AB0025 CITRULLINATED-PEPTIDE SPECIFIC CD4+ T CELL RESPONSES IN RHEUMATOID ARHRITIS

Background:

CD4+ T cells reacting to post-translationally modified, citrullinated self-antigens are thought to play a central role in the pathogenesis of rheumatoid arthritis (RA)1. This is evidenced by a strong HLA class II association, the success of therapeutic co-stimulation blockade and the detection of autoantigen specific T-cells using HLA class II multimers2. These cells may represent a target for antigen-specific, tolerogenic therapies and their in-depth phenotyping may provide the means by which to monitor such treatment.

Objectives:

To identify the citrullinated-peptide (cit-peptide) induced cytokine repertoire of antigen-specific memory CD4+ T cells in both healthy controls (HCs) and ACPA positive RA patients using intracellular cytokine staining and flow cytometry. Of note, the HLA-types of both HCs and RA patients were not known.

Methods:

Cryopreserved peripheral blood mononuclear cells (PBMC) from both HCs (n = 8) and RA patients (n = 13) with both early (untreated) and established disease were thawed and labelled with a proliferation tracking dye (PTD). Labelled PBMC were then either incubated alone or with a pool of cit-peptides for 9-days, followed by a 5-hour restimulation with PMA and ionomycin, where cytokine secretion was blocked for the final 4-hours using brefeldin-A. Cells were then harvested, permeabilised and stained for T cell surface markers and intracellular cytokines including IFN-γ, IL-4, IL-21 and IL-17. Stained cells were immediately acquired using a BD Fortessa X20, where antigen-specific CD4+ T cells were identified as the viable CD45RO+ (memory) CD4+ T cell population that had proliferated (PTDlow) in response to the cit-peptides. Stimulation indices (SI) were calculated as the percentage of proliferated memory CD4+ T cells in the stimulated wells divided by the percentage in the unstimulated conditions, and cit-peptide responders were defined as those with an SI > 2.0. Net cytokine production was measured by subtracting the percentage cytokine production from unstimulated CD4+ CD45RO+ PTDlow cells, from those stimulated with the cit-peptides.

Results:

Comparable proliferative responses were observed in both donor groups in response to stimulation with the cit-peptide pool, where 37 % of HCs and 31 % of RA patients responded with an SI > 2.0 (Fig. 1A). While little cytokine production was observed in the cit-peptide responding HC T cells, for responding RA donors, cit-peptide responsive CD4+ memory T cells were predominantly IFN-γ and IL-21 producing (Fig. 1B and 1C). In contrast, these donors did not produce significant levels of either IL-17 or IL-4 (Fig. 1D and 1E).

Conclusion:

Cit-peptides were able to induce proliferation in both HCs and RA memory CD4+ T cells which, amongst the RA donors only, were of a Th1/Tfh subtype. In contrast, and while based only on a small sample, cit-peptides did not induce either IL-17 or IL-4 production in either donor group, suggesting a lack of Th17/Th2 responses. Not all donors responded to the peptide pool, possibly reflecting the limited number of pooled cit-peptides or to a lack of confirmed HLA-DRB1*04:01 positive donors, as peptides were selected for their specificity on this basis. Future work will therefore include HLA-typing, as well as the inclusion of additional citrullinated-epitopes to demonstrate autoreactivity in a wider cross-section of patients. Further phenotyping of the cit-peptide specific T cells will be performed, and future plans will be to study the assay data alongside clinical outcomes to assess its value for immune monitoring.

References:

[1]Malmström, V et al Nat Rev Immunol. 2017; 17(1):60-75.

[2]Gerstner, C et al BMC Immunol. 2020; 21(27):1-14.

Disclosure of Interests:

Jessica Swift: None declared, James Stanway: None declared, Ioana Nicorescu: None declared, Catharien Hilkens: None declared, Frederik Stevenaert Employee of: Janssen, Amy Anderson Grant/research support from: Pfizer, GSK and Janssen, Arthur Pratt Grant/research support from: Pfizer, GSK and Janssen, John D Isaacs Speakers bureau: Abbvie, Gilead, Roche, UC, Consultant of: Abbvie, Gilead, Roche, UC, Grant/research support from: Pfizer, GSK and Janssen

Figure 1.

Citrullinated-peptide specific memory CD4+ T cell proliferation (A) and net % cytokine production of IFN-γ (B), IL-21 (C), IL-17 (D) and IL-4 (E) positive cells.

Burdock (Arctium lappa) Leaf Extracts Increase the In Vitro Antimicrobial Efficacy of Common Antibiotics on Gram-positive and Gram-negative Bacteria

This work aimed to study the potential effects of four Arctii folium extracts, 5 mg gallic [GAE] acid equivalents per 1 mL sample, on six antibiotics (Ampicillin/AM, Tetracycline/TE, Ciprofloxacin/CIP, Sulfamethoxazole-Trimethoprim/SXT, Chloramphenicol/C and Gentamicin/CN) tested on four Gram-positive (Staphylococcus aureus ATCC 6538, Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, and Staphylococcus epidermidis ATCC 12228) and five Gram-negative (Proteus mirabilis ATCC 29245, Escherichia coli ATCC 35218, E. coli ATCC 11229, E. coli ATCC 8739, and Bacillus cereus ATCC 11778) bacteria. Arctii folium extracts were the whole ethanol extract/W and subsequent ethyl acetate/EA, aqueous/AQ, and chloroform/CHL fractions. Chemical qualitative analysis (HPTLC method) emphasized five main polyphenol compounds in Arctii folium polar extracts: chlorogenic acid (Rf≈0.52/0.55) and its isomer, 1,5-di-O-caffeoylquinic acid (Rf≈0.90/0.92), plus cynarin (Rf≈0.77), hyperoside (Rf≈0.68/0.64) and isoquercitrin (Rf≈0.69/0.71). Microbiological screening indicated Arctii folium polar extracts (AQ and W) efficacy on S. epidermidis ATCC 12228; the MIC values were in the range of common antibiotics, being 32 and 128 μg GAE per mL sample respectively. The unpredictable effects (stimulatory or inhibitory) of Arctii folium extracts in combination with typical antibiotics as well as a potential use of the whole ethanol extract/W for restoring the antimicrobial potency of susceptible antibiotics have also been evidenced.

Antioxidant Properties of a Parsley (Petroselinum crispum) Juice Rich in Polyphenols and Nitrites

Parsley (Petroselinum crispum) is an herbaceous vegetable used as foodstuff, spice and medicinal plant because it provides antioxidants especially flavonoids (apigenin), vitamins (K, C and A), and volatile oils, among other compounds. Because parsley has important concentrations of nitrates and flavonoids, very little vegetal pigment and a mild flavour profile, it was chosen for this study. The aim of this study was to obtain parsley juice rich in nitrite and polyphenols and to assess its antioxidant activity. To obtain nitrite from nitrate by enzymatic reaction, Staphylococcus xylosus ATCC 29971 was used as nitrate reductase source. To obtain the vegetable juice, fresh roots were minced and homogenized in aqueous solution. The sterile juice was filtered and then inoculated with S. xylosus and incubated at 37°C. The nitrate and nitrite concentrations (mg/L) were determined using a colorimetric method using salicylic acid and Griess reagent, respectively. The total polyphenols content (TPC) was measured with Folin-Ciocalteu reagent and expressed as mg gallic acid equivalent / 100 mL (mg GAE / 100 mL). The total flavonoids content (TFC) was measured with aluminium chloride reagent, and expressed as mg catechin equivalent / 100 mL (mg CE / 100 mL). To determine the antioxidant activity of parsley juice, the ability to reduce DPPH synthetic radical, reducing power of Fe3+ ion and the capacity of chelating transition metal ions were assessed. Maximum concentration of nitrites was achieved for parsley juice in the presence of S. xylosus after 24 hours; TPC was 14.87 mg GAE / 100 mL and TFC was 11.21 mg CE / 100 mL. The ability of parsley fermented juice to reduce DPPH synthetic radical was 79.45%, while the capacity to reduce Fe3+ was 0.758 ± 0.14 (absorbance at 700 nm) and to chelate Fe2+ ion was 23.64%. Parsley juice represents an important source of natural nitrate and flavonoids, with important antioxidant capacity.

Epilobi Hirsuti Herba Extracts Influence the In Vitro Activity of Common Antibiotics on Standard Bacteria

Epilobium genus has been confirmed as an effective source of natural antimicrobials. However, the influence of Epilobi hirsuti herba derived products on usual antibiotics activity has not been studied. In this study, several standardized Epilobi hirsuti herba extracts (EHE) were evaluated in order to asses their potential effects on usual antibiotics tested on standard Gram-positive and Gram-negative bacterial strains in vitro. The results emphasized that the bacterial strains ranged from sensitive (MIC values between 50–200 μg GAE mL-1) (S. epidermidis ATCC 12228) to very resistant (E. coli strains), E. faecalis ATCC 29212 being practically immune to EHE. In terms of synergistic interaction, Tetracycline and Ampicillin combinations lead to the most important stimulatory effects, the diameters of the inhibition zone being even 60% bigger compared to the antibiotic alone. Synergistic effects between myricetin(galloyl) derivates and Tetracycline were also revealed on P. aeruginosa and E. coli strains. Together, it clearly demonstrated not only EHE’s own antimicrobial properties, but also their capacity to influence the antimicrobial potency of some common antibiotics. These results could be useful for the area of herbal medicines and as potential candidates in managing microbial resistance, but also for physicians and pharmacists using combined antibacterial therapy.