Gustavo Pessini Amarante-Mendes

Live recombinant Listeria monocytogenes (Lm) vaccines are usually framed as intracellular antigen-delivery platforms endowed with intrinsic adjuvant activity. Here we argue that this view may be incomplete. Because Lm vaccines strongly engage innate immune cells, their efficacy might depend on both immediate inflammatory signaling and a separately established or acquired trained state. Importantly, direct evidence that recombinant Lm induces bona fide trained immunity - defined by durable functional changes supported by epigenetic and metabolic reprogramming beyond the initial inflammatory phase - is currently limited. We consider two distinct questions: whether pre-existing trained immunity changes the efficacy of subsequent Lm vaccination, and whether Lm vaccination itself induces a lasting trained innate program in addition to antigen-specific CD8 T-cell immunity. Pre-existing training could alter vector clearance, antigen presentation, and initial T-cell priming, whereas hypothetical Lm-induced training could affect later tumor-microenvironment function, memory recall, and long-term tumor control without accounting for the initial CD8 T-cell response. Either scenario might enhance or constrain efficacy, and the two require different experimental examinations. We propose trained innate reprogramming as a testable mechanistic variable, rather than an established property of Lm vaccines, with implications for vaccine design, repeated dosing, safety, and interpretation of antitumor vaccines.

Memory T cells are essential for effective and durable immune responses, as they provide long-term immunological surveillance and rapid reactivity upon re-exposure to a given pathogen or cancer cell. In solid tumors, the immunosuppressive tumor microenvironment (TME) often hinders immune activation, making enhancing memory T cell formation and persistence a key goal in cancer immunotherapy. Novel strategies are exploring ways to support these memory T cells, including using Listeria monocytogenes as a cancer vaccine vector. Notably, L. monocytogenes has unique properties that make it an ideal candidate for this purpose: it is highly effective at activating T cells, promoting the differentiation and survival of memory T cells, and modulating the TME to favor immune cell function. Thus, by leveraging the ability of L. monocytogenes to induce a strong, sustained T-cell response, researchers aim to develop vaccines that provide lasting immunity against tumors, reduce recurrence rates, and improve patient survival outcomes. This mini-review highlights the potential of memory T cell-focused cancer immunotherapy and the promising role of L. monocytogenes in advancing these efforts.

One of the main objectives of developing new anti-cancer vaccine strategies is to effectively induce CD8+ T cell-mediated anti-tumor immunity. Live recombinant vectors, notably Listeria monocytogenes, have been shown to elicit a robust in vivo CD8+ T-cell response in preclinical settings. Significantly, it has been demonstrated that Listeria induces inflammatory/immunogenic cell death mechanisms such as pyroptosis and necroptosis in immune cells that favorably control immunological responses. Therefore, we postulated that the host’s response to Listeria-based vectors and the subsequent induction of CD8+ T cell-mediated immunity would be compromised by the lack of regulatory or effector molecules involved in pyroptosis or necroptosis. To test our hypothesis, we used recombinant L. monocytogenes carrying the ovalbumin gene (LM.OVA) to vaccinate wild-type (WT), caspase-1/11^−/−, gsdmd^−/−, ripk3^−/−, and mlkl^−/− C57Bl/6 mice. We performed an in vivo cytotoxicity assay to assess the efficacy of OVA-specific CD8+ T lymphocytes in eliminating target cells in wild-type and genetically deficient backgrounds. Furthermore, we evaluated the specific anti-tumor immune response in mice inoculated with the B16F0 and B16F0.OVA melanoma cell lines. Our findings demonstrated that while caspase-1/11 and GSDMD deficiencies interfere with the rapid control of LM.OVA infection, neither of the KOs seems to contribute to the early activation of OVA-specific CTL responses. In contrast, the individual deficiency of each one of these proteins positively impacts the generation of long-lasting effector CD8+ T cells.

One of the main objectives of developing new anti-cancer vaccine strategies is to effectively induce CD8+ T cell-mediated anti-tumor immunity. Live recombinant vectors, notably Listeria mono-cytogenes, have been shown to elicit a robust in vivo CD8+ T cell response in preclinical settings. Significantly, it has been demonstrated that Listeria induces inflammatory/immunogenic cell death mechanisms such as pyroptosis and necroptosis in immune cells that favorably control immunological responses. Therefore, we postulated that the host's response to Listeria-based vec-tors and the subsequent induction of CD8+ T cell-mediated immunity would be compromised by the lack of regulatory or effector molecules involved in pyroptosis or necroptosis. To test our hy-pothesis, we used recombinant L. monocytogenes carrying the ovalbumin gene (LM.OVA) to vac-cinate wild-type (WT), caspase-1/11-/-, gsdmd-/-, ripk3-/-, and mlkl-/- C57Bl/6 mice. We performed an in vivo cytotoxicity assay to assess the efficacy of OVA-specific CD8+ T lymphocytes in eliminat-ing target cells in wild-type and genetically deficient backgrounds. Furthermore, we evaluated the specific anti-tumor immune response in mice inoculated with B16F0 and B16F0.OVA mela-noma cell lines. Our findings demonstrated that while caspase-1/11 and GSDMD deficiencies in-terfere with the rapid control LM.OVA infection, of the KO seems to contribute to the early acti-vation of OVA-specific CTL responses. In contrast, individual deficiency of each one of these pro-teins negatively impact the generation of long-lasting effector CD8+ T cells.

Chronic myeloid leukemia (CML) was considered for a long time one of the most hostile leukemia that was incurable for most of the patients, predominantly due to the extreme resistance to chemotherapy. Part of the resistance to cell death (apoptosis) is the result of increased levels of anti-apoptotic and decreased levels of pro-apoptotic member of the BCL-2 family induced by the BCR-ABL1 oncoprotein. BCR-ABL1 is a constitutively active tyrosine kinase responsible for initiating multiple and oncogenic signaling pathways. With the development of specific BCR-ABL1 tyrosine kinase inhibitors (TKIs) CML became a much more tractable disease. Nevertheless, TKIs do not cure CML patients and a substantial number of them develop intolerance or become resistant to the treatment. Therefore, novel anti-cancer strategies must be developed to treat CML patients independently or in combination with TKIs. Here, we will discuss the mechanisms of BCR-ABL1-dependent and -independent resistance to TKIs and the use of BH3-mimetics as a potential tool to fight CML.

Malaria is an enormous burden on global health that caused 409,000 deaths in 2019. Severe malaria can manifest in the lungs, an illness known as acute respiratory distress syndrome (ARDS). Not much is known about the development of malaria-associated ARDS (MA-ARDS), especially regarding cell death in the lungs. We had previously established a murine model that mimics various human ARDS aspects, such as pulmonary edema, hemorrhages, pleural effusion, and hypoxemia, using DBA/2 mice infected with Plasmodium berghei ANKA. Here, we explored the mechanisms and the involvement of apoptosis in this syndrome. We found that apoptosis contributes to the pathogenesis of MA-ARDS, primarily as facilitators of the alveolar-capillary barrier breakdown. The protection of pulmonary endothelium by inhibiting caspase activation could be a promising therapeutic strategy to prevent the pathogenicity of MA-ARDS. Therefore, intervention in the programmed death cell mechanism could help patients not to develop severe malaria.

The constitutively active BCR-ABL1 tyrosine kinase, found in t(9;22)(q34;q11) chromosomal translocation-derived leukemia, initiates an extremely complex signaling transduction cascade that induces a strong state of resistance to chemotherapy. Targeted therapies based on tyrosine kinase inhibitors (TKIs), such as imatinib, dasatinib, nilotinib, bosutinib, and ponatinib, have revolutionized the treatment of BCR-ABL1-driven leukemia, particularly chronic myeloid leukemia (CML). However, TKIs do not cure CML patients, as some develop TKI resistance and the majority relapse upon withdrawal from treatment. Importantly, although BCR-ABL1 tyrosine kinase is necessary to initiate and establish the malignant phenotype of Ph-related leukemia, in the later advanced phase of the disease, BCR-ABL1-independent mechanisms are also in place. Here, we present an overview of the signaling pathways initiated by BCR-ABL1 and discuss the major challenges regarding immunologic/pharmacologic combined therapies.

Chagas disease is a life-threatening disorder caused by the protozoan parasiteTrypanosoma cruzi. Parasite-specific antibodies, CD8⁺T cells, as well as IFN-γ and nitric oxide (NO) are key elements of the adaptive and innate immunity against the extracellular and intracellular forms of the parasite. Bim is a potent pro-apoptotic member of the Bcl-2 family implicated in different aspects of the immune regulation, such as negative selection of self-reactive thymocytes and elimination of antigen-specific T cells at the end of an immune response. Interestingly, the role of Bim during infections remains largely unidentified. To explore the role of Bim in Chagas disease, we infected WT,Bim^+/−,Bim^−/−mice with trypomastigotes forms of the Y strain ofT. cruzi. Strikingly, our data revealed thatBim^−/−mice exhibit a delay in the development of parasitemia followed by a deficiency in the control of parasite load in the bloodstream and a decreased survival compared to WT andBim^+/−mice. At the peak of parasitemia, peritoneal macrophages ofBim^−/−mice exhibit decreased NO production, which correlated with a decrease in the pro-inflammatory Small Peritoneal Macrophage (SPM) subset. A similar reduction in NO secretion, as well as in the pro-inflammatory cytokines IFN-γ and IL-6, was also observed inBim^−/−splenocytes. Moreover, an impaired anti-T. cruziCD8⁺T-cell response was found inBim^−/−mice at this time point. Taken together, our results suggest that these alterations may contribute to the establishment of a delayed yet enlarged parasitic load observed at day 9 after infection ofBim^−/−mice and place Bim as an important protein in the control ofT. cruziinfections.