The "modified host protein" model of scrapie proposes that the transmissible agent is composed of the degradation-resistant protein, Sp33-37, and that clinical and pathologic signs result from neurotoxic accumulations of this protein. Sp33-37 is an abnormal, amyloidogenic isoform of the normally occurring cellular protein Cp33-37. This study investigated the tissue distribution of Cp33-37 in hamster. In brain, Cp33-37 was most concentrated in the hippocampal formation. Immunohistochemical studies localized Cp33-37 to neurons and surrounding neuropil in hippocampus; septal, caudate, and thalamic nuclei; dorsal root ganglia cells; and large-diameter dorsal root axons. In non-neuronal hamster tissues, Cp33-37 was detected in circulating leukocytes, heart, skeletal muscle, lung, intestinal tract, spleen, testis, ovary, and some other organs. The presence of Cp33-37 in extracerebral tissues indicates that its function is not unique to brain. These results indicate that the molecular substrate for the production of Sp33-37, the scrapie agent, and scrapie amyloid is present in a variety of cerebral and extracerebral sites.

Lipids in fresh human milk do not inactivate viruses but become antiviral after storage of the milk for a few days at 4 or 23°C. The appearance of antiviral activity depends on active milk lipases and correlates with the release of free fatty acids in the milk. A number of fatty acids which are normal components of milk lipids were tested against enveloped viruses, i.e., vesicular stomatitis virus, herpes simplex virus, and visna virus, and against a nonenveloped virus, poliovirus. Short-chain and long-chain saturated fatty acids had no or a very small antiviral effect at the highest concentrations tested. Medium-chain saturated and long-chain unsaturated fatty acids, on the other hand, were all highly active against the enveloped viruses, although the fatty acid concentration required for maximum viral inactivation varied by as much as 20-fold. Monoglycerides of these fatty acids were also highly antiviral, in some instances at a concentration 10 times lower than that of the free fatty acids. None

Human milk was found to become antiviral during storage at 4 degrees C because of the release of fatty acids by lipolysis. The stored milk caused more than a 10,000-fold inactivation of visna virus during incubation at 37 degrees C for 30 minutes. Medium-chain saturated and long-chain unsaturated fatty acids inactivated visna virus and other enveloped viruses causing more than a 3000-fold to 10,000-fold reduction in virus titer. 1-Monoglycerides and ethers of medium-chain fatty acids were more antiviral than the corresponding free fatty acids. Antiviral fatty acids were found to affect the viral envelope, causing leakage and, at higher concentrations, a complete disintegration of the envelope and the viral particles. Lipids commonly found in natural products could possibly be used as antiviral agents against enveloped viruses.

PrP 27-30, a unique protease-resistant protein associated with scrapie infectivity, derives from the proteolytic cleavage of a larger precursor encoded by a host gene. To identify sites of PrP biosynthesis, in situ hybridization was done using cloned PrP cDNA as a probe. In rodent brain, PrP mRNA was expressed in neurons, ependymal cells, choroid plexus epithelium, astrocytes, pericytes, endothelial cells and meninges of both scrapie-infected and uninfected animals. PrP mRNA was also detected in vitro in isolated brain microglia cells. Pulmonary cells and heart muscle cells contained high levels of this mRNA. Hybridization was not detected in spleen, confirming earlier RNA blot experiments indicating extremely low levels of PrP mRNA in this tissue. Results indicate that PrP mRNA is a normal component in a variety of non-neuronal tissues and may explain the origin of the amyloid plaques present in the subependymal region of scrapie-infected brain.

No abstract

A strain of measles virus isolated in this laboratory from the brain of a patient with subacute sclerosing panencephalitis (SSPE) 1 (1) has remained cell-associated and nonproductive despite attempts to induce release of free virus from infected syncytia by cocultivation and serial passage in susceptible cell lines. This virus, designated strain D.R., has been found to be highly encephalitogenic in young adult ferrets when live or freeze-thawed syncytia on ferret cells are inoculated by the intracerebral (IC) route (1, 2). On the other hand, preliminary experiments in our laboratory indicated that wild-type (wt) measles virus, strain Edmonston, grown in monkey kidney cells was not virulent in adult ferrets. This raised the question of whether or not neurovirulence in adult ferrets is a characteristic of SSPE measles virus strains. To answer this question we grew a number of wt and SSPE strains of measles virus in Vero cell cultures and compared their neurovirulence in ferrets under identical conditions. We found that SSPE strains Mantooth, Halle, and LEC-S were like the wt strains Edmonston and Woodfolk in that they did not cause a detectable central nervous system infection in the animals, but elicited a strong serum antibody response. SSPE strains Biken, IP-3, LEC, and D.R. on the other hand, were clearly neurovirulent, although to a varying extent. In an attempt to determine whether the differences in neurovirulence of the various measles virus strains could be correlated with differences in their biological properties in cell culture, we compared a number of viral characteristics, such as cytopathic effect (CPE), virus production, and uhrastructural changes in Vero cells and in low passage monolayer cultures of ferret and human brain cells. Materials and MethodsCell Cultures and Media. Vero cells, a continuous line of African green monkey kidney cells (Flow Laboratories, Rockville, Md.) were grown in Eagle's basal medium (BME) supplemented with 10% inactivated fetal calf serum (FCS, Grand Island Biological Co., Grand Island, N. Y.), and maintained in BME with 2% FCS. Brain cultures from ferrets were prepared as previously described (1, 2). In brief, finely minced brain tissue was trypsinized and the dispersed cells washed and resuspended in growth medium consisting of BME with 20% FCS. The ferret brain (FB) cultures, in 250-ml plastic flasks (BioQuest, BBL & Falcon Products, Cockeysville, Md.), were changed at intervals until confluent cell layers had formed, and then subcuhured by trypsinization. Human brain (HB) culture was obtained from a brain biopsy extracted for diagnostic purposes from the temporal lobe of a 12-yr old child. It was found to be free of any viral CPE. The original explant cultures were subcuhured by trypsinization. The culture medium was BME with 20% inactivated FCS. The maintenance medium was BME with 2% FCS. Both FB and HB cultures were used after two to five passages by trypsinization. Both I Abbreviations used in this paper:

Subacute sclerosing panencephalitis, a rare, progressive, fatal central nervous system disease of children, is caused by measles virus. Clinical signs occur months to several years after recovery from acute measles infection. It is not known where the virus persists while the disease is inapparent. Involvement of organs outside the central nervous system has rarely been documented. To search for possible peripheral reservoirs of measles virus we used in situ hybridization to probe for measles virus RNA and immunocytochemical studies to localize measles virus antigens ina variety of organs taken at autopsy from confirmed cases of subacute sclerosing panencephalitis. Seven of 9 cadavers were found to contain measles virus RNA or antigens, or both, in at least one location outside the central nervous system. These sites included lymphoid organs such as thymus, spleen, lymph nodes, and tonsil, suggesting a role for lymphocytes in disease pathogenesis. Virus was also detected in kidney, lung, and glandular tissues such as pancreas, adrenal, and pituitary. These reservoirs may provide the antigenic stimulus leading to the elevated response characteristic for subacute sclerosing panencephalitis.

Measles virus grown in Vero cell cultures was examined at the ultrastructural level after immunoperoxidase staining with antiserum against the matrix protein. The antiserum clearly preferentially labeled the fuzzy material surrounding cytoplasmic nucleocapsids, but not the nucleocapsids themselves.