Diversity and generation of defective interfering influenza virus particles.
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Defective Viruses↗
Biomedical subjects
J M Janda
Publications and source records attributed to J M Janda.
Defective influenza viral ribonucleoproteins cause interference.
Ribonucleoproteins (RNPs) isolated from infectious and defective interfering (DI) influenza virus (WSN) contained three major RNP peaks when analyzed in a glycerol gradient. Peak I RNP was predominant in infectious virus but was greatly reduced in DI virus preparations. Conversely, peak III RNP was elevated in DI virus, suggesting a large increase in DI RNA in this fraction. Labeled [(32)P]RNA was isolated from each RNP region and analyzed by electrophoresis on polyacrylamide gels. Peak I RNP contained primarily the polymerase and some HA genes, peak II contained some HA gene but mostly the NP and NA genes, and peak III contained the M and NS genes. In addition, peak III RNP from DI virus also contained the characteristic DI RNA segments. Interference activity of RNP fractions isolated from infectious and DI virus was tested using infectious center reduction assay. RNP peaks (I, II, and III) from infectious virus did not show any interference activity, whereas the peak III DI RNP caused a reduction in the number of infectious centers as compared to controls. Similar interference was not demonstrable with peak I RNP of DI virus nor with any RNP fractions from infectious virus alone. The interference activity of RNP fractions was RNase sensitive, suggesting that the DI RNA contained in DI RNPs was the interfering agent, and dilution experiments supported the conclusion that a single DI RNP could cause interference. The interfering RNPs were heterogeneous, and the majority migrated slower than viral RNPs containing M and NS genes. These results suggest that DI RNP (or DI RNA) is also responsible for interference in segmented, negative-stranded viruses.
Defective Viruses↗
Homologous interference mediated by defective interfering influenza virus derived from a temperature-sensitive mutant of influenza virus.
A temperature-sensitive group II mutant of influenza virus, ts-52, with a presumed defect in viral RNA synthesis, readily produced von Magnus-type defective interfering virus (DI virus) when passed serially (four times) at high multiplicity in MDBK cells. The defective virus (ts-52 DI virus) had a high hemagglutinin and a low infectivity titer, and strongly interfered with the replication of standard infectious viruses (both ts-52 and wild-type ts+) in co-infected cells. Progeny virus particles produced by co-infection of DI virus and infectious virus were also defective and also had low infectivity, high hemagglutinating activity, and a strong interfering property. Infectious viruses ts+ and ts-52 were indistinguishable from ts-52 DI viruses by sucrose velocity or density gradient analysis. Additionally, these viruses all possessed similar morphology. However, when the RNA of DI viruses was analyzed by use of polyacrylamide gels containing 6 M urea, there was a reduction in the amount of large RNA species (V1 to V4), and a number of new smaller RNA species (D1 to D6) with molecular weights ranging from 2.9 X 10(5) to 1.05 X 10(5) appeared. Since these smaller RNA species (D1 to D6) were absent in some clones of infectious viruses, but were consistently associated with DI viruses and increased during undiluted passages and during co-infection of ts-52 with DI virus, they appeared to be a characteristic of DI viruses. Additionally, the UV target size of interfering activity and infectivity of DI virus indicated that interfering activity was 40 times more resistant to UV irradiation than was infectivity, further implicating small RNA molecules in interference. Our data suggest that the loss of infectivity observed among DI viruses may be due to nonspecific loss of a viral RNA segment(s), and the interfering property of DI viruses may be due to interfering RNA segments (DIRNA, D1 to D6). ts-52 DI virus interfered with the replication of standard virus (ts+) at both permissive (34 degrees C) and nonpermissive temperatures. The infectivity of the progeny virus was reduced to 0.2% for ts+ and 0.05% for ts-52 virus without a reduction in hemagglutinin titer. Interference was dependent on the concentration of DI virus. A particle ratio of 1 between DI virus (0.001 PFU/cell) and infectious virus (1.0 PFU/cell) produced a maximal amount of interference. Infectious virus yield was reduced 99.9% without any reduction of the yield of DI viruses Interference was also dependent on the time of addition of DI virus. Interference was most effective within the first 3 h of infection by infectious virus, indicating interference with an early function during viral replication.
Cell Line↗
Evaluation of five rapid systems for the identification of Neisseria gonorrhoeae.
Five commercial kit systems for the rapid identification of Neisseria gonorrhoeae were evaluated. The systems were tested with various pathogenic and saprophytic Neisseria and Branhamella strains having reactions typical for their individual species. Three systems (RIM-N, quadFERM, and RapID NH) were found to be 100% sensitive and specific.
Costs and Cost Analysis↗
In vitro susceptibilities of Edwardsiella tarda to 22 antibiotics and antibiotic-beta-lactamase-inhibitor agents.
The in vitro susceptibilities of 22 isolates of Edwardsiella tarda were studied with 22 antibiotics and antibiotic-beta-lactamase-inhibitor agents. Results indicated that all isolates were susceptible to the aminoglycosides, cephalosporins, penicillins, imipenem, aztreonam, ciprofloxacin, and antibiotic-beta-lactamase-inhibitor agents. Each strain produced a beta-lactamase even though no resistance was detected to the beta-lactams.
Animals↗
Clinical disease spectrum and pathogenic factors associated with Plesiomonas shigelloides infections in humans.
Plesiomonas shigelloides is a gram-negative, facultatively anaerobic rod whose appropriate taxonomic position is presently under investigation. The isolation and identification of this microorganism in contaminated specimens (e.g., feces) by a clinical laboratory depend on the screening of gram-negative colonies for oxidase and indole positivity and the appropriate use of selective and differential agars. Plesiomonads have been associated with extraintestinal diseases (bacteremia, meningitis) on rare occasions; they have been recovered sporadically from patients presenting with acute gastroenteritis. Although case reports and epidemiologic data support a role for P. shigelloides in diarrheal disease, laboratory investigations have failed to identify an enteropathogenic mechanism in these bacteria consistently or to reveal an animal model that faithfully reproduces the disease. Moreover, studies with volunteers have failed to establish an etiologic relation between Plesiomonas and bacterial gastroenteritis. An accurate picture of the role of this bacterium in human disease must await future studies.
Bacterial Infections↗
Mesophilic aeromonads in human disease: current taxonomy, laboratory identification, and infectious disease spectrum.
The importance of the genus Aeromonas in human disease has recently become better appreciated through the use of improved methodologies for the recovery and identification of aeromonads from biologic specimens and as a result of medical studies aimed at determining the clinical significance of these bacteria when isolated from localized and invasive infections of humans. Taxonomic schemes currently allow for the identification of six Aeromonas species (five mesophilic and one psychrophilic), four of the five mesophilic species having been recovered from infectious processes or isolated from clinical material of human origin. Two major categories of human illness attributed to Aeromonas species have been observed: acute gastroenteritis in both pediatric and adult populations and disseminated disease (e.g., bacteremia) in persons with underlying hematologic malignancies or hepatic dysfunctions. Although the role of mesophilic aeromonads as important agents of bacterial gastroenteritis remains unconfirmed because of the inability to fulfill Koch's postulates (no animal model), several lines of compelling clinical and laboratory evidence indicate that these microorganisms are significant enteric pathogens.
Aeromonas↗