Activation of anti-SARS-CoV-2 human CTLs by extracellular vesicles engineered with the N viral protein

We investigated an innovative anti-SARS-CoV-2 immune strategy finalized to oral administration of extracellular vesicles (EVs) inducing an anti-SARS-CoV-2 N CD8+ T cytotoxic lymphocyte (CTL) immune response. We previously reported that the SARS-CoV-2 N protein can be uploaded at high levels in EVs upon fusion with Nefmut, i.e., a biologically inactive HIV-1 Nef mutant incorporating into EVs at quite high levels. Here, we analyze the immunogenic properties in human cells of EVs engineered with SARS-CoV-2 N fused at the C-terminus of either Nefmut or a deletion mutant of Nefmut referred to as NefmutPL. Analysis of in vitro produced EVs proven the uploading of N protein also when fused with truncated Nefmut. Mice injected with DNA vectors expressing each fusion protein developed robust SARS-CoV-2 N-specific CD8+ T cell immune responses. When ex vivo human dendritic cells were challenged with EVs engineered with either fusion products, the induction of a robust N-specific CTL activity, as evaluated by both CD107a and trogocytosis assays, was observed. Through these data we achieved the proof-of-principle that engineered EVs can be instrumental to elicit anti-SARS-CoV-2 CTL immune response in human cells. This achievement represents a mandatory step towards the upcoming experimentations in pre-clinical models.

Melanoma Stem Cell Vaccine Modified with IL-33 Induces Anti-Tumor Immunity by Activating CD8+T Cells

Background: Melanoma stem cells (MSCs)-based vaccine strategies have been a potent immunotherapeutic approach for melanoma treatment, which aimed at inducing specific anti-tumor immunity and targeting cancer stem-like cells. To boost anti-melanoma activity induced by B16F10 CD44+CD133+ MSCs (B16F10 MSCs) vaccine, we generated a novel vaccine expressing IL-33. Tumor growth and pulmonary metastasis were assessed to estimate the effectiveness of the vaccine. Methods: The antitumor effect of the vaccine was observed in this study. The mechanism of inducing anti-tumor immunity was detected by flow cytometric assays, cytotoxicity assays, and ELISA, including expression of CD8+T cells surface and intracellular molecules, the cytotoxic activity of splenocytes in the immunized mice and secretion of serum cytokines.Results: We found that MSCs vaccine expressing IL-33 significantly inhibited melanoma growth and reduced the lung melanoma nodules. Mechanistic investigations established that the vaccine-primed CD8+T cells could selectively target MSCs and confer anti-tumor immunity, which included promoting the proliferation of CD8+T cells, inhibiting the differentiated depletion of CD8+T cells in vivo, inducing the formation of memory CD8+T cells, and activating specific cytotoxic T lymphocyte (CTL) immune response. Conclusions: MSCs vaccine expressing IL-33 is able to initiate anti-tumor specific immune response by activating CD8+T cells.

Mathematical analysis of an HTLV-I infection model with the mitosis of CD4+ T cells and delayed CTL immune response

In this paper, we consider an improved Human T-lymphotropic virus type I (HTLV-I) infection model with the mitosis of CD4+ T cells and delayed cytotoxic T-lymphocyte (CTL) immune response by analyzing the distributions of roots of the corresponding characteristic equations, the local stability of the infection-free equilibrium, the immunity-inactivated equilibrium, and the immunity-activated equilibrium when the CTL immune delay is zero is established. And we discuss the existence of Hopf bifurcation at the immunity-activated equilibrium. We define the immune-inactivated reproduction ratio R0 and the immune-activated reproduction ratio R1. By using Lyapunov functionals and LaSalle’s invariance principle, it is shown that if R0 < 1, the infection-free equilibrium is globally asymptotically stable; if R1 < 1 < R0, the immunity-inactivated equilibrium is globally asymptotically stable; if R1 > 1, the immunity-activated equilibrium is globally asymptotically stable when the CTL immune delay is zero. Besides, uniform persistence is obtained when R1 > 1. Numerical simulations are carried out to illustrate the theoretical results.