Measles-virus proteins in the brain tissue of patients with subacute sclerosing panencephalitis: absence of the M protein

Measles Sclerosing Subacute PanEncephalitis (SSPE), an intriguing and ever-present disease: Data, assumptions and new perspectives

BACKGROUND

Subacute sclerosing panencephalitis (SSPE) is a rare, non-treatable and fatal neurological complication of measles, still present due to the return of the epidemic linked to the loosening of vaccination policies. Its mechanism remains unexplained.

OBJECTIVE

The main objective was to investigate explanatory variables relating to the risk of developing SSPE and its pathophysiology.

METHODS

Literature analysis was focused on different varieties of SSPE: perinatal forms, short-incubation forms similar to acute measles inclusion body encephalitis (MIBE), rapidly evolving forms, forms occurring in the immunosuppressed, adult forms, and family forms. In addition, several studies on the parameters of innate immunity and interferon responses of patients were analyzed.

RESULTS

Two main data were highlighted: a relationship between the so-called fulminant forms and the prescription of corticosteroids was established. In familial SSPE, two groups were individualized according to the duration of the latency period, prompting an analysis of patient exomes.

CONCLUSION

Treatment with corticosteroids should be banned. Knowledge of the genes involved and epigenetics should be useful for understanding the pathophysiology of SSPE and other late-onset neurological infections with RNA viruses.

Microglia depletion exacerbates demyelination and impairs remyelination in a neurotropic coronavirus infection

Microglia are considered both pathogenic and protective during recovery from demyelination, but their precise role remains ill defined. Here, using an inhibitor of colony stimulating factor 1 receptor (CSF1R), PLX5622, and mice infected with a neurotropic coronavirus (mouse hepatitis virus [MHV], strain JHMV), we show that depletion of microglia during the time of JHMV clearance resulted in impaired myelin repair and prolonged clinical disease without affecting the kinetics of virus clearance. Microglia were required only during the early stages of remyelination. Notably, large deposits of extracellular vesiculated myelin and cellular debris were detected in the spinal cords of PLX5622-treated and not control mice, which correlated with decreased numbers of oligodendrocytes in demyelinating lesions in drug-treated mice. Furthermore, gene expression analyses demonstrated differential expression of genes involved in myelin debris clearance, lipid and cholesterol recycling, and promotion of oligodendrocyte function. The results also demonstrate that microglial functions affected by depletion could not be compensated by infiltrating macrophages. Together, these results demonstrate that microglia play key roles in debris clearance and in the initiation of remyelination following infection with a neurotropic coronavirus but are not necessary during later stages of remyelination.

The SI strain of measles virus derived from a patient with subacute sclerosing panencephalitis possesses typical genome alterations and unique amino acid changes that modulate receptor specificity and reduce membrane fusion activity

Subacute sclerosing panencephalitis (SSPE) is a fatal sequela associated with measles and is caused by persistent infection of the brain with measles virus (MV). The SI strain was isolated in 1976 from a patient with SSPE and shows neurovirulence in animals. Genome nucleotide sequence analyses showed that the SI strain genome possesses typical genome alterations for SSPE-derived strains, namely, accumulated amino acid substitutions in the M protein and cytoplasmic tail truncation of the F protein. Through the establishment of an efficient reverse genetics system, a recombinant SI strain expressing a green fluorescent protein (rSI-AcGFP) was generated. The infection of various cell types with rSI-AcGFP was evaluated by fluorescence microscopy. rSI-AcGFP exhibited limited syncytium-forming activity and spread poorly in cells. Analyses using a recombinant MV possessing a chimeric genome between those of the SI strain and a wild-type MV strain indicated that the membrane-associated protein genes (M, F, and H) were responsible for the altered growth phenotype of the SI strain. Functional analyses of viral glycoproteins showed that the F protein of the SI strain exhibited reduced fusion activity because of an E300G substitution and that the H protein of the SI strain used CD46 efficiently but used the original MV receptors on immune and epithelial cells poorly because of L482F, S546G, and F555L substitutions. The data obtained in the present study provide a new platform for analyses of SSPE-derived strains as well as a clear example of an SSPE-derived strain that exhibits altered receptor specificity and limited fusion activity.

Involvement of morbilliviruses in the pathogenesis of demyelinating disease

Two members of the morbillivirus genus of the family Paramyxoviridae, canine distemper virus (CDV) and measles virus (MV), are well-known for their ability to cause a chronic demyelinating disease of the CNS in their natural hosts, dogs and humans, respectively. Both viruses have been studied for their potential involvement in the neuropathogenesis of the human demyelinating disease multiple sclerosis (MS). Recently, three new members of the morbillivirus genus, phocine distemper virus (PDV), porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV), have been discovered. These viruses have also been shown to induce multifocal demyelinating disease in infected animals. This review focuses on morbillivirus-induced neuropathologies with emphasis on aetiopathogenesis of CNS demyelination. The possible involvement of a morbillivirus in the pathogenesis of multiple sclerosis is discussed.

Viral induced demyelination

Viral induced demyelination, in both humans and rodent models, has provided unique insights into the cell biology of oligodendroglia, their complex cell-cell interactions and mechanisms of myelin destruction. They illustrate mechanisms of viral persistence, including latent infections in which no infectious virus is readily evident, virus reactivation and viral-induced tissue damage. These studies have also provided excellent paradigms to study the interactions between the immune system and the central nervous system (CNS). Although of interest in their own right, an understanding of the diverse mechanisms used by viruses to induce demyelination may shed light into the etiology and pathogenesis of the common demyelinating disorder multiple sclerosis (MS). This notion is supported by the persistent view that a viral infection acquired during adolescence might initiate MS after a long period of quiescence. Demyelination in both humans and rodents can be initiated by infection with a diverse group of enveloped and non-enveloped RNA and DNA viruses (Table 1). The mechanisms that ultimately result in the loss of CNS myelin appear to be equally diverse as the etiological agents capable of causing diseases which result in demyelination. Although demyelination can be a secondary result of axonal loss, in many examples of viral induced demyelination, myelin loss is primary and associated with axonal sparing. This suggests that demyelination induced by viral infections can result from: 1) a direct viral infection of oligodendroglia resulting in cell death with degeneration of myelin and its subsequent removal; 2) a persistent viral infection, in the presence or absence of infectious virus, resulting in the loss of normal cellular homeostasis and subsequent oligodendroglial death; 3) a vigorous virus-specific inflammatory response wherein the virus replicates in a cell type other than oligodendroglia, but cytokines and other immune mediators directly damage the oligodendroglia or the myelin sheath; or 4) infection initiates activation of an immune response specific for either oligodendroglia or myelin components. Virus-induced inflammation may be associated with the processing of myelin or oligodendroglial components and their presentation to the host's own T cell compartment. Alternatively, antigenic epitopes derived from the viral proteins may exhibit sufficient homology to host components that the immune response to the virus activates autoreactive T cells, i.e. molecular mimicry. Although it is not clear that each of these potential mechanisms participates in the pathogenesis of human demyelinating disease, analysis of the diverse demyelinating viral infections of both humans and rodents provides examples of many of these potential mechanisms.

Identification of potential antibody markers in HIV-associated dementia

Markers for HIV-associated dementia (HAD) are needed for diagnosis and management. Specific antibodies to brain and immune complexes (IC) in the cerebrospinal fluid (CSF) are potential markers. CSF IC were found in 4 of 4 HAD patients, 2 of 2 AIDS-central nervous system (CNS) lymphoma patients with dementia, 0 of 1 AIDS-CNS lymphoma patient without dementia, 0 of 1 AIDS-CNS toxoplasmosis patient without dementia, and 0 of 10 neurologic disease controls. By blinded immunoblots, antibrain antibodies in serum and CSF were found in 11 of 12 HAD cases and 7 of 19 HIV-1 patients without HAD. All 11 non-HIV-1 controls were negative. These and published data suggest antibrain antibodies and IC may serve as markers of HAD.

Autoimmune markers in HIV-associated dementia

The etiology of HIV-associated dementia (HAD) is still unknown although direct viral effects have not been supported. Although evidence supports a role for products of activated macrophages, other evidence suggested the possibility of associated autoimmune phenomena at least as a marker. In a blinded analysis, non-HIV-infected whole brain material was immunoblotted with samples of serum, and in certain cases cerebrospinal fluid (CSF), from HAD patients and controls. Distinct antibrain antibodies were detected in 11/12 of HIV+ HAD patients, 7/19 of HIV+ patients without HAD, and 0/11 HIV seronegative controls who were either healthy or had other neurologic diseases. Reactivity against control tissue was negative. Though the etiopathogenetic relation of these antibrain antibodies remains to be delineated, the data suggest that they may be a marker of HAD.

Relapsed and late-onset Nipah encephalitis

An outbreak of infection with the Nipah virus, a novel paramyxovirus, occurred among pig farmers between September 1998 and June 1999 in Malaysia, involving 265 patients with 105 fatalities. This is a follow-up study 24 months after the outbreak. Twelve survivors (7.5%) of acute encephalitis had recurrent neurological disease (relapsed encephalitis). Of those who initially had acute nonencephalitic or asymptomatic infection, 10 patients (3.4%) had late-onset encephalitis. The mean interval between the first neurological episode and the time of initial infection was 8.4 months. Three patients had a second neurological episode. The onset of the relapsed or late-onset encephalitis was usually acute. Common clinical features were fever, headache, seizures, and focal neurological signs. Four of the 22 relapsed and late-onset encephalitis patients (18%) died. Magnetic resonance imaging typically showed patchy areas of confluent cortical lesions. Serial single-photon emission computed tomography showed the evolution of focal hyperperfusion to hypoperfusion in the corresponding areas. Necropsy of 2 patients showed changes of focal encephalitis with positive immunolocalization for Nipah virus antigens but no evidence of perivenous demyelination. We concluded that a unique relapsing and remitting encephalitis or late-onset encephalitis may result as a complication of persistent Nipah virus infection in the central nervous system.

The matrix gene expression of subacute sclerosing panencephalitis (SSPE) virus (Osaka-1 strain): a comparison of two sibling viruses isolated from different lobes of an SSPE brain

The Fr/V and Oc/V sibling viruses of the Osaka-1 strain of the subacute sclerosing panencephalitis (SSPE) virus were defective in cell-free virus production. By radioimmunoprecipitation assay, the matrix (M) protein was not detected in cells persistently infected with the Osaka-1 strain. This undetectable expression was consistent with the selective reduction of antibody response to the M protein in the patient from whom the Osaka-1 strain was isolated. The sequence of the M gene, however, predicted that the protein could be synthesized because the translational start and stop codons for the protein were not altered. Northern blot hybridization demonstrated the selective defect of the monocistronic mRNAs for the M protein and the phosphoprotein (P) together with the dominant presence of the P-M bicistronic mRNA. This absence of the M mRNA was further confirmed by primer extension analysis. Therefore, the undetectable expression of the M protein in the infected cells was proved to be caused by a transcriptional defect. The two sibling viruses, isolated from remote portions of an SSPE brain, were indistinguishable in their viral characters, including the M gene sequences, which indicates the possibility of clonal expansion of the strain in the brain.

Environmental risk factors for subacute sclerosing panencephalitis (SSPE)

In Israel, SSPE has been shown to be much more frequent among Sephardic Jews and Arabs than among Ashkenazic Jews. In the present study, we tried to explore environmental factors that may be of etiological importance and explain these differences in prevalence. The study is a case-control one, which includes 95 patients and 2 groups of controls, with 95 people in each. The general population controls were group-matched to the case group by sex, age, and ethnic origin. The family controls consisted of the sibling closest in age to each patient. A statistically significant positive correlation was found between risk of SSPE and early measles infection, large family, overcrowding in the home, older age of the mother, higher birth order, fewer years of schooling of the parents, fewer cultural activities, and rural place of birth. All these factors are interpreted as contributing to a higher risk of early measles infections, which thus may well be the main risk factor for SSPE.

Infection with cytotoxic T-lymphocyte escape mutants results in increased mortality and growth retardation in mice infected with a neurotropic coronavirus

C57BL/6 mice infected with mouse hepatitis virus strain JHM (MHV-JHM) develop a chronic demyelinating encephalomyelitis several weeks after inoculation. Previously, we showed that mutations in the immunodominant CD8 T-cell epitope (S-510-518) could be detected in nearly all samples of RNA and virus isolated from these mice. These mutations abrogated recognition by T cells harvested from the central nervous systems of infected mice in direct ex vivo cytotoxicity assays. These results suggested that cytotoxic T-lymphocyte (CTL) escape mutants contributed to virus amplification and the development of clinical disease in mice infected with wild-type virus. In the present study, the importance of these mutations was further evaluated by infecting naive mice with MHV-JHM variants isolated from infected mice and in which epitope S-510-518 was mutated. Compared to mice infected with wild-type virus, variant virus-infected animals showed higher mortality and morbidity manifested by decreased weight gain and neurological signs. Although a delay in the kinetics of virus clearance has been demonstrated in previous studies of CTL escape mutants, this is the first illustration of significant changes in clinical disease resulting from infection with viruses able to evade the CD8 T-cell immune response.

Subacute sclerosing panencephalitis manifesting as viral retinitis: clinical and histopathologic findings

PURPOSE AND METHODS

To describe the clinical and histopathologic features of a patient with viral retinitis secondary to subacute sclerosing panencephalitis.

RESULTS

The patient was a human immunodeficiency virus-negative intravenous drug abuser with an acute retinitis that later progressed to encephalitis despite aggressive treatment for possible viral, protozoal, bacterial, and rickettsial infections. The patient had many of the characteristic findings of subacute sclerosing panencephalitis, including a history of measles in early childhood, myoclonus, periodic complexes on electroencephalographic testing, persistently elevated serum and cerebrospinal fluid antimeasles immunoglobulin G (IgG) titers, and a cerebrospinal fluid oligoclonal IgG gammopathy. Ultrastructural examination demonstrated numerous filamentous microtubular intranuclear viral inclusions in the nuclear layers of the retina consistent with the measles virus. This case is unusual in that our patient developed subacute sclerosing panencephalitis later in life and because there was an 8-year period between presumed viral infections in the two eyes.

CONCLUSIONS

An acute retinitis in an intravenous drug abuser is not always caused by human immunodeficiency virus-related infections; not all viral retinitis responds to therapy; and mortality as well as the usual morbidity may be associated with viral retinitis. One might consider the diagnosis of subacute sclerosing panencephalitis in a young person with an acute retinitis with little or no vitreal inflammation and lack of response to anticytomegalovirus and antitoxoplasmosis therapy.

Selected pediatric viral infections

Viral infections of the central nervous system in infants and children are uncommon but potentially serious illnesses. Common causes have included the enteroviruses (particularly polioviruses and coxsackieviruses), herpes viruses (type 1 and type 2 herpes simplex, varicella, and cytomegalovirus), arboviruses, rubella, mumps, measles (including subacute sclerosing panencephalitis), and human immunodeficiency virus. Several of these viruses, such as cytomegalovirus, herpes simplex, and vertically transmitted human immunodeficiency virus, may cause congenital infections. Others are acquired later in childhood. In recent years, immunization programs have significantly reduced the occurrence of some of these diseases. A brief survey of the clinical and pathological manifestations of these illnesses will be discussed along with current incidence data.

Detection of immunoreactive antigen, with a monoclonal antibody to measles virus, in tissue from a patient with Crohn's disease

Using immunofluorescence (IF), we investigated reactive antigens present in Crohn's disease patients with monoclonal antibodies derived from cells infected with measles virus, but not with the subacute sclerosing panencephalitis virus. During immunoblotting, one monoclonal antibody (mAb 86) reacted with a polypeptide with a molecular weight of 36,000 dalton (M; matrix protein) in measles virus-infected cells. This monoclonal antibody displayed a positive reaction only with tissues from patients with Crohn's disease by the IF test. It did not react with samples from patients with other chronic inflammatory bowel diseases, such as ulcerative colitis. Other monoclonal antibodies to the measles virus protein, and monoclonal antibodies to Herpes simplex virus type 1 did not react with the same tissue samples. The role of measles virus infection and/or a viral antigen (possibly the M protein) as a causative agent in Crohn's disease poses a challenging avenue for further research.

Functional analysis of matrix proteins expressed from cloned genes of measles virus variants that cause subacute sclerosing panencephalitis reveals a common defect in nucleocapsid binding

We have developed an in vitro nucleocapsid-binding assay for studying the function of the matrix (M) protein of measles virus (MV) (A. Hirano, A. H. Wang, A. F. Gombart, and T. C. Wong, Proc. Natl. Acad. Sci. USA, 89:8745-8749, 1992). In this communication we show that the M proteins of three MV strains that cause acute infection (Nagahata, Edmonston, and YN) bind efficiently to the viral nucleocapsids whereas the M proteins of four MV strains isolated from patients with subacute sclerosing panencephalitis (SSPE) (Biken, IP-3, Niigata, and Yamagata) fail to bind to the viral nucleocapsids. MV Biken (an SSPE-related virus) produces variant M sequences which encode two antigenically distinct forms of M protein. A serine-versus-leucine difference is responsible for the antigenic variation. MV IP-3 (an SSPE-related virus) also produces variant M sequences, some of which have been postulated to encode a functional M protein responsible for the production of an infectious revertant virus. However, the variant M proteins of Biken and IP-3 strains show no nucleocapsid-binding activity. These results demonstrate that the nucleocapsid-binding function is conserved in the M proteins of MV strains that cause acute infection and that the M proteins of MV strains that cause SSPE exhibit a common defect in this function. Analysis of chimeric M proteins indicates that mutations in the amino-terminal, carboxy-proximal, or carboxy-terminal region of the M protein all abrogate nucleocapsid binding, suggesting that the M protein conformation is important for interaction with the viral nucleocapsid.

Measles virus infection of cells in perivascular infiltrates in the brain in subacute sclerosing panencephalitis: confirmation by non-radioactive in situ hybridization, immunocytochemistry and electron microscopy

As part of continuing multidisciplinary studies on the neuropathogenesis of subacute sclerosing panencephalitis (SSPE), in situ hybridisation, immunocytochemistry and electron microscopy were used to detect measles virus nucleic acid, protein and nucleocapsids in brain perivascular infiltrates of three cases. Perivascular cuffing cells which contained measles virus nucleic acid and antigens were found in all cases. Infected cuffs occurred predominantly in areas of general parenchymal cell infection and in many of these a high proportion of the infiltrating cells were infected. Other cuffs in these areas were either uninfected or contained only a few infected cells. Occasional infected cells were also seen in cuffs in non-infected areas. In contrast, no specific immunocytochemical reactions or in situ hybridisation for measles virus was observed in brain tissue from a patient with herpes encephalitis. By electron microscopy viral nucleocapsid, consistent with measles virus, was found within the cytoplasm of plasma cells in the inflammatory cuffs in SSPE brain tissue. Possible explanations for our results are that infiltrates become infected on arrival in the CNS or alternatively, that the infected infiltrates reflect a generalised infection of the reticuloendothelial system. The frequent presence of uninfected cuffs favours the former explanation.

Pathogenesis of virus-induced demyelination

Demyelination is a component of several viral diseases of humans. The best known of these are subacute sclerosing panencephalitis (SSPE) and progressive multifocal leukoencephalopathy (PML). There are a number of naturally occurring virus infections of animals that involve demyelination and many of these serve as instructive models for human demyelinating diseases. In addition to the naturally occurring diseases, many viruses have been shown to be capable of producing demyelination in experimental situations. In discussing virus-associated demyelinating disease, the chapter reviews the architecture and functional organization of the CNS and considers what is known of the interaction of viruses with CNS cells. It also discusses the immunology of the CNS that differs in several important aspects from that of the rest of the body. Experimental models of viral-induced demyelination have also been considered. Viruses capable of producing demyelinating disease have no common taxonomic features; they include both DNA and RNA viruses, enveloped and nonenveloped viruses. The chapter attempts to summarize the important factors influencing viral demyelination, their common features, and possible mechanisms.

HLA antigens in subacute sclerosing panencephalitis patients in Israel

HLA Class I antigens were determined in the 49 subacute sclerosing panencephalitis (SSPE) patients. In analyzing the Arabs and the Jews separately, there is a decrease in HLA-A2 in the Jewish patients (X2 = 3.96; P less than 0.05), a significant increase in the HLA-A29 in the Arab SSPE patients (X2 = 6.29; P less than 0.02), and a slight, insignificant increase of HLA-A29 in the Jewish patients. The present study supports previous findings of Kurent's and needs following studies in larger groups of Arab SSPE patients.

Functional and nonfunctional measles virus matrix genes from lethal human brain infections

Subacute sclerosing panencephalitis (SSPE) is a lethal disease induced by the persistence of measles virus in the human brain. In many SSPE cases, the viral matrix (M) protein cannot be detected; in others, M proteins of the expected size are found and sequence analysis of M cDNAs has confirmed that the reading frames are intact, showing only several missense mutations. To determine whether these alterations result in nonfunctional proteins, we have replaced the M gene of an infectious full-length genomic cDNA (from vaccine strain Edmonston) with different M genes derived from four patients with SSPE. One of the SSPE M genes tested proved to be functionally competent, giving rise to a virus yielding titers similar to those of viruses containing the M gene from control lytic strains. The other three SSPE M genes were not functionally competent in the same test. In all three cases, the inactivating changes resided in the carboxyl-terminal half of the M protein, as shown by the exchange of either of the two genes halves. In summary, mutational M gene alterations, which either prevent synthesis of M protein altogether or only allow synthesis of nonfunctional M protein, have been detected by us and by others in 9 of 10 SSPE cases. The one functional M gene appears to be an exception to the rule, indicating that M gene alteration might not be an absolute requirement for disease development.

Control of virus-induced cell fusion by host cell lipid composition

Virus-induced cell fusion has been examined in a series of stable cell lines which were originally selected for resistance to the fusogenic effects of polyethylene glycol (PEG). For a wide variety of viruses, including murine hepatitis virus (a coronavirus), vesicular stomatitis virus (a rhabdovirus), and two paramyxoviruses (Sendai virus and SV5), susceptibility to virus-induced fusion was found to be inversely correlated with susceptibility to PEG-induced fusion. This phenomenon was observed both for cell fusion occurring in the course of viral infection and for fusion induced "from without" by the addition of high titers of noninfectious or inactivated virus. The fusion-altered cell lines (fusible by virus but not by PEG) are characterized by their unusual lipid composition, including marked elevation of saturated fatty acids and the presence of an unusual ether-linked neutral lipid. To test the association between lipid composition and fusion, acyl chain saturation was manipulated by supplementing the culture medium with exogenous fatty acids. In such experiments, it was possible to control the responses of these cells to both viral and chemical fusogens. Increasing the cellular content of saturated fatty acyl chains increased the susceptibility of cells to viral fusion and decreased susceptibility to PEG-induced fusion, whereas lowering fatty acid saturation had the opposite effect. Thus, parallel cultures of cells can be either driven toward the PEG-fusible/virus-fusion-resistant phenotype of the parental cells or rendered susceptible to viral fusion but resistant to PEG-induced fusion, solely by the alteration of cellular lipids. The ability of cellular lipid composition to regulate virus-induced membrane fusion suggests a possible role for lipids in viral infection and pathogenesis.

Influenza virus genetic sequences in the blood of children with congenital pathology of the CNS

Influenza A virus genetic sequences revealed by dot hybridization were detected in peripheral blood cells, serum and liquor of three children with congenital pathology of the CNS. The children were born to mothers who contacted influenza during pregnancy. The virus-specific sequences were found for a long period of time (83 days in one case). The serum of the child did not contain antibodies against M protein suggesting that viral nucleocapsids but not the virus particles persist in the organism of the sick child.

New, sensitive, radioactive-free bioluminescence-enhanced detection system in protein blotting and nucleic acid hybridization

A relatively simple, very sensitive bioluminescence-enhanced detection system for protein blotting and nucleic acid hybridization is described. The method utilizes antibodies conjugated with alkaline phosphatase or nucleotide probes complexed with alkaline phosphatase. Then the alkaline phosphatase takes part in a reaction by releasing D-luciferin (Photinus pyralis) from D-luciferin-O-phosphate. Liberated D-luciferin reacts with luciferase, ATP and oxygen under light emission. Light is measured using the Argus-100 a photon counting camera system or photographic films. Bound alkaline phosphatase conjugated antibodies or hybridized nucleotide probes can be visualized. The limit of detection is at present 5 to 50 fg of protein (IgG), corresponding, for example to 30 to 300 x 10(-21) mol. This means a much higher sensitivity of the detection system in comparison to systems used at present. Experiments concerning nucleic acid hybridization and visualization of the emitted light by a photon counting camera (Argus-100) are under investigation.

Biased hypermutation and other genetic changes in defective measles viruses in human brain infections

We assessed the alterations of viral gene expression occurring during persistent infections by cloning full-length transcripts of measles virus (MV) genes from brain autopsies of two subacute sclerosing panencephalitis patients and one measles inclusion body encephalitis (MIBE) patient. the sequence of these MV genes revealed that, most likely, almost 2% of the nucleotides were mutated during persistence, and 35% of these differences resulted in amino acid changes. One of these nucleotide substitutions and one deletion resulted in alteration of the reading frames of two fusion genes, as confirmed by in vitro translation of synthetic mRNAs. One cluster of mutations was exceptional; in the matrix gene of the MIBE case, 50% of the U residues were changed to C, which might result from a highly biased copying event exclusively affecting this gene. We propose that the cluster of mutations in the MIBE case, and other combinations of mutations in other cases, favored propagation of MV infections in brain cells by conferring a selective advantage to the mutated genomes.

Intrathecal interferon in subacute sclerosing panencephalitis

Three patients at Stage II of subacute sclerosing panencephalitis (SSPE) were treated with semipurified alpha-interferon (IFN) using different combinations of intrathecal and intravenous routes: 1 x 10(6) IU of alpha-IFN were given every other day up to a total of 15 x 10(6) IU. Transient improvement of neurological symptoms and electroencephalogram were noted in all 3, while cognitive function slightly improved in 2 of them. Clinical benefits gradually disappeared 2 to 6 months after cessation of IFN. Intrathecal antibody production did not change substantially, but CSF Leu 3a/Leu 2a ratio appeared to increase. No significant side effects were observed, except for a mild meningeal inflammatory reaction after each intrathecal administration of IFN.

A new, very sensitive, bioluminescence-enhanced detection system for protein blotting. Ultrasensitive detection systems for protein blotting and DNA hybridization, I

A relatively simple, very sensitive bioluminescence-enhanced detection system for protein blots is described. The method utilizes antibodies conjugated with alkaline phosphatase. The alkaline phosphatase then takes part in a reaction by releasing D-luciferin (Photinus pyralis) from D-luciferin-O-phosphate. Liberated D-luciferin reacts with luciferase, ATP and oxygen with light emission. The light is detected by a sensitive photographic film, thereby permitting the visualization of the alkaline phosphatase-conjugated antibodies. Under non-optimized conditions the limit of detection is at present 5 to 50 pg of protein, corresponding e.g. to 30 to 300 x 10(-18) mol of rabbit immunoglobulin G. The detection system is therefore 100 times more sensitive than other systems used at present.

Persistent measles virus genome in autoimmune chronic active hepatitis

A radiolabelled 50-base oligonucleotide complementary with the measles virus gene encoding the nucleocapsid was used as a probe to identify persistent measles virus genome in the lymphocytes from patients with autoimmune chronic active hepatitis (AICAH). Positive hybrids were found in 12 of 18 patients, and correlated strongly with high antibody titres to measles. Among the 45 controls, positive hybrids were found in 1 patient with measles, 1 of 3 patients with systemic lupus erythematosus, and 2 of 4 patients with cryptogenic cirrhosis. Persistence of part of the measles virus genome in AICAH may have important implications in the pathogenesis of the liver disease, and possibly in other disorders such as systemic lupus erythematosus, multiple sclerosis, and Paget's disease where an abnormal immune response to measles has been observed.

Late onset, symptomatic, demyelinating encephalomyelitis in mice infected with MHV-JHM in the presence of maternal antibody

The presence of maternal antibodies protected suckling C57BL/6 mice from the clinical manifestations of the acute encephalomyelitis caused by mouse hepatitis virus, strain JHM (MHV-JHM), a coronavirus, even though histological evidence of encephalomyelitis was found at early times after inoculation. 100% of infected suckling mice developed a fatal disease in the absence of maternal antibody. By 14 days after inoculation, the brains of all antibody-protected mice examined were nearly normal on histological examination. At 3-8 weeks post-inoculation, approximately 40% of the antibody-protected mice developed a neurological disease characterized by hindlimb paralysis and wasting. Evidence of inflammation and demyelination was apparent in the spinal cord and brainstem. The mice that remained asymptomatic at this time showed few signs of inflammation and none developed clinical disease over the following 9 months. Viral antigen could be detected in most of the mice examined at all times after inoculation, whether symptomatic or not, and was particularly evident in the animals with hindlimb paralysis. MHV-JHM could be consistently cultured from the mice with hindlimb paralysis. These results show that maternal immune factors can completely protect susceptible mice from the acute, fatal, clinical encephalomyelitis caused by MHV-JHM, but cannot prevent the establishment of a latent state and subsequent development of virus-induced, clinically evident, demyelinating disease. This model will be useful for studying the virus and host factors important for the development of MHV-JHM latency and subsequent virus-induced demyelination.

Measles virus matrix protein gene expression in a subacute sclerosing panencephalitis patient brain and virus isolate demonstrated by cDNA hybridization and immunocytochemistry

Subacute sclerosing panencephalitis (SSPE) is a rare, fatal disease of children caused by a persistent measles virus infection of the central nervous system. A defect in synthesis of measles virus matrix (M) protein may be a factor in virus persistence in the brain. This study details attempts to detect expression of M protein in the brain of an SSPE patient, in the cell-associated virus isolated from this brain, and in brains of ferrets inoculated with the isolate. In situ hybridization with a tritiated cloned cDNA probe was used to search for RNA encoding M protein. Immunostaining with monospecific antiserum and the avidin-biotin-peroxidase technique was done to locate the polypeptide. The data obtained indicate that although nucleotide sequences coding for M protein were detected in the patient and ferret brains, expression of M protein in these tissues could not be detected. In the culture SSPE virus isolate, the results were the same until the infected cells were examined by electron microscopy and a very limited expression of M protein was revealed. This suggests either diminished synthesis and/or rapid degradation of M protein in this cell-associated virus strain.

Rapid degradation restricts measles virus matrix protein expression in a subacute sclerosing panencephalitis cell line

Measles virus matrix protein expression is restricted in the persistently infected brain cells of patients with the chronic neurological disease subacute sclerosing panencephalitis (SSPE). Prior studies of the nature of this restriction have identified polyadenylylated matrix gene-encoded RNA transcripts unable to direct effective translation. The defective nature of these mRNAs readily accounted for the inability to detect matrix protein in these persistently infected cells and suggested that in SSPE the restriction of matrix protein expression is achieved by preventing its synthesis. Recently, however, we reported evidence that matrix protein is synthesized in at least one example of this persistent infection, the SSPE cell line IP-3-Ca. In this case, failure of matrix protein to accumulate normally accounted for its restricted expression [Sheppard, R. D., Raine, C. S., Bornstein, M. B. & Udem, S. A. (1985) Science 228, 1219-1221]. To clarify the nature of the restriction displayed by IP-3-Ca cells, the synthesis and fate of the matrix protein of this SSPE cell line were examined in detail. No evidence of constraints on the efficiency of matrix protein mRNA transcription or translation was found. Instead, the restricted expression proved to be the result of rapid posttranslational degradation of matrix protein. We suggest that matrix protein gene mutations incurred in the course of genome replication are likely to be responsible for the diversity of observed mechanisms restricting matrix protein expression. In that event, the nature and position of the nucleotide substitution(s) would be the determinants of the level at which restricted expression is achieved.

Expression of defective measles virus genes in brain tissues of patients with subacute sclerosing panencephalitis

The persistence of measles virus in selected areas of the brains of four patients with subacute sclerosing panencephalitis (SSPE) was characterized by immunohistological and biochemical techniques. The five measles virus structural proteins were never simultaneously detectable in any of the brain sections. Nucleocapsid proteins and phosphoproteins were found in every diseased brain area, whereas hemagglutinin protein was detected in two cases, fusion protein was detected in three cases, and matrix protein was detected in only one case. Also, it could be shown that the amounts of measles virus RNA in the brains differed from patient to patient and in the different regions investigated. In all patients, plus-strand RNAs specific for these five viral genes could be detected. However, the amounts of fusion and hemagglutinin mRNAs were low compared with the amounts in lytically infected cells. The presence of particular measles virus RNAs in SSPE-infected brains did not always correlate with mRNA activity. In in vitro translations, the matrix protein was produced in only one case, and the hemagglutinin protein was produced in none. These results indicate that measles virus persistence in SSPE is correlated with different defects of several genes which probably prevent assembly of viral particles in SSPE-infected brain tissue.

Susceptibility of endothelial cells derived from different blood vessels to common viruses

We examined whether endothelial cells derived from different blood vessels vary in their susceptibility to viral infection. Five common viral pathogens of humans (herpes simplex 1, measles, mumps, echo 9, and coxsackie B4 viruses) were evaluated for growth in endothelial cells derived from bovine fetal pulmonary artery, thoracic aorta, and vena cava. All five viruses replicated in each type of endothelial cell. There were apparent differences in the quantities of measles and mumps viruses produced in pulmonary artery endothelium compared with thoracic aorta and vena cava when endothelial cells were obtained from different animals. However, when pulmonary artery endothelial cells were compared with vena cava cells from the same animal, growth of each virus was similar in the two cell types. Four of the viruses replicated in the various endothelial cells without producing appreciable changes in cell morphology. These results indicate that endothelial cells from different blood vessels are equally susceptible to the human viruses evaluated, and that viral replication can occur without major alterations in cell morphology. Endothelial cells could serve as permissive cells permitting viruses to leave the circulation and initiate infection in adjacent tissues, including subendothelial smooth muscle cells.

Isolation of measles virus polypeptides from infected brain tissue by affinity chromatography

A method has been developed to isolate measles virus proteins from infected hamster brain tissue. Suckling hamsters inoculated intracerebrally with the HBS strain of measles virus were used in these studies. Viral proteins were isolated from infected brain lysates by affinity chromatography on Sepharose beads coupled with IgG from rabbit hyperimmune anti-measles serum. The eluted proteins were separated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), electrophoretically transferred onto blotting matrix, and immunolabelled with anti-measles antibodies. Individual viral proteins were identified by labelling with monoclonal or monospecific antibodies. All viral proteins except the fusion (F1) protein were identifiable on the immunoblots in relative amounts comparable to purified virions. In addition, a second phosphoprotein (P) band not found in purified virions was present in infected brains and cell cultures infected with HBS or LEC strains of virus. This method should be useful for isolating small quantities of viral proteins from large amounts of tissue, and should make possible the characterization of measles virus proteins in persistently infected CNS tissue.

The intracellular half-lives of nonreplicating nucleocapsids of DI particles of wild type and mutant strains of vesicular stomatitis virus

We have used defective interfering (DI) particles purified free of all infectious virus to determine the intracellular biological stability of nonreplicating nucleocapsids of vesicular stomatitis virus (VSV). Following infection of BHK-21 cells or tc-7 cells with a low multiplicity of pure DI particles, we superinfected them at varying times afterward with a high multiplicity of infectious helper virus to allow replication of those DI particle nucleocapsids retaining biological activity. Careful quantitation of DI particles in the yields from each time point showed that the biological half-life of intracellular VSV Indiana wild type DI particle nucleocapsids was 6 hr in BHK-21 cells and 5.3 hr in tc-7 cells (not significantly different). However, a DI particle from a temperature-sensitive mutant (tsG31) of VSV exhibited a biological nucleocapsid half-life of 12.5 hr and a DI particle isolated following 5 years of persistent infection had a half-life of 18 hr. These findings have significance for the stability of DI particle activity in vivo during acute infections where virus and DI particles are not always present together in the same cells due to cycling interactions. The increased half-life of DI nucleocapsids after years of persistent infection contrasts with the decreased stability and debilitation generally observed in infectious virus from persistent infection. Finally, transcapsidation studies showed that the intracellular half-life differences between DI particles are due mainly to their RNA genomes rather than to the N protein which encapsidates them.

Effect of interferon on Vero cells persistently infected with SSPE virus and lytically infected with measles virus

The effect of lymphoblastoid interferon (IFN) on viral polypeptides synthesized in a Vero cell culture persistently infected with subacute sclerosing panencephalitis virus (SSPE-Vero) was compared to that of Vero cells infected with exogenous measles virus. After IFN treatment there was no significant decrease in the synthesis of SSPE viral proteins, but inhibition of synthesis of measles polypeptides was readily seen. In Vero and SSPE-Vero cells IFN was able to inhibit replication of Sindbis virus although the effect in Vero cells was significantly more sensitive. In both cell lines IFN was able to stimulate 2'--5' oligoadenylate synthetase (E enzyme) but not the protein kinase system. The SSPE-Vero cells showed a lower basal level of E enzyme activity than the Vero cells.

Round cell variant of measles virus: neurovirulence and pathogenesis of acute encephalitis in newborn hamsters

A subacute sclerosing panencephalitis (SSPE) strain of measles virus has been previously shown to be composed of two interrelated but separable viral variants. One of these, the syncytiagenic or S variant, resembles defective, cell-associated strains of measles virus; while the other, the round cell inducing or RC variant, induces a highly productive infection in cell culture. It is now reported that the S variant is more neurovirulent in newborn hamsters than the RC variant and that viral replication in infected CNS tissues occurs in two phases. Early in the infection cell-free virus, composed primarily of the RC variant, is produced. Later, coincident with the appearance of antiviral antibody, cell-free virus rapidly disappears, leaving behind only cell-associated virus which resembles the S variant. Quantification of viral antigen expression in the infected tissues suggests that this change in the state of infection is not associated with antigenic modulation, but rather is the result of preferential elimination of RC variant infected cells.

Temporal invariance and clonal uniformity of brain and cerebrospinal IgG, IgA, and IgM in multiple sclerosis

Elevated cerebrospinal fluid (CSF) IgG and oligoclonal IgG bands on electrophoresis are valuable clinical markers for B cell proliferation in the brains of patients with multiple sclerosis (MS). Using two-dimensional electrophoresis, (2DE) we have established that the humoral immune response in MS brain is characterized by finite clonal complexity for the major Ig classes. An important question is whether this immune response is clonally stable or varies with time, related to the development of new lesions and random entry of B cells into the MS brain. To investigate this, we performed serial electrophoretic studies on CSF obtained from 19 patients with MS; the intervals ranged from 7 to 12 yr, with a mean of 8 yr. These analyses included studies of IgG, IgA, and IgM, and revealed that the humoral immune response in MS is clonally stable over long periods. Spontaneous fluctuations or reduction in CSF IgG levels by drugs did not qualitatively affect B cell clonal proliferation in MS brain, in that dominant bands and spots were not obliterated. It has been asserted that IgG synthesis in MS is nonsense antibody because the spectotypes of IgG isolated from different regions of MS brains differ. Factors other than clonal heterogeneity could account for differences found using one-dimensional analysis. B cell clonal products resolve into unique and well-resolved spots by 2DE; the method is uniquely suitable for analysis of restricted immune responses. Therefore, Ig were isolated from 11 regions of three MS brains and the 2DE patterns were compared. The similarity of the 2DE patterns indicate unequivocally that major clones are distributed uniformly although some clones are more prominent in some brain areas. IgA and IgM isolated from the same areas also showed similar patterns. Furthermore, the patterns of light and heavy chains in brain regions differed from serum but were similar to the autologous CSF, providing new evidence that CSF IgG in MS derives from synthesis in situ. Our results indicate that, once initiated, B cell clonal proliferation persists indefinitely and is little altered qualitatively at a clonal level over time, even when CSF IgG levels change or are altered by drugs. Our results are consistent with allotype and idiotype analysis of Ig production in MS and conflict with nonsense antibody proposals of the origin and nature of in situ synthesized Ig in MS.

Quantification of measles virus antigens in infected CNS tissue: development of an enzyme linked immunoassay

An enzyme linked immunoassay procedure has been developed which allows accurate quantification of low levels of measles virus antigens in infected central nervous system (CNS) tissues. In its development a systematic study was made of the effects of a large excess of nonviral proteins on the assay results. It was found that controls using single proteins such as bovine serum albumin were inadequate. Further, results indicate that experimental samples and viral antigen standards must be closely matched for their content of CNS tissue proteins since such proteins exert distinctive quantitative effects, both dramatic and subtle.

Detection of measles virus RNA in lymphocytes from peripheral-blood and brain perivascular infiltrates of patients with subacute sclerosing panencephalitis

To clarify the relation between lymphocytes and measles virus in subacute sclerosing panencephalitis, we used in situ hybridization and a cloned measles virus DNA probe, specific for nucleocapsid protein, to detect measles virus RNA sequences in circulating lymphocytes and brain perivascular cuffs of patients with subacute sclerosing panencephalitis. Seventy to 90 per cent of peripheral mononuclear cells from three such patients were found to contain measles virus RNA sequences. In contrast, only a few infected cells were observed in four seropositive adults (0.1 to 5 per cent) and three age-matched children (10 to 15 per cent) used as controls. In one sample of brain tissue from a patient with subacute sclerosing panencephalitis, viral RNA sequences were also detected in nerve cells and in numerous cells from the perivascular infiltrates. In contrast, no hybridization was observed in brain tissue from a patient with herpetic encephalitis and from a patient with postlymphoma encephalitis. We conclude that measles virus has a strong tropism for lymphocytes and nerve cells in subacute sclerosing panencephalitis and that lymphocytes may be involved in the pathogenesis of the disease.

The diminishing incidence of hypsarrhythmia

The incidence of hypsa over a 40-year period in 667 pts was noted to rise to a peak in 1958 and then to fall so that relatively few cases appeared in the early 1970's, with hypsa seen only rarely in the past 10 years. This diminishing incidence was confirmed in a major children's hospital. The incidence curve of rubeola is seen to follow a similar course; the possibility is discussed that subclinical infectious disease, and rubeola in particular as a prototype, may have played a more prominent role in the etiology of hypsa than has been considered in the past.

Measles virus matrix protein detected by immune fluorescence with monoclonal antibodies in the brain of patients with subacute sclerosing panencephalitis

Brain materials from four cases of subacute sclerosing panencephalitis were examined by immune fluorescence with monoclonal antibodies against five structural components of measles virus. All five antigens including the matrix component were present in the brain tissues of all cases. A defective Vero cell-associated virus isolate from one of the cases produced all of the structural components except the matrix protein.

Round cell variant of measles virus: spontaneous conversion from productive to cell-associated state of infection

A subacute sclerosing panencephalitis strain of measles virus was found to be composed of two viral variants distinguishable by their cytopathic effects in Vero cells. One of the variants was similar to defective cell-associated measles virus strains, whereas the other was highly productive of viral progeny but did not induce cell fusion. Cloning of the variants by an agarose plaque procedure revealed a consistent and rapid interconversion of the variants into one another. While the mechanism of this interconversion remains unknown, analysis of the expression of viral antigens by the variants using indirect immunofluorescence with monoclonal antibodies specific for measles structural antigens suggested that the interconversion involved modulation of the expression of the viral matrix or M antigen.