Citations

Abstract Rationale Candida albicans (CA) is ubiquitous and individuals are often immunized against it. However, skin testing reactivity with CA-antigens (CAAg) have been variable during latent tuberculosis infection (LTBI) screening. We hypothesized that the use of a CAAg in an ELISPOT assay would provide a positive control to study tuberculosis (TB)-antigen specific immune responses. Objective To test an ELISPOT with TB-antigens and control conditions, including a purified protein derivative of CA, CAAg, that differentiates subjects with LTBI from unexposed subjects. Methods An ELISPOT that detects interferon-γ from PBMCs (2×105 cells) after 2-day incubation with TB antigens, controls, including CAAg, and co-stimulatory antibodies. We studied two independent cohorts of subjects with LTBI diagnosis based on TST and IGRA results per clinical guidelines. Results One-hundred thirty-nine subjects were studied in 2010–12, including 27 patients with LTBI and 21 IGRA(−) unexposed subjects. ELISPOT with TB-antigens but also CAAg - nil (78 [21 – 182] vs. 9 [1 – 50] cfu) differentiated LTBI subjects from unexposed ones (P<0.005). A second cohort of 76 subjects were studied in 2015–17, including 14 patients with LTBI and 24 unexposed controls, which showed similar statistical results. Positive control (SEAB/antiCD3) did not differentiate these study groups. ELISPOT results with CAAg correlated with results of ELISPOT with TB antigens in all subjects (P<0.001), and in the LTBI and unexposed groups independently. Conclusion An ELISPOT assay that includes CAAg revealed immune reactivity that is prevalent in LTBI. The immune subsets that react to both CA and mycobacterial antigens are unclear, but may be relevant for both TB and candida immunity.

Abstract Glioblastoma multiforme (GBM) is incurable and among the most lethal of cancers. Immunotherapy for GBM is hampered by the fact that GBM patients are severely immunosuppressed with dangerously low T cell counts. Importantly, immunotherapy for GBM will be ineffective without defining the mechanism of immunosuppression. Given that GBM does not metastasize, we investigated the possibility of neuro-immune interactions using the GL261 glioma model in C57BL/6 mice. C57BL/6 mice harboring GL261 gliomas have abnormal thymuses which are acutely and significantly involuted compared to healthy control mice. Glioma bearing mice also have significant thymic atrophy which increases with tumor burden. Further structural analysis of the thymus in glioma bearing mice revealed disrupted thymic epithelial cells and reduced EPCAM+ cell expression of MHC II. Thymic subsets in tumor bearing mice were also developmentally skewed with increased generation of single positive T cells and a block at double negative 2 (DN2) to DN3 transition. Peripherally, MHCII expression was also significantly decreased in blood derived cells in glioma bearing mice. This correlated with an overall reduction in total CD4 T cell numbers. The results of this study demonstrate the GL261 model is recapitulating the immune suppression observed in GBM patients. These results also support the presence of a brain-thymus interaction that could negatively impact the development of immunotherapy strategies to treat GBM.

Abstract Glioblastoma multiforme (GBM) is a deadly CNS malignancy with an average survival of ~12 months post diagnosis despite aggressive treatment. Immunotherapy approaches to treat GBM are being developed, but the unique immune environment of the brain and the immunosuppressive features of GBM have complicated early efforts. Even αPD-1 checkpoint blockade, highly useful in the context of melanoma, has proved ineffective in the treatment of GBM. In order to promote the efficacy of αPD-1 against the GL261 murine model of GBM, we supplemented this therapy with an engineered IL-2 cytokine. IL-2 therapy has been used clinically for metastatic melanoma and renal cancer, but its short half-life in circulation necessitated dangerously high doses to keep the drug concentration sufficiently high. Fusing IL-2 to the mouse serum albumin molecule (MSA-IL-2), extends the cytokine’s half-life. While neither αPD-1 nor MSA-IL-2 are effective monotherapies against the GL261 model tumor, we have found this combination immunotherapy to provide durable tumor clearance and to create immunologic memory capable of resisting GL261 rechallenge. Most strikingly, this combination therapy is independent of the CD8 T cell function, clearing established GL261 tumors in mice incapable of MHC class I restricted antigen presentation. Independence of MHC class I restricted antigen presentation makes this combination immunotherapy using αPD-1 checkpoint blockade both highly novel and translatable to clinical use.

Abstract Peripheral immune suppression is a hallmark of highly malignant Glioblastoma multiforme (GBM). Given that effective immunotherapy for GBM relies on a functional immune system, it is crucial to define the underlying mechanism of peripheral immunosuppression. We therefore evaluated immunosuppression using the GL261 model of GBM. We first examined cytokine production by microglia and brain-infiltrating lymphocytes for immune suppressing factors. We observed relatively unchanged levels of IL-10 and TGF-β in glioma bearing mice compared to controls. Therefore, we next investigated cellular components of the blood for evidence of suppression. However, we did not observe enhanced frequencies of Tregs (Foxp3+ CD4+) in tumor bearing mice. Finally, we analyzed cytokine levels in the serum of mice harboring gliomas compared to glioma negative animals. This assay revealed fluctuations in chemokine and cytokine levels between these two groups, prompting the analysis of a potential serum derived factor in promoting immunosuppression. We therefore evaluated T cell activation and proliferation in the presence of serum isolated from glioma harboring mice and healthy controls. CFSE-labeled T cells stimulated with CD3/CD28 beads in the presence of glioma negative mouse serum had normal proliferation. In contrast, CD4+ and CD8+ T cell proliferation was completely inhibited when cultured with serum from glioma bearing mice. These studies demonstrate the importance of a serum derived factor in mediating immunosuppression. Defining and inhibiting this circulating factor could be the first step towards improving immunotherapy strategies for GBM.

Abstract Blood brain barrier (BBB) disruption is a feature of multiple neurological disorders for which there is an increasingly recognized role for CD8+ T cells. Theiler’s murine encephalomyelitis virus (TMEV) infection serves as an excellent model to study CD8+ T cell mediated BBB disruption because of the well-characterized immune response to the immunodominant VP2121–130 peptide presented in the context of the H-2Db class I molecule. Intravenous injection of VP2121–130 peptide seven days post TMEV infection results in severe BBB disruption. BBB disruption is dependent on CD8+ T cell interaction with the Db: VP2121–130 epitope, but the antigen presenting cell required for BBB disruption is undefined. We hypothesized that dendritic cells are responsible for presentation of the immunodominant VP2121–130 peptide. We tested this hypothesis using a novel H-2Db Cre-LoxP conditional knockout mouse bred to MHC class I deficient CD11c-Cre expressing mice. We then evaluated these animals at 7 days post infection for induction of BBB disruption, following VP2121–130 peptide administration, using gadolinium enhanced MRI, fluorescent albumin leakage into the brain, and confocal microscopy for the tight junction protein occludin. Control CD11c-Cre(−) mice generated robust Db: VP2121–130 epitope specific CD8+ T cell responses and displayed extensive BBB disruption. In contrast, CD11c-Cre(+) littermates generated no brain infiltrating antiviral CD8+ T cell responses and were protected from BBB disruption. We conclude that CD11c+ dendritic cells are required for priming of CD8+ T cell responses and are necessary for BBB disruption during neuroinflammation in this model.

Abstract Microglia are central nervous system (CNS) resident immune cells for which the impact of MHC class I antigen presentation is still being defined. To directly address if microglia contribute to CD8 T cell-mediated immunity of the CNS, we generated a novel tamoxifen inducible CX3CR1-creER H-2Kb MHC class I conditional knockout mouse. In this transgenic mouse, the H-2Kb MHC class I molecule is deleted on all CX3CR1-expressing cells following tamoxifen treatment. By two weeks post tamoxifen treatment, peripheral CX3CR1-expressing cells repopulate, restoring normal expressing of H-2Kb. This leaves only microglia as the sole MHC class I-deficient cell type. We hypothesized that deletion of H-2Kb on microglia would reduce CD8 T cell responses in the CNS. We challenged these animals and cre-negative littermates with intracranial picornavirus infection with Theiler’s murine encephalomyelitis virus expressing ovalbumin (TMEV-OVA). We also challenged mice with experimental GL261 gliomas. We found that microglia-specific H-2Kb deletion reduces the CD8 T cell response in the CNS and attenuates the activation status of brain-infiltrating CD8 T cells in both models of neuroinflammation. We conclude that microglia are functional antigen presenting cells, and are required for a complete antigen-specific CD8 T cell response in the brain. These findings are the first to definitively address the role of microglia-expressed MHC class I in CNS immunological challenges.

Abstract HER2 is a prime target for cancer therapeutics due to its high overexpression in tumors. Advanced clinical trials, in breast and prostate cancer, investigating the use of the HLA-A2-binding HER2 peptide p369-377 (E75) as a vaccine are ongoing. In the present study, we investigated the proteasomal processing of p369-377 and other epitopes from HER2. We did not detect processing of p369-377 by either the proteasome or immunoproteasome in vitro, suggesting that tumor cells do not naturally process this epitope from HER2 for presentation on HLA-A2. However, other HER2 peptides were found to be consistently processed by the proteasome and immunoproteasome. One newly identified processed peptide, HER2 p373-382, was found to bind HLA-A2 stronger than p369-377, despite algorithms that predicted p369-377 as a stronger binder. Cytotoxic T lymphocytes (CTL) specific for p373-382 recognized target cells pulsed with either p373-382 or p369-377. CTL specific for p373-382 also lysed HER2+HLA-A2+ human breast cancer cells more efficiently than p369-377-specific CTL. These results suggest that cancer cells are naturally processing and presenting p373-382. Furthermore, our results suggest that T cells generated against p369-377 in previous studies may have been cross-reacting with p373-382. Thus, the newly identified p373-382 peptide may be a more appropriate candidate for vaccines with this new evidence that it is processed and presented by HLA-A2 for recognition by HER2-specific CTL.

AbstractBackgroundCyclin E1 (CCNE1) is a potential predictive marker and therapeutic target in tubo‐ovarian high‐grade serous carcinoma (HGSC). Smaller studies have revealed unfavorable associations for CCNE1 amplification and CCNE1 overexpression with survival, but to date no large‐scale, histotype‐specific validation has been performed. The hypothesis was that high‐level amplification of CCNE1 and CCNE1 overexpression, as well as a combination of the two, are linked to shorter overall survival in HGSC.MethodsWithin the Ovarian Tumor Tissue Analysis consortium, amplification status and protein level in 3029 HGSC cases and mRNA expression in 2419 samples were investigated.ResultsHigh‐level amplification (>8 copies by chromogenic in situ hybridization) was found in 8.6% of HGSC and overexpression (>60% with at least 5% demonstrating strong intensity by immunohistochemistry) was found in 22.4%. CCNE1 high‐level amplification and overexpression both were linked to shorter overall survival in multivariate survival analysis adjusted for age and stage, with hazard stratification by study (hazard ratio [HR], 1.26; 95% CI, 1.08‐1.47, p = .034, and HR, 1.18; 95% CI, 1.05‐1.32, p = .015, respectively). This was also true for cases with combined high‐level amplification/overexpression (HR, 1.26; 95% CI, 1.09‐1.47, p = .033). CCNE1 mRNA expression was not associated with overall survival (HR, 1.00 per 1‐SD increase; 95% CI, 0.94‐1.06; p = .58). CCNE1 high‐level amplification is mutually exclusive with the presence of germline BRCA1/2 pathogenic variants and shows an inverse association to RB1 loss.ConclusionThis study provides large‐scale validation that CCNE1 high‐level amplification is associated with shorter survival, supporting its utility as a prognostic biomarker in HGSC.

Background: Prior studies have reported conflicting results of persistent iatrogenic atrial septal defect (iASD) and its impact following a transcatheter edge-to-edge repair (TEER) procedure. This study aims to evaluate the incidence of iASD and its clinical and hemodynamic impact after a TEER. Methods: Consecutive patients who underwent a TEER procedure from June 2014 to September 2020 at the Mayo Clinic were identified. The presence of iASD was retrospectively identified on post-procedure transthoracic echocardiography (TTE) to group patients into an iASD+ group and an iASD− group for comparison of prognosis and cardiac function. Results: A total of 316 patients were included; the mean age was 79.1 ± 9.1 years, and 67.7% were male. Persistent iASD was diagnosed in 108 (34.2%) patients. There was no difference concerning all-cause mortality, heart failure hospitalization, and stroke/TIA between groups at follow-up (median follow-up of 9 months). Post-procedure TTE demonstrated no differences regarding right ventricle (RV) and left ventricle (LV) dimensions and function, including TAPSE (15.2 ± 4.6 vs. 15.4 ± 5.5 mm, p = 0.875), and LV ejection fraction (51.1 ± 14.0% vs. 51.3 ± 13.9%, p = 0.933). However, patients with iASD had higher RV systolic pressure (48.7 ± 14.4 vs. 45.5 ± 14.5 mmHg, p = 0.042) compared with patients without iASD. Conclusion: Notwithstanding higher RV pressures, patients with persistent iASD had no hemodynamic compromise and an equal prognosis compared with those without a residual atrial defect after a TEER procedure. These findings support the mid-term safety of procedures in which an interatrial defect needs to be created and would argue against the need for interventional closure.

Abstract Background Isavuconazole (ISA) is a relatively recent triazole antifungal with several attractive qualities and so increased clinical experience and data on the use of ISA are desirable. However, the data on the pattern of ISA use in invasive fungal infections (IFI) is limited. Methods We conducted a retrospective study of patients with probable or proven IFI treated with ISA at Mayo Clinic from 1/1/2015 to 4/1/2020 to examine temporal trends and characteristics of ISA use. Results The use of ISA rose over this period, from 4 cases in 2015 to 42 cases in 2019. Of 131 patients identified, ISA was used as the initial antifungal in 15 (11.5%) patients and as the secondary agent in 116 (88.5%) patients. The most cited reasons for choosing ISA as first-line therapy were drug-drug interactions (5, 33%) and baseline QTc prolongation (3, 20%). In cases of ISA used as a secondary agent, the reasons for transitioning to ISA were QTc prolongation (22, 19%), followed by judged failure of the primary therapy (20, 17%), drug-drug interactions (12, 10%), and various toxicities with the first agent. ISA was discontinued early in 81 (62%) patients. Common reasons for early discontinuation were patient death or comfort care (27, 33%), intolerance (18, 22%), failure of therapy (17, 21%), cost or access (6, 7%), drug-drug interaction (3, 4%), issues with absorption or drug delivery (3, 4%), and microbe susceptibility (1, 1%). ISA was judged successful and used as definitive treatment in the remaining 50 (38%) patients. About 30 patients took >1 year of ISA, and no major adverse effects from long-term therapy were noted. Conclusion Although ISA is approved for pulmonary aspergillosis and mucormycosis, we found that few patients were treated with ISA as either primary or salvage therapy. In cases where it was used, shortening the QTc and fewer drug-drug interactions were its most attractive qualities. Although it is a newer azole, the morbidity common with other antifungals should prompt more studies on ISA’s efficacy to increase clinicians’ confidence in this option. Disclosures All Authors: No reported disclosures.