Harnessing iNKT cells to improve in situ vaccination for cancer therapy

<p>Toll-like receptor (TLR) agonism in combination with the activation of type I NKT (iNKT) cells through systemic administration of their respective agonists has been shown to have a cooperative effect on activating antigen-presenting cells, stimulating cytokine production, and inducing adaptive immune responses to co-administered antigens. Here, it was hypothesised that it might be possible to harness these activities to treat solid tumours locally via intratumoural treatment to combat tumour growth while reducing toxicity to other organs. An intratumoural treatment model combining the stimulatory activity of unmethylated DNA oligonucleotides consisting of synthetic cytosine-guanine motifs (CpG), a TLR9 agonist, with activation of iNKT cells through administration of the CD1d-binding iNKT agonist α-galactosylceramide (α-GalCer) intratumourally was shown to have significant anti-tumour activity. The treatment regimen showed superior efficacy to that achieved with either agent alone in several in vivo models representing different types of cancer. In some models, the combination of α-GalCer and CpG was effective at inducing the complete rejection of both treated and untreated tumours through the induction of a systemic adaptive immune response. Post tumour rejection, a memory response protected against rechallenge with the same, or similar, tumours. Intratumoural administration of the agents was associated with increases in IFN-α in the tumour (rather than the serum), and blockade or removal of the IFN-α receptor abrogated the anti-tumour response. The importance of the draining lymph node and spleen in anti-tumour activity (as shown by the excision of these organs), and liver enzyme responses, suggested that some of the agonists/antigens may have dispersed into the lymphoid organs and liver to support the response. Nonetheless, the anti-tumour effect was dependent on local effects of the intratumoural administration on the tumour microenvironment, as subcutaneous and peritumoural routes of administration only minimally affected tumour growth despite the reagents potentially having greater exposure to lymphoid organs. Through the use of various techniques including knockout mice, neutralising monoclonal antibodies, confocal microscopy and flow cytometry, it was shown that the combination of α-GalCer and CpG was dependent on the effector activity of CD8+ cells. However, optimal activity was associated with changes in other immune cell types, notably recruitment of iNKT cells into the tumour bed, and was also associated with induction of serum antibodies that could transfer some protection to naïve hosts. Induction of a successful response was dependent on conventional dendritic cells (DCs) of the “cDC1” phenotype, which are known to be effective at antigen cross-presentation to CD8+ T cells, while full tumour rejection also required the activity of plasmacytoid DCs, which are significant producers of IFN-α. In less immunogenic tumour models, the addition of relevant tumour associated antigens (TAAs) improved the anti-tumour response. The TAAs could be added as part of an admix, but improved responses were obtained when TAAs were chemically conjugated to α-GalCer via an enzymatically cleavable linker. Alternatively, intratumoural administration of α-GalCer and CpG as free agents could be combined effectively with low dose systemic chemotherapy to induce curative responses, potentially through a mechanism involving immunogenic cell death to improve the immunogenicity of TAAs in situ.</p>

Harnessing iNKT cells to improve in situ vaccination for cancer therapy

<p>Toll-like receptor (TLR) agonism in combination with the activation of type I NKT (iNKT) cells through systemic administration of their respective agonists has been shown to have a cooperative effect on activating antigen-presenting cells, stimulating cytokine production, and inducing adaptive immune responses to co-administered antigens. Here, it was hypothesised that it might be possible to harness these activities to treat solid tumours locally via intratumoural treatment to combat tumour growth while reducing toxicity to other organs. An intratumoural treatment model combining the stimulatory activity of unmethylated DNA oligonucleotides consisting of synthetic cytosine-guanine motifs (CpG), a TLR9 agonist, with activation of iNKT cells through administration of the CD1d-binding iNKT agonist α-galactosylceramide (α-GalCer) intratumourally was shown to have significant anti-tumour activity. The treatment regimen showed superior efficacy to that achieved with either agent alone in several in vivo models representing different types of cancer. In some models, the combination of α-GalCer and CpG was effective at inducing the complete rejection of both treated and untreated tumours through the induction of a systemic adaptive immune response. Post tumour rejection, a memory response protected against rechallenge with the same, or similar, tumours. Intratumoural administration of the agents was associated with increases in IFN-α in the tumour (rather than the serum), and blockade or removal of the IFN-α receptor abrogated the anti-tumour response. The importance of the draining lymph node and spleen in anti-tumour activity (as shown by the excision of these organs), and liver enzyme responses, suggested that some of the agonists/antigens may have dispersed into the lymphoid organs and liver to support the response. Nonetheless, the anti-tumour effect was dependent on local effects of the intratumoural administration on the tumour microenvironment, as subcutaneous and peritumoural routes of administration only minimally affected tumour growth despite the reagents potentially having greater exposure to lymphoid organs. Through the use of various techniques including knockout mice, neutralising monoclonal antibodies, confocal microscopy and flow cytometry, it was shown that the combination of α-GalCer and CpG was dependent on the effector activity of CD8+ cells. However, optimal activity was associated with changes in other immune cell types, notably recruitment of iNKT cells into the tumour bed, and was also associated with induction of serum antibodies that could transfer some protection to naïve hosts. Induction of a successful response was dependent on conventional dendritic cells (DCs) of the “cDC1” phenotype, which are known to be effective at antigen cross-presentation to CD8+ T cells, while full tumour rejection also required the activity of plasmacytoid DCs, which are significant producers of IFN-α. In less immunogenic tumour models, the addition of relevant tumour associated antigens (TAAs) improved the anti-tumour response. The TAAs could be added as part of an admix, but improved responses were obtained when TAAs were chemically conjugated to α-GalCer via an enzymatically cleavable linker. Alternatively, intratumoural administration of α-GalCer and CpG as free agents could be combined effectively with low dose systemic chemotherapy to induce curative responses, potentially through a mechanism involving immunogenic cell death to improve the immunogenicity of TAAs in situ.</p>

A balance score between immune stimulatory and suppressive microenvironments identifies mediators of tumour immunity and predicts pan-cancer survival

Background The balance between immune-stimulatory and immune-suppressive mechanisms in the tumour microenvironment is associated with tumour rejection and can predict the efficacy of immune checkpoint-inhibition therapies. Methods We consider the observed differences between the transcriptional programmes associated with cancer types where the levels of immune infiltration predict a favourable prognosis versus those in which the immune infiltration predicts an unfavourable prognosis and defined a score named Mediators of Immune Response Against Cancer in soLid microEnvironments (MIRACLE). MIRACLE deconvolves T cell infiltration, from inhibitory mechanisms, such as TGFβ, EMT and PI3Kγ signatures. Results Our score outperforms current state-of-the-art immune signatures as a predictive marker of survival in TCGA (n = 9305, HR: 0.043, p value: 6.7 × 10−36). In a validation cohort (n = 7623), MIRACLE predicts better survival compared to other immune metrics (HR: 0.1985, p value: 2.73 × 10−38). MIRACLE also predicts response to checkpoint-inhibitor therapies (n = 333). The tumour-intrinsic factors inversely associated with the reported score such as EGFR, PRKAR1A and MAP3K1 are frequently associated with immune-suppressive phenotypes. Conclusions The association of cancer outcome with the level of infiltrating immune cells is mediated by the balance of activatory and suppressive factors. MIRACLE accounts for this balance and predicts favourable cancer outcomes.

Neoleukin-2 enhances anti-tumour immunity downstream of peptide vaccination targeted by an anti-MHC class II VHH

Cancer-specific mutations can lead to peptides of unique sequence presented on MHC class I to CD8 T cells. These neoantigens can be potent tumour-rejection antigens, appear to be the driving force behind responsiveness to anti-CTLA-4 and anti-PD1/L1-based therapies and have been used to develop personalized vaccines. The platform for delivering neoantigen-based vaccines has varied, and further optimization of both platform and adjuvant will be necessary to achieve scalable vaccine products that are therapeutically effective at a reasonable cost. Here, we developed a platform for testing potential CD8 T cell tumour vaccine candidates. We used a high-affinity alpaca-derived VHH against MHC class II to deliver peptides to professional antigen-presenting cells. We show in vitro and in vivo that peptides derived from the model antigen ovalbumin are better able to activate naive ovalbumin-specific CD8 T cells when conjugated to an MHC class II-specific VHH when compared with an irrelevant control VHH. We then used the VHH-peptide platform to evaluate a panel of candidate neoantigens in vivo in a mouse model of pancreatic cancer. None of the candidate neoantigens tested led to protection from tumour challenge; however, we were able to show vaccine-induced CD8 T cell responses to a melanoma self-antigen that was augmented by combination therapy with the synthetic cytokine mimetic Neo2/15.

Oncolytic bacteria: past, present and future

ABSTRACTMore than a century ago, independent groups raised the possibility of using bacteria to selectively infect tumours. Such treatment induces an immune reaction that can cause tumour rejection and protect the patient against further recurrences. One of the first holistic approximations to use bacteria in cancer treatment was performed by William Coley, considered the father of immune-therapy, at the end of XIX century. Since then, many groups have used different bacteria to test their antitumour activity in animal models and patients. The basis for this reactivity implies that innate immune responses activated upon bacteria recognition, also react against the tumour. Different publications have addressed several aspects of oncolytic bacteria. In the present review, we will focus on revisiting the historical aspects using bacteria as oncolytic agents and how they led to the current clinical trials. In addition, we address the molecules present in oncolytic bacteria that induce specific toxic effects against the tumors as well as the activation of host immune responses in order to trigger antitumour immunity. Finally, we discuss future perspectives that could be considered in the different fields implicated in the implementation of this kind of therapy in order to improve the current use of bacteria as oncolytic agents.

Clinically Relevant Immune Responses against Cytomegalovirus: Implications for Precision Medicine

Immune responses to human cytomegalovirus (CMV) can be used to assess immune fitness in an individual. Further to its clinical significance in posttransplantation settings, emerging clinical and translational studies provide examples of immune correlates of protection pertaining to anti-CMV immune responses in the context of cancer or infectious diseases, e.g., tuberculosis. In this viewpoint, we provide a brief overview about CMV-directed immune reactivity and immune fitness in a clinical context and incorporate some of our own findings obtained from peripheral blood or tumour-infiltrating lymphocytes (TIL) from patients with advanced cancer. Observations in patients with solid cancers whose lesions contain both CMV and tumour antigen-specific T-cell subsets are highlighted, due to a possible CMV-associated “bystander” effect in amplifying local inflammation and subsequent tumour rejection. The role of tumour-associated antibodies recognising diverse CMV-derived epitopes is also discussed in light of anti-cancer immune responses. We discuss here the use of anti-CMV immune responses as a theranostic tool—combining immunodiagnostics with a personalised therapeutic potential—to improve treatment outcomes in oncological indications.