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O V Nikolaeva

Publications and source records attributed to O V Nikolaeva.

17 recordsLinked to original sources
PubMed1997

Modulation of the antigenic reactivity of the citrus tristeza virus coat protein.

Trapping properties of a panel of monoclonal antibodies (Mabs) raised against citrus tristeza virus (CTV) were analyzed in an indirect double-antibody sandwich ELISA (I-DAS-ELISA). These antibodies had been previously assigned by serological specificity into five groups (I to V). Mabs from group V, which are directed to conformational epitopes, trapped significant amounts of virus antigen from CTV-infected plant tissue at IgG concentration above 10 ng/ml. Mabs from groups I to IV, which are directed to linear, continuous epitopes, performed poorly as coating antibodies, even at a 1 microgram/ml concentration of the IgG's, indicating that the respective linear epitopes were inaccessible. However, when Mabs from groups I to IV were combined with a small amount of Mabs from group V, a substantial increase in trapping of the CTV antigen was recorded. In this 'two antibody-binding assay' previously cryptic, linear epitopes of the CTV CP apparently became accessible to the Mabs from groups I to IV. Modulation of the antigenic reactivity of the CTV CP was also recorded upon binding of the Mabs directed to the conformational epitopes in solution. Induced exposure of the linear epitopes of the CTV CP was revealed in 'two antibody-binding assays' with pairwise combinations of different mouse Mabs and several rabbit and chicken polyclonal antisera with different serological specificities, including antisera to bacterially expressed CP fragments. This mixed coating in I-DAS-ELISA resulted in substantially increased efficiency of the virus antigen trapping by antisera produced against bacterially expressed protein fragments and an increased sensitivity of the CTV detection after optimization of the ratio between conformational and linear antibodies.

Antibodies, Viral↗
PubMed1996

Organization of the 3'-terminal half of beet yellow stunt virus genome and implications for the evolution of closteroviruses.

The 3'-terminal half of the beet yellow stunt virus (BYSV) genome 10,545 nt, has been cloned and sequenced. The sequenced portion of the BYSV genome encompasses 10 open reading frames (ORFs) and 241 nt of the 3' untranslated region. The sequence spans, in the 5' to 3' direction, the C-terminal region of the replication-associated polyprotein gene (ORF 1a) which includes the set of motifs typical of helicases (HEL), the entire 53-kDa polymerase (RdRp) gene (ORF 1b), and genes encoding 30-kDa (ORF 2), 6-kDa (ORF 3), 66-kDa (ORF 4), 61-kDa (ORF 5), 25-kDa (ORF 6), 23.7-kDa (coat protein, CP) (ORF 7), 18-kDa (ORF 8), and 22-kDa (ORF 9) proteins. The double-stranded RNA "replicative form" of the BYSV was demonstrated to have a nontemplate G residue at the 3' terminus of the (+) strand. The RdRp of BYSV is presumably expressed via a +1 ribosomal frameshift. The five-gene module conserved among closteroviruses was identified in BYSV; it includes a gene array coding for a 6-kDa small hydrophobic protein, a 66-kDa homolog of the cellular HSP70 heat shock proteins, a 61-kDa protein, and a 25-kDa diverged copy of the CP followed by the CP gene itself. Phylogenetic analysis of the replication-associated HEL and RdRp domains as well as proteins from the five-gene module demonstrated the closest relationship between BYSV and two other closteroviruses, beet yellows (BYV) and citrus tristeza (CTV) viruses. Like CTV, the BYSV genome contains a 30-kDa protein gene between the RdRp and the 6-kDa protein genes, and like BYV it has only two genes downstream of the CP gene. The organization of the BYSV genome appears to be intermediate between BYV and CTV, which suggests that these three viruses might represent three distinct but probably close stages in the closterovirus evolution.

Amino Acid Sequence↗
PubMed1995

Complete sequence of the citrus tristeza virus RNA genome.

The sequence of the entire genome of citrus tristeza virus (CTV), Florida isolate T36, was completed. The 19,296-nt CTV genome encodes 12 open reading frames (ORFs) potentially coding for at least 17 protein products. The 5'-proximal ORF 1a starts at nucleotide 108 and encodes a large polyprotein with calculated MW of 349 kDa containing domains characteristic of (from 5' to 3') two papain-like proteases (P-PRO), a methyltransferase (MT), and a helicase (HEL). Alignment of the putative P-PRO sequences of CTV with the related proteases of beet yellows closterovirus (BYV) and potyviruses allowed the prediction of catalytic cysteine and histidine residues as well as two cleavage sites, namely Val-Gly/Gly for the 5' proximal P-PRO domain and Met-Gly/Gly for the 5' distal P-PRO domain. The autoproteolytic cleavage of the polyprotein at these sites would release two N-terminal leader proteins of 54 and 55 kDa, respectively, and a 240-kDa C-terminal fragment containing MT and HEL domains. The apparent duplication of the leader domain distinguishes CTV from BYV and accounts for most of the size increase in the ORF 1a product of CTV. The downstream ORF 1b encodes a 57-kDa putative RNA-dependent RNA polymerase (RdRp), which is probably expressed via a +1 ribosomal frameshift. Sequence analysis of the frameshift region suggests that this +1 frameshift probably occurs at a rare arginine codon CGG and that elements of the RNA secondary structure are unlikely to be involved in this process. The complete polyprotein resulting from this frameshift event has a calculated MW of 401 kDa and after cleavage of the two N-terminal leaders would yield a 292-kDa protein containing the MT, HEL, and RdRp domains. Phylogenetic analysis of the three replication-associated domains, MT, HEL, and RdRp, indicates that CTV and BYV form a separate closterovirus lineage within the alpha-like supergroup of positive-strand RNA viruses. Two gene blocks or modules can be easily identified in the CTV genome. The first includes the replicative MT, HEL, and RdRp genes and is conserved throughout the entire alpha-like superfamily. The second block consists of five ORFs, 3 to 7, conserved among closteroviruses, including genes for the CTV homolog of HSP70 proteins and a duplicate of the coat protein gene. The 3'-terminal ORFs 8 to 11 encode a putative RNA-binding protein (ORF 11), and three proteins with unknown functions; this gene array is poorly conserved among closteroviruses.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1994

Screening of the closterovirus genome by degenerate primer-mediated polymerase chain reaction.

The genome of beet yellows virus (BYV), the type representative of the closterovirus group, encodes a homologue of the cellular heat-shock protein (HSP) 70 family. A pair of degenerate primers targeted to motifs A and E, which are highly conserved in HSP70s, was synthesized. Genomes of several definite and possible members of the closterovirus group were screened for the presence of the HSP70 gene with PCR using these degenerate primers. BYV, citrus tristeza virus (CTV), beet yellow stunt virus (BYSV) and carnation necrotic fleck virus templates produced 1 kb amplification products, which were shown by sequencing to represent fragments of the respective HSP70 genes. Further screening was performed with an additional degenerate primer targeted to the motif IV of the putative viral polymerase. This degenerate primer and specific primers complementary to the 5' region of the HSP70 genes of the respective viruses were used to estimate the distance between polymerase motif IV and the start point of the HSP70 gene for BYV (approximately 1.1 kb), CTV and BYSV (around 2.0 kb) by PCR. The amplified genome regions of CTV (3026 nucleotides) and BYSV (2837 nucleotides) were cloned and sequenced. CTV and BYSV were found to encode the gene for an additional 30K (BYSV) or 33K (CTV) protein between the polymerase and the small hydrophobic protein genes, which was absent in BYV. These two 30K proteins displayed very weak similarity to each other, unlike the highly conserved polymerases, hydrophobic proteins and HSP70s of BYV, CTV and BYSV. Degenerate primer-mediated PCR proved to be an efficient tool for rapid screening and subsequent cloning of the viral genomes.

Base Sequence↗
PubMed1988

[Secretory immunoglobulin of the stomach in patients with chronic gastritis].

The determination of the level of secretory IgA by a method of radial immunodiffusion after Mancini in the gastric juice of 48 patients with chronic gastritis in correlation with the status of the gastric mucosa, the level of acidification and the phase of exacerbation has shown diagnostic potentialities of the method. The highest IgA level was detected in patients with "rearrangement" gastritis and in patients with sharply suppressed gastric secretion. In marked atrophy of the gastric mucosa IgA secretion was significantly lowered. The period of remission was attended by a decrease in IgA secretion as compared with the phase of exacerbation.

Gastric Juice↗
PubMed1981

[Interferon-inducing and antiviral activity of levamisole].

It was shown that levamisol administered orally to mice induced production of interferon with its maximum level in 4-6 hours and prolonged subsequent circulation in the host (the observation period of 5 days). Antiviral activity of levamisol in experimental forest-spring encephalitis was shown (protection of 35-40 per cent). When levamisol were used in combination with polyguacyl, an additive effect was recorded.

Administration, Oral↗
PubMed1980

[Combined use of isoprinosine and an interferon inducer in experimental viral infection].

It was shown for the first time that isoprinosine has an antiviral effect in treatment of experimental forest-spring encephalitis. The combined use of isoprinosine with mouse interferon in treatment of the infected albino mice potentiated antiviral effect as compared to the effect of substances used alone. In addition, the combined use of isoprinosine and interferon inductor in minimum nontoxic amounts resulted in a 4--8 fold increase in the titers of the serum interferon and a statistically significant increase in the mouse resistance to the viral infection. It was found that the efficacy of the combined use of isoprinosine and mouse interferon or interferon inductor increased, when the interval between the drug administrations was prolonged up to 24 hours. The maximum effect providing 75 per cent protection of the animals from the viral infection and an increase in the average life span of the mice from 7.9 to 17.4 days was observed with the combined use of isoprinosine and interferon inductor.

Animals↗
PubMed1980

[Biological activity of a new Soviet natural inducer, double-stranded RNA].

Antiviral activity of a two-spiral RNA (ts RNA), a new natural interferon inductor was studied. It was shown that ts RNA extracted from a phage infected E. coli culture was an active inductor of interferon and resistance to infection with the forestspring encephalitis virus experimental animals. In experiments on 10-12 g mice ts RNA administered in a dose of 50 micrograms/mouse 6 hours after the infection induced up to 1280 units/ml of the serum interferon. When the inductor was administered repeatedly, the experimental animals developed hyporeactivity resulting in a marked decrease in interferon production after the 3rd subsequent injection. The most pronounced effect with respect to the forest-spring encephalitis virus was observed when the inductor was administered intraperitoneally in a dose of 20 micrograms/mouse 4 hours before the infection. The protective effect was less pronounced when the inductor was administered 24 and 48 hours before the infection. A two-fold administration of the inductor did not increase the antiviral effect. When the inductor was administered in a dose of 100 micrograms 14 days before the infection, the animals showed an increase in the nonspecific resistance to the infection resulting in a marked antiviral effect.

Animals↗
PubMed1977

Comparison of interferon-inducing activities and antiviral effects of tobacco mosaic virus, tilorone and sodium nucleinate.

Endogenous interferon was produced in animals in response to the administration of tobacco mosaic virus (TMV), tilorone and sodium nucleinate. The relationship between interferon production and the kind of inducer and the route of its administration was studied. TMV was completely innocuous for Macaca rhesus monkeys and mice and caused no untoward effects in humans upon peroral administration. TMV, tilorone and sodium nucleinate given per os exerted a marked protective effect in mice against tick-borne encephalitis, eastern and western equine encephalomyelitis and influenza virus infections.

Administration, Oral↗
PubMedDate not supplied

[Effect of prolonged storage times on the infectivity of lyophilized arboviruses].

Lyophilized arboviruses of the following taxonomic groups: alfaviruses, flaviviruses, Bunyamwera supergroup viruses, as well as arenaviruses were used in the study. These viruses had been stored for a long time at --20 degree C. Determinations of the infectious titers in suckling mice showed that in a period of over 10 years (up to 21 years) no complete loss of infectivity occurred in any virus groups.

Animals↗
PubMedDate not supplied

[Interferon-inducing and antiviral activity of dsRNA of yeast origin].

The paper describes derivation of double-stranded RNA from K plasmid of Sachcaromyces cerevisiae yeast by means of electrophoresis in agar gel and by differential salting out with 4 M lithium chloride. Studies in vitro and in vivo demonstrated a high interferon-inducing and antiviral activity of dsRNA preparations from the yeast plasmid.

Animals↗