Experimental amyotrophic leukospongiosis in guinea pigs after retrobulbar infection

The results of modelling of amyotrophic leukospongiosis, a new form of slow infection of the human central nervous system, on guinea-pigs are reported. The animals were injected retrobalbulary with the virus-containing suspension. 1.5-2.5 weeks after the injection 70% of animals revealed signs of retinopathy during ophthalmoscopy. Two months later 90% of animals died, 40% of them exhibiting manifestations of the infection. Experimental amyotrophic leukospongiosis was histologically confirmed in all the dead animals. This method of modelling made it possible to shorten the incubation period to 1.0-2.0 months, while in intracerebral and intramuscular ways of contamination it was 3.5-8.2 and 5.3-11.1 months, respectively. The results evidence the involvement of the peripheral visual analyzer in the pathogenesis of experimental leukospongiosis at the early stages of its development.     

Isolation of a nonclassical virus and a study of its etiological role in human amyotrophic leukospongiosis

The study of the brain of a patients with amyotrophic leukospongiosis and the brain of squirrel monkeys with the experimentally induced disease has resulted in the isolation of an agent which, in accordance with its physicochemical and biological properties, can be classified with unconventional viruses. The results of the experimental reproduction of the disease in laboratory animals have confirmed its etiological role in the development of the disease.     

Epidemiological research in amyotrophic leukospongiosis

The epidemiological aspects of amyotrophic leukospongiosis (AL), a slow viral infection of the central nervous system leading to the fatal outcome in 2-4 years, have been studied. As a rule, this disease is observed in the inhabitants of rural areas or in town dwellers born in rural areas and having spent there a considerable part of their life. AL occurs in persons of middle and older age; young people under 19 years and old people over 68 years of age are not affected by this infection. In contrast to amyotrophic lateral sclerosis and the Jakob-Creutzfeldt disease, AL is characteristic for persons in the phase of hormonal activity. The disease starts mostly in autumn and winter; this regularity is especially pronounced in women. The morbidity level (according to the average annual data) is at present 0.3 per million of population. An increased morbidity rate is characteristic of the family and group type of the epidemic process. This higher morbidity rate, by one order higher than that observed in the sporadic type of morbidity, is caused by the gradual formation of "genetic isolates".     

Ultrastructural changes in the axons of the central nervous system in experimental amyotrophic leukospongiosis

Ultrastructural changes, various by their character and the degree of expression, have been found in axons of the spinal cord of guinea-pigs with amyotrophic leukospongiosis (AL) (a slow infection of the CNS). The dependence of the degree of degenerative changes on the disease duration is shown. Absorption of cellular debris by oligodendrocytes and astrocytes is noted. It seems that microglia does not participate in phagocytosis. The conclusion has been made that experimental AL is a convenient model for studying the mechanisms of death of the central axons and analysis of the glia cell function under the conditions of keeping the blood-brain barrier intact.     

The molecular basis of herpes simplex virus pathogenicity

The key features of herpes simplex viruses are cell destruction with considerable pathology, particularly in productive infections of the central nervous system, and ability to remain latent in sensory and autonomic neurons of the peripheral nervous system. In cells in culture, approximately half of the 74 known different genes of the virus are not essential for viral replication. For the most part, these genes are required for efficient viral replication in experimental animal models. Mutations in a small number of viral genes have been shown to decrease the ability of the virus to access the central nervous system or in ability to multiply efficiently. These genes play a key role in defining the pathogenic properties of the virus. Current evidence suggests that viral gene expression is not required for initiation and maintenance of the latent state. Latency reflects the capacity of the cell to specifically and transiently repress viral gene expression.     

Western equine encephalitis in infants; a report on three cases with sequelae

Approximately one-third of the laboratory-confirmed cases of Western equine encephalitis occur in children under the age of 10. The present paper describes three instances of Western equine encephalomyelitis virus infection in infants under one year of age, together with the resultant sequelae. The difficulties associated with diagnosis of central nervous system disturbances in very young children are discussed, and it is pointed out that in view of the frequent occurrence of clinical infections with the arthropod-borne encephalitis viruses these agents should be given serious consideration as a cause of acute central nervous system infection in childhood and as the possible etiology for obscure, severe neurological disturbances in the pediatric age groups.     

WESTERN EQUINE ENCEPHALITIS IN INFANTS—A Report on Three Cases with Sequelae

Approximately one-third of the laboratory-confirmed cases of Western equine encephalitis occur in children under the age of 10. The present paper describes three instances of Western equine encephalomyelitis virus infection in infants under one year of age, together with the resultant sequelae. The difficulties associated with diagnosis of central nervous system disturbances in very young children are discussed, and it is pointed out that in view of the frequent occurrence of clinical infections with the arthropod-borne encephalitis viruses these agents should be given serious consideration as a cause of acute central nervous system infection in childhood and as the possible etiology for obscure, severe neurological disturbances in the pediatric age groups.     

Modification of a method to study cell fusion induced in vitro by viruses]

A studying method of viruses induced cell-fusion is described, using monolayers of Vero monkey cells. Nature and density of cells and infection multiplicity are studied. The sensibility is equal to 4 hemagglutining units of Senda? and accuracy about +/- 3 % of polykaryocytosis. Quantification. comparison and kinetics study of cell-fusion are allowed by this method which may lead to systematic and routine exploration of cell-fusion ability of biological extracts from slow degenerative diseases of the human central nervous system.     

Listeria monocytogenes: epidemiology, human disease, and mechanisms of brain invasion

Listeria monocytogenes is a facultative intracellular bacterium that has predilection for causing central nervous systemic infections in humans and domesticated animals. This pathogen can be found worldwide in the food supply and most L. monocytogenes infections are acquired through ingestion of contaminated food. The main clinical syndromes caused by L. monocytogenes include febrile gastroenteritis, perinatal infection, and systemic infections marked by central nervous system infections with or without bacteremia. Experimental infection of mice has been used for over 50 years as a model system to study the pathogenesis of this organism including the mechanisms by which it invades the brain. Data from this model indicate that a specific subset of monocytes, distinguished in part by high expression of the Ly-6C antigen, become parasitized in the bone marrow and have a key role in transporting intracellular bacteria across the blood-brain barriers and into the central nervous system. This Minireview will summarize recent epidemiologic and clinical information regarding L. monocytogenes as a human pathogen and will discuss current in vitro and in vivo data relevant to the role of parasitized monocytes and the pathogenetic mechanisms that underlie its formidable ability to invade the central nervous system.     

Biochemical and immunological changes in guinea pigs with experimentally reproduced amyotrophic leukospongiosis

Biochemical blood serum tests at different stages of amyotrophic leukospongiosis have shown differences in lactate and pyruvate levels as well as in lactate dehydrogenase activity, indicative of the increased oxidative exchange in sick guinea-pigs. It is suggested that intensified glycolysis is a compensatory-adaptive reaction in response to hypoxia due to respiratory disorders (spinal type) and degeneration and death of motoneurons. Leukospongiosis was accompanied by the decline in the complement level in the blood serum and production of antibodies to nervous fiber proteins.     

Content of phospholipid, cerebroside and cerebroside sulfate in the central nervous system of mice with acute experimental viral demyelination

A study was made of the content of phospholipids, cerebrosides and cerebroside sulfates in the central nervous system of mice with experimental acute viral encephalomyelitis. No considerable changes in phospholipid content were revealed. A significant drop in the content of cerebrosides and cerebroside sulfates was defected in the CNS, being more pronounced in the spinal cord of sick animals. The reduction in the content of glycolipids can be explained by myelin disintegration and by the effect of viruses on the olygodendrocytes in which cerebrosides and cerebroside sulfates are synthesized.     

Illuminating viral infections in the nervous system

Viral infections are a major cause of human disease. Although most viruses replicate in peripheral tissues, some have developed unique strategies to move into the nervous system, where they establish acute or persistent infections. Viral infections in the central nervous system (CNS) can alter homeostasis, induce neurological dysfunction and result in serious, potentially life-threatening inflammatory diseases. This Review focuses on the strategies used by neurotropic viruses to cross the barrier systems of the CNS and on how the immune system detects and responds to viral infections in the CNS. A special emphasis is placed on immune surveillance of persistent and latent viral infections and on recent insights gained from imaging both protective and pathogenic antiviral immune responses.     

Study of the effects of amyotrophic leukospongiosis causative agent on neuroglia cells in vitro

The influence of amyotrophic leukospongiosis (AL) causative agent on the ultrastructure of different types of cells of dissociated rat embryo brain and spinal cord cultures was studied. The AL agent belongs to the unconventional viruses (prions) and causes degenerative changes in the CNS. Large neurons and fibrous astrocytes were shown to be most sensitive. It was noted that the time of development and the degree of the dystrophic changes depend on the agent concentration. The destruction of cell membranes resulted in the pair neuron confluence. The formation of giant mitochondria with intramitochondrial inclusions was detected. It is supposed that the energetic apparatus of sensitive cells is primarily damaged by the infectious agent.     

Increased stem cell proliferation in the spinal cord of adult amyotrophic lateral sclerosis transgenic mice

Harnessing the regenerative potential of the central nervous system to repopulate depleted cellular populations from endogenous stem cells would be a novel approach for the treatment of neurological diseases resulting from cell death. Consequently, understanding if and how the central nervous system is capable of such regeneration would determine if such an approach is feasible. In this report, we provide evidence of widespread regenerative response in the spinal cord of amyotrophic lateral sclerosis transgenic mice. However, this regenerative response appears to be largely unproductive. We demonstrate that there is significantly increased gliogenesis, but an absence of convincing neurogenesis. The fact that the neurodegenerative process stimulates a regenerative response suggests that the adult spinal cord has at least limited ability for regeneration. Further studies will determine if this endogenous regenerative process can be enhanced and directed so as to slow or even reverse the natural progression of this devastating disease.     

A method of detecting demyelinated nerve tissue in experimental allergic encephalomyelitis

A method of rapid pathomorphological diagnosis of demyelinization with a simultaneous detection of cell elements in the nervous tissue has been described. The method tested on the model of experimental allergic encephalomyelitis (EAE) is a modified method of Marchi with subsequent staining of histological sections with toluidine blue. Due to a shorter period of nervous tissue exposure to potassium bichromate and osmium acid solutions (from 6-8 weeks to 5 days) the cells preserve their ability to uptake the dye and the endurance of histological sections increases. Their thickness (2-3 microns) makes it possible to examine them in immersion magnification of the light microscope. Using the above method, we succeeded in revealing hematogenic and glial elements in demyelinating foci in the central nervous system of animals with EAE. The method described can be used for studying pathomorphology of multiple sclerosis and other demyelinating diseases in humans and their experimental models, as well as for the express diagnosis of demyelinization in pathoanatomical practice.     

Harnessing endogenous miRNAs to control virus tissue tropism as a strategy for developing attenuated virus vaccines

Live attenuated vaccines remain the safest, most cost-effective intervention against viral infections. Because live vaccine strains are generated empirically and the basis for attenuation is usually ill defined, many important viruses lack an efficient live vaccine. Here, we present a general strategy for the rational design of safe and effective live vaccines that harnesses the microRNA-based gene-silencing machinery to control viral replication. Using poliovirus as a model, we demonstrate that insertion of small miRNA homology sequences into a viral genome can restrict its tissue tropism, thereby preventing pathogenicity and yielding an attenuated viral strain. Poliovirus strains engineered to become targets of neuronal-specific miRNAs lost their ability to replicate in the central nervous system, leading to significant attenuation of neurovirulence in infected animals. Importantly, these viruses retained the ability to replicate in nonneuronal tissues. As a result, these engineered miRNA-regulated viruses elicited strong protective immunity in mice without producing disease.     

Analysis of the antigenic and immunogenic properties of protein M of the influenza virus by an immunoenzyme method

A test system permitting the detection of influenza virus protein M at a concentration of 0.1-0.5 ng/ml in ELISA has been developed. The use of this system made it possible to detect influenza viruses A and B directly in crude virus-containing material and clinical samples obtained from influenza patients. During the outbreak of influenza in the spring of 1983 ELISA was successfully used for the rapid diagnosis of influenza, and some of its advantages in comparison with the conventional immunofluorescence test were thus demonstrated. To overcome difficulties arising from the low immunogenic potency of protein M, in the process of obtaining diagnostic sera and ascitic fluids the animals were immunized with the conjugate of protein M and polyelectrolite, which ensured considerable activation of humoral immune response.     

Seminars in Virology: A Biological Perspective of Slow Virus Infection and Chronic Disease

Sequential events characterize the interaction of viruses with parenchymal cells, and acute lytic infections of tissues and organs have broad biological attributes. A knowledge of these permits a keener understanding of persistent, intermittent herpesvirus infections and persistent, continuous respiratory virus infections. In addition to unique biochemical mechanisms which may permit the latter chronic infections to evolve, the roles of defective and mutant strains of virus, viral interference, and the genetic, developmental and immunological expressions of the host are of considerable and provocative importance.The traditional view of viral infections embraces a broad spectrum of acute pathological and inflammatory events. The relationship of measles virus to subacute sclerosing panencephalitis, the elucidation of the latency of herpes simplex virus, and the slow unmasking of the pathogenesis of multiple sclerosis have illustrated the subtle elements of persistent viral infections of the human being. These chronic neurological diseases have provided the opportunity and stimulus for sharp dissection of the biological and biochemical processes which embellish the logical link of viral infections to other forms of chronic human illness.     

Epidemiology of Leptospirosis in California: A Cause of Aseptic Meningitis

Twenty-one cases of leptospirosis, including three that were fatal, were reported in California during 1961-1965. An additional 18 cases were detected for the same period by screening sera from patients with central nervous system (CNS) disease of suspected viral origin. This finding supports a hypothesis that leptospirosis frequently is not considered in the differential diagnosis of CNS disease in which viral infection is suspected.The 39 patients, six of them females, ranged in age from six to 66 years. Most infections occurred in the summer. A history of exposure to animals or of swimming in potentially contaminated waters was obtained from 32 of the 39.     

Therapeutic gene silencing delivered by a chemically modified small interfering RNA against mutant SOD1 slows amyotrophic lateral sclerosis progression

Inherited neurodegenerative diseases, such as Huntington disease and subset of Alzheimer disease, Parkinson disease, and amyotrophic lateral sclerosis, are caused by the mutant genes that have gained undefined properties that harm cells in the nervous system, causing neurodegeneration and clinical phenotypes. Lowering the mutant gene expression is predicted to slow the disease progression and produce clinical benefit. Administration of small interfering RNA (siRNA) can silence specific genes. However, long term delivery of siRNA to silence the mutant genes, a requirement for treatment of these chronic central nervous system (CNS) diseases, remains a critical unsolved issue. Here we designed and tested a chemically stabilized siRNA against human Cu,Zn-superoxide dismutase (SOD1) in a mouse model for amyotrophic lateral sclerosis. We show that the modified siRNA has enhanced stability and retains siRNA activity. Administration of this siRNA at the disease onset by long term infusion into the CNS resulted in widespread distribution of this siRNA, knocked down the mutant SOD1 expression, slowed the disease progression, and extended the survival. These results bring RNA interference therapy one step closer to its clinical application for treatment of chronic, devastating, and fatal CNS disorders.