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Biomedical subjects

A Klimov

Publications and source records attributed to A Klimov.

33 records · Page 2Linked to original sources
PubMed1999

Recombinant influenza A virus vaccines for the pathogenic human A/Hong Kong/97 (H5N1) viruses.

Recombinant reassortment technology was used to prepare H5N1 influenza vaccine strains containing a modified hemagglutinin (HA) gene and neuraminidase gene from the A/Hong Kong/156/97 and A/Hong Kong/483/97 isolates and the internal genes from the attenuated cold-adapted A/Ann Arbor/6/60 influenza virus strain. The HA cleavage site (HA1/HA2) of each H5N1 isolate was modified to resemble that of "low-pathogenic" avian strains. Five of 6 basic amino acids at the cleavage site were deleted, and a threonine was added upstream of the remaining arginine. The H5 HA cleavage site modification resulted in the expected trypsin-dependent phenotype without altering the antigenic character of the H5 HA molecule. The temperature-sensitive and cold-adapted phenotype of the attenuated parent virus was maintained in the recombinant strains, and they grew to 108.5-9.4 EID50/mL in eggs. Both H5N1 vaccine virus strains were safe and immunogenic in ferrets and protected chickens against wild-type H5N1 virus challenge.

Amino Acid Sequence↗
PubMed1998

Characterization of an avian influenza A (H5N1) virus isolated from a child with a fatal respiratory illness.

An avian H5N1 influenza A virus (A/Hong Kong/156/97) was isolated from a tracheal aspirate obtained from a 3-year-old child in Hong Kong with a fatal illness consistent with influenza. Serologic analysis indicated the presence of an H5 hemagglutinin. All eight RNA segments were derived from an avian influenza A virus. The hemagglutinin contained multiple basic amino acids adjacent to the cleavage site, a feature characteristic of highly pathogenic avian influenza A viruses. The virus caused 87.5 to 100 percent mortality in experimentally inoculated White Plymouth Rock and White Leghorn chickens. These results may have implications for global influenza surveillance and planning for pandemic influenza.

Amino Acid Sequence↗
PubMed1996

[Carotid endarterectomy based on preoperative duplex ultrasound].

Carotid endarterectomy is the most common vascular procedure. Recent studies have suggested that carotid endarterectomy can be performed safely, based solely on ultrasound duplex evaluation in selected patients. We evaluated 12 men and 8 women who underwent carotid endarterectomy, 12 for significant symptomatic disease and 8 for tight, asymptomatic stenosis of the carotid artery. All had duplex ultrasound scans without angiography before operation. They all survived. 2 had hoarseness due to vocal cord paralysis which resolved 5 months later in 1, while in the other it still persisted 2 months after operation. There were no other neurologic complications. During follow-up all have remained symptom-free. We conclude that clinical assessment of carotid artery stenosis with duplex ultrasound scan of good technical quality provides appropriate information on which to base carotid endarterectomy, and is a safe alternative to preoperative angiography.

Aged↗
PubMed1995

Beware of absent femoral pulse (or how to prevent major complications after minor procedures).

The following is presented to illustrate the importance of examining all peripheral pulses, especially the femoral pulse, before performing minor surgical procedures on the lower extremity, even limited toe amputation. This simple examination is a must in identifying patients at risk for severe peripheral arterial insufficiency, which can lead to major complications if underestimated or undiagnosed. We offer three examples to illustrate this point. All patients underwent successful revascularization and major lower limb amputation was avoided.

Aged↗
PubMed1992

Subtype H7 influenza viruses: comparative antigenic and molecular analysis of the HA-, M-, and NS-genes.

Antigenic analysis of the haemagglutinin and matrix protein with corresponding sets of monoclonal antibodies as well as sequence analysis of HA-, M-, and NS-genes were carried out to establish antigenic and genetic relationships between four fowl plague virus (FPV) strains of H7 subtype. The data obtained revealed close genetic relatedness between the oldest known influenza A virus, A/chicken/Brescia/1902 (H7N7), and two FPV strains, A/FPV/Dobson (H7N7) and A/FPV/Weybridge (H7N7). These three strains apparently differ in all genes investigated from the A/FPV/Rostock isolate.

Amino Acid Sequence↗
PubMed1991

Further studies on cold adapted variants of human influenza virus A/Krasnodar/101/59 (H2N2) with special reference to genetic stability of attenuation markers.

A previously described cold adapted (ca) attenuated virus, K/25, derived from parent strain A/Krasnodar/101/59 (H2N2), was further modified by 35 additional passages in chick embryos at suboptimal temperature. The virus obtained had retained a distinct ts and ca phenotype and some other markers of attenuation but differed from formerly isolated ca variants by its higher genetic stability connected with an increased growth capacity in chick embryos.

Animals↗
PubMed1988

Nucleotide sequence of RNA segment 7 and the predicted amino sequence of M1 and M2 proteins of FPV/Weybridge (H7N7) and WSN (H1N1) influenza viruses.

Since the gene products (M1 and M2) of influenza virus RNA segment 7 have been implicated in host range restriction, sensitivity to the drug amantadine, virus yield in chicken embryos as well as in virus assembly and morphology, we have determined the nucleotide sequence of this RNA segment for an avian [A/FPV/Weybridge (H7N7)] and a human [A/WSN/33 (H1N1)] virus and compared it to that of the other influenza A virus strains. The results show that all ten strains of influenza A virus contain an identical number of nucleotides (1027 bases) in RNA segment 7 and an identical number of amino acids in M1 (252 aa) and M2 (97 aa) proteins. The observed amino acid changes are conservative in nature suggesting the requirement of a critical structure of both proteins in virus assembly. Furthermore, the presence of some consistent amino acid substitutions among different human and avian strains also supports the possible existence of host range and drug resistance determinants in M1 and M2 proteins.

Amino Acid Sequence↗
PubMed1986

Comparative studies of wild-type and cold-mutant (temperature-sensitive) influenza virus: detection of mutations in all genes of the A/Ann Arbor/6/60 (H2N2) mutant vaccine donor strain.

Direct biochemical evidence has been obtained for the existence of mutations in all eight RNA segments of the A/Ann Arbor/6/60 cold-adapted (ca) mutant influenza virus strain as compared with its wild-type (wt) progenitor. Polyacrylamide gel electrophoresis (PAGE) of viral RNA revealed a change in the electrophoretic migration of RNA 2 (PB1). T1 oligonucleotide mapping revealed changes in two polymerase genes (the PB2 and PA genes), the hemagglutinin (HA) gene and the nucleoprotein (NP) gene. Analysis of S1 nuclease-treated RNA hybrids on polyacrylamide gels detected changes in the HA and neuraminidase (NA) genes. Partial DNA sequence analysis demonstrated a base sequence change in the matrix (M) protein gene that predicts an amino acid change in the M2 protein and a silent mutation in the non-structural (NS) protein gene. In addition, analysis of viral polypeptides by PAGE has so far revealed changes in the viral protein, PA. These findings directly demonstrate the existence of multiple mutations in the ca vaccine strain, a property that may provide reliably and stably attenuated vaccines that derive their six internal genes from the ca A/Ann Arbor/6/60 donor strain.

Genes, Viral↗
PubMed1981

Genome analysis of influenza A virus strains isolated during an epidemic of 1979-1980.

The genome and polypeptides of influenza A virus H3N2 strains isolated during the epidemic of 1979-1980 in the U.S.S.R. and G.D.R. have been analysed. Five varieties of H3N2 strains differing in a number of genes have been found. The isolates of the first group was similar to the A/Texas/1/77 strain in all the genes; the isolates of the second group were similar to the A/Bangkok/1/79 strain in all the genes; the strain representative of the third variety, contained all the genes except gene 4 close to those of the A/Bangkok/1/79 strain; the isolates of the fourth group contained genes 7 and 8 similar to those of the A/Bangkok/1/79 strain while the other genes corresponded to those of no strains under comparison; the viruses of the fifth group contained gene 3 similar to that of A/Moscow/406/76 strain, gene 7 was similar to that of A/Texas/1/77 strain and the other genes differed from all other strains compared. The data obtained indicate that during an influenza epidemic occurring in certain region several influenza virus varieties of the same serotype can circulate simultaneously, differing not only in the antigenic specificity of the haemagglutinin, but also in other genes.

Disease Outbreaks↗
PubMed1979

Investigation of recombinants of human influenza and fowl plague viruses.

Recombinants of human influenza type A viruses, A/Krasnodar/101/1959 (H2N2) or A/Habarovsk/15/1976 (H3N2), and fowl plague virus (FPV), strain Weybridge (Hav1Neq1) were obtained. The genome of the recombinant obtained by recombination of influenza A/Habarovsk/15/1976 virus and FPV contained the genes 4 (HA) and 6 (NA) derived from the influenza A/Habarovsk virus and all the other genes [1, 2, 3, 5 (NP), 7 (M), 8 (NS)] from FPV. The genome of the recombinant of A/Krasnodar/101/1959 virus and FPV contained the genes 2, 4 (HA) and 6 (NA) derived from influenza A/Krasnodar virus and all the other genes [1, 3, 5, (NP), 7 (M), 8 (NS)] from FPV. The recombinants, like FPV, gave high virus yields in chick embryos and could multiply at high temperatures (40 and 42 degrees C), but, like human influenza viruses, were non-pathogenic for chickens and did not replicate in chick embryo fibroblast culture, but did replicate in a human conjunctiva cell line, clone 1-5C-4. The virion transcriptase of the recombinants, in a number of properties determined in vitro, was similar to FPV transcriptase but not to the human influenza virus enzyme.

Animals↗
PubMed1979

Replication of two influenza virus strains and a recombinant in HEF and LEP cells.

The replication of influenza viruses A/NWS-D, A/WS-MK and their r12 recombinant in human embryo fibroblast (HEF) and human diploid fibroblast (LEP) cell lines was studied. In HEF cells virus NWS-D and recombinant r12 induced synthesis of virus-specific macromolecules and produced infectious virions; virus WS-MK induced synthesis of virus complementary RNA (cRNA), virion RNA (vRNA), protein, RNP and non-infectious virions, but haemagglutinin cleavage was impaired and the virions formed contained uncleaved haemagglutinin. In LEP cells, infectious virions were formed only by virus NWS-D; viruses WS-MK and r12 induced synthesis of virus cRNA, vRNA, proteins and RNP; virus r12 had the haemagglutinin cleaved, whereas in virus WS-MK this process was impaired; neither virus WS-MK nor r12 was capable of forming virions. Analysis of the recombinant r12 genome showed that it had only inherited a single gene from NWS-D, the one coding for neuraminidase, having inherited all others (P1, P2, P3, HA, NP, M, NS) from WS-MK. The data obtained suggested that the inability of virus WS-MK to form infectious virions in HEF cells is due to the character of its neuraminidase, which is incapable of participating in haemagglutinin cleavage. The deficient reproduction of this virus in the other host-cell system (LEP) is apparently associated with some characteristics of another protein (other proteins) of this virus.

Animals↗