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Polypeptide vaccines effectively activate human T cells but suffer from poor biological stability, which confines both transport logistics and in vivo therapeutic activity. Synthetic biology has the potential to address these limitations through the generation of highly stable antigenic 'mimics' using subunits that do not exist in the natural world. We developed a platform based on D-amino acid combinatorial chemistry and used this platform to reverse engineer a fully artificial [CD8.sup.+] T cell agonist that mirrored the immunogenicity profile of a native epitope blueprint from influenza virus. This nonnatural peptide was highly stable in human serum and gastric acid, reflecting an intrinsic resistance to physical and enzymatic degradation. In vitro, the synthetic agonist stimulated and expanded an archetypal repertoire of polyfunctional human influenza virus-specific [CD8.sup.+] T cells. In vivo, specific responses were elicited in naive humanized mice by subcutaneous vaccination, conferring protection from subsequent lethal influenza challenge. Moreover, the synthetic agonist was immunogenic after oral administration. This proof-of-concept study highlights the power of synthetic biology to expand the horizons of vaccine design and therapeutic delivery., Introduction [CD8.sup.+] T cells recognize short peptide fragments presented by MHC class I (MHC-I) molecules on the surface of nucleated cells (1-3). These peptide-MHC-I (pMHC-I) molecular arrays are scanned by [...]

Accurate assessment of SARS‐CoV‐2 immunity is critical in evaluating vaccine efficacy and devising public health policies. Whilst the exact nature of effective immunity remains incompletely defined, SARS‐CoV‐2‐specific T‐cell responses are a critical feature that will likely form a key correlate of protection against COVID‐19. Here, we developed and optimized a high‐throughput whole blood‐based assay to determine the T‐cell response associated with prior SARS‐CoV‐2 infection and/or vaccination amongst 231 healthy donors and 68 cancer patients. Following overnight in vitro stimulation with SARS‐CoV‐2‐specific peptides, blood plasma samples were analysed for TH1‐type cytokines. Highly significant differential IFN‐γ+/IL‐2+ SARS‐CoV‐2‐specific T‐cell responses were seen amongst previously infected COVID‐19‐positive healthy donors in comparison with unknown / naïve individuals (p < 0·0001). IFN‐γ production was more effective at identifying asymptomatic donors, demonstrating higher sensitivity (96·0% vs. 83·3%) but lower specificity (84·4% vs. 92·5%) than measurement of IL‐2. A single COVID‐19 vaccine dose induced IFN‐γ and/or IL‐2 SARS‐CoV‐2‐specific T‐cell responses in 116 of 128 (90·6%) healthy donors, reducing significantly to 27 of 56 (48·2%) when measured in cancer patients (p < 0·0001). A second dose was sufficient to boost T‐cell responses in the majority (90·6%) of cancer patients, albeit IFN‐γ+ responses were still significantly lower overall than those induced in healthy donors (p = 0·034). Three‐month post‐vaccination T‐cell responses also declined at a faster rate in cancer patients. Overall, this cost‐effective standardizable test ensures accurate and comparable assessments of SARS‐CoV‐2‐specific T‐cell responses amenable to widespread population immunity testing, and identifies individuals at greater need of booster vaccinations. [ABSTRACT FROM AUTHOR]

Oncolytic viruses possess the ability to infect, replicate and lyse malignantly transformed tumour cells. This oncolytic activity amplifies the therapeutic advantage and induces a form of immunogenic cell death, characterized by increased CD8 + T‐cell infiltration into the tumour microenvironment. This important feature of oncolytic viruses can result in the warming up of immunologically 'cold' tumour types, presenting the enticing possibility that oncolytic virus treatment combined with immunotherapies may enhance efficacy. In this review, we assess some of the most promising candidates that might be used for oncolytic virotherapy: immunotherapy combinations. We assess their potential as separate agents or as agents combined into a single therapy, where the immunotherapy is encoded within the genome of the oncolytic virus. The development of such advanced agents will require increasingly sophisticated model systems for their preclinical assessment and evaluation. In vivo rodent model systems are fraught with limitations in this regard. Oncolytic viruses replicate selectively within human cells and therefore require human xenografts in immune‐deficient mice for their evaluation. However, the use of immune‐deficient rodent models hinders the ability to study immune responses against any immunomodulatory transgenes engineered within the viral genome and expressed within the tumour microenvironment. There has therefore been a shift towards the use of more sophisticated ex vivo patient‐derived model systems based on organoids and explant co‐cultures with immune cells, which may be more predictive of efficacy than contrived and artificial animal models. We review the best of those model systems here. [ABSTRACT FROM AUTHOR]

Immune checkpoint inhibitors (antibodies that block the T cell co‐inhibitory receptors PD‐1/PD‐L1 or CTLA‐4) have revolutionized the treatment of some forms of cancer. Importantly, combination approaches using drugs that target both pathways have been shown to boost the efficacy of such treatments. Subsequently, several other T cell inhibitory receptors have been identified for the development of novel immune checkpoint inhibitors. Included in this list is the co‐inhibitory receptor lymphocyte activation gene‐3 (LAG‐3), which is upregulated on T cells extracted from tumor sites that have suppressive or exhausted phenotypes. However, the molecular rules that govern the function of LAG‐3 are still not understood. Using surface plasmon resonance combined with a novel bead‐based assay (AlphaScreenTM), we demonstrate that LAG‐3 can directly and specifically interact with intact human leukocyte antigen class II (HLA‐II) heterodimers. Unlike the homologue CD4, which has an immeasurably weak affinity using these biophysical approaches, LAG‐3 binds with low micromolar affinity. We further validated the interaction at the cell surface by staining LAG‐3+ cells with pHLA‐II‐multimers. These data provide new insights into the mechanism by which LAG‐3 initiates T cell inhibition. [ABSTRACT FROM AUTHOR]

Although metastatic disease is responsible for the majority of cancer deaths, tests of novel immunotherapies in mouse tumour models often focus on primary tumours without determining whether these therapies also target metastatic disease. This study examined the impact of depleting Foxp3+ regulatory T cells (Treg), on lung metastases, using a mouse model of breast cancer. After Treg-depletion, generation of an immune response to the primary tumour was a critical determinant for limiting development of metastasis. Indeed, resection of the primary tumour abrogated any effect of Treg-depletion on metastases. In addition, whilst the immune response, generated by the primary tumour, prevented metastases development, it had little impact on controlling established disease. Collectively, the data indicate that metastatic cells in the lung are not controlled by immune responses induced by the primary tumour. These findings indicate that targeting Tregs alone will not suffice for treating lung metastases. [ABSTRACT FROM AUTHOR]

Emerging studies have demonstrated the potential of PI3Kδ blockade as an immunotherapy for solid tumours. In pre-clinical models, we recently demonstrated that anti-LAG3 immune checkpoint blockade vastly potentiated PI3Kδ-based immunotherapy, enabling successful tumour control in all treated mice. [ABSTRACT FROM AUTHOR]

The homing molecule, L-selectin (CD62L), is commonly used as a T cell activation marker, since expression is downregulated following engagement of the T cell receptor. Studies in mice have shown that CD62L+ central memory T cells are better at controlling tumor growth than CD62L− effector memory T cells, while L-selectin knockout T cells are poor at controlling tumor growth. Here, we test the hypothesis that T cells expressing genetically modified forms of L-selectin that are maintained following T cell activation (L-selectin enhanced T cells) are better at controlling tumor growth than wild type T cells. Using mouse models of adoptive cell therapy, we show that L-selectin enhancement improves the efficacy of CD8+ T cells in controlling solid and disseminated tumor growth. L-selectin knockout T cells had no effect. Checkpoint blockade inhibitors synergized with wild type and L-selectin enhanced T cells but had no effect in the absence of T cell transfers. Reduced tumor growth by L-selectin enhanced T cells correlated with increased frequency of CD8+ tumor infiltrating T cells 21 days after commencing therapy. Longitudinal tracking of Zirconium-89 (89Zr) labeled T cells using PET-CT showed that transferred T cells localize to tumors within 1 h and accumulate over the following 7 days. L-selectin did not promote T cell homing to tumors within 18 h of transfer, however the early activation marker CD69 was upregulated on L-selectin positive but not L-selectin knockout T cells. L-selectin positive and L-selectin knockout T cells homed equally well to tumor-draining lymph nodes and spleens. CD69 expression was upregulated on both L-selectin positive and L-selectin knockout T cells but was significantly higher on L-selectin expressing T cells, particularly in the spleen. Clonal expansion of isolated L-selectin enhanced T cells was slower, and L-selectin was linked to expression of proliferation marker Ki67. Together these findings demonstrate that maintaining L-selectin expression on tumor-specific T cells offers an advantage in mouse models of cancer immunotherapy. The beneficial role of L-selectin is unrelated to its' well-known role in T cell homing and, instead, linked to activation of therapeutic T cells inside tumors. These findings suggest that L-selectin may benefit clinical applications in T cell selection for cancer therapy and for modifying CAR-T cells to broaden their clinical scope. [ABSTRACT FROM AUTHOR]