Isolation and characterization of subacute sclerosing panencephalitis virus nucleocapsids

A protocol for the gentle purification of virus-like particles produced in plants

The purpose of the protocol is to extract and purify virus-like particles (VLPs) that have been produced in plants. More specifically, this method is well suited to the purification of chimaeric and genetically modified VLPs that do not have native surface properties. This will be the case for VLPs used in antigen display experiments. Such particles are often more fragile than their wild-type infectious virus counterparts, and as such can be damaged or lost during procedures that involve pelleting or precipitating the particles. The method presented here is based on ultracentrifugation and density gradients, with no pelleting or precipitation step. It makes virtually no assumptions about the yield of recombinant VLPs or their properties, which means that this protocol is ideally suited to screening new constructs which are expected to lead to the formation of VLPs. This protocol will allow the researcher to determine whether the construct does indeed form VLPs, and if it does, will reduce the likelihood of those particles being lost or damaged during the purification process. Because of its non-specific nature, this protocol may also be suited to the purification of viruses of unknown nature from leaf material where an infection is suspected.

Rapid isolation of morbillivirus nucleocapsid for genomic RNA cDNA cloning and the production of specific core protein antisera

A procedure is described for the rapid isolation of canine distemper virus nucleocapsid, free from contaminating viral non-core and host cellular proteins. Nucleocapsid isolated in this manner is amenable to ultrastructural evaluation, protein isolation for the production of monospecific hyperimmune serum, and genomic RNA isolation for cDNA cloning. Nucleocapsid (NC) and a defective NC variant (Df-NC) isolated from 5.5 x 10(7) Vero cells infected with Ond-CDV is readily visualized on cesium gradients. The calculated density for NC is 1.2976 +/- 0.0033 g/ml and 1.2458 +/- 0.0056 g/ml for Df-NC. Ultrastructurally, NC appears as long uninterrupted strands, 1.6 +/- 0.1 microns in length, 21.2 +/- 1.7 nm in diameter, with well defined capsid subunits. Df-NC are truncated with a uniform length of 85.8 +/- 7.1 nm and a 24.5 +/- 1.3 nm diameter. A total of 2.1 +/- 0.2 mu of NC protein is obtained for every 1 x 10(6) cells infected; 89.7% of this mass is represented by a 61 kDa protein (N), 8.4% by a 75 kDa protein (P), and 1.9% by a 160-200 kDa protein (L), which is in agreement with the NC constituency of other paramyxoviruses. Viral N and P proteins, purified by 7.5% SDS-PAGE, were used in the production of hyperimmune serum. Specificity was demonstrated by Western blot analysis. Both antisera were capable of detecting viral antigen in persistently and lytically CDV infected cells by indirect immunofluorescence. A single high molecular weight species of nucleic acid was isolated from purified nucleocapsids compatible with a 14.6 kb morbillivirus genome. Although the efficiency of RNA extraction from purified NC was low (14.2%), sufficient RNA was obtained for gel analysis and the establishment of genomic RNA cDNA clones.

A rapid method for the purification of cytoplasmic paramyxoviral nucleocapsids

A rapid method for the purification of cytoplasmic paramyxoviral nucleocapsids using a tabletop ultracentrifuge is described. The method yields materials equivalent in purity to materials purified by previously published procedures but requires only a fraction of the time (65 min vs 7-41.5 h). When used in conjunction with modern hypersensitive analytical techniques, the procedure provides equivalent or greater amounts of nucleocapsid for subsequent analysis or study.

Measles virus and its associated diseases

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Slow virus infections

Slow viruses produce diseases whose incubation periods range from several months to many years. Because of this long latency period, the lack of inflammation produced by these diseases and the lack of recoverable virus particles, it is only recently that the association has been made between the viruses and the diseases they cause. The detailed study of kuru, a neurologic affliction of a remote tribe of cannibals in New Guinea, was responsible for the synthesis of new and previously gathered information into a unified framework to explain not only kuru but other diseases as well. Since then, animal models, transmission experiments and histologic and biochemical studies have unveiled new links connecting viruses to previously obscure neurologic, neurophthalmic and ophthalmic entities.

Persistent infection of tissue culture cells by RNA viruses

In this paper, the characteristics of cultured cells persistently infected with RNA viruses, other than leuko viruses are described. The roles that the host cell, interferon, virus mutants and defective interfering particles may play in the establishment and maintenance of persistent infection are discussed. It is proposed that the interaction of viruses with certain types of host cells can lead to persistent infection. The differences in virus-host interactions may be attributable to differences in membrane properties of various cells. Defective interfering particles may play a role in the establishment of persistent infections in cells which normally undergo lytic virus development. Mutant types of virus appear to be prominent in the virus released from persistently infected cells, but the role that various mutants play in the maintenance of persistent infections remains unclear.

Cytology of rheumatoid synovial cells in culture. III. Significance of isolates of epithelial cell lines

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Characterization of virus-specific RNAs from subacute sclerosing panencephalitis virus-infected CV-1 cells

CV-1 cells infected with subacute sclerosing panencephalitis (SSPE) virus incorporated uridine-(3)H into at least four virus-specific RNA components in the presence of actinomycin D. The component sedimenting fastest had a sedimentation coefficient of 50s corresponding to a molecular weight of 6 x 10(6). The other three RNA components have sedimentation constants of 35s, 22s, and 18s corresponding to molecular weights of 2.5 x 10(6), 1.0 x 10(6), and 0.75 x 10(6), respectively. The base composition of the 50s RNA is distinct from that of cellular RNA and comparable with base compositions of viral RNAs of other paramyxoviruses. The base composition of the 18s RNA shows approximate complementarity with the 50s RNA. RNA-RNA annealing experiments using unlabeled 50s SSPE RNA with labeled 18s RNA from cells infected with SSPE virus or measles virus show 100% annealing with 18s SSPE RNA but only 60% annealing with 18s measles RNA. These experiments suggest some differences between the 18s RNAs of SSPE virus-infected cells and measles virus-infected cells.

Immunoperoxidase stain of measles antigen in tissue culture

A specific electron microscopy staining technique for measles antigen has been developed by using Vero cells infected with a subacute sclerosing panencephalitis (SSPE) measles virus strain and fixed in glutaraldehyde or formaldehyde. Peroxidase-labeled antibody was prepared according to the method of Avrameas (4). Sera from SSPE patients with high measles antibody titer as well as normal human sera with and without measles antibody were used. With both fixatives, specific labeling was obtained on the surface of infected cells, on the budding site, and on complete viral particles. The cell membrane staining sometimes had a patchy distribution in that the reaction was most intense on the surface projections in front of each nucleocapsid. This suggests modification of the cell membrane in association with the nucleocapsids. In contrast, no label was detected on the membranes of the cells during the latent period from penetration through maturation of the virus. In formaldehyde-fixed cultures, cytoplasmic inclusions were stained, and this label was located on the "fuzzy" material around the nucleocapsids. The smooth type of nucleocapsids, mainly seen in the nucleus, were never labeled. These findings suggest that the antigenic nature of the "fuzzy" nucleocapsids in the cytoplasm may be different from that of the "smooth" nucleocapsids. The immunoperoxidase method gives good resolution of viral antigenic sites at high magnifications under electron microscopy and may be of value in studies on the immunopathogenesis of SSPE and other chronic viral infections.