Unclassified Viruses Research Articles

Cellular lesions in intestinal mucosa of gnotobiotic calves experimentally infected with a new unclassified bovine virus (Breda virus).

Four gnotobiotic calves were inoculated intranasally with Breda virus within two hours after cesarean section. Three calves developed diarrhea between 48 and 60 hours after inoculation; one calf was killed at 36 hours. Consistent microscopic findings in the intestinal mucosae of calves with diarrhea were cytopathologic changes in enterocytes of the lower small intestine, large intestine, and dome epithelial cells and an acute inflammatory response with cellular infiltration and subtle changes in capillaries. Virions with average dimensions of 35 x 80 nm were seen in rounded cells that had severe cell swelling, dilatation of the cytocavitary network, and hydropic degeneration. Virions were most often in multiple, large autophagolysosomes. There was a good correlation in detection of virus in cells with electron microscopy and indirect immunofluorescence. No lesions were detectable in two control calves killed five days after inoculation.

Studies with an unclassified virus isolated from diarrheic calves

A transmissible agent (Breda agent) was isolated from a calf with diarrhea and shown to be infectious by inoculation orally into gnotobiotic and conventionally reared calves. The “Breda” agent had the morphology of a virus and possessed a hemagglutinin. Antigenic studies showed the virus to be antigenically different from bovine coronavirus, parainfluenza 3 virus, bovine rotavirus, bovine parvovirus and bovine pestivirus (BVD). Attempts to culture the virus in cell or organ cultures or in embryonated eggs, were unsuccessful. The virus was either spherical or kidney shaped, with 7–9 nm peplomers on the surface. A few particles possessed coronavirus processes of 17–20 nm, but these were arranged irregularly and were thought to be tissue debris. Three out of eight experimental calves developed severe diarrhea and the lesions in the small and large intestines were similar to those reported for coronavirus. The virus replicated in the jejunal and ileal regions of the small intestine and in the spiral colon, as judged by immunofluorescence. The virus multiplied in all experimental calves and was excreted in the feces; excretion correlating with the onset of diarrhea or a change in the appearance of the feces. There was little or no malabsorption measured by the uptake of D-xylose and the fact that infection of both the crypt and villus epithelial cells was observed, suggests that the pathogenesis may be different from rotavirus and coronavirus. Fourteen of fortyseven calves in the outbreak were infected with the virus, virus was not identified in other farm outbreaks of the disease.

Characterization of a Picornavirus Isolated from Broiler Chicks

The rectal content of an apparently normal 1-week-old broiler chick yielded an unclassified cytopathogenic virus with cytopathic effects of the round type. It was identified as a picornavirus from the following: ribonucleic acid in the viral core; virus growth in the cytoplasm; a particle about 30 nm in diameter; resistance to ethyl ether, chloroform, trypsin, and acid; relative heat-lability; and partial stabilization to molar magnesium chloride. The virus was stable under freezing and thawing, and sonication. It was distinguished from avian encephalomyelitis virus by the neutralization test.

Some Unclassified Viruses and Virus-Like Agents

Some Unclassified Viruses and Virus-Like Agents

PROBLEMS ASSOCIATED WITH THE USE OF ARTHROPOD VIRUSES IN PEST CONTROl

Over 700 species of insects and mites are reported to have viral diseases ( 15). More than 320 viruses have been isolated from over 250 insect and mite species of agricultural importance. At least 38 arthropod species have been examined in terms of control with arthropod viruses. The production of arthropod viruses from 5 insect species has been industrialized on a pilot basis by private enterprise in the United States (9). Most of the species investigated for control with arthropod viruses are important pests of food, fiber, and forest crops in the world. Represented are species for which large amounts of pesticides are currently used and which plant protection specialists have the greatest difficulty controlling. In the state of California, the combination of estimated damage and crop losses caused by species in this category (bollworm, armyworm, looper, cutworm, gelechiid moths, leafroller moths, codling moth, and citrus red mite) amounted to over $73 million in 1970 (53). The status, characterization, nomenclature, and classification of arthropod viruses was recently reviewed (15). Thus far, arthropod viruses are represented by six genera, namely, Baculovirus (nuclear polyhedrosis and granulosis viruses), Pox­ virus (Entomopoxviruses), Iridiovirus, Parvovirus (Densonucleosis viruses), En­ terovirus, and Rhabdovirus; one group, cytoplasmic polyhedroses; and many unclassified viruses. The species of Baculovirus are the best known arthropod viruses and some have been used for pest control on a commercial basis (9). During the 1950s, alfalfa growers in California collected and utilized nuclear polyhedrosis virus (NPV) to control the alfalfa caterpillar (Colias eurytheme) (48). For many years growers and pest control operators in various parts of the United States have field collected and utilized NPV for the control of the cabbage looper ( Trichoplusia ni) on a variety of food crops (73). Spodoptera NPV has been utilized on a limited scale in California

Serological and pathogenicity studies with some unclassified porcine adenoviruses

Eight unclassified porcine adenoviruses were compared serologically with each other and with prototype strains of porcine adenovirus types 1 to 4 by means of reciprocal virus neutralization tests. There was no relationship between any of the unclassified viruses and porcine adenovirus type 4, but unidirectional cross reactions did occur between 7 of the new viruses and one or other of porcine adenovirus types 1 to 3. In addition, cross reactions occurred among all the unclassified viruses, but all were unidirectional. Each of the unclassified viruses was inoculated intranasally into 2 hysterotomy-derived, colostrum-deprived, 7-days-old piglets. One piglet of each pair was killed 6 days, and the other 8 days, after inoculation. Diarrhoea occurred in one pair of piglets and oedema of the mesocolon was seen at post mortem examination of 5 piglets. Virus was isolated from the tonsil, ileum, colon and rectum of most of the inoculated piglets, but not from the liver, spleen, kidney, pancreas, brain, lung, bronchial or mediastinal lymph node, parotid salivary gland, mesenteric lymph or jejunum.

The Status of Viruses Pathogenic for Insects and Mites

Several very different reviews could be presented under this title, but here status is taken to mean condition of things, and the emphasis is on recent investigations­ chiefly on those which have some relevance to the exploitation of viruses for pest control. As Tarasevich (190) has emphasized this aim involves the solution of many fundamental problems, such as those relating to the characterization, entry, multi­ plication, and epizootiology of viruses. It is a testimony to the present interest in insect viruses that for the purpose defined, it was necessary to consider over 400 papers published since January 1970. Many of these have had to be omitted from the list of references, and the results, as for earlier publications, are referred to only through later papers, reviews, and textbooks (31, 36, 57, 89, 93, liS, 131, 132, 170, 171, 194, 200). Aspects of the ecology and epizootiology of viruses have been reviewed or discussed (169, 183, 186, 187, 228), and also insect tissue cultures and the part they can play in the study and production of insect viruses have been reviewed (26, 80, 199, 210). The characterization, nomenclature, and classification of insect viruses are all matters for active research and debate (128). At the present time, a system being worked out by the International Committee for the Nomenclature of Viruses seems to be favored and has been adopted in this review. An important feature of this system, based mainly on the properties of the virus particle, is the cryptogram which embodies in four pairs of symbols certain biochemical, biophysical, and morphologi­ cal features of viruses or groups of viruses (221). As knowledge advances it may appear desirable to give less emphasis in the classification to the attributes of viruses in their dormant form (the virions) and to include certain dynamic criteria (179, 222). So far, insect viruses are represented in six genera and one group (group is a provisional term), but there are also many unclassified viruses. Up-to-date information about the distribution of the viruses in the different host orders has been kindly provided by M. E. Martignoni (personal communication) from a computer-based catalog (135) (see Table I). Some relatively familiar, but

Systematics of RNA tumor viruses and virus-like particles of human origin.

[(3)H]DNA copies of avian, feline, murine, and primate RNA tumor virus genomes were synthesized in vitro by an RNA-dependent DNA polymerase reaction. These DNAs were hybridized to 60-70S RNA that had been purified from the viruses. The amount of the [(3)H]DNA hybridized yielded a measure of the genetic relatedness among the DNA preparations synthesized by the viruses. When many combinations of DNA and RNA were analyzed, the pattern of hybridization showed in some cases that the DNA copies of the viral RNA were related to each other in the same way that the natural hosts of the viruses are phylogenetically related. This pattern was observed only among the RNA leukemia viruses. The sarcoma component in sarcoma-leukemia viruses from rats and primates appeared to be unusually closely related. The mouse mammary carcinoma virus and two unclassified viruses (MPMV and Visna) appeared to be genetically distinct.A similar analysis of DNA synthesized by an RNA-dependent DNA polymerase associated with a viral-like particle obtained from the cytoplasm of human leukemic white blood cells demonstrated that this DNA occupied a space in the affinity pattern of leukemia viruses which is expected of a nucleic acid from a primate-type-C RNA tumor virus. This observation strengthens earlier evidence that components of RNA tumor viruses are associated with human leukemia.

THE ISOLATION OF AN UNCLASSIFIED VIRUS FROM AN OUTBREAK OF INFANTILE DIARRHOEA.

A virus was isolated from fifteen of nineteen children living in an infants' home during an outbreak of diarrhoea. The virus possesses many of the characteristics of the enterovirus group but is serologically distinct from any of the accepted members of this group. It is non-pathogenic for unweaned mice, non-cytopathic in tissue cultures of monkey kidney, but is rapidly cytopathic for tissue-cultured cells of human origin. It is serologically similar to virus Hu 659 isolated by Abrahams in the United States (personal communication).I should like to thank the Director-General of Public Health and State Psychiatric Services, New South Wales, for permission to publish.

Cytoplasmic crystals in FL cells infected with an unclassified enteric virus (presumably a new type of ECHO)

Cytoplasmic crystals in FL cells infected with an unclassified enteric virus (presumably a new type of ECHO)

Murray Valley encephalitis: a survey of suspected mosquito vectors.

SummaryA survey of the mosquitoes of a section of the Murray River Valley of Australia has provided data of value to epidemiologic investigators of Murray Valley encephalitis and to persons possibly concerned with mosquito problems in this area.In these studies, 16 species of mosquitoes are recorded. Laboratory tests for Murray Valley encephalitis virus on 17,833 mosquitoes representing 10 species have been negative. Several other types of virus, an unclassified pox virus and myxomatosis virus, were isolated from mosquitoes collected.Interpretation of data on the biology of adult mosquitoes permits some evaluation of the relative potential importance of the various species as vectors of Murray Valley encephalitis. It is concluded that certain species should be suspected as vectors, in the following order of importance: Culex annulirostris, Culex fatigans “complex,” Mansonia linealis, Aedes theobaldi and possibly Anopheles annulipes. As no epidemiologic evidence could be found that the virus was still present in the area studied, the negative findings neither prove nor disprove that mosquitoes are vectors of this virus, and further studies are warranted.A sample of 71 larval collections has been analyzed as to larval habitats, association of various species, the conditions of water source and use leading to mosquito breeding and possible control problems. It is suggested that an effective program for mosquito control would require modification of existing irrigation facilities and practices, as well as an attack on natural and purely domestic water sources of mosquitoes.