CSF pleocytosis only in animals killed within 24 h of onset of a clinical exacerbation associated with more than 100 leucocytes/microliter of CSF. Guinea pigs with this degree of CSF pleocytosis were defined as suffering an inflammatory relapse. Blood lymphocytes responsive to MBP and NP were detected only in animals killed at the onset of clinical signs of either the acute or an inflammatory relapse. This dynamic relationship suggests that migration of encephalitogen-responsive lymphocytes via the blood to the central nervous system could produce certain relapses in CREAE. However, the relative paucity of CSF leucocytes in most animals killed during relapses between 15-26 weeks pi suggests that other factors may elicit neurological exacerbations in the late chronic phase.

HLA antigens in acute measles encephalitis

The frequency of HLA-A, B, DR antigens was studied in 24 patients with acute measles encephalomyelitis compared to 1926 control subjects. The results demonstrated no association between the susceptibility to the disease and HLA markers. However, DR4 was observed in 6 patients out of 10 who developed intrathecal secretion of specific antimeasles immunoglobulins, while absent in 4 patients, who did not (p less than 0.04). Further studies on a larger series are needed.

Myelin basic protein and demyelinating diseases

Myelin basic protein (MBP) is a major protein component of myelin sheath. Primarily because of its ability to induce experimental allergic encephalomyelitis (EAE) in animals, this protein has been considered to play an important role in the pathogenesis of multiple sclerosis (MS), which is one of the most common demyelinating diseases. Its precise measurement in the cerebrospinal fluid (CSF) has been uncommonly difficult, mainly due to immunoheterogeneity of MBP or MBP-like material. More recently, highly sensitive radioimmunoassay techniques utilizing well-characterized antisera have been developed that facilitated its use in the management of MS. The clinical course of MS is highly variable, and the disease is characterized by periods of remission and relapses. Many studies have demonstrated the release of MBP during relapses and elevated levels of MBP in the CSF can be detected if lumbar puncture is performed within 7 days of the onset of neurologic symptoms suggestive of MS. However, the presence of MBP is not an absolute indicator of MS, as elevated MBP levels are also frequently observed in other demyelinating diseases.

Acute disseminated encephalitis documented by magnetic resonance imaging and computed tomography. Report of a case

A 16-year-old girl developed left hemispheric deficits, which were followed by clouding of consciousness, quadriplegia, and subcortical blindness. Although we could not demonstrate a recent viral infection, the clinical features, laboratory and radiologic findings strongly suggested the diagnosis acute disseminated encephalitis. Cerebrospinal fluid abnormalities incompletely correlated with the clinical course. In contrast, X-ray computed tomography and particularly magnetic resonance imaging of the head closely reflected disease and improvement.

Amino acid homology between the encephalitogenic site of myelin basic protein and virus: mechanism for autoimmunity

Amino acid sequence homology was found between viral and host encephalitogenic protein. Immune responses were then generated in rabbits by using the viral peptide that cross-reacts with the self protein. Mononuclear cell infiltration was observed in the central nervous systems of animals immunized with the viral peptide. Myelin basic protein (MBP) is a host protein whose encephalitogenic site of ten amino acids induces experimental allergic encephalomyelitis. By computer analysis, hepatitis B virus polymerase (HBVP) was found to share six consecutive amino acids with the encephalitogenic site of rabbit MBP. Rabbits given injections of a selected eight- or ten-amino acid peptide from HBVP made antibody that reacted with the predetermined sequences of HBVP and also with native MBP. Peripheral blood mononuclear cells from the immunized rabbits proliferated when incubated with either MBP or HBVP. Central nervous system tissue taken from these rabbits had a histologic picture reminiscent of experimental allergic encephalomyelitis. Thus, viral infection may trigger the production of antibodies and mononuclear cells that cross-react with self proteins by a mechanism termed molecular mimicry. Tissue injury from the resultant autoallergic event can take place in the absence of the infectious virus that initiated the immune response.

A quantitation of myelin-associated glycoprotein and myelin basic protein loss in different demyelinating diseases

The loss of myelin-associated glycoprotein (MAG) and myelin basic protein (MBP) was compared by quantitative immunocytochemistry in demyelinating lesions of measles encephalomyelitis (ME), multiple sclerosis (MS), and progressive multifocal leukoencephalopathy (PML). Serial sections from paraffin-embedded tissue were reacted with antisera for MAG and MBP, and areas of staining loss were compared morphometrically. Lesions in ME showed MAG loss equal to that of MBP, lesions of PML showed MAG loss greater than that of MBP, and MS lesions showed a mixture of patterns. These data demonstrate distinctive patterns of MAG and MBP loss in these three diseases.

Sequence homology between certain viral proteins and proteins related to encephalomyelitis and neuritis

Post-infectious or post-vaccinal demyelinating encephalomyelitis and neuritis may be due to immunological cross-reactions evoked by specific viral antigenic determinants (epitopes) that are homologous to regions in the target myelins of the central and peripheral nervous systems. Such homologies have been found by computer searches in which decapeptides in two human myelin proteins were compared with proteins of viruses known to infect humans. These viruses include measles, Epstein-Barr, influenza A and B, and others that cause upper respiratory infections. Several regions identified in myelin basic protein and P2 protein can be related to experimental allergic encephalomyelitis or neuritis in laboratory animals.

Intrathecal synthesis of different alpha-interferons in patients with various neurological diseases

CSF and sera from 238 newborns and children with various neurological diseases were assayed on bovine cells for the presence of alpha-interferon (IFN). An intrathecal synthesis of pH 2-resistant alpha-IFN was recovered in all newborns and in more than 90% of children with herpes encephalitis. It was also observed in one case of mumps encephalitis and in one case of encephalitis associated with Influenza A infection. An acid-labile alpha-IFN production was detected in CSF from more than one half of patients with viral meningitis or active congenital rubella and in those with neurological complications of systemic lupus erythematosus. This alpha-IFN subtype was also detected in CSF from only 2/37 children with measles encephalitis. In contrast, no alpha-IFN (less than 2 IU) in CSF was found among patients with subacute sclerosing panencephalitis, Guillain-Barré syndrome, Reye's syndrome, acute cerebellar ataxia, infantile spasms or facial paralysis of unknown origin.

Acute viral encephalitis

Clinical manifestations of acute viral encephalitis are described, differential diagnoses are outlined, and a diagnostic approach is recommended. Encephalitic syndromes caused by arboviruses, herpesviruses, enteroviruses, and parainfectious processes are discussed.

Host genetic regulation of acute MHV-4 viral encephalomyelitis and acute experimental autoimmune encephalomyelitis in (BALB/cKe x SJL/J) recombinant-inbred mice

In the present report we provide the strain distribution patterns of susceptibility to acute mouse hepatitis virus type-4 (MHV-4) encephalomyelitis, acute experimental allergic encephalomyelitis (EAE) and vasoactive amine sensitivity (VAAS) for 9 (CXJ) recombinant-inbred strains between BALB/cKe (C) and SJL/J(J) mice. We confirm that susceptibility to MHV-4 is not linked to the H-2 complex, and that all strains susceptible to acute EAE have both a responder H-2 haplotype (H-2s or H-2d) and induced (B. pertussis) VAAS. In addition, we provide evidence that susceptibility to acute EAE induction is controlled by an additional presently unmapped locus and that an EAE-like histopathological disease does not usually follow MHV-4 infection intracerebrally in animals susceptible to MHV-4, acute EAE and induced VAAS.

Relapsing experimental allergic encephalomyelitis. An autoimmune model of multiple sclerosis

R-EAE is a valuable model for human MS. Table 2 outlines the similarities between R-EAE and MS. The clinical course and pathologic changes seen in this model accurately reflect the pattern of MS. The immunologic changes seen in animals with R-EAE also are similar to those seen in MS. Therefore, the clinicopathologic features of MS can be duplicated with a purely autoimmune model. Although this is of considerable pathogenic significance in understanding MS, we do not know what the inciting event is in MS that would be the equivalent of immunizing an animal with neural antigen. Despite this, R-EAE has and should continue to provide experimental data of considerable importance to an understanding of the mechanisms involved in the evolution of inflammatory demyelination. Other important models of MS utilize viral-induced demyelination. Although the clinical picture of most of the chronic demyelinating viral infections does not show as clear a relapsing or remitting pattern as seen in R-EAE, viral etiologies better fit the epidemiology of MS [16]. Several studies have demonstrated development of an acute EAE-like disease with sensitization to neural antigens following viral infection [12, 30, 56]. Thus, one can hypothesize an initial viral illness causing sensitization of the host to a neural antigen (?MBP) with a subsequent immunopathogenic course similar to that seen in R-EAE. Whether this will in fact be the case remains unproven as yet. Our understanding of the immunopathogenic mechanisms underlying inflammatory demyelination has been enlarged through studies of R-EAE. It is now clear that the minimal myelin antigen necessary for production of the disease is MBP, although this may differ in some species. The relapsing nature of this disorder is mediated in part through lymphocytes, as demonstrated in transfer studies, and thus does not require persistent antigenic depots. There is a genetic susceptibility to development of the CNS autoimmune state, and we speculate that an as yet unidentified perturbation of the host immune system allows for the occurrence of relapsing disease (Table 3).

Viral infections of the nervous system

Neurotropic viruses cause a number of important infectious syndromes including encephalitis, myelitis, meningitis, and radiculopathy. In this review, the biology of conventional and unconventional viruses is examined. The host immune response to viruses is discussed, and patterns of viral pathogenesis are explained. The clinical features, laboratory findings, management of important viral infections, such as herpes simplex encephalitis and epidemic encephalitis, are presented. Post-infection syndromes, such as the Guillain-Barré syndrome, and chronic viral infections, such as those causing progressive multifocal leukoencephalopathy and subacute sclerosing panencephalitis, are discussed. Current knowledge concerning the nature of unconventional virus-like agents of the spongiform encephalopathies, including kuru and Creutzfeldt-Jakob disease, is summarized. Finally, viral infections of immunocompromised patients and the possible role of viruses in the newly described acquired immunodeficiency syndrome (AIDS) are examined.

Basic proteins bind immunoglobulin G: a mechanism for demyelinating disease?

Heat-aggregated immunoglobulin G ( HAGG ) bound avidly to solid-phase basic proteins, including myelin basic protein. In contrast, monomeric immunoglobulin bound weakly. Bound HAGG could activate complement. Normal human serum strongly inhibited the binding of HAGG , even when decomplemented or greatly diluted. Cerebrospinal fluid was also inhibitory, but the effect was weaker. Apart from inhibition by decomplemented serum, the biochemical characteristics of the interaction were similar to those of other Fc ligands with IgG, particularly C1q. In multiple sclerosis this interaction could occur between IgG and central-nervous-system myelin basic protein, leading to demyelination by activation of immune mechanisms of tissue damage. Bound IgG is present in multiple sclerosis plaques and IgG from multiple sclerosis patients can produce demyelination in experimental models. However, there is little evidence of any specific immunity to central-nervous-system antigens in multiple sclerosis, and this non-specific interaction might be an important link in the pathogenesis of the disorder.