Valentin Voillet

T cell correlates of COVID-19 risk are poorly defined, particularly in people with HIV (PWH). CoVPN 3008 (NCT05168813) Part A was a prospective 14,002-participant cohort study that administered one or two doses of mRNA-1273 COVID-19 vaccine, depending on baseline SARS-CoV-2 serostatus, in participants (83% PWH) in sub-Saharan Africa. Participants self-monitored for prespecified COVID-19 symptoms, defined by Centers for Disease Control and Prevention symptom criteria. Previous work showed that protection from COVID-19 was superior for hybrid versus vaccine-induced immunity, and that neutralizing antibody titers inversely associated with COVID-19 risk. In the present work, we measured T cell responses to Spike and Nucleocapsid at baseline and 4 weeks post last-vaccination (Peak) in a case-cohort study and assessed them as correlates of risk. In Hybrid Group PWH (n = 22 cases), COVID-19 risk over 6 months decreased with increasing Peak Spike BA.4/5-specific CD4 + T cell responses, from 15.8%, 4.7%, and 0% risk at 0.1%, 0.2%, and 0.3% IFN-γ and/or IL-2 response magnitude, respectively. Including baseline Spike-specific neutralizing antibody titer and Peak CD4 + T cell functionality score in the same model increased the association’s strength (overall p < 0.001). Thus, CD4 + T cell responses are an independent correlate of COVID-19 risk among PWH with pre-existing SARS-CoV-2 immunity.

Immune checkpoint inhibitors (ICIs) have transformed Merkel cell carcinoma (MCC) outcomes, but most patients with MCC develop resistance. We identified T cell receptor (TCR) _MCC1 , a highly avid, HLA-A*02:01–restricted TCR targeting the Merkel cell polyomavirus (MCPyV) oncoprotein large-T antigen _15–23 . Seven patients with ICI-refractory metastatic MCPyV ⁺ MCC received TCR _MCC1 -transduced cells (T _TCR-MCC1 cells) after lymphodepleting chemotherapy or HLA-enhancing interventions [radiation or interferon gamma-1b (Actimmune)], with concurrent ICIs (NCT03747484). T _TCR-MCC1 cells trafficked to tumor sites and expressed a gene expression profile compatible with T cell activation, with tumor regression observed in two patients. However, therapeutic activity was limited by HLA class I silencing, a common mechanism of immune escape in MCC. In one patient, delayed tumor regression coincided with endogenous effector immune activation and restoration of MCC HLA expression, implying that robust local responses could reverse HLA silencing. To overcome this barrier, we engineered CD4 and CD8 T _TCR-MCC1 cells to coexpress CD8αβ and a CD200R-CD28 switch receptor, enabling CD4 T cell engagement and T cell costimulation. These modifications enhanced tumor infiltration, increased HLA expression, and improved control of HLA ^low MCC in vivo in mice. These findings support the feasibility of TCR-engineered cell therapy for MCPyV ⁺ MCC and provide a blueprint for overcoming immune evasion via targeted localized enhancement of antigen presentation.

Table S4. Staining panel used for multiplex immunohistochemistry

Table S1. Baseline cytokine levels (prior to lymphodepletion) for UPN-03 and UPN-04.

Figure S1. Cellular composition of the post-treatment tumor biopsy of patient UPN-03. Figure S2. Gating strategy for multiparameter flow cytometry for UPN-03. Figure S3. Gating strategy for multiparameter flow cytometry for UPN-04.

Table S2. Differentially expressed TCR-β CDR3 sequences increased at 3 and/or 35 month timepoints in patient UPN-04

Table S3. Cellular composition of post-infusion timepoints.

Chimeric antigen receptor (CAR) T-cell therapy produces high response rates in refractory B-cell non–Hodgkin lymphoma, but long-term data are minimal to date. In this study, we present long-term follow-up of a pilot trial testing a CD20-targeting third-generation CAR in patients with relapsed B-cell lymphomas following cyclophosphamide-only lymphodepletion. Two of the three patients in the trial, with mantle cell lymphoma and follicular lymphoma, had remissions lasting more than 7 years, though they ultimately relapsed. The absence of B-cell aplasia in both patients suggested a lack of functional CAR T-cell persistence, leading to the hypothesis that endogenous immune responses were responsible for these long-term remissions. Correlative immunologic analyses supported this hypothesis, with evidence of new humoral and cellular antitumor immune responses proximal to clinical response time points. Collectively, our results suggest that CAR T-cell therapy may facilitate epitope spreading and endogenous immune response formation in lymphomas.Significance:Two of three patients treated with CD20-targeted CAR T-cell therapy had long-term remissions, with evidence of endogenous antitumor immune response formation. Further investigation is warranted to develop conditions that promote epitope spreading in lymphomas.

Adoptive transfer of T cells engineered with tumor-specific T cell receptors (TCRs) has shown limited efficacy in solid tumors, hindered by insufficient persistence, tumor trafficking, and dependence on tumor-associated co-stimulatory ligands. In a phase I trial (NCT 04639245) for patients with metastatic MAGE-A1-expressing tumors and adequate organ function; one participant received treatment, which was well-tolerated. In this case and NSG murine models, infusion of CD4/CD8 T cells co-expressing a class-I MAGE-A1-specific TCR and CD8αβ, failed to control tumor progression. To enhance function downstream of TCR signaling, here we investigate the adaptability of TCR components to synthetic modification. Leveraging the obligate co-expression of CD8αβ required for class-I TCR function in CD4 T cells, we identify CD8β as a tractable site for engineering without loss of function. In vitro screening demonstrates incorporation of the CD28 intracellular tail, yielding a CD8/CD28 chimeric co-receptor, most effectively enhances cytokine production, T cell persistence, and tumor control in immunodeficient murine models while preserving stem-like transcriptional features compared to native CD8β. Further rational modification of the CD28 binding motifs improves tumor control in vivo with increased intratumoral accumulation and reduced exhaustion. This benefit also extends to PRAME and WT1-specific TCRs in vitro supporting generalizability.