Different immunoassays using recombinant antigens or synthetic peptides were evaluated for the serodiagnosis of Chlamydia trachomatis infections. Antigens used included cysteine-rich outer membrane protein 2 (OMP2), heat shock protein 60, the polypeptide encoded by open reading frame 3 of the plasmid (pgp3), synthetic peptides derived from species-specific epitopes in variable domain IV of the major OMP (MOMP) (Labsystems, Helsinki, Finland), and a fragment of the total lipopolysaccharide (Medac, Hamburg, Germany). Because cross-reactions between chlamydial species have been reported, Chlamydia pneumoniae-specific antibodies were also determined by immunoassays (Labsystems). Responses obtained with serum samples from patients with well-defined diseases (i.e., urethral or endocervical samples from which C. trachomatis DNA was amplified) were compared to those obtained with samples from healthy blood donors. The best sensitivity (79%) associated with the best specificity (82%) was obtained when immunoglobulin G (IgG) responses to both MOMP and pgp3 were considered. The highest sensitivity (89%) was obtained with anti-OMP2 IgG, but the lowest specificity (57%) was obtained with this antibody, due to probable cross-reactivity with C. pneumoniae OMP2.

The lower IFN-gamma concentrations in HLA-B27-positive patients with C. trachomatis reactive arthritis could be related to the tendency of these patients to have more severe or chronic arthritis.

Objective-To gain information concerning the association between parvovirus B19 infection and arthritis.Methods-Blood or synovial fluid, or both, from a total of 77 adult patients with various arthropathies (rheumatoid arthritis 13; mechanical arthropathies 11; crystal induced arthritis 13; idiopathic mono/oligoarthritis 25; suspicion of viral arthritis 15) were tested for the presence of the viral genome and anti-B19 antibodies. B19 DNA in blood and synovial fluid was investigated by nested polymerase chain reaction, and anti-B19 IgM and IgG antibodies were detected in blood by enzyme immunoassay. Results-A recent parvovirus infection was documented by the presence of anti-B19 IgM antibodies in the blood of 13 patients. B19 DNA, together with anti-B19 IgM and IgG antibodies, were detected in the blood of seven patients who had an acute transient arthritis, putatively of viral origin. Viral DNA was detected in a synovial fluid sample and in the blood of one patient with monoarthritis who had an anti-B19 IgG response only. Conclusions-The prevalence of anti-B19

SUMMARYObjective. To investigate whether determining the presence of serum or synovial fluid (SF ) IgG and IgA of anti-Chlamydia antibodies with two recent commercially available enzyme-linked immunosorbent assays (ELISA) using synthetic peptides or recombinant antigen could be helpful to detect possible Chlamydia trachomatis (CT )-involved disease in rheumatological patients without evidence of urogenital CT infection.Methods. The prevalence of such antibodies was determined in samples from patients with well-defined disease, i.e. CT sexually acquired arthritis and from patients with other inflammatory arthropathies unrelated to CT.Results. When considering IgG and/or IgA anti-MOMP or anti-LPS antibodies, a sensitivity of 100% was obtained for serum and SF samples, but with a low specificity. A sensitivity and a specificity equal or close to 80% were observed for the SF IgG anti-MOMP antibodies.Conclusion. Clinically, the most appropriate determination was the SF IgG anti-MOMP antibodies. This commercially available ELISA test could be useful for the diagnosis of probable CT reactive arthritis.K : Sexually acquired reactive arthritis, Chlamydia trachomatis, Antibodies, Enzyme-linked immunoassay, Synovial fluid.R arthritis is characterized by asymmetrical gous to C. pneumoniae MOMP (Labsystems Research Laboratory, Helsinki, Finland). The other is based on mono/oligoarthritis, following a urogenital or intestinal infection. Chlamydia trachomatis (CT ) is often an exclusively Chlamydia-specific recombinant fragment of the total lipopolysaccharide (LPS) (3-deoxyresponsible for the urogenital infection, even in the absence of direct clinical symptoms [1][2][3]. The dia--manno-2-octulopyranosonic acid or 3-Kdo) (Medac GmbH, Hamburg, Germany). This antigen, genus gnosis of C. trachomatis sexually acquired reactive arthritis (CT-SARA), defined as arthritis with evidence specific, allows the detection of antibodies against C. trachomatis, C. pneumoniae and C. psittaci. of urogenital CT infection, has recently been improved by the development of different commercially availableWe therefore used these commercially available ELISA tests for two main purposes. First, to differenkits used to detect CT nucleic acids in urogenital smears and urine from symptomatic or silently infected tiate the CT responses (determined with the MOMP antigen) from the responses against any Chlamydia patients. However, these tests are not useful if arthritis develops after the initial phase of infection, when the species (determined with the LPS antigen). Secondly, to estimate whether these tests could allow the identibacteria are not detectable any more. In such cases, serological methods in combination with anamnesis, fication of some probable CT-SARA cases among patients defined as SARA (without evidence of uroclinical picture and course of disease could provide a strong indication for probable CT-SARA. To this end, genital CT infection) or undifferentiated mono/oligoarthritis. Their performances were evaluated in terms we have...

In clinical rheumatology, the diagnosis of Chlamydia reactive arthritis is difficult because an incomplete form of the disease can closely resemble an undifferentiated seronegative mono/oligoarthritis. We investigated whether measuring specific isotypes of anti-Chlamydia antibodies in serum can improve the diagnosis, by comparing such antibody concentrations in the serum of patients with well-defined disease, i.e. Chlamydia trachomatis sexually acquired reactive arthritis (CT-SARA), with other arthritides. Antibody levels were determined by enzyme-linked immunosorbent assay (ELISA). When considering two different isotypes and their combination, the best sensitivity (63%) was obtained for IgM and/or IgA results with a specificity of 81%. The patients with CT-SARA and SARA had the highest levels of antibodies of all isotypes tested. It is concluded that, in our experimental conditions, only very high values of specific isotypes could indicate a diagnosis of Chlamydia reactive arthritis.