PubMed Health⌕ Search

Biomedical subjects

C Köhne

Publications and source records attributed to C Köhne.

10 recordsLinked to original sources
PubMed1999

Development of bivalent (B/E) vaccines able to neutralize CCR5-dependent viruses from the United States and Thailand.

Recombinant envelope glycoproteins prepared from a subtype B (MN) strain and a subtype E (CM244) strain of HIV-1 were combined to create a bivalent vaccine (B/E) effective against viruses circulating in the United States and Asia. Combining the two antigens resulted in formulations that increased the breadth and potency of the inter-subtype neutralizing response. Antibodies to the bivalent vaccine formulation neutralized viruses possessing diverse phenotypes, including syncytia-inducing and non-syncytia-inducing primary isolates, viruses using either the CCR5 or the CXCR4 chemokine receptors, and viruses differing in their sensitivity to soluble CD4. These studies demonstrate for the first time that the magnitude and quality of the immune response to HIV-1 can be improved by combining recombinant envelope glycoproteins from different genetic subtypes.

AIDS Vaccines↗
PubMed1999

Secretion of glycosylation site mutants can be rescued by the signal/pro sequence of tissue plasminogen activator.

Strategies that prevent the attachment of N-linked carbohydrates to nascent glycoproteins often impair intracellular transport and secretion. In the present study, we describe a method to rescue the intracellular transport and secretion of glycoproteins mutagenized to delete N-linked glycosylation sites. Site-directed mutagenesis was used to delete N-linked glycosylation sites from a chimeric protein, TNFR-IgG1. Deletion of any of the three glycosylation sites in the TNFR portion of the molecule, alone or in combination, resulted in a moderate or near total blockade of TNFR-IgG1 intracellular transport and secretion. Pulse chase experiments suggested that the glycosylation site mutants accumulated in the endoplasmic reticulum (ER) and were inefficiently exported to the Golgi apparatus (GA). Replacement of the TNFR signal sequence with the signal/pro sequence of human tissue plasminogen activator (tPA) overcame the blockade to intracellular transport, and restored secretion to levels comparable to those achieved with the fully glycosylated molecule. Ligand binding studies suggested that the secreted glycosylation variants possessed binding characteristics similar to the fully glycosylated protein. This study demonstrates that N-terminal sequences of tPA are unexpectedly efficient in facilitating transport from the ER to the GA and suggests that these sequences contain a previously unrecognized structural element that promotes intracellular transport.

Amino Acid Sequence↗
PubMed1996

Purification and characterization of the soluble interleukin-6 receptor from human plasma and identification of an isoform generated through alternative splicing.

The soluble human interleukin-6 receptor (shIL6R) was purified from human plasma. In a single immunoaffinity purification step a 140000-fold enrichment with a yield of 95% was achieved. A subsequent IL-6 affinity chromatography resulted in a homogeneous receptor preparation but only in a yield of less than 5%. The biological activity of the soluble receptor was clearly demonstrated by its ability to induce the synthesis of the acute-phase protein 1-antichymotrypsin in HepG2 cells stably transfected with IL-6. Upon gel filtration, the native shIL6R showed an apparent molecular mass of 93 kDa. Analysis by SDS/PAGE revealed an apparent molecular mass of 65 kDa for the soluble receptor. Deglycosylation with peptide N-glycosidase F led to a shift in molecular mass from 65 kDa to 45 kDa. It has previously been shown that the shIL6R can be generated by shedding the membrane-bound form or by expression of an alternatively spliced mRNA. Here we show that the shIL6R isolated from human plasma is recognized by an affinity-purified peptide antibody raised against an amino acid sequence unique for the alternatively spliced isoform. Thus, the shIL6R isoform generated through alternative splicing which has been previously detected in supernatants of cultured cell lines is also an in vivo product circulating in human plasma.

Alternative Splicing↗
PubMed1996

Soluble receptors for cytokines and growth factors.

Soluble cytokine and growth factor receptors are currently believed to play an important role in the regulation of biological activities of their ligands. In this review, the current ideas on the mechanisms and regulation of generation of soluble receptors and their possible physiological functions are presented. Furthermore, implications of soluble cytokine and growth factor receptors as disease markers and therapeutical agents are summarized and discussed.

Alternative Splicing↗
PubMed1996

Weekly infusional 5-fluorouracil plus/minus other drugs for the treatment of advanced gastric cancer.

Based on preclinical data and the promising results being achieved with infusional 5-FU in colorectal and breast cancer, we investigated a weekly schedule of a 24-hour infusion of 5-FU plus folinic acid (HD-FU/FA) in patients failing to first-line chemotherapy and HD-FU/FA plus cisplatin (C) or plus cisplatin/epidoxorubicin (C/E) in chemo-naive patients with advanced gastric cancer. In all three trials the results achieved with the tested chemotherapy regimens indicated high activity and good tolerability. All three protocols were administered as outpatient treatment. With HD-FU/FA and overall response rate of 24% and a median survival time of 5 months was observed in 17 patients refractory to or relapsing after first-line chemotherapy. HD-FU/FA/C induced an overall response rate of 66% and a median survival time of 13 months. Of note was the high activity of this regimen in patients with malignant ascites. HD-FU/FA/C/E also proved to be an interesting regimen similar active as HD-FU/FA/C but it was subjectively less well tolerated. In patients with locally advanced disease the response rate was 90% (10/11), and in patients with distant metastases 50% (8/16).

Adult↗
PubMed1994

Evidence for a loop-like insertion mechanism of pro-Omp A into the inner membrane of Escherichia coli.

We have studied the insertion of pro-OmpA into the Escherichia coli membrane in vivo using various mutants that have either alterations in the amino-terminal parts of the signal peptide or in the mature region that flanks the signal peptide. A pro-OmpA mutant with an amino terminal extension of 142 residues derived from ribulokinase (AraB) was analysed for its membrane insertion. The AraB portion, which includes a cluster of seven charged residues close to the signal sequence, did not interfere with the Sec components and allowed efficient export of OmpA. During translocation the AraB portion remained in the cytoplasm. Further mutants of OmpA were constructed in the carboxy-terminal region flanking the signal sequence. Pro-OmpA does not translocate across the membrane when a charge cluster, comprised of Lys-Arg-Arg-Glu-Arg, is introduced after positions 5, 11 or 15 of the mature region, but is translocated when the cluster is introduced after position 22. This defines a region of about 20 residues in the mature part of pro-OmpA that is crucial for membrane insertion. These results suggest that in the case of the Sec-dependent pro-OmpA, as with the Sec-independent M13 procoat, the precursor assumes a loop-like structure involving the signal peptide and the early part of the mature region, leaving the amino terminus of the signal peptide at the cytoplasmic face.

Amino Acid Sequence↗
PubMed1988

Direct effects of cholecystokinin on human gastric motility.

For a precise analysis of the cholecystokinin (CCK 8) effects on human stomach, we dissected strips of longitudinal and circular muscle from the fundus, corpus and antrum, and circular muscle from the inner and outer pyloric sphincter and duodenum. Specimens were taken during gastrectomy and from stomachs of kidney donors. Mechanical activity was simultaneously recorded under auxotonic conditions. After CCK 8 application, the following effects were observed: (1) direct excitatory effects of CCK 8 with great regional variations in quality and intensity; (2) increases in amplitude of phasic contractions in the outer plyorus and longitudinal antrum (in the other types of preparations the effects were negligible; (3) increases in tonic activity in preparations of the proximal stomach and in strips of longitudinal muscle form the antrum, and (4) remarkable interindividual differences, with negligible responses in one third of the 24 human stomachs examined.

Acetylcholine↗