IL-10-Dependent Crosstalk between Murine Marginal Zone B Cells, Macrophages, and CD8α+ Dendritic Cells Promotes Listeria monocytogenes Infection.

Type 1 CD8α+ conventional dendritic cells (cDC1s) are required for CD8+ T cell priming but, paradoxically, promote splenic Listeria monocytogenes infection. Using mice with impaired cDC2 function, we ruled out a role for cDC2s in this process and instead discovered an interleukin-10 (IL-10)-dependent cellular crosstalk in the marginal zone (MZ) that promoted bacterial infection. Mice lacking the guanine nucleotide exchange factor DOCK8 or CD19 lost IL-10-producing MZ B cells and were resistant to Listeria. IL-10 increased intracellular Listeria in cDC1s indirectly by reducing inducible nitric oxide synthase expression early after infection and increasing intracellular Listeria in MZ metallophilic macrophages (MMMs). These MMMs trans-infected cDC1s, which, in turn, transported Listeria into the white pulp to prime CD8+ T cells. However, this also facilitated bacterial expansion. Therefore, IL-10-mediated crosstalk between B cells, macrophages, and cDC1s in the MZ promotes both Listeria infection and CD8+ T cell activation.

Characterization of circulating and cultured Tfh-like cells in sickle cell disease in relation to red blood cell alloimmunization status.

BACKGROUND: People living with sickle cell disease (SCD) are prone to red blood cell (RBC) alloimmunization. We hypothesized that subjects with alloantibodies (responders) would have differences in circulating T-follicular helper (Tfh)-like cells compared to subjects without alloantibodies (non-responders). MATERIALS AND METHODS: Peripheral blood mononuclear cells were collected from 28 subjects, including those with SCD and controls. Circulating CD4 T-cell subsets were first evaluated at baseline. CD4 T-cell subsets were also evaluated after naïve CD4 T-cells were differentiated into Tfh-like cells following in vitro culture with CD3/CD28 beads, IL-7, IL-12, and Activin A. Transfusion and alloantibody histories were extracted from the electronic medical record. RESULTS: Non-responders had a lower percentage of CD45RA negative Tmemory cells than responders or controls (p<0.05). Notably, there were no differences in circulating Tfh-like cells between any group. However, naïve CD4 T-cells from subjects with SCD were more likely to express CXCR5 after in vitro culture than cells from controls. After culture, CXCR5 expressing cells from responders were more likely to express PD1 and ICOS (16.43 %, sd. 20.23) compared to non-responders (3.69 %, s.d. 3.09) or controls (2.78 %, s.d. 2.04). DISCUSSION: The tendency for naïve CD4 T-cells from responders to differentiate into Tfh-like cells after in vitro culture may suggest these cells are prepared to assist B-cells with antibody production regardless of antigen specificity. Further studies are needed, but it is possible that these results may explain why some responders form RBC alloantibodies with multiple specificities, in addition to RBC autoantibodies and HLA alloantibodies.

Red blood cell alloimmunization is associated with lower expression of FcγR1 on monocyte subsets in patients with sickle cell disease.

BACKGROUND: Despite the clinical significance of red blood cell (RBC) alloantibodies, there are currently no laboratory tests available to predict which patients may be at risk of antibody formation after transfusion exposure. Given their phagocytic and inflammatory functions, we hypothesized that differences in circulating monocytes may play a role in alloimmunization. STUDY DESIGN AND METHODS: Forty-two adults with sickle cell disease (SCD) were recruited, with data extracted from the electronic medical record and peripheral blood analyzed by flow cytometry for total monocytes, monocyte subsets (CD14 high/CD16 low+ classical monocytes, CD14 high/CD16 high+ intermediate monocytes, and CD14 intermediate/CD16 high+ non-classical/inflammatory monocytes), and FcγR1 (CD64) expression. Thirteen "non-responder" patients (non-alloimmunized patients with documented RBC transfusion at the study institution) were compared to 20 alloimmunized "responder" patients, who had a total of 44 RBC alloantibodies identified. RESULTS: There were no significant differences in the percentages of total monocytes, monocyte subsets, or measured cytokines between non-responders and responders. However, non-responders had higher CD64 expression on classical monocytes (MFI mean 3424 ± standard deviation 1141) compared to responders (MFI mean 2285 ± 1501), p = 0.029, and on intermediate monocytes (MFI mean 3720 ± 1191) compared to responders (MFI mean 2497 ± 1640), p = 0.033. CONCLUSIONS: Monocytes and the inflammatory milieu increasingly are being appreciated to play a role in some complications of SCD. The differences in FcγR1 expression on monocyte subsets noted between responders and non-responders, which cannot be directly explained by the serum cytokines evaluated, warrant further investigation.

Changes in T-cell subsets identify responders to FcR-nonbinding anti-CD3 mAb (teplizumab) in patients with type 1 diabetes.

The mechanisms whereby immune therapies affect progression of type 1 diabetes (T1D) are not well understood. Teplizumab, an FcR nonbinding anti-CD3 mAb, has shown efficacy in multiple randomized clinical trials. We previously reported an increase in the frequency of circulating CD8(+) central memory (CD8CM) T cells in clinical responders, but the generalizability of this finding and the molecular effects of teplizumab on these T cells have not been evaluated. We analyzed data from two randomized clinical studies of teplizumab in patients with new- and recent-onset T1D. At the conclusion of therapy, clinical responders showed a significant reduction in circulating CD4(+) effector memory T cells. Afterward, there was an increase in the frequency and absolute number of CD8CM T cells. In vitro, teplizumab expanded CD8CM T cells by proliferation and conversion of non-CM T cells. Nanostring analysis of gene expression of CD8CM T cells from responders and nonresponders versus placebo-treated control subjects identified decreases in expression of genes associated with immune activation and increases in expression of genes associated with T-cell differentiation and regulation. We conclude that CD8CM T cells with decreased activation and regulatory gene expression are associated with clinical responses to teplizumab in patients with T1D.

Prolonged proinflammatory cytokine production in monocytes modulated by interleukin 10 after influenza vaccination in older adults.

We evaluated in vivo innate immune responses in monocyte populations from 67 young (aged 21-30 years) and older (aged ≥65 years) adults before and after influenza vaccination. CD14(+)CD16(+) inflammatory monocytes were induced after vaccination in both young and older adults. In classical CD14(+)CD16(-) and inflammatory monocytes, production of tumor necrosis factor α and interleukin 6, as measured by intracellular staining, was strongly induced after vaccination. Cytokine production was strongly associated with influenza vaccine antibody response; the highest levels were found as late as day 28 after vaccination in young subjects and were substantially diminished in older subjects. Notably, levels of the anti-inflammatory cytokine interleukin 10 (IL-10) were markedly elevated in monocytes from older subjects before and after vaccination. In purified monocytes, we found age-associated elevation in phosphorylated signal transducer and activator of transcription-3, and decreased serine 359 phosphorylation of the negative IL-10 regulator dual-specificity phosphatase 1. These findings for the first time implicate dysregulated IL-10 production in impaired vaccine responses in older adults.

Bupropion pre-treatment of endotoxin-induced depressive symptoms.

Increased levels of inflammatory cytokines may play a role in depression. Depressive symptoms can be induced in humans with administration of low-dose lipopolysaccharide (LPS; endotoxin), which activates the innate immune system and causes release of inflammatory cytokines. We previously found that pre-treatment with the serotonin reuptake inhibitor citalopram reduced LPS-induced fatigue and anhedonia. This is a follow-up study to determine whether LPS-induced symptoms could be reduced by pre-treatment with bupropion, a norepinephrine and dopamine reuptake inhibitor. In this double-blind, randomized, placebo-controlled, cross-over study, 10 healthy subjects received intravenous LPS (0.8 ng/kg) after oral pre-treatment with bupropion (75 mg twice a day) or placebo for 7 days. The Montgomery-Åsberg Depression Rating Scale (MADRS), the Profile of Mood States (POMS), and a visual analog scale (VAS) were used to measure depressive symptoms. Serum levels of inflammatory cytokines and chemokines were measured with electrochemiluminescence assays. The results of this study, which must be considered preliminary, showed that LPS administration was associated with (1) increase in serum levels of all cytokines and chemokines assayed; (2) increase in total MADRS score, mostly due to items 7 (lassitude) and 8 (anhedonia); (3) increase in fatigue; (4) decrease in vigor; and (5) decrease in social interest. Bupropion pre-treatment had no statistically significant effect on the innate immune response to LPS or on LPS-induced behavioral changes, suggesting that 1-week pre-treatment with bupropion does not inhibit LPS-induced fatigue and anhedonia, contrary to what was found previously with citalopram.

Tissue-engineered vascular grafts transform into mature blood vessels via an inflammation-mediated process of vascular remodeling.

Biodegradable scaffolds seeded with bone marrow mononuclear cells (BMCs) are the earliest tissue-engineered vascular grafts (TEVGs) to be used clinically. These TEVGs transform into living blood vessels in vivo, with an endothelial cell (EC) lining invested by smooth muscle cells (SMCs); however, the process by which this occurs is unclear. To test if the seeded BMCs differentiate into the mature vascular cells of the neovessel, we implanted an immunodeficient mouse recipient with human BMC (hBMC)-seeded scaffolds. As in humans, TEVGs implanted in a mouse host as venous interposition grafts gradually transformed into living blood vessels over a 6-month time course. Seeded hBMCs, however, were no longer detectable within a few days of implantation. Instead, scaffolds were initially repopulated by mouse monocytes and subsequently repopulated by mouse SMCs and ECs. Seeded BMCs secreted significant amounts of monocyte chemoattractant protein-1 and increased early monocyte recruitment. These findings suggest TEVGs transform into functional neovessels via an inflammatory process of vascular remodeling.

Quantitative DNA Repair Biomarkers and Immune Profiling for Temozolomide and Olaparib in Metastatic Colorectal Cancer.

Purpose: O6-methylguanine DNA methyltransferase (MGMT)-silenced tumors reveal sensitivity to temozolomide (TMZ), which may be enhanced by PARP inhibitors. Approximately 40% of colorectal cancer has MGMT silencing and we aimed to measure antitumoral and immunomodulatory effects from TMZ and olaparib in colorectal cancer. Experimental Design: Patients with advanced colorectal cancer were screened for MGMT promoter hypermethylation using methylation-specific PCR of archival tumor. Eligible patients received TMZ 75 mg/m2 days 1-7 with olaparib 150 mg twice daily every 21 days. Pretreatment tumor biopsies were collected for whole-exome sequencing (WES), and multiplex quantitative immunofluorescence (QIF) of MGMT protein expression and immune markers. Results: MGMT promoter hypermethylation was detected in 18/51 (35%) patients, 9 received study treatment with no objective responses, 5/9 had stable disease (SD) and 4/9 had progressive disease as best response. Three patients had clinical benefit: carcinoembryonic antigen reduction, radiographic tumor regression, and prolonged SD. MGMT expression by multiplex QIF revealed prominent tumor MGMT protein from 6/9 patients without benefit, while MGMT protein was lower in 3/9 with benefit. Moreover, benefitting patients had higher baseline CD8+ tumor-infiltrating lymphocytes. WES revealed 8/9 patients with MAP kinase variants (7 KRAS and 1 ERBB2). Flow cytometry identified peripheral expansion of effector T cells. Conclusions: Our results indicate discordance between MGMT promoter hypermethylation and MGMT protein expression. Antitumor activity seen in patients with low MGMT protein expression, supports MGMT protein as a predictor of alkylator sensitivity. Increased CD8+ TILs and peripheral activated T cells, suggest a role for immunostimulatory combinations. Significance: TMZ and PARP inhibitors synergize in vitro and in vivo in tumors with MGMT silencing. Up to 40% of colorectal cancer is MGMT promoter hypermethylated, and we investigated whether TMZ and olaparib are effective in this population. We also measured MGMT by QIF and observed efficacy only in patients with low MGMT, suggesting quantitative MGMT biomarkers more accurately predict benefit to alkylator combinations.

Determining the fate of seeded cells in venous tissue-engineered vascular grafts using serial MRI.

A major limitation of tissue engineering research is the lack of noninvasive monitoring techniques for observations of dynamic changes in single tissue-engineered constructs. We use cellular magnetic resonance imaging (MRI) to track the fate of cells seeded onto functional tissue-engineered vascular grafts (TEVGs) through serial imaging. After in vitro optimization, murine macrophages were labeled with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles and seeded onto scaffolds that were surgically implanted as inferior vena cava interposition grafts in SCID/bg mice. Serial MRI showed the transverse relaxation times (T(2)) were significantly lower immediately following implantation of USPIO-labeled scaffolds (T(2) = 44 ± 6.8 vs. 71 ± 10.2 ms) but increased rapidly at 2 h to values identical to control implants seeded with unlabeled macrophages (T(2) = 63 ± 12 vs. 63 ± 14 ms). This strongly indicates the rapid loss of seeded cells from the scaffolds, a finding verified using Prussian blue staining for iron containing macrophages on explanted TEVGs. Our results support a novel paradigm where seeded cells are rapidly lost from implanted scaffolds instead of developing into cells of the neovessel, as traditionally thought. Our findings confirm and validate this paradigm shift while demonstrating the first successful application of noninvasive MRI for serial study of cellular-level processes in tissue engineering.

Metabolomic and transcriptomic signatures of influenza vaccine response in healthy young and older adults.

Seasonal influenza causes mild to severe respiratory infections and significant morbidity, especially in older adults. Transcriptomic analysis in populations across multiple flu seasons has provided insights into the molecular determinants of vaccine response. Still, the metabolic changes that underlie the immune response to influenza vaccination remain poorly characterized. We performed untargeted metabolomics to analyze plasma metabolites in a cohort of younger and older subjects before and after influenza vaccination to identify vaccine-induced molecular signatures. Metabolomic and transcriptomic data were combined to define networks of gene and metabolic signatures indicative of high and low antibody response in these individuals. We observed age-related differences in metabolic baselines and signatures of antibody response to influenza vaccination and the abundance of α-linolenic and linoleic acids, sterol esters, fatty-acylcarnitines, and triacylglycerol metabolism. We identified a metabolomic signature associated with age-dependent vaccine response, finding increased tryptophan and decreased polyunsaturated fatty acids (PUFAs) in young high responders (HRs), while fatty acid synthesis and cholesteryl esters accumulated in older HRs. Integrated metabolomic and transcriptomic analysis shows that depletion of PUFAs, which are building blocks for prostaglandins and other lipid immunomodulators, in young HR subjects at Day 28 is related to a robust immune response to influenza vaccination. Increased glycerophospholipid levels were associated with an inflammatory response in older HRs to flu vaccination. This multi-omics approach uncovered age-related molecular markers associated with influenza vaccine response and provides insight into vaccine-induced metabolic responses that may help guide development of more effective influenza vaccines.

Acute alcohol consumption alters the peripheral cytokines IL-8 and TNF-α.

BACKGROUND: Acute alcohol consumption triggers release of cytokines, which are immune signaling molecules. Dysregulated cytokine levels are associated with impaired immune function, and peripheral cytokine levels may communicate with the brain to propagate drinking-related behaviors. This exploratory study aims to characterize the peripheral cytokine response to an alcohol challenge in a well-controlled laboratory setting. METHODS: Moderate alcohol drinkers (n = 17), abstinent for >5 days, consumed alcohol calibrated to achieve blood concentrations of 120 mg/dL. Serum cytokine levels (IL-6, IL-8, IL-12, IFN-γ, TNF-α) were measured prior to drinking, 6 h after drinking, and 24 h after drinking. Linear mixed models evaluated within-subject differences in cytokine levels over time. RESULTS: The pro-inflammatory chemokine IL-8 significantly increased 6 h after alcohol [F(1,34) = 4.13, p = 0.0002, d' = 0.5]. In contrast, the pro-inflammatory cytokine TNF-α significantly decreased 6 h after alcohol [F(1,34) = -3.07, p = 0.004, d' = 0.3]. No cytokines were significantly different from baseline 24 h after alcohol. CONCLUSIONS: In our exploratory data, acute alcohol challenge (120 mg/dL) elicits dynamic changes in the pro-inflammatory molecules IL-8 and TNF-α. The findings help inform the temporal profile of cytokine response to alcohol, and identify IL-8 as a cytokine of interest for future studies of periphery-brain immune communication.

Daily Cannabis Users with Sickle Cell Disease Show Fewer Admissions than Others with Similar Pain Complaints.

Introduction: Previous studies have shown that cannabis use is common in adults with sickle cell disease (SCD), and that many patients report using cannabis to treat pain. Methods: We performed a cross-sectional study of adults with SCD and compared daily users of cannabis with others using validated patient-reported measures of pain and quality of life as well as opioid and health care utilization. Results: Daily cannabis users with SCD had worse pain episode severity scores than others (56.7 vs. 48.8, p=0.02) yet had 1.8 fewer annual admissions (p=0.01) and 1.2 fewer annual emergency room (ER) visits (p=0.01), and similar amounts of opioids dispensed to others after matching for age, gender, SCD genotype, hydroxyurea use, and pain impact scores. Conclusions: We show that people with SCD with more severe pain crisis are more likely to use daily cannabis, yet have lower rates of hospital admission and ER use as compared with others with similar disease severity and pain impact. Randomized controlled trials should be performed.

Targeting neuroinflammation with minocycline in heavy drinkers.

RATIONALE: Alcohol has both acute and chronic effects on neuroimmune signaling, including triggering pro-inflammatory cytokine release by microglia. Minocycline, a second-generation tetracycline antibiotic, inhibits microglial activation and reduces neuroinflammation in preclinical studies. In mice, minocycline also reduces ethanol intake, attenuates ethanol-induced conditioned place preference, and inhibits ethanol-induced microglial activation and pro-inflammatory cytokine release. OBJECTIVE: Here, for the first time, we tested the effects of minocycline on subjective response to ethanol and acute ethanol-induced inflammation in humans. METHODS: Forty-eight heavy drinkers participated in a double-blind, placebo-controlled trial in which they were randomized to receive placebo, 100 mg, or 200 mg of minocycline for 10 days. Each subject then underwent two experimental sessions in which they were given a fixed dose of intravenous ethanol using a "clamp" procedure (100 mg%) or placebo (normal saline) on days 8 and 10 of treatment. RESULTS: Minocycline was well tolerated, but there was no effect of either dose of minocycline on subjective response to ethanol or ethanol-induced craving; minocycline effects on cognitive function seem to interact with age. Minocycline treatment did not alter serum cytokine levels at baseline or during ethanol-exposure, although certain baseline cytokine levels predict sedative response to ethanol. CONCLUSION: These findings indicate that a short-term treatment with minocycline may not alter ethanol-related inflammation or subjective response to ethanol in humans. Further research is needed to identify pharmacological agents with robust effects on ethanol-induced inflammation to determine whether neuroimmune modulation represents a viable treatment strategy for alcohol use disorder.

Phase I study of safety and tolerability of sunitinib in combination with sirolimus in patients with refractory solid malignancies and determination of VEGF (VEGF-A) and soluble VEGF-R2 (sVEGFR2) in plasma.

PURPOSE: Sirolimus, an oral mTOR inhibitor, may complement the anti-angiogenic and anti-tumor activity of sunitinib, an oral small molecule inhibitor of multiple receptor tyrosine kinases, by vertical disruption of vascular epithelial growth factor receptor (VEGFR) signaling, by reducing the compensatory production of VEGF in sunitinib-treated patients and also by directly inhibiting tumor cell proliferation. We conducted this phase 1 study to investigate the maximum tolerated dose (MTD) for this combination of sunitinib and sirolimus in humans. PATIENTS AND METHODS: Sunitinib was given at 50 mg daily × 28 every 6 weeks. The first cohort received sunitinib alone for cycle 1 (50 mg daily for 2 weeks followed by 2 weeks off) and received sunitinib at standard dose 50 mg daily for 4 weeks followed by 2 weeks off in combination with sirolimus 4 mg weekly; this dose and schedule were further investigated in second cohort. The third cohort received decreased dose of sunitinib at 37.5 mg daily for 4 weeks followed by 2 weeks off in combination with sirolimus at 4 mg weekly. Sirolimus dose was escalated to 8 mg weekly in fourth cohort. RESULTS: Eighteen patients with ECOG PS of 0 or 1 were enrolled, median age 57 years (range 24-76), M:F ratio: 11:7. Median number of prior treatments is 2 (range 0-5); six patients had no prior systemic therapy. Half of patients from the first two cohorts required dose reduction or early discontinuation of treatment; therefore, sunitinib dose was decreased to 37.5 mg daily in third and fourth cohort. In third and fourth cohort, one-third of patients required dose modification during cycle 1 or cycle 2. Multiple patients had significant toxicities including fatigue and hand-foot syndrome. One patient developed interstitial pneumonitis, and one patient died suddenly on day 8 due to progressive disease. There were six patients who tolerated four or more cycles. Among these six patients, two patients with renal cell carcinoma (RCC) achieved partial response; one subsequently underwent surgical resection of residual renal mass and lymph node dissection and achieved complete response afterward. One with metastatic melanoma also achieved complete response after metastatectomy. There was no apparent pharmacokinetic interaction between sunitinib and sirolimus. 4 mg weekly sirolimus did not reduce the sunitinib-induced circulating VEGF production but stimulated more VEGF production through some unknown compensatory mechanism. CONCLUSION: Toxicity precluded dose escalation of weekly sirolimus in combination with a standard sunitinib dose/schedule. These results suggest caution when combining targeted agents lacking specificity for tumor signaling or vasculature.

Standardizing Flow Cytometry Immunophenotyping Analysis from the Human ImmunoPhenotyping Consortium.

Standardization of immunophenotyping requires careful attention to reagents, sample handling, instrument setup, and data analysis, and is essential for successful cross-study and cross-center comparison of data. Experts developed five standardized, eight-color panels for identification of major immune cell subsets in peripheral blood. These were produced as pre-configured, lyophilized, reagents in 96-well plates. We present the results of a coordinated analysis of samples across nine laboratories using these panels with standardized operating procedures (SOPs). Manual gating was performed by each site and by a central site. Automated gating algorithms were developed and tested by the FlowCAP consortium. Centralized manual gating can reduce cross-center variability, and we sought to determine whether automated methods could streamline and standardize the analysis. Within-site variability was low in all experiments, but cross-site variability was lower when central analysis was performed in comparison with site-specific analysis. It was also lower for clearly defined cell subsets than those based on dim markers and for rare populations. Automated gating was able to match the performance of central manual analysis for all tested panels, exhibiting little to no bias and comparable variability. Standardized staining, data collection, and automated gating can increase power, reduce variability, and streamline analysis for immunophenotyping.

Systems immunology reveals markers of susceptibility to West Nile virus infection.

West Nile virus (WNV) infection is usually asymptomatic but can cause severe neurological disease and death, particularly in older patients, and how individual variations in immunity contribute to disease severity is not yet defined. Animal studies identified a role for several immunity-related genes that determine the severity of infection. We have integrated systems-level transcriptional and functional data sets from stratified cohorts of subjects with a history of WNV infection to define whether these markers can distinguish susceptibility in a human population. Transcriptional profiles combined with immunophenotyping of primary cells identified a predictive signature of susceptibility that was detectable years after acute infection (67% accuracy), with the most prominent alteration being decreased IL1B induction following ex vivo infection of macrophages with WNV. Deconvolution analysis also determined a significant role for CXCL10 expression in myeloid dendritic cells. This systems analysis identified markers of pathogenic mechanisms and offers insights into potential therapeutic strategies.

Genomic landscape of cutaneous T cell lymphoma.

Cutaneous T cell lymphoma (CTCL) is a non-Hodgkin lymphoma of skin-homing T lymphocytes. We performed exome and whole-genome DNA sequencing and RNA sequencing on purified CTCL and matched normal cells. The results implicate mutations in 17 genes in CTCL pathogenesis, including genes involved in T cell activation and apoptosis, NF-κB signaling, chromatin remodeling and DNA damage response. CTCL is distinctive in that somatic copy number variants (SCNVs) comprise 92% of all driver mutations (mean of 11.8 pathogenic SCNVs versus 1.0 somatic single-nucleotide variant per CTCL). These findings have implications for new therapeutics.

Location of the epitope for an anti-CD8alpha antibody 53.6.7 which enhances CD8alpha-MHC class I interaction indicates antibody stabilization of a higher affinity CD8 conformation.

MHC class I tetramers are widely used, usually in combination with an antibody to CD8, to detect antigen specific T cells. Some anti-CD8alpha antibodies block the interaction of murine MHC class I tetramers with CD8 T cells, while others such as 53.6.7, enhance. To understand the molecular basis for this effect, we mapped the epitope for the enhancing antibody 53.6.7 and three other blocking antibodies using a panel of murine CD8alpha (Lyt-2) mutants expressed on COS-7 transfectants. Mutations in residues that contact MHC class I affected binding of the blocking antibodies. In contrast, antibody 53.6.7 was affected by a mutation in the residue T81A located on the D-E loop. In the cocrystal of CD8alphaalpha with MHC class I, two different complexes (A and B) were observed, indicating the existence of different CD8 conformations. The T81 residue does not make contact with MHC class I in either complex, however, neighboring residues in the D-E loop make very different contacts in the two different complexes. The most likely explanation for antibody enhancement of tetramer bindings is that binding of 53.6.7 to CD8alphabeta stabilizes a conformation with a higher affinity for interaction with MHC class I and suggests that the CD8 binding site is flexible.

The immune cell infiltrate populating meningiomas is composed of mature, antigen-experienced T and B cells.

BACKGROUND: Meningiomas often harbor an immune cell infiltrate that can include substantial numbers of T and B cells. However, their phenotype and characteristics remain undefined. To gain a deeper understanding of the T and B cell repertoire in this tumor, we characterized the immune infiltrate of 28 resected meningiomas representing all grades. METHODS: Immunohistochemistry was used to grossly characterize and enumerate infiltrating lymphocytes. A molecular analysis of the immunoglobulin variable region of tumor-infiltrating B cells was used to characterize their antigen experience. Flow cytometry of fresh tissue homogenate and paired peripheral blood lymphocytes was used to identify T cell phenotypes and characterize the T cell repertoire. RESULTS: A conspicuous B and T cell infiltrate, primarily clustered in perivascular spaces, was present in the microenvironment of most tumors examined. Characterization of 294 tumor-infiltrating B cells revealed clear evidence of antigen experience, in that the cardinal features of an antigen-driven B cell response were present. Meningiomas harbored populations of antigen-experienced CD4+ and CD8+ memory/effector T cells, regulatory T cells, and T cells expressing the immune checkpoint molecules PD-1 and Tim-3, indicative of exhaustion. All of these phenotypes were considerably enriched relative to their frequency in the circulation. The T cell repertoire in the tumor microenvironment included populations that were not reflected in paired peripheral blood. CONCLUSION: The tumor microenvironment of meningiomas often includes postgerminal center B cell populations. These tumors invariably include a selected, antigen-experienced, effector T cell population enriched by those that express markers of an exhausted phenotype.

Enhanced stimulation of anti-ovarian cancer CD8(+) T cells by dendritic cells loaded with nanoparticle encapsulated tumor antigen.

PROBLEM: Dendritic cell (DC)-based cancer therapies are favored approaches to stimulate anti-tumor T-cell responses. Unfortunately, tolerance to tumor antigens is difficult to overcome. Biodegradable poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NP) are effective reagents in the delivery of drugs and tumor-associated antigens (TAA). In this study, we assessed the capacity of a PLGA NP-based delivery system to augment CD8 T-cell responses to ovarian cancer TAA. METHOD OF STUDY: Human DC were generated from blood monocytes by conventional in vitro differentiation and loaded with either soluble tumor lysate or NP/lysate conjugates (NPL). These antigen-loaded DC were then used to stimulate autologous CD8(+) T cells. Cytokine production and activation markers were evaluated in the CD8(+) T cells. RESULTS: DC loading with NPL increased cytokine production by stimulated CD8 T cells and induced T-cell expression of cell surface co-stimulatory molecules, typical of anti-tumor immune responses. In contrast, delivery of naked tumor lysate antigens preferentially induced a T-cell profile characteristic of tolerization/exhaustion. CONCLUSION: These findings indicate that delivery of TAA in NP enables DC to efficiently activate anti-tumor CD8(+) T cells. PLGA NP encapsulation of tumor-derived lysate protein antigens is an encouraging new preparative methodology for DC-based vaccination meriting clinical testing.