Dendritic cells process synthetic long peptides better than whole protein, improving antigen presentation and T-cell activation.

The efficiency of antigen (Ag) processing by dendritic cells (DCs) is vital for the strength of the ensuing T-cell responses. Previously, we and others have shown that in comparison to protein vaccines, vaccination with synthetic long peptides (SLPs) has shown more promising (pre-)clinical results. Here, we studied the unknown mechanisms underlying the observed vaccine efficacy of SLPs. We report an in vitro processing analysis of SLPs for MHC class I and class II presentation by murine DCs and human monocyte-derived DCs. Compared to protein, SLPs were rapidly and much more efficiently processed by DCs, resulting in an increased presentation to CD4⁺ and CD8⁺ T cells. The mechanism of access to MHC class I loading appeared to differ between the two forms of Ag. Whereas whole soluble protein Ag ended up largely in endolysosomes, SLPs were detected very rapidly outside the endolysosomes after internalization by DCs, followed by proteasome- and transporter associated with Ag processing-dependent MHC class I presentation. Compared to the slower processing route taken by whole protein Ags, our results indicate that the efficient internalization of SLPs, accomplished by DCs but not by B or T cells and characterized by a different and faster intracellular routing, leads to enhanced CD8⁺ T-cell activation.

Efficient ex vivo induction of T cells with potent anti-tumor activity by protein antigen encapsulated in nanoparticles.

Protein antigen (Ag)-based immunotherapies have the advantage to induce T cells with a potentially broad repertoire of specificities. However, soluble protein Ag is generally poorly cross-presented in MHC class I molecules and not efficient in inducing robust cytotoxic CD8(+) T cell responses. In the present study, we have applied poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NP) which strongly improve protein Ag presentation by dendritic cells (DC) in the absence of additional Toll-like receptor ligands or targeting devices. Protein Ag-loaded DC were used as antigen presenting cells to stimulate T cells in vitro and subsequently analyzed in vivo for their anti-tumor effect via adoptive transfer, a treatment strategy widely studied in clinical trials as a therapy against various malignancies. In a direct comparison with soluble protein Ag, we show that DC presentation of protein encapsulated in plain PLGA-NP results in efficient activation of CD4(+) and CD8(+) T cells as reflected by high numbers of activated CD69(+) and CD25(+), interferon (IFN)-γ and interleukin (IL)-2-producing T cells. Adoptive transfer of PLGA-NP-activated CD8(+) T cells in tumor-bearing mice displayed good in vivo expansion capacity, potent Ag-specific cytotoxicity and IFN-γ cytokine production, resulting in curing mice with established tumors. We conclude that delivery of protein Ag through encapsulation in plain PLGA-NP is a very efficient and simple procedure to stimulate potent anti-tumor T cells.

Virtual Reality Simulator versus Conventional Advanced Life Support Training for Cardiopulmonary Resuscitation Post-Cardiac Surgery: A Randomized Controlled Trial.

External chest compressions are often ineffective for patients arresting after cardiac surgery, for whom emergency resternotomy may be required. A single-blinded randomized controlled trial (RCT) was performed, with participants being randomized to a virtual reality (VR) Cardiac Surgical Unit Advanced Life Support (CSU-ALS) simulator training arm or a conventional classroom CSU-ALS training arm. Twenty-eight cardiothoracic surgery (CTS) residents were included and subsequently assessed in a moulage scenario in groups of two, either participating as a leader or surgeon. The primary binary outcomes were two time targets: (1) delivering three stacked shocks within 1 min and (2) resternotomy within 5 min. Secondary outcomes were the number of protocol mistakes made and a questionnaire after the VR simulator. The conventional training group administered stacked shocks within 1 min in 43% (n = 6) of cases, and none in the VR group reached this target, missing it by an average of 25 s. The resternotomy time target was reached in 100% of the cases (n = 14) in the conventional training group and in 83% of the cases (n = 10) in the VR group. The VR group made 11 mistakes in total versus 15 for those who underwent conventional training. Participants reported that the VR simulator was useful and easy to use. The results show that the VR simulator can provide adequate CSU-ALS training. Moreover, VR training results in fewer mistakes suggesting that repetitive practice in an immersive environment improves skills.

Virtual reality simulation as a training tool for perfusionists in extracorporeal circulation: Establishing face and content validity.

Objective: We conducted a prospective study to assess the face and content validity of a new virtual reality (VR) extracorporeal circulation simulator (ECC) developed for perfusionists to facilitate training and practice. We evaluated the opinions of students and staff members about the feasibility of the simulation. The 2 groups consisted of experts (qualified perfusionists) and novices (trainee perfusionists). Methods: Perfusionists (n = 12 experts and n = 11 trainees) received instructions on how to use the VR simulator and then proceeded to perform the start of cardiopulmonary bypass in the VR environment. Participants then completed a Usefulness, Satisfaction, and Ease of Use Questionnaire. The questions were rated on a 5-point Likert scale, ranging from 1 (fully disagree) to 5 (fully agree), to assess the face validity and content validity of this simulator. Results: Participants reported a predominantly positive experience with the VR-ECC simulator, with 96% (n = 22) agreeing that the simulator was a useful way of training ECC scenarios. All participants found it easy to interact with the software (100%, n = 23), and 82% of students (n = 9) believed it helped them remember the steps involved with initiating ECC. Finally, (87% [n = 20]) of participants believed the image quality and depth perception were good. Conclusions: Our next-generation simulator was valid for face and content constructs, and almost all participants found it to be a useful way of training for ECC scenarios. This simulator represents a first step toward truly blended digital learning and a new interactive, flexible, and innovative modality for perfusion training.

Virtual Reality Simulation Training for Cardiopulmonary Resuscitation After Cardiac Surgery: Face and Content Validity Study.

BACKGROUND: Cardiac arrest after cardiac surgery commonly has a reversible cause, where emergency resternotomy is often required for treatment, as recommended by international guidelines. We have developed a virtual reality (VR) simulation for training of cardiopulmonary resuscitation (CPR) and emergency resternotomy procedures after cardiac surgery, the Cardiopulmonary Resuscitation Virtual Reality Simulator (CPVR-sim). Two fictive clinical scenarios were used: one case of pulseless electrical activity (PEA) and a combined case of PEA and ventricular fibrillation. In this prospective study, we researched the face validity and content validity of the CPVR-sim. OBJECTIVE: We designed a prospective study to assess the feasibility and to establish the face and content validity of two clinical scenarios (shockable and nonshockable cardiac arrest) of the CPVR-sim partly divided into a group of novices and experts in performing CPR and emergency resternotomies in patients after cardiac surgery. METHODS: Clinicians (staff cardiothoracic surgeons, physicians, surgical residents, nurse practitioners, and medical students) participated in this study and performed two different scenarios, either PEA or combined PEA and ventricular fibrillation. All participants (N=41) performed a simulation and completed the questionnaire rating the simulator's usefulness, satisfaction, ease of use, effectiveness, and immersiveness to assess face validity and content validity. RESULTS: Responses toward face validity and content validity were predominantly positive in both groups. Most participants in the PEA scenario (n=26, 87%) felt actively involved in the simulation, and 23 (77%) participants felt in charge of the situation. The participants thought it was easy to learn how to interact with the software (n=24, 80%) and thought that the software responded adequately (n=21, 70%). All 15 (100%) expert participants preferred VR training as an addition to conventional training. Moreover, 13 (87%) of the expert participants would recommend VR training to other colleagues, and 14 (93%) of the expert participants thought the CPVR-sim was a useful method to train for infrequent post-cardiac surgery emergencies requiring CPR. Additionally, 10 (91%) of the participants thought it was easy to move in the VR environment, and that the CPVR-sim responded adequately in this scenario. CONCLUSIONS: We developed a proof-of-concept VR simulation for CPR training with two scenarios of a patient after cardiac surgery, which participants found was immersive and useful. By proving the face validity and content validity of the CPVR-sim, we present the first step toward a cardiothoracic surgery VR training platform.

Interleukin-2 signals converge in a lymphoid-dendritic cell pathway that promotes anticancer immunity.

Tumor-infiltrating dendritic cells (DCs) correlate with effective anticancer immunity and improved responsiveness to anti-PD-1 checkpoint immunotherapy. However, the drivers of DC expansion and intratumoral accumulation are ill-defined. We found that interleukin-2 (IL-2) stimulated DC formation through innate and adaptive lymphoid cells in mice and humans, and this increase in DCs improved anticancer immunity. Administration of IL-2 to humans within a clinical trial and of IL-2 receptor (IL-2R)-biased IL-2 to mice resulted in pronounced expansion of type 1 DCs, including migratory and cross-presenting subsets, and type 2 DCs, although neither DC precursors nor mature DCs had functional IL-2Rs. In mechanistic studies, IL-2 signals stimulated innate lymphoid cells, natural killer cells, and T cells to synthesize the cytokines FLT3L, CSF-2, and TNF. These cytokines redundantly caused DC expansion and activation, which resulted in improved antigen processing and correlated with favorable anticancer responses in mice and patients. Thus, IL-2 immunotherapy-mediated stimulation of DCs contributes to anticancer immunity by rendering tumors more immunogenic.

Continuous venovenous hemodiafiltration using cytokine-adsorbing hemofilters as adjuvant therapy for anaerobic descending necrotizing mediastinitis: a case report.

BACKGROUND: We describe a combinatorial intensive care approach and discuss the critical factors that allowed us to successfully manage a life-threatening case of acute anaerobic septic shock triggered by descending necrotizing mediastinitis. CASE PRESENTATION: We admitted a 38-year-old critically ill Kosovar Albanian man to our intensive care unit because of clinical manifestations of severe sepsis. His condition had worsened in the previous 2 weeks following unsuccessful antibiotic therapy for tonsillitis complicated by retropharyngeal abscesses. Computed tomography and intraoperative observations identified abscesses in the anterior and middle mediastinum regions and the distal part of the neck, directly on the border with the left lobe of the thyroid gland. Cultures indicated infections with α-hemolytic Streptococcus and Clostridium species: High procalcitonin and lactate levels, blood gas analysis, poor peripheral capillary oxygen saturation, and severe hemodynamic instability pointed to a case of acute septic shock. The entire treatment consisted of an aggressive antibiotic regimen, transthoracic and mediastinal surgical evacuation of the abscess, vacuum sealing drainage with a pleural chest tube, continuous venovenous hemodiafiltration using cytokine-adsorbing hemofilters, and extracorporeal blood hyperoxygenation. CONCLUSIONS: Efficient treatment of severe anaerobic sepsis resulting from descending necrotizing mediastinitis should build on a multidisciplinary approach. In support of first-line therapies with targeted antibiotics and surgical debridement, clinicians should consider alternative therapies such as continuous venovenous hemodiafiltration with cytokine-adsorbing hemofilters and hyperoxygenation.

The Histone Methyltransferase Ezh2 Controls Mechanisms of Adaptive Resistance to Tumor Immunotherapy.

Immunotherapy and particularly immune checkpoint inhibitors have resulted in remarkable clinical responses in patients with immunogenic tumors, although most cancers develop resistance to immunotherapy. The molecular mechanisms of tumor resistance to immunotherapy remain poorly understood. We now show that induction of the histone methyltransferase Ezh2 controls several tumor cell-intrinsic and extrinsic resistance mechanisms. Notably, T cell infiltration selectively correlated with high EZH2-PRC2 complex activity in human skin cutaneous melanoma. During anti-CTLA-4 or IL-2 immunotherapy in mice, intratumoral tumor necrosis factor-α (TNF-α) production and T cell accumulation resulted in increased Ezh2 expression in melanoma cells, which in turn silenced their own immunogenicity and antigen presentation. Ezh2 inactivation reversed this resistance and synergized with anti-CTLA-4 and IL-2 immunotherapy to suppress melanoma growth. These anti-tumor effects depended on intratumorally accumulating interferon-γ (IFN-γ)-producing PD-1low CD8+ T cells and PD-L1 downregulation on melanoma cells. Hence, Ezh2 serves as a molecular switch controlling melanoma escape during T cell-targeting immunotherapies.

CD40-targeted dendritic cell delivery of PLGA-nanoparticle vaccines induce potent anti-tumor responses.

Dendritic cells (DC) play a prominent role in the priming of CD8(+) T cells. Vaccination is a promising treatment to boost tumor-specific CD8(+) T cells which is crucially dependent on adequate delivery of the vaccine to DC. Upon subcutaneous (s.c.) injection, only a small fraction of the vaccine is delivered to DC whereas the majority is cleared by the body or engulfed by other immune cells. To overcome this, we studied vaccine delivery to DC via CD40-targeting using a multi-compound particulate vaccine with the aim to induce potent CD8(+) T cell responses. To this end, biodegradable poly(lactic-co-glycolic acid) nanoparticles (NP) were formulated encapsulating a protein Ag, Pam3CSK4 and Poly(I:C) and coated with an agonistic αCD40-mAb (NP-CD40). Targeting NP to CD40 led to very efficient and selective delivery to DC in vivo upon s.c. injection and improved priming of CD8(+) T cells against two independent tumor associated Ag. Therapeutic application of NP-CD40 enhanced tumor control and prolonged survival of tumor-bearing mice. We conclude that CD40-mediated delivery to DC of NP-vaccines, co-encapsulating Ag and adjuvants, efficiently drives specific T cell responses, and therefore, is an attractive method to improve the efficacy of protein based cancer vaccines undergoing clinical testing in the clinic.

Use of enhanced interleukin-2 formulations for improved immunotherapy against cancer.

The use of interleukin-2 (IL-2) for the stimulation of an effector immune response against metastatic cancer dates back to the early 1980s. Administration of unmodified IL-2, either alone or together with antigen-specific approaches, has resulted in remarkably long-term survival of some patients suffering from metastatic melanoma. However, such treatment is usually hampered by the appearance of toxic adverse effects, which has motivated the engineering of modified IL-2 formulations showing reduced toxicity while being more potent at stimulating anti-tumor effector immune cells. In this review we summarize and discuss the features and biological relevance of several enhanced IL-2 formulations, compare these to IL-15-based therapeutics, and try to foreshadow their potential in immunological research and immunotherapy.

Targeting nanoparticles to CD40, DEC-205 or CD11c molecules on dendritic cells for efficient CD8(+) T cell response: a comparative study.

Here we demonstrated the importance of targeting antigens (Ags) to dendritic cell (DC) receptors to achieve an efficient cytotoxic T cell response which was associated with a strong activation of DC. Pegylated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) were used to encapsulate ovalbumin (OVA) as a model Ag. This PLGA complex, together with Toll like receptor (TLR) 3 and 7 ligands, was then targeted to distinct DC cell-surface molecules. These cell-surface molecules, including CD40, a TNF-α family receptor, DEC-205, a C-type lectin receptor and CD11c, an integrin receptor, were targeted by means of specific monoclonal antibodies (mAbs) coupled to the NP. The efficiency of these different targeting strategies to activate DC and elicit a potent CD8(+) T cell response was studied. PLGA-(Ag/TLR3+7L) NP was more efficiently targeted to and internalized by DC in vitro compared to the control non-targeted NP. We observed a small but significantly improved internalization of CD40-targeted NP compared to DEC-205 or CD11c targeted NP. In contrast to non-targeted NP, all targeted NPs equally stimulated IL-12 production and expression of co-stimulatory molecules by DC, inducing strong proliferation and IFN-y production by T cells in vitro. Moreover, subcutaneous vaccination with CD40, DEC-205 and CD11c-targeted NP consistently showed higher efficacy than non-targeted NP in stimulating CD8+ T cell responses. However, all targeted NP vaccines showed an equal capacity to prime cytotoxic CD8+ T cells, which subsequently were able to induce targeted cell lysis. In conclusion, delivery of NP-vaccines to DC by targeting via cell-surface molecules leads to strong enhancement of vaccine potency and induction of T cell responses compared to non-specific delivery of NP to DC.

Administration of anti-CD25 mAb leads to impaired α-galactosylceramide-mediated induction of IFN-γ production in a murine model.

CD4(+)CD25(+)Foxp3(+) T regulatory cells (Tregs) and CD1d-restricted invariant natural killer T (iNKT) cells are two cell types that are known to regulate immune reactions. Depletion or inactivation of Tregs using specific anti-CD25 antibodies in combination with immunostimulation is an attractive modality especially in anti-tumour immunotherapy. However, CD25 is not expressed exclusively on Tregs but also on subpopulations of activated lymphocytes. Therefore, the modulatory effects of the specific anti-CD25 antibodies can also be partially attributed to their interactions with the effector cells. Here, the effector functions of iNKT cells were analysed in combination with anti-CD25 mAb PC61. Upon PC61 administration, α-galactosylceramide (α-GalCer)-mediated activation of iNKT cells resulted in decreased IFN-γ but not IL-4 production. In order to determine whether mutual interactions between Tregs and iNKT cells take place, we compared IFNγ production after α-GalCer administration in anti-CD25-treated and "depletion of regulatory T cell" (DEREG) mice. Since no profound effects on IFNγ induction were observed in DEREG mice, deficient in FoxP3(+) Tregs, our results indicate that the anti-CD25 antibody acts directly on CD25(+) effector cells. In vivo experiments demonstrated that although both α-GalCer and PC61 administration inhibited TC-1 tumour growth in mice, no additive/synergic effects were observed when these substances were used in combination therapy.

Selective transduction of mature DC in human skin and lymph nodes by CD80/CD86-targeted fiber-modified adenovirus-5/3.

In vivo targeting of dendritic cells (DC) represents an attractive alternative to currently apply ex vivo DC-based genetic tumor vaccination protocols. Finding the optimal vector for in vivo targeting of DC is important for such strategies. We, therefore, tested a panel of subgroup C/B chimeric and fiber-modified adenoviruses (Ads) for their relative capacity to transduce human DC. We made use of in vitro generated Langerhans cells, and of ex vivo human skin and melanoma-draining lymph node derived DC. Of the tested viruses the C/B-chimeric adenovirus serotype 5 (Ad5)/3 virus most efficiently transduced in vitro generated Langerhans cells. In addition, Ad5/3 preferentially targeted mature myeloid DC from human skin and draining lymph node and transduced them at significantly higher frequencies than Ad5. In addition, Ad5/3 was more specific for mature human skin-derived CD1a+ CD83+ DC than the previously reported DC-transducing C/B-chimeric vector Ad5/35, infecting less bystander cells. It was previously reported that Ad5/3 transduced human monocyte-derived DC by binding to the B7 molecules CD80 and CD86. High-efficiency transduction of mature skin-derived DC was similarly shown to be mediated through binding to CD80/CD86 and not to interfere with subsequent T-cell priming. We conclude that Ad5/3, in combination with DC-activating adjuvants, represents a promising therapeutic tool for the in vivo transduction of mature DC, and may be less likely to induce unwanted side effects such as immune tolerance through the infection of nonprofessional antigen-presenting cells.