Frequency Of Subpopulations Research Articles

TH1 Cell Frequency and Neutrophil-to-Lymphocyte Ratio in Hemodialysis: Potential Contributions to Patient Monitoring.

Introduction: Patients undergoing hemodialysis (HD) often exhibit an impaired cellular immune response, which may contribute to an increased susceptibility to infections and other complications. Th1 cells, a subset of T-helper cells, play a crucial role in cellular immunity. However, the modulation of Th1 cells by HD treatment remains unclear. Objective: This study aims to investigate the levels of circulating T cells, especially Th1 cells, and the neutrophil-to-lymphocyte ratio (NLR) in HD patients. Methods: We recruited 26 HD patients and 10 healthy volunteers. Demographical data were collected, and peripheral blood samples were analyzed. Absolute blood cell counts were determined, and T-cell populations were identified using flow cytometry. Th1 cells were defined as IFN-γ-producing CD4+ T cells after in vitro activation, and NLR was calculated through the ratio between the neutrophil and lymphocyte counts measured in peripheral blood. Results: We have observed a significant decrease in Th1 subpopulation frequency in HD patients, as well as significant correlations between immunological and demographic parameters, among which are the NLR values and the absolute values of T-cell subsets. Conclusions: These results seem to clarify the role of Th1 cells in modulating the immune responses of hemodialysis-treated patients, potentially considering its frequency as an indicator for CKD development.

HLA class I expression on human platelets is highly variable and correlates with distinct allele group frequencies.

Human leukocyte antigen (HLA) class I molecules are expressed on platelets and can represent a source of alloimmunization in recipients of platelet transfusions. HLA mismatch between donors and recipients may be associated with the induction of anti-HLA antibodies, which can culminate in refractoriness to platelet transfusions. In the present study we analyzed HLA allele group frequencies and HLA expression levels on human platelets from blood donors. Platelet-rich plasma was collected from 139 donors to monitor platelet HLA class I expression by flow cytometry. DNA from donors with high and low platelet HLA expression was used in the genotype studies. Frequencies of large and normal-sized platelet subpopulations were determined and HLA class I expression was studied. Mean platelet volume (MPV) and platelet large-cell ratio (P-LCR) were analyzed in both groups of donors. The analysis showed variable platelet HLA class I expression with significant differences among donors. HLA class I allele group frequencies in donors with high and low platelet HLA expression showed distinctive genotypic features strictly related to expression level. The main allele groups found in samples with high platelet HLA class I expression were HLA-A*02, -A*68, -B*15, -B*49, and -C*03. Platelet HLA class I expression did not change over time or during freezing-thawing cycles. The analysis of platelet subpopulations showed a statistically significant higher expression of HLA class I molecules on large platelets than on normal-sized platelets. Moreover, donors with high HLA class I expression showed a higher frequency of large platelets (p<0.0001). The analysis of P-LCR in both groups of donors showed a statistically significant difference (p<0.05) within high HLA-expressing donors. Our data suggest an allele-dependent expression of HLA class I molecules on human platelets with distinct HLA allele group frequencies and different platelet subpopulation frequencies among blood donors.

High prevalence of polymyxin-heteroresistant carbapenem-resistant Klebsiella pneumoniae and its within-host evolution to resistance among critically ill scenarios.

We aimed to explore the prevalence and within-host evolution of resistance in polymyxin-heteroresistant carbapenem-resistant Klebsiella pneumoniae (PHR-CRKP) in critically ill patients. We performed an epidemiological analysis of consecutive patients with PHR-CRKP from clinical cases. Our study investigated the within-host resistance evolution and its clinical significance during polymyxin exposure. Furthermore, we explored the mechanisms underlying the dynamic evolution of polymyxin resistance at both subpopulation and genetic levels, involved population analysis profile test, time-killing assays, competition experiments, and sanger sequencing. Additionally, comparative genomic analysis was performed on 713 carbapenemase-producing K. pneumoniae strains. We enrolled 109 consecutive patients, and PHR-CRKP was found in 69.7% of patients without previous polymyxin exposure. 38.1% of PHR-CRKP isolates exhibited polymyxin resistance and led to therapeutic failure in critically ill scenarios. An increased frequency of resistant subpopulations was detected during PHR-CRKP evolution, with rapid regrowth of resistant subpopulations under high polymyxin concentrations, and a fitness cost in an antibiotic-free environment. Mechanistic analysis revealed that diverse mgrB insertions and pmrB hypermutations contributed to the dynamic changes in polymyxin susceptibility in dominant resistant subpopulations during PHR evolution, which were validated by comparative genomic analysis. Several deleterious mutations (e.g. pmrBLeu82Arg, pmrBSer85Arg) were firstly detected during PHR-CRKP evolution. Indeed, specific sequence types of K. pneumoniae demonstrated unique deletions and deleterious mutations. Our study emphasizes the high prevalence of pre-existing heteroresistance in CRKP, which can lead to polymyxin resistance and fatal outcomes. Hence, it is essential to continuously monitor and observe the treatment response to polymyxins in appropriate critically ill scenarios.

Assessment of non-classical lymphocyte populations in patients with advanced lung cancer treated with Biomodulina T following platinum-based chemotherapy

Aim: Currently, malignant diseases represent a health issue worldwide. Among these, lung cancer is of growing importance, due to its high incidence and mortality. Chemotherapy, one of the most frequently used treatments, has shown its ability to induce accelerated immunosenescence in classic and as well non-classic lymphocyte compartments, being less described in the latter. The immune restoration strategies have demonstrated their ability to reverse immunosenescence and exhaustion markers in conventional lymphocyte subpopulations after chemotherapy. However, the possible immunorestorative effect on non-classical lymphocytes has not been widely reported. The aim of this study was to evaluate the effect of chemotherapy and the administration of a thymic polypeptide factor on non-classical lymphocyte populations in patients with advanced lung cancer. Methods: Eighteen patients with advanced lung cancer, were evaluated at baseline before and after platinum-based chemotherapy (4–6 cycles). All patients could complete treatment with a thymic polypeptide factor [Biomodulina T (BT)] at the end of chemotherapy. Blood from patients was collected by venipuncture in heparinized tubes before and after chemotherapy and at the end of BT treatment to analyze the frequencies of non-classical immune subpopulations by flow cytometry. Results: Natural killer (NK), natural killer T cells (NKT), and double-positive T lymphocyte (DPT) proportions reached normal values in patients diagnosed with advanced lung cancer before receiving cytotoxic treatment. Chemotherapy did not induce modifications in the total percent of NK, NKT, and DPT populations in these patients. However, the administration of BT decreased DPTs and NK cells expressing the cluster of differentiation (CD)57 molecule, which is considered a marker of immunosenescence. Conclusions: These results suggest a lower influence of platinum-based chemotherapy on non-classical lymphocytes and the potential to generate a reconstitution of lymphocyte subpopulations in patients with advanced lung cancer by using the thymic factor BT, which reveals a new possibility for improving the response to cancer immunotherapies [Cuban Public Registry of Clinical Trial (RPCEC, https://rpcec.sld.cu/en/trials/RPCEC00000358-En) identifier: RPCEC00000358].

High concentrations of Maraviroc do not alter immunological and metabolic parameters of CD4 T cells

Maraviroc (MVC) is an antiretroviral drug capable of binding to CCR5 receptors and block HIV entry into target cells. Moreover, MVC can activate NF-kB pathway and induce viral transcription in HIV-infected cells, being proposed as a latency reversal agent (LRA) in HIV cure strategies. However, the evaluation of immunological and metabolic parameters induced by MVC concentrations capable of inducing HIV transcription have not been explored in depth. We cultured isolated CD4 T cells in the absence or presence of MVC, and evaluated the frequency of CD4 T cell subpopulations and activation markers levels by flow cytometry, and the oxidative and glycolytic metabolic rates of CD4 T cells using a Seahorse Analyzer. Our results indicate that a high concentration of MVC did not increase the levels of activation markers, as well as glycolytic or oxidative metabolic rates in CD4 T cells. Furthermore, MVC did not induce significant changes in the frequency and activation levels of memory cell subpopulations. Our data support a safety profile of MVC as a promising LRA candidate since it does not induce alterations of the immunological and metabolic parameters that could affect the functionality of these immune cells.

Macrophage subpopulations in pediatric patients with lupus nephritis and other inflammatory diseases affecting the kidney

BackgroundMacrophages play an important role in the pathogenesis of lupus nephritis (LN), but less is known about macrophage subtypes in pediatric LN. Here we compared renal inflammation in LN with other inflammatory pediatric kidney diseases and assessed whether inflammation correlates with clinical parameters.MethodsUsing immunofluorescence microscopy, we analyzed renal biopsies from 20 pediatric patients with lupus nephritis (ISN/RPS classes II–V) and pediatric controls with other inflammatory kidney diseases for infiltration with M1-like (CD68 + /CD206 − , CD68 + /CD163 −), M2a-like (CD206 + /CD68 +), and M2c-like macrophages (CD163 + /CD68 +) as well as CD3 + T-cells, CD20 + B-cells, and MPO + neutrophilic granulocytes. In addition, the correlation of macrophage infiltration with clinical parameters at the time of renal biopsy, e.g., eGFR and serum urea, was investigated. Macrophage subpopulations were compared with data from a former study of adult LN patients.ResultsThe frequency of different macrophage subtypes in biopsies of pediatric LN was dependent on ISN/RPS class and showed the most pronounced M1-like macrophage infiltration in patients with LN class IV, whereas M2c-like macrophages were most abundant in class III and IV. Interestingly, on average, only half as many macrophages were found in renal biopsies of pediatric LN compared to adult patients with LN. The distribution of frequencies of macrophage subpopulations, however, was different for CD68 + CD206 + (M2a-like) but comparable for CD68 + CD163 − (M1-like) CD68 + CD163 + (M2c-like) cells in pediatric and adult patients. Compared to other inflammatory kidney diseases in children, fewer macrophages and other inflammatory cells were found in kidney biopsies of LN. Depending on the disease, the frequency of individual immune cell types varied, but we were unable to confirm disease-specific inflammatory signatures in our study due to the small number of pediatric cases. Worsened renal function, measured as elevated serum urea and decreased eGFR, correlated particularly strongly with the number of CD68 + /CD163 − M1-like macrophages and CD20 + B cells in pediatric inflammatory kidney disease.ConclusionAlthough M1-like macrophages play a greater role in pediatric LN patients than in adult LN patients, M2-like macrophages appear to be key players and are more abundant in other pediatric inflammatory kidney diseases compared to LN.

Dual-Targeting CD33/CD123 NANOBODY ® T Cell Engager Targeting Leukemia Blasts and Stem/Progenitor Cells in Relapsed AML

Acute myeloid leukemia (AML) is the most common adult hematologic malignancy. Relapse is common and salvage treatment with cytotoxic chemotherapy is rarely curative. Immunotherapy targeting surface antigens expressed in leukemia cells has emerged as an effective approach for AML treatment for patients who are older/unfit for or relapsed from/refractory to current regimens (Isidori A, et al. Frontiers Oncol. 2021). CD123 and CD33, two clinically validated targets in AML, are jointly expressed on blasts and leukemic stem cells (LSC) in &amp;gt;95% of AML patients. However, their expression is heterogenous between subclones and between patients which may impact the efficacy of single-targeting agents in certain patient populations. We recently reported a novel dual-targeting CD33/CD123 NANOBODY® T-cell engager (CD33/CD123-TCE) and demonstrated the anti-leukemia activity of CD33/CD123-TCE in AML with good safety profile in vivo (Dullaers M, et. al, JITC. 2022). Here we showed that CD33/CD123-TCE effectively targets AML blasts and LSC in relapsed AML. The cell surface expression profiling of samples from 55 patients with relapsed/refractory AML showed that all samples were positive for CD123 and CD33. The frequency of subpopulations in all samples co-expressing CD33 and CD123 is the most prominent, followed by single expression of CD123, and CD33. CD33-CD123- subset represented a minority. To investigate the anti-leukemia effect of CD33/CD123 TCE, we treated 18 primary samples for 7 days and assessed apoptosis by flow cytometry. Treatment of CD33/CD123 TCE at 2.5nM (low dose) and 25nM (high dose) induced more than 50% specific apoptosis in majority of bulk AML, with no significant difference between low and high dose of CD33/123 TCE. Analysis of cytotoxicity towards CD34+ AML-LSC revealed that CD33/CD123 TCE at low and high doses resulted in similar specific apoptosis of CD34+ cells, half of samples reached higher than 50% of apoptosis. Colony-forming assay in 2 primary samples further confirmed that CD33/CD123 TCE effectively inhibited the clonogenicity of primary AML cells expressing CD123 and CD33. While the average activity of CD33/CD123 TCE was comparable to single-targeting CD33-TCE and CD123-TCE reagents, in a subset of patient samples (11% of all samples), the dual-targeting CD33/CD123-TCE induced higher apoptosis in bulk and CD34+ AML cells compared to single-targeting controls, supporting utility of dual targeting. Concomitantly, CD3+ T cell expansion was observed in all dual- and single treatment groups, with a trend toward stronger amplification by CD33/CD123-TCE. Next, we examined AML and T cell phenotypes using mass cytometry (CyTOF) to characterize the impact of the TCE treatments. UMAP plus FlowSOM analysis revealed heterogenous subsets of LSC within samples and across patients. LSC subsets defined by CD34+ are known to co-express various surface markers associated with LSC-drug resistance and disease relapse including CD135 (FLT3), CD117 (c-kit), CLL-1, PD-L1 and TIM-3. These subsets were found highly sensitive to CD33/CD123-TCE, with subset CD34+CD38+CD117+PD-L1+CD123+ and CD34+CD38- showing greater sensitivity to CD33/CD123-TCE. Despite diverse expression of leukemic markers, CD33/CD123-TCE depleted CD34+ AML-LSC in all 3 samples tested by CyTOF, whereas single-targeting CD123-TCE and CD33-TCE were only effective in 2/3 samples. Analysis of T cell subsets revealed that dual- or single- targeting TCE expanded CD4+ helper and CD8+ cytotoxic subsets in all samples compared to control. CD4+ and CD8+ cells co-expressing CD69, TIM-3 or PD-1 were expanded by TCE in all three samples. Expansion of central and effector memory T cells defined by CCR7+CD45RA- and CCR7-CD45RA- in CD4+ and CD8+ subsets were seen in all treatment groups in 2 samples, whereas the highest expansion of CCR7-CD45RA-CD4+ effector memory subsets by CD33/CD123-TCE was seen in 1 sample. Taken together, the CD33/CD123 dual-targeting NANOBODY® TCE exhibits potent anti-AML activity and offers a broad patient coverage. Immunophenotypic profiling confirmed the effectiveness of CD33/CD123-TCE in eliminating various blast- and LSC-subsets, activating CD4+ and CD8+ T cells or expanding central/effector memory CD4+ and CD8+ T cells. These dual-targeting immune engagers may constitute an effective treatment option for patients who are older/unfit for or relapsed from/refractory to current regimens.

BIOM-07. NON-TUMOR PLASMA EXTRACELLULAR VESICLES PREDICT THE OCCURRENCE OF GBM: A MACHINE LEARNING ANALYSIS

Abstract INTRODUCTION Glioblastoma (GBM) is the most common primary malignant brain tumor and has a poor clinical outcome. Extracellular vesicles (EVs) are promising biomarkers to assist the differential diagnosis between pseudoprogression and true tumor progression. We aimed to identify non-tumor plasma EV markers that predicted GBM occurrence using trained multiple tree-based machine learning algorithms. METHODS We included plasma samples of 40 GBM and 40 non-GBM (20 brain metastasis, 20 normal donors). Spectral flow cytometry was performed to determine plasma EV subpopulation frequency based on CD9,CD81,CD63,CD11b,CD45,CD31, and CD41a expression. Multiparametric t-SNE and FlowSOM analysis clustered plasma EVs based on these markers. Decision trees and random forest classifiers were trained and tested to predict the disease status (GBM vs non-GBM) based on plasma EV subpopulations. RESULTS Compared to non-GBM, GBM had increased frequency of CD9+ EVs (64.52% vs 40.69%, p&amp;lt; 0.0001), CD9+CD63-CD81- EVs (54.45% vs 37.26%, p&amp;lt; 0.0001) and myeloid-derived EVs (CD9+CD11b+ EVs, 20.77% vs 12.48%, p = 0.0241). In the decision tree analysis, low frequency of CD9+ EVs was found in 44% of all cases and represented a chance of 75% to be classified as non-GBM cases. An algorithm based on random forest analysis (n = 500 trees) using these markers had a sensitivity of 85.71% and specificity of 77.8% with an overall accuracy of 81.25% for identifying GBM. The frequencies of CD9+, CD9+CD63-CD81-, and CD9+CD63+CD81+ were the most critical factors in predicting GBM diagnosis. FlowSOM analysis identified 20 plasma EV subpopulations but had a lower accuracy (62.5%) when combined with our machine learning algorithm. CONCLUSIONS Non-tumor plasma EV expression profile combined with tree-based machine learning demonstrated high accuracy in predicting patient disease status. CD9+ EV frequency was one of the most promising biomarkers to assist in this diagnosis. We will continue to test our established algorithm and further validate our findings in a larger cohort.

BIOM-34. NON-NEOPLASTIC PLASMA EV SUBPOPULATIONS CORRELATE WITH TUMOR SIZE AND OVERALL SURVIVAL IN GLIOBLASTOMA INDEPENDENT OF STEROID USAGE

Abstract INTRODUCTION Extracellular Vesicles (EVs) are lipid bilayer particles present in almost all biofluids and carry tumor-specific molecular cargo. Plasma EVs are promising sources of biomarker discovery for glioblastoma (GBM). The clinical relevance of non-neoplastic plasma EVs in GBM remains unclear. In this study, we determine if associations exist between plasma EV subpopulation frequencies in GBM and clinical factors. METHODS Platelet-free plasma samples of 63 GBM, 43 Grade 2 glioma, and 45 healthy donors were included. All glioma plasma samples were collected before surgery. Plasma EV subpopulation frequency based on surface expression of EV-associated tetraspanins (CD9/CD81/CD63) and markers of cell origin (CD45/CD41a/CD11b/CD31) was determined by spectral flow cytometry. Clinical information including age, surgery, MGMT methylation status, corticosteroid usage, tumor volume, and overall survival data was recorded. RESULTS Compared to normal donors, GBM patients had increased CD9+, CD63+, CD81+, and CD11b+ EVs but decreased CD41a+ EVs. GBM patients also had the highest frequency of myeloid-derived CD9+CD11b+ EVs (20.17%) followed by grade 2 gliomas (13.78%) and normal donors (2.76%, p&amp;lt; 0.001). More GBM patients (29/63, 46.0%) received preoperative corticosteroids than grade 2 glioma patients (9/43, 20.9%; p = 0.008). Corticosteroid use was not associated with differences in EV subpopulation frequencies in GBM or grade 2 glioma patients. Pearson correlation analysis showed weak but statistically significant correlations between GBM total tumor volume and CD9+ EVs (p = 0.014), CD41a+ EVs (p = 0.037), and CD9+/CD63-/CD81- EVs (p = 0.007). In GBM patients, younger age (&amp;lt; 60 yrs, p = 0.01), gross total resection (p = 0.02), MGMT methylation (p = 0.002), high CD9+ EV expression (p = 0.011), low CD9+CD63-CD81- EV expression (p = 0.009) and low CD9+CD11b+ EV expression (p = 0.006) correlated with longer overall survival. CONCLUSION Differentially expressed non-neoplastic plasma EV subpopulations have significant clinical relevance in GBM including association with tumor volume and predicting survival. Validation of those markers in larger cohorts could reveal new prognostic biomarkers for GBM.

IS1-related large-scale deletion of chromosomal regions harbouring the oxygen-insensitive nitroreductase gene nfsB causes nitrofurantoin heteroresistance in Escherichia coli.

Nitrofurantoin is a broad-spectrum first-line antimicrobial used for managing uncomplicated urinary tract infection (UTI). Loss-of-function mutations in chromosomal genes nfsA, nfsB and ribE of Escherichia coli are known to reduce nitrofurantoin susceptibility. Here, we report the discovery of nitrofurantoin heteroresistance in E. coli clinical isolates and a novel genetic mechanism associated with this phenomenon. Subpopulations with lower nitrofurantoin susceptibility than major populations (hereafter, nitrofurantoin-resistant subpopulations) in two E. coli blood isolates (previously whole-genome sequenced) were identified using population analysis profiling. Each isolate was known to have a loss-of-function mutation in nfsA. From each isolate, four nitrofurantoin-resistant isolates were derived at a nitrofurantoin concentration of 32 mg l-1, and a comparator isolate was obtained without any nitrofurantoin exposure. Genomes of derived isolates were sequenced on Illumina and Nanopore MinION systems. Genetic variation between isolates was determined based on genome assemblies and read mapping. Nitrofurantoin minimum inhibitory concentrations (MICs) of both blood isolates were 64 mg l-1, with MICs of major nitrofurantoin-susceptible populations varying from 4 to 8 mg l-1. Two to 99 c.f.u. per million demonstrated growth at the nitrofurantoin concentration of 32 mg l-1, which is distinct from that of a homogeneously susceptible or resistant isolate. Derived nitrofurantoin-resistant isolates had 11-66 kb deletions in chromosomal regions harbouring nfsB, and all deletions were immediately adjacent to IS1-family insertion sequences. Our findings demonstrate that the IS1-associated large-scale genetic deletion is a hitherto unrecognized mechanism of nitrofurantoin heteroresistance and could compromise UTI management. Further, frequencies of resistant subpopulations from nitrofurantoin-heteroresistant isolates may challenge conventional nitrofurantoin susceptibility testing in clinical settings.

Transcriptome alterations in peripheral blood B cells of patients with multiple sclerosis receiving immune reconstitution therapy

BackgroundMultiple sclerosis (MS) is a chronic, inflammatory and neurodegenerative disease that leads to irreversible damage to the brain and spinal cord. The goal of so-called "immune reconstitution therapies" (IRTs) is to achieve long-term disease remission by eliminating a pathogenic immune repertoire through intense short-term immune cell depletion. B cells are major targets for effective immunotherapy in MS.ObjectivesThe aim of this study was to analyze the gene expression pattern of B cells before and during IRT (i.e., before B-cell depletion and after B-cell repopulation) to better understand the therapeutic effects and to identify biomarker candidates of the clinical response to therapy.MethodsB cells were obtained from blood samples of patients with relapsing–remitting MS (n = 50), patients with primary progressive MS (n = 13) as well as healthy controls (n = 28). The patients with relapsing MS received either monthly infusions of natalizumab (n = 29) or a pulsed IRT with alemtuzumab (n = 15) or cladribine (n = 6). B-cell subpopulation frequencies were determined by flow cytometry, and transcriptome profiling was performed using Clariom D arrays. Differentially expressed genes (DEGs) between the patient groups and controls were examined with regard to their functions and interactions. We also tested for differences in gene expression between patients with and without relapse following alemtuzumab administration.ResultsPatients treated with alemtuzumab or cladribine showed on average a > 20% lower proportion of memory B cells as compared to before IRT. This was paralleled by profound transcriptome shifts, with > 6000 significant DEGs after adjustment for multiple comparisons. The top DEGs were found to regulate apoptosis, cell adhesion and RNA processing, and the most highly connected nodes in the network of encoded proteins were ESR2, PHB and RC3H1. Higher mRNA levels of BCL2, IL13RA1 and SLC38A11 were seen in patients with relapse despite IRT, though these differences did not pass the false discovery rate correction.ConclusionsWe show that B cells circulating in the blood of patients with MS undergoing IRT present a distinct gene expression signature, and we delineated the associated biological processes and gene interactions. Moreover, we identified genes whose expression may be an indicator of relapse risk, but further studies are needed to verify their potential value as biomarkers.

Defining the spatial distribution of extracellular adenosine revealed a myeloid-dependent immunosuppressive microenvironment in pancreatic ductal adenocarcinoma

BackgroundThe prognosis for patients with pancreatic ductal adenocarcinoma (PDAC) remains extremely poor. It has been suggested that the adenosine pathway contributes to the ability of PDAC to evade the immune...

Frequency of B-Cell Subpopulations in Low Responders in Comparison with High Responders to Hepatitis B Vaccine Among Health Care Workers.

Vaccination is the most effective way to prevent Hepatitis B (HB) infection. The goal of vaccination is to induce immunological memory. Hence, determining the frequency of memory B-cell (MBC) subsets is an important indicator of vaccine efficacy. This study aimed to evaluate the frequency of different B-cell subpopulations and the expression of PD-1 on B-cell subsets in low responders (LR) and high responders (HR) to HB vaccine. According to our findings, the expression level of PD-1 was significantly higher on atypical MBC (atMBC) than that of naive B cell and classical MBC (cMBC) in LR and HR groups. Moreover, cMBCs had a significant higher PD-1 expression than naive B cells in LR group. No significant differences were found in the frequency of various B-cell subpopulations and the expression level of PD-1 on B-cell subsets between LR and HR groups. We observed a negative correlation between age and HBsAb titer and a positive correlation between age and PD-1 expression level on cMBC in LR group. It can be concluded that inadequate specific memory B-cell response, rather than total memory B-cell deficiency, may be implicated in low responsive rate to HB vaccine in healthy individuals.

Investigating the Potential of Cuboidal Nanometals as Protein Subunit Vaccine Carriers In Vivo

AbstractMetal nanoparticles (NPs) are suggested as a vaccine delivery platform. At present, there is limited description of cuboidal Ag nanocubes (AgNCs; nonporous) and Au nanocages (AuNCs; porous) as a protein carrier for vaccination. Here, the intrinsic protein binding ability of AgNC and AuNC is first investigated, using ovalbumin (OVA) as a model antigen, to determine its suitability as a vaccine carrier. Next, the effect of AgNCs and AuNCs on bone‐marrow‐derived dendritic cells (BMDCs) is assessed in vitro. Finally, in vivo humoral and cellular immune responses of AgNC–OVA and AuNC–OVA following intramuscular immunization and their prophylactic effects in B16F10‐OVA mice tumor model are investigated. In terms of OVA loading efficiency, AgNCs are superior to AuNCs. Both nanomaterials are found not to induce BMDC maturation at subtoxic doses. After administration of nanovaccines, serum immunoglobulin G (IgG) responses are comparable between groups. However, there are slight alterations in relative frequencies of lymphocyte subpopulations, with AgNC–OVA‐immunized mice exhibiting lower memory T cells and reduced B cell and T follicular helper cell populations in spleen. Overall, AgNC–OVA and AuNC–OVA immunizations do not alter tumor growth. This study characterizes the intrinsic immunomodulatory properties of AgNCs and AuNCs, as protein subunit vaccine carriers.

Dysregulated NAD(H) homeostasis associated with ciprofloxacin tolerance in Escherichia coli investigated on a single-cell level with the Peredox [NADH:NAD+] biosensor.

Antibiotic persistence (subpopulation tolerance) occurs when a subpopulation of antibiotic sensitive cells survives prolonged exposure to a bactericidal concentration of an antibiotic, and is capable of regrowth once the antibiotic is removed. This phenomenon has been shown to contribute to prolonged treatment duration, infection recurrence, and accelerated development of genetic resistance. Currently, there are no biomarkers which would allow for segregation of these antibiotic-tolerant cells from the bulk population prior to antibiotic exposure, limiting research on this phenomenon to retrograde analyses. However, it has been previously shown that persisters often have a dysregulated intracellular redox homeostasis, warranting its investigation as a potential marker for antibiotic tolerance. Furthermore, it is currently unknown whether another antibiotic tolerant subpopulation - viable but non-culturable cells (VBNCs), are simply persisters with extreme lag phase, or are formed through separate pathways. VBNCs similarly to persisters remain viable following antibiotic exposure, however, are not capable of regrowth in standard conditions. In this article we employed an NADH:NAD+ biosensor (Peredox) to investigate NADH homeostasis of ciprofloxacin-tolerant E. coli cells on a single-cell level. [NADH:NAD+] was used as a proxy for measuring intracellular redox homeostasis and respiration rate. First, we demonstrated that ciprofloxacin exposure results in a high number of VBNCs, several orders of magnitude higher than persisters. However, we found no correlation in the frequencies of persister and VBNC subpopulations. Ciprofloxacin-tolerant cells (persisters & VBNCs) were actively undergoing respiration, although at a significantly lower rate on average when compared to the bulk population. We also noted significant heterogeneity on a single-cell level within the subpopulations, however were unable to segregate persisters from VBNCs based on these observations alone. Finally, we showed that in the highly-persistent strain of E. coli, E. coli HipQ, ciprofloxacin-tolerant cells have a significantly lower [NADH:NAD+] ratio than tolerant cells of its parental strain, providing further link between disturbed NADH homeostasis and antibiotic tolerance.

P35 Heteroresistance to cefiderocol in clinical Gram-negative isolates

Abstract Background Heteroresistance is a phenotype in which a clinically susceptible bacterial isolate contains less susceptible subpopulations. Unexpectedly high levels of treatment failure for cefiderocol, a novel antibiotic designed to treat multidrug-resistant infections, have been attributed to this phenomenon. Objectives To determine prevalence of cefiderocol heteroresistance amongst clinical isolates at a North London tertiary care centre and study the population dynamics upon exposure to the antibiotic. Methods Gram-negative clinical isolates (n = 146) were screened for cefiderocol susceptibility by standard disc diffusion and Etest assays. Isolates were classified based on EUCAST breakpoints for cefiderocol susceptibility. Heteroresistance was confirmed by performing modified-population analysis profile (mPAP) assay in iron-depleted Mueller Hinton II agar. MIC values were determined by broth microdilution (BMD) assay as per EUCAST guidelines. The heteroresistant isolates and their corresponding less susceptible subpopulations were serially passaged in media with sub-inhibitory concentrations of cefiderocol as well as in cefiderocol-free medium. The changes in frequency and/or susceptibility in the heteroresistant subpopulation were detected using mPAP. Results Eleven heteroresistant (7.53%) and twenty-two resistant (15.06%) isolates were identified. Cefiderocol susceptibility of the heteroresistant isolates after five passages in cefiderocol-free medium partially reverted to that of the parent population. However, this phenomenon was not observed in the cohort that was first passaged in cefiderocol-containing medium before passages in cefiderocol-free medium. When heteroresistant populations were passaged in cefiderocol-containing media at 0.25× MIC values, no MIC changes were observed after five serial passages; however, the proportion of less susceptible subpopulations increased by 1.2 log10 in one out of five isolates. Nevertheless, when the antibiotic pressure was removed by passaging in cefiderocol-free media for a further five serial passages, the MIC and/or frequency of the less susceptible colonies within the heteroresistant population further increased in 80% of the passaged isolates. In one isolate, the MIC of the heteroresistant sub-population increased by &amp;gt;32-fold while the frequency of the heteroresistant sub-population increased by 1.0 log10 in another. Conclusions The prevalence of heteroresistance to cefiderocol was around 7% amongst clinical isolates. The heteroresistant phenotypes were unstable unless exposed to cefiderocol. Such exposure may also increase the MIC and/or frequency of less susceptible cells within the heteroresistant population. This amplification can continue even after removal of antibiotic pressure. Developing methods for detecting heteroresistance to cefiderocol in clinical laboratories is essential. Clinicians need to take this phenomenon into account when planning treatment regimens to optimize the effectiveness of this invaluable addition to the antimicrobial armamentarium.

AhR agonist tapinarof ameliorates lupus autoimmunity by suppressing Tfh cell differentiation via regulation of the JAK2-STAT3 signaling pathway.

The aryl hydrocarbon receptor (AhR) is a critical regulator of the pathogenesis of autoimmune disorders. We aimed to investigate the therapeutic effect of the AhR agonist tapinarof during the development of systemic lupus erythematosus (SLE). MRL/lpr mice were intraperitoneally injected with 1 or 5 mg/kg tapinarof for 6 weeks. Kidney histopathology was evaluated using hematoxylin and eosin (H&E) and Periodic-Acid-Schiff (PAS) staining. Immunofluorescence microscopy was performed to detect immune complex renal depositions. Flow cytometry (FCM) analysis was carried out to determine the proportions of T and B cell subsets. Realtime qPCR was used to quantify the expression of Tfh cell-associated genes. We conducted an in vitro polarization experiment to observe the effect of tapinarof on Tfh differentiation. Western blotting was used to detect the expression of target proteins. We found that tapinarof treatment ameliorated lupus phenotypes, including splenomegaly, lymph node enlargement, kidney damages, immune complex deposition, and excessive secretion of antibodies. Additionally, we showed that Treg subpopulation frequencies significantly increased in MRL/lpr mice treated with tapinarof, while the proportion of Th1/Th2 cells was reduced after tapinarof administration. Moreover, tapinarof suppressed Tfh cell differentiation and germinal center (GC) reaction in vivo. The inhibitory effect of tapinarof on Tfh cells was further verified in the in vitro Tfh cell polarization experiment. Realtime qPCR revealed that tapinarof repressed the expression of Tfh signature genes. Mechanistically, tapinarof significantly inhibited the phosphorylation levels of JAK2 and STAT3. The capacity for Tfh differentiation was partially rescued by the STAT3 activator Colivelin TFA. Furthermore, our in vitro Tfh polarization experiments indicated that tapinarof suppressed Tfh cell development in SLE. Our data demonstrated that tapinarof modulated the JAK2-STAT3 pathway to suppress Tfh cell differentiation for the treatment of lupus symptoms in MRL/lpr mice.

Investigating the potential of silver nanocubes and gold nanocages as protein subunit vaccine carriers

Abstract Metal nanoparticles have been exploited as vaccine delivery platforms for various diseases. In particular, Ag and Au NPs of different size and shape have been shown to promote delivery of antigens and act as efficient adjuvants. Yet, there is limited description of cuboidal Ag nanocubes (AgNCs) and Au nanocages (AuNCs) as antigen carriers for vaccination. Here, we first investigated the intrinsic protein binding ability of AgNCs and AuNCs, using ovalbumin (OVA) as a model. Next, the effect of AgNCs and AuNCs on bone marrow-derived dendritic cells (BMDCs) in terms of cytotoxicity and maturation was assessed. Finally, we investigated humoral and cellular immune responses of AgNCs-OVA and AuNCs-OVA following intramuscular immunization and their prophylactic effects in B16F10-OVA mice tumor model. In terms of OVA loading efficiency, AgNCs were more potent than AuNCs, despite their non-porous form. Both cubic nanomaterials were found not to induce BMDCs maturation in vitro or DCs maturation in spleen. Following the administration of nanovaccine doses, serum IgG responses were comparable between groups. However, there were significant alterations in relative frequencies of lymphocyte sub-populations. Overall, AgNCs-OVA and AuNCs-OVA immunization via intramuscular route did not alter tumour growth. This study has demonstrated the intrinsic immunomodulatory properties of AgNCs and AuNCs, preceding their potential use as nanocarriers. Supported by grants from British Council (Newton Fund, 337313), Wellcome Trust (WT103913), and TUBITAK.

Circulating SARS-CoV-2+ megakaryocytes are associated with severe viral infection in COVID-19

AbstractSeveral independent lines of evidence suggest that megakaryocytes are dysfunctional in severe COVID-19. Herein, we characterized peripheral circulating megakaryocytes in a large cohort of inpatients with COVID-19 and correlated the subpopulation frequencies with clinical outcomes. Using peripheral blood, we show that megakaryocytes are increased in the systemic circulation in COVID-19, and we identify and validate S100A8/A9 as a defining marker of megakaryocyte dysfunction. We further reveal a subpopulation of S100A8/A9+ megakaryocytes that contain severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) protein and RNA. Using flow cytometry of peripheral blood and in vitro studies on SARS-CoV-2–infected primary human megakaryocytes, we demonstrate that megakaryocytes can transfer viral antigens to emerging platelets. Mechanistically, we show that SARS-CoV-2–containing megakaryocytes are nuclear factor κB (NF-κB)-activated, via p65 and p52; express the NF-κB–mediated cytokines interleukin-6 (IL-6) and IL-1β; and display high surface expression of Toll-like receptor 2 (TLR2) and TLR4, canonical drivers of NF-κB. In a cohort of 218 inpatients with COVID-19, we correlate frequencies of megakaryocyte subpopulations with clinical outcomes and show that SARS-CoV-2–containing megakaryocytes are a strong risk factor for mortality and multiorgan injury, including respiratory failure, mechanical ventilation, acute kidney injury, thrombotic events, and intensive care unit admission. Furthermore, we show that SARS-CoV-2+ megakaryocytes are present in lung and brain autopsy tissues from deceased donors who had COVID-19. To our knowledge, this study offers the first evidence implicating SARS-CoV-2+ peripheral megakaryocytes in severe disease and suggests that circulating megakaryocytes warrant investigation in inflammatory disorders beyond COVID-19.

Abstract PD9-04: Immunological and clinical consequences of durvalumab treatment in combination to neoadjuvant chemotherapy in triple-negative breast cancer patients

Abstract Background: The implementation of immune checkpoint inhibitors in the therapy of different cancer types has provided promising results, but only a limited number of patients respond. Therefore, biomarkers to identify these responding patients are urgently needed. Methods: The GeparNuevo was a randomized, double-blind phase II trial in which triple-negative breast cancer (TNBC) patients were treated with neoadjuvant chemotherapy (NACT) consisting of nanoparticle albumin-bound paclitaxel in an initial phase followed by treatment with epirubicin and cyclophosphamide. Placebo or durvalumab were given throughout the neo-adjuvant treatment and in the “window” sub-cohort also prior to chemotherapy. Primary objective of this report was to evaluate changes in the blood immune cell repertoires of TNBC patients receiving durvalumab (anti-PD-L1) versus placebo in combination with NACT. At up to 4 different time points during therapy, blood samples were taken and underwent immunomonitoring using multicolor flow cytometry. The absolute counts of the major immune cell subtypes in the blood as well as the frequencies of different immune cell subpopulations and their functional phenotypes along treatment were determined and correlated to clinico-pathologic characteristics of the patients and to treatment response. Results: 120 out of 174 patients included in the GeparNuevo trial underwent blood immunomonitoring; 63 patients belonged to the “window” sub-cohort. Durvalumab administration almost completely blocked the detection of the inhibitory ligand PD-L1 and induced changes in the composition of the immune cell subpopulations. Evaluation of the “window” sub-cohort, in which an enhanced, but not significant pathological clinical response was observed within the immunomonitored patients, identified different markers correlating with clinical response to durvalumab. Higher frequencies of CD4+ T cells at recruitment as well as increased frequencies of T cells bearing the gamma delta TCR along treatment were some of the characteristics of patients responding to durvalumab treatment. Conclusions: The flow cytometry-based immunomonitoring of the clinical trial identified different immune-relevant biomarkers at recruitment as well as during treatment that predict clinical response to durvalumab. After validation of this data in an independent patient cohort, these markers could be implemented for an improved patient stratification to immunotherapy. Citation Format: Chiara Massa, Thomas Karn, Karsten Weber, Andreas Schneeweiss, Claus Hanusch, Jens-Uwe Blohmer, Dirk-Michael Zahm, Christian Jackisch, Marion van Mackelenbergh, Jörg Thomalla, Frederik Marmé, Jens Huober, Volkmar Müller, Christian Schem, Anja Müller, Elmar Stickeler, Katharina Biehl, Peter A. Fasching, Michael Untch, Sibylle Loibl, Carsten Denkert, Barbara Seliger. Immunological and clinical consequences of durvalumab treatment in combination to neoadjuvant chemotherapy in triple-negative breast cancer patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD9-04.