Efficacy of viral components of a nonabortigenic combination vaccine for prevention of respiratory and reproductive system diseases in cattle.

Efficacy and safety of components of an IM-administered vaccine for prevention of infectious bovine rhinotracheitis virus (IBRV), parainfluenza type-3 (PI-3) virus, bovine viral diarrhea virus (BVDV), and respiratory syncytial virus (RSV) infections and campylobacteriosis and leptospirosis were evaluated in cattle, including calves and pregnant cows. Challenge of immunity tests were conducted in calves for IBRV, PI-3 virus, or BVDV vaccinal components. All inoculated calves developed serum-neutralizing antibodies and had substantially greater protection (as measured by clinical rating systems) than did controls after challenge exposure to virulent strains of IBRV, PI-3 virus, BVDV, or RSV. In in utero tests, IBRV or bovine RSV vaccinal strains were inoculated into fetuses of pregnant cows. Histologic changes or abortions did not occur after fetal inoculation of the RSV vaccinal strain, and 10 of 14 fetuses responded serologically. Of 9 fetuses, one responded serologically to the IBRV vaccinal strain after in utero inoculation and was aborted 3 weeks later. In an immunologic interference test, 10 calves vaccinated with 2 doses of the multivalent vaccine, containing the 4 viral components and a Campylobacter-Leptospira bacterin, developed serum-neutralizing antibodies to IBRV, PI-3 virus, BVDV, and RSV without evidence of serologic interference. Under field conditions, 10,771 cattle, including 4,543 pregnant cows, were vaccinated. Vaccine-related abortions did not occur.

Further evidence for entry of infectious bovine rhinotracheitis virus into bovine kidney cells.

The penetration of bovine kidney cells by infectious bovine rhinotracheitis virus, a member of the herpesvirus group, was investigated using the direct immunoferritin labeling technique. Electron microscopic examination of infected cells after 10 min at 37°C revealed fusion between viral envelope and cell membrane; the former reacted with the ferritin particles conjugated with antiviral antibody. However, shortly after penetration of the nucleocapsid, viral-specific antigenic sites on the plasma membrane were not detected by the immunoferritin technique. Antigenically reactive structures in a disorganized array were frequently detected extracellularly, situated above the penetration sites as indicated by the internalized nucleocapsids.

Purification and buoyant density of infectious bovine rhinotracheitis virus.

A purification scheme for infectious bovine rhinotracheitis virus utilizing rate-zonal centrifugation in a 10-40% potassium tartrate gradient was described. The density of IBRV in the potassium tartrate gradient was found to be 1.22 g/cm3. Electron microscopic examination of purified virus preparations revealed homogeneous populations of enveloped virions with minute projections on the envelope surface.

Electron Micrography of Bud Formation in Metschnikowia krissii.

The fine structure of bud formation of Metschnikowia krissii was studied by means of ultramicrotomy and transmission electron microscopy. Bud protrusion and development were observed by scanning electron microscopy. Bud formation in this yeast takes place by an extension of a small localized area of the existing parent wall. The parent cell and its bud are initially separated by the plasmalemma, creating an intercellular site within which the generation of new cell wall (bud and birth scar areas) occurs centripetally. When the dividing wall is complete and new cell wall material is formed, a narrow cleavage plane becomes increasingly defined. This cleavage plane apparently proceeds laterally toward the direction of the existing outer walls which rupture, resulting in the separation of the bud from the parent cell. The bud scar is prominently convex in shape; the birth scar is less conspicuous and initially concave in shape. Comparison of bud formation in M. krissii is made with that observed in Saccharomyces cerevisiae and Rhodotorula glutinis.

Biosynthesis of the influenza virus envelope in abortive infection.

Synthesis and processing of the envelope proteins of influenza A virus (fowl plague virus) have been analysed in BHK, HeLa and L cells, in which the virus undergoes abortive replication and does not form virus particles, and in the productive chick embryo fibroblast system. In abortive infection, synthesis of the M protein is specifically inhibited. The extent of this defect varies depending on the host cell and the amount of virus particles formed closely reflects the amount of M synthesized. Cell fractionation experiments demonstrated that the haemagglutinin glycoprotein HA is synthesized in abortive as well as in productive cells at the rough endoplasmic reticulum, that it migrates via smooth internal membranes to the plasma membrane and that it is cleaved by proteolysis into fragments HA1 and HA2 in the course of migration. Immune electron microscopy using monospecific antibodies against haemagglutinin and neuraminidase showed that both glycoproteins are exposed at the cell surface. Thus, synthesis and processing of the virus glycoproteins does not depend on the formation of the M protein. However, the M protein appears to be necessary for budding and thus for particle formation.

Electron micrography study of the asci and ascospores of Metschnikowia Kamienski.

Internal and surface structures of asci and ascospores were studied by transmission electron microscopy (TEM) and by scanning electron microscopy (SEM) to establish the character and number of ascospores within the ascus of Metschnikowia krissii. Enzyme digestion with snail gut enzymes and SEM examination suggested the presence of a single ascospore enclosed in a thick sheath of epiplasmic materials. Two closely associated ascospores without an epiplasmic sheath were clearly distinguishable from asci of M. bicuspidata var. chathamia when similarly treated. Ultramicrotomy and TEM established conclusively that M. krissii produced a single ascospore per ascus. Neither SEM nor TEM revealed any morphological detail of the ascospores of taxonomic significance.