A useful approach to get information about the potential fusogenic ability of virus synthetic peptides is the study of its interfacial properties and subsequent study in mono- and bilayers. In this work, we have characterized by means of physicochemical tools (i.e. compression isotherms and surface activity) the sequence 267-284, LLGTEVSEVLGGAGLTGG, derived from the E2 structural protein of HGV/GBV-C. The adsorption of the peptide at the air/water interface was monitored by following the increase in surface pressure as a function of time at two different pH values: 5 and 7. Parameters such as surface excess or molecular area were calculated from the equation of Gibbs. The peptide showed a tendency to migrate to the surface of a saline-buffered solution. It formed stable monolayers at the air/water interface giving a compression isotherm with a shape consistent with that of some alpha-helical peptide conformations. Brewster angle microscopy (BAM) showed that through compression the peptide formed multilayers. The studies with lipid monolayers (DPMC, DMPC/DMPG, and DMPC/DMTAP) showed that the peptide interacts with all the lipids assayed producing a marked disrupting effect upon them. In these effects electrostatic interactions seem to have some participation.

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SummaryAntifilaggrin autoantibodies (AFA) have described to be the most specific markers of rheumatoid arthritis (RA) and epitopes containing citrulline within the sequence of filaggrin identified as major antigenic sites recognised by AFA. In this paper we confirm that citrulline is an essential constituent of filaggrin related antigenic determinants recognised by RA specific autoantibodies, thus having an important role for the development of filaggrin peptides based serological tests. Moreover, we describe our findings on the comparative conformational analysis of filaggrin (306-324) peptide sequence and an analogue in which two arginines were simultaneously substituted by citrulline carried out by Circular Dichroism (CD) and Fourier-Transform Infrared Spectroscopy (FTIR). Results might contribute to the understanding of the structural features that may be important to explain the enhanced binding characteristics of citrullinated peptides to the autoantibodies in rheumatoid arthritis.

Letters to the EditorsAnti-carbamylated protein antibodies are associated with early abatacept response in rheumatoid arthritis Comment on: Anti-carbamylated protein antibodies as a clinical response predictor in rheumatoid arthritis patients treated with abatacept Sirs, We read the article by Kumar et al., which is the first to address the association between anti-carbamylated protein antibodies (anti-CarP) and the response to abatacept (ABA) in rheumatoid arthritis (RA), with great interest. The most striking findings were the better response (a significant reduction in δ-DAS28-PCR) to ABA in anti-CarP positive patients and a reduction in anti-CarP levels. No differences in the therapeutic response were found when analyzed according to ACPA nor rheumatoid factor status (1). This prompted us to assess whether we could reproduce their observations. The PACTABA study is a Spanish multicenter, observational sub-study of the ASCORE trial (NCT02090556) (2), including active RA patients who had previously failed with ≥1 conventional DMARD or ≥1 biologic therapy. Subcutaneous ABA was administered (125 mg weekly) and patients were followed prospectively. The therapeutic response was determined by δ-DAS28 (baseline to 3 months) and EULAR response criteria at 3 months of follow-up. Seventy-nine patients were included, of whom only the 65 who had sufficient information for data extraction were analysed. Anti-CarP were assessed at 0 and 3 months by a homemade ELISA test using fetal calf serum (cut-off ≥132.5 AU; 96% specificity vs. healthy population). The study is supported by Bristol Myers Squibb (BMS). Fifty-two patients were female (80%), with mean age of 55.1(±13.9) years and a disease duration of 9.5(±7.2) years. Eighty percent were ACPA positive and 58.5% had previously failed with ≥1 biologic therapy. At baseline, 28(43.1%) patients were anti-CarP positive and no difference in DAS28 was observed according to anti-CarP status. At three months of follow up, a significant reduction in δ-DAS28 was observed in anti-CarP positive patients compared with anti-CarP negative patients (-1.904 vs. -0.212; p<0.005) (Fig. 1a). According to anti-CarP status, a similar proportion achieved a EU-LAR response (13/32(41%) vs. 8/21(38%); p=NS). However, EULAR responders had higher baseline anti-CarP levels than nonresponders (451.3±675.4 vs. 152.6±158.3; p=0.018) (Fig. 1b). In addition, responders showed a significant reduction in anti-CarP levels after 3 months on treat-

Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research. Patient consent for publication Not required. Provenance and peer review Commissioned; internally peer reviewed.