Biomedical subjects

S S Monroe

Publications and source records attributed to S S Monroe.

83 records · Page 5Linked to original sources

PubMed1991

Temporal synthesis of proteins and RNAs during human astrovirus infection of cultured cells.

Astroviruses are nonenveloped particles with a distinctive star-shaped surface structure that have been detected by electron microscopy in stool samples from humans and animals with gastroenteritis. We examined the patterns of macromolecular synthesis in astrovirus-infected cells with a goal of establishing a molecular basis for taxonomic classification. Trypsin is required for continuous replication of astrovirus in cultured cells; however, during a single cycle of infection, astrovirus antigen was synthesized earlier and at higher levels when serum, rather than trypsin, was included in the growth medium. This enhanced production of antigen, as measured by enzyme immunoassay, was accompanied by the appearance of aggregates of virus particles in the cytoplasm of infected cells. During astrovirus replication in cells cultured in the presence of serum, we detected a single infection-specific protein (90 kDa) beginning at 12 h postinfection. This protein was recognized by antiastrovirus rabbit serum and was sensitive to trypsin digestion in vitro, with the concomitant appearance of three smaller immunoreactive proteins (31, 29, and 20 kDa). We also detected two dactinomycin-resistant RNAs (7.2 and 2.8 kb), both of which were polyadenylated, in the cytoplasm of astrovirus-infected cells. The larger of these two RNAs is presumably the viral genome, whereas the smaller species may be a subgenomic messenger. Comparison of the proteins and RNAs synthesized in astrovirus-infected cells with those of the recognized families of nonenveloped single-stranded RNA animal viruses suggests that astroviruses should not be classified as members of either Caliciviridae or Picornaviridae.

Antigens, Viral↗

PubMed1990

Viral agents of gastroenteritis. Public health importance and outbreak management.

Each year, infectious gastroenteritis causes greater than 210,000 children in the United States to be hospitalized and 4-10 million children to die worldwide. Since the mid-1970s, knowledge has increased dramatically concerning the viral agents that are responsible for much of this public health burden. Rotavirus, the most common cause of diarrhea among children, infects virtually every child in the United States by the age of 4 years and causes potentially lethal dehydration in 0.75% of children less than 2 years of age. Other recently identified pathogens include the enteric adenoviruses, calicivirus, astrovirus, and the Norwalk family of agents. Conclusive diagnosis of these viruses requires electron microscopic examination of stool specimens, a laboratory technique that is available only at a few large centers, including CDC. Stool samples from an outbreak that are submitted to CDC for detection of viral pathology should be collected in bulk from 10 ill persons during their first 48 hours of illness, while feces are still liquid, and should be stored at 4 C (not frozen). Acute- and convalescent-phase serum samples should be collected from the same persons, plus from an equal number of controls, during the first week of illness and 3 weeks thereafter. Control measures for outbreaks of viral gastroenteritis should focus on the removal of an ongoing common source of infection (e.g., an ill food handler or the contamination of a water supply) and on the interruption of person-to-person transmission that can perpetuate an outbreak in a population after the common source has been removed. Because improvements in environmental hygiene may not be accompanied by reductions of endemic diarrhea caused by viruses, immunization may play an important role in future control; vaccine trials for rotavirus are in progress. In anticipation of vaccine development and use, CDC recently began national surveillance for the viral agents of gastroenteritis. Health-care facilities involved in the detection of rotavirus or the other viral agents of diarrhea can participate.

Acute Disease↗

PubMed1990

An outbreak of acute gastroenteritis caused by a small round structured virus in a geriatric convalescent facility.

An outbreak of acute gastroenteritis (AGE) occurred in a 201-bed geriatric convalescent facility in Los Angeles County during December 1988 through January 1989. The attack rate was 55% among residents and 25% among employees. Illnesses were characterized by vomiting and diarrhea to a lesser extent, and the absence of fever. Bacterial and parasitic tests in a sample of patients were negative. A 27 nm small round structured virus (SRSV) was identified in one of 30 stools studied by immune electron microscopy (IEM). While rotavirus and influenza A and B were found in three, one and three cases, respectively, no alternative etiologic agent could be demonstrated for most cases. The outbreak met Centers for Disease Control (CDC) clinical and epidemiologic criteria for Norwalk-like gastroenteritis. The death rate of residents was not elevated beyond baseline during the outbreak; however, one healthy employee had diarrhea and dehydration and died after developing an arrhythmia. An autopsy showed moderate, diffuse lymphocytic and neutrophilic myocarditis, and viral studies found influenza A in left ventricular tissue. Fourteen (25%) of 57 employee cases worked in occupations without routine stool or patient contact. At least nine of these employees lacked evidence of direct fecal contact, and transmission of infection in these cases may have been airborne.

Acute Disease↗

PubMed1989

Viral gastroenteritis aboard a cruise ship.

A 32-nm small round structured virus (SRSV), possibly related to the Snow Mountain agent (SMA), was implicated as the cause of recurrent outbreaks of gastroenteritis on a cruise ship. There was no identifiable relation to food or water consumption, but the risk of gastroenteritis among passengers who had shared toilet facilities was twice that of those who had a private bathroom and the rate of illness was related to the number of passengers sharing a communal restroom (ie, with one or more toilets): contaminated bathrooms may be an important vehicle for person-to-person spread of this enteric agent. In each cabin, index patients who had vomited in their cabins were more likely to have had cabinmates who subsequently became ill than were index patients who had not vomited. These epidemiological findings implicate vomitus in the transmission of viral gastroenteritis and they are consistent with the transmission of viral agents by airborne droplets or person-to-person contact. New strategies for prevention of viral gastroenteritis should include protection against environmental contamination by viruses in airborne droplets or vomitus.

Acute Disease↗

PubMed1989

Purification and characterization of adult diarrhea rotavirus: identification of viral structural proteins.

Adult diarrhea rotavirus (ADRV) is a newly identified strain of noncultivable human group B rotavirus that has been epidemic in the People's Republic of China since 1982. We have used sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western (immuno-) blot analysis to examine the viral proteins present in the outer and inner capsids of ADRV and compared these with the proteins of a group A rotavirus, SA11. EDTA treatment of double-shelled virions removed the outer capsid and resulted in the loss of three polypeptides of 64, 61, and 41, kilodaltons (kDa). Endo-beta-N-acetylglucosaminidase H digestion of double-shelled virions identified the 41-kDa polypeptide as a glycoprotein. CaCl2 treatment of single-shelled particles removed the inner capsid and resulted in the loss of one polypeptide with a molecular mass of 47 kDa. The remaining core particle had two major structural proteins of 136 and 113 kDa. All of the proteins visualized on sodium dodecyl sulfate-polyacrylamide gel electrophoresis were antigenic by Western blot analysis when probed with convalescent-phase human and animal antisera. A 47-kDa polypeptide was most abundant and was strongly immunoreactive with human sera, animal sera raised against ADRV and against other group B animal rotaviruses (infectious diarrhea of infant rat virus, bovine and porcine group B rotavirus, and bovine enteric syncytial virus) and a monoclonal antibody prepared against infectious diarrhea of infant rat virus. This 47-kDa inner capsid polypeptide contains a common group B antigen and is similar to the VP6 of the group A rotaviruses. Human convalescent-phase sera also responded to a 41-kDa polypeptide of the outer capsid that seems similar to the VP7 of group A rotavirus. Other polypeptides have been given tentative designations on the basis of similarities to the control preparation of SA11, including a 136-kDa polypeptide designated VP1, a 113-kDa polypeptide designated VP2, 64- and 61-kDa polypeptides designated VP5 and VP5a, and several proteins in the 110- to 72-kDa range that may be VP3, VP4, or related proteins. The lack of cross-reactivity on Western blots between antisera to group A versus group B rotaviruses confirmed that these viruses are antigenically quite distinct.

Adult↗

PubMed1985

Studies of defective interfering RNAs of Sindbis virus with and without tRNAAsp sequences at their 5' termini.

Three of six independently derived defective interfering (DI) particles of Sindbis virus generated by high-multiplicity passaging in cultured cells have tRNAAsp sequences at the 5' terminus of their RNAs (Monroe and Schlesinger, J. Virol. 49:865-872, 1984). In the present work, we found that the 5'-terminal sequences of the three tRNAAsp-negative DI RNAs were all derived from viral genomic RNA. One DI RNA sample had the same 5'-terminal sequence as the standard genome. The DI RNAs from another DI particle preparation were heterogeneous at the 5' terminus, with the sequence being either that of the standard 5' end or rearrangements of regions near the 5' end. The sequence of the 5' terminus of the third DI RNA sample consisted of the 5' terminus of the subgenomic 26S mRNA with a deletion from nucleotides 24 to 67 of the 26S RNA sequence. These data showed that the 5'-terminal nucleotides can undergo extensive variations and that the RNA is still replicated by virus-specific enzymes. DI RNAs of Sindbis virus evolve from larger to smaller species. In the two cases in which we followed the evolution of DI RNAs, the appearance of tRNAAsp-positive molecules occurred at the same time as did the emergence of the smaller species of DI RNAs. In pairwise competition experiments, one of the tRNAAsp-positive DI RNAs proved to be the most effective DI RNA, but under identical conditions, a second tRNAAsp-positive DI RNA was unable to compete with the tRNAAsp-negative DIs. Therefore, the tRNAAsp sequence at the 5' terminus of a Sindbis DI RNA is not the primary factor in determining which DI RNA becomes the predominant species in a population of DI RNA molecules.

Aspartic Acid↗

PubMed1984

Common and distinct regions of defective-interfering RNAs of Sindbis virus.

Defective-interfering (DI) particles are helper-dependent deletion mutants which interfere specifically with the replication of the homologous standard virus. Serial passaging of alphaviruses in cultured cells leads to the accumulation of DI particles whose genomic RNAs are heterogeneous in size and sequence composition. In an effort to examine the sequence organization of an individual DI RNA species generated from Sindbis virus, we isolated and sequenced a representative cDNA clone derived from a Sindbis DI RNA population. Our data showed that: (i) the 3' end of the DI RNA template was identical to the 50 nucleotides at the 3' end of the standard RNA; (ii) the majority (75%) of the DI RNA template was derived from the 1,200 5'-terminal nucleotides of the standard RNA and included repeats of these sequences; and (iii) the 5' end of the DI RNA template was not derived from the standard RNA, but is nearly identical to a cellular tRNAAsp (S. S. Monroe and S. Schlesinger, Proc. Natl. Acad. Sci. U.S.A. 80:3279-3283, 1983). We have also utilized restriction fragments from cloned DNAs to probe by blot hybridization for the presence of conserved sequences in several independently derived DI RNA populations. These studies indicated that: (i) a 51-nucleotide conserved sequence located close to the 5' end of several alphavirus RNAs was most likely retained in the DI RNAs; (ii) the junction region containing the 5' end of the subgenomic 26S mRNA was deleted from the DI RNAs; and (iii) the presence of tRNAAsp sequences was a common occurrence in Sindbis virus DI RNAs derived by passaging in chicken embryo fibroblasts.

Base Sequence↗

PubMed1983

RNAs from two independently isolated defective interfering particles of Sindbis virus contain a cellular tRNA sequence at their 5' ends.

Defective interfering (DI) particles are deletion mutants that interfere specifically with the replication of homologous standard virus. We have determined the 5'-terminal nucleotide sequences of two DI RNA populations by the following methods: (i) cloning of the cDNA from one of the DI RNA populations and sequencing a representative clone, and (ii) using both DI RNA populations as templates for preparing primer-directed cDNA transcripts and sequencing these transcripts. The 5' terminal sequences of the two DI RNA populations were not derived from standard Sindbis viral RNA but were almost identical to those of a cellular tRNAAsp.

Animals↗

PubMed1982

Sequence analysis of cDNA's derived from the RNA of Sindbis virions and of defective interfering particles.

Sindbis virus generates defective interfering (DI) particles during serial high-multiplicity passage in cultured cells. These DI particles inhibit the replication of infectious virus and can be an important factor in the establishment and maintenance of persistent infection in BHK cells. In an effort to understand how these DI particles are generated and how they interfere with the replication of standard virus, we performed a partial sequence analysis of the RNA obtained from two independently isolated populations of DI particles and from two Sindbis virus variants and compared these with the RNA of the parental wild-type virus. The 3'-terminal regions of the RNAs were sequenced by the dideoxy chain terminating method. Internal regions of the RNA were examined by restriction endonuclease digestion of cDNA's made to the various RNAs and by direct chemical sequencing of 5' end-labeled restriction fragments from cDNA made to the DI RNAs. One of the variant viruses examined was originally derived from cells persistently infected with Sindbis virus for 16 months and is resistant to interference by the DI strains used. In the 3'-terminal region of the RNA from this variant, only two base changes were found; one of these occurs in the 20-nucleotide 3'-terminal sequence which is highly conserved among alphaviruses. The DI RNA sequences were found to have been produced not by a single deletional event, but by multiple deletion steps combined with sequence rearrangements; all sequences examined are derived from the plus strand of Sindbis virion RNA. Both DI RNAs had at least 50 nucleotides of wild-type sequence conserved at the 3' terminus; in addition, they both contained conserved and perhaps amplified sequences derived from the non-26S region of the genome which may be of importance in their replication and interference ability.

Base Sequence↗

PubMedDate not supplied

"Norwalk-like viruses" as a cause of foodborne disease outbreaks.

While outbreaks of foodborne disease remain an important public health concern, their aetiology is not identified in a majority of instances. In targeted studies, the application of newly developed molecular assays has demonstrated that a large proportion of these outbreaks may be caused by the "Norwalk-like viruses" (NLV), a genus of genetically related viruses belonging to the family Caliciviridae. NLV outbreaks associated with consumption of faecally contaminated oysters are frequently reported and can best be controlled by preventing contamination of oyster-harvesting waters. Infectious foodhandlers are another frequent source of contamination, and such transmission can be minimised by exclusion of ill foodhandlers and the maintenance of strict personal hygiene. Molecular assays have greatly refined the epidemiological investigation of foodborne NLV outbreaks, allowing the linking of outbreaks in different locations and permitting the identification of the virus in the implicated vehicle. The development of simpler and more sensitive assays and their use on a broader scale will assist in defining the true burden of foodborne NLV outbreaks and improve strategies for their prevention and control.

Animals↗

PubMedDate not supplied

Norwalk-like viral gastroenteritis outbreak in U.S. Army trainees.

An outbreak of acute gastroenteritis hospitalized 99 (12%) of 835 U. S. Army trainees at Fort Bliss, El Paso, Texas, from August 27 to September 1, 1998. Reverse transcriptase polymerase chain reaction tests for Norwalk-like virus were positive for genogroup 2. Gastroenteritis was associated with one post dining facility and with soft drinks.

Caliciviridae Infections↗