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Biomedical subjects

K Korn

Publications and source records attributed to K Korn.

At least 19 recordsLinked to original sources
PubMed2001

[Detection of hepatitis C virus RNA in tear film of a patient with recurrent peripheral corneal ulcers].

BACKGROUND: There are conflicting reports on the role of hepatitis C virus in corneal pathology. PATIENT: A 58-year-old male patient presented with recurrent peripheral corneal ulcers and corneal thinning in the left eye. There was a bilateral vascular pannus formation and a decreased ocular wetting measured by Schirmer testing. The posterior ocular segment was normal. There was no sign of any systemic rheumatic disease. Serological testing detected antibodies against hepatitis C virus. Hepatitis C virus RNA testing using a quantitative polymerase chain reaction method revealed hepatitis C virus RNA in serum (> 3.2 million copies/ml) and in tear samples (18,000 copies/ml) of the patient. In a control group of 7 consecutive patients with hepatitis C virus RNA detection in the serum but without ocular pathology, no hepatitis C virus RNA was detected in tear samples (detection limit: 1000 copies/ml). CONCLUSIONS: Detection of hepatitis C virus RNA in lacrimal fluid of a patient with recurrent peripheral corneal ulcers may indicate a pathogenic role of hepatitis C virus in corneal pathology. Especially, since our patients with systemic hepatitis C virus infection but without ocular changes did not show hepatitis C virus RNA in their tears. Therefore, patients with recurrent corneal ulcers of unknown origin should be tested for systemic hepatitis C virus infection.

Corneal Ulcer↗
PubMed2001

Fluorescence correlation spectroscopy as a new method for the investigation of aptamer/target interactions.

Fluorescence correlation spectroscopy is an attractive tool for monitoring molecular interactions in solution. We report here a new and highly sensitive method for studying the interaction of aptamers with their targets using this technique. In vitro selection technology is a combinatorial method for the generation of nucleic acid receptors (aptamers) that are capable of binding to various target molecules. Using the in vitro selection approach we isolated RNAs which bind to the antibiotic moenomycin with high affinity. The formation of RNA-moenomycin complexes was studied by fluorescence correlation spectroscopy with a tetramethylrhodamine-labeled derivative of moenomycin.

Combinatorial Chemistry Techniques↗
PubMed2000

Simple algorithm derived from a geno-/phenotypic database to predict HIV-1 protease inhibitor resistance.

BACKGROUND: Resistance against protease inhibitors (PI) can either be analysed genotypically or phenotypically. However, the interpretation of genotypic data is difficult, particularly for PI, because of the unknown contributions of several mutations to resistance and cross-resistance. OBJECTIVE: Development of an algorithm to predict PI phenotype from genotypic data. METHODS: Recombinant viruses containing patient-derived protease genes were analysed for sensitivity to indinavir, saquinavir, ritonavir and nelfinavir. Drug resistance-associated mutations were determined by direct sequencing. geno- and phenotypic data were compared for 119 samples from 97 HIV-1 infected patients. RESULTS: Samples with one or two mutations in the gene for the protease were phenotypically sensitive in 74.3%, whereas 83.6% of samples with five or more mutations were resistant against all PI tested. Some mutations (361, 63P, 71V/T, 771) were frequent both in sensitive and resistant samples, whereas others (241, 30N, 461/L, 48V, 54V, 82A/F/T/S, 84V, 90M) were predominantly present in resistant samples. Therefore, the presence or absence of a single drug resistance-associated mutation predicted phenotypic PI resistance with high sensitivity (96.5-100%) but low specificity (13.3-57.4%). A more specific algorithm was obtained by taking into account the total number of drug resistance-associated mutations in the gene for the protease and restricting these to certain key positions for the PI. The algorithm was subsequently validated by analysis of 72 independent samples. CONCLUSION: With an optimized algorithm, phenotypic PI resistance can be predicted by viral genotype with good sensitivity (89.1-93.0%) and specificity (82.6-93.3%). The reliability and relevance of this algorithm should be further evaluated in clinical practice.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Comparison of immunogenicity and reactogenicity of a measles, mumps and rubella (MMR) vaccine in German children vaccinated at 9-11, 12-14 or 15-17 months of age.

Children aged 9-11, 12-14 or 15-17 months, respectively were vaccinated with a measles, mumps and rubella (MMR) vaccine and serum antibody responses and reactogenicity were compared. The data of 118 children could be analysed (group 1=9-11 months, n=46; group 2=12-14 months, n=29, group 3, 15-17 months, n=43). The only significant difference observed was for seroconversion against measles virus between group 1 and group 3 (84.8% vs 100%, p=0.012). No serious adverse events were reported. Local side reactions were mild, infrequent and independent of age. Immunisation against MMR is safe and effective even when administered before the currently recommended age of 12 months.

Age Factors↗
PubMed2000

Low level of cross-resistance to amprenavir (141W94) in samples from patients pretreated with other protease inhibitors.

The therapeutic success of an antiretroviral salvage regimen containing protease inhibitors (PI) is limited by PI-resistant viral strains exhibiting various degrees of resistance and cross-resistance. To evaluate the extent of cross-resistance to the new PI amprenavir, 155 samples from 132 human immunodeficiency virus type 1-infected patients were analyzed for viral genotype by direct sequencing of the protease gene. Concomitantly, drug sensitivity to indinavir, saquinavir, ritonavir, nelfinavir, and amprenavir was analyzed by a recombinant virus assay. A total of 111 patients had been pretreated with 1-4 PI, but all were naive to amprenavir. A total of 105 samples (67.7%) were sensitive to amprenavir; 25 samples (16.1%) were intermediately resistant, and another 25 samples were highly resistant (4- to 8-fold- and >8-fold-reduced sensitivity, respectively). The mutations 46I/L, 54L/V, 84V, and 90M showed the strongest association with amprenavir resistance (P < 0. 0001). The scoring system using 84V and/or any two of a number of mutations (10I/R/V/F, 46I/L, 54L/V, and 90M) predicted amprenavir resistance with a sensitivity of 86.0% and a specificity of 81.0% within the analyzed group of samples. Of 62 samples with resistance against 4 PI, 23 (37.1%) were still sensitive to amprenavir. In comparison, only 2 of 23 samples (8.7%) from nelfinavir-naive patients with resistance against indinavir, saquinavir, and ritonavir were still sensitive to nelfinavir. Amprenavir thus appears to be an interesting alternative for PI salvage therapy.

Carbamates↗
PubMed2000

Analysis of the RNase T1 mediated cleavage of an immobilized gapped heteroduplex via fluorescence correlation spectroscopy.

We report a new method for studying the activity of hydrolytic enzymes. Fluorescence correlation spectroscopy was used to observe online the hydrolyzation of a rhodamine B-labeled substrate by ribonuclease T1. A gapped heteroduplex substrate - a hybrid of a ribooligonucleotide and two smaller complementary deoxyribooligonucleotides - was immobilized via biotin to a streptavidin-coated surface of a coverslip. The reported method opens the possibility to study the cleavage of small substrates differing only slightly in molecular weight from the enzyme reaction product. The use of fluorescence correlation spectroscopy allows the detection of very low enzyme concentrations (down to 10(-21) mol 0.05 fM of RNase T1, corresponding to about 600 RNase T1 molecules in 0.02 ml).

Binding Sites↗
PubMed2000

Epstein-Barr virus in pediatric patients after renal transplantation.

BACKGROUND: Pediatric allograft recipients are at an increased risk for lymphotropic virus-associated disorders, particularly in association with primary EBV infection. PATIENTS AND METHODS: Twenty-nine children, adolescents and young adults after renal transplantation were studied in comparison with a healthy young adult control group for evidence of primary, reactivated or chronic active EBV infection at two different time points. RESULTS: Prevalence of antibodies against viral capsid antigen (VCA) was > or = 90% in both groups, whereas anti-Epstein-Barr nuclear antigen (EBNA) was detected only in 19 of 26 seropositive patients compared with seropositive controls (p = 0.01). Persistence of EBV DNA in leukocytes for > or = 6 months was observed in 11 seropositive patients (38%) and one control patient (p < 0.007) using nested polymerase chain reaction. In the transplant recipients, 3 cases of primary EBV infection and 3 cases of chronic active EBV infection were identified. One of these cases developed a non-Hodgkin lymphoma one year later. CONCLUSION: The results suggest that determination of pretransplant antibody status in recipients, rapid detection of EBV infection in seronegative symptomatic recipients, and regular screening for persistent EBV DNA in patients at risk to develop post-transplantation lymphoproliferative disease should be performed.

Adolescent↗
PubMed2000

Phenotypic HIV-1 resistance correlates with treatment outcome of nelfinavir salvage therapy.

In order to analyse whether drug sensitivity testing would be beneficial for clinical decision-making in heavily pretreated patients, we retrospectively studied viral genotype and phenotypic drug resistance in 12 HIV-1-infected patients, each of them with a history of failing at least one therapeutic regimen including one or two protease inhibitors (PIs). The salvage therapy included nelfinavir as new PI in all cases. Four patients showed a sustained and five patients a transient viral load decrease. Three patients failed to show a significant decline of plasma HIV-1 RNA. In the baseline samples of these cases, resistance against all components of their combination therapy could be detected, whereas at least one antiretroviral drug was still active in the cases with transient treatment response. All patients with sustained therapy response harboured viruses that were either fully sensitive or resistant to only one of the drugs administered. In our study, phenotypic drug resistance was predictive for the success of antiretroviral salvage regimens.

Amino Acid Sequence↗
PubMed1999

Rapid, phenotypic HIV-1 drug sensitivity assay for protease and reverse transcriptase inhibitors.

BACKGROUND: Development of drug resistance is one of the major reasons for the failure of antiretroviral therapy of HIV-1 infection. Knowing the drug sensitivity-resistance profile of viruses present in a patient prior to treatment or change in treatment could help to optimize therapy. OBJECTIVE: Development of a rapid standardized phenotypic HIV-1 drug sensitivity assay for protease (PR) and reverse transcriptase (RT) inhibitors. DESIGN: The PR gene (codons 1-99) and the 5' part of the RT gene (codons 1-300) of HIV-1 is amplified from the plasma of infected individuals by RT-PCR and ligated into a proviral clone of HIV-1 containing a deletion of the PR gene and the 5' part of the RT gene. Bacteria are transformed with the ligation product and plasmid DNA is prepared from a library of transformed bacteria. The plasmid DNA is transfected into 293 T cells and recombinant virus is harvested from the supernatant of the transfected cells 2 days after transfection. The sensitivity of the recombinant virus is determined with the help of a sensitive indicator cell line. RESULTS: Recombinant viruses were generated with high efficiency. Determination of the drug sensitivity of the recombinant viruses with an indicator cell line was highly reproducible. The recombinant viruses accurately reflected the sensitivity-resistance profile of the parental viruses. The phenotypic drug sensitivity determined by this assay correlated well with the treatment history of patients. CONCLUSION: This assay system should allow rapid, high-throughput analyses of phenotypic HIV-1 drug sensitivity for PR and RT inhibitors. Due to the efficient generation of recombinant viruses, propagation of the recombinant viruses in cell culture is not required prior to the determination of the sensitivity of the recombinant viruses. The risk of selecting fitter non-resistant viruses due to culture conditions is minimized.

Anti-HIV Agents↗