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O P Rekvig

Publications and source records attributed to O P Rekvig.

At least 19 recordsLinked to original sources
PubMed2004

Anti-DNA antibody subpopulations and lupus nephritis.

As a consequence of increased insight into the cellular and molecular mechanisms responsible for induction of B cell and T cell autoimmunity to DNA and nucleosomes, there is an obvious need to reconsider the dogma stating that anti-dsDNA antibodies serve as marker antibodies for SLE and also that anti-dsDNA antibodies per se are responsible for the initiation of lupus nephritis. Given that the potential to produce anti-dsDNA antibodies is an inherent property of the normal immune system and that few anti-DNA antibodies have nephritogenic potential, we must try to solve the problem whether it is avidity for DNA, specificity for unique DNA structures or cross-reactivity with non-DNA molecules, that make such antibodies pathogenic and thus potential markers for SLE and lupus nephritis. In this review, we will summarize contemporary problems related to these questions; (1) try to focus on phenotypic differences with respect to the ability to produce anti-dsDNA antibodies between individuals suffering from SLE and those not belonging to this diagnostic group, and (2) to describe differences between pathogenic and non-pathogenic anti-dsDNA antibodies.

Animals↗
PubMed2004

Anti-dsDNA antibodies and disease classification in antinuclear antibody positive patients: the role of analytical diversity.

BACKGROUND: The presence of "anti-DNA antibodies in abnormal titres" is a well established criterion for SLE classification, but there is no agreement on the performance of this test. OBJECTIVE: To study the correlation between clinical findings and five different solid and solution phase anti-DNA antibody assays. METHODS: 158 consecutively collected ANA positive sera were studied in a double blind fashion. Anti-DNA antibodies were determined by different solid phase assays (ssDNA-, dsDNA- specific ELISA, EliA anti-dsDNA assay, Crithidia luciliae assay), and by an experimental solution phase anti-DNA assay using biotinylated pUC18 plasmid, human, calf thymus, and E coli DNA. Antibody affinity was determined by surface plasmon resonance. Clinical data were obtained independently of the laboratory analyses and later related to the anti-dsDNA findings. RESULTS: Anti-dsDNA antibodies were most frequently detected by ELISA, but were not specific for SLE as they were present in up to 30% of other disease groups. Those detected by the Crithidia luciliae assay were predictive for SLE, while antibodies binding in solution phase ELISA using the pUC18 correlated strongly with the Crithidia luciliae assay. Surface plasmon resonance analysis showed that antibody binding to pUC18 was not due to higher relative affinity for dsDNA in general, but apparently to specificity for that plasmid DNA. Serum samples from three patients with lupus nephritis were positive in both pUC18 solution phase and Crithidia luciliae assays. CONCLUSIONS: Assay principle selection is decisive for the detection of clinically significant anti-DNA antibodies. Revision of the anti-DNA antibody criterion in the SLE classification may be needed.

Animals↗
PubMed2001

Simian virus 40 large T-antigen, but not small T-antigen, trans-activates the human cytomegalovirus major immediate early promoter.

Cytomegalovirus infection is a major cause of morbidity in immunocompromised patients. The major immediate early promoter/enhancer (MIEP) of the human cytomegalovirus controls the expression of the immediate early genes 1 and 2 which play a central role both in primary and reactivated human cytomegalovirus (HCMV)-infections. Our previous studies have shown that co-infection of A549 cells with human cytomegalovirus and human polyomavirus BK resulted in enhanced expression of the immediate early genes 1 and 2 and that the early gene products of BK virus trans-activated the MIEP. However, neither the MIEP sequences required for mediating this trans-activation, nor the contribution of the individual BK virus early gene products were examined. The MIEP contains multiple binding sites for the transcription factors CREB, AP1, Sp1 and NFkappaB, which may mediate polyomavirus large T- or small t-antigens-induced promoter activation. Transient transfection studies in A549 cells demonstrated that SV40 large T-antigen, but not small t-antigen, trans-activated MIEP activity approximately 9-fold. Mutations in individual binding motifs in the context of the complete MIEP did not impair traits-activation by large T-antigen. The level of induction of a truncated MIEP consisting of a single set of CRE/AP1, NFkappaB, and Sp1 binding motifs by large T-antigen was reduced 2-fold compared to the full length MIEP. Extended truncations diminished trans-activation by large T-antigen. To determine the contribution of a single binding motif in the trans-activation by large T-antigen, a CRE/AP1, an NFkappaB, an Sp1, or a non-consensus Sp1-motif, respectively, was linked to the MIEP TATA-sequence respecting the natural spacing between the two transcription regulatory elements. Only the MIEP TATA-box with the correctly spaced non-consensus Sp1 binding site (GT-motif) was stimulated by large T-antigen. These results suggest that an isolated non-consensus Sp1-motif is important for trans-activation of the MIEP by large T-antigen, but that other cis-acting elements can compensate for this element in the context of the whole MIEP.

Antigens, Polyomavirus Transforming↗
PubMed2001

Differences in the reactivity of CD4+ T-cell lines generated against free versus nucleosome-bound SV40 large T antigen.

Previous results have revealed a strong correlation between polyomavirus BK reactivation and disease activity and antinuclear auto-antibody production in the human autoimmune disease systemic lupus erythematosus. BK virus establishes a latent infection in most humans, and reactivation requires the production of the DNA-binding large T antigen. Experimentally induced expression of the polyomavirus SV40 large T antigen in mice induces both an immune response to large T antigen and autoimmune response to nuclear antigens and antinuclear antibody production. Previous results have indicated that human T-antigen-specific CD4+ T-cell lines are stimulated equally by free, soluble and nucleosome-bound T antigen. This study was designed to determine how antigen processing of nucleosomes containing bound SV40 large T antigen may affect the specificity and response characteristics of experimentally induced T-antigen-specific CD4+ T cells. The results indicated that CD4+ T-cell lines generated from mice immunized with soluble, free T antigen responded very poorly in response to stimulation with T antigen bound to nucleosomes. CD4+ T-cell lines generated from mice immunized with nucleosomes that had bound T antigen in situ responded to both free and nucleosome-bound T antigen. The T-antigen-specific, CD4+ memory T cells induced by latent polyomavirus infections in humans may be uniquely suited to initiate autoimmunity to nuclear antigens upon virus reactivation.

Animals↗
PubMed2001

Antinuclear antibody screening in this new millennium: farewell to the microscope?

ANA testing by immunofluorescence technique (F-ANA) is nowadays still performed in much the same way as 45 years ago when the test was introduced. Due to its low specificity the F-ANA test has a poor predictive value for systemic autoimmune diseases and in addition has proven difficult to standardise. In the meantime, many of the nuclear and cytoplasmatic auto-antigens, related to specific types of autoimmune disease, have been characterised and can be tested for in specific ELISA assays (E-ANA). These assays are in large part automated and enable the large volume testing required, by the current attitude, to use ANA-testing for its high negative predictive value in the exclusion of systemic autoimmune disease. In addition, E-ANA assays give specific results for clinically relevant autoantibodies, while its test repertoire can be altered at any given time to reflect changes in current thinking on relevant auto-antigens. Thus, we suggest that the unspecific F-ANA test should no longer be considered the gold standard for the detection of clinically relevant autoantibodies.

Antibodies, Antinuclear↗
PubMed2000

A longitudinal study of human cytomegalovirus serology and viruria fails to detect active viral infection in 20 systemic lupus erythematosus patients.

In this study, we investigated whether active human cytomegalovirus infection could be detected in 20 systemic lupus erythematosus (SLE) patients over a one-year observation period by polymerase chain reaction on serial urine specimens and by monitoring of IgG and IgM HCMV-specific antibody profiles in serial serum samples. Of 788 urine samples analysed for the presence of human cytomegalovirus DNA, only 2 specimens (0.25%) collected from two different patients contained genuine human cytomegalovirus sequences as determined by polymerase chain reaction and subsequent sequencing of the PCR products. These two patients had one positive sample out of 36 samples or 40 samples, respectively. Nineteen of the patients (95%) possessed IgG antibodies against human cytomegalovirus, while 9 (45%) produced IgM antibodies. However, none of the patients showed signs of an active virus infection as judged by the stable anti-HCMV IgG or IgM antibody levels during the observation period, nor was any correlation between disease activity and HCMV serology/viruria observed. Of single serum samples of 26 age- and sex-matched blood donors, 21 (81%) were HCMV IgG positive and 1 (3.8%) was IgM seropositive. In conclusion, our data fail to establish an active human cytomegalovirus infection in SLE patients.

Adult↗
PubMed1999

T cell lines specific for polyomavirus T-antigen recognize T-antigen complexed with nucleosomes: a molecular basis for anti-DNA antibody production.

We have previously demonstrated that in vivo expression of the polyomavirus DNA-binding T-antigen initiated production of IgG antibodies to T-antigen and to DNA, but not to a panel of autoantigens not related to nucleosomes, indicating an antigen-selective T cell-dependent B cell response. In this study, we demonstrate that CD4-positive T cells from both normal and systemic lupus erythematosus (SLE) patients readily proliferate in response to pure T-antigen, and also to T-antigen in complex with nucleosomes. T-antigen-specific T cell lines from both normal individuals and SLE patients proliferate in response to nucleosome-T-antigen complexes, but not to nucleosomes or histones. B cells co-cultured with T-antigen-specific T cells and stimulated with nucleosome-T-antigen complexes produce anti-T-antigen and anti-DNA antibodies, indicating that such CD4-positive T cells have the potential to interact with B cells specific for individual components of nucleosome-T-antigen complexes. Thus, a non-self DNA-binding protein like polyomavirus T-antigen may initiate and maintain an antibody response to DNA when T-antigen is actively expressed.

Adult↗
PubMed1999

Termination of human T cell tolerance to histones by presentation of histones and polyomavirus T antigen provided that T antigen is complexed with nucleosomes.

OBJECTIVE: To investigate whether polyomavirus T antigen linked to histones through nucleosome-T antigen complexes has the potential to terminate histone-specific T cell anergy. METHODS: Blood mononuclear cells from healthy individuals were used as the source to establish T cell lines initiated and maintained by T antigen, histones, nucleosome-T antigen complexes, or nucleosomes. Proliferative responses of these lines to T antigen, histones, and nucleosomes were determined. RESULTS: Whereas T cell lines could be established using T antigen or T antigen-nucleosome complexes, histones or nucleosomes did not have this potential. However, T cell lines selected by T antigen-nucleosome complexes responded subsequently to histones and nucleosomes. Identical results were obtained with murine and human nucleosomes, provided that they were complexed with T antigen. CONCLUSION: T antigen-specific T cells possess the potential to proliferate when interacting with an antigen-presenting cell that presents T antigen. In the presence of T antigens complexed with nucleosomes, T antigen-specific T cells offer bystander help that may terminate histone-specific T cell anergy. These T cells may progress into functional, autoimmune T cells if histones are properly presented.

Animals↗
PubMed1999

Linked production of antibodies to mammalian DNA and to human polyomavirus large T antigen: footprints of a common molecular and cellular process?

OBJECTIVE: To test whether the presence of antibodies to human polyomavirus large T antigen, a viral DNA-binding protein essential for productive polyomavirus replication, correlates with the presence of antibodies to single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), or the autologous TATA-binding protein (TBP). METHODS: Sera from patients with various diagnosed or suspected autoimmune syndromes were analyzed for the presence of antibodies to T antigen, DNA, or TATA-binding protein, and correlations were determined. Rheumatoid factor (RF) was studied as a control antibody. RESULTS: A highly significant correlation between antibodies to T antigen and antibodies to ssDNA or TATA-binding protein, but not between anti-T antigen antibodies and RF, was found in all patient groups. Of all sera that were positive for antibodies to dsDNA, 62% were positive for antibodies to T antigen (P<0.03). CONCLUSION: A non-self DNA-binding protein such as human polyomavirus large T antigen may render DNA immunogenic upon binding to nucleosomes when expressed in vivo. This is indicated by the strong correlation between antibodies to T antigen and antibodies to DNA or TBP and is consistent with a hapten-carrier model. This model implies cognate antigen-selective interaction of T antigen-specific T helper cells and DNA-specific B cells or B cells specific for other components of nucleosomes, consistent with the results of previous experiments.

Antibodies, Antinuclear↗
PubMed1999

Screening tests for antinuclear antibodies (ANA): selective use of central nuclear antigens as a rational basis for screening by ELISA.

Rational, fully automated ELISA screening tests for ANA have become accessible for routine use. Full length, recombinant or purified naturally expressed antigens can be selected to deliver well defined screening tests, designed to detect ANAs of established clinical significance, while unknown specificities with no clear biological impact are omitted. By comparing results of ANA screening by immunofluorescence (IIF) on tissue section with HEp-2 cells, a correlation of 88% was revealed, while 86% of HEp-2-positive sera bound tissue sections. Eighty-nine percent of HEp-2 ANA-positive sera bound in ANA ELISA I. Seventy-five percent of ANAs detected in ELISA I also bound in ELISA II. These correlations were statistically significant. ANAs detected in ANA ELISA I were all detected upon retesting in both ANA screening ELISA systems, and also by antigen-specific ELISAs. Specific ANAs defined by ELISA, immunodiffusion or Crithidia tests were detected in both ANA ELISA tests. These data demonstrate that most ANAs detected by immunofluorescence tests contain a dominating repertoire of specificities covered by the ANA ELISA systems. The sensitivity of the different ELISA tests can easily be adjusted to internationally defined consensus levels, and screening for ANA using both ELISA systems detects expected ANA specificities in ongoing international quality assessment programs.

Antibodies, Antinuclear↗
PubMed1999

BK and JC viruses in patients with systemic lupus erythematosus: prevalent and persistent BK viruria, sequence stability of the viral regulatory regions, and nondetectable viremia.

A role for polyomaviruses in the pathogenesis of systemic lupus erythematosus (SLE) has been suggested. BK virus (BKV) and JC virus (JCV) were demonstrated in single urine specimens from 7 (16%) of 44 and 5 (11%) of 44 patients with SLE and 0/88 and 18 (21%) of 88 matched healthy controls, respectively. During a 1-year follow-up study, episodes of polyomaviruria were detected in 16 (80%) of 20 patients, BKV in 13, and JCV in 3 patients. A group of 12 (60%) of 20 patients demonstrated persistent or recurrent polyomaviruria, BKV viruria (n=9), or JCV viruria (n=3) in 180 (70%) of 256 specimens. Polyomaviruria was not significantly associated with immunosuppressive therapy. The BKV and JCV isolates revealed predominantly stable archetypal regulatory regions over 3 years, indicating viral persistence rather than reinfection as a cause for urinary shedding. The demonstration of nondetectable viremia and stable archetypal BKV and JCV noncoding control regions during persistent viruria argue against the urinary tract as a focus for the creation of rearranged regulatory region variants.

Adult↗
PubMed1999

Complement activation in patients with systemic lupus erythematosus without nephritis.

OBJECTIVE: To study the association between disease activity and complement activation prospectively in patients with systemic lupus erythematosus (SLE). PATIENTS AND METHODS: Twenty-one SLE patients were examined monthly for 1 yr. Disease activity, autoantibodies, conventional complement tests and the following complement activation products were investigated: C1rs-C1inh complexes, C4bc, Bb, C3a, C3bc, C5a and the terminal SC5b-9 complement complex (TCC). RESULTS: Modest variation in disease activity was noted. None of the patients had nephritis. Flare was observed at 27 visits. Four patients had anti-C1q antibodies in conjunction with modestly low C1q concentrations. The complement parameters were rather constant during the observation period. Slightly to moderately decreased C4 (0.05-0.10 g/l) was found in 10 patients and severely decreased C4 (<0.05 g/l) in seven patients. Decreased C4 was not associated with increased complement activation. Complement activation products were either normal or slightly elevated. TCC was the only activation product correlating significantly with score for disease activity at flare. None of the variables tested predicted flares. CONCLUSION: Complement tests are of limited importance in routine examination of SLE without nephritis, although TCC is suggested to be one of the most sensitive markers for disease activity.

Adult↗
PubMed1999

Seasonal variations in activity of systemic lupus erythematosus in a subarctic region.

Photosensitivity is one of the major clinical features of Systemic Lupus Erythematosus (SLE), and is considered to be implicated in the disease pathogenesis. We studied seasonal variations of SLE disease activity at latitude 70 degrees North where there is no sunlight in the winter time, in contrast to 24 h daily sunlight in the summer (midnight sun). The associations between the level of plasma melatonin in June and December with disease manifestations were also studied. Twenty-one SLE patients were examined each month for 1 y, and disease activity was assessed by laboratory parameters as well as clinical disease activity parameters SLEDAI and doctor's global assessment. Melatonin levels were quantified by a RIA-assay. There was no significant change of clinical measures or laboratory parameters of disease activity from one month to the next during the one year, except photosensitive rashes. January was the only month without SLE-flares or arthritis, in contrast to rest of the year. The levels of plasma melatonin were highest in December for seven patients and highest in June for one patient (P < 0.005). Plasma melatonin levels did not correlate with measures of clinical disease activity. At a latitude of 70 degrees North there were no major seasonal variations in SLE disease activity during the one year. There was an accumulation of photosensitivity in the summer months, but no indications of worsening of the disease in the winter months. In contrast to the rest of the year, there was no flare in January which had only 5.6 h of sunshine. The level of p-melatonin did not correlate with measures of disease activity.

Adult↗
PubMed1998

Antibodies to DNA--towards an understanding of their origin and pathophysiological impact in systemic lupus erythematosus.

In 1997, the discovery of autoantibodies reactive with DNA celebrates its fortieth anniversary. Over these 4 decades, hardly any other single spontaneously produced antibody population has been subjected to such a wide scientific interest both from a basic immunological as well as from a clinical point of view. From the time of their first description, myths and enigmas regarding their biological origin have dominated the scene. Only during the last few years results have been obtained that have justified new conceptual frameworks for the understanding of the molecular bases for their production, as well as for their pathophysiological potential in systemic lupus erythematosus (SLE). Central, newly obtained experimental and clinical results that have profoundly improved our understanding of the origin and biology of anti-DNA antibodies will be presented and discussed below.

Animals↗
PubMed1997

Experimental expression in mice and spontaneous expression in human SLE of polyomavirus T-antigen. A molecular basis for induction of antibodies to DNA and eukaryotic transcription factors.

We have previously demonstrated that experimental expression of the polyomavirus transcription factor T-antigen has the potential to induce anti-DNA antibodies in mice. Two sets of independent evidences are presented here that demonstrate a biological relevance for this model. First, we describe results demonstrating that mice inoculated with T-antigen-expressing plasmids produced antibodies, not only to T-antigen and DNA, but also to the DNA-binding eukaryotic transcription factors TATA-binding protein (TBP), and to the cAMP-response-element-binding protein (CREB). Secondly, we investigated whether polyomavirus reactivation occurs in SLE patients, and whether antibodies to T-antigen, DNA, and to TBP and CREB are linked to such events. Both within and among these SLE patients, frequent polyomavirus reactivations were observed that could not be explained by certain rearrangements of the noncoding control regions, nor by corticosteroid treatment. Linked to these events, antibodies to T-antigen, DNA, TBP, and CREB were detected, identical to what we observed in mice. Antibodies recognizing double-stranded DNA were confined to patients with frequent polyomavirus reactivations. The results described here indicate that cognate interaction of B cells recognizing DNA or DNA-associated proteins and T cells recognizing T antigen had taken place as a consequence of complex formation between T ag and DNA in vivo in the context of polyomavirus reactivations.

Adrenal Cortex Hormones↗
PubMed1997

Human polyomavirus BK and immunogenicity of mammalian DNA: a conceptual framework.

Although the origin of autoimmune antibodies to double-stranded DNA (dsDNA) is not known, the variable-region structures of such antibodies indicate that they are produced in response to antigen-selective stimulation. In accordance with this, results from experiments using artificial complexes of DNA and DNA-binding polypeptides for immunizations have indicated that DNA may induce these antibodies. The immunogenicity of DNA in vivo may therefore depend upon structures, or processes, that render DNA immunogenic. It is therefore crucial to determine the nature of the antigen(s) recognized by anti-DNA antibody-inducing Th cells. We describe here the results of a series of experiments using polyomavirus BK (BKV) inoculation as a model system for initiation of antibodies to DNA, including dsDNA, in animals. From the early observation that BKV had the potential to induce the linked production of antibodies to DNA and histones, we have investigated and described the molecular bases for how this virus may do so. The minimum requirement for DNA to act as an immunogen is the in vivo expression of the BKV early gene encoding the DNA-binding large T-antigen. In the context of in vivo expression of this gene, IgG antibodies to dsDNA, histones, and T-antigen were produced. Monoclonal anti-dsDNA antibodies derived from BKV immunized mice demonstrated variable-region structures highly similar to those of spontaneous anti-DNA antibodies in murine lupus. These results represent a conceptual advance in understanding a potential molecular basis for initiation of autoimmunity in systemic lupus erythematosus and establish a precedent for further studies on polyomavirus expression as one biological origin for anti-dsDNA antibodies in human lupus.

Animals↗
PubMed1997

Mechanisms of transcriptional regulation of cellular genes by SV40 large T- and small T-antigens.

During the past decade a number of virus-encoded transcriptional trans-activators that regulate the expression of viral genes have been reported. These trans-activators may also affect the expression or activity of several cellular genes or gene products to create an optimal cellular environment that favors viral replication. Among the better-studied viral trans-activating proteins are the Simian virus 40 large T- and small t-antigens. During the last few years, mechanisms by which these two viral proteins influence cellular gene expression start to emerge. They are grouped provisionally and reflect the methods used to determine the effects of large T-antigen. Large T-antigen may influence cellular gene expression by: i. altering mRNA levels of cellular transcription factors; ii. interacting with and regulating the DNA-binding or transcriptional activity of specific transcription factors; iii. functionally substitution of eukaryotic transcription factors; iv. direct binding to DNA; or v. regulating components of signaling transduction pathways. Small t-ag seems to exert its effect mainly through inhibiting a cellular phosphatase, protein phosphatase 2A, thereby modulating components of signal transduction pathways and preventing dephosphorylation of several transcription factors. However, small t-ag may also control cellular gene expression by regulating mRNA levels of transcription factors or by interacting with other transcription factors.

Animals↗