Autoimmune responses against posttranslationally modified antigens are a hallmark of several autoimmune diseases. For example, antibodies against citrullinated protein antigens (ACPA) have shown their relevance for the prognosis and diagnosis of rheumatoid arthritis (RA), and have been implicated in disease pathogenesis. It is conceivable that other autoantibody systems, recognizing other posttranslationally modified proteins, are also present in RA. Here, we describe the presence of an autoantibody system that discriminates between citrulline- and homocitrulline-containing antigens in the sera of RA-patients. IgG antibodies recognizing carbamylated (homocitrulline-containing) antigens were present in sera of over 45% of RA-patients. Likewise, anticarbamylated protein (anti-CarP) IgA antibodies were observed in 43% of RA-sera. ACPA and anti-CarP antibodies are distinct autoantibodies because, in selected double-positive patients, the anti-CarP antibody binding to carbamylated antigens could be inhibited by carbamylated antigens, but not by control or citrullinated antigens. Similarly, ACPA-binding to citrullinated antigens could only be inhibited by citrullinated antigens. In line with this observation, 16% of ACPA-negative RA-patients, as measured by a standard ACPA assay, harbored IgG anti-CarP antibodies, whereas 30% of these patients tested positive for IgA anti-CarP antibodies. The presence of anti-CarP antibodies was predictive for a more severe disease course in ACPA-negative patients as measured by radiological progression. Taken together, these data show the presence of a unique autoantibody system recognizing carbamylated, but not citrullinated, protein antigens. These antibodies are predictive for a more severe clinical course in ACPA-negative RA-patients, indicating that anti-CarP antibodies are a unique and relevant serological marker for ACPA-negative RA.

Objective. Rheumatoid arthritis (RA) is characterized by inflammation and joint destruction, with the degree of damage varying greatly among patients. Prediction of disease severity using known clinical and serologic risk factors is inaccurate. This study was undertaken to identify new serologic markers for RA severity using an in silico model of the rheumatic joint.Methods. An in silico model of a prototypical rheumatic joint was used to predict candidate markers associated with erosiveness. The following 4 markers were chosen for validation: tartrate-resistant acid phosphatase 5b (TRAP-5b), N-telopeptide of type I collagen (NTX), angiopoietin 2 (Ang-2), and CXCL13. Serum from 74 RA patients was used to study whether radiologic joint destruction (total erosion score and total Sharp/van der Heijde score [SHS]) after 4 years of disease was associated with serum levels at the time of diagnosis. Serum marker levels were determined using enzyme-linked immunosorbent assays. For confirmation, baseline serum levels were analyzed for an association with progression of joint damage over 7 years of followup in a cohort of 155 patients with early RA.Results. Comparison of high and low quartiles of erosion score and SHS at 4 years showed a difference in baseline serum CXCL13 level (P ‫؍‬ 0.011 and P ‫؍‬ 0.018, respectively). In the confirmation cohort, elevated baseline CXCL13 levels were associated with increased rates of joint destruction during 7 years of followup (P < 0.001 unadjusted and P < 0.004 with adjustment for C-reactive protein level). Analyzing anti-CCP-2-positive and anti-CCP-2-negative RA separately yielded a significant result only in the anti-CCP-2-negative group (P < 0.001).Conclusion. Our findings indicate that CXCL13 is a novel serologic marker predictive of RA severity. This marker was identified with the help of an in silico model of the RA joint.

The effect of a brief beta-lactam action on a bacterial culture has been studied by combining the use of a high performance photometer with phase contrast microscopic examination. After exposure of the culture with the antibiotic, the growth curves presented in logn OD have shown the importance of the pre-lytic increase in OD (PIOD). Using Escherichia coli a study of the PIOD values allowed us to separate the beta-lactam antibiotics studied into two groups: those whose PIOD were concentration-dependent (ampicillin, carbenicillin, ticarcillin, moxalactam, ceftazidime, cefsulodin, cefotaxime) and those whose PIOD were concentration-independent (or weakly dependent) (azlocillin, mezlocillin, piperacillin). When the PIOD was independent of the concentrations, long filaments were observed by phase contrast microscopy. Using Pseudomonas aeruginosa, all the antibiotics studied produced PIOD values that were barely dependent of the concentrations, and long filaments were observed by phase contrast microscopy. Study of the lag of regrowth in the post antibiotic period using a beta-lactamase technique showed that, if the PIOD was hardly concentration dependent, so was the lag of regrowth.

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Urinary tract infections caused by P-lactamase-producing bacteria were treated with 500 mg of amoxicillin three times daily plus either 250 or 125 mg of clavulanic acid three times daily. The overall cure rate was 63.6%, 77.7% with the high dose of clavulanic acid and 53.8% with the low dose. Gastrointestinal intolerance was common in the high-dose clavulanic acid regimen.Formulations of amoxicillin with potassium clavulanate possess activity against many plasmid-mediated P-lactamase-producing bacteria (3, 4, 7-11, 13-15, 19) and have been used successfully in the therapy of urinary tract infections (1,8).Two formulations were assessed in this trial, which included 22 adult in-patients (17 women and 5 men, ranging in age from 50 to 90 years) suffering from 24 episodes of urinary tract infection caused by amoxicillin-resistant organisms. Ten episodes (9 patients, group 1) were treated for 10 days with the 2:1 combination (500 mg of amoxicillin plus 250 mg of clavulanic acid administered three times daily), and fourteen episodes (13 patients, group 2) were treated with the 4:1 combination (500 mg of amoxicillin plus 125 mg of clavulanic acid administered three times daily). Tablets were taken with food. Exclusion criteria were allergy to P-lactams, renal impairment (creatinine clearance, <30 ml/ min), hepatic failure, bleeding disorders, bladder catheterization, recent administration of an effective antibiotic, and infection with an organism resistant to combinations of amoxicillin and clavulanic acid. Complete physical examinations were obtained before, during, and after treatment. Complete blood counts with differential leukocyte counts, platelets counts, hemoglobin levels, and concentrations of creatinine, urea, alkaline phosphatase, transaminases, and bilirubin in serum were also made at these times. "Clean-catch" urine was considered infected if yielding i105 organisms per ml on at least two separate occasions, together with significant pyuria (8). Clinical pyelonephritis was confirmed by the presence of antibody-coated bacteria (18). Antibiotic susceptibility was determined by an agar diffusion method (2), using filter-paper disks impregnated with amoxicillin alone (20 ,ug) and in combination with clavulanic acid (20 ,ug of amoxicillin and 10 ,ug of clavulanic acid), both kindly provided by Beecham Laboratories. Bacteria were considered susceptible if the diameter of the growth inhibition zone was >'19 mm and resistant if the zone was -14 mm. Minimal inhibitory concentrations (MICs) were determined by an agar dilution method. A multiinoculator (16) was used to deliver 4 x 103 colonyforming units per spot on the surfaces of Mueller-Hinton agar plates containing twofold serial dilutions of the combination over a suitable concentration range. The stock solution (300 ,ug/ml), prepared from pellets (provided by Beecham Laboratories) containing 2 mg of amoxicillin and 1 mg of clavulanic acid, was diluted in distilled water. The breakpoints were identical for amoxicillin alone and for the drug combination; i.e.,...