Increase in norovirus activity reported in Europe.
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Caliciviridae Infections↗
Biomedical subjects
C H von Bonsdorff
Publications and source records attributed to C H von Bonsdorff.
Evaluation of the purification capacity of nine portable, small-scale water purification devices.
A test was performed to evaluate the microbial and chemical purification capacity of nine portable, small-scale water purification filter devices with production capacity less than 100 L/h. The devices were tested for simultaneous removal capacity of bacteria (cultured Escherichia coli, Clostridium perfringens, Klebsiella pneumoniae and Enterobacter cloacae), enteric protozoans (formalin-stored Cryptosporidium parvum oocysts), viral markers (F-RNA bacteriophages) and microcystins produced by toxic cyanobacterial cultures. In general, the devices tested were able to remove bacterial contaminants by 3.6-6.9 log10 units from raw water. Those devices based only on filtration through pores 0.2-0.4 microm or larger failed in viral and chemical purification. Only one device, based on reverse osmosis, was capable of removing F-RNA phages at concentrations under the detection limit and microcystins by 2.5 log10. The present study emphasised the need for evaluation tests of water purification devices from the public safety and HACCP (Hazard Analysis and Critical Control Point) points of view. Simultaneous testing for various pathogenic/indicator microbes and microcystins was shown to be a useful and practical way to obtain essential data on actual purification capacity of commercial small-scale drinking-water filters.
Animals↗
A prolonged outbreak of Norwalk-like calicivirus (NLV) gastroenteritis in a rehabilitation centre due to environmental contamination.
An outbreak of Norwalk-like calicivirus (NLV) gastroenteritis occurred in a rehabilitation centre in southern Finland between December 1999 and February 2000. An epidemiological investigation was conducted to determine the source and extent of the outbreak. More than 300 guests and staff members became ill during the outbreak. No food or activity in the centre could be linked epidemiologically to illness. NLV genogroup II was detected by RT-PCR in stool samples of symptomatic guests and employees. All strains reacted similarly with the microplate hybridization probe panel and showed the same nucleotide sequence, indicating that they represented the same NLV strain. Food and water samples were negative for NLV, whereas NLV was detected in three environmental specimens. The strains from patients and environment were identical based on microplate hybridization probes, suggesting that environmental contamination may have been important for the spread of calicivirus and the protracted course of the outbreak.
Adult↗
Infections of the central nervous system of suspected viral origin: a collaborative study from Finland.
We studied 3231 patients with acute central nervous system (CNS) symptoms of suspected viral origin to elucidate the current etiologic spectrum. In 46% of the cases, a viral finding was observed. Varicella-zoster virus (VZV) was the main agent associated with encephalitis, as well as meningitis and myelitis. VZV comprised 29% of all confirmed or probable etiologic agents. Herpes simplex virus (HSV) and enteroviruses accounted 11% each, and influenza A virus 7%. VZV seems to have achieved a major role in viral infections of CNS. In encephalitis in our population, VZV is clearly more commonly associated with these neurological diseases than HSV. The increase in VZV findings may in part be a pseudophenomenon due to improved diagnostic methods, however, a true increase may have occurred and the pathogenetic mechanisms behind this should be elucidated.
Adenoviridae Infections↗
Waterborne epidemics in Finland in 1998-1999.
Fourteen waterborne epidemics occurred in Finland during 1998-1999. About 7,300 illness cases were registered in these outbreaks. All except one of the waterborne epidemics were associated with undisinfected groundwaters. An equal number of waterborne epidemics occurred in public and private water systems, but most cases of illness occurred in public water systems. The three largest epidemics comprised 6,700 illness cases. Insufficient purification treatment unable to remove Norwalk-like viruses caused the only waterborne epidemic in a surface water plant. The main reasons for groundwater outbreaks were floods and surface runoffs which contaminated water. Norwalk-like viruses caused eight and Campylobacter three of the outbreaks. In two cases the epidemic ceased by the exhaustion of susceptible persons in the exposed community but in most cases it was terminated by changing the water source, boiling the drinking water, and starting chlorination.
Campylobacter Infections↗
[Are food poisonings caused by viruses?].
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Caliciviridae↗
Confirmation of Norwalk-like virus amplicons after RT-PCR by microplate hybridization and direct sequencing.
A large number of Norwalk-like viruses (NLVs) have been identified from stool samples by RT-PCR by amplifying part of the polymerase-coding gene. A set of probes were selected based on sequence analysis of the viruses circulating in Finland during the years 1996-97 for confirmation of the findings by hybridization. A microplate hybridization test, which provides a rapid semi-automatic detection for PCR products, was designed and compared with agarose gel electrophoresis. From the material of 210 stool samples, mainly from diarrheal outbreaks during years 1997-1998, three probes, one for NLV genogroup GGI and one for each of the two GGII subgroups (Toronto-like and Lordsdale-like), were sufficient to detect 87.8% (36/41) of GGI and 89.0% (49/55) of GGII samples positive by gel electrophoresis. Amplicon sequencing of the strains not detected by the above probes revealed genetic variability in the sequences. Biotin-streptavidin binding was used both for microplate hybridization assays and for direct sequencing to identify the amplicons. Based on the sequences three more probes for the hybridization panel were added so that all the different NLVs of this study could be recognized.
Base Sequence↗
An outbreak of calicivirus associated with consumption of frozen raspberries.
In April 1988, an outbreak of gastroenteritis occurred among employees in a large company in Helsinki, Finland. A retrospective cohort study, using a self-administered questionnaire, was carried out to ascertain the cause and extent of the outbreak. To meet the case definition, employees had to have had diarrhoea and/or vomiting since 2 April, 1998. A subanalysis was made in the biggest office, consisting of 360 employees, of whom 204 (57%) completed the questionnaire. Of these 108 (53%) met the case definition. Employees who had eaten raspberry dressing were more likely to meet the case definition than those who had not (Attack Rate (AR) 65% versus AR 18% Relative Risk, (RR) 3.7, 95%, Confidence Intervals (CI) 2.0-6.7). Four stool specimens obtained from affected kitchen staff who had all eaten the raspberry dressing and who had all become ill simultaneously with the employees were positive by polymerase chain reaction (PCR) for calicivirus. The data suggest that the primary source of the outbreak was imported frozen raspberries contaminated by calicivirus.
Adult↗
Outbreak of viral gastroenteritis due to drinking water contaminated by Norwalk-like viruses.
Heinävesi, a Finnish municipality with a population of 4860 inhabitants, had an outbreak of gastroenteritis in March 1998. On the basis of an epidemiologic survey, an estimated 1700-3000 cases of acute gastroenteritis occurred during the outbreak. Municipal water consumption was found to be associated with illness (risk ratio [RR]=3.5, 95% confidence interval, 3.11>RR>3.96). Norwalk-like virus (NLV) genogroup II (GGII) was identified in untreated water, treated water, and 4 tap water samples by use of reverse transcription-polymerase chain reaction. This was the first time NLVs had been detected in municipal tap water. Fifteen of 27 patient stool samples had NLV GGII, with an identical amplification product to that found in the water samples, indicating that the outbreak was caused by this virus. In some patients, NLV genogroup I was also encountered. This virus, however, could not be detected in the water samples. Inadequate chlorination contributed to the survival of the virus in the water.
Caliciviridae Infections↗
[Gene amplification methods in viral diagnostics].
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Clinical Competence↗
Isolation of an iridovirus from pike-perch Stizostedion lucioperca.
We have isolated a large virus from pike-perch Stizostedion lucioperca fingerlings with no signs of disease. The biochemical structural, and serological properties of this newly isolated virus suggest that it belongs to the family Iridoviridae. The virus multiplied and was cytopathogenic in several cultured fish cell lines. The virus has a DNA-containing genome and is assembled in the cytoplasm. When viewed in electron micrographs, the assembly sites showed a paracrystalline array of hexagonal nucleocapsids. The ultrastructure of the pike-perch virus resembled that of previously isolated fish iridoviruses. It is an enveloped icosahedral DNA virus. The diameter of the nucleocapsid in thin sections was 127 +/- 3 nm; in negatively stained preparates the size of the enveloped virus varied from 147 to 187 nm. In immunofluorescence the virus was stained by rabbit antisera against EHN (epizootic haematopoietic necrosis) virus, sheatfish iridovirus and cod iridovirus. The pathogenicity of the virus isolate was studied by inoculation into juvenile rainbow trout Oncorhyncus mykiss. Experimental infection under aquarium conditions suggested that the virus is apothogenic to rainbow trout. The infective virus could be recovered from the viscera of inoculated fish during the first week post-infection, after which the proportion of virus-positive fish declined over time. A small proportion of the fish still carried the virus 24 d post-inoculation.
Animals↗
Assembly of viroplasm and virus-like particles of rotavirus by a Semliki Forest virus replicon.
In this study we have used an expression system based on Semliki Forest virus (SFV) to study assembly and intracellular localization of certain capsid proteins of rotavirus in neurons and mammalian epithelial cells. The complete genes of vp2 (vp2A) and vp6 (vp6A) of group A rotavirus (SA-11) and gene 5 encoding vp6 (vp6C) of porcine group C rotavirus (strain Cowden/AmC-1) were inserted into an SFV expression replicon. Transfection of BHK-21 cells with in vitro-made SFV transcripts resulted in a high level of expression of the heterologous genes. Cotransfection with helper RNA encoding the SFV structural proteins, but lacking the genomic RNA packing signal, resulted in production of recombinant infectious virus. Immunological and biochemical analysis revealed that vp6 was expressed to high levels in primary neurons and mammalian epithelial cells and that vp6 was retained as an authentic homotrimer, stabilized by noncovalent interactions with native antigenic determinants. Thin section electron microscopy analysis revealed that vp6 alone assembled into viroplasm-like structures in the cytoplasm. While coexpression of vp2 and vp6 of group A rotavirus resulted in formation of single-shelled-like particles, no evidence of intracellular assembly was found, suggesting that other viral proteins are required for intracellular formation of single-shelled particles. A notable observation was that the vp6 proteins of group A and C rotaviruses showed different immunofluorescence patterns in BHK-21 cells; vp6C displayed an intense punctate immunofluorescence pattern, while vp6A was characterized by a pronounced filamentous staining in close vicinity to the cytoskeleton.
Animals↗
Short sequences define genetic lineages: phylogenetic analysis of group A rotaviruses based on partial sequences of genome segments 4 and 9.
Genetic diversity in strains of human group A rotaviruses was analysed by phylogenetic methods. The study material comprised 109 serotype G1 or G4 rotavirus samples isolated in Finland during 1986-1990. Parts of the coding regions of rotaviral genome segments 4 and 9, which encode proteins with serotype specificity, the spike protein VP4 (P serotype) and the outer capsid protein VP7 (G serotype), respectively, were sequenced. As determined by analysis of segment 4 sequences all G1 strains and all except one G4 strain showed P[8] specificity, the one being of P[6] specificity. The G1P[8] strains could be further differentiated into four groups based on segment 9 sequences, while G4P[8] strains formed only one group. Type P[8] (G1P[8] and G4P[8]) strains formed two main groups based on segment 4 sequences, suggesting free segregation of segment 4 between these G strains. Most global G1, G4 and P[8] strains in GenBank/EMBL originating from the 1970s to the present co-clustered with these groups, suggesting that the groups exist as relatively stable lineages. No linear accumulation of nucleotide substitutions was detected in strains of one serotype during the study period. Also, the deduced amino acids of the antigenic regions A, B and C of VP7 were nearly conserved within the phylogenetic lineages. Interestingly, only short amino acid sequences were necessary to divide the e-types correctly into phylogenetic lineages. These amino acid signature motifs were located in aa 29-68 of VP7 and aa 121-135 of VP4 of the G1 and P[8] lineages, respectively.
Amino Acid Sequence↗
Baculoviral display of the green fluorescent protein and rubella virus envelope proteins.
The ability to display heterologous proteins and peptides on the surface of different types of bacteriophage has proven extremely useful in protein structure/function studies. To display such proteins in a eucaryotic environment, we have produced a vector allowing for fusion of proteins to the amino-terminus of the Autographa californica nuclear polyhedrosis virus (AcNPV) major envelope glycoprotein, gp64. Such fusion proteins incorporate into the baculoviral virion and display the FLAG epitope tag. We have further produced recombinant baculoviruses displaying the green fluorescent protein (GFP) and the rubella virus envelope proteins, E1 and E2. The incorporation of the GFPgp64, E1gp64, and E2gp64 fusion proteins into the baculovirus particle was demonstrated by western blot analysis of purified budded virus. This is the first report of the display of the GFP protein or the individual rubella virus spike proteins on the surface of an enveloped virus. Such a eucaryotic viral display system may be useful for the display of proteins dependent on glycosylation for activity and for targeting of recombinant baculoviruses to novel host cell types as a gene transfer vehicle.
Amino Acid Sequence↗
Effect of brefeldin A on rotavirus assembly and oligosaccharide processing.
Rotavirus is one of very few viruses that utilizes the endoplasmic reticulum (ER) for maturation. The maturation process is unique not only because it involves translocation of subviral particles across the ER membrane, but also because mature virus is thought to be retained in the ER until cell lysis. Brefeldin A (BFA) is a compound that blocks protein export from the ER to the Golgi complex and causes disruption of the Golgi complex with relocation of resident Golgi proteins to the ER. We found that BFA had a pronounced effect on rotavirus assembly and oligosaccharide processing. Single-step growth experiments demonstrated that BFA reduced infectious progeny rotavirus yield by 99.9%. Immunohistochemical staining with monoclonal antibodies showed that all examined VP4, VP6, VP7, and NS28 epitopes remained unaffected by BFA. A novel observation from pulse-chase experiments was that BFA-treatment rapidly increased the molecular weight of the ER-associated VP7 followed by endo-beta-N-acetylglucosaminidase H (endo H) resistance. A novel observation was also that the trans-ER NS28 protein remained endo H sensitive through the course of BFA-treatment, but that the molecular weight varied during chase. Electron microscopy analysis revealed that BFA interfered in the transition from the intermediate enveloped particle to the mature double-shelled virus.
Amino Acid Sequence↗
Evolutionary conservation in the hepatitis B virus core structure: comparison of human and duck cores.
BACKGROUND: Hepatitis B virus is a major human pathogen which has been extensively studied, yet its structure is unknown. Cryo-electron microscopy of the viral cores expressed in Escherichia coli or isolated from infected liver provides a means for determining the structure of the hepatitis B nucleocapsid. RESULTS: Using cryo-electron microscopy and three-dimensional image reconstruction, we have determined the structures of duck and human hepatitis B virus cores and find that they have similar dimer-clustered T = 3 and T = 4 icosahedral organizations. The duck virus core protein sequence differs from the human in both length and amino acid content; however, the only significant structural differences observed are the lobes of density on the lateral edges of the projecting (distal) domain of the core protein dimer. The different cores contain varying amounts of nucleic acid, but exhibit similar contacts between the core protein and the nucleic acid. Immunoelectron microscopy of intact cores has localized two epitopes on the core surface corresponding to residues 76-84 and 129-132. CONCLUSIONS: The bacterial expression system faithfully reproduces the native hepatitis B virus core structure even in the absence of the complete viral genome. This confirms that proper assembly of the core is independent of genome packaging. Difference imaging and antibody binding map three sequence positions in the structure: the C terminus and the regions near amino acids 80 and 130. Finally, we suggest that the genome-core interactions and the base (proximal) domain of the core dimer are evolutionarily conserved whereas the projecting domain, which interacts with the envelope proteins, is more variable.
Animals↗
Rotavirus serotypes and electropherotypes in Finland from 1986 to 1990.
Four epidemic seasons of rotaviruses were studied in Helsinki during 1986-1990. This is the first Scandinavian study, where both electropherotypes and serotypes are determined. Out of 5316 fecal specimens 769 (14.5%) rotavirus positive samples were detected by electron microscopy. Of these, 645 isolates (83.9%) gave a clear RNA pattern in gel electrophoresis and they clustered into 87 electropherotypes. An illustrative number of isolates representing each electropherotype (= E-type) was serotyped using VP7 protein-specific monoclonal antibodies for serotypes G1-G4 and without exceptions, within one E-type only a single serotype specificity was found. After establishment of the serotype of each E-type, the distribution of serotypes was scored as 61.2%, 2.0%, 0.5% and 29.8% for G1-G4, respectively; 6.5% remained untypable. Two seasons had one predominant E-type (Season 1, 1986-87, and Season 3, 1988-89, 84.2% and 80.6% of rotavirus positive samples, respectively). Both were followed by a season with no predominant E-type, but several minor E-types. Altogether, 5 short E-types (13/645 samples) with serotype G2 specificity were found, most of them occurring in Season 2. Only 2 E-types (3 samples) belonged to serotype G3. Group C rotavirus was found in 8 specimens. In this study a shift in serotypes, from G1 to G4, was observed in Finland in 1988/89; a similar shift was reported in many European countries at that time.
Child↗
The 6-kilodalton membrane protein of Semliki Forest virus is involved in the budding process.
Alphavirus genomes encode a small hydrophobic protein of 6 kDa (the 6K protein) that is expressed as part of a large polyprotein containing the sequences of the two virus transmembranal glycoproteins which form the spikes of the infectious particle. Although made in amounts equivalent to those of the glycoproteins, very little of the 6K protein is found in secreted infectious virions. The role of this protein in virus replication and structure has been studied by use of a variety of mutationally altered forms of 6K, which yield phenotypically distinct viruses. A complete deletion of the gene encoding the 6K protein (delta 6K) of Semliki Forest Virus (SFV) has been constructed from an SFV infectious cDNA and the transcribed RNA-produced progeny virus that closely resembled the normal virus (P. Liljeström, S. Lusa, D. Huylebroeck, and H. Garoff, J. Virol. 65:4107-4113, 1991). Further studies of this mutant have now been performed, and they show that growth of delta 6K has a strong dependency on its host cell, varying from 2 to 50% of the rate of formation of the wild-type SFV. Mammalian cells are much more defective than insect and avian cells in replication of the delta 6K mutant. This mutant is not defective in formation and transport of the glycoproteins or in production of nucleocapsids, which accumulate at the plasma cell membrane in infected BHK cells. The major defect, thus, is in the final assembly and budding of new virus. In BHK cells infected with the delta 6K strain, a relatively large fraction of the total infectious virus formed can be recovered by osmotic lysis of exhaustively washed cells. Infectious SFV totally lacking 6K is identical to wild-type SFV in the early stages of virus replication, i.e., binding and uptake. The particles themselves are more thermolabile than those of wild-type SFV, suggesting that the 6K protein may be a part of the structure of wild-type virus or that the slower budding leads to an altered configuration of the trimeric spikes. These data support other studies that implicate the 6K protein as an important but nonessential component in the assembly and budding of the alphavirus particle, perhaps by affecting the packing of the glycoproteins and their interactions with membrane lipid.
Animals↗