BACKGROUND. Preclinical experiments have shown that donor blood cells, modified in vitro by an alkylating agent (modified immune cells [MICs]), induced long-term specific immunosuppression against the allogeneic donor. METHODS. In this phase I trial, patients received either 1.5 × 10⁶ MICs per kg BW on day –2 (n = 3, group A), or 1.5 × 10⁸ MICs per kg BW on day –2 (n = 3, group B) or day –7 (n = 4, group C) before living donor kidney transplantation in addition to post-transplantation immunosuppression. The primary outcome measure was the frequency of adverse events (AEs) until day 30 (study phase) with follow-up out to day 360. RESULTS. MIC infusions were extremely well tolerated. During the study phase, 10 treated patients experienced a total of 69 AEs that were unlikely to be related or not related to MIC infusion. No donor-specific human leukocyte antigen Abs or rejection episodes were noted, even though the patients received up to 1.3 × 10¹⁰ donor mononuclear cells before transplantation. Group C patients with low immunosuppression during follow-up showed no in vitro reactivity against stimulatory donor blood cells on day 360, whereas reactivity against third-party cells was still preserved. Frequencies of CD19⁺CD24^hiCD38^hi transitional B lymphocytes (Bregs) increased from a median of 6% before MIC infusion to 20% on day 180, which was 19- and 68-fold higher, respectively, than in 2 independent cohorts of transplanted controls. The majority of Bregs produced the immunosuppressive cytokine IL-10. MIC-treated patients showed the Immune Tolerance Network operational tolerance signature. CONCLUSION. MIC administration was safe and could be a future tool for the targeted induction of tolerogenic Bregs. TRIAL REGISTRATION. EudraCT number: 2014-002086-30; ClinicalTrials.gov identifier: NCT02560220. FUNDING. Federal Ministry for Economic Affairs and Technology, Berlin, Germany, and TolerogenixX GmbH, Heidelberg, Germany.

Infections caused by multidrug-resistant bacteria are a global emerging problem. New antibiotics that rely on innovative modes of action are urgently needed. Ranalexin is a potent antimicrobial peptide (AMP) produced in the skin of the American bullfrog Rana catesbeiana. Despite strong antimicrobial activity against Gram-positive bacteria, ranalexin shows disadvantages such as poor pharmacokinetics. To tackle these problems, a ranalexin derivative consisting exclusively of d-amino acids (named danalexin) was synthesized and compared to the original ranalexin for its antimicrobial potential and its biodistribution properties in a rat model. Danalexin showed improved biodistribution with an extended retention in the organisms of Wistar rats when compared to ranalexin. While ranalexin is rapidly cleared from the body, danalexin is retained primarily in the kidneys. Remarkably, both peptides showed strong antimicrobial activity against Gram-positive bacteria and Gram-negative bacteria of the genus Acinetobacter with minimum inhibitory concentrations (MICs) between 4 and 16 mg/L (1.9–7.6 µM). Moreover, both peptides showed lower antimicrobial activities with MICs ≥32 mg/L (≥15.2 µM) against further Gram-negative bacteria. The preservation of antimicrobial activity proves that the configuration of the amino acids does not affect the anticipated mechanism of action, namely pore formation.

Multidrug-resistant bacteria represent one of the most important health care problems worldwide. While there are numerous drugs available for standard therapy, there are only a few compounds capable of serving as a last resort for severe infections. Therefore, approaches to control multidrug-resistant bacteria must be implemented. Here, a strategy of reactivating the established glycopeptide antibiotic vancomycin by structural modification with polycationic peptides and subsequent fatty acid conjugation to overcome the resistance of multidrug-resistant bacteria was followed. This study especially focuses on the structure–activity relationship, depending on the modification site and fatty acid chain length. The synthesized conjugates showed high antimicrobial potential on vancomycin-resistant enterococci. We were able to demonstrate that the antimicrobial activity of the vancomycin-lipopeptide conjugates depends on the chain length of the attached fatty acid. All conjugates showed good cytocompatibility in vitro and in vivo. Radiolabeling enabled the in vivo determination of pharmacokinetics in Wistar rats by molecular imaging and biodistribution studies. An improved biodistribution profile in comparison to unmodified vancomycin was observed. While vancomycin is rapidly excreted by the kidneys, the most potent conjugate shows a hepatobiliary excretion profile. In conclusion, these results demonstrate the potential of the structural modification of already established antibiotics to provide highly active compounds for tackling multidrug-resistant bacteria.

The increasing number of infections caused by multidrug-resistant bacteria requires an intensified search for new antibiotics. Pep19-4LF is a synthetic antimicrobial peptide (GKKYRRFRWKFKGKLFLFG) that was previously designed with the main focus on high antimicrobial activity. The hydrophobic motif, LFLFG, was found to be essential for antimicrobial activity. However, this motif shows several limitations such as aggregation in biological media, low solubility, and small yields in peptide synthesis. In order to obtain more appropriate peptide characteristics, the hydrophobic motif was replaced with fatty acids. For this purpose, a shortened variant of Pep19-4LF (Pep19-short; GKKYRRFRWKFKGK) was synthesized and covalently linked to saturated fatty acids of different chain lengths. The peptide conjugates were tested with respect to their antibacterial activity by microdilution experiments on different bacterial strains. The length of the fatty acid was found to be directly correlated to the antimicrobial activity up to an ideal chain length (undecanoic acid, C11:0). This conjugate showed high antimicrobial activity in absence of toxicity. Time–kill studies revealed a fast and bactericidal mode of action. Furthermore, the first in vivo experiments of the conjugate in rodents demonstrated pharmacokinetics appropriate for application as a drug. These results clearly indicate that the hydrophobic motif of the peptide can be replaced by a single fatty acid of medium length, simplifying the design of this antimicrobial peptide while retaining high antimicrobial activity in the absence of toxicity.

Our previous studies in rats showed that incubation of monocytic dendritic cells (DCs) with the chemotherapeutic drug mitomycin C (MMC) renders the cells immunosuppressive. Donor-derived MMC–DCs injected into the recipient prior to transplantation prolonged heart allograft survival. Although the generation of DCs is labour-intensive and time-consuming, peripheral blood mononuclear cells (PBMCs) can be easily harvested. In the present study, we analyse under which conditions DCs can be replaced by PBMCs and examine their mode of action. When injected into rats, MMC-incubated donor PBMCs (MICs) strongly prolonged heart allograft survival. Removal of monocytes from PBMCs completely abrogated their suppressive effect, indicating that monocytes are the active cell population. Suppression of rejection was donor-specific. The injected MICs migrated into peripheral lymphoid organs and led to an increased number of regulatory T-cells (Tregs) expressing cluster of differentiation (CD) markers CD4 and CD25 and forkhead box protein 3 (FoxP3). Tolerance could be transferred to syngeneic recipients with blood or spleen cells. Depletion of Tregs from tolerogenic cells abrogated their suppressive effect, arguing for mediation of immunosuppression by CD4⁺CD25⁺FoxP3⁺ Tregs. Donor-derived MICs also prolonged kidney allograft survival in pigs. MICs generated from donor monocytes were applied for the first time in humans in a patient suffering from therapy-resistant rejection of a haploidentical stem cell transplant. We describe, in the present paper, a simple method for in vitro generation of suppressor blood cells for potential use in clinical organ transplantation. Although the case report does not allow us to draw any conclusion about their therapeutic effectiveness, it shows that MICs can be easily generated and applied in humans.

Chimeric antigen receptor T (CAR-T) cells targeting CD19 came into clinical practice for the treatment of B cell lymphoma in 2018. However, patients being treated for B cell lymphoma often suffer from comorbidities such as chronic pain, cardiovascular diseases and arthritis. Thus, these patients frequently receive concomitant medications that include nonsteroidal anti-inflammatory drugs (NSAIDs) like cyclooxygenase (COX) inhibitors. Celecoxib, a selective COX-2 inhibitor, and aspirin, a non-selective COX-1 and COX-2 inhibitor, are being used as anti-inflammatory, analgesic and anti-pyretic drugs. In addition, several studies have also focused on the anti-neoplastic properties of COX-inhibitors. As the influence of COX-inhibitors on CD19.CAR-T cells is still unknown, we investigated the effect of celecoxib and aspirin on the quantity and quality of CD19.CAR-T cells at different concentrations with special regard to cytotoxicity, activation, cytokine release, proliferation and exhaustion. A significant effect on CAR-T cells could be observed for 0.1 mmol/L of celecoxib and for 4 mmol/L of aspirin. At these concentrations, we found that both COX-inhibitors could induce intrinsic apoptosis of CD19.CAR-T cells showing a significant reduction in the ratio of JC-10 red to JC-10 green CAR-T cells from 6.46 ± 7.03 (mean ± SD) to 1.76 ± 0.67 by celecoxib and to 4.41 ± 0.32 by aspirin, respectively. Additionally, the ratios of JC-10 red to JC-10 green Daudi cells were also decreased from 3.41 ± 0.30 to 0.77 ± 0.06 by celecoxib and to 1.26 ± 0.04 by aspirin, respectively. Although the cytokine release by CD19.CAR-T cells upon activation was not hampered by both COX-inhibitors, activation and proliferation of CAR-T cells were significantly inhibited via diminishing the NF-ĸB signaling pathway by a significant down-regulation of expression of CD27 on CD4⁺ and CD8⁺ CAR-T cells, followed by a clear decrease of phosphorylated NF-ĸB p65 in both CD4⁺ and CD8⁺ CAR-T cells by a factor of 1.8. Of note, COX-inhibitors hampered expansion and induced exhaustion of CAR-T cells in an antigen stress assay. Collectively, our findings indicate that the use of COX-inhibitors is a double-edged sword that not only induces apoptosis in tumor cells but also impairs the quantity and quality of CAR-T cells. Therefore, COX-inhibitors should be used with caution in patients with B cell lymphoma under CAR-T cell therapy.