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Canine calicivirus (CaCV), isolated from feces of a dog with diarrhea, was readily propagated in cultures of canine cells and in a dolphin cell line. Serologic evidence indicated many dogs in at least one geographic area had been infected with CaCV, but its role as an etiologic agent of disease was not established. In cell culture most CaCV virions were strongly cell-associated making purification difficult. CaCV was established as a member of the Caliciviridae by morphology and physicochemical properties of virions (density, sedimentation rate, single major polypeptide, RNA genome size), although some of the properties differed slightly from those of previously described caliciviruses; evidence was also obtained for caliciviral RNA species in infected cells. Based on tests with antisera to numerous caliciviruses and presumed caliciviruses, CaCV appeared to be not closely related to any previously described virus except the stunting syndrome agent of chickens.

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A rapid and sensitive radioimmunoassay for the detection of soluble Yersinia pestis fraction I antigen using antibody-coated beads and radiolabeled immunoglobulin was applied to spleen-liver extracts, rendered noninfectious by either treatment or filtration, from rodents dead of plague. The procedure was capable of detecting nanogram amounts of soluble plague antigen.

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Proteins associated with 36S virus RNA from Vero cells infected with San Miguel sea lion virus, type 2 (SMSV-2), were labelled with 125I. One protein, VPg, remained linked to RNA when subjected to deproteinization techniques. VPg labelled wtih 32P was observed on 36S RNA from purified virions; the quantity of label was compatible with two phosphates per genome. The estimated mol. wt. of SMSV-2 VPg was 15 000.

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The caliciviruses, as a proposed family Caliciviridae, have a distinct virion morphology with cup-shaped depressions on a spherical capsid surface. The viruses have single-stranded RNA, which has a molecular weight about 2.6 x 10(6) and is infectious. The RNA is covalently linked to a small protein. A single major polypeptide is found in the capsid. A subgenomic RNA, molecular weight about 1 x 10(6), coding for the capsid polypeptide is found in infected cells. Caliciviruses infecting swine, pinnipeds and cats have been characterized. Viruses which are morphologically identical to the known caliciviruses have been identified in human feces; these viruses have been shown to be associated with gastroenteritis, but they have not yet been propagated in the laboratory.

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A radioimmune assay method designated St-RIP using a staphylococcal IgG adsorbent, which potentially has broad applications to viral (and nonviral) antigen-antibody systems, was applied to detection of calicivirus antibodies. Purified 125I-labeled virions of San Miguel sea lion virus serotypes 4 (SMSV-4) and 5 (SMSV 5) were incubated with sera; the immune complexes were reacted with an immunoadsorbent, formaldehyde-fixed staphylococci (Staphylococcus aureus protein A producer, strain Cowan I), and collected by centrifugation. Broad cross-reactivity was observed among serotypes of SMSV and vesicular exanthema of swine virus (VESV), but there was no reaction with antisera to six noncaliciviruses. Antibody production in a rabbit inoculated with SMSV-5 polypeptide was monitored by St-RIP assay; reactivity with intact SMSV-4 virion antigen was slightly less than, but closely paralleled, reactivity with SMSV-5 virion antigen. Applicability of the St-RIP test to serologic survey was demonstrated with pinniped, swine, and human (laboratory personnel) sera; numerous positive St-RIP reactions suggested the occurrence of widespread contacts with caliciviruses.

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RNA labeled with [3H]uridine from Vero cells infected with San Miguel sea lion virus in the presence of actinomycin D was analyzed by glycerol density gradient sedimentation and polyacrylamide gel electrophoresis. The predominant single-stranded RNA (36S, 2.6 x 10(6) molecular weight) was genome size. There was also a prominent 22S, 1.1 x 10(6)-molecular weight, single-stranded component and one or more double-stranded or partially double-stranded classes. Replicative forms, sedimenting at 18S, contained single-stranded RNA corresponding to the larger-molecular-weight class. All classes of intracellular RNA and virion RNA were polyadenylated. These findings and results with pig kidney cells infected with vesicular exanthema of swine virus and feline cells infected with feline calicivirus indicate that caliciviruses exhibit a strategy of replication different from typical picornaviruses and supports removal of the caliciviruses from the family Picornaviridae.

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Aerosols of the Moloney murine sarcoma virus (MuSV-M) and leukemia virus (MuLV-M) complex (MuSV-M/MuLV-M) were generated from refluxing atomizers and then aged in rotating drums at 21 degrees C holding temperature with relative humidities ranging from 25 to 76%. The MuSV-M and MuLV-M aerosolized from the same tumor extract preparation survived almost equally at the four humidity levels. Both viruses remained viable in the airborne state for at least 2 hours after aerosolization. When mice were exposed to airborne MuSV-M/MuLV-M, no macroscopic lesions were observed in lungs or other tissues examined during the 2-month postexposure period. On the basis of this study, MuSV-M was determined unsuitable as a "model system" in which a simple aerosol dose response could be used for biohazard evaluation of oncogenic virus aerosols.

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A calicivirus, San Miguel sea lion virus serotype 4, isolate 15FT, externally labelled with 125I, was shown by gel electrophoresis to possess a single major polypeptide. The polypeptide migrated anomalously upon electrophoresis in two sodium dodecyl sulfate (SDS) systems: more slowly than bovine serum albumin in a continuous phosphate-buffered system and more rapidly than bovine serum albumin in a discontinuous system. Estimated molecular weights in the two systems were approximately 71,000 and 64,000, respectively. There was no clear evidence for a minor virion polypeptide. Treatment of purified San Miguel sea lion virions with dimethyl suberimidate, a cross-linking reagent, preserved virion integrity during long-term storage at 4 degrees C. Oligomeric species of the polypeptide were observed upon electrophoresis of products from cross-linked virions. Based upon a preferred polypeptide molecular weight estimate of 71,000 and distribution of oligomeric species, a calicivirion model with 120 monomeric protein units is proposed as an alternative to a 180-unit model.

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Influenza A virus, strain WSNH, propagated in bovine, human and chick embryo cell cultures and aerosolized from the cell culture medium, was maximally stable at low relative humidity (RH), minimally stable at mid-range RH, and moderately stable at high RH. Most lots of WSNH virus propagated in embryonated eggs and aerosolized from the allantoic fluid were also least stable at mid-range RH, but two preparations after multiple serial passage in eggs showed equal stability at mid-range and higher RH's. Airborne stability varied from preparation to preparations of virus propagated both in cell culture and embryonal eggs. There was no apparent correlation between airborne stability and protein content of spray fluid above 0.1 mg/ml, but one preparation of lesser protein concentration was extremely unstable at 50 to 80 per cent RH. Polyhydroxy compounds exerted a protective effect on airborne stability.

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Biophysical properties of three new San Miquel sea lion virus isolates from pinnipeds were examined and compared with those of previously characterized serotypes. The caliciviruses showed an identical sedimentation rate of 183S in 5-20% sucrose. Buoyant densities in CsCl were in the range of 1.35-1.39 g/ml, with differences among the serotypes.

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A simple, economical radioassay system employing disposable polypropylene microcentrifuge tubes was developed. Plastic adapters permitted automatic operation in liquid scintillation spectrometers. Counting efficiencies of (3)H, (14)C, (32)P, and (125)I in liquid scintillation cocktails and of (32)P by Cerenkov radiation (at lower efficiency in absence of added scintillator) were comparable to those in standard vials. Multipurpose use of the microtubes made the system versatile and expedient, e.g., collection of precipitates and radioassay in the same container. Collection of radioimmune precipitates was aided by a carrier inorganic precipitate, Mg(2)P(2)O(7).

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Heterogeneity of buoyant density and RNA content of virions of Moloney murine leukemia-sarcoma complex [MSV (MLV)] was the result of passage at low dilution. Heterogeneous stocks revealed two major RNA components in the population, with the smaller component, apparent mol wt 4 x 10(6) to 5 x 10(6), becoming predominant upon serial passage at low dilution. Concomitantly, infectivity titers of both MLV and MSV decreased upon serial passage at low dilution. MSV (MLV) passaged at high dilution retained high titers and a rather homogeneous high-molecular-weight RNA population characteristic of high-buoyant-density virions. Interference of both MLV and MSV replication was demonstrated by employing mixed inocula containing both low- and high-dilution passage stocks of MSV (MLV). In contrast to results with MSV (MLV), MLV freed of MSV by limit dilution did not show heterogeneity of buoyant density or of RNA when propagated at low dilution.

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