An engineering strategy to target activated EGFR with CAR T cells.

Chimeric antigen receptor (CAR) T cells have shown remarkable response rates in hematological malignancies. In contrast, CAR T cell treatment of solid tumors is associated with several challenges, in particular the expression of most tumor-associated antigens at lower levels in vital organs, resulting in on-target/off-tumor toxicities. Thus, innovative approaches to improve the tumor specificity of CAR T cells are urgently needed. Based on the observation that many human solid tumors activate epidermal growth factor receptor (EGFR) on their surface through secretion of EGFR ligands, we developed an engineering strategy for CAR-binding domains specifically directed against the ligand-activated conformation of EGFR. We show, in several experimental systems, that the generated binding domains indeed enable CAR T cells to distinguish between active and inactive EGFR. We anticipate that this engineering concept will be an important step forward to improve the tumor specificity of CAR T cells directed against EGFR-positive solid cancers.

Modulation of immune responses to liposomal vaccines by intrastructural help.

The encapsulation of HIV-unrelated T helper peptides into liposomal vaccines presenting trimers of the HIV-1 envelope glycoprotein (Env) on the surface (T helper liposomes) may recruit heterologous T cells to provide help for Env-specific B cells. This mechanism called intrastructural help can modulate the HIV-specific humoral immune response. In this study, we used cationic T helper liposomes to induce intrastructural help effects in a small animal model. The liposomes were functionalized with Env trimers by a tag-free approach designed to enable a simplified GMP production. The pre-fusion conformation of the conjugated Env trimers was verified by immunogold electron microscopy (EM) imaging and flow cytometry. The liposomes induced strong activation of Env-specific B cells in vitro. In comparison to previously established anionic liposomes, cationic T helper liposomes were superior in CD4+ T cell activation after uptake by dendritic cells. Moreover, the T helper liposomes were able to target Env-specific B cells in secondary lymphoid organs after intramuscular injection. We also observed efficient T helper cell activation and proliferation in co-cultures with Env-specific B cells in the presence of cationic T helper liposomes. Mouse immunization experiments with cationic T helper liposomes further revealed a modulation of the Env-specific IgG subtype distribution and enhancement of the longevity of antibody responses by ovalbumin- and Hepatitis B (HBV)-specific T cell help. Thus, clinical evaluation of the concept of intrastructural help seems warranted.

Conjugation of Native-Like HIV-1 Envelope Trimers onto Liposomes Using EDC/Sulfo-NHS Chemistry: Requirements and Limitations.

The display of native-like human immunodeficiency virus type 1 envelope (HIV-1 Env) trimers on liposomes has gained wide attention over the last few years. Currently, available methods have enabled the preparation of Env-liposome conjugates of unprecedented quality. However, these protocols require the Env trimer to be tagged and/or to carry a specific functional group. For this reason, we have investigated N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide/N-Hydroxysulfosuccinimide (EDC/Sulfo-NHS) chemistry for its potential to covalently conjugate tag-free, non-functionalized native-like Env trimers onto the surface of carboxyl-functionalized liposomes. The preservation of the liposome's physical integrity and the immunogen's conformation required a fine-tuned two-step approach based on the controlled use of ß-mercaptoethanol. The display of Env trimers was strictly limited to activated liposomes of positive charge, i.e., liposomes with a positive zeta potential that carry amine-reactive Sulfo-NHS esters on their surface. In agreement with that, conjugation was found to be highly ionic strength- and pH-dependent. Overall, we have identified electrostatic pre-concentration (i.e., close proximity between negatively charged Env trimers and positively charged liposomes established through electrostatic attraction) to be crucial for conjugation reactions to proceed. The present study highlights the requirements and limitations of potentially scalable EDC/Sulfo-NHS-based approaches and represents a solid basis for further research into the controlled conjugation of tag-free, non-functionalized native-like Env trimers on the surface of liposomes, and other nanoparticles.

Crossing borders to facilitate live donor kidney transplantation: the Czech-Austrian kidney paired donation program - a retrospective study.

Kidney paired donation (KPD) is a valuable tool to overcome immunological barriers in living donor transplantation. While small national registries encounter difficulties in finding compatible matches, multi-national KPD may be a useful strategy to facilitate transplantation. The Czech (Prague) and Austrian (Vienna) KPD programs, both initiated in 2011, were merged in 2015. A bi-national algorithm allowed for ABO- and low-level HLA antibody-incompatible exchanges, including the option of altruistic donor-initiated domino chains. Between 2011 and 2019, 222 recipients and their incompatible donors were registered. Of those, 95.7% (Prague) and 67.9% (Vienna) entered into KPD registries, and 81 patients received a transplant (95% 3-year graft survival). Inclusion of ABO-incompatible pairs in the Czech program contributed to higher KPD transplant rates (42.6% vs. 23.6% in Austria). After 2015 (11 bi-national match runs), the median pool size increased to 18 pairs, yielding 33 transplants (8 via cross-border exchanges). While matching rates doubled in Austria (from 9.1% to 18.8%), rates decreased in the Czech program, partly due to implementation of more stringent HLA antibody thresholds. Our results demonstrate the feasibility of merging small national KPD programs to increase pool sizes and may encourage the implementation of multi-national registries to expand the full potential of KPD.

Extracorporeal photopheresis as second-line therapy for patients with acute graft-versus-host disease: does the number of cells treated matter?

BACKGROUND: Extracorporeal photopheresis (ECP) has demonstrated efficacy as second-line treatment for steroid-refractory (SR) acute graft-versus-host disease (aGVHD). The aim of our study was to analyze whether the amount of ECP-treated cells in patients with SR, aGVHD has an impact on response at 1 month. STUDY DESIGN AND METHODS: Data on white blood cells, lymphocytes, monocytes, mononuclear cells, and neutrophils, including absolute counts and counts per kilogram of body weight in ECP products from patients with aGVHD, were collected. For each cell population, the median dose per single ECP and the cumulative doses collected during the first week and the first month of treatment were compared with the response to ECP. RESULTS: In total, 99 patients underwent 1215 ECP procedures. Overall response was defined as a complete response if all signs of aGVHD resolved or a partial response if greater than 50% resolution was reached without other, additional immunosuppression. An overall response was obtained by 75% of patients, including 53% complete responses. Univariate analysis showed a correlation of lymphocytes and mononuclear cells/kg body weight for a single procedure and overall response. In logistic regression analysis, no tested variable had an influence on response. In receiver operating characteristic curve analysis, cutoffs of 8.4 × 106 /kg body weight lymphocytes and 13.9 × 106 /kg body weight mononuclear cells were associated with an overall response to ECP at 1 month with 75% sensitivity. CONCLUSION: Our results in patients with steroid-refractory aGVHD confirm that response rates to ECP are high and that certain cutoff values for lymphocytes and mononuclear cells/kg body weight in each individual procedure can predict an overall response to ECP at 1 month.