Lifelong protection mediated by stem cell-like CD8(+) T memory subset cells (Tscm) induced by vaccination

Immunotherapeutic Potential of T Memory Stem Cells

Memory T cells include T memory stem cells (T_SCM) and central memory T cells (T_CM). Compared with effector memory T cells (T_EM) and effector T cells (T_EFF), they have better durability and anti-tumor immunity. Recent studies have shown that although T_SCM has excellent self-renewal ability and versatility, if it is often exposed to antigens and inflammatory signals, T_SCM will behave as a variety of inhibitory receptors such as PD-1, TIM-3 and LAG-3 expression, and metabolic changes from oxidative phosphorylation to glycolysis. These changes can lead to the exhaustion of T cells. Cumulative evidence in animal experiments shows that it is the least differentiated cell in the memory T lymphocyte system and is a central participant in many physiological and pathological processes in humans. It has a good clinical application prospect, so it is more and more important to study the factors affecting the formation of T_SCM. This article summarizes and prospects the phenotypic and functional characteristics of T_SCM, the regulation mechanism of formation, and its application in treatment of clinical diseases.

CD40 Accelerates the Antigen-Specific Stem-Like Memory CD8+ T Cells Formation and Human Papilloma Virus (HPV)-Positive Tumor Eradication

Antigen-specific stem-like memory CD8⁺ T cells (Tscm) have a series of stem cell characteristics, including long-term survival, self-renewal, anti-apoptosis and persistent differentiation into cytotoxic T cells. The effective induction of tumor-specific CD8⁺ Tscm could persistently eradicate tumor in pro-tumor hostile microenvironment. This study was to investigate the role of CD40 in HPV16-specific CD8⁺ Tscm induction and its anti-tumor function. We found that CD40 activation accelerated vaccine-induced HPV16 E7-specific CD8⁺ Tscm formation. Comparing to other HPV-specific CD8⁺ T cells, CD8⁺ Tscm were found to be stronger and long-term anti-tumor function, in vivo and in vitro, even in the adoptive cellular transferring model. Furthermore, high frequencies of Tscm might prevent the HPV infection to move on to the development of cancer. And the CD40 effect on Tscm involved Wnt/β-catenin activation. Our study suggest that CD40 activation supports the generation of tumor-specific CD8⁺ Tscm, thus providing new insight into cancer immunotherapy.

CD8+ T Cell Response to Trypanosoma cruzi Antigens during Chronic Chagas Disease

Flow cytometry is a valuable technique in cellular immunology that allows evaluating effective parameters of the immune response associated with CD8⁺ T cells. During Chagas disease, infection caused by Trypanosoma cruzi parasite, similar to other intracellular infectious agents, antigen-specific CD8⁺ T cells are essential for controlling the infection. However, CD8⁺ T cell response is only partially effective in some chronic Chagas disease patients. Thus, characterization and phenotyping of T. cruzi-specific CD8⁺ T cells are of great importance during chronic Chagas disease.

Antigen-specific CD8+ memory stem T cells generated from human peripheral blood effectively eradicate allogeneic targets in mice

BACKGROUND

As the implantation and long-term existence of tumor-specific T cells in host are the prerequisite for adoptive immunotherapy, memory stem T cells (T_SCM) with self-renewal and differentiation capacity show the greatest potential to implant and long-term exhibit function in vivo, compared with other T cells of differentiation stages. Hence, tumor-specific T_SCM have become potential candidate for adoptive T cell therapy of cancer. Here, we reported a protocol to generate allogeneic antigen-specific CD8+ T_SCM cells from human PBLs.

METHODS

To prepare allogeneic antigen-specific CD8+ T_SCM, we used an LCL named E007 of defined HLA allotyping as simulator, a co-culture of E007 and allogeneic PBLs was carried out in the presence of differentiation inhibitor TWS119 for 7 days. Sorting of proliferation cells ensured the E007-specificity of the prepared T_SCM cells. The sorted lymphocytes underwent further expansion by cytokines IL-7 and IL-15 for further 7 days, making the E007-specific CD8 + T_SCM expanded in number. The stem cell and T memory cell properties of the prepared CD8+ T_SCM were observed in NOD-SCID mice.

RESULTS

Our protocol began with 1 × 10⁷ PBLs and resulted in 2 × 10⁷ E007-specific CD8+ T_SCM cells in 2 weeks of preparation. The prepared T_SCM cells exhibited a proliferative history and rapid differentiation into effector cells upon the E007 re-stimulation. Importantly, the prepared T_SCM cells were able to exist long and reconstitute other T cell subsets in vivo, eradicating the E007 cells effectively after transferred into the LCL burden mice.

CONCLUSIONS

This protocol was able to prepare allogeneic antigen-specific CD8+ T_SCM cells from human PBLs. The prepared T_SCM showed the properties of stem cells and T memory cells. This study provided a reference method for generation of antigen-specific T_SCM for T cell adoptive immunotherapy.

Dynamics of T Cells Repertoire During Trypanosoma cruzi Infection and its Post-Treatment Modulation

Chagas disease courses with different clinical phases and has a variable clinical presentation and progression. The acute infection phase mostly exhibits a non-specific symptomatology. In the absence of treatment, the acute phase is followed by a chronic phase, which is initially asymptomatic. This chronic asymptomatic phase of the disease is characterized by a fragile balance between the host's immune response and the parasite replication. The loss of this balance is crucial for the progression of the sickness. The virulence and tropism of the T. cruzi infecting strain together to the inflammation processes in the cardiac tissue are the main factors for the establishment and severity of the cardiomyopathy. The efficacy of treatment in chronic Chagas disease patients is controversial. However, several studies carried out in chronic patients demonstrated that antiparasitic treatment reduces parasite load in the bloodstream and leads to an improvement in the immune response against the Trypanosoma cruzi parasite. The present review is mainly focused on the cellular patterns associated to the clinical status and the evolution of the disease in chronic patients, as well as the effectiveness of the treatment related to T. cruzi infection control. Therefore, an emphasis is placed on the dynamics of specific-antigens T cell subpopulations, their memory and activation phenotypes, their functionality and their contribution to pathogenesis or disease control, as well as their association with risk of congenital transmission of the parasite.