Subacute sclerosing panencephalitis: propagation of measles virus from brain biopsy in tissue culture

Neuroprogressive disease of post-infectious origin: a review of a resurging subacute sclerosing panencephalitis (SSPE)

Subacute sclerosing panencephalitis (SSPE) is a progressive, essentially untreatable, disease of the nervous system. When first described in the 20th Century, it was characterized more for its neuropathological features than for its pathophysiology or cause. It was not until the 1960s that a clear relationship to the measles virus was established. It is now thought that this uncommon infectious encephalopathy is caused by a "slow," altered or persistent form of the wild measles virus which has harbored in the nervous system for years. Then a "breakout" occurs and the more lytic and virulent organisms produce the progressive and spreading inflammatory and destructive lesions which are confined to the nervous system. Epidemiological study of the disease confirms its relationship to measles. In the years since the development of national measles immunization programs, there has been a dramatic decline in the incidence of measles exanthem and until recently a corresponding decline in the incidence of SSPE. In recent years there has been a mild to moderate increase in cases of SSPE as reported to the USA/International SSPE Registry. As yet, there has not been a totally effective treatment. The purpose of this paper is to give an overall review on SSPE and its relationship to measles. This review will include a prospectus of its history, considerations as to its etiology, correlation of clinicopathological features, and thoughts on the past and present epidemiology and treatment.

Persistent infection of B lymphocytes by bovine respiratory syncytial virus

Bovine respiratory syncytial virus (BRSV) is a major cause of respiratory disease in young cattle. Here we demonstrate BRSV persistence at low levels in tracheobronchial and mediastinal lymph nodes up to 71 days after the experimental infection of calves. Positive results were obtained on viral genomic RNA and messenger RNA coding for the nucleoprotein, glycoprotein (G), and fusion protein (F). G and F proteins were also detected in the pulmonary lymph nodes by immunohistochemistry. Double-staining experiments revealed that viral antigen was present in B-lymphocytes. Coculture experiments with the lymph node cells showed that the virus was still able to infect permissive target cells, even though no cytopathic effect was recorded. In vitro studies indicate that BRSV was still able to replicate in bovine B-lymphocyte cell lines 6 months after infection. These results may also be relevant to the understanding not only of the epidemiology and the peculiarities of the immune response of BRSV infections but also of human respiratory syncytial virus infections.

Experimental old dog encephalitis (ODE) in a gnotobiotic dog

Experimental infection of a gnotobiotic Beagle dog with the neurovirulent R252 strain of canine distemper virus (R252-CDV) resulted in long-term central nervous system (CNS) infection; cerebral and brain stem lesions were consistent with old dog encephalitis (ODE). Eight clinical cycles of relapsing cortical and subcortical signs were documented over 33 months and were corroborated by the presence of both chronic and active inflammatory demyelinating lesions within the neuraxis. Immunocytochemistry revealed that CDV antigen was restricted to neurons. Attempts to use fresh brain tissue to directly transmit the infection to CDV-susceptible gnotobiotic dogs were unsuccessful. Reisolation of infectious virus from the infected dog required prolonged culture and coculture of brain explant cells with CDV-susceptible Vero cell monolayers. These findings demonstrate that ODE is a variant of virulent CDV-induced canine neurologic disease that can evolve de novo within the CNS of subclinically infected dogs in the absence of external sources of reinfection. The highly cell-associated nature of the virus, when first recovered from this dog, suggests that the virus was present within the CNS in a replication-defective form.

Fulminating subacute sclerosing panencephalitis: case report and literature review

We describe a young urban boy with atypically fulminant subacute sclerosing panencephalitis (SSPE). He had measles at 3 years of age despite receiving measles immunization in infancy. The literature describing acute SSPE is reviewed and summarized. This report reiterates the need to include SSPE as a diagnostic possibility in acute encephalopathic processes. The dismal prognosis of SSPE further emphasizes the need for measles vaccination and revaccination of all children who are initially immunized at an age of less than 15 months.

Subacute sclerosing panencephalitis

Subacute sclerosing panencephalitis (SSPE), a neurodegenerative disease caused by a persistent "slow virus infection" with a mutated measles virus, is endemic in much of the developing world. Its incidence will increase in the USA, not only in immigrants, but also because of the 1988-1990 measles epidemic. This report reviews the pathogenesis, clinical and laboratory diagnosis, and future perspectives in treatment and prevention.

Detection by polymerase chain reaction of wild-type measles virus genome in the cerebrospinal fluid of a patient with SSPE who had received measles vaccine

BACKGROUND

Previous studies have reported that approximately 4-5% of patients with subacute sclerosing panencephalitis (SSPE) were given measles vaccination but had no history of natural measles. However, in the case who received measles vaccine, it has been extremely difficult to determine whether the actual cause of SSPE is the inoculated vaccine virus or not.

OBJECTIVES

To detect the measles virus genome in a patient with SSPE and to analyze its nucleotide and deduced amino acid sequence.

STUDY DESIGN

We applied the polymerase chain reaction (PCR) to detect the measles virus genome in specimens from a 12-year-old boy with SSPE who had received measles vaccine 10 years before and had no history of apparent natural measles. The oligonucleotide primers for PCR were prepared based on the nucleotide sequence of the F and NP genes of the measles virus Edmonston strain.

RESULTS

F and NP genes were detected in both the cerebrospinal fluid and peripheral blood lymphocytes. Nucleotide and deduced amino acid sequence analysis of the F gene showed that the patient's virus was different from that of the vaccine strain. Judging from these results, it was likely that the SSPE-associated strain in this case was derived from the wild-type rather than the vaccine strain.

CONCLUSIONS

PCR is a useful method to establish a definitive diagnosis of SSPE and to study the nature of the SSPE-associated virus.

Detection of measles virus genomic sequences in SSPE brain tissue by the polymerase chain reaction

The polymerase chain reaction (PCR) was modified to detect RNA genomic sequences by generating cDNA copies of these sequences as a preliminary step. Oligonucleotide primer pairs complementary to sequences in each of the five major structural protein genes of the measles virus (nucleocapsid protein, phosphoprotein, matrix protein, fusion protein, and hemagglutinin protein) were synthesized. PCR products were tentatively identified by visualization of bands of the appropriate size by ethidium bromide staining after gel electrophoresis, and identity was confirmed by subsequent restriction enzyme cleavage of the products at predetermined sites to yield fragments of predicted size. This method successfully amplified 400-500 base regions from each of these five genes in RNA extracts of wild measles virus cultured in Vero cells and in RNA extracted from most of the SSPE brain tissues tested, but not in RNA from any control brain tissues. Measles virus genome was detected in SSPE brain tissues stored frozen for as long as 27 years and formalin-fixed paraffin-embedded subacute sclerosing panencephalitis (SSPE) brain tissues as old as 9 years. This method provides a simple, rapid and highly sensitive means of detecting and identifying sequences of RNA genomes by PCR. The success of this method in detecting measles virus in SSPE brain tissue suggests that PCR is appropriate to investigate the possible presence of RNA viruses in other neurological disorders of unknown etiology.

Mutated and hypermutated genes of persistent measles viruses which caused lethal human brain diseases

Persistent measles viruses (MVs) causing lethal human brain diseases are defective, and the structure of several mutated matrix genes has been elucidated previously. The present study of four persistent MVs revealed a high number of differences from a consensus sequence also in other genes. Amino acid changes accumulated in the carboxyl terminus of the nucleocapsid protein and in the amino terminus of the phosphoprotein, but did not significantly alter these products, which are implicated in viral replication and transcription. The contrary is true for the envelope glycoproteins: In three of four cases, mutations caused partial deletion of the short intracellular domain of the fusion protein, most likely compromising efficient viral budding. Moreover, in the hemagglutinin gene of a strain showing strongly reduced hemadsorption, 20 clustered A to G mutations, resulting in 16 amino acid changes, were detected. This hypermutation might be due to unwinding modification of a part of the MV RNA genome accidentally present in a double-stranded form. Finally, we classified four lytic and seven persistent MV strains on the basis of their sequences. Surprisingly, the four lytic viruses considered belong to the same class. The persistent viruses form more loosely defined groups, which all differ from the vaccine strain Edmonston.

Production of immunoglobulin G and increased antiviral antibody in cerebrospinal fluid of dogs with delayed-onset canine distemper viral encephalitis

Sera and cerebrospinal fluid (CSF) from four dogs with delayed-onset canine distemper viral (CDV) encephalitis (old dog encephalitis) were compared with samples from dogs with acute CDV and from recently vaccinated controls. Dogs with old dog encephalitis (ODE) had elevated CSF IgG concentrations (122 micrograms/ml) compared to controls (13 micrograms/ml) without elevated CSF albumin; their CSF IgG index was significantly greater. CSF proteins banding in the alkaline region of isoelectric focusing gels were immunochemically identified as IgG. Detectable viral neutralizing antibody was present in ODE CSF, and formed a larger proportion of IgG in CSF than in serum. Serum samples containing 2 mg IgG bound to all viral polypeptides of both R252 and Onderstepoort CDV isolates by immunoblot analysis. CSF samples of ODE patients bound viral antigens when diluted to contain as little as 5-40 micrograms IgG, while patient serum could be diluted to 40-200 micrograms IgG content compared to serum IgG of 100 micrograms/ml in vaccinated controls. Serial CSF dilutions consistently bound to H and NP polypeptides at the highest dilutions, similar to the binding of serums from recently vaccinated dogs. Thus, dogs with delayed-onset CDV encephalitis have elevated concentrations of CSF IgG, much of which is virus-specific, with an antigen binding pattern similar to that of sera of recently immunized dogs.

Viral aetiology of Paget's disease of bone: a review

Images

Treatment of subacute sclerosing panencephalitis: an overview

Subacute sclerosing panencephalitis (SSPE) is a rare central nervous system degenerative disease that occurs primarily in children and adolescents. It is believed to be caused by a measles-like virus. Initial symptoms usually present as a variety of personality changes followed by myoclonus with progression of mental and motor deterioration, which leads to death within a few months to years. New experimental treatment with inosiplex has been shown to be helpful for patients stricken with this progressive neurological disease. A response to inosiplex therapy is best in patients with a slowly progressing form of the disease. Inosiplex treatment is safe with few adverse effects. The duration of treatment appears to be lifelong since many patients relapse when inosiplex therapy is discontinued. This article reviews the etiology, pathogenesis, and experimental treatment of SSPE.

Ultrastructural features of the osteoclasts from Paget's disease of bone in relation to a viral aetiology

The ultrastructure of the osteocytes, osteoblasts, osteoclasts, haemopoietic and other connective tissue cells was examined in 27 biopsies from 22 patients with Paget's disease of bone. Electron microscopy showed characteristic nuclear and cytoplasmic inclusions in the osteoclasts of all of the 25 biopsies exhibiting histological evidence of Paget's disease. Such inclusions were absent from all the other types examined. The intranuclear inclusions consisted of stacked rows or complex whorls of tubular filaments with an individual filament diameter of 12-15 nm, often arranged in a paracrystalline array. The frequency of occurrence of inclusions in the osteoclasts and their individual nuclei measured quantitatively in 18 of the biopsies was related to the histological severity of the disease process. The similarity of the observed inclusions to those of paramyxovirus inclusion bodies (particularly measles) support the hypothesis that Paget's disease is a slow virus infection.

Ultrastructural study of long-term canine distemper virus infection in tissue culture cells

The morphogenesis of canine distemper virus was studied in Vero cell cultures for 43 days post-inoculation. Active replication of the virus was observed by electron microscopy and assay from 12 h after inoculation on, and peak production was observed on days 5, 14, and 22. From day 28 on, constant but smaller amounts of infectious virus were detected. Two ultrastructural types of intracytoplasmic nucleoprotein filaments were observed; although they first appeared at different times, their subsequent chronological patterns of development were similar. The cells apparently became free of virus by a mechanism of vacuolation. Intranuclear filaments were seen about day 11 and appeared to increase in number thereafter, whereas the infectious titer declined. Possible mechanisms of persistence are discussed in the light of these findings.

Diagnostic virology using electron microscopic techniques

This chapter illustrates the development of the use of electron microscopy in viral diagnosis. The field covered is confined to medical viral diagnosis, but parallel developments have taken place in both veterinary and botanical fields and techniques derived from both these sources are also included where relevant. It is reported that the scanning transmission mode of operation, which can induce image contrast changes electronically, may enhance studies with unstained sections and perhaps facilitate thin section immune electron microscopy (IEM). The application of negative stain IEM has been particularly useful for the study of the antigenic nature of some of the newly discovered noncultivable viruses. Viral antigens can also be detected in thin sections of infected cells by IEM with suitably labeled specific antibodies. Confirmation of viral infection by electron microscopy on tissues originally processed for light microscopy is also frequently useful.

Mode of subacute sclerosing panencephalitis (SSPE) virus infection in tissue culture cells. III. Neurovirulence of cell-free SSPE viruses of Niigata-1, Kitaken-1, and Biken strains

Cell-free viruses recovered from virus-carrying cultures of the Niigata-1, Kitaken-1, and Biken strains of SSPE virus were examined for neurovirulence. The cell-free viruses were prepared by freezing and thawing or by EDTA treatment of the virus-carrying cultures and inoculated into adult mice intracerebrally. A considerable number of the inoculated mice showed clinical signs about 1 to 5 weeks after the inoculation. The first symptom was hyperreactivity, which was followed by paresis and myoclonus. All of the affected mice fell in paralysis and finally died. The virus could be recovered from the moribund mice by cocultivation of the brain cells with Vero cells. Immunofluorescence staining of the brain tissue revealed that infected cells containing viral antigens were distributed sparsely. No inflammatory feature, however, was observed in the brain as far as examined and neutralizing antibody against SSPE virus was not detected in sera from the mice inoculated with the cell-free SSPE viruses.

Measles virus nucleotide sequences: detection by hybridization in situ

A tritium-labeled probe that detects measles virus nucleotide sequences was hybridized in situ to cells infected with measles virus and to sections of brain tissue from patients with subacute sclerosing panencephalitis and from patients with multiple sclerosis. The measles virus genome was detected in many cells in subacute sclerosing panencephalitis where this virus would have been missed by methods such as immunofluorescence. Measles virus sequences were also found in two foci in one of four cases of multiple sclerosis. This refined method of hybridization in situ, which can be useful in the search for covert virus infections of man, provides evidence that viruses may be involved in multiple sclerosis.

Encephalitis after inhalation of measles virus: a pathogenetic study in hamsters

A neuroadapted strain of measles virus (HNT) was administered by inhalation to newborn hamsters. Primary replication of virus in the lung was followed by the transient appearance of virus in spleen within 7 to 9 days of inoculation. A terminal encephalitis occurred between 6 and 60 days in 31% of infected hamsters, and virus was recovered by explant culture of these brains. Virus could not be cultured directly from brain or tissue homogenates. At least 7% of hamsters that had survived the infection for two months had antibody to measles virus. The histopathological change in morbid animals was limited to the central nervous system (CNS) and consisted of small foci of necrosis, perivascular mononuclear cell infiltrates, intracytoplasmic and intranuclear inclusions, and vacuolated pyknotic neurons. Immunofluorescent studies disclosed measles antigen in the lungs and brain. This hamster model of measles encephalitis following a "natural" route of inoculation appears to represent a faithful reproduction of certain CNS complications of natural measles infection in humans, i.e., measles encephalitis and subacute sclerosing panencephalitis.

Mode of subacute sclerosing panencephalitis (SSPE) virus infection in tissue culture cells. II. Cell-free viruses in cell cultures infected with Kitaken-1 and Biken strains of SSPE virus

Cell-free infectious viruses were successfully recovered by the aid of freezing and thawing from cultures infected with the Kitaken-1 and Biken strains of subacute sclerosing panencephalitis (SSPE) virus. Our results including those in a previous report which dealt with the Niigata-1 strain of SSPE virus show that cell-free viruses can be detected from all of the SSPE virus-carrying cultures established in Japan. It was also found that cell-free infectious viruses can be recovered efficiently by dispersing the virus-carrying cultures with EDTA. The inclusion of trypsin in the EDTA solution, however, caused a poor recovery of the infectious viruses. Infection of cells with the cell-free viruses readily established the virus-carrying cultures that have characteristics comparable to those of their original cultures. The culture infected with the Kitaken-1 strain produced infectious viruses in about ten times the amount of the other two infected cultures. The buoyant densities of the cell-free infectious viruses were almost the same among the three strains, the values being 1.120 to 1.132, but significantly less than that of 1.164 of measles virus. The low density can be ascribed to one of the characteristics of these SSPE viruses.

Mode of subacute sclerosing panencephalitis (SSPE) virus infection in tissue culture cells. I. Detection of infectious virions from cells infected with Niigata-1 strain of SSPE virus

By the aid of freezing and thawing, cell-free infectious virions were detected from an apparently nonproductive Vero cell line infected with Niigata-1 strain of subacute sclerosing panencephalitis virus. The production of infectious virions was limited in amount and such virions were detectable only during a limited period after cell subculture. The infectious virions were filtrable through a 0.65 mu membrane filter and neutralized completely by an antiserum against measles virus. The virions were banded at the density of 1.132, while Edmonston strain of measles virus banded at 1.164 in potassium tartrate density gradients. Infectious virions were also released from infected Vero cells by treatment of the cells in a hypotonic solution to an amount comparable to that obtained by freezing and thawing. Infection of normal culture of Vero cells with the infectious virions readily established a virus-cell interaction identical to that in the original infected culture from which the virions were recovered.

Infantile cortical measles inclusion body encephalitis during combined treatment of acute lymphoblastic leukemia

A case of cortical measles inclusion body encephalitis occuring in a boy aged 6 years 7 months, 4 months after uncomplicated measles is reported. The child was undergoing combined treatment ofr acute lymphoblastic leukemia. He was in primary remission for 2 years. The neuropathological findings are characterized by necrosis, eosinophilic nuclear and cytoplasmic inclusion bodies in the neuronal and glial cells within the cerebral cortex and basal ganglia. Nucleocapsides of paramyxoviruses were detected in the nuclear inclusion bodies of both cell types.

Isolation and characterisation of a defective measles virus from a subacute sclerosing panencephalitis patient

A cytopathic measles virus was isolated from a brain biopsy of a subacute sclerosing panencephalitis (SSPE) patient. The agent could be transferred to Vero cells by cocultivation, but the infectivity always remained cell-associated -ie, a defective virus infection. The cell-associated nature of the virus was retained through 25 passages in Vero cells. Intracerebral inoculation of hamsters (2-6 days old) with the cocultured Vero cells gave rise to 100% mortality in 5-7 days. The virus retained its cell-associated nature after passage in hamsters. Electron microscopy of the brain and Vero cocultures showed the presence of virus-like ribonucleoparticles mainly in the nucleus. The presence of viral antigens in the nucleus, cytoplasm, and on the plasma membranes was confirmed by immunofluorescence. Using a combination of immunological and biochemical techniques, it was shown that all the viral proteins were synthesized with the exception of the haemagglutinin. Inclusion of the fusion inhibitor SV4814 (CBZ-D phenylalanine-L-phenylalanine-L-arginine-NO2) in the culture medium led to the elimination of the SSPE infection.

Isolation and biological characterization of a measles virus-like agent from the brain of an autopsied case of subacute sclerosing panencephalitis (SSPE)

Isolation of a cytopathic agent causing formation of syncytial giant cells in co-cultivated Vero cells from the brain of an autopsied case of subacute sclerosing panencephalitis (SSPE) is reported. The syncytia usually autolyzed from the center after growing to 1 to 2 mm in diameter and then detached from the culture vessels, and finally made macroscopically recognizable round plaques on the monolayer under liquid overlay. The agent was identified serologically as an agent related to measles virus, by both immunofluorescent tests and plaque reduction tests using anti-measles sera. However, the infected cells did not produce either virions or hemagglutinin, and failed to show hemadsorption and hemolysis of African green monkey red cells even after the 55th passage through Vero cells. Newborn mice, adult mice and hamsters showed neurologic signs after intracerebral inoculations of the infected cells, and most of them died from acute encephalitis. Guinea pigs were unsusceptible. From the brain of the animals with neurologic signs, a similar agent to the inoculated one was recovered. The new isolate appears to be a strain closely related to measles virus on the basis of serology, and was designated as SSPE-"Kitaken-1" strain.

The effects of measles virus and various strains of SSPE virus on organotypic cultures of nervous tissue

The neurotropic effects, virologic behaviors and morphologic appearances of 4 strains of subacute sclerosing panencephalitis (SSPE) virus have been examined in organotypic cultures of hamster cerebellar tissue and have been compared with the Edmonston strain of measles virus in the same system. While measles virus caused extensive damage to nervous tissue, the SSPE strains, in general, exerted a less deleterious effect. All of the SSPE viruses replicated in this tissue. The SSPE strains showed morphologic variation ranging from normal measles-type virions to apparently nucleocapsid deficient forms. It is speculated that some of these differences between measles and SSPE virus may account for the differences in the in vivo conditions with which they are associated.

Cell-associated subacute sclerosing panencephalitis agent studied in organotypic central nervous system cultures: viral rescue attempts and morphology

Organotypic cultures of hamster cerebellum were exposed to the IP-3-Ca cell line , which contains a cell-associated subacute sclerosing panencephalitis agent. Central nervous system (CNS) cultures were examined by light and electron microscopy as well as standard virological techniques from 3 to 46 days postinfection. The results indicate that although viral nucleocapsid material was transferred to elements of the CNS, cell-free virus could not be detected by virological techniques and by electron microscopy, and budding viral particles were not observed. Attempts to recover cell-free virus from hamster CNS tissue exposed to IP-3-Ca cells were generally negative. However, 2% of the cultures yielded low levels of infectious virus. IP-3-Ca cells were able to transfer the cell-associated viral material to all cell types found in the CNS cultures and were capable of inducing polykaryocytes in the CNS cultures. The role of cell-associated virus-like agents in subacute sclerosing panencephalitis and other chronic CNS infections is discussed.

Isolation and characterization of temperature-sensitive mutants of measles virus

Nine temperature-sensitive (ts) mutants of nonattenuated Edmonston strain measles virus were isolated from wild-type virus which was grown in the presence of 5-fluorouracil. Adsorption, temperature shift, and complementation experiments indicated that all these mutants were restricted at an intracellular stage of infection. However, all the mutants were more rapidly inactivated at 41 C than was wild-type virus, suggesting that the ts product of each mutant either influences or is a structural component of the virus. Three complementation groups were found to be represented among the mutants. Group A contained one mutant and it did not induce synthesis of detectable amounts of viral antigen at the nonpermissive temperature (39 C). Group B consisted of six mutants which did not induce viral antigen synthesis at 39 C and one mutant which did. Group C was represented by one mutant and it induced viral antigen synthesis at 39 C. The two mutants which induced sythesis of viral antigen also induced synthesis of relatively small amounts of virus-specific RNA at 39 C. These mutants, while producing cytoplasmic and nuclear accumulations of viral antigen at 39 C, were restricted in production of syncytia and hemadsorption. All the mutants were less neurovirulent than wild-type virus, as indicated by their inability to produce acute disease in newborn hamsters.

Complications of keratoplasty

The complications of keratoplasty have been greatly reduced in recent years by virtue of finer instrumentation, microsurgery, new drugs to minimize postoperative complications, and improved methods of donor cornea preversation. A 49-year-old woman, following uncomplicated keratoplasty with donor material from a patient who had died of a slow virus disease, developed the same condition and died 18 months later. Until more evidence is available, donor material from individuals dying of obscure chronic central nervous system disorders should be used with extreme caution.

Human brain in tissue culture. I. Acquisition, initial processing, and establishment of brain cell cultures

This paper details the in vitro techniques used to establish cells in culture from the brains of 40 patients, most of whom had chronic neurologic disease. The clinical and pathologic features of these patients are given. The success in establihsing cell lines was dependent upon the origin of tissue (biopsy vs. autopsy), the site of removal from the brain, and various environmental and technical manipulations in vitro.

Isolation and characterization of subacute sclerosing panencephalitis virus nucleocapsids

Nucleocapsids from subacute sclerosing panencephalitis (SSPE) virus-infected CV-1 cells were concentrated by differential centrifugation employing sucrose cushion techniques and further purified by centrifugation through a linear CsCl density gradient. The bouyant density of (3)H-uridine-labeled nucleocapsids in CsCl was found to be 1.31 g/cm(3). Ultraviolet absorption spectra of the purified SSPE nucleocapsid showed an absorption maximum at 260 to 265 nm and a 280/260 ratio that corresponded to a nucleic acid content of approximately 4.3%. Negatively stained preparations of SSPE nucleocapsids were found to have a width of 18 +/- 1 nm, a periodicity of 5 to 6 nm, and a length between 1-1.4 mum, with the greatest number at 1.3 mum.

Latency of human measles virus in hamster cells

A latent system employing measles virus (Schwarz strain) was developed in hamster embryo fibroblasts (HEF). Measles virus-specific antigen was detected by immunofluorescence in 30 to 50% of HEF cells, and these cells released infectious virus when co-cultivated with a susceptible monkey cell line, BSC-1 cells. No infectious virus could be detected in the cells when measures were taken to exclude passage of viable latent cells onto the indicator BSC-1 cells. Infectious center assays demonstrated that about 1 in 10 of the latently infected cells in the population could release infectious virus. Infectious virus appeared within 6 hr after co-cultivation of the HEF cells with BSC-1 cells, as compared to 24 hr required for normal replication of measles virus in the BSC-1 cells. Furthermore, labeling of progeny virus ribonucleic acid (RNA) by using tritiated uridine, and inhibition of RNA or protein synthesis by 5-azacytidine or cycloheximide suggested that neither additional RNA nor protein synthesis is required after co-cultivation of the cells to effect early virus release. It can therefore be postulated that there is a block at a late step in virus replication in the latently infected hamster cells. The most obvious site would concern maturation of infectious virions at the cell membrane.

Virus antibody levels in systemic lupus erythematosus

Antibody titers to a group of viral antigens have been determined in sera from patients with systemic lupus erythematosus (SLE), control groups with inflammatory diseases and normals. Mean titers in SLE sera for all viruses tested were significantly greater than in four control groups, but not greater than in active tuberculosis, both by the complement‐fixation (CF) and hemagglutination‐inhibition (HI) methods. By the CF method, only measles virus showed significantly higher titers in SLE than in all control groups; by the HI method, measles antibody titers were higher in SLE than in all groups but tuberculosis. There was no correlation between antibody titers and gammaglobulin levels. The results indicated a moderate though variable overall hypereactivity in SLE to the viral antigens tested.