Maternal antibody-mediated protection against gastroenteritis due to rotavirus in newborn mice is dependent on both serotype and titer of antibody

In order to evaluate the role of passively acquired, rotavirus-specific antibodies in protection against diarrhea, we inoculated mouse dams with rotaviruses of various serotypes, and their newborns were orally challenged with a primate rotavirus (simian SA-11). Dams were immunized by using a regimen that included repeated inoculations administered either orally or intraperitoneally with adjuvant. The serum antibody response detected in dams by radioimmunoassay and plaque-reduction neutralization after parenteral immunization was approximately 15-fold and 80-fold greater, respectively, than that found after oral "hyperimmunization." Parenteral immunization with rotavirus serotypes either homotypic or heterotypic to the challenge virus protected suckling mice against diarrhea; protection was closely correlated with the in vitro neutralizing activity of maternal serum against the challenge virus. Oral immunization with only rotavirus strains homotypic to the challenge virus afforded protection; the lower immune response after oral immunization with rotaviruses heterotypic to the challenge virus resulted in a titer of neutralizing antibody to the challenge virus below the protective threshold. From our current studies it appears that antibody-mediated passive protection against rotavirus challenge is dependent on both serotype and titer of antibody.

Diverse serologic response to rotavirus infection of infants in a single epidemic

Eight infants with onset of gastroenteritis occurring within a 32-day period were examined for stool rotavirus antigen and serum antibody response to rotavirus. Each infant presented evidence of rotavirus infection but no single test for rotavirus-specific antigen or antibody was positive for every infected individual. Rotavirus was identified in the stools of five infants; in the others rotavirus etiology was determined by a specific immune response only. The neutralizing antibody response to each of four human rotavirus serotypes and to bovine rotavirus Nebraska calf diarrhea virus ranged from totally negative to a specific response to up to four serotypes. Three originally seropositive infants each showed an increase in neutralizing antibody titer to two or more serotypes. However, two of five originally seronegative infants also developed antibody to two or more serotypes. No consistent pattern of responses to different serotypes was detected.

Rotavirus-specific antibodies in fetal bovine serum and commercial preparations of serum albumin

Rotavirus-specific antibodies were detected in fetal bovine serum, bovine serum albumin, and human serum albumin by radioimmunoprecipitation with the NCDV strain of bovine rotavirus as the detecting antigen. Fetal bovine sera neutralized bovine rotavirus in a plaque reduction neutralization test to titers of 1:20 or greater. Immunoglobulins purified from fetal bovine serum by protein A-agarose affinity chromatography precipitated rotavirus antigens but did not neutralize bovine rotavirus. Rotavirus antibodies in fetal bovine serum and in purified serum albumin preparations may interfere with diagnostic assays for the detection of rotavirus antigens or antibodies.

A murine model for oral infection with a primate rotavirus (simian SA11)

Simian rotavirus SA11 was shown to replicate in the gastrointestinal tracts of infant mice after oral inoculation. Clinical symptoms, histopathological changes in the small intestinal mucosa, and the type-specific humoral immune response were all characteristic of rotavirus-induced gastroenteritis. The availability of this small animal model for the study of a primate rotavirus infection should expedite analysis of the immune response necessary for protection against challenge.

Response of mice to rotaviruses of bovine or primate origin assessed by radioimmunoassay, radioimmunoprecipitation, and plaque reduction neutralization

Sera from (i) gnotobiotic BALB/c, CD-1, and CFW mice and (ii) conventional BALB/c mice were evaluated by radioimmunoassay, radioimmunoprecipitation, and plaque reduction neutralization, using the Wa, SA-11, and WC-3 (bovine) strains of rotavirus as the detecting antigens. The gnotobiotic mice had no antirotavirus antibody detectable by radioimmunoprecipitation and no neutralizing antibody at a dilution of 1:50 by plaque reduction neutralization. All sera from the conventional mice had rotavirus-specific antibodies detected by radioimmunoassay and by radioimmunoprecipitation at serum dilutions of 1:50 and 1:10,000, respectively. The antibodies were directed against viral proteins p116, p94, p88, and p84 of all three viruses, but had no neutralizing activity against heterologous rotaviruses at a dilution of 1:50. Conventional seropositive mice were parenterally immunized with the Wa, SA-11, or WC-3 strain of rotavirus. An approximate 100-fold increase in rotavirus-specific antibodies was detected by radioimmunoassay, and greater than 20-fold selective neutralization of the immunizing strain of virus was observed. Sera from the mice immunized with Wa virus had antibodies directed against inner and outer capsid proteins of all three rotaviruses. The mouse can be a useful model for studying the immune response to heterologous rotavirus infection; preexisting antibodies presumably directed towards murine rotavirus do not prevent the development of a type-specific immune response to a nonmurine rotavirus.

The cultivation of human rotavirus, strain 'Wa', to high titer in cell culture and characterization of the viral structural polypeptides

The structural proteins of the 'Wa' (serotype 2) strain of human rotavirus have not been described previously. Single-cycle virus growth in MA-104 cells using 5 micrograms/ml of trypsin in the growth medium was rapid with maximal viral yields (approximately 10(6) PFU/ml) obtained 10-12 h post-infection. There was a continuous progression of cytopathic effect (CPE) from 6- to 5-h post-infection. Under conditions of multiple-cycle growth, a greater concentration of trypsin (40 micrograms/ml) in the growth medium was required to obtain rapid progression of CPE and production of a high titer (approximately 10(7) PFU/ml) of infectious (double-shelled) virus. Single- and double-shelled virions were separated by isopycnic centrifugation in CsCl and analyzed by SDS-PAGE. Five proteins with molecular weights of 116,000, 92,000, 88,000, 84,000 and 41,000 were identified as components of the inner shell and four proteins with molecular weights of 60,000, 38,000, 32,000 and 27,000 were located in the outer shell.

Similarity in the bound carbohydrate groups of glycoproteins from cells of several vertebrate classes

The carbohydrate groups of the glycoproteins of human, hamster, chick, reptile and fish cells growing in culture have been fractionated in succession according to size (Sephadex G-50), affinity for concanavalin A, charge (DEAE-Sephadex) and by thin-layer chromatography. It was found that despite the complexity of the array of separable glycopeptides in each type of cell, most of these structures seemed to be common to all of the cells. This suggests that they have existed in a relatively stable state for several hundreds of millions of years throughout the evolution of the vertebrates.

Defective interfering particles of fixed rabies viruses: lack of correlation with attenuation or auto-interference in mice

Six different fixed strains of rabies virus were analysed for their capacity to produce defective particles following acute infection of BHK-21 cells. Five of the six strains produced one or more defective particle populations with strain-specific sedimentation properties, particle length and abbreviated RNA genome size. These defective particles varied in their capacity to interfere with replication of standard rabies virus in cell culture. Each virus strain characteristically either killed adult mice according to a normal dose-response pattern or to an auto-interference type of pattern, or failed to kill mice. Different strains also varied in their capacity to induce a cytopathic effect in cell culture. However, there was no apparent correlation between the presence of defective particles and the pathogenic potential of rabies virus in mice or in cell culture.

Integration pattern of hepatitis B virus DNA sequences in human hepatoma cell lines

Four human hepatoma cell lines established from primary hepatocellular carcinomas were examined for the presence of hepatitis B virus DNA sequences. Reassociation kinetic analysis indicated that the cell lines HEp-3B 217, HEp-3B 14, HEp-3B F1, and PLC/PRF/5 contained two, one, one, and four genome equivalents per cell, respectively. Southern blot hybridization analysis demonstrated that hepatitis B virus DNA was integrated into the cellular DNAs of these cell lines. Further liquid hybridization studies with 32P-labeled HincII restriction fragments of hepatitis B virus DNA established that DNA sequences from all regions of the HBV genome were represented in the integrated viral sequences. Although the three HEp-3B cell lines were derived from the same tumor, they differed significantly in their patterns of integration of hepatitis B virus DNA, the number of copies of viral DNA per cell, and their ability to produce the virus-coded surface antigen.

Regeneration of DI particles of virulent and attenuated rabies virus: genome characterization and lack of correlation with virulence phenotype

Two strains of fixed rabies virus were examined for their ability to regenerate defective interfering (DI) particles and for possible correlation of DI particle production with the expression of virulence. A plaque-purified stock of the attenuated ERA strain (ERApp), which characteristically caused an auto-interfering death response in adult mice inoculated i.c., was serially passed at a high m.o.i. inBHK-21 cells. By the sixth passage, DI particles were regenerated that corresponded in sedimentation velocity and DI/RNA size to the smallest of three sizes of DI particles produced by the parental stock virus. The regeneration of ERA DI particles in vivo was not detected during 15 serial high or low m.o.i. passages of infected newborn mouse brain, though the passaged virus consistently elicited an auto-interfering-type death response when assayed in adult mice. The attenuated Flury HEPpp strain regenerated up to three unique size classes of DI particles during serial passage in BHK-21 or murine neuroblastoma C1300 clone NA cells compared with the one band of DI particles produced by the parental Flury HEP stock virus. The BHK-21 cell-adapted Flury HEPpp virus failed to kill adult mice when inoculated at high concentrations after two serial passages in NA cells. However, the virus became fully virulent and a single band of regenerated DI particles was visible. Additional bands of defective particles were visible following the third serial passage in NA cells. Single-stranded RNA with a mol. wt. of 0.62 x 10(6) was extracted from the first DI particle population to be regenerated. This corresponded in mol. wt. to the DI/ssRNA characteristic of the parental attenuated Flury HEP virus. However, in the parental type DI/RNA, partially dsRNA could be isolated in addition to ssRNA. Double-stranded RNA could not be detected in the regenerated DI particles derived from the virulent NA cell-propagated Flura HEPpp virus. These results suggest that the virulence phenotype of fixed rabies viruses does not depend on the presence or absence of DI particles.

Rabies serogroup viruses in neuroblastoma cells: propagation, "autointerference," and apparently random back-mutation of attenuated viruses to the virulent state

Each of several strains of fixed rabies virus was found to replicate to high titers in C1300 mouse neuroblastoma (clone NA) cells, without adaptation. Rabies serogroup Lagos bat, Mokola, and Duvenhage viruses also replicated efficiently in NA cells. Kotonkan and Obodhiang viruses replicated efficiently after adaptation, to titers not previously obtained in vitro. Infection in NA cells was frequently more cytopathic than in BHK-21 cells, allowing titration of Kotonkan and Obodhiang viruses by plaque assay. Duvenhage virus caused syncytium formation. Serial propagation of rabies viruses at a high multiplicity of infection in NA cells led to a rapid decline in virus yields; similar "autointerference" has not previously been demonstrated with rabies virus in other cell systems. Rabies virus infection in NA cells exhibited extreme sensitivity to interference by experimentally added defective interfering virions. Although several strains of attenuated rabies virus consistently reverted rapidly to virulence after propagation in NA cells, other strains of attenuated rabies and rabies serogroup viruses acquired increased virulence at a more gradual rate or not at all, suggesting that diverse characters may control virulence. When attenuated Flury HEP rabies virus was serially propagated at a low multiplicity of infection in either NA cells or suckling mouse brain, virulence appeared at a very variable rate, indicating that these systems may selectively enhance replication of randomly occurring virulent virus mutants.

Fer de Lance virus (FDLV): a probable paramyxovirus isolated from a reptile

A new virus has been isolated by inoculation of lung tissues of diseased snakes into snake embryos. Homogenates of infected embryo tissues caused c.p.e. in cell cultures incubated at 30 degrees C. The virus replicates in a wide variety of reptilian or mammalian cell types incubated at 30 degrees C, inducing either syncytium formation or minimal or no cytopathic changes. Efficient replication occurs in embryonated hens' eggs at 27 to 30 degrees C. The virus haemagglutinates guinea pig and chick erythrocytes; it possesses a neuraminidase similar to the receptor-destroying enzyme of Vibrio cholera. Electron microscopic observations of infected cells examined in thin section revealed pleomorphic viruses 146 to 321 nm in diam. resembling known myxoviruses. Internal nucleocapsid strands are 15 to 16 nm in diam.; nucleocapsid observed in negatively stained preparations measures 14 nm in diam. The virus was determined to possess a nucleoprotein core containing a 50S single-stranded unsegmented RNA genome. All characters of the virus are similar to those of the paramyxovirus group except that the nucleocapsid diam. is intermediate between that of paramyxoviruses and pneumoviruses. The virus is antigenically distinct from known myxoviruses and is unique among myxoviruses in its restriction to growth at temperature below 37 degrees C.

Evolutionary relatedness of viper and primate endogenous retroviruses

A retrovirus previously isolated from a tumored Russell's viper is shown by molecular hybridization to be an endogenous virus of this reptilian species. Radio-immunologic techniques revealed that the viper retrovirus is immunologically and, hence, evolutionarily related to endogenous type D retorviruses of Old World primates. These findings extend the number of vertebrate classes possessing endogenous retroviruses and suggest that type D retroviruses may even be more widely distributed in nature than type C retroviruses.

Rabies viruses increase in virulence when propagated in neuroblastoma cell culture

Several strains of attenuated rabies virus lacking the capacity to kill adult mice acquired a high lethal potential for mice after one to five serial passages in murine or human neuroblastoma cells. The virulence acquired after passage in neuroblastoma cells is a stable genetic trait retained during subsequent passage of viruses in nonneuroblastoma cell systems.

Role of host immune response in the development of either encephalitic or paralytic disease after experimental rabies infection in mice

The clinical and histopathological manifestations of the infection of immunosuppressed (cyclophosphamide-treated) and immunocompetent (control) adult mice with the CVS ts 2 strain of fixed rabies virus were correlated with the kinetics of virus multiplication in the central nervous system and with the development of serum antibody. In immunocompetent mice severe paralytic disease causing 80% mortality was accompanied by marked inflammation and degeneration of the central nervous system parenchymatous tissue. Antirabies antibody was detected in all immunocompetent mice severely paralyzed from postinoculation day 6 on; virus was rarely isolated. In contrast, immunosuppressed mice developed encephalitic symptoms with only minor paralysis; the infection was 100% fatal. Histopathological changes in immunosuppressed mice were confined to degeneration and necrosis of individual neurons and mild microglial reaction; virus was isolated from all of these mice. No significant level of antibody was detected. Similar manifestations were seen after infection of immunodeficient (athymic) mice except that the athymic mice developed levels of antibody similar to those of control mice on day 6; antibodies in athymic mice were predominantly of immunoglobulin class M.

Ultrastructural studies of cell-virus interaction in reptilian cell lines. IV. Effects of chloramphenicol and ethidium bromide on VSW cell mitochondria and associated virions

Structural effects of chloramphenicol (CAP) and ethidium bromide (EB) on VSW cell mitochondria and intramitochondrial virions (IMV) have been studied on a comparative basis by thin-section electron microscopy. CAP-treated cells show a wide variety of mitochondrial alterations, frequently involving swelling of the organelle and loss of cristae orientation. IMV are generally severely disrupted, particularly in peripheral regions. In such configurations, strand-like material radiates in a spokelike fashion from the shell zone to adjacent cristae-matrix area. EB-treated cells also display considerable mitochondrial distortion evidenced primarily by the formation of small, localized multimembrane regions. IMV exposed to EB, however, are less structurally damaged than CAP-treated ones. The relative incidence of IMV production is enhanced approximately fourfold in EB-treated cells compared to CAP-treated ones, suggesting that virion synthesis may be under nuclear, rather than mitochondrial, control.

Differences in efficiency of protective effect caused by high ambient temperature in mice infected with diverse substrains of rabies virus

We have shown previously that a non-fatal outcome of infection with street rabies virus occurs more often when mice are exposed to a high ambient temperature (HAT = 35 degrees C) early in the course of the infection. To determine what influence the virus strain had on this protective effect of HAT, we have extended these observations to studies of a fixed rabies strain, CVS and several substrains of CVS virus derived from temperature-sensitive (ts) mutants. In all cases, mortality was reduced to some extent by exposure of the animals to HAT; however, dramatic strain-specific differences in the extent of the effect were noted. Although each of the virus substrains tested was revertant in the ts character (as tested in vitro using a non-permissive temperature of 40-5 degrees C), several substrains (ts 1, ts 4, RT51) caused disease that was sensitive (greater than 90% reduction in mortality) to HAT. Mortality induced by the parental CVS virus was reduced approx. 50% at HAT. A single CVS virus substrain, VSW89, caused disease that wal less affected by HAT than was disease induced by the parental strain. As in previous studies with street virus, the incubation periods for infection with CVS virus substrains were consistently prolonged at HAT.

Rabies virus infection in mouse neuroblastoma cells

As part of an inquiry into factors that determine the virulence of fixed rabies virus, mouse neuroblastoma cells were infected in culture with high virulence and low virulence strains of Flury HEP virus. Low virulence virus infection differed from high virulence virus infection in (1) its more rapid production of progeny virus in the early cycles of virus infection as shown by the number of extracellular virus particles and the infectivity of the supernatant fluid; (2) its earlier development of viral antigens on the cell surface; and (3) its earlier and more severe morphologic alteration of the cell surface. Where applicable, the differences were corroborated by scanning and transmission electron microscopy of the infected cells using the critical point drying technique on whole cells. The number of cells susceptible to complement-dependent immunolysis was almost proportional to the number of cells that were surface antigen-positive regardless of the strain of the virus used. Implications of the difference in the kinetics of virus production and of the development of surface antigens between low and high virulence strains are discussed.

Pathogenic mycoplasmas: cultivation and vertebrate pathogenicity of a new spiroplasma

A spiroplasma recovered from allantoic fluids of chick embryos infected with the tick-derived suckling mouse cataract agent was grown in continuous passage on a new artificial culture medium. The cultured organisms induced typical ocular and other disease symptoms in susceptible animals, and were reisolated from involved host tissues. Although spiroplasmas have been previously recognized as plant and insect pathogens, this is the first spiroplasma shown to multiply at 37 degrees C and to be pathogenic for vertebrates.

Intracytoplasmic type A particles in viper spleen cells

Structures resembling typical type A particles were observed in paranuclear inclusions in cultured C-type particle-producing viper cells (VSW cell line). The incidence of type A particle inclusions was low (approximately 0.5% of cell profiles examined) in untreated cells, but both the incidence and size of the inclusions were slightly increased in cells treated with ethidium bromide. This is apparently the first observation of type A particles in cells of a poikilothermic vertebrate.