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D Peters

Publications and source records attributed to D Peters.

At least 19 recordsLinked to original sources
PubMed1992

The nucleotide sequence of the S RNA of Impatiens necrotic spot virus, a novel tospovirus.

Impatiens necrotic spot virus (INSV) shares a number of properties with tomato spotted wilt virus (TSWV), the type species of the genus tospovirus within the family Bunyaviridae. INSV, however, differs from TSWV in plant host range and serology. In order to define the genomic structure and the taxonomic status of this TSWV-like virus, the nucleotide sequence of its genomic S RNA segment has been determined. The molecular data obtained demonstrate that, like TSWV, INSV has an ambisense S RNA molecule, encoding a non-structural protein in viral sense and the nucleocapsid protein in viral complementary sense. The level of nucleotide sequence homology between their S RNAs, as well as the divergence in amino acid sequence homology of their gene products, confirm previous conclusions from serological studies that INSV and TSWV represent distinct virus species within the newly created genus, tospovirus.

Amino Acid Sequence↗
PubMed1992

An unidentified Toxoplasma-like tissue cyst-forming coccidium in a cat (Felis catus).

An unidentified coccidium was found in the brain and the heart of a 6-year-old female cat. Tissue cysts measured 40-130 x 40-112 microns and contained hundreds of bradyzoites measuring 4.2-5.2 x 1.2-1.8 microns. The cyst wall was 0.26-0.53 microns thick. Tissue cysts reacted positively with anti-Toxoplasma gondii serum but not with anti-Neospora caninum serum in an immunohistochemical test. Ultrastructurally, the cyst was aseptate and contained banana-shaped bradyzoites. Micronemes and rhoptries in bradyzoites were unlike those found in T. gondii bradyzoites. In the unidentified coccidium, the micronemes were arranged in rows and the rhoptries extended from the anterior tip to the posterior end.

Animals↗
PubMed1992

Characterization of RNA-mediated resistance to tomato spotted wilt virus in transgenic tobacco plants.

Recently high levels of protection against tomato spotted wilt virus (TSWV), a negative-strand RNA virus infecting plants, have been obtained by transforming tobacco with viral nucleoprotein (N) gene sequences. Here we demonstrate that this protection is primarily due to the presence of N gene transcripts in the cells of transgenic plants, and hence appears to be RNA-mediated. Further, transgenic tobacco plants are only protected to isolates and strains of TSWV and not to other tospoviruses that share considerable nucleotide sequence homology in their N genes to TSWV. In addition to being protected after mechanical inoculation, the transgenic tobacco plants are also resistant to inoculation using viruliferous thrips, i.e. Frankliniella occidentalis (Perg.), one of the most important natural vector species.

Cell Line, Transformed↗
PubMed1992

Defective interfering L RNA segments of tomato spotted wilt virus retain both virus genome termini and have extensive internal deletions.

Defective interfering (DI) RNA molecules derived from the genomic L RNA segment of tomato spotted wilt virus (TSWV) were generated during sequential passage of the virus at high multiplicity. Characterization of DI RNAs from four distinct isolates by Northern blot analysis and sequence determination revealed that both the 5' and 3' genomic termini were retained in these molecules. Each DI RNA contained a single internal deletion of approximately 60% to 80% of the L RNA segment. All DI RNAs studied maintain an open reading frame (ORF) which suggests that these defective molecules should be translatable by ribosomes. Detection of only defective molecules with ORFs indicates either that association with ribosomes or translation is a prerequisite for the selection and maintenance of replicating DI RNAs, or that the truncated proteins produced play a role in their selection or replication. Analysis of the junction sites in the DI RNAs showed that short nucleotide sequences are repeated, one at the release and another at the reinitiation point on the L RNA. One of these is lost during the generation of the DI molecules. The presence of repeated sequences at the junction sites seems to be unique for tospovirus DI L RNAs; they have not been described for other DI systems of either positive- or negative-strand RNA viruses. A model for TSWV DI RNA generation is proposed in which the viral polymerase can 'jump' across the internal sequences from one secondary structure to another containing the repeated sequences, during the replication of the viral complementary L RNA segment.

Base Sequence↗
PubMed1992

The nucleotide sequence of the M RNA segment of tomato spotted wilt virus, a bunyavirus with two ambisense RNA segments.

The complete sequence of the tomato spotted wilt virus (TSWV) M RNA segment has been determined. The RNA is 4821 nucleotides long and has an ambisense coding strategy similar to that of the S RNA segment. The M RNA segment contains two open reading frames (ORFs), one in the viral sense which encodes a protein with a predicted size of 33.6K, and one in the viral complementary sense which encodes the precursor to the G1 and G2 glycoproteins, with a predicted size of 127.4K. Both ORFs are expressed via the synthesis of subgenomic mRNAs that possibly terminate at a stable hairpin structure, located in the intergenic region. The precursor for the glycoproteins contains a sequence motif (RGD) which is characteristic of cellular attachment domains. Significant sequence homology was found between the G1 glycoproteins of members of the genus Bunyavirus and a corresponding region in the glycoprotein precursor of TSWV, indicating a close evolutionary relationship between these viruses. With the elucidation of the M RNA sequence, the complete nucleotide sequence of TSWV has been determined. TSWV represents the first member of the Bunyaviridae shown to contain two ambisense RNA segments.

Amino Acid Sequence↗
PubMed1992

Viral RNA synthesis in tomato spotted wilt virus-infected Nicotiana rustica plants.

The synthesis of viral RNA species in tomato spotted wilt virus-infected Nicotiana rustica plants was followed in terms of time and relative abundance. Systemic symptoms were visible after 4 days postinoculation (p.i.), but viral (v) and viral-complementary (vc) strands of all three genomic RNA segments [large (L) RNA, medium (M) RNA and small (S) RNA] were detected from 2 days p.i. In addition, two subgenomic mRNAs, derived from S RNA, were detected. For the L RNA segment no subgenomic mRNAs were detected, suggesting that this segment is expressed via the synthesis of a genome-sized vc mRNA. A possible M-specific subgenomic mRNA was detected, showing a similar time course of appearance as the subgenomic mRNAs derived from the S RNA segment. Analysis of cytoplasmic RNA fractions revealed that both v and vc strands of all three genomic segments associate with the nucleocapsid protein into nucleocapsid structures, the vcRNA species being present in lower amounts. Intact, enveloped virus particles contained only the v strand of the L RNA segment and, surprisingly, both v and vc strands of the M and S RNA segment, though in different ratios.

Bunyaviridae↗
PubMed1992

Non-viral heterogeneous sequences at the 5' ends of tomato spotted wilt virus mRNAs.

Subgenomic messenger RNAs transcribed from the tomato spotted wilt virus (TSWV) S RNA segment were partially purified from total RNA extracts of TSWV-infected Nicotiana rustica and analysed by primer extension analysis. The data obtained show the presence of non-viral sequences, 12 to 20 nucleotides in length, at the 5' ends of the N and NSs mRNAs, indicating a cap-snatching mechanism for the initiation of transcription. This is the first report of a plant virus using such a mechanism for transcription of the viral genome.

Plant Viruses↗
PubMed1991

The nonstructural protein (NSs) encoded by the ambisense S RNA segment of tomato spotted wilt virus is associated with fibrous structures in infected plant cells.

The open reading frame located in the viral strand of the ambisense S RNA of tomato spotted wilt virus (TSWV), was cloned into transfer vector pAc33DZ1 and inserted downstream of the polyhedrin promoter in the Autographa californica nuclear polyhedrosis virus genome. Recombinant baculoviruses were obtained that showed a high-level expression of a 52.4-kDa protein corresponding to the inserted TSWV gene. The viral protein thus produced was purified and injected into rabbits to raise antibodies. Western immunoblot analyses of extracts from TSWV-infected plants demonstrated that the 52.4-kDa TSWV-specific polypeptide represents a nonstructural protein (denoted NSs), being absent in purified virus particles. Immunogold labeling of tissue sections of TSWV-infected Nicotiana rustica plants showed that this protein was, depending on the virus isolate, either found dispersed throughout the cytoplasm or associated with fibers which appeared as elongated flexible filaments or paracrystalline rods.

Animals↗
PubMed1991

Generation of envelope and defective interfering RNA mutants of tomato spotted wilt virus by mechanical passage.

During a series of mechanical transfers of tomato spotted wilt virus, two distinct types of mutants were generated. Firstly, a morphologically defective isolate was obtained which had lost the ability to produce the membrane glycoproteins and, as a consequence, was not able to form enveloped particles. Analysis of the genomic RNAs of this isolate suggested that this defect was caused by either point mutations or very small deletions in the medium genomic RNA segment. Secondly, isolates were obtained which had accumulated truncated forms of the large (L) RNA segment. These shortened L RNA molecules most likely represented defective interfering RNAs, since they replicated more rapidly than full-length L RNA and their appearance was often associated with symptom attenuation. Defective L RNAs of different sizes were generated after repeated transfers, and hybridization analysis using L RNA-specific cDNA probes showed that the internal regions deleted varied in length. The presence of defective L RNAs in nucleocapsid fractions as well as in enveloped virus particles indicates that all defective molecules retained the sequences required for replication, encapsidation by nucleocapsid proteins and packaging of the nucleocapsid into virus particles.

Blotting, Northern↗
PubMed1991

Tomato spotted wilt virus L RNA encodes a putative RNA polymerase.

The complete nucleotide sequence of the large (L) genome segment of tomato spotted wilt virus (TSWV) has been determined. The RNA is 8897 nucleotides long and contains complementary 3' and 5' ends, comprising 62 nucleotides at the 5' end and 66 nucleotides at the 3' end. The RNA is of negative polarity, with one large open reading frame (ORF) located on the viral complementary strand. This ORF corresponds to a primary translation product of 2875 amino acids in length, with a predicted Mr of 331,500. Comparison with the polymerase proteins of other negative-strand viruses indicates that this protein most likely represents the viral polymerase. The genetic organization of TSWV L RNA is similar to that of the L RNA segments of Bunyamwera and Hantaan viruses, animal-infecting representatives of the Bunyaviridae.

Amino Acid Sequence↗
PubMed1991

[Comparative studies of the filtration behavior of bacteria and organic particles in porous groundwater conductors. Fundamentals and methods].

In subsurface aquatic environments two groups of micro-organisms are observed: allochthonous bacteria and viruses, which as contaminants are eliminated from water after some time, and autochthonous groundwater micro-organisms, which belong to the natural subsurface environment and may reach very high abundances under favourable conditions--especially in the presence of a high nutrient supply. The migration of micro-organisms is controlled by flow length dependent transport processes (advection--dispersion, adsorption--desorption), and predominantly by filtration. This can be described on the basis of an expanded advection--dispersion concept. The filter effects in a certain porous aquifer can be quantified by the filter efficiency (filter factor) as a measure of the specific decrease of an initial concentration on a certain flow length. Recent laboratory experiments show that for sand the filter factor depends on the respective microbial species and is highly correlated to the effective grain diameter of the porous material, which is routinely determined in hydrogeology. Experiments with columns filled with quartz sand using the bacteria species Escherichia coli ATCC 11229, Pseudomonas cepacia DSM 50181, Streptococcus faecalis ATCC 6569, and polystyrene beads with similar density and diameters show that the filter factor is controlled by the grain size of filter material, the flow velocity, the diameter of the particle and the ionic strength of the water: The filter factor is specific for each microbial species for the same conditions of the aquatic environment. The filter factor decreases one order of magnitude if the flow velocity increases in the same order. A major control of the filter factor is the grain size. Conventionally the grain size is used as characteristic length instead of the pore size which, although it should be the real reference date, is relatively difficult to measure. For the assessment of the filter factor, the grain size d10, taken from the grain size distribution curve, can be used. The influence of the particle diameter on the filter factor, which was predicted by the filtration theory, was confirmed. The minimum values of the filter factor were encountered at particle diameters of about 1 micron, which is about the size of bacteria. The filter factor is influenced strongly by the ionic strength in water with low ionic strength, whereas in water of higher ionic strength its influence can be neglected. These relationships can be formulated into empirical equations, which allow prediction of the filter factor for given hydraulic conditions.

Bacterial Physiological Phenomena↗
PubMed1990

Poliovirus mutants resistant to neutralization with soluble cell receptors.

Poliovirus mutants resistant to neutralization with soluble cellular receptor were isolated. Replication of soluble receptor-resistant (srr) mutants was blocked by a monoclonal antibody directed against the HeLa cell receptor for poliovirus, indicating that the mutants use this receptor to enter cells. The srr mutants showed reduced binding to HeLa cells and cell membranes. However, the reduced binding phenotype did not have a major impact on viral replication, as judged by plaque size and one-step growth curves. These results suggest that the use of soluble receptors as antiviral agents could lead to the selection of neutralization-resistant mutants that are able to bind cell surface receptors, replicate, and cause disease.

Animals↗
PubMed1990

A characterization of epitopes on potato leafroll virus coat protein.

A panel of ten stable hybridoma cell lines secreting monoclonal antibodies (MAbs) specific for potato leafroll virus (PLRV) antigen, was produced in two fusion experiments with murine splenic and myeloma cells. Using different ELISA procedures and Western blotting it was shown that one MAb detected a continuous epitope and nine MAbs reacted with conformation-dependent ones. The conformation-dependent epitopes could be separated into two groups after alkaline treatment of the virions. The MAbs were further differentiated in competitive binding assays. Within the group of MAbs reacting with epitopes not sensitive to alkaline degradation, only two MAbs were directed to the same epitope. The MAbs detecting epitopes formed by the quaternary protein structure or by a protein subunit configuration sensitive to alkaline degradation, displayed positive cooperative binding among each other. In total, a minimum number of nine different, but overlapping, epitopes on the PLRV coat protein could be revealed. The immune response to PLRV antigen in rabbit appeared to be directed mainly towards epitopes recognized by three MAbs. Most MAbs displayed heterologous reactivity to other luteoviruses, i.e., tomato yellow top virus (TYTV), beet western yellow virus (BWYV), beet mild yellowing virus (BMYV), bean leafroll virus (BLRV), and different strains of barley yellow dwarf virus. Three MAbs solely reacted with PLRV and TYTV. Six MAbs gave different reaction patterns in these tests; one of these MAbs differentiated BMYV from BWYV, and another detected a common epitope on PLRV and BLRV, a serological relationship not reported previously to our knowledge.

Animals↗
PubMed1990

Detection of tomato spotted wilt virus using monoclonal antibodies and riboprobes.

The immunoreactivity of a panel of monoclonal antibodies raised to tomato spotted wilt virus (TSWV) was examined in enzyme-linked immunosorbent assays (ELISA) and dot immunobinding assays (DIBA) procedures. MAbs 6.12.15 and 2.9 were specific for the nucleocapsid protein of TSWV. The sensitivity of the two immunoassays was compared with that of a dot-blot hybridization technique using riboprobes (RNA transcripts) to TSWV M RNA. Using deproteinized plant extracts or purified virus preparations, as little as 1 pg RNA could be detected. Although an ELISA using MAb 6.12.15, a DIBA procedure using MAb 3.22.6 and the dot-blot hybridization, detected several TSWV isolates in different host species equally well, the ELISA was most precise and most suitable for routine diagnosis in the field.

Animals↗
PubMed1990

Serological differentiation of 20 isolates of tomato spotted wilt virus.

Twenty tomato spotted wilt virus (TSWV) isolates were serologically compared in ELISA employing five different procedures using a rabbit polyclonal antiserum against nucleocapsid proteins (NuAbR) and mouse monoclonal antibodies (MAbs), two directed to nucleocapsid proteins (N1 and N2) and four directed to glycoproteins G1 to G4. All the antisera were raised against TSWV-CNPH1. The 20 isolates were differentiated into two distinct serogroups. Serogroup I consisting of 16 isolates strongly reacted with NuAbR. The other four isolates were poorly recognized by NuAbR and were placed in another serogroup, designated II. The panel of MAbs differentiated the TSWV isolates into three serotypes. The 16 isolates forming serogroup I reacted strongly with the MAbs generated and were identified as serotype I isolates. The four isolates which made up serogroup II were split into serotypes II and III. The serotype II isolates did not respond or responded poorly with MAbs N1, N2 and G3. The two other isolates placed in serotype III were recognized by N1 but not by N2 and G3. Two isolates became defective after several mechanical passages and failed to respond or responded very poorly with MAbs directed to glycoproteins. Our results show that ELISA employing polyclonal and monoclonal antisera is a useful tool to differentiate TSWV isolates and to detect defective forms. The results also strongly suggest that TSWV nucleocapsid proteins are less conserved than the glycoproteins.

Antibodies, Monoclonal↗