Susceptibility of Four Abalone Species, Haliotis gigantea, Haliotis discus discus, Haliotis discus hannai and Haliotis diversicolor, to Abalone asfa-like Virus

Abalone amyotrophia is a viral disease that causes mass mortality of juvenile Haliotis discus and H. madaka. Although the cause of this disease has yet to be identified, we had previously postulated a novel virus with partial genome sequence similarity to that of African swine fever virus is the causative agent and proposed abalone asfa-like virus (AbALV) as a provisional name. In this study, three species of juvenile abalone (H. gigantea, H. discus discus, and H. diversicolor) and four species of adult abalone (the above three species plus H. discus hannai) were experimentally infected, and their susceptibility to AbALV was investigated by recording mortality, quantitatively determining viral load by PCR, and conducting immunohistological studies. In the infection test using 7-month-old animals, H. gigantea, which was previously reported to be insusceptible to the disease, showed multiplication of the virus to the same extent as in H. discus discus, resulting in mass mortality. H. discus discus at 7 months old showed abnormal cell masses, notches in the edge of the shell and brown pigmentation inside of the shell, which are histopathological and external features of this disease, while H. gigantea did not show any of these characteristics despite suffering high mortality. Adult abalones had low mortality and viral replication in all species; however, all three species, except H. diversicolor, became carriers of the virus. In immunohistological observations, cells positive for viral antigens were detected predominantly in the gills of juvenile H. discus discus and H. gigantea, and mass mortality was observed in these species. In H. diversicolor, neither juvenile nor adult mortality from infection occurred, and the AbALV genome was not increased by experimental infection through cohabitation or injection. Our results suggest that H. gigantea, H. discus discus and H. discus hannai are susceptible to AbALV, while H. diversicolor is not. These results confirmed that AbALV is the etiological agent of abalone amyotrophia.

A novel quasi-viral agent, MaTu, is a two-component system

MaTu is a quasi-viral agent presumably derived from a human mammary tumor. In some respects it resembles classical viruses and in some the "slow viruses," and in others it is different from both. Using monoclonal antibodies (Mabs), we showed that it is a two-component system. One part of the complex, MX, is exogenous; it is manifested by a protein, p58X, which is a cytoplasmic antigen and it reacts with some natural sera of man and of various animals. The other component, MN, is endogenous to human cells. This is manifested by a twin protein(s), p54/58N, localized on the cell surface and in the nucleus. This protein is absent in rapidly growing, sparse cultures of HeLa, but it is inducible either by keeping the cells in dense cultures or, more efficiently, by infecting them with MX. Both inducing factors are synergistic. Only p54/58N is associated with virions of vesicular stomatitis virus (VSV), reproduced in MaTu-infected HeLa. This suggests that MN is responsible for complementation of VSV mutants and for the formation of the VSV (MaTu) pseudotype. Both p54/58N peptides are glycosylated and they form oligomers linked by disulfidic bonds; p58X is not glycosylated and it does not form S-S-linked oligomers.

Isolation of cytopathic small round viruses with BS-C-1 cells from patients with gastroenteritis

Fecal extracts from 12 subjects in outbreaks of oyster-associated nonbacterial gastroenteritis were inoculated with BS-C-1 cells for isolation of the causative viruses. Cytopathic agents were isolated from 3 patients. No cross-neutralizing reactions were observed between the isolates and prototypes of human enteroviruses. The isolates were approximately 30 nm in diameter and had a distinct ultrastructure resembling that of astroviruses. Four polypeptide bands with molecular sizes of 42, 28, 27, and 22 kDa were seen on SDS-PAGE analyses. Seroconversion against the isolate was observed in 18 (31.6%) of 57 patients involved in five of seven outbreaks examined by neutralization test. A protein band characteristically reactive with the paired serum samples was detectable at 42 kDa by immunoblot assay. These results suggested that some small round viruses resembling astroviruses might show cytopathic effect in BS-C-1 cells and may be associated with an oyster-related gastroenteritis.

Mystery swine disease in The Netherlands: the isolation of Lelystad virus

In early 1991, the Dutch pig-industry was struck by the so-called mystery swine disease. Large-scale laboratory investigations were undertaken to search for the etiological agent. We focused on isolating viruses and mycoplasmas, and we tested paired sera of affected sows for antibodies against ten known pig viruses. The mycoplasmas M. hyosynoviae, M. hyopneumoniae, and Acholeplasma laidlawii, and the viruses encephalomyocarditis virus and porcine enterovirus types 2 and 7 were isolated from individual pigs. An unknown agent, however, was isolated from 16 of 20 piglets and from 41 of 63 sows. This agent was characterised as a virus and designated Lelystad virus. No relationship between this virus and other viruses has yet been established. Of 165 sows reportedly afflicted by the disease, 123 (75 per cent) seroconverted to Lelystad virus, whereas less than 10 per cent seroconverted to any of the other virus isolates or to the known viral pathogens. Antibodies directed against Lelystad virus were also found in pigs with mystery swine disease in England, Germany, and in the United States. We conclude that infection with Lelystad virus is the likely cause of mystery swine disease.

Application of control measures against viral haemorrhagic disease of rabbits in the Czech and Slovak Federal Republic

The first outbreaks of viral haemorrhagic disease (VHD) of rabbits were reported from eastern Slovakia in 1987. In 1988, the infection spread throughout the Czech and Slovak Federal Republic. Electron microscopy was used by the Veterinary Research Institute in Brno to diagnose the disease during the early stage of infection. At present, the regional laboratories of the veterinary investigation services use the haemagglutination and the direct immunofluorescence tests as the principal methods to demonstrate the causal agent. Indirect immunofluorescence and immunoperoxidase techniques have been developed to demonstrate VHD virus, while the enzyme-linked immunosorbent assay (ELISA) has been used to detect antibodies. Diagnostic kits, allowing a wide use of these methods, are now available commercially. Two types of inactivate vaccines were developed and produced in 1988 and 1989. VHD is controlled by vaccination of exposed rabbit colonies. This is accompanied by other preventive and protective measures, directed by district veterinary officers following instructions from federal authorities.

Immunological characterization of the Marin County strain of astrovirus

Marin County virus (MCV) was isolated from a stool suspension and serially propagated in human embryonic kidney cell cultures. MCV particles in stool and cell-propagated virus stocks showed reactivity by immune electron microscopy (IEM) with rabbit antiserum to astrovirus type 5. MCV antigen was also detected in two MCV stool samples by enzyme immunoassay (EIA) with an astrovirus group-specific monoclonal antibody. Acute and convalescent sera from 3 of 3 MCV-infected patients showed seroconversion to cell-propagated MCV by EIA. Immunofluorescence of MCV propagated in cell culture showed positive reactivity with an astrovirus group specific monoclonal antibody and astrovirus type 5 antiserum, with some cross-reactivity with astrovirus type 1. Similar results were obtained with the prototype strain of astrovirus type 5. However, in plaque-reduction assays, both the prototype astrovirus type 5 and MCV were neutralized by type 5 antiserum only. We conclude that MCV can be serially propagated by techniques used for previously described astroviruses and is serotypically an astrovirus type 5.

Foodborne Snow Mountain agent gastroenteritis with secondary person-to-person spread in a retirement community

A variety of small round-structured viruses are being recognized with increasing frequency as a cause of gastroenteritis in the community, but have rarely been reported to cause outbreaks in hospitals or extended-care facilities. From March 20 through April 15, 1988, an outbreak of gastroenteritis occurred in a retirement facility in the San Francisco Bay area. Illness was characterized by diarrhea, nausea, and vomiting; two residents died. Attack rates were 46% (155 of 336) in residents and 37% (28 of 75) in employees. During the initial outbreak period, illness among residents was associated with two shrimp meals served in the facility dining hall (odds ratio = 6.7). Person-to-person transmission probably occurred: The risk of becoming ill one or two days after a roommate became ill was significantly greater than that of becoming ill at other times during the outbreak (risk ratio = 6.5). Microbiologic examinations for bacterial and parasitic enteric pathogens were negative; however, 27-nm viral particles were detected by immune electron microscopy and by blocking enzyme immunoassay to Snow Mountain agent in stools obtained at the onset of illness from one of six ill residents. Seroconversion (greater than fourfold antibody rise) to Snow Mountain agent was detected in acute- and convalescent-phase serum specimens from five of six ill residents as measured by enzyme immunoassay, but not for Norwalk agent as measured by radioimmunoassay. This report of an outbreak of Snow Mountain agent gastroenteritis in an extended-care facility documents that these difficult-to-identify 27-nm viruses can cause outbreaks in inpatient settings.

Diagnosis of astrovirus gastroenteritis by antigen detection with monoclonal antibodies

An enzyme-linked immunosorbent assay (ELISA), based on monoclonal antibodies to the astrovirus group antigen, was designed for the detection of astroviruses in stools of patients with gastroenteritis. Compared to immune electron microscopy used as the standard test, the sensitivity of the astrovirus ELISA was 91% (31/34) and the specificity was 96% (54/56). All five of the known astrovirus serotypes could be detected in 16 samples on which serotyping was done. In tests on 155 stools containing other enteric viruses, including adenoviruses, rotaviruses, caliciviruses, Hawaii virus, Snow Mountain virus, and Norwalk virus (30, 20, 70, 24, 4, and 7 samples, respectively), only 3 were positive in the astrovirus ELISA. The combined specificity for all astrovirus immune electron microscopy-negative samples was 98% (206/211). The results demonstrate that the new ELISA provides a sensitive and specific means for the diagnosis of astrovirus gastroenteritis.

Western blot (immunoblot) assay of small, round-structured virus associated with an acute gastroenteritis outbreak in Tokyo

Small, round-structured virus (SRSV) was detected in a stool specimen of a patient during an acute gastroenteritis outbreak in Tokyo and was tentatively named SRSV-9. SRSV-9 was purified by sucrose velocity gradient centrifugation after CsCl density gradient centrifugation. The buoyant density of SRSV-9 appeared to be 1.36 g/ml in CsCl. A Western blot (immunoblot) assay using the biotin-avidin system revealed that SRSV-9 was antigenically related to the Hawaii agent but distinct from the Norwalk agent and contained a single major structural protein with a molecular size of 63.0 +/- 0.6 kilodaltons. The prevalence of SRSV-9 infection in Tokyo was surveyed by the Western blot antibody assay by using a crude virus preparation as the antigen. Seroconversion was observed in 56.5% of the patients involved in the outbreaks from which SRSV was detected by electron microscopy.

Antigenic characterization of cell-cultivated astrovirus serotypes and development of astrovirus-specific monoclonal antibodies

Cultivation of human astroviruses in human embryonic kidney or LLCMK2 cell cultures was corroborated for four of the five serotypes originally reported (types 1, 2, 4, and 5). By using type-specific rabbit antisera and immunofluorescence of virus-infected cells, we readily distinguished between serotypes of astrovirus; however, these serotypes showed a high degree of cross-reactivity by enzyme-linked immunoassay, a result indicating the presence of a group antigen. We prepared monoclonal antibodies to astrovirus type 2 antigen and selected them on the basis of group antigen reactivity. The antibodies were reactive with the four astrovirus serotypes that we could cultivate, as well as with the Marin County strain of astrovirus. A previously reported cell-cultivated astrovirus type 3 also reacted with the monoclonal antibodies. These monoclonal antibodies, and the finding of group reactivity among the human astroviruses, should facilitate studies on the importance of these viruses as agents of viral gastroenteritis.

The development and evaluation of radioimmune assays for the detection of immune globulins M and G against astrovirus

The development and evaluation of radioimmune assays for the detection of IgM and IgG antibodies to astrovirus are described. The test was shown to be sensitive and specific, and suitable for screening large numbers of sera. The use of the assays has established that astrovirus type 1 is prevalent in the United Kingdom and that not only infants but also schoolchildren and elderly patients are affected. Further evidence is given to support the view that Marin County Agent is antigenically related to astrovirus type 1.

Snow Mountain agent gastroenteritis from clams

A 1983 investigation of two clambake-related gastroenteritis outbreaks in Rochester, New York, showed that 84 (43%) of 196 persons interviewed had an acute illness characterized by watery diarrhea, vomiting, and abdominal cramps. None of the ill persons were hospitalized or had complications. Illness was associated with eating raw (p = 0.002) or baked (p less than 0.01) hard-shell clams, with the risk of illness increasing with the total number of clams consumed (p less than 0.01). The median incubation period and duration of illness were 36 and 44 hours, respectively. Stool samples obtained 2-4 days after onset of illness were negative for commonly recognized bacterial and viral pathogens. However, of 31 persons whose stools were tested, the stool of only one ill person was positive by enzyme-linked immunosorbent assay for the Snow Mountain agent, one of the Norwalk-like viruses. Paired serum specimens from six (67%) of nine ill and two (29%) of seven well persons showed a fourfold or greater rise in antibody titer to Snow Mountain agent. Persons who ate clams were more likely to seroconvert to Snow Mountain agent (eight of 12) than were those who did not eat clams (zero of four) (p = 0.04). The clams were harvested off the coast of southern Massachusetts in late October, when harvest waters were documented to be contaminated by untreated municipal sewage. This report describes the first documented outbreak of shellfish-associated gastroenteritis attributed to Snow Mountain agent of which we are aware.

Enzyme-linked immunosorbent assays for Snow Mountain and Norwalk agents of viral gastroenteritis

Enzyme-linked immunosorbent assays (ELISAs) for antigen detection and blocking ELISAs for serum antibody rises were developed for the Snow Mountain and Norwalk agents of viral gastroenteritis. The ELISAs were as sensitive as the existing radioimmunoassays and were specific for the Snow Mountain or Norwalk agent. The blocking ELISAs detected the same number of significant rises in antibodies to these agents as did the existing blocking radioimmunoassays.

Preliminary characterisation of torovirus-like particles of humans: comparison with Berne virus of horses and Breda virus of calves

Pleomorphic virus-like particles have been observed by electron microscopy in the faeces of children and adults with diarrhoea. Some of these particles were approximately 100 nm in diameter and had a "fringe" of closely applied peplomers approximately 10 nm long; they closely resembled Berne virus of horses and Breda virus of calves, the two representatives of a newly proposed family called the Toroviridae. In one sample a toroidal nucleoprotein-like structure was observed within the particles. For two samples a buoyant density of 1.14 g/ml was determined by centrifugation through a sucrose density gradient. One sample possessed a haemagglutinin for rat erythrocytes. The serological relationship between these different viruses was observed by immune electron microscopy, haemagglutination inhibition, and serum neutralisation. The role of these virus-like particles as candidate pathogens of humans is discussed.

Purification and properties of an intranuclear virus-specific antigen from tissue infected with Borna disease virus

A virus-specific antigen was extracted from brains of rats and from MDCK cells infected with Borna disease (BD) virus and purified to homogeneity by immunoaffinity chromatography and HPLC. The antigen consists of two components which are almost equal in size (38 000 mol. wt.), and it forms aggregates in its native form. The virus specificity of the two antigenic entities was confirmed by immunoblots with convalescent serum and monoclonal antibodies. Immunofluorescent staining with monoclonal antibodies and a hyperimmune serum prepared against the purified antigen showed the intranuclear fluorescence typical for BD virus-infected cells.

Borna disease virus. A possible etiologic factor in human affective disorders?

Borna disease virus is a unique neurotropic agent that appears to have a predilection for the limbic area of the brain. In some animal species, it can produce a behavioral syndrome characterized by aggressive and passive phases. This syndrome has suggested an analogy to certain human affective disorders. In this preliminary study, we examined the possible involvement of Borna disease virus in the etiology of human mood disorders by assaying for virus-specific antibodies in 265 patients with unipolar or bipolar depression and 105 normal, healthy volunteers. Twelve patients (4.5%) and none of the healthy controls demonstrated this antibody in their serum samples. It will be necessary to replicate and extend these intriguing preliminary results to determine if Borna disease virus is possibly involved in the pathogenesis of affective disorders in humans.

Detection of serum antibodies to Borna disease virus in patients with psychiatric disorders

Borna disease virus causes a rare meningoencephalitis in horses and sheep and has been shown to produce behavioral effects in some species. The possibility that the Borna virus is associated with mental disorders in humans was evaluated by examining serum samples from 979 psychiatric patients and 200 normal volunteers for the presence of Borna virus-specific antibodies. Antibodies were detected by the indirect immunofluorescence focus assay. Antibodies to the virus were demonstrated in 16 of the patients but none of the normal volunteers. The patients with the positive serum samples were characterized by having histories of affective disorders, particularly of a cyclic nature. Further studies are needed to define the possible involvement of Borna virus in human psychiatric disturbances.

Rocket line immunoelectrophoresis: an improved assay for simultaneous quantification of a mink parvovirus (Aleutian disease virus) antigen and antibody

A rocket line immunoelectrophoretic assay (RLIE) was developed for the simultaneous quantification of viral antigens and antiviral antibodies of the important mink parvovirus, Aleutian disease virus (ADV). The sensitivity of the RLIE assay was found to be 5 log2 higher than that of the counter current immunoelectrophoresis which is the assay routinely used for diagnostic purposes.

Enteric viral infections of calves and passive immunity

At least eight viruses have been identified, four within the last 5 yr, that produce diarrhea and pathological intestinal lesions in experimentally inoculated calves. Coronavirus and rotavirus frequently are associated with the neonatal calf diarrhea syndrome, but the etiologic role of the newly identified viruses is undefined. All diarrheal viruses replicate within small intestinal epithelial cells, resulting in variable degrees of villous atrophy. Immunity against these viral infections, therefore, must be directed toward protection of the susceptible intestinal epithelial cells. Because most of these viral infections occur in calves less than 3 wk of age, passive lactogenic immunity within the gut lumen plays an important role in protection. This report reviews methods of boosting rotavirus antibody responses in bovine mammary secretions and analyses of passive and active immunity in calves supplemented with colostrum and challenged by rotavirus. Results indicate rotavirus immunoglobulin G1 antibodies in colostrum and milk were elevated after intramuscular and intramammary vaccination of pregnant cows with an Ohio Agricultural Research and Development Center rotavirus vaccine but not after intramuscular immunization with a commercial rota-coronavirus vaccine. Feeding colostrum from intramuscular plus intramammary immunized cows to newborn calves challenged by rotavirus prevented diarrhea and shedding of rotavirus.

Examination of Aleutian disease virus in charge-shift crossed immunoelectrophoresis

The surface properties of Aleutian disease virus were studied by charge-shift crossed immunoelectrophoresis. When different strains of Aleutian disease virus were treated with non-charged detergent followed by charged detergents, they showed bi-directional migration velocity shifts in electrophoresis, indicating amphiphilic surface properties of the virus.

Analysis of the quantity of antiviral antibodies from mink infected with different Aleutian disease virus strains

Mink persistently infected with Aleutian disease virus (ADV) develop hypergammaglobulinaemia and immune complex disease. Radiolabelled antibodies from mink infected with ADV-G, DK, Pullman , and Utah I strains of ADV were reacted against all four ADV strains in radioimmunoassay (RIA). The amount of anti-ADV antibody in two equally hypergammaglobulinaemic serum pools varied from 13% (anti- Pullman ) to 57% (anti-Utah I). Serum pools from two other sources (anti-DK and anti-ADV-G), although less hypergammaglobulinaemic , had 5% and 13%, respectively, indicating that 43-95% of the Ig in the sera of mink with AD was not specific antibody to ADV structural antigens. The possibility of a general polyclonal activation of the humoral immune system is being discussed. Comparison of plateau RIA binding levels for the four serum pools against the four viral antigens suggested three patterns of reactivity: DK and Utah I reacted similarly, but Pullman and ADV-G reacted serologically different.

Mink with Aleutian disease have high-affinity antiviral antibodies

Mink persistently infected with Aleutian disease virus (ADV) develop plasmacytosis (hypergammaglobulinaemia) and immune complex disease. Mink of different colour phases were infected with different strains of ADV and bled at different times after infection. The average antibody affinities (Kav) were measured in the sera and found to fall in the range of 2 X 10(9) - 2 X 10(10) M-1, thus indicating good-quality antibodies. In sera of non-Aleutian genotype mink a decline in Kav during development of plasmacytosis was observed. Moreover, the antibody heterogeneity (alpha values) tended to decrease during the disease progress. In contrast, the Kav values in sera of infected Aleutian genotype mink remained relatively high after hypergammaglobulinaemia developed, and the antibody heterogeneity for certain of the mink sera indicated restricted heterogeneity (high alpha values). In agreement with the clonal selection theory, low virus burden (for instance, during infection with a low-virulence ADV strain) generated relatively higher affinity antibodies than a high virus burden for instance, the highly virulent Utah I strain of ADV). Furthermore, antibodies present in low concentration were of higher affinity than antibodies present in high concentrations. The relatively high affinity antibodies found in this study indicate that if the immune complex disease seen in AD is caused by virus-anti-virus antibodies, good-quality antibodies are likely to be responsible for the pathological findings.

Immune complexes in Aleutian disease: demonstration of antibody on isolated virus

The specific binding of Staphylococcal protein A for mammalian immunoglobulin G was used to demonstrate IgG associated with Aleutian disease virus (ADV) when isolated from infected mink tissues. Protein A specifically bound to mink serum Ig with no reaction with other serum or tissue proteins. Protein A labeled with 131Iodine reacted with crude virus preparations but not with virus that had been purified by freon extraction to the point where it became reactive with antibody by counterimmunoelectrophoresis. Binding to purified ADV was restored when the purified virus was first reacted with antibody. Results of urea treatment indicated this as an alternative method for isolation of ADV free from antibody.

Serological analyses of different mink Aleutian disease virus strains

Four different isolates of Aleutian disease virus have been compared electrophoretically and serologically. These were the DK and Utah 1 isolates, known as highly virulent strains, the Pullman isolate, known as a low virulent strain and the avirulent ADV-G isolate, which is the only strain grown in cell culture. ADV-G was shown to migrate in agarose electrophoresis 22 per cent slower than the other strains. Several murine monoclonal antibodies were prepared against each of the isolates. Each one reacted with all 4 of the isolates, but a few showed higher affinity for some of the isolates. Competitive RIA analyses were also performed, and these studies indicated some serological differences between the 4 strains. It is concluded that ADV-G polypeptides are chemically different but immunologically cross-reacting with the polypeptides present on the field ADV strains. It is suggested that the small serological differences seen between the field strains might be caused by slightly different in vivo proteolytic degradation of the viral capsid proteins and thus might not be taken as an indication of strain variation.

Immunoglobulin classes of Aleutian disease virus antibody

Aleutian disease virus (ADV) persistently infects mink and causes marked hypergammaglobulinemia. Immunoglobulin class-specific antisera were used to define the total immunoglobulin of each class by radial immunodiffusion and the immunoglobulin class of ADV-specific antibody by immunofluorescence in experimentally and naturally infected mink. Electrophoretic gamma globulin closely reflects the immunoglobulin G (IgG) level in mink, and the majority of the increased immunoglobulin and ADV antibody in infected mink is IgG. IgM becomes elevated within 6 days after infection, reaches peak levels by 15 to 18 days, and returns to normal by 60 days after infection. The first ADV antibody demonstrable is IgM, and most mink have virus-specific IgM antibody for at least 85 days postinfection. Serum IgA levels in normal mink are not normally distributed, and ADV infection causes a marked elevation of IgA. Low levels of ADV-specific IgA antibody can be shown throughout the course of infection. Failure of large amounts of virus-specific IgG antibody to inhibit the reaction of virus-specific IgM and IgA antibodies suggests that the various classes of antibodies are directed against spatially different antigenic determinants. The IgM and IgA were shown not to be rheumatoid factors.

Borna disease of horses. An immunohistological and virological study of naturally infected animals

The brains of eight horses that had suffered from natural Borna disease were examined with virologic, immunohistological, and electron-microscopic methods. All brains harbored infectious virus as shown by inoculation of experimental animals. Regional assessment of the infectivity exhibited the highest titers in the hippocampus and piriform cortex and the lowest in the cerebellum. Conventional histology yielded pathologic alterations very similar to those of the classical description of the disease. Immunohistology demonstrated the highest amounts of Borna disease virus-specific antigen in the nuclei of neurons. In the perikarya, dendrites, and axons smaller amounts of antigen were found. A comparison of the antigen distribution with the inflammatory reaction established a high concordance of these two parameters. The presence of virus-specific antigen seems to trigger the exsudation of inflammatory cells, which reflect the extension of the infectious process. Heavy inflammatory exsudates in the white matter underlying diseased cortical areas can be explained by the axonal presence of virus-specific antigen. Virus particles could not be demonstrated with the electron microscope. The most significant findings at the ultrastructural level were stacks of fine filaments, adhering closely to cytoplasmic cisterns. These structures might be related to virus components or might be involved in virus morphogenesis.

Sensitive radioimmune assay for measuring Aleutian disease virus antigen and antibody

A solid-phase, one-step radioimmune assay was developed which could detect as little as 0.02 microliter of a standard Aleutian disease virus antigen preparation, approximately 3.2 ng of viral protein. Virus antigen was measured in different mink organs and cell types during experimental intraperitoneal infection. The gut and kidney were the first organs in which virus antigen could be detected (day 3 to 6 after infection). On day 6 or later virus antigen was found in spleen, liver, kidney, lymph nodes, peritoneal exudate, and bone marrow cells. With inhibition of antigen binding, a radioimmune assay was developed for antibody detection. Viral antibodies could be detected as early as 3 days after infection. Antibody titers from 1/10(5) to more than 1/10(6) were found in plasmacytotic mink. When the sensitivity of the antibody radioimmune assay was compared with that of other known methods for anti-Aleutian disease virus quantitation, the radioimmune assay was considerably more sensitive, detecting as little as 5 ng of antibody.

Autoimmunity in Aleutian disease: contribution of antiviral and anti-DNA antibody to hypergammaglobulinemia

The contributions to Aleutian disease gammopathy of specific antiviral antibody and an autoimmune component, anti-DNA antibody, were studied with pastel ranch mink naturally infected with Aleutian disease virus. Specific antibody activities were determined by countercurrent immunoelectrophoresis and radioimmune assay, respectively. Gamma globulin levels (percent gamma) were determined by serum electrophoresis. Within an infected mink population, it was possible to predict the level of gammopathy from measurement of the two antibody levels. For the mink serum samples used, there was better correlation between anti-DNA antibody levels and total serum immunoglobulin than between anti-Aleutian disease virus antibody titers and percent gamma. With serum samples taken over a 2-week interval, significant increases were measured in anti-DNA antibody and percent gamma. Increases in anti-Aleutian disease virus titers during this period were not significant. The results suggest that the continuing increases in serum immunoglobulin in Aleutian disease virus-infected mink are due to both a specific antiviral response and an autoimmune response, as reflected in generation of anti-DNA antibody.

Isolation of virus and antibody containing immune complexes from mink with Aleutian disease by affinity chromatography of equine complement clq

Affinity chromatography on immobilized equine complement Clq was used for the isolation of complement-binding immune complexes in sera of mink infected with Aleutian disease virus. Immune complexes were isolated and quantitated from 4 of 5 infected mink, as early as 2 weeks after infection and before hypergammaglobulinemia had appeared. The quantity of immunoglobulin G in these immune complexes ranged from 180 to 370 micrograms/ml serum. There were no Clq-binding immune complexes found in mink which were negative for Aleutian disease antibody. Using 125I-labeled BSA-anti-BSA complexes, we demonstrated that the affinity columns bound selectively immune complexes which had formed in antibody excess, whereas immune complexes in antigen excess were not bound. By neutralization of sensitized virus with anti-mink IgG serum, non Clq-binding immune complexes were also detected, which indicates that circulating immune complexes in persistently infected mink are heterogeneous as far as their reactivity with equine Clq is concerned.

Pleural effusion disease in rabbits. Properties of the aetiological agent

The size and heat sensitivity of Pleural effusion disease (PED) agent or virus (PEDV) propagated in rabbits were examined. The infectious particles were estimated to be between 25 and 50 nm by filtration. Residual infectivity of infectious serum was 0.1 per cent after heating at 56 degrees C for 4 hours. PEDV and the Stockholm agent appeared identical concerning pathogenic and immunogenic properties by infection experiments and protection tests in rabbits. Two of the three PEDV isolates were less pathogenic but appeared immunogenically identical to PEDV. The third isolate, obtained from the laboratory, which several years previously had supplied material for demonstration of the Stockholm agent, differed from PEDV in pathogenic and immunogenic properties. Serological examinations of paired rabbit sera did not indicate any antigenic relationship between PEDV and representative members of the two mammalian coronavirus antigenic groups. It is concluded that the aetiological agent of PED is a virus not belonging to the coronaviridae.

Mitogen- and viral antigen-induced transformation of lymphocytes from normal mink and from mink with progressive or nonprogressive Aleutian disease

Peripheral blood lymphocytes (PBL) from mink with progressive Aleutian disease (AD) were shown to be significantly less responsive to phytohemagglutinin, concanavalin A, and pokeweed mitogen than were PBL from normal mink and from mink with a nonprogressive form of AD. Response to the virus of AD was significantly greater in PBL cultures from mink with nonprogressive AD than in those from normal mink or mink with progressive AD. After experimental infection with AD virus, mink PBL were responsive to viral antigen only transiently. These findings suggest that lymphocyte responsiveness as indicated by transformation induced by mitogens or viral antigen may be an important aspect of host response to infection with the parvovirus of AD.

Norwalk virus gastroenteritis in volunteers consuming depurated oysters

Following the widespread outbreaks of oyster-associated gastroenteritis which occurred throughout Australia in 1978, several programmes were introduced to minimise the occurrence of further outbreaks. One programme included the depuration (purification) of oysters and the use of human volunteers to test-consume samples from batches of depurated oysters before their sale to the public. Oysters from the Georges River and Brisbane Waters were test-consumed from December, 1978, to August, 1979. None of the volunteers was ill after consuming Brisbane Waters oysters but 52 reported ill after eating Georges River oysters. The predominant symptoms were nausea, vomiting and diarrhoea with an average incubation period of 42 hours. Recovery was usually complete in 36-48 hours. Of the 52 illnesses reported 31 (60%) occurred in two particular weeks ending July 1st and 22nd when rates of 18.3% and 7.8% were reported. The average illness rate for the remainder of the period under study was only 1%. Norwalk virus was found in 8 of 25 (32%) stools, and antibody increases demonstrated in seven of ten paired sera, giving an overall diagnostic rate for Norwalk infection of 37.0% for these two peak periods. Heavy rain preceded these two weeks in which the illnesses occurred. No evidence of Norwalk infection was found at any other time. These studies confirmed the epidemiological findings of the major outbreak of gastroenteritis in 1978, and showed that only Georges River oysters caused Norwalk virus infections and that depuration as carried out in 1979 was not entirely satisfactory.

The 33- to 39-nm virus-like particles, tentatively designed as Sapporo agent, associated with an outbreak of acute gastroenteritis

An outbreak of nonbacterial gastroenteritis occurred in an orphanage in December 1979. Of 54 residents, 43 were affected with acute gastroenteritis. Diarrhea was the commonest symptom. The 33- to 39-nm virus-like particles, tentatively designated as Sapporo agent, were detected in 17 (48.6%) of the patients' 35 fecal specimens. Morphologically, it was difficult to distinguish the Sapporo agent from other agents without geometrical pattern of the surface. Antigenically, the Sapporo agent related to the Otofuke agent detected in an outbreak of the institution for mentally retarded adults and also to the SRV ;76 detected in familial cases of infectious gastroenteritis. The Sapporo agent might belong to a new group of those gastroenteritis viruses which were larger in size than the Norwalk virus group.

Oyster-associated gastroenteritis in Australia: the detection of Norwalk virus and its antibody by immune electron microscopy and radioimmunoassay

Following widespread outbreaks of oyster-associated gastroenteritis in Australia during 1978 in which Norwalk virus was implicated as the causative agent, collaborative studies were undertaken between laboratories in Australia and the United States to confirm the etiology. Immune electron microscopy (IEM) techniques were used in Australia and radioimmunoassay (RIA) methods in the United States. Norwalk virus was detected by IEM in seven of 15 faecal samples, and four were positive by RIA. A much better correlation was found with antibody determinations. Both methods demonstrated significant increases in antibody to Norwalk virus in 22 of 30 sets (73%) of "acute" and "convalescent" sera, confirming that Norwalk virus was responsible for the majority of cases. It is significant that the RIA serology was determined using Norwalk antigen originating in the United States and the IEM serology was determined using 27--30-nm particles originating in Australia.

Immune response and prevalence of antibody to Norwalk enteritis virus as determined by radioimmunoassay

A solid-phase microtiter radioimmunoassay was established for the detection of Norwalk virus and its antibody, with clinical materials from human volunteers previously studied in Massachusetts as reagents. A study of 308 Massachusetts residents showed that serum antibody to Norwalk agent was rarely present during childhood but was detectable in approximately 50% of adults. All volunteers inoculated with Norwalk virus who developed illness seroconverted (10/10), whereas only one-third (5/15) of nonill volunteers seroconverted (P = 0.0009). The 10 nonill, nonseroconverting subjects had undetectable to low preexisting antibody levels. Paradoxically, 10/13 subjects with preexisting antibody became ill, whereas 17/25 lacking antibody did not (P = 0.009). All 3 subjects with preexisting anti-Norwalk radioimmunoassay blocking activity in duodenal intraluminal fluids became ill, whereas only 5/11 lacking such activity developed illness (P = 0.15). These data further support the unique concept that some individuals are susceptible to repeated infections with this agent, whereas others are incapable of developing infection.

Prevalence of antibody to the Norwalk virus in various countries

Serum samples from children and adults from several countries were tested by radioimmunoassay for antibody to the Norwalk virus. Antibody was commonly found in adults from all the countries tested. Antibody appears to be acquired more rapidly in children from underdeveloped countries than in children from the United States.

Biophysical properties of a non-cultivable 29-nm enteric virus

A 29 nm non-cultivable virus (NCV) was detected in faecal extracts from children hospitalized for gastroenteritis. The NCV had a density of 1.35 g/ml in glycerol-potassium tartrate density gradients and was resistant to degradation by proteolytic enzymes, non-ionic detergents and pH extremes. The surface of these virus particles had knob-like projections which appeared to have a symmetrical arrangement. When heated to 56 degrees C, the virus was completely degraded to soluble components which could not be seen by electron microscopy.

Antibodies to viral gastroenteritis viruses in Crohn's disease

Antibody prevalence and titer to rotavirus and Norwalk virus were studied in Crohn's disease patients and in age-, sex-, and time-matched controls. There were no significant antibody differences between the groups studied.

Isolation of a virus strain from Argas persicus ticks

A previously undescribed virus was isolated from Argas persicus ticks collected on sentinel chicken in western Slovakia. The strain was lethal for suckling mice only after intracerebral inoculation. No symptoms were induced in adult mice. The virus strain was insensitive to sodium deoxycholate and resistant to ether treatment. An antigen prepared from the virus did not agglutinate goose or human O erythrocytes. The single strain obtained in 1976 appeared to be untrelated to a large number of known arboviruses when tested by the complement-fixation reaction.

Astrovirus gastroenteritis age distribution of antibody

Astrovirus antibody was detected by immunofluorescence using infected primary human embryo kidney cultures as antigen. Of 87 Oxford children aged 0--10 years, only 7% in the 6 to 12-month-old group had antibody. The percentage of children having evidence of past infection rose progressively in the 1--4 age range and 75% of the 5 to 10-year-old group possessed astrovirus antibody. Fifty-four (77%) of a group of 70 young adults likewise had antibody.

Norwalk agent-like particles associated with gastroenteritis in human beings

Currently, 6 agents of viral gastroenteritis with properties similar to the Norwalk agent have been described. These are the Hawaii, Montgomery County, W, Ditchling, and Cockle agents, as well as the Norwalk agent. These agents are 25 to 27 nm in diameter, are nonenveloped, and have a buoyant density of 1.38 to 1.40 g/cc in CsCl. Multiple antigenic types exist among these agents. These particles have been detected by immune electron microscopy in feces of acutely ill patients. None has been successfully cultivated in vitro, and suitable animal models of disease do not exist. Studies in volunteers indicate that acute infection is associated with a reversible histopathologic change in the jejunal mucosa and with transient malabsorption. Pathogenesis of these changes remains unknown. Other similar agents will likely emerge from ongoing studies.