Breast cancer is a tumor entity that is one of the leading causes of mortality among women worldwide. Although numerous treatment options are available, current explorations of personalized vaccines have shown potential as promising new treatment options to prevent the recurrence of cancer. Here we present a small proof of concept study using a prophylactic peptide vaccination approach in four female breast cancer patients who achieved remission after standard treatment. The patients were initially analyzed for somatic tumor mutations and then treated with personalized neoantigen-derived peptide vaccines. These vaccines consisted of HLA class I and class II peptides and were administered intracutaneously followed by subcutaneous application of sargramostim and/or topical imiquimod as an immunological adjuvant. After an initial priming phase of four vaccinations within two weeks, patients received monthly boosting/maintenance vaccinations. Chemotherapy or checkpoint inhibition was not performed during vaccination. One patient received hormone therapy. The vaccines were well tolerated with no serious adverse events. All patients displayed vaccine-induced CD4+ and/or CD8+ T-cell responses against various neoantigens. Furthermore, all patients remained tumor-free and had persistent T-cell responses, even several months after the last vaccination, suggesting the potential of peptide vaccines as an immunosurveillance and long term prophylaxis option.

Isocitrate dehydrogenase (IDH) mutant glioma is a malignant primary brain tumor diagnosed in adults. In recent years, there has been significant progress in understanding the molecular pathogenesis and biology of these tumors. The first targeted IDH-inhibitor was approved by the US Food and Drug Administration in August 2024 for grade 2 gliomas, in light of results of a phase III trial which showed significant advantages in progression-free survival. However, biologic therapy is not curative, and subsequent treatment options offer only limited clinical benefit and often result in long-term toxicities. In addition, targeted treatment options for grade 3 and grade 4 IDH-mutant gliomas are still missing. In this study, we present n=52 patients with glioma (grade 2, 3 and 4) with confirmed IDH1 mutation (mutIDH1) in the newly diagnosed and recurrent setting who, in addition to standard-of-care, received a personalized neoantigen-targeting peptide vaccine. Each tumor was initially analyzed for somatic mutations by whole exome sequencing, and a peptide vaccine containing potential neoepitopes was designed, manufactured and vaccinated. Each vaccine consisted of peptides derived from numerous somatic mutations, including at least one peptide targeting the mutIDH1. Vaccine immunogenicity was determined by intracellular cytokine staining and simultaneous measurement of four T-cell activation markers (Interferon-γ, Tumor Necrosis Factor, Interleukin-2, CD154) after 12-day in vitro expansion of pre and post vaccination peripheral blood mononuclear cells. Extracellular CD154 staining was used to sort mutIDH1-specific CD4+T cells. Immunomonitoring revealed that the vaccines were immunogenic and induced mainly CD4 but also CD8 T cell responses. Vaccine-induced immune responses were robust and polyfunctional. Immunogenicity against mutIDH1 was high (89%). We implemented an assay which allowed us to isolate functional antigen-specific CD4+T cells in an HLA-independent manner. Subsequent T cell receptor (TCR) repertoire sequencing revealed that CD4+T cells reacting on mutIDH1 stimulation were polyclonal. Strikingly, we detected two mutIDH1-specific TCRβ candidate sequences in three different patients. These three patients had the same human leukocyte antigen (HLA) DQA-DQB alleles. The obtained TCRβ sequences could be tracked in autologous ex-vivo single-cell transcriptomic data. Our results provide a rationale for pursuing vaccination and T cell transfer strategies targeting IDH1. Furthermore, our findings indicate that personalized neoantigen-targeting vaccines might be considered for the treatment of IDH1-mutant gliomas.

Ovarian cancer is one of the most common cancers among women and the most lethal malignancy of all gynecological cancers. Surgery is promising in the early stages; however, most patients are first diagnosed in the advanced stages, where treatment options are limited. Here, we present a 49-year-old patient who was first diagnosed with stage III ovarian cancer. After the tumor progressed several times under guideline therapies with no more treatment options available at that time, the patient received a fully individualized neoantigen-derived peptide vaccine in the setting of an individual healing attempt. The tumor was analyzed for somatic mutations via whole exome sequencing and potential neoepitopes were vaccinated over a period of 50 months. During vaccination, the patient additionally received anti-PD-1 therapy to prevent further disease progression. Vaccine-induced T-cell responses were detected using intracellular cytokine staining. After eleven days of in vitro expansion, four T-cell activation markers (namely IFN-ɣ, TNF-α, IL-2, and CD154) were measured. The proliferation capacity of neoantigen-specific T-cells was determined using a CFSE proliferation assay. Immune monitoring revealed a very strong CD4+ T-cell response against one of the vaccinated peptides. The vaccine-induced T-cells simultaneously expressed CD154, TNF, IL-2, and IFN-ɣ and showed a strong proliferation capacity upon neoantigen stimulation. Next-generation sequencing, as well as immunohistochemical analysis, revealed a loss of Beta-2 microglobulin (B2M), which is essential for MHC class I presentation. The results presented here implicate that the application of neoantigen-derived peptide vaccines might be considered for those cancer stages, where promising therapeutic options are lacking. Furthermore, we provide more data that endorse the intensive investigation of B2M loss as a tumor escape mechanism in clinical trials using anti-cancer vaccines together with immune-checkpoint inhibitors.

Background/Objectives: Fully personalized peptide vaccines targeting tumor-specific mutations are a promising treatment option for patients in an adjuvant but also advanced/metastatic disease situation in addition to non-personalized standard therapies. Here, we report a patient’s case with advanced metastatic colorectal cancer (mCRC) who was treated with a neoantigen-derived multi-peptide vaccine in addition to standard of care. Methods: Tumor-specific mutations were identified by whole exome and transcriptome sequencing. An individualized peptide vaccine was designed using an in-house developed epitope prediction and vaccine design platform. In this case, the vaccine consisted of 20 peptides targeting 18 distinct mutations. The vaccine was administered according to a prime-boost scheme for a total of 12 vaccinations. Vaccine immunogenicity was determined by stimulation of patient T cells with vaccinated peptides and subsequent intracellular cytokine staining (ICS). Tumor-infiltrating lymphocytes (TIL) were analyzed by ICS and T cell receptor beta chain (TCRβ) sequencing. Results: The patient survived for 41 months since initial diagnosis despite continuous disease progression under all therapeutic interventions. The vaccination induced multiple neoantigen-specific T cell responses in the patient without notable side effects. Two liver metastases were resected five months after the start of vaccination, and TIL were extracted and cultured. Analysis of TIL cultures revealed tumor infiltration by vaccine-induced neoantigen-specific T cells in only one of the metastases. TCRβ sequencing of neoantigen-specific T cells and tumor tissues supported this finding. Vaccine-targeted variants were reduced or absent in the metastasis with vaccine-specific T cell infiltration. Conclusions: This case demonstrates immunogenicity of a neoantigen-derived peptide vaccine and highlights tumor-infiltrating capabilities and potential cytotoxicity of vaccine-induced T cells in mCRC.

The pivotal role of the cell entry receptor ACE2 for SARS‐CoV‐2 infection is well‐established. When ACE2 is shed from cell surface into plasma as soluble ACE2 (sACE2), it can effectively neutralize SARS‐CoV‐2. This longitudinal prospective cohort study analyzed sACE2 activity in 1192 participants, aged 4 months to 81 years, 3 and 12 months after SARS‐CoV‐2 household exposure. Following SARS‐CoV‐2 exposure, participants exhibited significantly elevated sACE2 activity, irrespective of confirmed infection, with the highest levels observed in exposed children. Longitudinal analysis revealed a decline in sACE2 levels over time, reaching levels comparable to age‐ and sex‐matched pre‐pandemic controls. An increase in sACE2 activity was also confirmed in vitro in Calu‐3 (human lung) cells within hours of SARS‐CoV‐2 exposure, providing a direct link between SARS‐CoV‐2 exposure and elevated sACE2. This study, therefore, challenges the dichotomy of categorizing SARS‐CoV‐2 exposed participants as infected or not infected solely on currently established diagnostic assays. It demonstrates lasting host responses independent of B‐ and T‐cell memory and may help to keep SARS‐CoV‐2 infections in balance and contribute to successful virus clearance in children and adults lacking humoral and cellular immune responses following SARS‐CoV‐2 exposure.Trial Registration: German Registry for Clinical Studies; Identifier: D 00021521.

Anti–T lymphocyte globulin (ATLG) significantly reduces the risk of engraftment failure in allogeneic hematopoietic stem cell transplant (HSCT) but hampers posttransplant immune reconstitution. We hypothesized that in patients receiving haploidentical CD3/CD19-depleted grafts, these double-edged effects could be better balanced by attaining high ATLG serum concentrations before transplant but as low as possible on the day of transplant. Therefore, we moved the start of ATLG application to day −12 and determined serum concentrations of T-cell–specific ATLG in pediatric patients treated with 3 established dosing regimens (15, 30, or 60 mg/kg). Corresponding mean T-cell–specific ATLG serum concentrations at day 0 were 1.14, 2.99, or 12.10 μg/mL, respectively. Higher ATLG doses correlated with higher peak levels at days −8 and −7 and reduced graft rejection, whereas lower ATLG doses correlated with significantly faster posttransplant recovery of T and natural killer cells. The rate of graft-versus-host disease remained low, independent of ATLG doses. Moreover, in vitro assays showed that ATLG concentrations of 2.0 μg/mL and lower only slightly reduced the activity of natural killer cells, and therefore, the function of such effector cells might be preserved in the grafts. Pharmacokinetic analysis, compatible with linear first-order kinetics, revealed similar half-life values, independent of ATLG doses. Hence, the day on which a desired ATLG serum level is reached can be calculated before HSCT. Our retrospective study demonstrates the relevance of dosing and time of administration of ATLG on engraftment and immune recovery in ex vivo CD3/CD19-depleted haploidentical HSCT.