Biomedical subjects

J Kolberg

Publications and source records attributed to J Kolberg.

At least 55 records · Page 3Linked to original sources

PubMed1995

A linear B-cell epitope on the class 3 outer-membrane protein of Neisseria meningitidis recognized after vaccination with the Norwegian group B outer-membrane vesicle vaccine.

The class 3 outer-membrane protein (OMP) of Neisseria meningitidis is a potential target for bactericidal and opsonic antibodies in humans. Synthetic peptides spanning the class 3 OMP from the vaccine strain 44/76 (B:15:P1.7,16:L3,7) were synthesized on pins and screened with serum obtained from Norwegian adolescents immunized with a meningococcal serogroup B outer-membrane vesicle (OMV) vaccine. A strong IgG response to a single peptide (19FHQNGQVTEVTT30) located within loop 1 (VR1) was stimulated after three doses of OMV vaccine in three vaccinees selected on the basis of their antibody response to class 3 OMP. No clear linear B-cell epitopes were recognized by four different murine serotype 15-specific mAbs. A 23mer peptide (D63b2) containing loop 1 of the class 3 OMP was synthesized, and the IgG responses were measured in pre- and post-vaccination serum from 27 vaccinees. Specific IgG rose significantly in 37% of vaccinees 6 weeks after the second dose and in 74% of the vaccinees 6 weeks after the third dose of the OMV vaccine. Most immune sera reacted distinctly on immunoblots with denatured class 3 OMP, and the immunoblotting reactivity correlated strongly with concentration of the IgG antibodies specific for peptide D63b2. When added to a post-vaccination serum from one vaccinee, peptide D63b2 competed efficiently with the class 3 OMP for specific antibody binding on immunoblots and in pin ELISA. The results show that the significant part of the humoral response to the meningococcal class 3 OMP elicited by vaccination with the Norwegian OMV vaccine was directed against a single continuous epitope.

Adult↗

PubMed1995

Emergence of a new virulent clone within the electrophoretic type 5 complex of serogroup B meningococci in Norway.

An increase in B:15:P1.12 meningococci among isolates from patients with Neisseria meningitidis infection in Norway in recent years led to further characterization of such strains. Between 1987 and 1992, B:15:P1.12 strains constituted 9.8% (24 strains) of B:15 isolates. The B:15:P1.12 strains belonged to the electrophoretic type 5 (ET-5) complex, but 17 (71%) strains were a new clone (ET-5c) not found elsewhere in the world. All but one strain of ET-5c were responsible for a localized outbreak of systemic meningococcal disease in western Norway. A novel monoclonal antibody (202,G-12), developed against the unknown variable region 2 on the class 1 protein of one of these strains, bound to 19 of the 15:P1.12 strains, 4 strains bound the subtype P1.13 reference monoclonal antibody MN24H10.75, and the remaining strain showed no reaction. Sequencing of porA genes demonstrated a series of nine threonine residues in the deduced variable region 2 of the latter strain, while four and five threonine residues were found in the corresponding regions of strains reacting with the monoclonal antibodies 202,G-12 and MN24H10.75, respectively. Epitope mapping with synthetic peptides showed that 202,G-12 bound to a sequence of 11 amino acids which included the four threonine residues specific for subtype P1.13a. Immunoglobulin G antibodies against the P1.7,16 subtype protein, induced in volunteers after vaccination with the Norwegian meningococcal vaccine, did not cross-react on immunoblots with the subtype protein of clone ET-5c. Thus, postvaccination class 1 protein antibodies, assumed to be protective, may not be effective against infection with the new clone.

Adolescent↗

PubMed1995

Human antibody responses to meningococcal outer membrane antigens after three doses of the Norwegian group B meningococcal vaccine.

The antibody kinetics in sera from 27 adults after three doses of the Norwegian group B meningococcal outer membrane vesicle (OMV) vaccine was studied. The vaccinees received the third dose 4 to 5 years after the first two. Antibody responses against outer membrane proteins (OMPs) and lipopolysaccharides were studied by enzyme-linked immunosorbent assay and immunoblotting and with serum bactericidal assays (SBA) with three variants of the vaccine strain, 44/76. Six weeks after the second injection, the geometric mean (GM) of the levels of immunoglobulin G (IgG) against OMVs was about sevenfold higher than that of prevaccination levels, and 74% of the vaccinees developed a greater-than-twofold rise in SBA titer. After 6 months, the GM of IgG levels declined to about threefold higher, and after 4 to 5 years it declined to about twofold higher, than that before vaccination. The third dose induced a rapid increase in SBA titers in 96% of the vaccinees, and the GM of levels of IgG against OMVs rose to about 14-fold the prevaccination level. One year later, the IgG antibody levels had dropped to 4.6-fold the prevaccination level, but 88% of the vaccinees still showed bactericidal activity. The response after the two first doses was higher in individuals with prevaccination antibodies, but no such effect was found after three doses. The use of defined mutants in SBA and linear multiple regression analyses indicated that among the major OMPs, antibodies to the Opc and class 1 proteins made the most important single contributions to the bactericidal activity against the vaccine strain, but it also demonstrated the importance of antibodies against other antigens. After three doses, 68% of the vaccinees showed a significant SBA response against a strain lacking both the Opc and the class 1 proteins. Three doses converted almost all subjects to SBA responders and gave higher antibody levels and relatively less serosubtype-specific bactericidal activity than did two doses, probably indicating a broader cross-protection against heterologous strains.

Adult↗

PubMed1995

Nonisotopic hybridization assay for determination of relative amounts of genotypic human immunodeficiency virus type 1 zidovudine resistance.

A nonisotopic hybridization assay for human immunodeficiency virus genotypic zidovudine resistance determination is described. Biotinylated PCR product was hybridized with enzyme-labeled probes for wild-type or resistant mutant sequences and detected colorimetrically or chemiluminescently in a microplate format. Changes in mutant-to-wild-type ratios allow for the monitoring of longitudinal patient samples.

Antiviral Agents↗

PubMed1995

Evaluation of a novel serotyping system for hepatitis C virus: strong correlation with standard genotyping methodologies.

Direct sequencing and analysis of viral genomes are definitive methods for identifying various hepatitis C virus (HCV) genotypes. However, HCV genome sequencing methods are cumbersome and unsuitable for analyzing large numbers of clinical samples. We have developed a convenient, reliable, and reproducible RIBA strip immunoblot assay system for determining HCV serotype. Briefly, the assay consists of an immunoblot strip on which there are five lanes of immobilized serotype-specific HCV peptides from the nonstructural (NS-4) and core regions of the genomes of HCV types 1,2, and 3. HCV serotype is deduced by determining the greatest intensity of reactivity to the NS-4 serotype-specific HCV peptide band in relation to the intensity of the human immunoglobulin G internal control bands on each strip. HCV core peptide reactivity is used only in the absence of NS-4 reactivity. We used this assay to successfully serotype a high percentage of sera from well-documented HCV-infected patients. Our serotyping results correlated 99% with the findings from the standard restriction fragment length polymorphism genotyping methods. Less than 5% of the serum samples were untypeable. For a selected group of alpha interferon-treated patients we observed that the nonresponders (76.2%) and a majority of the responders who relapsed (72.2%) had type 2 HCV infection. A small population (n= 8) of complete responders was split 3:4:1 as type 1, type 2, and type 3, respectively. Our data indicate that this new serotyping assay has the potential to be a highly specific and reliable method for typing of HCV infection in patients.

Genotype↗

PubMed1995

Streptococcus pneumoniae types 19A and 19F and Streptococcus suis capsular type 8 share common capsular epitopes.

Two monoclonal antibodies (MAbs) to Streptococcus pneumoniae types 19A and 19F were tested with the 35 reference strains and 334 field strains of Streptococcus suis by dot blotting. Both MAbs reacted with the capsular type 8 reference strain, and one reacted with 69% and one reacted with 100% of 81 S. suis capsular type 8 field strains tested. Epitopes recognized by both MAbs are capsular in origin.

Antigens, Bacterial↗

PubMed1995

Determination of human immunodeficiency virus RNA in plasma and cellular viral DNA genotypic zidovudine resistance and viral load during zidovudine-didanosine combination therapy.

Eleven human immunodeficiency virus (HIV)-infected subjects on long-term zidovudine (ZDV) therapy had didanosine (ddI) added to their antiretroviral regimen. HIV RNA in plasma was quantitated by branched-DNA signal amplification assay. Peripheral blood mononuclear cell (PBMC) HIV viral DNA was quantitated by PCR. The relative amounts of wild-type (WT) sequence, ddI resistance-associated codon changes (reverse transcriptase [RT] gene codon 65 K-->R [RT K65R], RT 174V, RT I135K/T/V, and RT M184I/V), and ZDV resistance-associated codon change (RT T215Y/F) from HIV RNA in plasma and RT T215Y/F from PBMC viral DNA were determined by differential hybridization of PCR products from 10 of 11 subjects. All subjects had evidence of RT T215Y/F mutation in both RNA in plasma and PBMC DNA at baseline. Subjects with a mixture of WT and RT T215Y/F HIV RNA in plasma at baseline demonstrated a decline in RNA levels in plasma after the addition of ddI. However, after 6 months of ZDV-ddI therapy, WT HIV RNA in plasma was undetectable in all subjects who had demonstrated a mixture at baseline. Subjects with only RT T215Y/F RNA present in plasma at baseline remained so and demonstrated no decline in RNA levels in plasma. In all subjects, no significant changes in PBMC DNA viral load and RT T215Y/F or WT levels were seen. HIV RNA in plasma demonstrated a significantly higher RT T215Y/F mutant/WT ratio than that of PBMC viral DNA, both at baseline and after ZDV-ddI combination therapy in all subjects. No subjects developed mutations associated with ddI resistance at codons 65, 74, 135, and 184 during this study. This study suggests that determination of relative amounts of RT T215Y/F and WT species from HIV RNA in plasma at baseline may be predictive of virologic response during ZDV-ddI combination therapy.

Base Sequence↗

PubMed1994

Identification of genotypes of hepatitis C virus by sequence comparisons in the core, E1 and NS-5 regions.

Isolates of hepatitis C virus (HCV) show considerable nucleotide sequence variability throughout the genome. Comparisons of complete genome sequences have been used as the basis of classification of HCV into a number of genotypes that show 67 to 77% sequence similarity. In order to investigate whether sequence relationships between genotypes are equivalent in different regions of the genome, we have carried out formal sequence analysis of variants in the 5' non-coding region (5'NCR) and in the genes encoding the core protein, an envelope protein (E1) and a non-structural protein (NS-5). In the E1 region, variants grouped into a series of six major genotypes and a series of subtypes that could be matched to the phylogenetic groupings previously observed for the NS-5 region. Furthermore, core and E1 sequences showed three non-overlapping ranges of sequence similarity corresponding to those between different genotypes, subtypes and isolates previously described in NS-5. Each major genotype could also be reliably identified by sequence comparisons in the well conserved 5'NCR, although many subtypes, such as 1a/1b, 2a/2c and some of those of type 4, could not be reliably distinguished from each other in this region. These data indicate that subgenomic regions such as E1 and NS-5 contain sufficient phylogenetic information for the identification of each of the 11 or 12 known types and subtypes of HCV. No evidence was found for variants of HCV that had sequences of one genotype in the 5'NCR but of a different one in the E1 or NS-5 region. This suggests that recombination between different HCV types is rare or non-existent and does not currently pose a problem in the use of subgenomic regions in classification.

Base Sequence↗

PubMed1994

Neural network for automatic analysis of motility data.

Continuous recording of intraluminal pressures for extended periods of time is currently regarded as a valuable method for detection of esophageal motor abnormalities. A subsequent automatic analysis of the resulting motility data relies on strict mathematical criteria for recognition of pressure events. Due to great variation in events, this method often fails to detect biologically relevant pressure variations. We have tried to develop a new concept for recognition of pressure events based on a neural network. Pressures were recorded for over 23 hours in 29 normal volunteers by means of a portable data recording system. A number of pressure events and non-events were selected from 9 recordings and used for training the network. The performance of the trained network was then verified on recordings from the remaining 20 volunteers. The accuracy and sensitivity of the two systems were comparable. However, the neural network recognized pressure peaks clearly generated by muscular activity that had escaped detection by the conventional program. In conclusion, we believe that neurocomputing has potential advantages for automatic analysis of gastrointestinal motility data.

Adult↗

PubMed1993

Classification of hepatitis C virus into six major genotypes and a series of subtypes by phylogenetic analysis of the NS-5 region.

Hepatitis C virus (HCV) showed substantial nucleotide sequence diversity distributed throughout the viral genome, with many variants showing only 68 to 79% overall sequence similarity to one another. Phylogenetic analysis of nucleotide sequences derived from part of the gene encoding a non-structural protein (NS-5) has provided evidence for six major genotypes of HCV amongst a worldwide collection of 76 samples from HCV-infected blood donors and patients with chronic hepatitis. Many of these HCV types comprised a number of more closely related subtypes, leading to a current total of 11 genetically distinct viral populations. Phylogenetic analysis of other regions of the viral genome produced relationships between published sequences equivalent to those found in NS-5, apart from the more highly conserved 5' non-coding region in which only the six major HCV types, but not subtypes, could be differentiated. A new nomenclature for HCV variants is proposed in this communication that reflects the two-tiered nature of sequence differences between different viral isolates. The scheme classifies all known HCV variants to date, and describes criteria that would enable new variants to be assigned within the classification as they are discovered.

Base Sequence↗

PubMed1992

At least five related, but distinct, hepatitis C viral genotypes exist.

Hepatitis C virus, the major causative agent of blood-borne non-A, non-B hepatitis in the world, has been the subject of considerable nucleic acid sequence analysis. Although all reported hepatitis C sequences from the United States have been represented by the prototype hepatitis C virus type 1 sequence, two groups of variant sequences have been reported in Japan. However, we have noted five distinct, but related, genotypes (I-V) throughout the world, based on detailed sequence determination and analysis of the first 1700 nucleotides and part of the nonstructural region 5 at the C terminus of the open reading frame. The nucleotide sequence for a large number of hepatitis C virus isolates spanning six continents was obtained by direct sequence analysis of PCR products after reverse transcription. Genotype was classified by using several distinct sequence motifs. We observed that most genotypes coexist in several geographic regions, including the United States, Japan, Germany, and Italy. So far, genotype V has been found only in South Africa. Interestingly, each distinct genotype seems to be maintained throughout the genome in the segments studied. These genotype distinctions should be considered when designing specific diagnostic tests, developing potential vaccines, and studying viral transmission.

Amino Acid Sequence↗

PubMed1992

Comparison of hepatitis C virus markers in patients with NANB hepatitis.

10 different HCV-specific assays and RT-PCR of the 5' untranslated region of HCV RNA were used to analyze sixty-four patients with chronic NANB liver disease. Po, CP-9 and C22 antigens are located in the putative core; C33c in the putative NS3; C100-3 in the putative NS3/4; KCL in the putative NS4/5 and C825 is located in the putative NS5. GOR protein is not part of the HCV genome, but antibodies to it appear to be present in response to a hepatitis C infection. Positive rates were 91% for Po, 89% for CP-9, 94% for C22, 97% for C33c, 88% for C100-3 (Ortho, EIA), 86% for C100-3 (Abbott, EIA), 84% for C100-3 (Ohtsuka, RIA), 88% for KCL, 59% for C825, 58% for GOR, and 83% for RT-PCR. There were 8 cases which were negative by all anti-C100 tests. 7 of these cases were positive by other anti-HCV markers and/or PCR suggesting the need for improved blood screening assays. There is a variation in the relative reactivity for different markers with different samples. Of the tests employed, anti C33c shows the highest positivity rate.

Adult↗

PubMed1992

Antibody binding to blood group antigens in relation to temperature: scanning electron microscopy of immunogold-labelled erythrocytes.

Binding patterns of mouse monoclonal antibodies (mAb) to P1, Pk, N, I, H, Y or A antigens were visualized in the backscatter electron imaging mode of a scanning electron microscope by indirect immunogold labelling. Experiments were performed at room temperature (RT) and at 4 degrees C. In experiments with anti-P1 and anti-Pk, clusters of immunolabelling particles dominated the immunolabelling pattern much more at RT than at 4 degrees C. By contrast, no clustering was seen with anti-N, even at RT. Clustering was also observed at RT with anti-I, anti-H and anti-Y, and on some Ax and A3 cells with anti-A, but was much reduced at 4 degrees C. Immunolabelling was stronger at 4 degrees C than at RT with all mAb except anti-N and anti-A. The results indicate that glycolipid blood group antigens are more mobile in the membrane of intact erythrocytes at RT than at 4 degrees C, and that the cells bind more antibodies to such antigens at 4 degrees C than at RT. We suggest that antigen immobilization in the cold will reduce cross-linking of antigens and hence increase the number of antibody molecules needed for epitope saturation, leading to increased binding of antibody in the cold. This may be the main reason for cold-enhanced agglutination with human blood group antibodies.

Animals↗

PubMed1992

Murine monoclonal antibodies against pneumococcal capsular polysaccharide types 4, 8, 22F and 19A/19F.

Monoclonal antibodies (MAbs) were produced against pneumococcal capsular polysaccharides after subcutaneous immunization of BALB/c mice with a 23-valent vaccine (Pneumovax N, Merck, Sharp & Dohme). Selected antibodies were tested in ELISA against individual polysaccharides from 23 different pneumococcal types and in a dot blot assay with heat-killed whole bacteria adhered to nitrocellulose paper. Three MAbs (isotype IgM) were found to be specific for types 4, 8 and 22F, respectively, whereas one (isotype IgA) reacted both with 19A and 19F. Very mild acid hydrolysis of the capsular polysaccharides resulted in loss of reaction with the antibodies.

Animals↗

PubMed1992

Antigenic change in a human IgG4-specific CH3 epitope upon binding of a monoclonal antibody against a neighboring IgG4-specific epitope.

Two sets of monoclonal antibodies (mAbs) probably reacting with two different epitopes in the CH3 domain of the human IgG4 molecule were studied. We observed that the commercially available mAb HP 6011 inhibited the antigen binding of the three mutually inhibitable mAbs, 40-A2, 41-E8 and 43-F11 (40-series), made by us. However, the 40-series mAbs, including those with similar affinity such as mAb HP6011, were not able to inhibit mAb HP 6011. When the 40-series mAbs were preincubated with IgG4, the mAb HP 6011 could partially displace these antibodies. This one-way inhibition indicates that upon binding mAb HP 6011 changes the antigenic structure of the IgG4 molecule by disrupting the epitope for the 40-series mAbs. A steric hindrance of this epitope by mAb HP 6011 is more unlikely, since the small Fab fragment of mAb HP 6011 also inhibited the reaction of the 40-series mAbs.

Antibodies, Monoclonal↗

PubMed1992

Monoclonal antibodies against rice bran lectin.

Two mouse monoclonal antibodies (IgM) were produced against the N-acetylglucosamine-specific rice bran lectin. It was difficult to establish antibody-producing hybrids when soluble rice lectin was used for immunization. Therefore a complex of rice lectin and chitin, a water-insoluble polymer of N-acetylglucosamine, was used as immunogen. Antibody reactivity against Gramineae lectins from barley, rice, rye and wheat (wheat germ agglutinin) was tested in ELISA and two (137,E-1 and 140,B-3) were found to be specific for rice lectin. Gramineae lectins were separated by sodium dodecyl-sulphate-polyacrylamide gel electrophoresis and electroblotted to nitrocellulose papers. Analyses showed that the antibodies reacted strongly with non-reduced rice lectin, whereas only weak staining was seen with the other lectins. The binding was abolished after treatment with 2-mercaptoethanol suggesting that disulphide bond tertiary structures were necessary for epitope integrity.

Acetylglucosamine↗

PubMed1991

Monoclonal antibody 117,C-11 recognizes three exposed regions on the surface of the Lathyrus ochrus isolectin I.

A mouse IgA monoclonal antibody, MoAb 117,C-11, was produced against the glucose/mannose specific isolectin I (LoLI) from Lathyrus ochrus seeds, a legume two-chain lectin comprising two heavy subunits non covalently associated to two light subunits. The MoAb reacted in ELISA with three different peptides representing three distinct amino acid stretches present on the surface of the heavy subunits of LoLI. Since these three stretches are too far apart to build a discontinuous/conformational epitope, it is presumed that they act as continuous/sequential epitopes. The presence of a complete or partial TGNV sequence within these epitopes could account for their reactivity towards the MoAb, as shown by inhibition studies using a chemically synthesized TGNV peptide. MoAb 117,C-11 also reacted with closely related two-chain lectins.

Amino Acid Sequence↗

PubMed1991

A mouse monoclonal antibody against glycophorin A produced by in vitro stimulation with human red cell membranes.

Human erythrocyte membranes were used as antigen for production of mouse monoclonal antibodies against blood group related structures by in vitro immunization. Culture medium supernatant of PHA and PMA stimulated mouse thymus cells was used as source of cytokines. The selected antibody designated 124,D-7 (isotype IgM) was found to directly agglutinate all human red cells, except the rare erythrocytes En(a-) which lack glycophorin A. Immunoblotting showed faint bands in the positions of glycophorin A, whereas no binding occurred to glycophorin B. Inhibition of agglutination with purified glycophorin A and peptides suggests that the epitope is located within the amino acid residues 35-40. Rat and chicken erythrocytes also reacted with the antibody, whereas mouse erythrocytes were only agglutinated at very low dilutions of ascitic fluid.

Agglutination Tests↗