Epizootic Diarrhea Of Infant Mice Research Articles

Highly sensitive ELISA for the serological detection of murine rotavirus EDIM based on its major immunogen VP6

Precise health monitoring of laboratory animals is a critical factor for surveillance and accuracy of animal experiments. Rotavirus epizootic diarrhea of infant mice (EDIM) leads to infections in mice that can influence animal studies, e.g., by altering the intestinal physiology. Thus, the aim of this study was establishing a highly sensitive and specific ELISA for the serological detection of EDIM infections in rodents. First, virus proteins were separated by SDS-PAGE and immunogenic proteins were visualized by immunoblotting and identified after in-gel digestion by tandem mass spectrometry. Subsequently, the major immunogen VP6 (virus protein 6) was expressed in Escherichia coli in high yields, purified by affinity chromatography, and used to establish an indirect ELISA. The diagnostic sensitivity and specificity were both above 99 % and the selectivity better than 98.7 % for animals infected by other pathogens listed by the Federation of Laboratory Animal Science Associations. Importantly, the Strep-rVP6-His-ELISA was more sensitive than a commercial virus-based ELISA and is a time- and cost-efficient complement to EDIM-specific immune-fluorescence assays. In conclusion, the assay can improve health monitoring by reducing the risk of missed EDIM infections in animal housing facilities, thereby improving animal welfare, reliability of animal studies, and protection of precious mice breeds.

Enhancement of VP6 immunogenicity and protective efficacy against rotavirus by VP2 in a genetic immunization

VP2/VP6 virus like particles (VLPs) are very effective in inducing protection against the rotavirus infection in animal models. Individually, VP6 can also induce protection. However, there is no information about the immunogenicity of VP2. The aim of this work was to evaluate the efficacy of DNA vaccines codifying for VP2 or VP6, alone or combined, to induce protection against the rotavirus infection. Murine rotavirus VP2 and VP6 genes were cloned into the pcDNA3 vector. Adult BALB/c mice were inoculated three times by intramuscular (i.m.) injections with 100 or 200µg of pcDNA3-VP2 or pcDNA3-VP6 alone or co-administered with 100µg of pcDNA3-VP2/100µg of pcDNA3-VP6. Two weeks after the last inoculation, mice were challenged with the wild type murine rotavirus strain epizootic diarrhea of infant mice (EDIMwt). We found that both plasmids, pcDNA3-VP2 and pcDNA3-VP6, were able to induce rotavirus-specific serum antibodies, but not intestinal rotavirus-specific IgA; only 200µg of pcDNA3-VP6 induced 35% protection against the infection. A similar level of protection was found when mice were co-administered with 100µg of pcDNA3-VP2/100µg of pcDNA3-VP6 (1:1 ratio). However, the best protection (up to 58%) occurred when mice were inoculated with 10µg of pcDNA3-VP2/100µg of pcDNA3-VP6 (1:10 ratio). These results indicate that the DNA plasmid expressing VP6 is a better vaccine candidate that the one expressing VP2. However, when co-expressed, VP2 potentiates the immunogenicity and protective efficacy of VP6.

Evaluation of oral Lanzhou lamb rotavirus vaccine via passive transfusion with CD4+/CD8+ T lymphocytes

Lanzhou Lamb derived Rotavirus (RV) Vaccine (namely LLR) for children is only used in China. Since there were no reports on evaluation of LLR, even the data of phase IV clinical trial, we proceed the evaluation of LLR through focusing on T-cell to investigate whether LLR could induce the potential function involving in protection as a vaccine. Four groups of nude mice were transfused with CD4+/CD8+ T-cells isolated from LLR-immunized (primed) and LLR-unimmunized (naïve) mice via intraperitonea (i.p.) respectively. Consequently, the adoption mice were challenged with mice-origin wild rotavirus EDIM (Epizootic Diarrhea of Infant Mice) by intragastric administration. Series of fecal/serum samples were collected and viral shedding, then serum IgA/IgG and secreted IgA were assayed. Compared to the mice transfused with T lymphocytes from naïve mice, the nude mice transfused with CD4+ T lymphocytes from primed mice induce fecal and serum IgA increasing more rapidly, and have a shorter duration of virus shedding too. Whereas, no significant difference in virus clearance was found between the mice transfused with CD8+ T lymphocytes isolated from primed and naïve mice. Therefore, we cleared the distinct roles of transfused CD4+/CD8+ T lymphocytes for rotavirus clearance in nude mice, that the viral clearance conducted by CD4+ T lymphocytes. Meanwhile, it has ability to help induction of LLR specific immunogenicity. Comparing with the transfusion of cell from primed and naïve mice, LLR can induce CD4+ T lymphocytes memory which is a potential index to reflect the immunogenicity and protection, while CD8+ T lymphocytes remove rotavirus by CTL with little memory ability.

Shutting down a working vivarium for decontamination.

Handling a rodent disease outbreak in a facility can be a challenge. After the University of Colorado Denver Office of Laboratory Animal Resources enhanced its sentinel monitoring program, > 90% of the animal colonies housed in a vivarium at the Anschutz Medical Campus (with an area of 50,000 net ft(2)), serving the labs of > 250 principal investigators, tested positive for multiple infective agents including mouse parvovirus, fur mites, pinworms and epizootic diarrhea of infant mice. The authors detail the process by which they planned and executed a shutdown and a decontamination of the facility, which involved the rederivation or cryopreservation of > 400 unique genetically modified mouse lines. The authors discuss the aspects of the project that were successful as well as those that could have been improved.

Sudden onset of mortality within a colony of FVB/n mice

An investigator at Colorado State University received five breeding pairs of FVB/n mice less than 23 days old from a commercial vendor. We housed the mice in a semibarrier animal room in microisolator cages on a 12-h light/dark cycle and gave them ad libitum access to water and rodent chow (Harlan Teklad 8640, Madison, WI). Serologic evaluations of two sentinel ICR mice caged in the same room were negative for serum antibodies reacting with mouse hepatitis virus (MHV), minute virus of mice (MVM), Sendai virus, mouse parvovirus (MPV), Mycoplasma pulmonis, Theiler’s murine encephalomyelitis virus (TMEV), and epizootic diarrhea of infant mice (EDIM) antigens. One mouse tested negative for all of the aforementioned except for MPV. The five pairs of FVB/n mice were therefore moved to a different MPV-positive semi-barrier room that also housed immunocompromised strains of mice. Three of the five females subsequently gave birth to 37 FVB/n offspring (17 males and 20 females) over a four-day period. Animal care technicians weaned the pups at 21 days old. Four weeks later, they noticed wounds on the tails and tail bases of 7week-old female FVB/n mice in two cages. One of us (M.D.R.) diagnosed conspecific aggression as the likely etiology and separated the animals in an attempt to alleviate the intracage aggression. We did not note any other abnormalities in the FVB/n mice or in any of the other mice housed in the same room. Approximately 5 weeks later (when the mice were 12 weeks old), we found a dead female FVB/n mouse with no premonitory symptoms. M.D.R. performed a complete necropsy; no gross lesions were noted. Over the next 4 weeks, animal care technicians found an additional 16 mice (1 male, 15 female) dead in their cages, again without any premonitory symptoms. We took blood from one of the remaining five female mice and submitted serum for a serology panel that tested for antibodies to ectromelia virus, EDIM, lymphocytic choriomeningitis virus (LCM), M. pulmonis, MHV, MNV, Parvo NS-1, MPV, MVM, pneumonia virus of mice (PVM), RE03, Sendai, and TMEV-GDII; all test results were negative. M.D.R. performed necropsies on 10 of the mice that had previously been found dead (9 female, 1 male). All mice were considered in good body condition, with a score of >3 out of 5 (ref. 1). The mice had adequate body fat stores and food within the stomach; the small and large intestines contained normal amounts of ingesta and feces. All mice appeared normally hydrated. We noted occasional superficial excoriations of the dermis on the dorsum of the tail base. Additionally, all the mice had wet fur below the mandible and on the ventrum of the neck. We performed histopathologic examinations on all major organs (brain, liver, heart, lungs, stomach, spleen, lymph nodes, salivary glands, small intestine, colon, kidney, adrenals, bladder, and gonads) from four mice that were necropsied. Brain sections of all mice had multifocal areas of neuronal necrosis and neuronal depletion in the cerebral cortex (Fig. 1). We also detected astrocytosis and early gliosis in the brain of one of two affected mice that were labeled with an antibody that recognizes glial fibrillary acidic protein (GFAP), a cell marker for neuroglia. Are these brain lesions of neuronal necrosis and loss common among FVB/n mice? Does the case history and epidemiology point to a syndrome associated with this strain?

Pathogens of house mice on arid Boullanger Island and subantarctic Macquarie Island, Australia.

Studies on island populations of house mice (Mus domesticus) and their viruses reveal insights into viral persistence in isolated communities. We surveyed the ectoparasites, endoparasites, and antiviral antibodies for 11 murine viruses and two bacteria of house mice inhabiting two islands off Australia. House mice on Boullanger Island were seropositive to two viruses, murine cytomegalovirus and epizootic diarrhea of infant mice. On subantarctic Macquarie Island, house mice were seropositive for five viruses: murine cytomegalovirus, lymphocytic choriomeningitis virus, mouse parvovirus, epizootic diarrhea of infant mice, and Theiler's murine encephalomyelitis virus. The diversity of antiviral antibodies was lower among populations of house mice on islands than those inhabiting mainland Australia. The decreased diversity of viruses in island populations of house mice may be a function of which agent the founder mice transfer to the island and related to the low densities which the host population may periodically reach over time.

The level of protection against rotavirus shedding in mice following immunization with a chimeric VP6 protein is dependent on the route and the coadministered adjuvant

Intranasal (i.n.) immunization of BALB/c mice with chimeric murine rotavirus EDIM (epizootic diarrhea of infant mice) VP6 and attenuated E. coli heat-labile toxin (LT), LT(R192G), stimulated >99% protection against rotavirus shedding after EDIM challenge. Here, we evaluated other potential adjuvants with chimeric VP6 administered by two mucosal routes: i.n. and oral. Besides LT(R192G), the adjuvants examined included Adjumer ®, CpG oligodeoxynucleotides (CpG ODN), chimeric A1 subunit of cholera toxin (CTA1)-DD, and QS-21. All except QS-21 significantly ( P<0.05) increased VP6-specific serum IgG responses after i.n. immunization, but none significantly increased these responses when administered orally. The i.n. delivery of chimeric VP6 alone induced both rotavirus IgG1 and IgG2a whose relative titers suggested a skewed Th2-like response. Inclusion of Adjumer ® greatly increased Th2-like responses, while CpG ODN shifted the response to a less Th2-like response. The adjuvants CTA1-DD, LT(R192G), QS-21 had no significant effect on ratios of IgG1/IgG2a titers. Following EDIM challenge of mice immunized i.n. with chimeric VP6 and either LT(R192G), CTA1-DD, Adjumer ® or CpG ODN, shedding was reduced >99, 95, 80, 74, respectively, relative to that found in unimmunized mice ( P<0.05). QS-21 induced less protection (43%, not significant (N.S.)) while immunization with chimeric VP6 alone reduced shedding by only 16% (N.S.). Oral immunization with chimeric VP6 and all selected adjuvants except QS-21 was less effective than after i.n. immunization, with protection levels of 94 ( P<0.05), 71 ( P<0.05), 55, 35 and 28% for LT(R192G), QS-21, CpG ODN, CTA1-DD, and Adjumer ®, respectively, while immunization with chimeric VP6 alone gave no protection. Thus, different adjuvants induced different degrees of protection and oral immunization was generally less effective then the i.n. route.

Murine experimental infection with rotavirus SA-11: clinical and immunohistological characteristics.

Six- to eight-day old (lactent) mice were inoculated orally with simian SA-11 rotavirus. During the first hours after infection, the virus was already detected in villous apical enterocytes by immunohistologic reaction of paraffin sections of the duodenum and jejunum but not in the ileum. Late on the first day, some animals developed already diarrhoea and pathologic lesions were observed in the duodenum and jejunum. During the second day most mice developed diarrhoea; tissue lesions were intense and maximal from duodenum to ileum when compared to other days and some colon sections had mild pathological characteristics. At this point, the virus in the ileum was only detected by immunohistologic reaction. During the third day some animals still had diarrhoea but tissue histology was regenerated and no virus could be detected. We conclude that the SA-11 model follows an infection pattern similar to Epizootic Diarrhoea of Infant Mice (EDIM) and propose to study immunological parameters as young susceptible animals mature into adult resistant ones.

Effect of vitamin A deficiency on the immune response to epizootic diarrhoea of infant mice (EDIM) rotavirus infection in mice.

The effect of vitamin A deficiency on the immune response to epizootic diarrhoea of infant mice (EDIM) rotavirus was studied in mice. The virus was given by oral dosing or by intraperitoneal injection. For oral challenge, weanling mice were fed on either a control or vitamin A-deficient diet ad lib. or pair-fed the control diet to the intake of the vitamin A-deficient group. A fourth group was fed on the vitamin A-deficient diet ad lib. for 10 weeks and then refed the control diet for 2 weeks. On day 77, mice were each given 30 microliters EDIM rotavirus orally and the animals were killed and examined 1 week later. The delayed-type hypersensitivity (DTH) response to picryl chloride was measured as an index of cell-mediated immunity. For intraperitoneal challenge, weanling mice were fed on either the control diet or the vitamin A-deficient diet ad lib. or pair-fed the control diet to the intake of the vitamin A-deficient group. On day 77, mice were each injected intraperitoneally with 30 microliters EDIM rotavirus and 1 week later antibody production was measured. In both experiments the body-weight, liver and serum vitamin A levels of the vitamin A-deficient group were significantly lower than the control or pair-fed groups. Following oral dosing the serum antibody levels specific to rotavirus were statistically significantly lower in vitamin A-deficient animals than the control or pair-fed groups. Vitamin A-deficient mice also showed an impaired DTH response compared with the control and pair-fed animals. Animals refed vitamin A for a short period showed a partial restoration of the antibody response. Following intraperitoneal challenge no statistically significant changes were observed in the serum antibody levels between any of the dietary groups. It is concluded that vitamin A deficiency impaired antibody production when rotavirus was given orally. Vitamin A deficiency also impaired cell-mediated immunity.

Effect of Severe Food Restriction on the Gut following Rotavirus Infection in Mice

The effect of severe food restriction on the histopathology of the gut following infection with epizootic diarrhoea of infant mice (EDIM) rotavirus was studied in mice. Over a period of 12 weeks, weanling mice were fed either 70 or 50% of the diet eaten by a control group on the previous day. After 11 weeks of feeding, animals were given 30 microliters/mouse of EDIM rotavirus orally and the histopathology of the gut and lymphoid organs examined. The histology of the spleen and thymus of different dietary groups appeared normal and no changes were observed due to the rotavirus challenge. Both the control and 70% food group had normal villi in the small intestine. In contrast there was severe atrophy of the villi in the animals whose intake was reduced by 50%. No additional damage to the villi was seen in association with the rotavirus infection. It is concluded that a prolonged, balanced reduction in food intake can itself cause villous atrophy in the gut but following rotavirus infection, adult animals were able to resist further villous damage.

Recovery from chronic rotavirus infection in mice with severe combined immunodeficiency: virus clearance mediated by adoptive transfer of immune CD8+ T lymphocytes

Severe combined immunodeficient (SCID) mice lack both functional T and B cells. These mice develop chronic rotavirus infection following an oral inoculation with the epizootic diarrhea of infant mice (EDIM) rotavirus. Reconstitution of rotavirus-infected SCID mice with T lymphocytes from immunocompetent mice allows an evaluation of a role of T-cell-mediated immunity in clearing chronic rotavirus infection. Complete rotavirus clearance was demonstrated in C.B-17/scid mice 7 to 9 days after the transfer of immune CD8+ splenic T lymphocytes from histocompatible BALB/c mice previously immunized intraperitoneally with the EDIM-w strain of murine rotavirus. The virus clearance mediated by T-cell transfer was restricted to H-2d-bearing T cells and occurred in the absence of rotavirus-specific antibody as determined by enzyme-linked immunosorbent assay, neutralization, immunohistochemistry, and radioimmunoprecipitation. Temporary clearance of rotavirus was observed after the transfer of immune CD8+ T cells isolated from the intestinal mucosa (intraepithelial lymphocytes [IELs]) or the spleens of BALB/c mice previously infected with EDIM by the oral route. Chronic virus shedding was transiently eliminated 7 to 11 days after spleen cell transfer and 11 to 12 days after IEL transfer. However, recurrence of rotavirus infection was detected 1 to 8 days later in all but one SCID recipient receiving cells from orally immunized donors. The viral clearance was mediated by IELs that were both Thy1+ and CD8+. These data demonstrated that the clearance of chronic rotavirus infection in SCID mice can be mediated by immune CD8+ T lymphocytes and that this clearance can occur in the absence of virus-specific antibodies.

X-Ray Microanalysis of Rotavirus-Infected Mouse Intestine

Neonatal mice were infected at 7 days of age with rotavirus [epizootic diarrhea of infant mice (EDIM) virus] and killed at 24-h intervals postinfection (PI). Cytoplasmic concentrations of Na, Mg, P, S, Cl, K, and Ca intestinal epithelial cells from infected and age-matched control animals were measured by x-ray microanalysis. In villus tip cells, Ca concentration increased at 24-96 h PI; Na concentration increased at 24-72 h PI; Ca and Na concentrations were near normal by 168 h PI. K concentration decreased 24-72 h PI, and Cl concentration decreased 48-96 h PI. In crypt cells, changes were observed without a discernible pattern: at 96 h PI, Na, Mg, S, and Cl concentrations increased and K concentration decreased; at 120 h PI, the concentrations of all elements except Na and Ca increased. In villus base cells, the mean concentrations of all elements except Ca peaked at 48-72 h PI and at 120 h PI. Na and Cl concentrations increased dramatically in some cells from 48 h PI onward. All the above concentration values were obtained from freeze-dried specimens and expressed in millimoles per kilogram of dry weight. Conversion of a limited number of data, pertaining to villus base cells, from dry weight to wet weight was possible. This conversion revealed that villus base cells in infected animals were more hydrated than corresponding cells from control animals. Also, the Na and Cl concentrations in mmol/kg H2O were significantly higher in villus base cells from infected animals than in those from corresponding controls: 137 +/- 7 versus 38 +/- 4 (Na) and 121 +/- 5 versus 89 +/- 6 (Cl). Wet weight concentrations of other elements were either the same (Mg) or lower (P, S, and K) after infection with virus. From these studies, a new concept of the pathophysiology of rotavirus-induced diarrhoeal secretion is proposed: stimulation of villus base cells to rapid cell division is accompanied by transient accumulation of Na and Cl; excess NaCl is secreted into the lumen, which is the driving force for fluid loss.

Natural Epizootic Diarrhea of Infant Mice (EDIM) a light and electron microscope study

Epizootic diarrhea of infant mice (EDIM), studied under natural conditions, reveals a typical histopathological picture given by the vacuolation of the enterocytes of duodenojejunal villi, which often involves the entire length of the villi, sparing the crypts. The lamina propria is edematous and its vessels are dilated. Half micron plastic embedded methylene blue azur II stained sections showed intracytoplasmic paranuclear inclusions in the enterocytes. With the electron microscope great numbers of 70 nm viruses are first observed close to the Golgi region. Viruses are also seen within the rough endoplasmic reticulum. Tubular structures are seen in the nucleus and the cytoplasm. They are interpreted as irregular capsids which undergo fragmentation and surround nucleoids. Viruses are released into the intestinal lumen through cell desquamation and by passing through the apical cytoplasm without any relationship with the cell membrane, thus being easily detected in feces with negative staining techniques. Viral crystals were also found within argentaffin cells. EDIM is a good natural model for the study of rotaviruses, common etiological agents of diarrhea in young mammals, including man.

A method for the serological diagnosis of epizootic diarrhoea of infant mice

A method for the serological diagnosis of epizootic diarrhoea of infant mice

Antigenic relationships among five reovirus-like (RVL) agents by complement fixation (CF) and development of new substitute CF antigens for the human RVL agent of infantile gastroenteritis.

The human reovirus-like (HRVL) agent, Nebraska calf diarrhea virus (NCDV), epizootic diarrhea of infant mice (EDIM) virus, simian agent (SA)-11, and the "O" (offal) agent were found to be similar, if not identical, in reciprocal complement fixation (CF) tests employing hyperimmune animal sera. In addition, in CF tests with paired sera from 35 diarrhea patients who shed the HRVL agent, 74% developed serologic evidence of infection with the HRVL antigen, 43% with NCDV, 51% with EDIM virus, 57% with SA-11, and 71% with the "O" agent. Thus, in addition to the NCDV, which had previously been described as a suitable substitute CF antigen for the HRVL agent, the SA-11, "O", and EDIM viruses may also be utilized as substitute antigens for the HRVL agent. However, the "O" agent appears to be the most efficient of the four substitute CF antigens and thus should be used preferentially when the HRVL agent is not available. The "O" agent was about as efficient as the HRVL agent and significantly more efficient than the NCDV for detecting seroresponses. The greatest efficiency for detecting infection with the HRVL agent resulted when sera were tested with both the HRVL and "O" agents as 31 (89%) of the patients developed serologic evidence of infection with one or both antigens. The finding of additional substitute CF antigens for the HRVL agent may have implications in the immunoprophylaxis against human disease.

Morphological and antigenic relationships between viruses (rotaviruses) from acute gastroenteritis of children, calves, piglets, mice, and foals

The reovirus-like particles present in the feces of young pigs and foals with acute enteritis and the virus causing epizootic diarrhea of infant mice were found to be indistinguishable morphologically from each other, from the South African SA. 11 and "O" viruses, and from the rotaviruses of children and calves. The inner capsid layer of each of these viruses reacted seriologically with sera of children, calves, mice, piglets, and foals convalescent from infection with their respective rotaviruses. These sera reacted by immunofluorescence with human, bovine, porcine, and murine rotaviruses, SA.11, and "O" viruses in tissue cultures and with human bovine, procine, nad murine viral antigens by complement fixation and gel diffusion. However, the antisera differed in their ability to react serologically with the outer capsid layer of the viruses investigated and in their ability to neutralize tissue culture-adapted calf virus. These two tests may demonstrate strain or host specificity among rotaviruses. Since the porcine, murine, and equine viruses are closely related serologically to and are morphologically identical to the human and bovine viruses, they should be included in the group of viruses for which the term "rotavirus" has been suggested. All known members of this proposed group of viruses share a common antigen, probably situated within the inner capsid layer; thus, any one of the viruses may be used for the preparation of antigen or antibody for diagnostic tests, and this will aid in the diagnosis of virus infection in those species from which a rotavirus has not been cultured.

Infantile enteritis viruses: morphogenesis and morphology.

A new virus was found to be associated with acute gastroenteritis in children. In duodenal biopsies, it was observed infecting only intestinal epithelial cells, and it resembled orbiviruses in its morphogenesis. For diagnsotic purposes the virus was readily demonstrated by negative staining of fecal extracts. Two forms of particles were seen: double-sheeled particles (70 to 75 nm in diameter) resembling those of reovirus with a sharper outline, and single-shelled particles (60 nm in diameter) with obvious capsomer structure and resembling those of orbiviruses. The morphological resemblance of this human virus to the viruses of "Nebraska" calf scours and epizootic diarrhoea of infant mice is emphasized.

NEW COMPLEMENT-FIXATION TEST FOR THE HUMAN REOVIRUS-LIKE AGENT OF INFANTILE GASTROENTERITIS: Nebraska Calf Diarrhœa Virus Used as Antigen

A complement-fixation (C.F.) test for the human reovirus-like agent of infantile gastroenteritis has been developed using the serologically related Nebraska calf diarrhœa virus (N.C.D.V.) as antigen. Most infants and children who shed the agent in stools and/or who demonstrated serological (C.F.) evidence of infection with a reovirus-like- particle-positive human stool-filtrate C.F. antigen also demonstrated serological evidence of infection when a concentrated N.C.D.V. preparation was employed as C.F. antigen. The N.C.D.V., which was previously shown to be related to the human reovirus-like agent, was found to be related antigenically to the epizootic diarrhoea of infant mice (E.D.I.M.) virus also. Studies on the prevalence of C.F. antibody in sera from infants and young children revealed a pattern of rapid acquisition of antibody to both the human reovirus-like agent and the N.C.D.V. as over 80% of these individuals possessed antibody to each agent by 36 months of age. A strong positive association was found in the results obtained with the two antigens. The ready availability of cell-culture-grown N.C.D.V., and its ability to serve as a " substitute " C.F. antigen for the human reovirus-like agent, should enable the sero-diagnosis of many cases of disease due to the human agent and facilitate seroepidemiological studies of such infections. In addition, the observation that a large proportion of individuals infected with the human reovirus-like agent develop serological evidence of infection not only to the human agent but to the calf agent as well may have important implications in the immunoprophylaxis of disease caused by the human reovirus-like agent.

An electron microscopic study of rabbit syncytium virus.

SummaryThe ultrastructure and viruscell relation of rabbit syncytium virus was studied by electron microscopy. The virus was seen in infected cell cultures, frequently in the cytoplasm and rarely in the nucleus, as a 650 A-diameter, nonmembrane-bound sphere. It was rarely found in intracytoplasmic vesicles as a 750-800 A-diameter, membrane-bound particle, the latter particle having acquired, in passing intravesicularly, a membrane derived from the vesicle wall The virus appeared to originate within dense cytoplasmic inclusions, and rarely, within similar nuclear inclusions. The virus particles were frequently associated with membrane-bound intracytoplasmic and intranuclear rods whose diameter was 750-1100 A. The biologic significance of the rod structures is not known. Our findings suggest that the ultrastructure and the intracellular behavior of rabbit syncytium are unlike those associated with any known virus, but approach most nearly those associated with the virus of epizootic diarrhea of infant mice....

Further observations on the virus of epizootic diarrhea of infant mice: An electron microscopic study

The particulate form of the virus of epizootic diarrhea of infant mice first appears as a single-membraned spherical structure, the central body, in cytoplasmic viroplasm. A nucleoid develops in the central body which moves into the cisterna of the endoplasmic reticulum (ER). In doing so it acquires a segmented “shell” which has an outer unit membrane. However, many particles without a shell and particles without nucleoids are present within the ER cisternae. Tubules bounded by a single membrane are present in the nucleus of infected cells and single- and double-membraned tubules of about the same diameter as the virus particles are present in the cytoplasm. Their role in the virus life cycle is not known.