Inhibitory effects on HLA-DR1-specific T-cell activation by influenza virus haemagglutinin-derived peptides.

Collagen (CII) 263-272 peptide, an autoantigen in rheumatoid arthritis, is a specific human leukocyte antigen (HLA)-DR1/4-binding peptide recognized by T-cell receptors (TCR). The affinity of influenza virus haemagglutinin (HA) 306-318 peptide for the antigen-binding groove of HLA-DR1/4 molecules is higher than that of CII263-272. The HLA-DR1/4-binding residues of HA306-318 are located in the region 308-317. Altered HA308-317 peptides with substitutions of TCR-contact residues may inhibit HLA-DR1/4-specific T-cell activation by blocking the antigen-binding site of HLA-DR1/4 molecules. To evaluate the role of altered HA308-317 peptides in HLA-DR1-restricted T-cell activation, we synthesized three altered HA308-317 peptides. The specific binding of altered HA308-317 peptides to HLA-DR1 molecules was examined using flow cytometry. Effects of altered HA308-317 peptides on HLA-DR1-specific T-cell hybridoma were studied by measuring T-cell proliferation and surface expression of CD69 or CD25. The results showed that altered HA308-317 peptides were able to bind to HLA-DR1 molecules and competed with CII263-272 or wildtype HA308-317 peptide. Compared with wildtype CII263-272 or HA308-317, altered HA308-317 peptides did not stimulate significant T-cell proliferation and CD69 or CD25 expression. Furthermore, the altered HA308-317 peptides inhibited HLA-DR1-specific T-cell activation induced by CII263-272 or wildtype HA308-317 peptide, which may suggest an effective therapeutic strategy in inhibition of HLA-DR1-specific T-cell responses in autoimmunity.

Binding of natural variants of staphylococcal superantigens SEG and SEI to TCR and MHC class II molecule.

SEG and SEI are staphylococcal superantigens (SAgs) identified recently that belong to the egc operon and whose genes are in tandem orientation. Only a few allelic variants of SEG and SEI have been reported. Here we analyzed four Staphylococcus aureus strains with genotypic variation in both SAgs. However, both SAgs retain key residues in their putative TCR and MHC binding sites and, accordingly, their superantigenic properties. Thus, SEI significantly stimulates mouse T-cells bearing Vbeta3, 5 and 13, while SEG stimulates Vbeta7 and 9 in the draining node when inoculated in the footpad. As another member of the SEB subfamily, SEG also stimulates mouse Vbeta8.1+2. However, the increase in Vbeta8.1+2 T-cells observed at day 2 after inoculation reverts to normal values at day 4, whereas it remains high at day 4 following inoculation with SEC3 or SSA. T-cell stimulation assays in the mouse and analysis of the putative Vbeta8.2 binding site on SEG, which includes three non-conserved residues, suggest a possibly unique interaction between Vbeta8.2 and SEG. We also analyzed biochemical and biophysical characteristics of SEI and SEG binding to their cognate human beta chains by surface plasmon resonance, and binding to the HLA-DR1 MHC class II molecule by gel filtration. SEI binds human Vbeta5.2 and Vbeta1 with apparent K(D)'s of 23 and 118 microM, respectively; SEG binds Vbeta13.6 with a K(D) of 5 microM. As suggested by sequence homology, SEI requires Zn2+ for strong binding to DR1, which goes undetected in the presence of EDTA. SEG and SEI have characteristics such as co-expression, different interaction with MHC class II and stimulation of completely different subsets of human and mouse T-cells, which indicate complementary superantigenic activity and suggest an important advantage to staphylococcal strains in producing them both.

Analysis of improvements, full responses, remission and toxicity in rheumatoid patients treated with step-up combination therapy (methotrexate, cyclosporin A, sulphasalazine) or monotherapy for three years.

OBJECTIVE: To evaluate two monotherapies followed by step-up combination therapy with two or three complementary drugs in active rheumatoid arthritis (RA) in comparison with sulphasalazine (SSZ) alone. METHODS: One hundred and twenty-six consecutive patients with early active RA were enrolled in this open controlled clinical trial. The primary end-point was 50% improvement according to the ACR criteria (ACR50) at 6, 12 or 18 months. The secondary end-points were a full response (Magnusson criteria) and/or remission (ACR criteria) at 3 yr. Methotrexate (MTX) (group 1), cyclosporin A (CsA) (group 2) or SSZ (group 3) was used first. After 6 months, a combination of two drugs (CsA and MTX) was employed in groups 1 and 2. SSZ was added after 12 months if improvement was less than ACR50 with the combination. Group 3 continued with SSZ alone. RESULTS: After 6 months, 57% of patients in group 1, 31% of group 2 (MTX vs CsA, P=0.002) and 33% of group 3 (MTX vs SSZ, P=0.01) had reached ACR50 improvement according to intention-to-treat analysis. At month 12 after starting a drug combination, 67% of group 1 and 76% of group 2 had reached ACR50 compared with 24% of group 3. At the 18-month follow-up, 90% of group 1 and 88% of group 2 but only 24% of group 3 had reached ACR50. After 18 months, 62% of group 1, 60% of group 2 and 48% of group 3 showed side-effects and three, five and eight patients in the three groups respectively had dropped out of the study. At the 3-yr follow-up, 9% of the patients in groups 1 and 2 and 7% of group 3 were in remission according to the ACR criteria; according to the Magnusson criteria, 40% showed a full response in groups 1 and 2 but only 21% did so in group 3. CONCLUSION: MTX appears to be the fastest-acting agent. A step-up approach with MTX plus CsA plus SSZ led to a 50% improvement according to the ACR criteria in most patients. After 3 yr, 40% of patients receiving combination therapy and 21% of patients receiving monotherapy showed a full response, while 9 and 7% respectively attained remission.

Effects of nilvadipine on cytokine-levels and soluble factors in collagen disease complicated with essential hypertension.

We examined some immunological parameters, particularly cytokines and soluble factors in collagen diseases complicated with essential hypertension. We also investigated the effects of Nilvadipine on immunological parameters after treatment with this drug for six months. The frequency of helper/inducer T cells (CD4+ CD8- cells, CD4+ CD45RA- cells) decreased in the peripheral blood on a 6 month treatment with nilvadipine. There was a significant decrease of suppressor/inducer T cells (CD4+ 45RA+ cells), and an insignificant decrease of activated T cells (CD3+ HLA-DR+ cells) and memory T cells (CD45RA- CD45RO+ cells) after treatment. Before treatment with Nilvadipine, interleukin-1beta, tumor necrosis factor-a, and interleukin-6 levels increased higher in the patients than in healthy volunteers. However, interleukin-1beta and interleukin-6 concentrations tended to decrease after treatment with Nilvadipine. Besides, tumor necrosis factor-alpha decreased significantly after treatment. The soluble interleukin-2 receptor concentrations also showed a decreased tendency after treatment, although high concentrations were found in the patients before treatment. In contrast, soluble human leukocyte antigen-1 and soluble thrombomodulin levels showed no significant change after treatment. These results suggest that Nilvadipine inhibits the generation of cytokines derived from activated T lymphocytes. Nilvadipine, calcium antagonist, may be useful for inhibition of vascular complication in collagen diseases.

Tetrapeptide derived inhibitors of complexation of a class II MHC: the peptide backbone is not inviolate.

Major histocompatabilty (MHC) proteins rely heavily on peptide backbone recognition for ligation. Nonetheless, modifications to the polyamide backbone of a tetrapeptide ligand can be made without abrogating binding.