Phagosomes induced by cytokines function as anti-Listeria vaccines: novel role for functional compartmentalization of STAT-1 protein and cathepsin-D

Investigation of Effects of the Spectral Library on Analysis of diaPASEF Data

Targeted analysis of data-independent acquisition (DIA) data needs a spectral library, which is generated by data-dependent acquisition (DDA) experiments or directly from DIA data. A comparison of the DDA library and DIA library in analyzing DIA data has been reported. However, the effects of different spectral libraries on the analysis of diaPASEF data have not been investigated. Here, we generate different spectral libraries with varying proteome coverage to analyze parallel accumulation-serial fragmentation (diaPASEF) data. Besides, we also employ the library-free strategy. The library, constructed by extensive fractionation DDA experiments, produces the highest numbers of precursors and proteins but with a high percentage of missing values. The library-free strategy identifies 10-20% fewer proteins than the library-based method but with a high degree of data completeness. A further study shows that the library-free strategy, although it identifies fewer proteins than the library-based method, leads to similar biological conclusions as the library-based method.

Exceptional antineoplastic activity of a dendritic-cell-targeted vaccine loaded with a Listeria peptide proposed against metastatic melanoma

Vaccination with dendritic cells (DCs) is proposed to induce lasting responses against melanoma but its survival benefit in patients needs to be demonstrated. We propose a DC-targeted vaccine loaded with a Listeria peptide with exceptional anti-tumour activity to prevent metastasis of melanoma. Mice vaccinated with vaccines based on DCs loaded with listeriolysin O peptide (91–99) (LLO_91–99) showed clear reduction of metastatic B16OVA melanoma size and adhesion, prevention of lung metastasis, enhanced survival, and reversion of immune tolerance. Robust innate and specific immune responses explained the efficiency of DC-LLO_91–99 vaccines against B16OVA melanoma. The noTable features of this vaccine related to melanoma reduction were: expansion of immune-dominant LLO_91–99-specific CD8 T cells that helped to expand melanoma-specific CD8⁺ T cells; high numbers of tumour-infiltrating lymphocytes with a cytotoxic phenotype; and a decrease in CD4⁺CD25^high regulatory T cells. This vaccine might be a useful alternative treatment for advanced melanoma, alone or in combination with other therapies.

GNP-GAPDH1-22 nanovaccines prevent neonatal listeriosis by blocking microglial apoptosis and bacterial dissemination

Clinical cases of neonatal listeriosis are associated with brain disease and fetal loss due to complications in early or late pregnancy, which suggests that microglial function is altered. This is believed to be the first study to link microglial apoptosis with neonatal listeriosis and listeriosis-associated brain disease, and to propose a new nanovaccine formulation that reverses all effects of listeriosis and confers Listeria monocytogenes (LM)-specific immunity. We examined clinical cases of neonatal listeriosis in 2013–2015 and defined two useful prognostic immune biomarkers to design listeriosis vaccines: high anti-GAPDH_1-22 titres and tumor necrosis factor (TNF)/interleukin (IL)-6 ratios. Therefore, we developed a nanovaccine with gold glyco-nanoparticles conjugated to LM peptide 1-22 of GAPDH (Lmo2459), GNP-GAPDH_1-22 nanovaccinesformulated with a pro-inflammatory Toll-like receptor 2/4-targeted adjuvant. Neonates born to non-vaccinated pregnant mice with listeriosis, showed brain and vascular diseases and significant microglial dysfunction by induction of TNF-α-mediated apoptosis. This programmed TNF-mediated suicide explains LM dissemination in brains and livers and blocks production of early pro-inflammatory cytokines such as IL-1β and interferon-α/β. In contrast, neonates born to GNP-GAPDH_1–22-vaccinated mothers before LM infection, did not develop listeriosis or brain diseases and had functional microglia. In nanovaccinated mothers, immune responses shifted towards Th1/IL-12 pro-inflammatory cytokine profiles and high production of anti-GAPDH_1–22 antibodies, suggesting good induction of LM-specific memory.

From Antigen Delivery System to Adjuvanticy: The Board Application of Nanoparticles in Vaccinology

In the last years, nanotechnologies have raised great interest because of the potential applications of engineered nanoparticles in nanomedicine (i.e., in vaccination, in diagnostic imaging procedures, and as therapeutic drug delivery systems). The use of nanoparticles in medicine has brought about the issue of their interaction with the immune system for two main reasons: first, understanding how long nanomedicines could persist in the organism and exert their beneficial effects before being recognized and eliminated by our defensive systems; second, understanding how the immune responses can be modulated by nanoparticles in order to obtain optimal effects. This issue is crucial in vaccine formulations based on the use of nanoparticles, which can operate both as a delivery system to enhance antigen processing and as an immunostimulatory adjuvant to induce and amplify protective immunity, in part because of their ability to activate the inflammasome and induce the maturation of interleukin 1β. Nanoparticles can be excellent adjuvants due to their biocompatibility and their physicochemical properties (e.g., size, shape, and surface charge), which can be tailored to obtain different immunological effects. This review provides an overview of recent strategies for the use of nanoparticles as promising/attractive adjuvants for novel prophylactic and therapeutic vaccines. The use of nanovaccines, with their practically infinite possibilities of specific design, could open the way to precision vaccinology, i.e., vaccine formulations tailored on the individual immune reactivity status.

A novel therapy for melanoma developed in mice: transformation of melanoma into dendritic cells with Listeria monocytogenes

Listeria monocytogenes is a gram-positive bacteria and human pathogen widely used in cancer immunotherapy because of its capacity to induce a specific cytotoxic T cell response in tumours. This bacterial pathogen strongly induces innate and specific immunity with the potential to overcome tumour induced tolerance and weak immunogenicity. Here, we propose a Listeria based vaccination for melanoma based in its tropism for these tumour cells and its ability to transform in vitro and in vivo melanoma cells into matured and activated dendritic cells with competent microbicidal and antigen processing abilities. This Listeria based vaccination using low doses of the pathogen caused melanoma regression by apoptosis as well as bacterial clearance. Vaccination efficacy is LLO dependent and implies the reduction of LLO-specific CD4⁺ T cell responses, strong stimulation of innate pro-inflammatory immune cells and a prevalence of LLO-specific CD8⁺ T cells involved in tumour regression and Listeria elimination. These results support the use of low doses of pathogenic Listeria as safe melanoma therapeutic vaccines that do not require antibiotics for bacterial removal.

A gold glyco-nanoparticle carrying a Listeriolysin O peptide and formulated with Advax™ delta inulin adjuvant induces robust T-cell protection against listeria infection

In the search for an effective vaccine against the human pathogen, Listeria monocytogenes (Listeria), gold glyconanoparticles (GNP) loaded with a listeriolysin O peptide LLO91-99 (GNP-LLO) were used to immunise mice, initially using a dendritic cell (DC) vaccine approach, but subsequently using a standard parenteral immunisation approach. To enhance vaccine immunogenicity a novel polysaccharide adjuvant based on delta inulin (Advax™) was also co-formulated with the GNP vaccine. Confirming previous results, DC loaded in vitro with GNP-LLO provided better protection against listeriosis than DC loaded in vitro using free LLO peptide. The immunogenicity of GNP-LLO loaded DC vaccines was further increased by addition of Advax™ adjuvant. However, as DC vaccines are expensive and impracticable for prophylactic use, we next asked whether the same GNP-LLO antigen could be used to directly target DC in vivo. Immunisation of mice with GNP-LLO plus Advax™ adjuvant induced LLO-specific T-cell immunity and protection against Listeria challenge. Protection correlated with an increased frequency of splenic CD4(+) and CD8(+) T cells, NK cells and CD8α(+) DC, and Th1 cytokine production (IL-12, IFN-γ, TNF-α, and MCP-1), post-challenge. Enhanced T-cell epitope recruitment post-challenge was seen in the groups that received Advax™ adjuvant. Immunisation with GNP-LLO91-99 plus Advax™ adjuvant provided equally robust Listeria protection as the best DC vaccine strategy but without the complexity and cost, making this a highly promising strategy for development of a prophylactic vaccine against listeriosis.

Improved vaccine efficacy of tumor exosome compared to tumor lysate loaded dendritic cells in mice

Leukemia immunotherapy frequently does not meet expectation, one of the handicaps being tumor exosome (TEX)-promoted immunosuppression. We here asked, using the mouse myeloid leukemia WEHI3B and the renal cell carcinoma line RENCA, whether dendritic cell (DC) vaccination suffices to counterregulate TEX-induced immunosuppression and whether TEX could serve as tumor antigen for DC-loading. DC-vaccination significantly prolonged the survival time of WEHI3B-bearing mice, TEX-loaded DC (DC-TEX) being superior to lysate-loaded DC (DC-lys), even an excess of TEX not interfering with immune response induction. The superior response to DC-TEX was accompanied by an increase in WEHI3B-specific CD4+ T cells, evaluated by trogocytosis and proliferation. Similar findings accounted for DC loaded with RENCA TEX. TEX was efficiently taken-up by DC and TEX uptake supported CD11c, MHCII and IL12 upregulation in DC. Importantly, TEX was partly recruited into the MHCII-loading compartment such that "TEX" presentation time and recovery in T cells significantly exceeded that of tumor-lysate. Thus, TEX did not drive DC into a suppressive phenotype and were a superior antigen due to higher efficacy of TEX-presentation that is supported by prolonged persistence, preferential processing in the MHCII-loading compartment and pronounced trogocytosis by T helper cells. TEX is present in tumor patients' sera. TEX, recovered and enriched from patients' sera, might well provide an optimized, individual-specific antigen source for DC-loading and vaccination.

Cellular vaccines in listeriosis: role of the Listeria antigen GAPDH

The use of live Listeria-based vaccines carries serious difficulties when administrated to immunocompromised individuals. However, cellular carriers have the advantage of inducing multivalent innate immunity as well as cell-mediated immune responses, constituting novel and secure vaccine strategies in listeriosis. Here, we compare the protective efficacy of dendritic cells (DCs) and macrophages and their safety. We examined the immune response of these vaccine vectors using two Listeria antigens, listeriolysin O (LLO) and glyceraldehyde-3-phosphate-dehydrogenase (GAPDH), and several epitopes such as the LLO peptides, LLO_189−201 and LLO₉₁₋₉₉ and the GAPDH peptide, GAPDH₁₋₂₂. We discarded macrophages as safe vaccine vectors because they show anti-Listeria protection but also high cytotoxicity. DCs loaded with GAPDH₁₋₂₂ peptide conferred higher protection and security against listeriosis than the widely explored LLO₉₁₋₉₉ peptide. Anti-Listeria protection was related to the changes in DC maturation caused by these epitopes, with high production of interleukin-12 as well as significant levels of other Th1 cytokines such as monocyte chemotactic protein-1, tumor necrosis factor-α, and interferon-γ, and with the induction of GAPDH₁₋₂₂-specific CD4⁺ and CD8⁺ immune responses. This is believed to be the first study to explore the use of a novel GAPDH antigen as a potential DC-based vaccine candidate for listeriosis, whose efficiency appears to highlight the relevance of vaccine designs containing multiple CD4⁺ and CD8⁺ epitopes.

Dissociation of innate immune responses in microglia infected with Listeria monocytogenes

Microglia, the innate immune cells of the brain, plays a central role in cerebral listeriosis. Here, we present evidence that microglia control Listeria infection differently than macrophages. Infection of primary microglial cultures and murine cell lines with Listeria resulted in a dual function of the two gene expression programmes involved in early and late immune responses in macrophages. Whereas the bacterial gene hly seems responsible for both transcriptional programmes in macrophages, Listeria induces in microglia only the tumor necrosis factor (TNF)-regulated transcriptional programme. Listeria also represses in microglia the late immune response gathered in two clusters, microbial degradation, and interferon (IFN)-inducible genes. The bacterial gene actA was required in microglia to induce TNF-regulated responses and to repress the late response. Isolation of microglial phagosomes revealed a phagosomal environment unable to destroy Listeria. Microglial phagosomes were also defective in several signaling and trafficking components reported as relevant for Listeria innate immune responses. This transcriptional strategy in microglia induced high levels of TNF-α and monocyte chemotactic protein-1 and low production of other neurotoxic compounds such as nitric oxide, hydrogen peroxide, and Type I IFNs. These cytokines and toxic microglial products are also released by primary microglia, and this cytokine and chemokine cocktail display a low potential to trigger neuronal apoptosis. This overall bacterial strategy strongly suggests that microglia limit Listeria inflammation pattern exclusively through TNF-mediated responses to preserve brain integrity.