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Biomedical subjects

T Kos

Publications and source records attributed to T Kos.

6 recordsLinked to original sources
PubMed1992

Hepatitis C virus antibody detection by a line immunoassay and (near) full length genomic RNA detection by a new RNA-capture polymerase chain reaction.

A rapid and simple RNA-capture polymerase chain reaction assay (RCPA) for detection of hepatitis C virus (HCV) is described. The assay detects specifically the presence of (near) full length genomic RNA of HCV by capturing HCV-RNA at the 3' terminal end on magnetic beads, followed by cDNA synthesis and PCR with 5' end specific primers. Sera were obtained from 30 chimpanzees inoculated with non-A, non-B hepatitis material from various sources, 28-122 months after infection. The sera were tested for the presence of HCV-RNA by RCPA and for HCV antibodies by a Line ImmunoAssay (Inno-LIA HCV Ab). Both tests were compared and show a high degree of agreement. Screening of 30 chimpanzee sera revealed either clearing of the virus below detection level (22/30) or development of a HCV carrier state (8/30). Only 1 of 11 LIA-indeterminate samples was positive by RCPA. As the RCPA is more sensitive, it can be used to test for the presence of HCV in sera which are classified indeterminate by the LIA. The outcome of the infection seems to be independent of the nature of the inocula, suggesting that the individual immune response could determine either clearing of the virus or the development of chronic infection.

Animals↗
PubMed1991

Hepatitis delta virus cDNA sequence from an acutely HBV-infected chimpanzee: sequence conservation in experimental animals.

Hepatitis delta virus (HDV) RNA was isolated from the serum of a chimpanzee acutely infected with hepatitis B virus (HBV) and superinfected with HDV. Interference of HDV with HBV resulted in decreased HBV DNA levels in the serum. This interference did not change the size of the two HBV specific RNAs present in the liver of the chimpanzee. The complete cDNA sequence of the HDV RNA (5th passage) was determined. Comparison of this cDNA sequence with our previously published sequence (4th passage), located in the variable domain of HDV, was highly conserved. The HDV strain used for these infections originated from a human HDV isolate also used for five to seven HDV passages in chronic HBV carrier chimpanzees (subtypes adw and ayw) or woodchucks chronically infected with woodchuck hepatitis virus (WHV). The complete HDV cDNA sequence showed an extreme conservation (up to 99.8% homology) with the previously published animal-derived HDV cDNA sequences irrespective of passage number and animal species. In contrast a markedly lower homology (85-89%) was found when compared with 3 human-derived HDV cDNA sequences. Comparison of our complete cDNA sequence with the human-derived cDNA sequences showed that the nucleotide changes in the human-derived isolates were restricted to specific regions on the genome and to specific basepair substitutions. The hepatitis Delta antigen (HDAg) is highly conserved both in the human- and animal-derived cDNA sequences showing mainly conservative amino acid changes.

Acute Disease↗
PubMed1991

Baculovirus-directed high level expression of the hepatitis delta antigen in Spodoptera frugiperda cells.

The hepatitis delta antigen (HDAg) is a multifunctional protein. It forms the core-like structure of the hepatitis delta virus (HDV) but also enhances replication of HDV in the nucleus of the hepatocyte. A cDNA fragment encoding HDAg was inserted adjacent to the polyhedrin promoter of Autographa californica nuclear polyhedrosis virus present in the baculovirus transfer vector pVL941. After transfection of Spodoptera frugiperda (Sf9) cells a recombinant baculovirus Ac delta 1 was isolated and purified using filter hybridization techniques. Sf9 cells infected with Ac delta 1 express the HDAg as a non-fused, non-glycosylated protein with an abundance of up to 25% of the total cellular protein mass. Immunoblot analysis using a human polyclonal anti-HD conjugate identified a 22K and a 24K protein in the nucleus of Ac delta 1-infected Sf9 cells. Electron microscopic studies using immunogold labelling showed that the recombinant HDAg (recHDAg) was associated with the hetero-chromatin of the Sf9 cells. The recHDAg produced by Sf9 cells elicited anti-HD antibodies in chimpanzees when injected intramuscularly.

Animals↗
PubMed1988

Nucleotide sequence of the Aspergillus niger trpC gene: structural relationship with analogous genes of other organisms.

The nucleotide sequence of the Aspergillus niger tryptophan C (trpC) gene was determined. Northern hybridization and S1-mapping experiments showed the presence of a 2.6 kb trpC poly(A)+ RNA with two very short (5 and 6 nucleotides) noncoding 5'-regions. Comparison of the predicted amino acid sequence with that of trp gene proteins of pro- and eukaryotic organisms revealed three functional domains (G, C, F) in the A. niger TrpC protein which catalyse the glutamine amidotransferase reaction (GAT), the indole-3-glycerol phosphate synthase reaction (IGPS) and the N-(5'-phosphoribosyl) anthranilate isomerase reaction (PRAI), respectively. These domains are highly conserved and bordered by short areas showing less homology. Within the F domain of the trpC gene in A. niger, A. nidulans and Neurospora crassa, a region encoding 30 amino acids was found which is absent in the analogous genes of Saccharomyces cerevisiae and prokaryotic organisms. This region has features of a mutated in-phase intron.

Amino Acid Sequence↗
PubMed1986

The purification and characterization of rat gamma interferon by use of two monoclonal antibodies.

Two mouse monoclonal antibodies, designated DB-1 and DB-2, were isolated and used for the purification and characterization of recombinant rat interferon gamma (rRIF-gamma) derived from Chinese hamster ovary (CHO) cells. The two antibodies belong to different classes (DB-1 is an IgG1 and DB-2 an IgA) and display similar epitope specificities as shown in competition binding experiments. Both antibodies, raised against rRIF-gamma, exhibited high affinity for rat and mouse gamma interferon and efficiently neutralized the antiviral activity of both animal interferon species. Affinity chromatography analysis showed that a column with immobilized DB-1 was capable of complete binding of rat and mouse gamma interferon, both natural and recombinant DNA-derived. As visualized by SDS-polyacrylamide gel electrophoresis and Western blot analysis, the purified rRIF-gamma preparation consisted of at least seven molecular forms with Mr values ranging between 14 000 and 25 000, with a relative abundance of a 18 000 Mr protein. Gel permeation chromatography of crude rRIF-gamma gave coincident peaks of rRIF-gamma proteins (all different forms) and interferon activity corresponding to a Mr value of 45 000. The results suggest that the molecular heterogeneity was due to differential glycosylation and was not the consequence of a proteolytic degradation process.

Animals↗