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Background mRNA-based COVID-19 vaccines have short- and long-term efficacy in healthy individuals, but their efficacy in patients with psoriasis receiving immunomodulatory therapy is less studied. Objectives To investigate long-term immunity after COVID-19 vaccination in patients with psoriasis receiving immunomodulatory therapy. Methods A prospective cohort study including patients (n = 123) with psoriasis receiving methotrexate (MTX) or biologics and controls (n = 226). Only mRNA-based COVID-19 vaccines administered with standard intervals between doses were investigated. Markers of immunity included SARS-CoV-2 spike glycoprotein-specific IgG and IgA, neutralizing capacity, and interferon-γ release from T cells stimulated with peptides of the SARS-CoV-2 spike glycoprotein. Results The proportion of IgG responders was lower 6 months after vaccination in patients receiving anti-tumour necrosis factor (TNF) treatment compared with controls. Anti-TNF treatment was associated with lower IgG levels (β = −0.82, 95% confidence interval −1.38 to −0.25; P = 0.001). The median neutralizing index was lower in the anti-TNF group [50% inhibition (interquartile range [IQR] 37–89)] compared with controls [98% inhibition (IQR 96–99)]; P < 0.001. Cellular responses were numerically lowest in the anti-TNF group. Conclusions Treatment with anti-TNF has an impact on the immunity elicited by mRNA-based COVID-19 vaccination in patients with psoriasis, resulting in a faster waning of humoral and cellular markers of immunity; however, the clinical implications are unknown.

(1) Background: Here, we investigate the incidence of mpox and factors associated with vaccine uptake in mainly well-treated men who have sex with men and are living with HIV (MSMWH). (2) Methods: This study included 727 MSMWH from the Copenhagen co-morbidity in HIV infection (COCOMO) study from 1 May to 31 October 2022. Mpox infection and vaccination status were obtained from the Danish Microbiology Database and The Danish Vaccination Register. Vaccination willingness was assessed through an online survey. (3) Results: At a median follow-up of 180 days, 13 (1.8%) participants had laboratory-confirmed mpox infections. Furthermore, 238 (32.7%) had received the mpox vaccine. A sexually transmitted disease (STD) in the preceding two years was associated with a higher risk of mpox infection (hazard ratio 7.1; 95% confidence interval (CI) [1.9–26.9]) and with higher odds of vaccination (adjusted odds ratio 3.1; 95% CI [2.2–4.6]). 401 (55.2%) participants responded to the survey. 228 (57.0%) reported very high vaccination willingness. The self-perceived risk of infection was associated with vaccine uptake. (4) Conclusions: The incidence of mpox was low. A prior STD was associated with both a higher risk of mpox infection and higher odds of vaccination. Despite high-risk sexual behavior and high vaccination willingness, a sizable fraction of participants had not been vaccinated.

Knowledge about the persistence of salivary immunity after SARS-CoV-2 vaccination is limited, and information on this topic could prove important for vaccine strategy and development. We hypothesized that salivary immunity would wane rapidly after vaccination.

Background Coronavirus disease 2019 (COVID-19) vaccines are implemented worldwide in efforts to curb the pandemic. This study investigates the risk of a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcriptase polymerase chain reaction (RT-PCR) test following BNT162b2 vaccination in a large real-life population in Denmark. Methods Vaccination status and positive SARS-CoV-2 RT-PCR results from adults in the Capital Region of Denmark (n = 1 549 488) were obtained from national registries. PCR testing was free and widely available. The number of positive PCR tests per individual at risk was calculated as weekly rates. Time to positive PCR test was modelled using Kaplan-Meier methods and hazard ratios (HRs) were calculated using Cox regression. Results A total of 1 119 574 individuals received the first dose of BNT162b2 and 1 088 879 received a second dose of BNT162b2. Individuals were followed up to 8.7 months after first dose (median: 5.5 months; interquartile ratio: 4.1–8.7). Rates of PCR-confirmed SARS-CoV-2 infection 2–4 months after the second dose were 0.21, 0.33, and 0.36 per 1000 individuals per week at risk for July, August, and September, respectively. Four or more months after the second dose, the rates were 0.56, 0.76, and 0.53 per 1000 individuals per week at risk for July, August, and September, respectively. HR of SARS-CoV-2 infection after the second dose was 0.2 (95% confidence interval, .05–.48; P = .001) for individuals with 8 months’ follow-up. Conclusions Individuals who received 2 doses of the BNT162b2 COVID-19 vaccine had a low risk of breakthrough infection after up to 8 months of follow-up. However, there was a tendency toward higher rates with longer follow-up.

Background: People with HIV (PWH) are at increased risk of severe COVID-19. We aimed to determine humoral responses in PWH and controls who received two doses of BNT162b2. Methods: In 269 PWH and 538 age-matched controls, we measured IgG and neutralizing antibodies specific for the receptor-binding domain of SARS-CoV-2 at baseline, 3 weeks and 2 months after the first dose of BNT162b2. Results: IgG antibodies increased from baseline to 3 weeks and from 3 weeks to 2 months in both groups, but the concentrations of IgG antibodies were lower in PWH than that in controls at 3 weeks and 2 months (p = 0.025 and

IntroductionResponses to COVID-19 vaccination in patients with chronic pulmonary diseases are poorly characterised. We aimed to describe humoral responses following two doses of BNT162b2 mRNA COVID-19 vaccine and identify risk factors for impaired responses.MethodsProspective cohort study including adults with chronic pulmonary diseases and healthcare personnel as controls (1:1). Blood was sampled at inclusion, 3 weeks, 2 and 6 months after first vaccination. We reported antibody concentrations as geometric means with 95% CI of receptor binding domain (RBD)-IgG and neutralising antibody index of inhibition of ACE-2/RBD interaction (%). A low responder was defined as neutralising index in the lowest quartile (primary outcome) or RBD-IgG ResultsWe included 593 patients and 593 controls, 75% of all had neutralising index ≥97% at 2 months. For the primary outcome, 34.7% of patients (n=157/453) and 12.9% of controls (n=46/359) were low responders (pDiscussionPatients with chronic pulmonary diseases established functional humoral responses to vaccination, however lower than controls. Age, comorbidities and immunosuppression were associated with poor immunological responses.

BackgroundPrevious studies have indicated inferior responses to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccination in solid organ transplant (SOT) recipients. We examined the development of anti-receptor-binding domain (RBD) immunoglobulin G (IgG) after two doses of BNT162b2b in SOT recipients 6 months after vaccination and compared to that of immunocompetent controls.MethodsWe measured anti-RBD IgG after two doses of BNT162b2 in 200 SOT recipients and 200 matched healthy controls up to 6 months after first vaccination. Anti-RBD IgG concentration and neutralizing capacity of antibodies were measured at first and second doses of BNT162b2 and 2 and 6 months after the first dose. T-cell responses were measured 6 months after the first dose.ResultsIn SOT recipients, geometric mean concentration (GMC) of anti-RBD IgG increased from first to second dose (1.14 AU/ml, 95% CI 1.08–1.24 to 11.97 AU/ml, 95% CI 7.73–18.77) and from second dose to 2 months (249.29 AU/ml, 95% CI 153.70–385.19). Six months after the first vaccine, anti-RBD IgG declined (55.85 AU/ml, 95% CI 36.95–83.33). At all time points, anti-RBD IgG was lower in SOT recipients than that in controls. Fewer SOT recipients than controls had a cellular response (13.1% vs. 59.4%, p < 0.001). Risk factors associated with humoral non-response included age [relative risk (RR) 1.23 per 10-year increase, 95% CI 1.11–1.35, p < 0.001], being within 1 year from transplantation (RR 1.55, 95% CI 1.30–1.85, p < 0.001), treatment with mycophenolate (RR 1.54, 95% CI 1.09–2.18, p = 0.015), treatment with corticosteroids (RR 1.45, 95% CI 1.10–1.90, p = 0.009), kidney transplantation (RR 1.70, 95% CI 1.25–2.30, p = 0.001), lung transplantation (RR 1.63, 95% CI 1.16–2.29, p = 0.005), and de novo non-skin cancer comorbidity (RR 1.52, 95% CI, 1.26–1.82, p < 0.001).ConclusionImmune responses to BNT162b2 are inferior in SOT recipients compared to healthy controls, and studies aiming to determine the clinical impact of inferior vaccine responses are warranted.

The MYC oncogene drives T- and B- lymphoid malignancies, including Burkitt’s lymphoma (BL) and Acute Lymphoblastic Leukemia (ALL). Here, we demonstrate a systemic reduction in natural killer (NK) cell numbers in SRα-tTA/Tet-O-MYCON mice bearing MYC-driven T-lymphomas. Residual mNK cells in spleens of MYCON T-lymphoma-bearing mice exhibit perturbations in the terminal NK effector differentiation pathway. Lymphoma-intrinsic MYC arrests NK maturation by transcriptionally repressing STAT1/2 and secretion of Type I Interferons (IFNs). Treating T-lymphoma-bearing mice with Type I IFN improves survival by rescuing NK cell maturation. Adoptive transfer of mature NK cells is sufficient to delay both T-lymphoma growth and recurrence post MYC inactivation. In MYC-driven BL patients, low expression of both STAT1 and STAT2 correlates significantly with the absence of activated NK cells and predicts unfavorable clinical outcomes. Our studies thus provide a rationale for developing NK cell-based therapies to effectively treat MYC-driven lymphomas in the future., Oncogene addiction is considered as a cancer cell-autonomous phenomenon, but can also influence the host immune system. Here the authors show that MYC-driven lymphomagenesis is associated with a block in the maturation and effector functions of natural killer cells as a mechanism of tumor escape from immunosurveillance.

The chronic joint inflammation in axial spondyloarthritis (axSpA) is characterized by infiltration of activated macrophages. The haptoglobin-hemoglobin receptor CD163 and the mannose receptor CD206 are strongly expressed on M2c and M2a macrophages, respectively. We measured the soluble forms of the receptors (sCD163 and sCD206) in plasma (PL) in two axSpA cohorts. All patients fulfil the 2009 Assessment of SpondyloArthritis International Society (ASAS) classification criteria for axSpA and/or the 1984 modified New York criteria for ankylosing spondylitis. The first cohort included anti-TNF-α treated patients with active axSpA (n = 30); the second cohort included patients in early disease stages (n = 38). Plasma sCD163 and sCD206 were both within the reference interval of healthy controls (HC), but sCD163 decreased slightly during anti-TNF-α treatment [baseline: 1.49 mg/L (IQR: 1.22-1.77 mg/L, 12 weeks: 1.29 (IQR: 1.09-1.57) mg/L, 20 weeks: 1.25 (IQR: 0.99-1.75) mg/L, 52 weeks: 1.39 (IQR: 1.15-1.78) mg/L], while sCD206 increased [baseline: 0.17 (IQR: 0.13-0.21) mg/L, 12 weeks: 0.19 (0.16-0.23) mg/L, 20 weeks: 0.20 (0.14-0.24) mg/L, 52: 0.19 (IQR: 0.14-0.23) mg/L], pointing toward a shift in polarization of involved macrophages. Plasma levels of sCD206 proved significantly higher in patients with early disease stages and definite radiological sacroiliitis (n = 10). This was not the case for sCD163. A significant increase in response to anti-TNF-α treatment, could suggest sCD206 as a marker of response to anti-TNF-α treatment, however, the potential for the two macrophage markers as diagnostic and prognostic indicators of disease in axSpA is weak.

Background: Apremilast (Otezla®) is a phosphodiesterase 4 (PDE4) inhibitor approved for the treatment of psoriasis and psoriatic arthritis (PsA), but the reason why apremilast shows clinical effect is not fully understood. The objective of this study was to study the downstream effects of apremilast on cells of inflamed joints in immune-mediated inflammatory arthritis. Methods: Synovial fluid was obtained from patients with active rheumatoid arthritis (RA), PsA or peripheral spondyloarthritis (SpA; n = 18). The in vitro models consisted of synovial fluid mononuclear cells (SFMCs) or fibroblast-like synovial cells (FLSs) cultured for 48 h, SFMCs cultured for 21 days, an osteoclast pit formation assay, and a mineralization assay. Results: In SFMCs cultured for 48 h, apremilast decreased the production of interleukin (IL)-12/IL-23p40 (the shared subunit of IL-12 and IL-23), colony-stimulating factor 1, CD6, and CD40 and increased the production of C-X-C motif chemokine 5 dose-dependently. Apremilast had a very different response signature compared with the tumor necrosis factor alpha inhibitor adalimumab with a substantially greater inhibition of IL-12/IL-23p40. In SFMCs cultured for 21 days, apremilast increased the secretion of IL-10. In FLS cultures, apremilast decreased matrix metalloproteinase-3 production. Apremilast decreased osteoclastogenesis but did not affect mineralization by human osteoblasts. Conclusion: This study reveals the downstream effects of apremilast in ex vivo models of arthritis with a strong inhibition of IL-12/IL-23p40 by SFMCs. Our findings could explain some of the efficacy of apremilast seen in IL-12/IL-23-driven immune-mediated inflammatory diseases such as psoriasis and PsA.

The MYC oncogene drives T and B lymphoid malignancies, including Burkitt’s lymphoma (BL) and Acute Lymphoblastic Leukemia (ALL). Using CyTOF, we demonstrate a systemic reduction in natural killer (NK) cell-mediated surveillance inSRα-tTA/Tet-O-MYCONmice bearing MYC-driven T-lymphomas, due to an arrest in NK cell maturation. Inactivation of lymphoma-intrinsic MYC releases the brakes on NK maturation restoring NK homeostasis. Lymphoma-intrinsic MYC arrests NK maturation by transcriptionally repressing STAT1/2 and secretion of Type I Interferons (IFNs). Treating T-lymphoma-bearing mice with Type I IFN improves survival by rescuing NK cell maturation. In MYC-driven BL patients, low expression of both STAT1 and STAT2 correlates significantly with the absence of activated NK cells and predicts unfavorable clinical outcomes. Adoptive transfer of mature NK cells is sufficient to delay both T-lymphoma growth and recurrence post MYC inactivation. Our studies thus provide a rationale for developing NK cell-based therapies to effectively treat MYC-driven lymphomas in the future.Abbreviations:CyTOFCytometry Time of FlightBLBurkitt’s LymphomaALLAcute Lymphoblastic LeukemiaDLBCLDiffuse Large B Cell LymphomaNK CellNatural Killer CellSTAT1/2Signal Transducer and Activator of Transcription 1/2IFNInterferonDCDendritic CellMYCv-myc avian myelocytomatosis viral oncogene homologPRECOGPrediction of Clinical Outcomes from Genomic ProfilesBLIBioluminescence ImagingTSSTranscriptional Start SiteHTLVHuman T-lymphotropic VirushMYChuman MYC

Background Targeting intracellular pathways with oral small molecules is an attractive therapeutic approach for treating immune mediated inflammatory diseases. The mitogen-activated protein kinase (MAPK) pathway is activated by environmental stressors, growth factors and inflammatory cytokines. However, the inhibition of central MAPK proteins has so far had undesirable side effects. The MAPK-activated protein kinase 2 (MK2) is a downstream mediator in the MAPK signalling pathway and could therefore be inhibited without the same side effects (see figure 1). Objectives The objective of this study was to study the effects of a small molecule inhibiting MK2 on inflammation and structural changes in ex vivo models of immune mediated inflammatory arthritis. Methods Synovial fluid mononuclear cells (SFMCs), fibroblast like synovial cells (FLSs) and peripheral blood mononuclear cells (PBMCs) were obtained from a study population consisting of patients with active RA or peripheral SpA with at least one swollen joint (for obtaining synovial fluid) (n=14). SFMCs were cultured for 48 hours with and without addition of a MK2 inhibitor (Celgene) at 1000 nM, 333 nM and 111 nM and supernatants were analysed by the Olink proseek multiplex interferon panel and commercially available ELISA assays. Because FLSs are only found in small amounts among SFMCs, autologous co-cultures of FLS and PBMCs and SFMCs were also used. SFMCs cultured for 21 days were used to study inflammatory macrophage differentiation and osteoclastogenesis. Results In SFMCs cultured for 48 hours, the MK2 inhibitor decreased the production of CXCL9 (p Conclusions This study reveals the effects of a MK2 inhibitor in ex vivo models of immune mediated inflammatory arthritis. The MK2 inhibitor changed the secretory profile of SFMCs and decreased inflammatory osteoclastogenesis. Taken together, this points to a role of this MK2 inhibitor in attenuating inflammatory and destructive arthritis. Disclosure of Interest T. Kragstrup: None declared, A. Mellemkjaer: None declared, M. Nielsen: None declared, L. Heftdal: None declared, P. Schafer Shareholder of: Celgene, Employee of: Celgene, B. Deleuran: None declared

Background Apremilast (Otezla) is a phosphodiesterase 4 (PDE4) inhibitor approved for the treatment of psoriasis and psoriatic arthritis (PsA), but the reason why apremilast shows clinical effect in PsA is not fully understood. Objectives The objective of this study was to study the downstream effects of apremilast on cells of the inflamed joint in ex vivo models of immune mediated inflammatory arthritis. First, we tested the effect of apremilast on the secretion of several cytokines, chemokines and growth factors by synovial fluid mononuclear cells (SFMCs). Then, we tested whether apremilast affect factors involved in structural changes by studying fibroblast-like synovial cells (FLSs), osteoclasts, synovial macrophages, and osteoblasts. Methods Synovial fluid was obtained from a study population consisting of patients with active rheumatoid arthritis (RA), psoriatic arthritis (PsA) or peripheral spondyloarthritis (SpA) with at least one swollen joint (n=18). Synovial fluid mononuclear cells (SFMCs) cultured for 48 hours were used to study the effect of apremilast on secretion of a large panel of cytokines, chemokines and growth factors using the Olink Proseek Multiplex interferon I panel. These effects were compared with the effects of the tumour necrosis factor alpha (TNFα) inhibitor adalimumab. Further, fibroblast-like synovial cells (FLSs) were used to study metalloproteinase secretion, SFMCs cultured for 21 days were used to study inflammatory osteoclastogenesis and macrophage differentiation, an osteoclast pit formation assay was used to study osteoclast activity, and a mineralization assay was used to study new bone formation. Results In SFMCs cultured for 48 hours apremilast decreased the production of IL-12/IL-23p40 (the shared subunit of IL-12 and IL-23) (p Conclusions This study reveals the downstream effects of apremilast in ex vivo models of arthritis with a strong inhibition of IL-12/IL-23p40. Our findings could explain some of the efficacy of apremilast seen in IL-12/IL-23 driven immune mediated inflammatory diseases such as psoriasis and psoriatic arthritis. Disclosure of Interest T. Kragstrup: None declared, M. Adams: None declared, S. Lomholt: None declared, M. Nielsen: None declared, L. Heftdal: None declared, P. Schafer Shareholder of: Celgene, Employee of: Celgene, B. Deleuran: None declared

Spondyloarthritis (SpA) is characterized by inflammation and new bone formation and can be treated by inhibition of the proinflammatory cytokines TNF-α and IL-17A. IL-26 is considered a proinflammatory cytokine, predominantly related to Th17 cells. In the present study, we investigate IL-26 expression in SpA patients, and examine the in vitro production of IL-26 by synovial cells and the effects of IL-26 on human osteoblasts. IL-26 was measured by ELISA in plasma and synovial fluid (SF) of 15 SpA patients and in plasma samples from 12 healthy controls. Facet joints from axial SpA patients were stained for IL-26 and analyzed by fluorescence microscopy. Synovial fluid mononuclear cells, C-C motif chemokine receptor 6 memory Th17 cells, and fibroblast-like synoviocytes (FLSs) were isolated, and supernatants were analyzed for IL-26 content by ELISA. FLSs were further stained for IL-26 production and the myofibroblast marker α-smooth-muscle-actin (αSMA) and analyzed by flow cytometry. Human osteoblasts were cultured in the presence of IL-26, and the degree of mineralization was quantified. We found that IL-26 levels in SF were increased compared with plasma (P < 0.0001). Moreover, IL-26 expression was found in facet joints of axial SpA patients within the bone marrow. IL-26 secretion was primarily found in αSMA(+) myofibroblasts. In contrast, Th17 cells did not produce detectable amounts of IL-26. Human osteoblasts treated with IL-26 showed increased mineralization compared with untreated osteoblasts (P = 0.02). In conclusion, IL-26 seems to be produced by myofibroblasts in the inflamed synovium and could be a possible facilitator of bone mineralization in SpA.KEY MESSAGES: IL-26 levels are higher in synovial fluid compared to plasma in spondyloarthritis. IL-26 was identified in axial facet joints of spondyloarthritis patients. Myofibroblasts from the spondyloarthritis synovium produce large amounts of IL-26. IL-26 induces bone mineralization in human osteoblasts.

Rheumatoid arthritis (RA) is characterized by chronic joint inflammation and infiltration by activated macrophages. TNFα is a central mediator in this process. The mannose receptor, CD206, is a scavenger receptor expressed by M2A-macrophages and dendritic cells. It is involved in collagen internalization and degradation. The soluble form has been suggested as a biomarker of M2A-macrophage activation. The aim of this study was to investigate sCD206 plasma levels in early RA patients initiating anti-TNFα treatment. Plasma levels of sCD206 were measured by ELISA in samples from 155 early RA patients with an average symptom duration of 3 months. Patients were randomized to 12 months' methotrexate and placebo (PLA) or methotrexate and adalimumab (ADA) treatment, followed by open-label treatment with disease-modifying anti-rheumatic drugs (DMARD) and if needed, ADA. Disease activity was assessed at baseline and after 3, 6, 12 and 24 months. Baseline plasma level of sCD206 in treatment naïve RA patients was 0.33 mg/L (CI: 0.33-0.38 mg/L) corresponding to the upper part of the reference interval for healthy controls (0.10-0.43 mg/L). In the PLA group, sCD206 levels decreased after 3 months, but did not differ from baseline after 6 months. In the ADA group, however, levels remained lower than baseline throughout the treatment period. In conclusion, initially, plasma sCD206 in early RA patients decreased in accordance with disease activity and initiation of DMARD treatment. Treatment with anti-TNFα preserved this decrease throughout the study period.

Background: Many high-risk B- and T- lymphoid malignancies including Acute Lymphoblastic Leukemia (ALL) and lymphomas exhibit hyperactivation of the MYC oncogene and MYC-associated pathways. Experimentally, direct targeting of MYC in mouse models of MYCHigh lymphoid cancers sustains tumor regression. However, the requirement of MYC in normal lymphocyte physiology has impeded the development of MYC inhibitors. Hence, the development of targeted therapies against MYCHigh lymphoid cancers requires the identification of cell-intrinsic and cell-extrinsic (immune microenvironment) processes uniquely regulated by 'oncogenic' MYC (MYCHigh B/T-lymphoblasts) but not by 'normal' MYC (MYCLow B/T-lymphocytes). Approach: We employed an inducible transgenic mouse model of MYC-driven T-ALL (SRα-tTA/Tet-O-hMYC mice; Felsher and Bishop, Molecular Cell, 1999) to study leukemia-intrinsic, and leukemia-extrinsic immune surveillance mechanisms upon MYC activation (MYCHigh/ON, overt T-ALL), and MYC inactivation (MYCLow/OFF, regressed T-ALL). Inducible regulation of the human MYC (hMYC) transgene specifically in T-lymphoblasts enables us to elucidate how T-ALL-intrinsic MYC impacts normal immune cells during leukemogenesis in vivo. Using mass cytometry (CyTOF), and CIBERSORT to profile the immune microenvironment of MYCHigh/ON and MYCLow/OFF T-ALLs in SRα-tTA/Tet-O-hMYC mice, we identified specific anti- and pro-tumorigenic immune subsets that can be modulated to develop targeted immunotherapies against MYC-driven lymphoid cancers. Results: By conducting CyTOF-based immune profiling of lymphoid organs in healthy mice, and mice bearing MYCON or MYCOFF T-ALL, we demonstrated a significant reduction in numbers of Natural Killer (NK) cells, and an increase in the absolute counts of neutrophils and dendritic cells (DCs) in MYCON mice, in comparison to healthy controls and MYCOFF mice. The reduction in NK cell numbers in MYCON mice led us to hypothesize that the NK subset may play an anti-tumorigenic role in MYC-driven T-ALLs. Since anti-tumor immune subsets can be developed as therapies against MYC-driven lymphoid cancers, we decided to focus on how MYC impacts NK cell-mediated immune surveillance. We demonstrated that mature CD3-NKp46+ Natural Killer (NK) cells are specifically 'excluded' from the T-ALL microenvironment, in a MYC-dependent fashion. Residual NK cells in MYCON T-ALL-bearing mice exhibited suppression of the NK cell maturation/cytotoxicity marker, NKp46. Concordant with the suppression of NKp46 on NK cells in MYCON mice, we observed a blockade in early NK cell development from the NK precursor (NKP) to the immature NK (iNK) stage which is marked by the expression of NKp46. Next, we showed that adoptive transfer of mature CD3- NKp46+ syngeneic NK cells alone is sufficient to delay the initiation of MYCON T-ALL, and the recurrence of MYCOFF T-ALL. Further investigation into the molecular mechanism behind blockade of NK cell maturation in MYC-driven B/T-lymphoid cancers revealed that cancer-intrinsic MYC transcriptionally represses STAT1/2-Type I IFN signaling required for early NK cell maturation from NKP to iNK stage. We observed that treating T-ALL-bearing SRα-tTA/Tet-O-hMYC mice (MYCON)with Type I IFN improves survival by rescuing NK cell maturation. We showed that that low expression of both STAT1 and STAT2 in patients with MYCHigh B- and T-lymphoid neoplasms correlates significantly with the absence of activated NK cells, and predicts unfavorable clinical outcomes. Of note, aggressive MYCHigh B/T-lymphoid cancers are often treated with Type I IFNs, but the molecular mechanisms underlying the anti-cancer properties of Type I IFNs are not completely understood. We demonstrate for the first time that MYC-mediated suppression of NK surveillance may in part be responsible for the sensitivity of B/T-lymphoid cancers to Type I IFN therapy. Conclusion: We conclude that subversion of NK cell-mediated immune surveillance is critical for MYC-induced leukemogenesis. Our studies thus provide a rationale for developing targeted NK cell-based therapies as alternatives to direct MYC inhibition for treating refractory MYCHigh B- and T- lymphoid malignancies. Disclosures No relevant conflicts of interest to declare.

Background: The MYC oncogene drives T and B cell lymphoid malignancies, including Burkitt's lymphoma (BL) and Acute Lymphoblastic Leukemia (ALL). Such lymphomas are said to be "oncogene-addicted" to MYC. In order to develop targeted therapies for MYC-driven cancers, it is vital to understand how MYC regulates both cell autonomous and non-cell-autonomous processes, including host immunity. Approach: We have used a particularly tractable approach for studying the role of oncogenic MYC on the host immune system during lymphomagenesis through a tetracycline (tet)-system regulated transgenic mouse model of MYC-driven T cell lymphoma (SRα-tTA/Tet-O-MYC mice; Felsher and Bishop, Molecular Cell, 1999). By delineating the global immunological changes during primary MYC-driven T cell lymphomagenesis in SRα-tTA/Tet-O-MYC mice using mass cytometry (CyTOF) and CIBERSORT, we identified anti-tumor immune subsets that can be developed as therapies to treat MYC-driven lymphomas. Results: Amongst the immune subsets evaluated, our results demonstrated a specific systemic suppression of natural killer (NK) cell-mediated surveillance in SRα-tTA/Tet-O-MYC mice bearing overt MYC-driven T cell lymphomas. Inactivation of lymphoma-intrinsic MYC restores NK cell-mediated immune surveillance, suggesting that the regulation of NK cell-mediated surveillance may be integral to MYC-induced lymphomagenesis. We observed that lymphoma-specific MYC transcriptionally represses STAT1/2 and secretion of Type I Interferons (IFNs) required for normal NK cell homeostasis and NK cell-mediated immune surveillance in the tumor microenvironment. Concordantly, treating T cell lymphoma-bearing SRα-tTA/Tet-O-MYC mice with Type I IFN improves survival by rescuing NK cell production, and in part overriding MYC-mediated suppression of NK surveillance. We showed that human lymphomas with both high levels of MYC and low levels of STAT1/2 have lower NK surveillance, and are associated with poor prognosis. Finally, we established the therapeutic implications of our findings by showing that adoptive transfer of NK cells significantly delays lymphoma initiation, and recurrence after MYC inactivation; suggesting that NK cell-based therapy may be effective against MYC-driven lymphomas. Conclusion: Subversion of NK cell surveillance is integral to MYC-induced lymphomagenesis. Our studies provide a rationale for further developing the NK subset as a cell-based immunotherapy to effectively treat MYC-driven lymphomas in the future. Disclosures No relevant conflicts of interest to declare.

The MYC oncogene is commonly overexpressed in hematopoietic cancers. In a transgenic mouse model of MYC-induced T-cell lymphoma, we found that there was a systemic reduction in NK cell (CD3- NKp46High) numbers and activation in lymphoid organs such as spleen and bone marrow. MYC inactivation in lymphoma-bearing MYCON mice partially restored NK cell numbers and activation. Hence, the MYC oncogene appears to suppress NK cell-mediated immune surveillance of lymphomas. We evaluated whether reduction in mature and activated NK cells (CD3- NKp46High) in MYCON mice was due to increased death of NK cells in these mice when compared to normal and MYCOFF mice. Using flow cytometry, NK cells were measured in age matched spleens and bone marrows of normal (n = 8), MYCON (n = 8), and MYCOFF (n = 8) mice. Surprisingly, we observed a significant reduction in proportions of dead NK cells (NKp46+ PI+) in spleen and bone marrow of MYCON mice, in comparison to normal and MYCOFF cohorts. Hence, the reduction in activated NK cell numbers during MYC-driven lymphomagenesis does not occur because of increased death of NK cells. Next, we investigated whether MYC arrests early NK cell development in the bone marrow of lymphoma mice, leading to systemic NK suppression. NK cell lineage specification begins with CD122 expression, that is maintained throughout NK development starting at the precursor stage. NK precursors (NKP) transition to immature NK (iNK) cells by expressing the cytotoxicity marker NKp46. iNK cells leave the bone marrow to populate peripheral lymphoid organs. We measured NKP (CD122+ NKP46-), and iNK (CD122+ NKp46+) cells in bone marrow of normal (n = 8), MYCON (n = 8), and MYCOFF (n = 8) mice. We observed no significant changes in the percentages of NKP. However, the proportions of iNK cells were significantly reduced in MYCON mice, in comparison to MYCOFF and normal mice. Our results suggest that MYC may block transition from NKP to iNK stage during early NK cell development. The reduction of iNK cells in spleens of MYCON mice was concordant with the reduction of iNK cells in bone marrow from the same mice. We conclude that MYC-induced lymphomagenesis blocks early NK cell development, thereby suppressing NK-mediated immune surveillance. Citation Format: Line D. Heftdal, Srividya Swaminathan, Dean W. Felsher. MYC-driven lymphomas suppress NK surveillance by blocking maturation of early NK cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 126.

Background New bone formation in spondyloarthritis involves myofibroblasts [1]. IL-26 is part of the IL-10 cytokine family and was recently reported to increase Th17 differentiation [2]. It was first discovered in herpesvirus saimiri–transformed T cells and thus suspected to be a T-cell cytokine [3]. However, more recent studies of RA patients show IL-26 expression in synoviolin-postive cells harvested from the synovia [2]. The knowledge about IL-26 is compromised by lack of IL-26 in mice and no studies of IL-26 in spondyloarthritis (SpA) and its regulation have been conducted. Objectives In the present study we aim to characterize IL-26 producing cells in spondyloarthritis (SpA). Methods IL-26 was measured by ELISA in plasma and synovial fluid (SF) of 14 SpA patients attending the clinic with a swollen joint and in plasma samples from 7 age and gender matched healthy controls. Synovial-fluid-mononuclear-cells (SFMC) and fibroblast-like-synoviocytes (FLS) were cultured and stimulated for 48 hours with IL-1β, TNFα, TGF-β, IL-17A and LPS. The supernatants were harvested and analyzed for IL-26 by ELISA. Tissue samples of inflamed synovial membrane were stained with a fluorochrome conjugated rabbit IL-26 antibody for immunofluorescence. Imaging of the sections was performed by confocal microscopy. For flow cytometry analysis, FLS were surface stained for CD90 and a live-dead marker, and subsequently permeabilized and stained intracellularly for α-Smooth-Muscle-Actin (αSMA) and IL-26. Samples were run on the flow cytometer within 24 hours of staining. Data are expressed as mean ± SD. Results IL-26 levels were significantly higher in synovial fluid compared with plasma; this applied to plasma from the healthy controls (HC) as well as SpA patients. (HC plasma: 5.8 ± 3.3 pg/ml, SpA plasma: 6.6 ± 1.8 pg/ml, SpA SF: 41.6 ± 6.8 pg/ml - P-values HC vs. SF: 0.0020, P-value SP vs. SF: + and CD90 + myofibroblasts by flow cytometry. Conclusions IL-26 levels in synovial fluid are significantly higher than in plasma, suggesting a local production of IL-26 in the inflamed joint. We found IL-26 positive cells in the synovial membrane with fibroblast morphology and FLS from the inflamed joints of SpA patients produce high amounts of IL-26. By flow cytometry we established that these IL-26 producing fibroblasts seem to be myofibroblasts primarily. References Beyer C, et al: Changing paradigms in spondylarthritis: The myofibroblast signature. Arthritis Rheum. 2012;65:24–7 Corvaisier M, et al: IL-26 is overexpressed in rheumatoid arthritis and induces proinflammatory cytokine production and Th17 cell generation. PLoS Biol 2012;10:e1001395 Knappe A, et al: Induction of a novel cellular homolog of interleukin-10, AK155, by transformation of T lymphocytes with herpesvirus saimiri. J Vi- rol 2000;74:3881–3887 Disclosure of Interest None declared