HTLV-1 induces an inflammatory CD4+CD8+ T cell population in HTLV-1-associated myelopathy.

Human T cell leukemia virus type 1 (HTLV-1) is a retrovirus with preferential CD4+ T cell tropism that causes a range of conditions spanning from asymptomatic infection to adult T cell leukemia and HTLV-1-associated myelopathy (HAM), an inflammatory disease of the CNS. The mechanisms by which HTLV-1 induces HAM are poorly understood. By directly examining the ex vivo phenotype and function of T cells from asymptomatic carriers and patients with HAM, we show that patients with HAM have a higher frequency of CD4+CD8+ double-positive (DP) T cells, which are infected with HTLV-1 at higher rates than CD4+ T cells. Displaying both helper and cytotoxic phenotypes, these DP T cells are highly proinflammatory and contain high frequencies of HTLV-1-specific cells. Mechanistically, we demonstrate that DP T cells arise by direct HTLV-1 infection of CD4+ and CD8+ T cells. High levels of CD49d and CXCR3 expression suggest that DP T cells possess the ability to migrate to the CNS, and when cocultured with astrocytes, DP T cells induce proinflammatory astrocytes that express high levels of CXCL10, IFN-γ, and IL-6. These results demonstrate the potential of DP T cells to directly contribute to CNS pathology.

Transcriptional reprogramming from innate immune functions to a pro-thrombotic signature by monocytes in COVID-19.

Although alterations in myeloid cells have been observed in COVID-19, the specific underlying mechanisms are not completely understood. Here, we examine the function of classical CD14+ monocytes in patients with mild and moderate COVID-19 during the acute phase of infection and in healthy individuals. Monocytes from COVID-19 patients display altered expression of cell surface receptors and a dysfunctional metabolic profile that distinguish them from healthy monocytes. Secondary pathogen sensing ex vivo leads to defects in pro-inflammatory cytokine and type-I IFN production in moderate COVID-19 cases, together with defects in glycolysis. COVID-19 monocytes switch their gene expression profile from canonical innate immune to pro-thrombotic signatures and are functionally pro-thrombotic, both at baseline and following ex vivo stimulation with SARS-CoV-2. Transcriptionally, COVID-19 monocytes are characterized by enrichment of pathways involved in hemostasis, immunothrombosis, platelet aggregation and other accessory pathways to platelet activation and clot formation. These results identify a potential mechanism by which monocyte dysfunction may contribute to COVID-19 pathology.

Separation of the CaV 1.2-CaV 1.3 calcium channel duo prevents type 2 allergic airway inflammation.

BACKGROUND: Voltage-gated calcium (Cav 1) channels contribute to T-lymphocyte activation. Cav 1.2 and Cav 1.3 channels are expressed in Th2 cells but their respective roles are unknown, which is investigated herein. METHODS: We generated mice deleted for Cav 1.2 in T cells or Cav 1.3 and analyzed TCR-driven signaling. In this line, we developed original fast calcium imaging to measure early elementary calcium events (ECE). We also tested the impact of Cav 1.2 or Cav 1.3 deletion in models of type 2 airway inflammation. Finally, we checked whether the expression of both Cav 1.2 and Cav 1.3 in T cells from asthmatic children correlates with Th2-cytokine expression. RESULTS: We demonstrated non-redundant and synergistic functions of Cav 1.2 and Cav 1.3 in Th2 cells. Indeed, the deficiency of only one channel in Th2 cells triggers TCR-driven hyporesponsiveness with weakened tyrosine phosphorylation profile, a strong decrease in initial ECE and subsequent reduction in the global calcium response. Moreover, Cav 1.3 has a particular role in calcium homeostasis. In accordance with the singular roles of Cav 1.2 and Cav 1.3 in Th2 cells, deficiency in either one of these channels was sufficient to inhibit cardinal features of type 2 airway inflammation. Furthermore, Cav 1.2 and Cav 1.3 must be co-expressed within the same CD4+ T cell to trigger allergic airway inflammation. Accordingly with the concerted roles of Cav 1.2 and Cav 1.3, the expression of both channels by activated CD4+ T cells from asthmatic children was associated with increased Th2-cytokine transcription. CONCLUSIONS: Thus, Cav 1.2 and Cav 1.3 act as a duo, and targeting only one of these channels would be efficient in allergy treatment.