Cytotoxic CD4+ T cells driven by T-cell intrinsic IL-18R/MyD88 signaling predominantly infiltrate Trypanosoma cruzi-infected hearts

Cytotoxic CD4+ T Cells Are Induced during Infection with Chlamydia trachomatis

Chlamydia trachomatis is the most common cause of bacterial sexually transmitted infection in both men and women. Immunity to C. trachomatis involves many cell types, but CD4+ T cells play a key role in protecting the host during natural infection. Specifically, IFN-γ production by CD4+ T cells is the main effector responsible for bacterial clearance, yet the exact mechanism by which IFN-γ confers protection is poorly defined. In our efforts to define the specific mechanisms for bacterial clearance, we now show that IFN-γ upregulates expression of MHC class II (MHCII) on nonhematopoietic cells during C. trachomatis infection in vivo. We also find that MHCII expression on epithelial cells of the upper genital tract contributes to the efficient clearance of bacteria mediated by pathogen-specific CD4+ Th1 cells. As we further cataloged the protective mechanisms of C. trachomatis-specific CD4+ T cells, we found that the T cells also express granzyme B (GzmB) when coincubated with infected cells. In addition, during C. trachomatis infection of mice, primed activated-naive CD4+ Th1 cells displayed elevated granzyme transcripts (GzmA, GzmB, GzmM, GzmK, GzmC) compared with memory CD4+ T cells in vivo. Finally, using intracellular cytokine staining and a GzmB-/- mouse strain, we show that C. trachomatis-specific CD4+ Th1 cells express GzmB upon Ag stimulation, and that this correlates with Chlamydia clearance in vivo. Together these results have led us to conclude that Chlamydia-specific CD4+ Th1 cells develop cytotoxic capacity through engagement with nonhematopoietic MHCII, and this correlates to C. trachomatis clearance.

MyD88 and Its Inhibitors in Cancer: Prospects and Challenges

The interplay between the immune system and cancer underscores the central role of immunotherapy in cancer treatment. In this context, the innate immune system plays a critical role in preventing tumor invasion. Myeloid differentiation factor 88 (MyD88) is crucial for innate immunity, and activation of MyD88 promotes the production of inflammatory cytokines and induces infiltration, polarization, and immune escape of immune cells in the tumor microenvironment. Additionally, abnormal MyD88 signaling induces tumor cell proliferation and metastasis, which are closely associated with poor prognosis. Therefore, MyD88 could serve as a novel tumor biomarker and is a promising target for cancer therapy. Current strategies targeting MyD88 including inhibition of signaling pathways and protein multimerization, have made substantial progress, especially in inflammatory diseases and chronic inflammation-induced cancers. However, the specific role of MyD88 in regulating tumor immunity and tumorigenic mechanisms remains unclear. Therefore, this review describes the involvement of MyD88 in tumor immune escape and disease therapy. In addition, classical and non-classical MyD88 inhibitors were collated to provide insights into potential cancer treatment strategies. Despite several challenges and complexities, targeting MyD88 is a promising avenue for improving cancer treatment and has the potential to revolutionize patient outcomes.

The compensatory role of T cells from lymph nodes in mice with splenectomy

The spleen is a vital organ for the immune system, while splenectomy may be necessary for various reasons. However, there is limited research on the impact of splenectomy on T cell function in peripheral lymph nodes as a compensatory mechanism in preventing infections. This study aimed to investigate the characteristics and function of CD8+ and CD4+ T cells in different peripheral lymph nodes during viral infection using a well-established splenectomy model. The results revealed that splenectomy caused an increase in CD8+GP33+ T cells in the mesenteric lymph nodes (MLN). Moreover, we demonstrated that splenectomy resulted in an increase of effector KLRG1+ T cells in the MLN. Additionally, the number of CD4+ cytotoxic T cells (CD4 CTLs) was also elevated in the peripheral lymph nodes of mice with splenectomy. Surprisingly, aged mice exhibited a stronger compensatory ability than adult mice, as evidenced by an increase in effector CD8+ T cells in all peripheral lymph nodes. These findings provide compelling evidence that T cells in MLN play a crucial role in protecting individuals with splenectomy against viral infections. The study offers new insights into understanding the changes in the immune system of individuals with splenectomy and highlights the potential compensatory mechanisms involved by T cells in peripheral lymph nodes.

Role of immune cells in the pathogenesis of myocarditis

Myocarditis is an inflammatory heart disease that mostly affects young people. Myocarditis involves a complex immune network; however, its detailed pathogenesis is currently unclear. The diversity and plasticity of immune cells, either in the peripheral blood or in the heart, have been partially revealed in a number of previous studies involving patients and several kinds of animal models with myocarditis. It is the complexity of immune cells, rather than one cell type that is the culprit. Thus, recognizing the individual intricacies within immune cells in the context of myocarditis pathogenesis and finding the key intersection of the immune network may help in the diagnosis and treatment of this condition. With the vast amount of cell data gained on myocarditis and the recent application of single-cell sequencing, we summarize the multiple functions of currently recognized key immune cells in the pathogenesis of myocarditis to provide an immune background for subsequent investigations.

A novel mRNA vaccine, TGGT1_278620 mRNA-LNP, prolongs the survival time in BALB/c mice with acute toxoplasmosis

IMPORTANCE

Toxoplasma gondii, an obligate intracellular eukaryotic parasite, can infect about one-third of the world's population. One vaccine, Toxovax, has been developed and licensed commercially; however, it is only used in the sheep industry to reduce the losses caused by congenital toxoplasmosis. Various other vaccine approaches have been explored, including excretory secretion antigen vaccines, subunit vaccines, epitope vaccines, and DNA vaccines. However, current research has not yet developed a safe and effective vaccine for T. gondii. Here, we generated an mRNA vaccine candidate against T. gondii. We investigated the efficacy of vaccination with a novel identified candidate, TGGT1_278620, in a mouse infection model. We screened T. gondii-derived protective antigens at the genome-wide level, combined them with mRNA-lipid nanoparticle vaccine technology against T. gondii, and investigated immune-related factors and mechanisms. Our findings might contribute to developing vaccines for immunizing humans and animals against T. gondii.

Blocking activation of CD4-CD8- T cells modulates their cytotoxic potential and decreases the expression of inflammatory and chemotactic receptors

CD4-CD8- (double negative - DN) T cells represent a small fraction of circulating T lymphocytes but are a major source of pro-inflammatory cytokines in patients with infectious diseases, including chronic Chagas cardiomyopathy (CCC), one of the deadliest cardiopathies known. Chagas disease is caused by an infection with the protozoan parasite Trypanosoma cruzi and can lead to either an asymptomatic form or a high-mortality cardiac disease. While circulating DN T cells represent a major inflammatory cytokine-expressing cell population in Chagas disease, their potential to be recruited to the heart and to perform cytotoxicity has not been determined. Our previous studies showed that blocking DN T cell activation decreases the expression of IFN-gamma, a cytokine involved in the severity of CCC. Here, studying a well-characterized cohort of Chagas patients with CCC or the asymptomatic form of Chagas disease (indeterminate form, IND), we evaluated the expression of cytotoxic molecules, cytokine and chemokine receptors in γδ+ and αβ+ DN T cells by multiparameter flow cytometry, and investigated whether blocking the activation of DN T cells influences the expression of these molecules. We observed that DN T cells from CCC display a higher expression of granzyme A, perforin, inflammatory molecules, and inflammatory chemokine receptors than cells from IND. Messenger RNA coding for these molecules is also upregulated in the heart of CCC patients. Importantly, blocking the activation of DN T cells from CCC modulates their cytotoxic potential and the expression of inflammatory and of chemokine receptors, suggesting that targeting DN T cell activation may be a valid strategy to reduce recruitment to the heart, inflammation, cytotoxicity and, thereby diminish CCC progression and severity.

Nitazoxanide: A Drug Repositioning Compound with Potential Use in Chagas Disease in a Murine Model

Chagas disease (ChD), caused by Trypanosoma cruzi, is the most serious parasitosis in the western hemisphere. Benznidazole and nifurtimox, the only two trypanocidal drugs, are expensive, difficult to obtain, and have severe side effects. Nitazoxanide has shown to be effective against protozoa, bacteria, and viruses. This study aimed to evaluate the nitazoxanide efficacy against the Mexican T. cruzi Ninoa strain in mice. Infected animals were orally treated for 30 days with nitazoxanide (100 mg/kg) or benznidazole (10 mg/kg). The clinical, immunological, and histopathological conditions of the mice were evaluated. Nitazoxanide- or benznidazole-treated mice had longer survival and less parasitemia than those without treatment. Antibody production in the nitazoxanide-treated mice was of the IgG1-type and not of the IgG2-type as in the benznidazole-treated mice. Nitazoxanide-treated mice had significantly high IFN-γ levels compared to the other infected groups. Serious histological damage could be prevented with nitazoxanide treatment compared to without treatment. In conclusion, nitazoxanide decreased parasitemia levels, indirectly induced the production of IgG antibodies, and partially prevented histopathological damage; however, it did not show therapeutic superiority compared to benznidazole in any of the evaluated aspects. Therefore, the repositioning of nitazoxanide as an alternative treatment against ChD could be considered, since it did not trigger adverse effects that worsened the pathological condition of the infected mice.

Genetic Ablation and Pharmacological Blockade of Bradykinin B1 Receptor Unveiled a Detrimental Role for the Kinin System in Chagas Disease Cardiomyopathy

Chagas disease, the parasitic infection caused by Trypanosoma cruzi, afflicts about 6 million people in Latin America. Here, we investigated the hypothesis that T. cruzi may fuel heart parasitism by activating B1R, a G protein-coupled (brady) kinin receptor whose expression is upregulated in inflamed tissues. Studies in WT and B1R^-/- mice showed that T. cruzi DNA levels (15 days post infection-dpi) were sharply reduced in the transgenic heart. FACS analysis revealed that frequencies of proinflammatory neutrophils and monocytes were diminished in B1R^-/- hearts whereas CK-MB activity (60 dpi) was exclusively detected in B1R^+/+ sera. Since chronic myocarditis and heart fibrosis (90 dpi) were markedly attenuated in the transgenic mice, we sought to determine whether a pharmacological blockade of the des-Arg⁹-bradykinin (DABK)/B1R pathway might alleviate chagasic cardiomyopathy. Using C57BL/6 mice acutely infected by a myotropic T. cruzi strain (Colombian), we found that daily treatment (15-60 dpi) with R-954 (B1R antagonist) reduced heart parasitism and blunted cardiac injury. Extending R-954 treatment to the chronic phase (120-160 dpi), we verified that B1R targeting (i) decreased mortality indexes, (ii) mitigated chronic myocarditis, and (iii) ameliorated heart conduction disturbances. Collectively, our study suggests that a pharmacological blockade of the proinflammatory KKS/DABK/B1R pathway is cardioprotective in acute and chronic Chagas disease.

VEGF-A enhances the cytotoxic function of CD4+ cytotoxic T cells via the VEGF-receptor 1/VEGF-receptor 2/AKT/mTOR pathway

BACKGROUND

CD4⁺ cytotoxic T cells (CD4 CTLs) are CD4⁺ T cells with major histocompatibility complex-II-restricted cytotoxic function. Under pathologic conditions, CD4 CTLs hasten the development of autoimmune disease or viral infection by enhancing cytotoxicity. However, the regulators of the cytotoxicity of CD4 CTLs are not fully understood.

METHODS

To explore the potential regulators of the cytotoxicity of CD4 CTLs, bulk RNA and single-cell RNA sequencing (scRNA-seq), enzyme-linked immunosorbent assay, flow cytometry, quantitative PCR, and in-vitro stimulation and inhibition assays were performed.

RESULTS

In this study, we found that VEGF-A promoted the cytotoxicity of CD4 CTLs through scRNA-seq and flow cytometry. Regarding the specific VEGF receptor (R) involved, VEGF-R1/R2 signaling was activated in CD4 CTLs with increased cytotoxicity, and the VEGF-A effects were inhibited when anti-VEGF-R1/R2 neutralizing antibodies were applied. Mechanistically, VEGF-A treatment activated the AKT/mTOR pathway in CD4 CTLs, and the increases of cytotoxic molecules induced by VEGF-A were significantly reduced when the AKT/mTOR pathway was inhibited.

CONCLUSION

In conclusion, VEGF-A enhances the cytotoxicity of CD4 CTLs through the VEGF-R1/VEGF-R2/AKT/mTOR pathway, providing insights for the development of novel treatments for disorders associated with CD4 CTLs.

Chagasic cardiomyopathy is marked by a unique signature of activated CD4+ T cells

Chagas disease is a neglected tropical disease in Latin America and an imported emerging disease worldwide. Chronic Chagas disease cardiomyopathy (CCC) is the most prominent clinical form and can lead to heart failure, thromboembolism, and sudden death. While previous reports have supported a role for CD4⁺ T lymphocytes in the pathogenesis of CCC a comprehensive analysis of these cells during different clinical forms is lacking. Here, we used high-dimensional flow cytometry to assess the diversity of circulating CD4⁺ T cells in patients with distinct clinical forms. We found increased frequencies of CD4⁺CD69⁺ T cells in patients compared to controls. CD39⁺ regulatory T cells, represented by mesocluster 6 were reduced in mild CCC patients compared to controls. Cytotoxic CD4⁺ T cells co-expressing granzyme B and perforin were expanded in patients with Chagas disease and were higher in patients with mild CCC compared to controls. Furthermore, patients with mild CCC displayed higher frequencies of multifunctional effector memory CD4⁺ T cells. Our results demonstrate an expansion in activated CD4⁺ T cells and a decrease in a functional subset of regulatory T cells associated with the onset of Chagas cardiomyopathy, suggesting their role in the establishment of cardiac lesions and as potential biomarkers for disease aggravation.