Concurrent immune checkpoint inhibition and selective immunosuppressive therapy in patients with immune-related enterocolitis.

PURPOSE: Immune checkpoint inhibitor (ICI) therapy is often suspended because of immune-related enterocolitis (irEC). We examined the effect of resumption of ICIs with or without concurrent selective immunosuppressive therapy (SIT) on rates of symptom recurrence and survival outcomes. METHODS: This retrospective, multicenter study examined patients who were treated with ICI and developed irEC requiring SIT (infliximab or vedolizumab) for initial symptom control or to facilitate steroid tapering between May 2015 and June 2020. After symptom resolution, patients were restarted either on ICI alone or on concurrent ICI and SIT at the discretion of the treating physicians. The associations between irEC recurrence and treatment group were assessed via univariate analyses and multivariate logistic regression. Cox proportional hazards model was used for survival analysis. RESULTS: Of the 138 included patients who required SIT for initial irEC symptom control, 61 (44.2%) patients resumed ICI without concurrent SIT (control group) and 77 (55.8%) patients resumed ICI therapy with concurrent SIT: 33 with infliximab and 44 with vedolizumab. After symptom resolution, patients in the control group were more commonly restarted on a different ICI regimen (65.6%) compared with those receiving SIT (31.2%) (p<0.001). The total number of ICI doses administered after irEC resolution and ICI resumption was similar in both groups (four to five doses). Recurrence of severe colitis or diarrhea after ICI resumption was seen in 34.4% of controls compared with 20.8% of patients receiving concurrent SIT. Concurrent SIT was associated with reduced risk of severe irEC recurrence after ICI resumption in a multivariate logistic regression model (OR 0.34; 95% CI 0.13 to 0.92; p=0.034). There was no difference in survival outcomes between patients in the control group and patients concurrently treated with SIT. CONCLUSION: After resolution of irEC symptoms, reinitiation of ICI with concurrent SIT is safe, reduces severe irEC recurrence, and has no negative impact on survival outcomes.

Personal neoantigen vaccines induce persistent memory T cell responses and epitope spreading in patients with melanoma.

Personal neoantigen vaccines have been envisioned as an effective approach to induce, amplify and diversify antitumor T cell responses. To define the long-term effects of such a vaccine, we evaluated the clinical outcome and circulating immune responses of eight patients with surgically resected stage IIIB/C or IVM1a/b melanoma, at a median of almost 4 years after treatment with NeoVax, a long-peptide vaccine targeting up to 20 personal neoantigens per patient ( NCT01970358 ). All patients were alive and six were without evidence of active disease. We observed long-term persistence of neoantigen-specific T cell responses following vaccination, with ex vivo detection of neoantigen-specific T cells exhibiting a memory phenotype. We also found diversification of neoantigen-specific T cell clones over time, with emergence of multiple T cell receptor clonotypes exhibiting distinct functional avidities. Furthermore, we detected evidence of tumor infiltration by neoantigen-specific T cell clones after vaccination and epitope spreading, suggesting on-target vaccine-induced tumor cell killing. Personal neoantigen peptide vaccines thus induce T cell responses that persist over years and broaden the spectrum of tumor-specific cytotoxicity in patients with melanoma.

A cloning and expression system to probe T-cell receptor specificity and assess functional avidity to neoantigens.

Recent studies have highlighted the promise of targeting tumor neoantigens to generate potent antitumor immune responses and provide strong motivation for improving our understanding of antigen-T-cell receptor (TCR) interactions. Advances in single-cell sequencing technologies have opened the door for detailed investigation of the TCR repertoire, providing paired information from TCRα and TCRß, which together determine specificity. However, a need remains for efficient methods to assess the specificity of discovered TCRs. We developed a streamlined approach for matching TCR sequences with cognate antigen through on-demand cloning and expression of TCRs and screening against candidate antigens. Here, we first demonstrate the system's capacity to identify viral-antigen-specific TCRs and compare the functional avidity of TCRs specific for a given antigen target. We then apply this system to identify neoantigen-specific TCR sequences from patients with melanoma treated with personalized neoantigen vaccines and characterize functional avidity of neoantigen-specific TCRs. Furthermore, we use a neoantigen-prediction pipeline to show that an insertion-deletion mutation in a putative chronic lymphocytic leukemia (CLL) driver gives rise to an immunogenic neoantigen mut-MGA, and use this approach to identify the mut-MGA-specific TCR sequence. This approach provides a means to identify and express TCRs, and then rapidly assess antigen specificity and functional avidity of a reconstructed TCR, which can be applied for monitoring antigen-specific T-cell responses, and potentially for guiding the design of effective T-cell-based immunotherapies.

HOP-1 Presenilin Deficiency Causes a Late-Onset Notch Signaling Phenotype That Affects Adult Germline Function in Caenorhabditis elegans.

Functionally redundant genes present a puzzle as to their evolutionary preservation, and offer an interesting opportunity for molecular specialization. In Caenorhabditis elegans, either one of two presenilin genes (sel-12 or hop-1) facilitate Notch activation, providing the catalytic subunit for the γ secretase proteolytic enzyme complex. For all known Notch signaling events, sel-12 can mediate Notch activation, so the conservation of hop-1 remains a mystery. Here, we uncover a novel "late-onset" germline Notch phenotype in which HOP-1-deficient worms fail to maintain proliferating germline stem cells during adulthood. Either SEL-12 or HOP-1 presenilin can impart sufficient Notch signaling for the establishment and expansion of the germline, but maintenance of an adult stem cell pool relies exclusively on HOP-1-mediated Notch signaling. We also show that HOP-1 is necessary for maximum fecundity and reproductive span. The low-fecundity phenotype of hop-1 mutants can be phenocopied by switching off glp-1/Notch function during the last stage of larval development. We propose that at the end of larval development, dual presenilin usage switches exclusively to HOP-1, perhaps offering opportunities for differential regulation of the germline during adulthood. Additional defects in oocyte size and production rate in hop-1 and glp-1 mutants indicate that the process of oogenesis is compromised when germline Notch signaling is switched off. We calculate that in wild-type adults, as much as 86% of cells derived from the stem cell pool function to support oogenesis. This work suggests that an important role for Notch signaling in the adult germline is to furnish a large and continuous supply of nurse cells to support the efficiency of oogenesis.