Antigenic variation among parainfluenza type 1 (Sendai) viruses: analysis of 6/94 virus

Monoclonal antibodies identify a strain-specific epitope on the HN glycoprotein of Newcastle disease virus strain Australia-Victoria

A panel of monoclonal antibodies raised against the hemagglutinin-neuraminidase glycoprotein (HN) of the Australia-Victoria strain of Newcastle disease virus has been used to compare that strain and eight other strains of the virus. The ability of the antibodies to neutralize infectivity, inhibit hemagglutination and neuraminidase, and bind to purified virions in solid-phase radioimmunoassays was determined for each strain. Of the four antigenic sites delineated by these antibodies on the HN of the homologous strain, site 1 (that with the greatest neutralizing susceptibility), is apparently conserved in all the strains tested as revealed by neutralization assays. The least neutralizing site, number 4, is also conserved in most of the strains tested. Site 2, which lies at or near the neuraminidase site, appears to be conserved in the avirulent strains but not in the virulent strains. An antibody to site 3 is unable to bind to a significant extent to any of the heterologous strains tested, and thus recognizes a strain-specific epitope. Inhibition of hemagglutination and neuraminidase by antibodies to each site were also examined and the results suggest that antibodies to sites 1 and 2 may distinguish virulent and avirulent strains at least with respect to these functions.

Pathological alterations of ependyma and choroid plexus after experimental cerebral infection of mice with Sendai virus

The effects of intracerebral inoculation of Sendai virus into young adult mice were investigated by immunofluorescence, light, and electron microscopy. Immunofluorescence of virus-specific antigens was maximal on the third day after inoculation, revealing infection of leptomeninges, ependyma, and choroid plexus. Histologically, meningitis, ependymitis, and choroiditis occurred between the second and third days. The choroiditis was associated with formation of vacuoles within the cytoplasm of epithelial cells. The vacuoles reached diameters up to 50 micrometer. The ubiquitous vacuolization of plexus epithelia resulted in a honeycomb-like pattern. Opaque viral inclusions were visible within the cytoplasm of choroidal and ependymal epithelium as well as in mononuclear inflammatory cells. On electron microscopy, they were composed of intracytoplasmic nucleocapsid accumulations. Viria lay free between microvilli of plexus epithelial cells, and budding virus structures were observed at cellular surfaces. Occasionally, complete viria occurred in the cytoplasm of plexus epithelial cells and were surrounded by a unit membrane from which they appeared to arise by budding. The formation of this small cavity can be interpreted as the first stage of vacuole formation.

Rat tracheal organ culture supports replication of parainfluenza 1 (6/94) virus and promotes 6/94 virus rescue from latently infected human brain cells

Rat tracheal organ culture (TOC) supported replication of parainfluenza 1 (6/94) virus. Cell-associated and cell-free viruses were found after primary infection of TOC. In contrast to other mammalian systems, rat TOC was capable of maintaining 6/94 virus infectivity after primary infection. Rat TOC may be considered a potential indicator system that could be used to detect virus latent in human tissue.

Solid phase indirect radioimmunoassay: standardization and applications in viral serology

In solid phase indirect radioimmunoassay (IRIA) antiviral immunoglobulins (Ig) bind specifically to the viral antigen fixed onto wells of microtiter plates. Radioactively labeled (125I) anti-Ig can be used to detect these antiviral antibodies. The sensitivity of the IRIA depends on the amount of antigen in the microtiter wells and the concentration of the 125I-labeled anti-Ig used. To standardize the assay, a method of antigen titration in the IRIA was devised, using parainfluenza type 1 viruses as antigens. The IRIA provides a means to titrate viral antigens with different biologic activities and antibodies against them. A binding inhibition test (BIT) based on IRIA allows the antigenic analysis of different virus strains, as is demonstrated for two closely related parainfluenza type 1 virus strains.

Acute optic neuritis: a virological study in relation to multiple sclerosis

Previous ultrastructural examination of peripheral blood lymphocytes revealed the presence of intranuclear filamentous structures in multiple sclerosis (MS) and in some optic neuritis (ON) patients. The present investigation was undertaken in the attempt to correlate the presence of such structures with the etiology of ON and MS and possibly to demonstrate the viral origin of the filaments. Suitable virological and serological techniques were used to detect and isolate infectious agents from peripheral blood samples and body excretions of 12 monosymptomatic ON patients at their first acute attack. Nevertheless, any efforts to demonstrate the presence of a virus in these patients have been unsuccessful: no evidence of active viral infection was obtained by serological studies of serum and cerebrospinal fluid samples, nor could viral antigens or inclusions be observed by immunofluorescence and cytochemical analysis. Negative results were also obtained from studies performed in parallel on MS patients and various controls. The significance of the failure to isolate infectious agents from either ON and MS patients is discussed.