Biomedical subjects

T Flaegstad

Publications and source records attributed to T Flaegstad.

At least 37 records · Page 2Linked to original sources

PubMed1991

Detection of specific IgA antibodies against BK virus by ELISA.

The development and evaluation of an ELISA for analysis of anti-BKV specific IgA antibodies in human sera are described. All children with cancer with a primary BKV infection developed specific IgA antibodies, without any specific symptoms during the infection. Specific IgA was found in 61% of sera from healthy persons containing BKV IgG antibodies, using the chosen cut-off value, and BKV IgM in 4%. These results indicate that IgA production is more persistent than IgM. The high frequency of specific IgA antibodies could either be explained by frequent reactivations or long-lasting persistence of antibodies.

Antibodies, Viral↗

PubMed1991

Amplification and sequencing of the control regions of BK and JC virus from human urine by polymerase chain reaction.

The various strains of BKV and JCV exhibit a remarkable degree of heterogeneity in the noncoding region near the origin of DNA replication. It is of great interest, therefore, to characterize the naturally occurring variants as a first step towards the attainment of an understanding of the origin and the biological significance of this hypervariability. In this paper we report the use of polymerase chain reaction for amplification and sequencing of the control regions of BKV and JCV DNAs from urines of AIDS patients, bone marrow transplantation recipients, and other patient groups. Our results support the conclusion that BK(WW) and its variants constitute the most prevalent strain in the human population tested so far. A new strain, designated BK(TU), was isolated from some patients from Norway. Urine inocula containing BK(WW) gave BK(TU) after propagation in cell culture, while BK(TU) did not change the sequence of its control region during the same procedure. The JCV isolates were almost identical with several strains molecularly cloned from the urine reported by Y. Yogo, T. Kitamura, C. Sugimoto, T. Ueki, Y. Aso, K. Hara, and F. Taguchi (J. Virol., 1990, 64, 3139-3143). This archetypal strain may represent the JCV circulating in the human population, from which various regulatory sequences of JCV isolates could have evolved by deletions and amplifications.

BK Virus↗

PubMed1991

Antibodies against BK virus in renal transplant recipient sera: results with five different methods indicate frequent reactivations.

Sera from 10 renal transplant recipients were investigated longitudinally for antibodies to human polyomavirus BK (BKV) using specific IgG-, IgA- and IgM-ELISA, hemagglutination inhibition (HAI) and neutralization tests (NT). Nine patients had anti-BKV serum antibodies before transplantation. The serological findings in 5 patients were compatible with reactivation of BKV infections. The results obtained with different tests were generally in good agreement. However, according to the definition of significant titer increase. 1-3 patients would have been undetected by employing HAI alone. High levels of antibodies detected by the other tests generally corresponded well with NT titers, i.e. the ability to neutralize infectivity. All the 5 patients with reactivation also showed an increase in specific IgA antibodies.

Adult↗

PubMed1990

BK virus early RNA transcripts in stably transformed cells: enhanced levels induced by dibutyryl cyclic AMP, forskolin and 12-O-tetradecanoylphorbol-13-acetate treatment.

The stably BK virus (BKV)-transformed hamster cell line BKT-1B and control BHK-21 cells were treated with dibutyryl cAMP (bu2cAMP), the adenylate cyclase activator forskolin, and the tumour-promoting agent 12-O-tetradecanoylphorbol-13-acetate (TPA). Cultures were stimulated for 30 min (short) and for 24 h (long). Northern blot analysis showed that for bu2cAMP and TPA both short and long stimulation resulted in significant increases in the levels of BKV early transcripts. Short exposure to forskolin resulted in a moderate increase and long exposure in a definite increase. In all cases the increased levels were maintained for at least 24 h after short stimulation was stopped. Experiments including the transcription inhibitor actinomycin D revealed that the enhanced levels of early BKV expression after treatment with the stimuli were due to induced RNA synthesis rather than to stabilization of the RNA. No DNA amplification of the early BKV sequences could be detected in the induced cells. The results are discussed with regard to possible roles for a cAMP-responsive element and a phorbol ester-responsive element, shown by sequencing to be present in the control region of the integrated BKV genome of the BKT-1B cells.

Animals↗

PubMed1990

At least two types of control regions can be found among naturally occurring BK virus strains.

The various strains of BK virus (BKV) exhibit a remarkable degree of heterogeneity in the transcriptional control region, which may affect the biological characteristics of a BKV strain. We describe the detection and sequencing of BKV control regions directly from urine samples and after propagation in cell culture. A BKV strain [BKV (TU)] with a control region anatomy not described earlier, as well as a BKV (WW)-like strain [BKV (WWT)], was detected in urine samples by direct sequencing of polymerase chain reaction products. Urine inocula containing BKV (WWT) yielded BKV (TU) upon one passage in cell culture, while BKV (TU) did not change its control region during propagation in cell culture. Analysis of the nucleotide sequence of the transcriptional control regions revealed a partial deletion and duplication in BKV (TU) compared with BKV (WWT). In addition, the control region of BKV (TU) contains two point mutations relative to BKV (WWT). This indicates that both virus strains were probably present in the BKV (WWT)-dominated urine inocula, rather than that BKV (WWT) genomes were rearranged into BKV (TU) genomes during cell propagation. The heterogeneity of the control region of BKV strains is discussed in relation to both confirmed and putative transcription factor-binding sites.

Animals↗

PubMed1990

Antibodies to meningococci in children with meningococcal disease.

Sera from 33 children with and 84 without meningococcal disease were examined for antimeningococcal IgG and IgM antibodies using an ELISA test. The meningococcal patients had a significantly higher prevalence of specific IgG antibodies (p = 0.0014), and also higher prevalence of IgM antibodies (p = 0.08; NS) than other children. These results indicate that the patients had been immunologically stimulated for some time before admission. The meningococcal patients who died had lower prevalence of specific IgM antibodies than the surviving patients, but the difference was not significant (p = 0.16). A significant increase of or high level of antimeningococcal antibodies was found in 11/12 patients examined, the last one had high levels already at admission. This type of ELISA test should therefore be helpful in the diagnosis of meningococcal disease when blood or CSF cultures are negative.

Adolescent↗

PubMed1990

BK virus terminates tolerance to dsDNA and histone antigens in vivo.

In order to characterize the immune response to BK virus, a human polyomavirus containing dsDNA and host cell histones, we followed the appearance of antibodies in five outbred rabbits after intravenous inoculation with purified infectious BK virus without any adjuvant. The animals were followed for 15 weeks after the first inoculation and booster doses were given after four and eight weeks. Antibodies were studied by ELISA techniques with the BK virus particle, dsDNA, ssDNA or the individual histones as test antigens. Antibodies to BK virus structural proteins were detected in all rabbits. Two out of five rabbits produced antibodies to dsDNA, ssDNA, nucleosomes and histones H1 and H3. Even a weak reactivity to H2B was detected in one serum. The autoantibody response was transient as it declined after a few weeks, but it reappeared after a second boost in one of the rabbits. The other animals did not respond in the same manner. The specificity of the antibodies against dsDNA was ascertained by inhibition studies employing S1 nuclease treated DNA as inhibitor. Furthermore, the dsDNA used as coating antigen was not recognized by a human reference serum with known specificity for ssDNA. The rabbit antisera did not show any reactivity to a panel of other (in this context irrelevant) autoantigens. This suggests that the anti-DNA and -histone antibodies are not a result of non-specific polyclonal B cell activation. Thus, inoculation of dsDNA viruses may represent a new model that allows us to investigate mechanisms responsible for circumvention of tolerance to self molecules.

Animals↗

PubMed1989

[Chronic virus infections. Mechanisms and clinical significance].

Numerous viruses are known to cause chronic infections in humans. Such infections are clinically important because of their association with a variety of disorders. The article reviews the mechanisms and clinical importance of such viruses, using Herpes simplex virus, Epstein-Barr virus and human immunodeficiency virus as examples.

Chronic Disease↗

PubMed1989

[Immune response to meningococci].

The bacterium Neisseria meningitidis causes serious meningococcal epidemics with a high rate of mortality. The article reviews the immunological aspects with regard to colonization, invasion, and vaccination. Serogroup B polysaccharide gives low or no immunological response. This calls for a special vaccine to protect against the most prevalent meningococcal group in Norway.

Bacterial Vaccines↗

PubMed1989

Prevalence of anti BK virus antibody in Portugal and Norway.

Specific IgG antibodies against BK virus measured by ELISA were used as a marker of previous infection. Results with sera from healthy people of different counties in Portugal were compared with previous findings in Norwegian sera. No significant difference between the prevalence and level of BKV IgG could be found between Portugal and Norway, and when comparing the different counties of Portugal. Thus, the way of transmission seemed to follow the same routes both in rural and urban counties in Portugal, and in Norway.

Antibodies, Viral↗

PubMed1989

Stimulation of clones specific for dsDNA or idiotypes of anti-dsDNA as a consequence of BK virus inoculation.

The human polyoma virus BK (BKV) has a 5 Kbp double-stranded (ds) DNA genome packed with host cell histones into a minichromosome. Two out of 5 rabbits inoculated with infectious BKV produced detectable anti-dsDNA antibodies. In two additional rabbits antibodies against idiotypes of anti-dsDNA antibodies were elicited. These findings strongly indicate the existence of immunocompetent anti-dsDNA clones which are regulated, at least in part, through a network mechanism by anti-idiotype antibodies.

Animals↗

PubMed1988

BK virus infection in children with cancer: serological response studied by haemagglutination inhibition, neutralization, and IgG- and IgM-class specific ELISA tests.

We recently developed enzyme-linked immunosorbent assays (ELISAs) for the detection of anti-BK virus IgG- and IgM-antibodies, and also a convenient and rapid serum neutralization test. Complemented by a traditional haemagglutination inhibition test (HAI) these methods were used to investigate the longitudinal response to BKV infection in sequentially taken sera from 29 children under treatment for cancer. In separate experiments it was shown that the results were not at any extent influenced by antibodies against other polyomaviruses. At the time of diagnosis the prevalence of specific IgG- and IgM-antibodies and the geometric mean IgG levels were not significantly different for the patients compared with a group of healthy children. The primary infections seemed to occur at the same age for the two groups of children. Seven of the patients had a primary infection with BKV. The results indicate that the host response in moderately immunosuppressed children during primary infection is the same as expected for healthy individuals with the development of specific IgG, HAI, and NT antibodies, and, usually, production of BKV-IgM for several months. The results indicated that whether specific IgM was demonstrated in the first sample or appeared later during a reactivation episode, this parameter was correlated with profound immunosuppression. Significant titre changes, detectable IgM antibodies and/or seroconversions were demonstrated in 69% (20/29) of the cancer patients. Such indications of recent viral activity was recorded in 42% (8/19) of children with meningococcal infections. The observation periods for the two groups of patients are, however, not directly comparable.

Antibodies, Viral↗

PubMed1988

Characterization of BK virus-specific antibodies in human sera by Western immunoblotting: use of a zwitterionic detergent for restoring the antibody-binding capacity of electroblotted proteins.

After initial problems related to denaturation of antigenic epitopes, we developed a Western immunoblotting method for the characterization of antibodies reacting with BK virus (BKV) structural polypeptides. When a zwitterionic detergent, Empigen BB, was added to the running buffer during electroblotting, the antibody-binding capacity of electrophoretically separated BKV polypeptides was partially restored. Antibodies reacting with different BKV antigens were detected and visualized by biotinylated anti-species-specific antibodies, peroxidase-conjugated streptavidine, and diaminobenzidine staining. Human sera containing anti-BKV antibodies reacted with VP1, but a serum containing antinuclear antibodies also reacted with VP4, -5 and -6 (histones). Serum from a rabbit inoculated with purified BKV reacted with VP1, and also with VP4, indicating that BKV inoculation may imply production of antibodies against histones.

Antibodies, Viral↗

PubMed1988

Antibody-mediated enhancement of BK virus infection in human monocytes and a human macrophage-like cell line.

We have monitored BK virus (BKV) antigen expression and multiplication in human monocytes and in a human macrophage (M luminal diameter)-like cell line (U937) in the presence or absence of dilution series of human or rabbit anti-BKV antisera. After infection with BKV alone, restricted expression (structural antigens and T-antigen) and multiplication was recorded in monocytes from some donors, while in U937 cells and monocytes from other donors, no signs of viral activity were detected. Monocyte cultures established from the same donor at different times demonstrated antigen expression/multiplication on two occasions but not on the third. A pronounced enhancement of BKV expression/multiplication in human monocytes and multiplication in U937 cells was seen with some dilutions of all antisera (human and rabbit) used. The pattern of enhancement and the dilution resulting in maximum viral activity was constant and seemed to be determined by the serum, but the exact level of enhancement for a given serum differed considerably in monocytes from different donors and seemed to be determined by the cells. In the latter respect, monocytes taken from the same donor some weeks apart showed variations at the same level, as did cells from different donors. PMA (phorbol-12-myristate-13-acetate) stimulation of monocytes and U937 cells resulted in stronger antibody enhancement in terms of infectivity, without affecting the number of monocytes showing antigen expression. No expression/multiplication of BKV was detected in the murine M luminal diameter-like cell line P338 DI.

Animals↗

PubMed1988

Inoculation with BK virus may break immunological tolerance to histone and DNA antigens.

BK virus particles contain histones of host cell origin that combine with viral DNA to form minichromosomes. Data from earlier immunoblotting experiments demonstrated that rabbits inoculated i.v. with purified infectious BK virus produced antibodies not only to the viral structural protein VP1 but also to migrating polypeptides of a molecular mass ranging from 14-16 kDa. These proteins were believed to represent certain histone classes. To examine this hypothesis, sera from five rabbits inoculated with BK virus were analyzed by ELISA for antibodies against polynucleosomes, the individual histone classes, and double-stranded DNA, as well as against antigens carried by the structural viral proteins. Antibodies against polynucleosomes and also against histones H1 and H3 were found in sera from two of five inoculated rabbits. The same sera contained antibodies reacting with double-stranded DNA, whereas no antibodies against H2A, H2B, and H4 were detected. BK virus inoculation may thus lead to a break of tolerance, resulting in autoantibody production against highly conserved antigens that, in this context, may be regarded as "self-antigens", irrespective of the species in which they originate.

Animals↗

PubMed1988

BK virus infection in patients with AIDS.

Antibodies to the human papovavirus BK (BKV) were determined in a group of 25 homo- and bisexual males with AIDS, 24 men with AIDS-related complex (ARC) and 18 healthy male homosexual controls from Copenhagen. The AIDS patients had a significantly lower prevalence and level of anti-BKV antibodies tested by IgG-ELISA, hemagglutination inhibition and neutralization tests than the ARC patients. About half of the anti-BKV antibody positive AIDS patients demonstrated primary infections or reactivations but without specific IgM production. The titers were low compared to primary infections in children. At least 2 of the patients lost their serological markers in the late phase of the disease. It is therefore possible that the low prevalence of BKV infection in AIDS patients is caused by loss of serological markers even if the level of total IgG is normal or increased.

AIDS-Related Complex↗

PubMed1987

BK virus in cell culture: infectivity quantitation and sequential expression of antigens detected by immunoperoxidase staining.

We applied an indirect immunoperoxidase staining method for the detection of BK virus (BKV) antigens in Vero cells. By immunoperoxidase staining of sequential samples, expression of BKV T- and structural antigens was first detectable 72 h postinfection (pi). The initial low number of antigen positive cells was slowly increasing until 6 d pi. Thereafter, a steady progression was observed until total cytopathogenic effect 30 d pi. Viral hemagglutinins were detected 11 d pi in both the culture medium and in the cell lysate. Passage of the preparations into fresh Vero cells and immunoperoxidase detection demonstrated the presence of infectious virions in both the cell lysates and the medium from 2 d pi. The number of infectious particles in both media and cell lysates correlated to the number of IP stained cells in the sequential staining. We suggest that this type of assay might be used to examine the effects, in vitro, of interferons and other virostatic drugs of BKV and other viruses.

Animals↗

PubMed1987

Benign meningococcemia with IgG and IgM antimeningococcal antibodies measured by ELISA.

Six patients with benign meningococcemia are presented. The clinical picture was typically intermittent fever with chills, skin eruptions, maculopapules (often hemorrhagic) and arthritis/arthralgia in a person in good general condition. Meningococci of serogroup B were isolated from the blood of 3 patients, from the cerebrospinal fluid of 1 patient and from the nasopharynx of the remaining 2 patients. In 4 patients we assayed the levels of IgG and IgM antibodies against meningococcus serogroup B in an enzyme-linked immunosorbent test (ELISA), using whole bacteria as the antigen. All of them had higher antibody levels than the geometric means for healthy controls of both IgG and IgM, except for 1 patient who did not develop IgG antibodies.

Adolescent↗