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Nitric oxide (NO) is produced in mammals by different isoforms of NO synthase (NOS), including the constitutive mitochondrial enzyme (mtNOS). Here we demonstrate that the concentration of NO resulting from a mitochondrial NOS activity increases under hypoxic conditions in isolated rat liver mitochondria. We show that mitochondrially derived NO mediates the impairment of active (state 3) respiration as measured in the presence of the substrates glutamate and malate after reoxygenation. Simultaneously, NO induces oxidative stress in mitochondria, characterized by an increase in the amount of protein carbonyls and a decrease in glutathione (GSH). Both the accumulation of oxidative stress markers during and the impaired respiration after reoxygenation were prevented by blocking NO production with the NOS inhibitor L-NAME. These observations suggest that mitochondria are exposed to high amounts of NO generated by a mitochondrial NOS upon hypoxia/reoxygenation. Such increased NO levels, in turn, inhibit mitochondrial respiration and may cause oxidative stress that leads to irreversible impairment of mitochondria.

Clinical development of chimeric antigen receptor (CAR)-T-cell therapy has been enabled by advances in synthetic biology, genetic engineering, clinical-grade manufacturing, and complex logistics to distribute the drug product to treatment sites. A key ambition of the CARAMBA project is to provide clinical proof-of-concept for virus-free CAR gene transfer using advanced Sleeping Beauty (SB) transposon technology. SB transposition in CAR-T engineering is attractive due to the high rate of stable CAR gene transfer enabled by optimized hyperactive SB100X transposase and transposon combinations, encoded by mRNA and minicircle DNA, respectively, as preferred vector embodiments. This approach bears the potential to facilitate and expedite vector procurement, CAR-T manufacturing and distribution, and the promise to provide a safe, effective, and economically sustainable treatment. As an exemplary and novel target for SB-based CAR-T cells, the CARAMBA consortium has selected the SLAMF7 antigen in multiple myeloma. SLAMF7 CAR-T cells confer potent and consistent anti-myeloma activity in preclinical assays in vitro and in vivo. The CARAMBA clinical trial (Phase-I/IIA; EudraCT: 2019-001264-30) investigates the feasibility, safety, and anti-myeloma efficacy of autologous SLAMF7 CAR-T cells. CARAMBA is the first clinical trial with virus-free CAR-T cells in Europe, and the first clinical trial that uses advanced SB technology worldwide.

Membrane wrapped nanoparticles represent a versatile platform for utilizing specific lipid-receptor interactions, such as siallyllactose-mediated binding of the ganglioside GM3 to Siglec1 (CD169), for targeting purposes. The membrane wrap around the nanoparticles does not only serve as a matrix to incorporate GM3 as targeting moiety for antigen presenting cells but also offers unique opportunities for constructing a biomimetic surface from lipids with potentially protein repellent properties. We characterize non-specific protein adsorption (corona formation) to membrane wrapped nanoparticles with core diameters of approx. 35 nm and 80 nm and its effect on the GM3-mediated targeting efficacy as function of surface charge through combined in vitro and in vivo studies. The stability and fate of the membrane wrap around the nanoparticles in a simulated biological fluid and after uptake in CD169 expressing antigen presenting cells is experimentally tested. Finally, we demonstrate in hock immunization studies in mice that GM3 decorated membrane wrapped nanoparticles achieve a selective enrichment in the peripheral regions of popliteal lymph nodes that contain high concentrations of CD169 expressing antigen presenting cells.

RIP-B7.1 mice express the costimulator molecule B7.1 (CD80) on pancreatic β cells and are a well-established model for studying de novo induction of diabetogenic CD8 T cells. Immunization of RIP-B7.1 mice with preproinsulin (ppins)-encoding plasmid DNA efficiently induces experimental autoimmune diabetes (EAD). EAD is associated with an influx of CD8 T cells specific for the Kb/A12–21 epitope into the pancreatic islets and the subsequent destruction of β cells. In this study, we used this model to investigate how ppins-derived Ags are expressed and processed to prime diabetogenic, Kb/A12–21-specific CD8 T cells. Targeting the Kb/A12–21 epitope, the insulin A chain, or the ppins to the endoplasmic reticulum (ER) (but not to the cytosol and/or nucleus) efficiently elicited Kb/A12–21-specific CD8 T cell responses. The Kb/A12–21 epitope represents the COOH terminus of the ppins molecule and, hence, did not require COOH-terminal processing before binding its restriction element in the ER. However, Kb/A12–21-specific CD8 T cells were also induced by COOH-terminally extended ppins-specific polypeptides expressed in the ER, indicating that the epitope position at the COOH terminus is less important for its diabetogenicity than is targeting the Ag to the ER. The Kb/A12–21 epitope had a low avidity for Kb molecules. When epitopes of unrelated Ags were coprimed at the same site of Ag delivery, “strong” Kb-restricted (but not Db-restricted) CD8 T cell responses led to the suppression of Kb/A12–21-specific CD8 T cell priming and reduced EAD. Thus, direct expression and processing of the “weak” Kb/A12–21 epitope in the ER favor priming of autoreactive CD8 T cells.

Vaccines are critical in the fight against infectious diseases, and immune-stimulating adjuvants are essential for enhancing vaccine efficacy. However, the precise mechanisms of action of most adjuvants are unknown. There is an urgent need for customized and adjuvant formulated vaccines against immune evading pathogens that remain a risk today. Understanding the specific role of various cell types in adjuvant-induced protective immune responses is vital for an effective vaccine design. We have investigated the role of cell-specific MyD88 signaling in vaccine adjuvant activity in vivo, using Neisserial porin B (PorB), a TLR2 ligand-based adjuvant, compared with an endosomal TLR9 ligand (CpG) and toll-like receptor (TLR)-independent (alum, MF59) adjuvants. We found that intact MyD88 signaling is essential, separately, in all three antigen-presenting cell types [B cells, macrophages, and dendritic cells (DCs)] for optimal TLR ligand-based adjuvant activity. The role of MyD88 signaling in B cell and DC in vaccine adjuvant has been previously investigated. In this study, we now demonstrate that the immune response was also reduced in mice with macrophage-specific MyD88 deletion (Mac-MyD88−/−). We demonstrate that TLR-dependent adjuvants are potent inducers of germinal center (GC) responses, but GCs are nearly absent in Mac-MyD88−/− mice following immunization with TLR-dependent adjuvants PorB or CpG, but not with TLR-independent adjuvants MF59 or alum. Our findings reveal a unique and here-to-for unrecognized importance of intact MyD88 signaling in macrophages, to allow for a robust vaccine-induced immune responses when TLR ligand-based adjuvants are used.

TOLL-like receptor (TLR) ligands activate both innate and adaptive immune cells, while modulating the cellular immune response. The outer membrane protein (OMP) from Neisseria meninigitidis, PorB, is a naturally occurring TLR2 ligand and functions as an adjuvant. Here, we demonstrate that PorB increases the level of OVA in the endo-/lysosomal cellular compartment of BMDCs, increases antigen presenting cell (APC) trafficking to draining lymph nodes, and enhances antigen cross-presentation. PorB is capable of mounting an antigen specific T cell response by efficiently stimulating antigen cross-presentation in vivo and in vitro assessed by BMDC OT-I cocultivation assays. The enhanced antigen cross-presentation and the increased APC recruitment to secondary lymphoid tissues expand the scope of known adjuvant effects of PorB on the immune system. Our findings lead to a better understanding of how TLR-ligand based adjuvants can alter and modulate immune responses.

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