Slow virus diseases

Prions are responsible for the so-ealled slow virus diseases, a distinet group of unusual neurologieal disorders. They are believed to be markedly resistant to inactivation by many ehemieal and physical agents but because they have not been purified, it is at present diffieult to state whether this is an intrinsic property of prions or whether it results fkm the proteetive effect of host tissue present. Certainly very high coneentrations of a bioeide aeting for long periods may be necessary to produee inactivation. 

The prion diseases are a closely related group of neuro-degenerative conditions which affect both humans and animals. They have previously been described as the subacute spongiform encephalopathies, slow virus diseases and transmissible dementias, and include scrapie in sheep, bovine spongiform encephalopathy (BSE) in cattle, and the human prion diseases, Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker disease (GSS), fatal familial insomnia (FFI) and kuru. Prion diseases are... 

Most bacterial infections can be treated successfully with antibiotics, but the development of satisfactory antiviral agents has been slow. Yet we are susceptible to many dangerous virus diseases, and viruses also take a huge toll among domestic animals and plants.3 The first antiviral drug, 5-iodo-2 -deoxyuridine (idoxuridine), was introduced in 1962 and was used for 20 years by ophthalmologists to treat serious eye infections by the herpes simplex virus (HSV). 

Slow viruses are becoming increasingly suspect in the instances of much more common diseases, particularly the autoimmune diseases. An autoimmune disease may be defined as a disease wheiein the immune system of the body does not direct its attack on an invading foreign substance, but instead at the body s own tissue. Many authorities consider rheumatoid arthritis and multiple sclerosis as autoimmune diseases. The precise causes of these diseases have remained obscure. Multiple sclerosis is a demyelinating disease and has variously been described as an autoimmune disease, a viral disease, or an autoimmune disease provoked by a virus. Epidemiological studies indicate that from 3 to 23 years may elapse between the time of exposure to the virus and the onset of symptoms. Further evidence points to involvement of a myxovirus. Measles virus is of this kind. 

Certain scrapie-like diseases of sheep in Iceland and some chronic encephalopathies in man (including kuru, the laughing disease of New Guinea) are the result of slow virus infections with long incubation periods. 1-Methylisatin 3-thiosemicar-bazone has been found to reduce the reverse transcriptase activity and cytopathic effect of the RNA slow viruses producing the sheep diseases and hence may provide a chemotherapeutic method for their control118. ... 

Finally, there is an increasing need to evaluate the importance of environmental toxins in the pathology of Alzheimer s disease. There has been much interest lately in the role of aluminium as a causative factor, while the studies of dementia associated with the acquired immunodeficiency syndrome have focused attention on the effects of slow viruses in causing brain cell death. 

Infectious disorders Chronic meningitis Tuberculosis, fungal, parasitic HIV disease Tertiary syphilis Slow virus (Creutzfeldt-Jakob disease) Treatment of infection... 

Draganescu N, Antipa C, Girjabu E, Melencu M. Endemic Balkan nephropathy, a slow virus disease Rev. Roum. Med.-Virol. 1983 ... 

Dickinson AG (1976) Scrapie in sheep and goats. In Kimberlin RH (ed) Slow virus diseases of animals and man. North-Holland Publishing, Amsterdam, pp 209-241... 

Prions are now thought to be what were formerly called slow viruses, because the resulting diseases took months or years or decades to develop (Voet and Voet, 1995, p. 1116). These particular diseases pertain to the mammalian nervous systan. None of the diseases exhibit inflammation or fever, indicating that the immune system is neither activated nor impaired by the disease. As has been indicated, the word prion stands for proteinaceous infectious particle, and the protein itself is called PrP, for prion protein. 

Many other possible causes of dialysis dementia have been proposed. These inclnde other trace element contaminants, normal pressure hydrocephalus, slow virus infection of the central nervous system, and regional alterations in cerebral blood flow (Arieff, 1990). Slow virus infection of the nervous system is a possible etiology for dialysis dementia. The clinical manifestations resemble those of other slow virus infections, such as Kuru or Creutzfeldt-Jakob disease (Selkoe, 1978 4714 Gajdusek, 1985 1662). 

In pharmacology, two adamantane derivatives. Amantadine (1-adamanta-neamine hydrochloride) and Rimantadine (a-methyl-1-adamantane methyla-mine hydrochloride) (see Fig. 24), have been well known because of their antiviral activity [129]. The main application of these drugs is prophylaxis (treatment to prevent the onset of a particular disease) and treatment of influenza-A viral infections. They are also used in the treatment of parkinsonism and inhibition of hepatitis-C virus. Memantine (1-amino-3,5-dimethyladaman-tane) (see Fig. 24) has been reported effective in slowing the progression of Alzheimer s disease [130]. 

The limiting factor in tomato production in the tropics is more apt to be a virus disease than a fungus disease of the foliage. The control of virus disease by control of the insect vector has been investigated in Mexico on potatoes (leaf roll, purple top), tomatoes (several unidentified viruses, one of which perhaps is curly top), and corn (corn stunt). Virus control in this way has been variable but usually negligible. This lack of control perhaps is due to slow kill of the insect vector, or to the continuous entry of the vector into the field. 

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