BackgroundType 1 conventional dendritic cells (cDC1s) possess efficient antigen presentation and cross-presentation activity, as well as potent T cell priming ability. Tissue-resident cDC1s (CD103+cDC1s in mice, CD141+cDC1s in humans) are linked with improved tumor control, yet the efficacy of immunotherapy using this population is understudied.MethodsWe generated murine CD103+cDC1s in vitro and examined their expression of cDC1-related factors, antigen cross-presentation activity, and accumulation in tumor-draining lymph nodes (TdLNs). The antitumor efficacy of the in vitro-generated CD103+cDC1s was studied in murine melanoma and osteosarcoma models. We evaluated tumor responses on vaccination with CD103+cDC1s, compared these to vaccination with monocyte-derived DCs (MoDCs), tested CD103+cDC1 vaccination with checkpoint blockade, and examined the antimetastatic activity of CD103+cDC1s.ResultsIn vitro-generated CD103+cDC1s produced cDC1-associated factors such as interleukin-12p70 and CXCL10, and demonstrated antigen cross-presentation activity on stimulation with the toll-like receptor 3 agonist polyinosinic:polycytidylic acid (poly I:C). In vitro-generated CD103+cDC1s also migrated to TdLNs following poly I:C treatment and intratumoral delivery. Vaccination with poly I:C-activated and tumor antigen-loaded CD103+cDC1s enhanced tumor infiltration of tumor antigen-specific and interferon-γ+CD8+T cells, and suppressed melanoma and osteosarcoma growth. CD103+cDC1s showed superior antitumor efficacy compared with MoDC vaccination, and led to complete regression of 100% of osteosarcoma tumors in combination with CTLA-4 antibody-mediated checkpoint blockade. In vitro-generated CD103+cDC1s effectively protected mice from pulmonary melanoma and osteosarcoma metastases.ConclusionsOur data indicate an in vitro-generated CD103+cDC1 vaccine elicits systemic and long-lasting tumor-specific T cell-mediated cytotoxicity, which restrains primary and metastatic tumor growth. The CD103+cDC1 vaccine was superior to MoDCs and enhanced response to immune checkpoint blockade. These results indicate the potential for new immunotherapies based on use of cDC1s alone or in combination with checkpoint blockade.
Dendritic cells (DCs) are the principal antigen-presenting cells of the immune system and play key roles in controlling immune tolerance and activation. As such, DCs are chief mediators of tumor immunity. DCs can regulate tolerogenic immune responses that facilitate unchecked tumor growth. Importantly, however, DCs also mediate immune-stimulatory activity that restrains tumor progression. For instance, emerging evidence indicates the cDC1 subset has important functions in delivering tumor antigens to lymph nodes and inducing antigen-specific lymphocyte responses to tumors. Moreover, DCs control specific therapeutic responses in cancer including those resulting from immune checkpoint blockade. DC generation and function is influenced profoundly by cytokines, as well as their intracellular signaling proteins including STAT transcription factors. Regardless, our understanding of DC regulation in the cytokine-rich tumor microenvironment is still developing and must be better defined to advance cancer treatment. Here, we review literature focused on the molecular control of DCs, with a particular emphasis on cytokine- and STAT-mediated DC regulation. In addition, we highlight recent studies that delineate the importance of DCs in anti-tumor immunity and immune therapy, with the overall goal of improving knowledge of tumor-associated factors and intrinsic DC signaling cascades that influence DC function in cancer.
e18666 Background: Pediatric Acute Lymphoblastic Leukemia/ Lymphoblastic Lymphoma (ALL/LLy) is the most common pediatric cancer. Invasive pneumococcal disease (IPD) is prevalent in this population and the Centers for Disease Control and Prevention recommends pneumococcal vaccination to decrease morbidity and mortality. Despite these recommendations, vaccination rates remain low and the incidence of IPD among children with hematologic malignancy is significantly higher compared to the average pediatric population. An interventional study was designed to improve the vaccination rate and reduce the incidence of IPD in our institution. Methods: A plan-do-study-act (PDSA) model of quality improvement (QI) was used. Chart review at our institute was done for the 6-month period of January 2020 - June 2020 and baseline rates for pneumococcal polysaccharide (PPSV23) vaccination were calculated. Patients were included if they were ≥ 2 years old, diagnosed with ALL/LLy, and undergoing maintenance. A multidisciplinary team performed the root cause analysis. Immunization records were obtained and reviewed and targeted interventions were implemented. The interventions used are outlined in Table. The percentage of pediatric ALL/LLy patients per month in maintenance who received age-appropriate pneumococcal vaccinations was monitored before and after the interventions. Results: Analysis of the 6-month retrospective cohort (n=36) showed a baseline vaccination rate of 5.5%. During the subsequent 6-month phase with interventions, 40 patients were prospectively enrolled. Demographics showed a mean age of 10.2 years (range, 2-21) and a predominantly male (66.7%) cohort. B-cell ALL/LLy comprised the majority (78.9%); the rest included T-cell ALL/LLy and mixed phenotype acute leukemia. As seen in Table, the percentage receiving at least 1 pneumococcal vaccine increased from 5.5% to 84.8% over the first 3 months, this plateaued around 81%. Completion of the series mirrored this and increased to 74.2%. Pre-visit planning and cues proved to be the most helpful interventions. Conclusions: Use of a PDSA model successfully improved pneumococcal vaccination rates in the pediatric ALL/LLy population. We suggest these results can be achieved with planning and implementation of the outlined interventions. [Table: see text]
Type 1 conventional dendritic cells (cDC1s) possess efficient antigen presentation and cross-presentation activity, yet the efficacy of immunotherapy utilizingthis population is understudied. We used in vitro-generated CD103+cDC1s in vaccination strategies to test their ability to control melanoma and osteosarcoma tumors. In vitro-generated CD103+cDC1s produced cDC1-associated factors such as IL-12p70 and CXCL10, and demonstrated antigen cross-presentation activity upon stimulation with the Toll-like receptor 3 (TLR3) agonist polyinosinic:polycytidylic acid (poly I:C). In vitro-generated CD103+cDC1s also migrated to tumor-draining lymph nodes (TdLNs) following poly I:C treatment and intratumoral (i.t.) delivery. Vaccination with poly I:C-activated and tumor antigen-loaded CD103+cDC1s enhanced tumor infiltration of tumor antigen-specific and IFN-g+CD8+ T cells, and suppressed melanoma and osteosarcoma growth. CD103+cDC1s showed superior anti-tumor efficacy compared to vaccination with monocyte-derived DCs (MoDCs), and led to complete regression of 100% of osteosarcoma tumors in combination with CTLA-4 antibody-mediated checkpoint blockade. In addition, CD103+cDC1s effectively protected mice from pulmonary melanoma and osteosarcoma metastases. Our data indicate an in vitro-generated CD103+cDC1 vaccine elicits systemic and long-lasting tumor-specific T cell-mediated cytotoxicity, which restrains primary and metastatic tumor growth. The CD103+cDC1 vaccine was superior to MoDCs and enhanced response to immune checkpoint blockade. These results indicate the potential for new immunotherapies based on use of cDC1s alone or in combination with checkpoint blockade.
Background In pediatric hematologic malignancy, the incidence of invasive fungal infections (IFI) is ~ 5-10% and leads to significant morbidity and mortality. Acute lymphoblastic leukemia (ALL) accounts for the largest group at risk and has the largest absolute number of IFI. Antifungal prophylaxis has the potential to mitigate risk of invasive infections in ALL but is not currently standard of care due to the paucity of data in ALL subgroups. A recent systematic review showed a significant reduction in proven/probable IFI and fungal infection-related mortality in pediatric patients when using a mold active agent compared with fluconazole, therefore an echinocandin was selected for systemic antifungal prophylaxis in our institution. In this study we investigate the incidence of IFI in patients with ALL in a highly endemic area (Ohio River Valley) and describe the impact of echinocandin prophylaxis in this population. Methods We conducted a retrospective cohort study of consecutive patients <25 years with ALL from 2015 to 2021 at Norton Children's Hospital, Louisville, KY. IFI was classified as possible, probable, or proven as defined by the 2020 European Organization for Research and Treatment of Cancer/ Mycoses Study Group Consensus Group. Patients were then analyzed in 2 subgroups based on prophylaxis with caspofungin. Inpatient administration of caspofungin was given to patients with high-risk B-ALL (HR B-ALL) and T-ALL as outlined in Table 1. Patient and IFI characteristics were collected, and cumulative incidence analyses used for subgroup comparisons. Results Demographics and patient characteristics are summarized in Table 2. Between 2015 to 2020 we identified 100 patients with ALL. Mean age at diagnosis was 7.2 years and 43% were female. We identified 14 unique cases of IFI in 13 patients with ALL who did not receive prophylaxis with caspofungin during 2015 to 2020 (14%). Prior to the implementation of prophylaxis, IFI occurred in 0% (0/43) of the SR B-ALL group, 18.2% (6/33) in HR B-ALL group and 35% (8/23) in T-ALL group. IFI incidence was highest in induction and consolidation phases (71.4%) and implicated species during these phases included Aspergillus, Candida, Fusarium, and Papulasopora. From April 2020 to July 2021, there were 22 newly diagnosed patients with ALL, 11 (50%) of whom received inpatient prophylaxis with caspofungin. There was 1 case (4.5%) of reported IFI during delayed intensification (no prophylaxis at the time of infection). As seen in Figure 1, patients with HR B-ALL and T-ALL who were hospitalized and received caspofungin during induction saw a notable decrease in the cumulative incidence of IFI, from 18.3% to 0% at 6 months into treatment before reaching similar levels in the patients who did not receive prophylaxis. Conclusion In our pediatric population, patients with T-ALL and HR B-ALL were more likely to develop IFI than those with SR B-ALL. Prophylaxis with caspofungin and inpatient hospitalization during induction were effective strategies for reducing the incidence of IFI in induction and consolidation for our high-risk leukemia population. This approach should be validated in larger studies with special consideration being given to patients in fungal endemic areas. Figure 1 Figure 1. Disclosures Raj: Terumo Medical Corporation: Honoraria, Speakers Bureau; Forma therapeutics: Consultancy; Global biotherapeutics: Speakers Bureau.
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