Pathogenesis of subacute spongiform encephalopathies

The subacute spongiform encephalopathies include scrapie of sheep, transmissible mink encephalopathy, and kuru and Creutzfeldt-Jakob disease of man. These diseases are caused by filterable infectious agents with unique physical properties. The usual sources of infection in nature are not completely known. Epidemiological evidence suggests that the agents may enter the body through breaks in the skin and mucous membranes. Experimental studies of scrapie after subcutaneous inoculation demonstrated early replication of the agent in lymphoid tissues and later appearance in other organs; as the amount of agent in the central nervous system (CNS) increased, it decreased in or disappeared from lymphoid tissues. In preliminary studies of kuru and Creutzfeldt-Jakob disease, the infectious agents were regularly recovered from the brains of clinically-ill patients and experimental animals but only occasionally from organs outside the CNS. It remains to be seen if early events in the pathogenesis of the two human diseases, before the appearance of clinical signs, are similar to those in scrapie.

Experimental kuru in the gibbon and sooty mangabey and Creutzfeldt-Jakob disease in the pigtailed macaque. With a summary of the host range of the subacute spongiform virus encephalopathies

The experimental host range for the slow virus infections causing subacute spongiform virus encephalopathies is enlarged in primates to include the gibbon for kuru, the pigtailed macaque for Creutzfeldt-Jakob disease, and the sooty mangabey for both diseases. The report is based on neuropathological evidence of the diseases in animals with preclinical lesions. A table lists all the species to which the subacute spongiform virus encephalopathies have been transmitted.

Experimental kuru in the spider monkey. Histopathological and ultrastructural studies of the brain during early stages of incubation

The brains of 10 spider monkeys inoculated intracerebrally with brain suspension from kuru patients have been studied histologically and ultrastructurally. The animals were killed by perfusion of fixative from four to forty-one weeks after inoculation, when healthy and free of neurological signs. Definite histopathological changes had occurred as early as four weeks after inoculation, when moderate numbers of bi-nucleated neurons were found within the limbic cortex, striatum, the hypothalamus and amongst the Purkinje cells of the cerebellum. At later stages of incubation a moderate loss of neurons in the cerebral and cerebellar cortex and a mild to moderate proliferation of fibrous astrocytes here and also in the hypothalamus were the most striking features. None of our cases showed either status spongiosus or the generalized astrocytic proliferation and hypertrophy, characteristic of fully developed experimental kuru, in any region of the brain. The principal ultrastructural abnormalities consisted of the formation of membrane-bound intracytoplasmic vacuoles, predominantly within dendrites, and of concentric laminar arrays derived from the endoplasmic reticulum. The former were seen in all regions of the brain examined and at all stages of incubation. Concentric laminar arrays were confined to the cerebellar nodulus, where they were most numerous in dendrites and neuronal perikarya four weeks after inoculation. Both changes are interpreted as an indication that the kuru agent acts upon the plasma membrane from an early stage onwards and, by stimulating its growth, leads to the formation of complex, membrane-bounded vacuoles and to hyperplasia of the endoplasmic reticulum. The formation of vacuoles is further regarded as the first sign of status spongiosus on an ultrastructural level. Attention is drawn to the great similarities between the changes observed in the present material and those described in the brains of patients dying from kuru and of primates with fully developed experimental kuru. The significance of the relatively rapid spread of the kuru agent throughout the brain is discussed in relation to the concept of "slow virus" diseases.

A modified polyriboinosinic-polyribocytidylic acid complex that induces interferon in primates

A comlex of polyriboinosinic-polyribocytidylic acid (poly I-poly C) with poly-L-lysine and carboxymethylcellulose has been prepared. This complex is five to 10 times as resistant to hydrolysis by primate serum as the parent poly I-poly C. It has a thermal denaturation temperature about 40 C higher than that of poly I-poly C. The complex induces significant levels of serum interferon in monkeys and chimpanzees under conditions in which poly I-poly C itself induces no interferon.

The foamy viruses

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Transmission of Creutzfeldt-Jakob disease to the stumptail macaque (Macaca arctoides)

The successful transmission of Creutzfeldt-Jakob disease from both affected human and chimpanzee brain to stumptail macaques has been accomplished. The incubation period of 5 yr was the same for both animals; however, the course of the disease was longer in the animal receiving the human brain. In both cases, initial mild symptoms slowly remitted only to reappear some 4 mo later. Muscle biopsies revealed changes suggestive of a mild neuropathy. In addition, there appeared to be an increased ability to incorporate 3H-thymidine in untreated cultures of lymphocytes from peripheral blood.

Transmission of Creutzfeldt-Jakob disease to the patas monkey (Erythrocebus patas) with cytopathological changes in in vitro cultivated brain cells

The transmission of Creutzfeldt-Jakob disease (CJD) to the patas monkey, Erythrocebus patas, has been accomplished. Clinical neurological disease was first noticed 47 months and 23 days after intracerebral inoculation of infected squirrel monkey brain. The disease progressed slowly and lasted 8 months. Microscopic examination of the brain and spinal cord revealed lesions of status spongiosus and astrogliosis in the cortical gray matter consistent with a diagnosis of experimental CJD. A vacuolating 'spongiform' cytopathological effect was seen in many of the in vitro cultivated brain cells in the outgrowth from explanted brain tissue of this monkey.

The progression and evaluation of hetatologic and serum biochemical values in the chimpanzee

Summary statistics of various hematologic and serum biochemical measures are presented for a colony of 74 chimpanzees (Pan troglodytes). Covariance analysis of longitudinal values revealed a progression of some measures with maturity. Equations for evaluating these measures as they relate to the health of individual colony members and new additions to the colony were formulated. From these equations, confidence bounds (95%), which can be regarded as normative ranges, were established for each of the measures. The literature on hematologic and serum biochemical values in the chimpanzee, especially as they pertain to the evaluation and progression of values, is reviewed.

Precautions in conducting biopsies and autopsies on patients with presenile dementia. Technical note

✓Precautions are recommended for operating room and autopsy room procedures involving patients with presenile dementia. These patients may have Creutzfeldt-Jakob disease, a transmissible disease caused by a virus likely to be extremely resistant to inactivation.

Isolation of a new simian foamy virus from a spider monkey brain culture

A syncytium-forming (foamy) virus was isolated from a spider monkey brain cell culture. Cytopathic effect was observed both in the brain culture and in human embryonic kidney cells. Neutralizing antibody was present in the sera of the spider monkey from whom the isolation was made. The virus was inhibited by 5-bromo-2-deoxyuridine (20 mug/ml), contained a ribonucleic acid-dependent deoxyribonucleic acid polymerase, and had an infectivity peak at 1.15 g/cm(3) in a sucrose density gradient. The virus passed through a 220-nm but not a 100-nm membrane filter, was chloroform sensitive, and was inactivated at 56 C in 30 min. Hemagglutinating and hemadsorption activity was not noted with a variety of erythrocytes. The virion was spherical, formed in the cytoplasm, and was 105 to 115 nm in diameter. Ring-shaped nucleoids, 45 to 50 nm in diameter, were associated with tubular profiles. The virus was not neutralized by sera prepared against known viruses, including simian foamy virus types 1 through 7, Mason-Pfizer monkey virus, and bovine syncytial and measles viruses. Sera from a rabbit hyperimmunized with the isolate and sera from 19 spider monkeys had neutralizing antibody to the isolate; however, these sera did not cross-react with simian foamy virus types 1 through 7. Neutralizing antibody to the isolate was not detected in sera from 16 humans, 9 rhesus monkeys, and 10 chimpanzees.

Experimental subacute spongiform virus encephalopathies in primates and other laboratory animals

The host range of subacute spongiform virus encephalopathies is described. The asymptomatic incubation period and the duration of the illnesses in various species of animal hosts is discussed along with information on additional species of Old World and New World monkeys and the domestic cat, which have been shown to be susceptible to subacute spongiform virus encephalopathies.