A comparative electron microscopic study on the morphogenesis of canine distemper and rinderpest viruses

Ultrastructure of equine morbillivirus

The ultrastructure of the equine morbillivirus (EMV) which was implicated in the death of one human and fourteen horses in Queensland, Australia during September 1994 and a 36 year old man from Queensland in October 1995 is described. The ultrastructure of the virus and the intracellular virus-specific structures are characteristic for the family Paramyxoviridae. Cytoplasmic nucleocapsids were observed within the infected cells monolayers, endothelial cells (lung) of infected horses and the neurons within the brain of the 36 year old Queensland man. Aggregates of smaller nucleocapsid-like structures were also observed within the brain of the same man; these did not react with sera from recovered EMV-infected horses or from a recovered EMV-infected human. Co-examination of rinderpest virus (RPV), bovine parainfluenza-3 (BPIV-3), human respiratory virus (HRSV) and Sendai virus revealed that their envelope-associated surface projections are equivalent in length to the 15 nm spikes of EMV. EMV differed from these other viruses in that the majority of virions possessed surface projections of two distinct lengths (18 and 15 nm). Further ultrastructural examinations of plaque purified EMV revealed a small percentage of EM viruses possessed a mixed array of surface projections indicating that the 'double-fringed' (DF) particles may be the result of a post-translational modification(s).

Viral antigen distribution in organs of cattle experimentally infected with rinderpest virus

The distribution of viral antigen in various organs of four approximately 10-month-old castrated male Friesian cattle experimentally infected with a highly virulent strain of rinderpest virus was studied. A monoclonal antibody with genus-specific reactivity for morbilliviruses was applied in an indirect immunoperoxidase method performed on formalin-fixed, paraffin-embedded tissue sections. Rinderpest viral antigen was located mainly in the cytoplasm of the epithelial cells of the digestive, respiratory, and urinary tracts, as well as in the cells of endocrine glands (adrenal, thyroid) and exocrine glands (salivary glands, sebaceous glands, exocrine pancreas). Furthermore, different types of cells in lymphatic organs contained rinderpest viral antigen. In contrast to the documented results of studies carried out with other morbilliviruses, tissues of the central nervous system did not contain viral antigen. Various types of epithelial and lymphoreticular cells are the main targets of a virulent strain of rinderpest virus in vivo.

Encephalitis following vaccination against distemper and infectious hepatitis in the dog. An optical and ultrastructural study

A 4-month-old, male, healthy dog developed CNS-symptoms 10 days after the second vaccination with live, attenuated distemper and canine hepatitis virus. The animal was euthanized after 2 weeks of illness. Light and electron microscopic examination of the CNS showed a partly necrotizing encephalomyelitis with numberous intranuclear and intracytoplasmic inclusion bodies, and the presence of probable pseudomyxovirus nucleocapsids and of crystalloid and tubuloreticular aggregates. Although there was conformity of inclusion bodies and probable viral structures as revealed by electron microscopy, the latter showed a much wider distribution. In addition, viral structures of a different type were found in polymorphonuclear leukocytes and vascular endothelial cells. Several morphological criteria led to the supposition that they are Picornaviruses, or possibly Arenaviruses. It is thought that their role in the disease process was at best an indirect one.

Morphology of the Warthin-Finkeldey giant cells in monkeys with experimentally induced measles

The lymphoid tissues of 9 monkeys infected experimentally with wild type measles virus were examined by light and electron microscopy. Multi-nucleated giant cells of the Warthin-Finkeldey type were found 7 to 11 days after virus inoculation. The giant cells occurred mostly in the germinal center of lymphatic follicles, where they underwent degeneration and disappeared rapidly. Lymphoid and reticular types of giant cells were recognized. The ultrastructural evidence suggested that some of the nuclei contained in giant cells were formed by an aberrant nuclear cleavage. The majority of giant cells, however, were postulated to arise from virus-mediated cell fusion, although direct evidence of cell fusion was not seen. Peculiar nuclear changes, in which some nuclei and fragments of the outer nuclear membrane were contained in a common outer membrane of the nuclear envelope, were observed in all lymphoid giant cells. Both cytoplasmic and intranuclear inclusions were seen to be composed of viral nucleoprotein strands. The former were detected in all giant cells of both types, and the latter in occasional nuclei, providing the direct evidence that giant cell formation resulted from replication of the virus.

Sporadic bovine meningo-encephalitis-isolation of a paramyxovirus

Isolation of a viral agent (107) directly from brain explants of a 15-month-old heifer with symptoms of a sporadic encephalomyelitis is described. The virus shares properties with the paramyxovirus family. It grows in a variety of cell cultures from different species, and induces nuclear and cytoplasmic inclusion bodies in infected cells. Nucleocapsids measuring 17 nm in diameter were found in the nucleus and cytoplasm of these cells when studied electron microscopically, thus indicating a close relationship of the agent to the measles-distemper-rinderpest group. No infectious virus was released from infected cells, although alignment of nucleocapsids was observed beneath the cell membrane, and no hemagglutinating activity could be detected with the methods employed. The 107 agent was compared serologically with parainfluenza viruses type 1, 2 and 3, simian virus 5, mumps and Newcastle disease virus (NDV), two bovine respiratory syncytial viruses and measles/subacute sclerosing panencephalitis, distemper and rinderpest viruses, always using 107 virus infected CV1 cells and antiserum of the different viruses in indirect FA tests. Positive FA reactions were observed only with two sera obtained from SSPE patients with high antibody titer to SSPE virus, and with one rabbit-anti-rinderpest serum. The titers of these sera to 107 virus, however, were significantly lower than those against homologous viruses. Five out of 9 sera from randomly selected healthy cattle showed antibody titers between 1:10 and 1:80 to 107 virus in FA tests. The significance of these results is discussed with respect to the epidemiology of SSPE in children and its possible implication with rinderpest in Europe.