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Background: Neoadjuvant ipilimumab plus nivolumab has yielded high response rates in patients with macroscopic stage III melanoma. These response rates translated to high short-term survival rates. However, data on long-term survival and disease recurrence are lacking., Patients and Methods: In OpACIN, 20 patients with macroscopic stage III melanoma were randomized to ipilimumab 3 mg/kg plus nivolumab 1 mg/kg q3w four cycles of adjuvant or split two cycles of neoadjuvant and two adjuvant. In OpACIN-neo, 86 patients with macroscopic stage III melanoma were randomized to arm A (2× ipilimumab 3 mg/kg plus nivolumab 1 mg/kg q3w; n = 30), arm B (2× ipilimumab 1 mg/kg plus nivolumab 3 mg/kg q3w; n = 30), or arm C (2× ipilimumab 3 mg/kg q3w plus 2× nivolumab 3 mg/kg q2w; n = 26) followed by surgery., Results: The median recurrence-free survival (RFS) and overall survival (OS) were not reached in either trial. After a median follow-up of 69 months for OpACIN, 1/7 patients with a pathologic response to neoadjuvant therapy had disease recurrence. The estimated 5-year RFS and OS rates for the neoadjuvant arm were 70% and 90% versus 60% and 70% for the adjuvant arm. After a median follow-up of 47 months for OpACIN-neo, the estimated 3-year RFS and OS rates were 82% and 92%, respectively. The estimated 3-year RFS rate for OpACIN-neo was 95% for patients with a pathologic response versus 37% for patients without a pathologic response (P < 0.001). In multiple regression analyses, pathologic response was the strongest predictor of disease recurrence. Of the 12 patients with distant disease recurrence after neoadjuvant therapy, 5 responded to subsequent anti-PD-1 and 8 to targeted therapy, although 7 patients showed progression after the initial response., Conclusions: Updated data confirm the high survival rates after neoadjuvant combination checkpoint inhibition in macroscopic stage III melanoma, especially for patients with a pathologic response. Pathologic response is the strongest surrogate marker for long-term outcome., Competing Interests: Disclosure AMM reports an advisory role for Bristol-Myers Squibb, MSD Oncology, Novartis, Pierre Fabre, QBiotics, and Roche. RPMS reports an advisory role for Merck Sharpe & Dohme, Novartis, and QBiotics; and was a speaker for Bristol-Myers Squibb. WJvH reports an advisory role for Amgen, Bristol-Myers Squibb, and Sanofi. BAvdW reports employment with Bristol-Myers Squibb. RAS reports an advisory role for Amgen, Bristol-Myers Squibb, Evaxion Biotech, GlaxoSmithKline, Merck Sharp & Dohme, Myriad Genetics, NeraCare GmbH, Novartis Australia, Novartis, Provectus Biopharmaceuticals Australia, QBiotics, and Roche; has received compensation for travel expenses from Bristol-Myers Squibb and Novartis Australia; has received honoraria from GlaxoSmithKline, Harvard Medical School, and Wake Forest School of Medicine; and has received research funding from the Australian National Health and Medical Research Council. JBAGH reports an advisory role for Achilles Therapeutics, BioNTech, Bristol-Myers Squibb, Immunocore, Instil Bio, Iovance Biotherapeutics, Ipsen, Molecular Partners, MSD Oncology, Neogene Therapeutics, Novartis, PokeAcell, Roche/Genentech, Sanofi, Third Rock Ventures, and T-Knife; has received research funding, paid to the institute, from Amgen, Asher Biotherapeutics, BioNTech, Bristol-Myers Squibb, MSD, Neon Therapeutics, and Novartis; and is stockowner of Neogene Therapeutics. TNS reports an advisory role for Allogene Therapeutics, Asher Bio, Celsius, Merus, Neogene Therapeutics, Scenic Biotech, and Third Rock Ventures; and is stockowner of Allogene Therapeutics, Asher Bio, Celsius, Merus, Neogene Therapeutics, Scenic Biotech, and Third Rock Ventures. ACJvA reports an advisory role for 4SC, Bristol-Myers Squibb, Amgen, Merck/Pfizer, Novartis, MSD Oncology, Pierre Fabre, Provectus, Sanofi, and Sirius Medical; and received research funding, all paid to the institute, from Amgen and Merck/Pfizer. GVL reports an advisory role for Agenus, Amgen, Array BioPharma, AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb, Evaxion Biotech A/S, Hexal, Highlight Therapeutics, Innovent Biologics, Merck Sharp & Dohme, Novartis, OncoSec, PHMR Ltd, Pierre Fabre, Provectus Australia, QBiotics, and Regeneron; and has received honorarium from Bristol-Myers Squibb and Pierre Fabre. CUB reports research funding from Bristol-Myers Squibb, Novartis, and NanoString, all paid to the institute; has an advisory role for Bristol-Myers Squibb, MSD Oncology, Roche/Genentech, Novartis, GlaxoSmithKline, AstraZeneca, Pfizer, Lilly, Genmab, Pierre Fabre, and Third Rock Ventures; and is stockowner of Uniti Cars and Immagene. All other authors have declared no conflicts of interest., (Copyright © 2023 European Society for Medical Oncology. Published by Elsevier Ltd. All rights reserved.)

Therapeutic efficacy of a tumor cell-based vaccine against experimental B16 melanoma requires the disruption of either of two immunoregulatory mechanisms that control autoreactive T cell responses: the cytotoxic T lymphocyte-associated antigen (CTLA)-4 pathway or the CD25(+) regulatory T (Treg) cells. Combination of CTLA-4 blockade and depletion of CD25(+) Treg cells results in maximal tumor rejection. Efficacy of the antitumor therapy correlates with the extent of autoimmune skin depigmentation as well as with the frequency of tyrosinase-related protein 2(180-188)-specific CTLs detected in the periphery. Furthermore, tumor rejection is dependent on the CD8(+) T cell subset. Our data demonstrate that the CTL response against melanoma antigens is an important component of the therapeutic antitumor response and that the reactivity of these CTLs can be augmented through interference with immunoregulatory mechanisms. The synergism in the effects of CTLA-4 blockade and depletion of CD25(+) Treg cells indicates that CD25(+) Treg cells and CTLA-4 signaling represent two alternative pathways for suppression of autoreactive T cell immunity. Simultaneous intervention with both regulatory mechanisms is therefore a promising concept for the induction of therapeutic antitumor immunity.

Dendritic cells (DCs) play a central role in the immune system as they drive activation of T lymphocytes by cognate interactions. However, as DCs express high levels of major histocompatibility complex class I, this intimate contact may also result in elimination of DCs by activated cytotoxic T lymphocytes (CTLs) and thereby limit induction of immunity. We show here that immature DCs are indeed susceptible to CTL-induced killing, but become resistant upon maturation with anti-CD40 or lipopolysaccharide. Protection is achieved by expression of serine protease inhibitor (SPI)-6, a member of the serpin family that specifically inactivates granzyme B and thereby blocks CTL-induced apoptosis. Anti-CD40 and LPS-induced SPI-6 expression is sustained for long periods of time, suggesting a role for SPI-6 in the longevity of DCs. Importantly, T helper 1 cells, which mature DCs and boost CTL immunity, induce SPI-6 expression and subsequent DC resistance. In contrast, T helper 2 cells neither induce SPI-6 nor convey protection, despite the fact that they trigger DC maturation with comparable efficiency. Our data identify SPI-6 as a novel marker for DC function, which protects DCs against CTL-induced apoptosis.

During immunosuppression, cytomegalovirus (CMV) can reactivate and cause serious clinical problems. Normally, abundant virus replication is suppressed by immune effector mechanisms. To study the interaction between CD8(+) T cells and persisting viruses, frequencies and phenotypes of CMV-specific CD8(+) T cells were determined in healthy individuals and compared to those in renal transplant recipients. In healthy donors, function of circulating virus-specific CD8(+) T cells, as measured by peptide-induced interferon gamma (IFN-gamma) production, but not the number of virus-specific T cells enumerated by binding of specific tetrameric peptide/HLA complexes, correlated with the number of CMV-specific IFN-gamma-secreting CD4(+) helper T cells. Circulating CMV- specific CD8(+) T cells did not express CCR7 and may therefore not be able to recirculate through peripheral lymph nodes. Based on coexpression of CD27 and CD45R0 most CMV-specific T cells in healthy donors appeared to be memory-type cells. Remarkably, frequencies of CMV-specific CD8(+) T cells were significantly higher in immunosuppressed individuals than in healthy donors. In these patients CMV-specific cells predominantly had an effector phenotype, that is, CD45R0(+)CD27(-)CCR7(-) or CD45RA(+)CD27(-)CCR7(-) and contained both granzyme B and perforin. Our data show that in response to immunosuppressive medication quantitative and qualitative changes occur in the CD8(+) T-cell compartment. These adaptations may be instrumental to maintain CMV latency. (Blood. 2001;98:754-761)

The diversity of the T cell receptor (TCR) repertoire is limited, because of the processes of positive and negative T cell selection. To obtain T cells with specificities beyond the immune system's capacity, we have developed a strategy for retroviral TCR display. In this approach, a library of T cell variants is generated in vitro and introduced into a TCR-negative murine T cell line by retroviral transfer. We document the value of TCR display by the creation of a library of an influenza A-specific TCR and the subsequent in vitro selection of TCRs that either recognize the parental influenza epitope or that have acquired a specificity for a different influenza A strain. The resulting in vitro selected TCRs induce efficient T cell activation after ligand recognition and are of equal or higher potency than the in vivo generated parent receptor. TCR display should prove a useful strategy for the generation of high-affinity tumor-specific TCRs for gene transfer purposes.

The enormous diversity of the T cell pool makes it difficult to determine whether inherent biases in the naive TCR repertoire can influence T cell responsiveness. In C57BL/6 mice the cytotoxic T lymphocyte response to an immunodominant HSV-1 determinant (gB) is characterized by a prominent bias in Vbeta element usage, associated with a conserved and preferentially D element-encoded CDR3 sequence. Comparison of naive and gB-specific T cell populations revealed a similar enrichment of germline D element-encoded CDR3 sequences in the preimmune repertoire. Strikingly, eliminating the germline coding of the gB-specific CDR3 sequence caused an almost complete loss of the dominant subset of gB-specific T cells, illustrating that CDR3 biases can significantly alter both the composition and strength of an immune response.

The role of memory T cells during the immune response against random antigenic variants has not been resolved. Here, we show by simultaneous staining with two tetrameric major histocompatibility complex (MHC)-peptide molecules, that the polyclonal CD8(+) T cell response against a series of natural variants of the influenza A nucleoprotein epitope is completely dominated by infrequent cross-reactive T cells that expand from an original memory population. Based on both biochemical and functional criteria, these cross-reactive cytotoxic T cells productively recognize both the parental and the mutant epitope in vitro and in vivo. These results provide direct evidence that the repertoire of antigen-specific T cells used during an infection critically depends on prior antigen encounters, and indicate that polyclonal memory T cell populations can provide protection against a range of antigenic variants.

The outcome of antigen recognition by naive CD8+ cytotoxic T lymphocytes (CTLs) in the periphery is orchestrated by CD4+ T-helper cells, and can either lead to priming or tolerization. The presence of T-helper cells favors the induction of CTL immunity, whereas the absence of T-helper cells can result in CTL tolerance. The action of T helper cells in CTL priming is mediated by CD40-CD40 ligand interactions. We demonstrate here that triggering of CD40 in vivo can considerably enhance the efficacy of peptide-based anti-tumor vaccines. The combination of a tolerogenic peptide vaccine containing a minimal essential CTL epitope with an activating antibody against CD40 converts tolerization into strong CTL priming. Moreover, CD40 ligation can provide an already protective tumor-specific peptide vaccine with the capacity to induce therapeutic CTL immunity in tumor-bearing mice. These findings indicate that the CD40-CD40 ligand pair can act as a 'switch', determining whether naive peripheral CTLs are primed or tolerized, and support the clinical use of CD40-stimulating agents as components of anti-cancer vaccines.

In vitro selection experiments have produced nucleic acid ligands (aptamers) that bind tightly and specifically to a great variety of target biomolecules. The utility of aptamers is often limited by their vulnerability to nucleases present in biological materials. One way to circumvent this problem is to select an aptamer that binds the enantiomer of the target, then synthesize the enantiomer of the aptamer as a nuclease-insensitive ligand of the normal target. We have so identified a mirror-image single-stranded DNA that binds the peptide hormone vasopressin and have demonstrated its stability to nucleases and its bioactivity as a vasopressin antagonist in cell culture.

Genetically encoded libraries of peptides and oligonucleotides are well suited for the identification of ligands for many macromolecules. A major drawback of these techniques is that the resultant ligands are subject to degradation by naturally occurring enzymes. Here, a method is described that uses a biologically encoded library for the identification of D-peptide ligands, which should be resistant to proteolytic degradation. In this approach, a protein is synthesized in the D-amino acid configuration and used to select peptides from a phage display library expressing random L-amino acid peptides. For reasons of symmetry, the mirror images of these phage-displayed peptides interact with the target protein of the natural handedness. The value of this approach was demonstrated by the identification of a cyclic D-peptide that interacts with the Src homology 3 domain of c- SRC. Nuclear magnetic resonance studies indicate that the binding site for this D-peptide partially overlaps the site for the physiological ligands of this domain.

Major histocompatibility complex (MHC) class I molecules associate with peptides that are delivered from the cytosol to the lumen of the endoplasmic reticulum by the transporter associated with antigen processing (TAP). Liver microsomes of SHR and Lewis rats, which express different alleles of TAP (cim(b) and cim(a), respectively), accumulate different sets of peptides. Use of MHC congenic rats assigned this difference to the MHC, independent of the class I products expressed. Both the cim(a) and cim(b) TAP complexes translocate peptides with a hydrophobic carboxyl terminus, but translocation of peptides with a carboxyl-terminal His, Lys, or Arg residue is unique to cim(a). Thus, the specificity of the TAP peptide translocator restricts the peptides available for antigen presentation.

Synthetic peptides have been used to sensitize target cells and thereby screen for epitopes recognized by T cells. Most epitopes of cytotoxic T lymphocytes can be mimicked by synthetic peptides of 12-15 amino acids. Although in specific cases, truncations of peptides improves sensitization of target cells, no optimum length for binding to major histocompatibility complex (MHC) class I molecules has been defined. We have now analysed synthetic peptide captured by empty MHC class I molecules of the mutant cell line RMA-S. We found that class I molecules preferentially bound short peptides (nine amino acids) and selectively bound these peptides even when they were a minor component in a mixture of longer peptides. These results may help to explain the difference in size restriction of T-cell epitopes between experiments with synthetic peptides and those with naturally processed peptides.

Major histocompatibility complex (MHC) class I molecules present antigen by transporting peptides from intracellularly degraded proteins to the cell surface for scrutiny by cytotoxic T cells. Recent work suggests that peptide binding may be required for efficient assembly and intracellular transport of MHC class I molecules, but it is not clear whether class I molecules can ever assemble in the absence of peptide. We report here that culture of the murine lymphoma mutant cell line RMA-S at reduced temperature (19-33 degrees C) promotes assembly, and results in a high level of cell surface expression of H-2/beta 2-microglobulin complexes that do not present endogenous antigens, and are labile at 37 degrees C. They can be stabilized at 37 degrees C by exposure to specific peptides known to interact with H-2Kb or Db. Our findings suggest that, in the absence of peptides, class I molecules can assemble but are unstable at body temperature. The induction of such molecules at reduced temperature opens new ways to analyse the nature of MHC class I peptide interactions at the cell surface.