A Machine Learning Approach for Prediction of CDAI Remission with TNF Inhibitors: A Concept of Precision Medicine from the FIRST Registry

INTRODUCTION

This study aimed to develop low-cost models using machine learning approaches predicting the achievement of Clinical Disease Activity Index (CDAI) remission 6 months after initiation of tumor necrosis factor inhibitors (TNFi) as primary biologic/targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs) for rheumatoid arthritis (RA).

METHODS

Data of patients with RA initiating TNFi as first b/tsDMARD after unsuccessful methotrexate treatment were collected from the FIRST registry (August 2003 to October 2022). Baseline characteristics and 6-month CDAI were collected. The analysis used various machine learning approaches including logistic regression with stepwise variable selection, decision tree, support vector machine, and lasso logistic regression (Lasso), with 48 factors accessible in routine clinical practice for the prediction model. Robustness was ensured by k-fold cross validation.

RESULTS

Among the approaches tested, Lasso showed the advantages in predicting CDAI remission: with a mean area under the curve 0.704, sensitivity 61.7%, and specificity 69.9%. Predicted TNFi responders achieved CDAI remission at an average rate of 53.2%, while only 26.4% of predicted TNFi non-responders achieved remission. Encouragingly, the models generated relied solely on patient-reported outcomes and quantitative parameters, excluding subjective physician input.

CONCLUSIONS

While external cohort validation is warranted for broader applicability, this study highlights the potential for a low-cost predictive model to predict CDAI remission following TNFi treatment. The approach of the study using only baseline data and 6-month CDAI measures, suggests the feasibility of establishing regional cohorts to generate low-cost models tailored to specific regions or institutions. This may facilitate the application of regional/in-house precision medicine strategies in RA management.

Extracting immunological and clinical heterogeneity across autoimmune rheumatic diseases by cohort-wide immunophenotyping

OBJECTIVE

Extracting immunological and clinical heterogeneity across autoimmune rheumatic diseases (AIRDs) is essential towards personalised medicine.

METHODS

We conducted large-scale and cohort-wide immunophenotyping of 46 peripheral immune cells using Human Immunology Protocol of comprehensive 8-colour flow cytometric analysis. Dataset consisted of >1000 Japanese patients of 11 AIRDs with deep clinical information registered at the FLOW study, including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). In-depth clinical and immunological characterisation was conducted for the identified RA patient clusters, including associations of inborn human genetics represented by Polygenic Risk Score (PRS).

RESULTS

Multimodal clustering of immunophenotypes deciphered underlying disease-cell type network in immune cell, disease and patient cluster resolutions. This provided immune cell type specificity shared or distinct across AIRDs, such as close immunological network between mixed connective tissue disease and SLE. Individual patient-level clustering dissected patients with AIRD into several clusters with different immunological features. Of these, RA-like or SLE-like clusters were exclusively dominant, showing immunological differentiation between RA and SLE across AIRDs. In-depth clinical analysis of RA revealed that such patient clusters differentially defined clinical heterogeneity in disease activity and treatment responses, such as treatment resistance in patients with RA with SLE-like immunophenotypes. PRS based on RA case-control and within-case stratified genome-wide association studies were associated with clinical and immunological characteristics. This pointed immune cell type implicated in disease biology such as dendritic cells for RA-interstitial lung disease.

CONCLUSION

Cohort-wide and cross-disease immunophenotyping elucidate clinically heterogeneous patient subtypes existing within single disease in immune cell type-specific manner.

Generation-Dependent Retention Rates and Reasons for Discontinuation of Molecular Targeted Therapies in Patients with Rheumatoid Arthritis: From FIRST Registry

INTRODUCTION

The study aimed to optimize medical care for elderly patients with rheumatoid arthritis (RA) by examining the 3-year continuation rate of different molecular targeted therapies across age groups in Japan, which has a significant elderly population.

METHODS

The study included patients with RA who started molecular targeted therapies between 2013 and 2019 and divided them into three age groups. The primary outcome was to assess the 3-year continuation rate of each drug and analyze reasons for treatment discontinuation using inverse probability of treatment weighting.

RESULTS

Among 2292 patients analyzed, tumor necrosis factor (TNF) inhibitors were most commonly used in those younger than 65 years of age (43.5%), while Janus kinase (JAK) inhibitors were also utilized (17.1%). In contrast, JAK inhibitors were less frequently used in patients aged 75 years and older (7.8%), with cytotoxic T lymphocyte antigen 4 immunoglobulin fusion proteins (CTLA4-Ig) being the most common (39.2%). JAK inhibitors and anti-interleukin-6 receptor (IL-6R) antibodies had higher continuation rates than other drugs in patients under 65 years (p < 0.001). For those aged 65-74 years, JAK inhibitors and CTLA4-Ig had higher continuation rates (p < 0.001), while among those aged 75 years and older, CTLA4-Ig and IL-6R antibodies had higher continuation rates (p < 0.001). Inadequate efficacy was the main reason for discontinuation in all age groups, while infection leading to discontinuation increased with age.

CONCLUSIONS

The study highlights the need to consider different age groups separately in elderly RA care. Among patients aged 75 years and older, abatacept and anti-IL-6R antibodies showed the highest continuation rates, suggesting their potential suitability and efficacy for this specific age cohort.

Safety and efficacy of anifrolumab therapy in systemic lupus erythematosus in real-world clinical practice: LOOPS registry

OBJECTIVES

To determine the safety and efficacy of anifrolumab in patients with systemic lupus erythematosus (SLE) classified based on the Lupus Low Disease Activity State (LLDAS) in real-world clinical practice.

METHODS

This retrospective observational study involved SLE patients who started anifrolumab therapy. The primary end point was the retention rate over 26 weeks after initiating anifrolumab therapy; 45 patients followed up for 12 weeks or longer were analyzed in the following groups to determine the safety and efficacy up to week 12 after treatment initiation: 1) non-LLDAS achievement group and 2) minor flare group. Safety and efficacy were compared between the minor flare group and the standard of care (SoC) group (treated by adding glucocorticoids (GCs) or immunosuppressants) after adjustment with inverse probability of treatment weighting using propensity score (PS-IPTW).

RESULTS

The retention rate of anifrolumab was 89.7% at week 26.The LLDAS achievement rates at week 12 were 42.9% and 66.7% in the non-LLDAS achievement and minor flare groups, respectively. In both groups, GC doses and SELENA-SLEDAI score significantly decreased. When the anifrolumab group with minor flare was compared with the SoC group or the GC dose increase group, the GC dose and SLEDAI score were significantly lower in the anifrolumab group than in both groups; there was no significant difference in LLDAS achievement.

CONCLUSIONS

At week 26 after initiating anifrolumab therapy, ∼90% patients remained on therapy. Anifrolumab might lower disease activity without initiating GCs and reduce GC doses, especially in patients who experience minor flares after LLDAS achievement.

Biological/targeted synthetic DMARDs do not arrest bone loss in patients with rheumatoid arthritis: a multicenter prospective observational study

OBJECTIVE

To elucidate the differential effects of biological/target synthesized DMARDs (b/tsDMARDs) on bone metabolism in patients with rheumatoid arthritis (RA) in a real-world cohort.

METHODS

This was a multicentre prospective observational study of RA patients enrolled at the time of 1st b/tsDMARDs administration. Bone mineral density (BMD) and bone turnover markers (BTMs) were measured during the 52-week observation. The study was designed to enrol all eligible RA patients. The end-points were differences in changes in BMD according to b/tsDMARD type, and the correlation between BMD and BTMs.

RESULTS

A total of 1,164 patients were enrolled in this study. b/tsDMARDs improved RA disease activity from mean CDAI 25.5 at baseline to 4.5 at week 26. Patients not receiving anti-osteoporotic agents (anti-OP) at baseline with no history of fracture experienced a significant decrease in both femoral neck (F: mean 0.666-0.655 g/cm3) and radial (R: 0.518-0.514) BMD at week 26. Despite maintaining low CDAI levels during weeks 26-52 (5.3-4.4), there was a continued decline in BMD (F: 0.653, R: 0.509. Weeks 52). None of b/tsDMARDs type preserved BMD. Conversely, patients receiving anti-OP at baseline maintained stable BMD throughout the study (Weeks 0/26/52. F: 0.551/0.551/0.555, R: 0.415/0.416/0.415). Although BTMs were changed by b/tsDMARDs, the changes were unrelated to those in BMD.

CONCLUSION

Our study suggested the progression of osteoporosis in RA patients during b/tsDMARDs treatment without anti-OP. BTMs may not reflect BMD change. Regular monitoring of BMD in RA should be considered for early management of osteoporosis.

Computed tomography for malignancy screening in patients with rheumatoid arthritis before initiation of disease modifying antirheumatic drug

OBJECTIVES

This study aimed to clarify the usefulness of screening for malignancies using CT before the initiation of biologic and targeted synthetic DMARDs (b/tsDMARDs) in patients with active RA.

METHODS

We examined 2192 patients with RA who underwent plain CT scans prior to the initiation of b/tsDMARDs. The sensitivity for detecting malignancy was measured and compared with that of regular screening (physical examination and X-ray). We then evaluated the clinical characteristics, prognosis and treatment of patients with RA with concomitant malignancies. Additionally, we determined the incidence rate of malignancy in patients with RA who were initiated on b/tsDMARDs after CT screening.

RESULTS

Of the 2192 patients, 33 (1.5%) were diagnosed with malignancy after CT screening. Whereas regular screening detected only seven malignancies, CT screening further detected 26 (including 19 at the early stage). On the other hand, 86% of the malignancies detectable by regular screening were at an advanced stage. Patients diagnosed with early-stage malignancies received RA treatments that included b/tsDMARDs after curative resection; 80% of these patients achieved low disease activity after 1 year. This rate was comparable to the patients without malignancy detection after screening (70%). The 5 year incidence of malignancy after the initiation of b/tsDMARDs after CT screening was lower than that of the RA cohort without CT screening (standardized incidence ratio: 0.35).

CONCLUSION

Screening in patients with RA using CT before the initiation of b/tsDMARDs allows for the early detection and treatment of malignancy, resulting in safer and more stable b/tsDMARD treatments.

Reduced homovanillic acid, SDF-1α and SCGF-β levels in cerebrospinal fluid are related to depressive states in systemic lupus erythematosus

OBJECTIVE

This study aimed to seek a new method of evaluation and surrogate markers for diffuse neuropsychiatric SLE (NPSLE).

METHODS

We enrolled 44 patients with SLE between 2017 and 2020 who fulfilled at least one of three specific inclusion criteria: high disease activity, abnormal findings (cerebrospinal fluid [CSF] examination, brain MRI, or electroencephalography), or history of neuropsychiatric illness. Psychiatric symptom rating scales (PSYRATS) were evaluated retrospectively. The primary end point was the PSYRATS positivity rate in SLE patients who had not been diagnosed with diffuse NPSLE.

RESULTS

Based on the 1999 ACR classifications, 7 out of the 44 patients evaluated using PSYRATS had been diagnosed with diffuse NPSLE. PSYRATS positivity was seen in 13 out of 37 SLE patients (35.1%) who had not been diagnosed with diffuse NPSLE, and all these patients were positive for Montgomery-Åsberg Depression Rating Scale (MADRS), an indicator of depression state in PSYRATS. Additionally, in the 20 SLE patients exhibiting depression symptoms who were MADRS-positive, CSF concentrations of the neuroinflammatory markers homovanillic acid (HVA; P = 0.0400), stromal cell-derived factor-1α (SDF-1α; P = 0.0431) and stem cell growth factor-β (SCGF-1β; P = 0.0061) were significantly reduced compared with the 24 MADRS-negative SLE patients, and the levels of HVA, SDF-1α and SCGF-1β correlated with one another (P < 0.05).

CONCLUSION

Many patients with active SLE have subclinical depression, and MADRS evaluation of neuropsychiatric symptoms is useful for detecting them. Additionally, the decrease in CSF levels of HVA, SDF-1 α and SCGF-1β reflects the same pathology, and these may serve as surrogate markers.

High-fat-diet-associated intestinal microbiota exacerbates psoriasis-like inflammation by enhancing systemic γδ T cell IL-17 production

Although it is known that psoriasis is strongly associated with obesity, the mechanistic connection between diet and skin lesions is not well established. Herein, we showed that only dietary fat, not carbohydrates or proteins, exacerbates psoriatic disease. Enhanced psoriatic skin inflammation was associated with changes in the intestinal mucus layer and microbiota composition by high-fat diet (HFD). Change of intestinal microbiota by vancomycin treatment effectively blocked activation of psoriatic skin inflammation by HFD, inhibited the systemic interleukin-17 (IL-17) response, and led to increased mucophilic bacterial species such as Akkermansia muciniphila. By using IL-17 reporter mice, we could show that HFD facilitates IL-17-mediated γδ T cell response in the spleen. Notably, oral gavage with live or heat-killed A. muciniphila effectively inhibited HFD-induced enhancement of psoriatic disease. In conclusion, HFD exacerbates psoriatic skin inflammation through changing the mucus barrier and the intestine microbial composition, which leads to an enhanced systemic IL-17 response.

TGF-β3 in differentiation and function of Tph-like cells and its relevance to disease activity in patients with systemic lupus erythematosus

OBJECTIVES

T peripheral helper (Tph) cells have major roles in pathological processes in SLE. We sought to clarify the mechanisms of Tph cell differentiation and their relevance to clinical features in patients with SLE.

METHOD

Phenotypes and functions of Tph cell-related markers in human CD4+ T cells purified from volunteers or patients were analysed using flow cytometry and quantitative PCR. Renal biopsy specimens from patients with LN were probed by multicolour immunofluorescence staining.

RESULTS

Among multiple cytokines, transforming growth factor (TGF)-β3 characteristically induced programmed cell death protein 1 (PD-1)hi musculoaponeurotic fibrosarcoma (MAF)+, IL-21+IL-10+ Tph-like cells with a marked upregulation of related genes including PDCD-1, MAF, SOX4 and CXCL13. The induction of Tph-like cells by TGF-β3 was suppressed by the neutralization of TGF-β type II receptor (TGF-βR2). TGF-β3-induced Tph-like cells efficiently promoted the differentiation of class-switch memory B cells into plasmocytes, resulting in enhanced antibody production. The proportion of Tph cells in the peripheral blood was significantly increased in patients with SLE than in healthy volunteers in concordance with disease activity and severity of organ manifestations such as LN. TGF-β3 was strongly expressed on macrophages, which was associated with the accumulation of CD4+ C-X-C chemokine receptor (CXCR5)-PD-1+ Tph cells, in the renal tissue of patients with active LN.

CONCLUSION

The induction of Tph-like cells by TGF-β3 mainly produced from tissue macrophages plays a pivotal role in the pathological processes of active LN by enhancing B-cell differentiation in patients with SLE.

Malignancies and rheumatoid arthritis, csDMARDs, biological DMARDs, and JAK inhibitors: challenge and outlook

INTRODUCTION

Rheumatoid arthritis (RA) is an autoimmune disorder necessitating immunosuppressive therapy. Remarkable progress has been made in the treatment of RA over recent decades, particularly with the development of biological disease-modifying antirheumatic drugs (bDMARDs) and Janus kinase inhibitors (JAKi). Nonetheless, the development of new drugs has been accompanied by concerns regarding the association between these novel therapies and the risk of malignancy.

AREAS COVERED

This narrative review aims to discuss the understanding of RA, conventional synthetic (cs) DMARDs, bDMARDs, JAKi, and their association with malignancy. Furthermore, the review discusses the management of malignancy in patients receiving b/tsDMARDs.

EXPERT OPINION

Although recent studies suggest that the potential risk of malignancy of methotrexate and a JAKi tofacitinib, it is essential to avoid indiscriminate withholding of treatment by those agents, as this may lead functional impairment and increased mortality. Therefore, the adoption of a Treat-to-Target (T2T) approach considering individual patient characteristics, becomes of utmost importance. Rheumatologists should maintain a vigilant stance regarding malignancy in this context, recognizing the importance of early detection and management. Implementing a screening program for malignancies is indispensable, and the use of computed tomography screening may enhance the effectiveness of management strategies.

Enhancer RNA commits osteogenesis via microRNA-3129 expression in human bone marrow-derived mesenchymal stem cells

Background

Highly regulated gene expression program underlies osteogenesis of mesenchymal stem cells (MSCs), but the regulators in the program are not entirely identified. As enhancer RNAs (eRNAs) have recently emerged as a key regulator in gene expression, we assume a commitment of an eRNA in osteogenesis.

Methods

We performed in silico analysis to identify potential osteogenic microRNA (miRNA) gene predicted to be regulated by super-enhancers (SEs). SE inhibitor treatment and eRNA knocking-down were used to confirm the regulational mechanism of eRNA. miRNA function in osteogenesis was elucidated by miR mimic and inhibitor transfection experiments.

Results

miR-3129 was found to be located adjacent in a SE (osteoblast-specific SE_46171) specifically activated in osteoblasts by in silico analysis. A RT-quantitative PCR analysis of human bone marrow-derived MSC (hBMSC) cells showed that eRNA_2S was transcribed from the SE with the expression of miR-3129. Knockdown of eRNA_2S by locked nucleic acid as well as treatment of SE inhibitors JQ1 or THZ1 resulted in low miR-3129 levels. Overexpression of miR-3129 promoted hBMSC osteogenesis, while knockdown of miR-3129 inhibited hBMSC osteogenesis. Solute carrier family 7 member 11 (SLC7A11), encoding a bone formation suppressor, was upregulated following miR-3129-5p inhibition and identified as a target gene for miR-3129 during differentiation of hBMSCs into osteoblasts.

Conclusions

miR-3129 expression is regulated by SEs via eRNA_2S and this miRNA promotes hBMSC differentiation into osteoblasts through downregulating the target gene SLC7A11. Thus, the present study uncovers a commitment of an eRNA via a miR-3129/SLC7A11 regulatory pathway during osteogenesis of hBMSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41232-022-00228-4.

Prophylaxis against pneumocystis pneumonia in rheumatoid arthritis patients treated with b/tsDMARDs: insights from 3787 cases in the FIRST registry

OBJECTIVES

The use of biologic and targeted synthetic (b/ts) DMARDs in the treatment of RA is increasing. Therefore, prevention of b/tsDMARDs-induced infection is important. Here we describe a prophylaxis protocol for preventing pneumocystis pneumonia (PCP) in RA patients treated with b/tsDMARDs.

METHODS

The study subjects were 3787 RA patients from the FIRST registry. They were divided into cohort 1 (n = 807, requiring prophylaxis against PCP based on physicians' assessment at the point of new treatment with or switch to b/tsDMARDs) and cohort 2 (n = 2980, receiving strategic PCP prophylaxis). The incidence and risk factors for PCP were investigated.

RESULTS

Twenty-six PCP cases were observed throughout the study. After the introduction of strategic PCP prophylaxis, PCP incidence diminished from 0.51/100 person-years (PYs) to 0.21/100 PYs (risk ratio = 0.42). Sulfamethoxazole and trimethoprim in combination (SMX-TMP) showed greater efficacy in the prevention of PCP than pentamidine inhalation (P <0.0001). The prophylaxis rate increased chronologically despite the falls in the average SMX-TMP dose and in the incidence of PCP. Subanalysis of the data for 929 patients from both groups who did not receive prophylaxis showed that old age, high BMI, coexisting lung diseases, low lymphocyte count, and low serum IgG levels increased the risk of PCP development. Development of PCP could be predicted (using an equation based on these variables) in patients not treated with glucocorticoids [area under the curve (AUC) = 0.910)], but less accurately in those on glucocorticoids (AUC = 0.746).

CONCLUSIONS

Our study clarified the risk factors for PCP in RA patients on b/tsDMARDs treatment and highlighted and defined the criteria for effective prophylaxis against PCP.

Impact of serum interleukin-22 as a biomarker for the differential use of molecular targeted drugs in psoriatic arthritis: a retrospective study

BACKGROUND

We explored whether serum cytokines could be used as biomarkers for optimal use of tumor necrosis factor inhibitors (TNF-i) and interleukin (IL)-17 inhibitors (IL-17-i) in patients with psoriatic arthritis (PsA).

METHODS

In cohort 1 (47 patients treated with IL-17-i [n=23] or TNF-i [n=24] for ≥1 year), we identified serum cytokines that predicted the achievement of Disease Activity in Psoriatic Arthritis-remission (DAPSA-REM), Psoriasis Area and Severity Index (PASI) 90, and Minimal Disease Activity after 1 year of TNF-i or IL-17-i therapy. Subsequently, we developed treatment strategies based on the identified cytokines; initiation of IL-17-i therapy in patients with low IL-22 concentrations (IL-22 <0.61376 pg/ml) and TNF-i therapy in patients with high IL-22 concentrations (0.61376< IL-22 pg/ml). In cohort 2 (34 patients), treatment responses were compared between the strategic treatment group (n=17), which was treated based on the treatment strategies, and the mismatched treatment group (n=17) to verify the validity of the treatment strategies developed using serum cytokines as biomarkers.

RESULTS

In cohort 1, serum IL-22 concentration was identified as a predictor of DAPSA-remission after 1 year of IL-17-i therapy. Regarding treatment strategies, we selected TNF-i for patients with high IL-22 concentrations and IL-17-i for those with low IL-22 concentrations. There were no significant differences in the baseline characteristics between the strategic and mismatched treatment groups. Regarding treatment effects, activity significantly improved at 1 year in both groups. Upon comparison of the treatment effects, the rate of achieving DAPSA-REM and Minimal Disease Activity at month 12 was significantly higher in the strategic treatment group.

CONCLUSIONS

The results of this pilot study suggest that IL-22 may be a biomarker of treatment response to TNF-i and IL-17-i in patients with PsA. Further large-scale studies in independent, prospectively collected datasets are required to verify that IL-22 is indeed a biomarker of treatment response in these patients.

Preferable outcome of Janus kinase inhibitors for a group of difficult-to-treat rheumatoid arthritis patients: from the FIRST Registry

Backgrounds

Treatment of difficult-to-treat rheumatoid arthritis (D2T RA) is one of the greatest unmet needs in rheumatology. This study aims to find out preferable treatment options for a group of D2T RA patients who are refractory to multiple biologic and targeted synthetic disease-modifying anti-rheumatic drugs (b/tsDMARDs).

Methods

Data were obtained from patients enrolled in the FIRST Registry who started either TNF inhibitor (TNFi), interleukin-6 receptor inhibitor, cytotoxic T-lymphocyte–associated antigen-4 immunoglobulin, or Janus-kinase inhibitor (JAKi) in the period of August 2013 to December 2020. Those who failed to ≥ 2 and ≥ 3 b/tsDMARDs were categorised as D2T RA and very D2T RA (vD2T RA), respectively. Change in Clinical Disease Activity Index (CDAI) and Health Assessment Questionnaire Disability Index were compared among the groups using propensity-based inverse probability treatment weighted (IPTW) method.

Results

Of 2128 cases included, 353 were categorised as D2T RA. Among the D2T RA, 106 were identified as vD2T RA. JAKi showed a significant improvement in CDAI in the patients with D2T RA and vD2T RA, compared to IPTW-adjusted patients treated with the other 3 regimens. Latent class analysis of the trajectories of treatment response revealed that the proportion of a group of patients who showed poor response was lower among the JAKi subgroup than among those with other subgroups. This superiority of JAKi was more apparent among methotrexate- and glucocorticoid-free individuals. The hazard ratio of severe adverse events was comparable among the four treatment subgroups in both the D2T RA and b/tsDMARD-naïve groups.

Conclusions

This study compared responsiveness to different classes of b/tsDMARDs among D2T RA and vD2T RA patients who were refractory to multiple b/tsDMARDs. The results suggest JAKi is a preferable treatment choice for this type of D2T RA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02744-7.

Efficacy and safety of belimumab during maintenance therapy in patients with systemic lupus erythematosus

Objectives

The efficacy of belimumab (BEL) during maintenance therapy in patients with SLE remains unclear in the real-life clinical setting. This study investigated the efficacy and safety of BEL in patients with SLE during maintenance therapy.

Methods

In this retrospective observational study, maintenance therapy was defined as low-dose glucocorticoid (GC) therapy (prednisolone equivalent dose of ≤0.2 mg/kg/day) in patients with a Safety of Estrogens in Lupus Erythematosus National Assessment-SLE Disease Activity Index (SELENA-SLEDAI) score <10. Participants comprised patients with SLE on HCQ or MMF [standard-of-care (SoC) group: n = 103] and those on BEL plus SoC (BEL+SoC group: n = 100). Selection bias was minimized using propensity score-based inverse probability of treatment weighting (IPTW). GC dose trajectories were modelled using growth mixture modelling (GMM). The primary end point was GC dose at 52 weeks.

Results

No significant difference was observed in patient characteristics between the two groups after IPTW adjustment. The BEL+SoC group exhibited a significant decrease in GC dose. GC dose at 52 weeks and relapse rate were significantly lower in the BEL+SoC group than in the SoC group. The proportion of patients in one of four groups defined by GMM for which GC dose was tapered to 0 mg within 52 weeks (GC tapering-discontinuation group) was significantly higher in the BEL+SoC group than in the SoC group. In the BEL+SoC group, low SELENA-SLEDAI score and low GC dose at baseline were associated with being GC dose-tapering discontinuation.

Conclusion

The present study suggests that BEL is suitable for patients with SLE during maintenance therapy.

T helper cells expressing fractalkine receptor and bearing T follicular helper 1-like cell functions in patients with IgG4-related disease

OBJECTIVE

Since the pathological features of IgG4-related disease (IgG4-RD) include lymphocyte infiltration and fibrotic changes in the lesions, we investigated the significance of fractalkine (CX3CL1) and lymphocyte subsets in patients with IgG4-RD.

METHODS

Peripheral blood and biopsied samples were obtained from healthy controls (HCs, n = 10), rheumatoid arthritis (RA, n = 10), and IgG4-RD patients (n = 16) and were analyzed by flow cytometry, immunohistology and costimulation assays.

RESULTS

Peripheral CX3CR1+ CD4+ T cells had an approximately threefold increase in the IgG4-RD patients (15.4%), compared with the HCs (5.0%). In addition, CX3CR1+ CD4+ T cells were localized in the salivary glands of the IgG4-RD patients but not in those with Sicca syndrome. CX3CR1 was induced on 20% of CD4+ T cells after T cell receptor (TCR) simulation with IL-12 for five days-culture. CX3CR1+ T cells showed high expression of both CXCR5 and CXCR3. Moreover, they co-expressed Bcl-6 and T-bet, the master transcription factors for T helper 1 (Th1) and T follicular helper (Tfh) cells. After secondary stimulation, CX3CR1+ T cells produced both interferon-gamma (IFN-γ) and IL-21. Compared with their CX3CR1- counterparts, CX3CR1+ CD4+ T cells induced plasmablast differentiation from naïve B cells more efficiently (15.0 vs 5.0%) and increased the production of IgG2, IgG3, and IgG4 by B cells.

CONCLUSION

CX3CR1+ CD4+ T cells characteristically increased in the peripheral blood and the affected tissues and were associated with an increase in the serum IgG4 levels of patients with IgG4-RD. This CD4 subset has a Th1/Tfh-like phenotype and a B cell helper function.

mTOR activation in CD8+ cells contributes to disease activity of rheumatoid arthritis and increases therapeutic response to TNF inhibitors

OBJECTIVE

This study aimed to understand the role of mTOR in CD8+ cells in the pathogenicity of rheumatoid arthritis (RA) and the changes after treatment with biologic drugs.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from 17 healthy controls and 86 patients with RA. Phosphorylation of mTOR (p-mTOR) and its clinical relevance were evaluated. The role of mTOR in CD8+ cells was also examined in vitro.

RESULTS

Patients with RA who had a moderate or high disease activity, were biologic-naïve, and were refractory to MTX were enrolled in this study. The p-mTOR levels in CD8+ cells were higher in patients with RA than in healthy controls, and they positively correlated with the disease activity in such patients. However, after one year of treatment with TNF inhibitors, the p-mTOR levels in CD8+ cells were suppressed and showed a positive correlation with the treatment response, which was not observed in the abatacept-treatment group. In vitro stimulation of CD8+ cells with anti-CD3 and anti-CD28 antibodies induced mTOR phosphorylation and increased the production of granzyme B, GNLY, TNF-α, and IFN-γ but decreased the production of granzyme K. However, on treatment with TNF inhibitors, p-mTOR levels in CD8+ cells and granzyme B production decreased, while granzyme K production increased. The production of GNLY and IFN-γ was not affected by the TNF inhibitors.

CONCLUSION

These results suggested that mTOR activation in CD8+ cells may be a novel evaluation marker for RA disease activity and a predictive marker of therapeutic response to TNF inhibitors.

An enhanced mitochondrial function through glutamine metabolism in plasmablast differentiation in systemic lupus erythematosus

OBJECTIVE

To evaluate the dysfunction of B cell metabolism and its involvement in SLE pathology.

METHODS

We assessed the expression of metabolic markers of B cells in the peripheral blood of healthy controls (HCs) and SLE patients by using flow cytometry. In vitro, peripheral B cells were isolated from HCs and SLE patients to investigate the metabolic regulation mechanisms involved in their differentiation.

RESULTS

The expression level of DiOc6 (mitochondrial membrane hyperpolarization) was higher in B cells from SLE patients than in HCs, and correlated to the percentage of plasmablasts in CD19+ cells and with SLEDAI, a disease activity score. Stimulation of CD19+ cells with the Toll-like receptor 9 (TLR9) ligand CpG and IFN-α enhanced glycolysis, oxidative phosphorylation (OXPHOS), DiOc6 expression, and plasmablast differentiation in vitro. In the absence of glutamine, both glycolysis and OXPHOS were reduced, and plasmablast differentiation was suppressed, whereas there was no change in the absence of glucose. As glutamine is an important nutrient for protein synthesis, we further investigated the effect of the glutaminase inhibitor BPTES, which inhibits glutamine degradation, on metabolic regulation. BPTES reduced DiOc6 expression, OXPHOS, reactive oxygen species (ROS) production, ATP production, plasmablast differentiation without affecting glycolysis. Metformin inhibited CpG- and IFN-α-induced glutamine uptake, mitochondrial functions and suppressed plasmablast differentiation.

CONCLUSIONS

Mitochondrial dysfunction in B cells is associated with plasmablast differentiation and disease activity in SLE. Enhanced mitochondrial functions mediated by glutamine metabolism are important for plasmablast differentiation, which may be a potential therapeutic target for SLE.

Pathological role of activated mTOR in CXCR3+ memory B cells of rheumatoid arthritis

OBJECTIVES

B cells play an important pathological role in rheumatoid arthritis (RA). In this study, we investigated the role of metabolic regulator mTOR in B cells and its relevance to the pathology of RA.

METHODS

Peripheral blood mononuclear cells were isolated from 31 normal subjects and 86 RA patients and the gated B cells were assessed for mTOR phosphorylation and chemokine receptor expression. In vitro studies on peripheral blood B cells isolated from the control and RA patients investigated the molecular mechanisms.

RESULTS

Higher concentrations of CXCL10 (CXCR3 ligands) and lower percentages of CXCR3+ memory B cells were present in the peripheral blood of RA patients relative to the control. RA patients with high CXCL10 concentrations had smaller percentage of CXCR3+ memory B cells and high disease activity. One-year treatment with TNF inhibitors increased the percentage of CXCR3+ memory B cells and reduced serum CXCL10 concentrations. mTOR phosphorylation in B cells was further enhanced in RA patients, compared to the control, and was selectively enhanced in CXCR3+ memory B cells. mTOR phosphorylation in CXCR3+ memory B cells correlated with disease activity. In vitro, mTOR phosphorylation in B cells enhanced IL-6 production and increased RANKL expression.

CONCLUSION

mTOR activation in CXCR3+ memory B cells of RA patients is associated with disease activity, mediated through IL-6 production and RANKL expression. The obtained results also suggest that TNF inhibitors mediate an impact on the association between CXCL10 and mTOR activated CXCR3+ memory B cells.

Thermophilic Enterococcus faecium QU 50 enabled open repeated batch fermentation for l-lactic acid production from mixed sugars without carbon catabolite repression

Thermophilic lactic acid bacterium enabled homo-l-lactic acid fermentation from hexose/pentose without carbon catabolite repression, and open repeated production by immobilization.

Nutrition-adaptive control of multiple-bacteriocin production by Weissella hellenica QU 13

AIM

To analyse nutrition-adaptive multiple-bacteriocin production by Weissella hellenica QU 13.

METHODS AND RESULTS

Weissella hellenica QU 13 produces two leaderless bacteriocins, weissellicins Y and M. Their production was studied in MRS and APT media by quantification analyses with liquid chromatography mass spectrometry (LC/MS), while transcriptional analysis of biosynthetic genes was performed by real-time reverse transcription (RT)-PCR. Weissellicin Y production was higher in MRS culture than in APT culture, while weissellicin M production was higher in APT culture than in MRS culture. APT medium contains a higher amount of thiamine than MRS medium, to enhance the growth of heterofermentative lactic acid bacteria. Therefore, thiamine addition to MRS culture enhanced the growth of W. hellenica QU 13; consequently, weissellicin Y production was decreased, while weissellicin M production was not affected. Furthermore, real-time RT-PCR analyses indicated that the transcriptional trends of their respective structural genes, welY and welM, were different from each other, and that these two genes' transcriptions responded to nutrition conditions.

CONCLUSION

Weissella hellenica QU 13 was demonstrated to control weissellicins Y and M production based on nutrition conditions. In addition, differential expression behaviour of weissellicins Y and M indicates that each of them would have separate roles to adapt to different environmental situations.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report that describes nutrition-adaptive multiple-bacteriocin production, in which thiamine inhibits bacteriocin production while it enhances the growth of the producer strain.

[Mesenchymal stem cells for the treatment and repair of inflammatory arthritis]

Mesenchymal stem cells (MSCs) possess multipotent capacity and exhibit immunoregulatory properties. In particular, MSCs can be easily isolated from various organs, can differentiate into various types of cells and generate regulatory T cells. Using human MSC derived from bone marrow and adipose tissue, we have clarified the following novel findings in vitro. 1) MSCs differentiated into osteoblasts or osteocytes under osteoblast-conditioned medium including the inflammatory stimuli such as IL-1. 2) The combination of IL-6 and soluble IL-6 receptor induced differentiation of MSCs to chondrocyte, whereas IL-17 inhibited their differentiation. 3) MSCs highly produced osteoprotegerin and inhibited osteoclastogenesis. Furthermore, we developed a local delivery system of MSCs by using nano-fiber scaffold. MSCs seeded on nano-fiber scaffold suppressed arthritis and bone destruction due to inhibition of systemic inflammatory reaction and immune response by suppressing T cell proliferation and reducing anti-type II collagen antibody production in vivo. Thus, our data may serve as a new strategy for MSC-based therapy in inflammatory diseases and an alternative delivery method for the treatment of destruction of bone and joints.

Spontaneous Differentiation of Human Mesenchymal Stem Cells on Poly-Lactic-Co-Glycolic Acid Nano-Fiber Scaffold

Introduction

Mesenchymal stem cells (MSCs) have immunosuppressive activity and can differentiate into bone and cartilage; and thus seem ideal for treatment of rheumatoid arthritis (RA). Here, we investigated the osteogenesis and chondrogenesis potentials of MSCs seeded onto nano-fiber scaffolds (NFs) in vitro and possible use for the repair of RA-affected joints.

Methods

MSCs derived from healthy donors and patients with RA or osteoarthritis (OA) were seeded on poly-lactic-glycolic acid (PLGA) electrospun NFs and cultured in vitro.

Results

Healthy donor-derived MSCs seeded onto NFs stained positive with von Kossa at Day 14 post-stimulation for osteoblast differentiation. Similarly, MSCs stained positive with Safranin O at Day 14 post-stimulation for chondrocyte differentiation. Surprisingly, even cultured without any stimulation, MSCs expressed RUNX2 and SOX9 (master regulators of bone and cartilage differentiation) at Day 7. Moreover, MSCs stained positive for osteocalcin, a bone marker, and simultaneously also with Safranin O at Day 14. On Day 28, the cell morphology changed from a spindle-like to an osteocyte-like appearance with processes, along with the expression of dentin matrix protein-1 (DMP-1) and matrix extracellular phosphoglycoprotein (MEPE), suggesting possible differentiation of MSCs into osteocytes. Calcification was observed on Day 56. Expression of osteoblast and chondrocyte differentiation markers was also noted in MSCs derived from RA or OA patients seeded on NFs. Lactic acid present in NFs potentially induced MSC differentiation into osteoblasts.

Conclusions

Our PLGA scaffold NFs induced MSC differentiation into bone and cartilage. NFs induction process resembled the procedure of endochondral ossification. This finding indicates that the combination of MSCs and NFs is a promising therapeutic technique for the repair of RA or OA joints affected by bone and cartilage destruction.

Contribution of the Interleukin-6/STAT-3 Signaling Pathway to Chondrogenic Differentiation of Human Mesenchymal Stem Cells

OBJECTIVE

Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into chondrocytes. Articular cartilage contains MSC-like chondroprogenitor cells, which suggests their involvement in the maintenance of cartilage homeostasis by a self-repair mechanism. Interleukin-6 (IL-6) is a cytokine with a wide range of physiologic functions, which are produced by MSCs in a steady manner and in large quantities. The purpose of this study was to investigate the involvement of IL-6 signaling in MSC differentiation into chondrocytes.

METHODS

Human bone marrow-derived MSCs were cultured using a pellet culture system in medium containing transforming growth factor β3. Chondrogenic differentiation was detected by cartilage matrix accumulation and chondrogenic marker gene expression.

RESULTS

IL-6 was detected at a high concentration in culture supernatants during chondrogenic differentiation. The expression of the IL-6 receptor (IL-6R) was significantly increased, accompanied by markedly increased phosphorylation and expression of STAT-3. Addition of IL-6 and soluble IL-6R (sIL-6R) to the chondrogenic culture resulted in concentration-dependent increases in cartilage matrix accumulation and cartilage marker gene expression (type II collagen/aggrecan/type X collagen). Phosphorylation of the master transcription factor SOX9 was enhanced upon addition of IL-6 and sIL-6R. STAT-3 knockdown suppressed chondrogenic differentiation. IL-6 and the MSC markers CD166 and nestin were colocalized in macroscopically normal human cartilage taken from the lateral femoral compartment of knees with medial tibiofemoral osteoarthritis.

CONCLUSION

During differentiation of human MSCs into chondrocytes, the activation of IL-6/STAT-3 signaling positively regulated chondrogenic differentiation. The presence of IL-6 around MSC-like cells in the cartilage tissue was identified, suggesting that IL-6 contributes to homeostasis and cartilage self-repair by promoting chondrogenic differentiation.

IL-6-accelerated calcification by induction of ROR2 in human adipose tissue-derived mesenchymal stem cells is STAT3 dependent

OBJECTIVE

The mechanisms of ectopic calcification in inflammatory diseases are poorly understood. We investigated the effects of inflammatory cytokines on the mechanisms of calcification in human adipose tissue-derived mesenchymal stem cells (hADSCs).

METHODS

The effects of inflammatory cytokines were evaluated using hADSCs cultured in osteoblast induction medium. mRNA expression was measured by real-time PCR and protein levels were measured by western blotting. Cell mineralization was evaluated by Alizarin Red S staining.

RESULTS

In hADSCs, administration of IL-6/soluble IL-6 receptor (sIL-6R), TNF or IL-1β accelerated calcification through enhanced expression of an osteoblast differentiation marker, runt-related transcription factor 2 (RUNX2). IL-6/sIL-6R had the greatest effect. The transcription of mRNA for receptor tyrosine kinase-like orphan receptor 2 (ROR2), involved in the non-canonical wingless-type (WNT) MMTV integration site pathway, was increased, while β-catenin expression, an essential factor in the canonical WNT signalling pathway for osteoblast differentiation, did not change. Suppression of signal transducer and activator of transcription 3 (STAT3), but not STAT1, by small interfering RNA (siRNA) exerted a strong inhibitory effect on RUNX2 and ROR2 expression, and inhibited accelerated calcification.

CONCLUSION

IL-6/sIL-6R stimulation accelerated the ROR2/WNT5A pathway in hADSCs in a STAT3-dependent manner, resulting in augmented calcification. These results suggest that the mechanisms of ectopic calcification accelerated by IL-6 in hADSCs may be involved in chronic inflammatory tissues and that IL-6 inhibitors may be beneficial in the treatment of ectopic calcification in inflammatory diseases.

IL-17 inhibits chondrogenic differentiation of human mesenchymal stem cells

OBJECTIVE

Mesenchymal stem cells (MSCs) can differentiate into cells of mesenchymal lineages, such as osteoblasts and chondrocytes. Here we investigated the effects of IL-17, a key cytokine in chronic inflammation, on chondrogenic differentiation of human MSCs.

METHODS

Human bone marrow MSCs were pellet cultured in chondrogenic induction medium containing TGF-β3. Chondrogenic differentiation was detected by cartilage matrix accumulation and chondrogenic marker gene expression.

RESULTS

Over-expression of cartilage matrix and chondrogenic marker genes was noted in chondrogenic cultures, but was inhibited by IL-17 in a dose-dependent manner. Expression and phosphorylation of SOX9, the master transcription factor for chondrogenesis, were induced within 2 days and phosphorylated SOX9 was stably maintained until day 21. IL-17 did not alter total SOX9 expression, but significantly suppressed SOX9 phosphorylation in a dose-dependent manner. At day 7, IL-17 also suppressed the activity of cAMP-dependent protein kinase A (PKA), which is known to phosphorylate SOX9. H89, a selective PKA inhibitor, also suppressed SOX9 phosphorylation, expression of chondrogenic markers and cartilage matrix, and also decreased chondrogenesis.

CONCLUSIONS

IL-17 inhibited chondrogenesis of human MSCs through the suppression of PKA activity and SOX9 phosphorylation. These results suggest that chondrogenic differentiation of MSCs can be inhibited by a mechanism triggered by IL-17 under chronic inflammation.

Identification and characterization of novel multiple bacteriocins produced by Lactobacillus sakei D98

AIM

To characterize novel multiple bacteriocins produced by Lactobacillus sakei D98.

METHODS AND RESULTS

Lactobacillus sakei D98 isolated from Shubo (rice malt) produced at least three bacteriocins. Using three purification steps, three novel antimicrobial peptides termed sakacin D98a, sakacin D98b and sakacin D98c were purified from the culture supernatant. Amino acid and DNA sequencing analysis revealed that the sakacins D98a, D98b and D98c are novel class IIa-like or class IId bacteriocins. In particular, sakacin D98b has a variant pediocin-box sequence, YANGVXC (with Ala instead of Gly), and a different location for the disulfide bridge (Cys(11) and Cys(18)) from that found in other class IIa bacteriocins.

CONCLUSIONS

Three novel bacteriocins were identified from Lactobacillus sakei D98. Their antimicrobial spectra and intensities indicate that these sakacins would have different modes of action. In addition, sakacin D98b showed low inhibitory activity against Listeria, probably due to the differences in amino acids and position of the disulfide bridge compared with the other class IIa bacteriocins.

SIGNIFICANCE AND IMPACT OF STUDY

Sakacins D98a and D98c are novel bacteriocins belonging to class IId bacteriocins. On the other hand, sakacin D98b, a class IIa-like bacteriocin, has a unique internal structure and activity spectrum.

Interleukin-1β induces differentiation of human mesenchymal stem cells into osteoblasts via the Wnt-5a/receptor tyrosine kinase-like orphan receptor 2 pathway

OBJECTIVE

Mesenchymal stem cells (MSCs) are considered to be a novel tool for the treatment of rheumatoid arthritis (RA) because of their multipotency to differentiate into osteoblasts and chondrocytes, their immunosuppressive effects, and availability. The aim of this study was to assess the mechanisms of human MSC differentiation into osteoblasts under inflammatory conditions.

METHODS

Human MSCs were cultured in commercialized osteogenic induction medium with inflammatory cytokines for up to 10 days. Osteoblast differentiation was detected by alkaline phosphatase staining and messenger RNA (mRNA) expression of multiple osteoblast markers. Mineralization was assessed by alizarin red S staining.

RESULTS

Among the various cytokines tested, interleukin-1β (IL-1β) induced differentiation of human MSCs into osteoblasts, which was confirmed by alkaline phosphatase activity, expression of RUNX2 mRNA, and strong alizarin red S staining. Among various molecules of the Wnt family, Wnt-5a and receptor tyrosine kinase-like orphan receptor 2 (Ror2), a major receptor of Wnt-5a, were significantly induced in human MSCs by IL-1β. Silencing of either WNT5A or ROR2 by small interfering RNA with 2 different sequences reduced alkaline phosphatase activity, RUNX2 expression, and alizarin red S staining of human MSCs induced by IL-1β.

CONCLUSION

IL-1β effectively and rapidly induced human MSC differentiation into osteoblasts and mineralization, mainly through the noncanonical Wnt-5a/Ror2 pathway. These results suggest potential benefits of IL-1β-treated human MSCs in the treatment of damaged bone as well as in the induction of self-renewal and self-repair of damaged tissue, including osseous tissue.

Dermal mast cell density in fingers reflects severity of skin sclerosis in systemic sclerosis

BACKGROUND

Systemic sclerosis (SSc) is characterized by skin sclerosis, which develops from the distal extremities and spreads to the trunk. Although several reports have implied the involvement of mast cells in SSc based on examination of forearm skin specimens, there have been no studies that examined digital skin specimens.

METHODS

Skin biopsies were obtained from the distal one-third of the forearm and between distal and proximal interphalangeal joints from 46 SSc patients, as well as from 29 non-SSc patients and normal controls. Dermal mast cells were detected histologically using NanoZoomer digital pathology.

RESULTS

Dermal mast cell density was significantly higher in both the forearms and fingers in SSc patients compared with non-SSc patients and normal controls. Digital dermal mast cell density was significantly higher in patients with diffuse cutaneous SSc than in local cutaneous SSc patients and also in the anti-topoisomerase I antibody-positive group than in the negative group, though such tendency was not noted in the forearm dermis. Interestingly, digital dermal mast cell density tended to correlate negatively but significantly with disease duration, suggesting the possible involvement of dermal mast cells in the early pathological process.

CONCLUSION

Digital accumulation of toluidine blue- and/or c-Kit-positive dermal mast cells appears to be involved in the early stages of the pathological processes of SSc, especially in patients positive for anti-topoisomerase I antibody.

New type non-lantibiotic bacteriocins: circular and leaderless bacteriocins

Bacteriocins are antimicrobial peptides that are ribosomally synthesised by bacteria. Bacteriocins produced by Gram-positive bacteria, including lactic acid bacteria, are under focus as the next generation of safe natural biopreservatives and as therapeutic alternatives to antibiotics. Recently, two novel types of non-lantibiotic class II bacteriocins have been reported with unique characteristics in their structure and biosynthesis mechanism. One is a circular bacteriocin that contains a head-to-tail structure in the mature form, and the other is a leaderless bacteriocin without an N-terminal extension in the precursor peptide. A circular structure can provide the peptide with remarkable stability against various stresses; indeed, circular bacteriocins are known to possess higher stability than general linear bacteriocins. Leaderless bacteriocins are distinct from general bacteriocins, because they do not contain N-terminal leader sequences, which are responsible for the recognition process during secretion and for inactivation of bacteriocins inside producer cells. Leaderless bacteriocins do not require any post-translational processing for activity. These two novel types of bacteriocins are promising antimicrobial compounds, and their biosynthetic mechanisms are expected to be applied in synthetic biology to design new peptides and for new mass production systems. However, many questions remain about their biosynthesis. In this review, we introduce recent studies on these types of bacteriocins and their potential to open a new world of antimicrobial peptides.

[Anti-rheumatic effect of JAK-inhibitors]

Treatment of rheumatoid arthritis (RA) has dramatically developed with the use of biologics targeting inflammatory cytokines. However, expense and parenteral use can cause issues in the initiation and continuation of the treatment. Therefore a new orally available anti-rheumatic drug has been long-awaited. Recently, small-molecule compounds targeting Janus kinase (JAK) has shown clinical efficacy similar to biologics in clinical trials for active RA. Among the JAK-inhibitors, new drug application for tofacitinib is concurrently under review in western and asian countries and is highly expected to become a new anti-rheumatic drug in the near future. In order to evaluate the mode of action, we utilized peripheral blood and synovium from RA patients. Proliferation and cytokine production of CD4+ T cell was prominently reduced and subsequently inhibited cartilage destruction by the synovium. Our result is in line with the inhibitory effect of tofacitinib on joint destruction in RA patients those who were treated with tofacitinib. Therefore, further clinical efficacy is expected in the in the long-term treatment with tofacitinib.

Characterization and identification of weissellicin Y and weissellicin M, novel bacteriocins produced by Weissella hellenica QU 13

AIMS

To identify and characterize novel bacteriocins from Weissella hellenica QU 13.

METHODS AND RESULTS

Weissella hellenica QU 13, isolated from a barrel used to make Japanese pickles, produced two novel bacteriocins termed weissellicin Y and weissellicin M. The primary structures of weissellicins Y and M were determined, and their molecular masses were determined to be 4925·12 and 4968·40 Da, respectively. Analysis of the DNA sequence encoding the bacteriocins revealed that they were synthesized and secreted without N-terminal extensions such as leader sequences or sec signal peptides. Weissellicin M showed significantly high and characteristic homology with enterocins L50A and L50B, produced by Enterococcus faecium L50, while weissellicin Y showed no homology with any other known bacteriocins. Both bacteriocins showed broad antimicrobial spectra, with especially high antimicrobial activity against species, which contaminate pickles, such as Bacillus coagulans, and weissellicin M showed relatively higher activity than weissellicin Y. Furthermore, the stability of weissellicin M against pH and heat was distinctively higher than that of weissellicin Y.

CONCLUSIONS

Weissella hellenica QU 13 produced two novel leaderless bacteriocins, weissellicin Y and weissellicin M, and weissellicin M exhibited remarkable potency that could be employed by pickle-producing industry.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first report, which represents a complete identification and characterization of novel leaderless bacteriocins from Weissella genus.