Common variable immunodeficiency (CVID) is characterized by defective B cell function, impaired antibody production, and increased susceptibility to bacterial infections. Here, we addressed the hypothesis that poor antibody-mediated immune control of infections may result in substantial perturbations in the T cell compartment. Newly diagnosed CVID patients were sampled before, and 6–12 months after, initiation of intravenous immunoglobulin (IVIg) therapy. Treatment-naïve CVID patients displayed suppressed CD4 T cell counts and myeloid dendritic cell (mDC) levels, as well as high levels of immune activation in CD8 T cells, CD4 T cells, and invariant natural killer T (iNKT) cells. Expression of co-stimulatory receptors CD80 and CD83 was elevated in mDCs and correlated with T cell activation. Levels of both FoxP3+ T regulatory (Treg) cells and iNKT cells were low, whereas soluble CD14 (sCD14), indicative of monocyte activation, was elevated. Importantly, immune reconstitution treatment with IVIg partially restored the CD4 T cell and mDC compartments. Treatment furthermore reduced the levels of CD8 T cell activation and mDC activation, whereas levels of Treg cells and iNKT cells remained low. Thus, primary deficiency in humoral immunity with impaired control of microbial infections is associated with significant pathological changes in cell-mediated immunity. Furthermore, therapeutic enhancement of humoral immunity with IVIg infusions alleviates several of these defects, indicating a relationship between poor antibody-mediated immune control of infections and the occurrence of abnormalities in the T cell and mDC compartments. These findings help our understanding of the immunopathogenesis of primary immunodeficiency, as well as acquired immunodeficiency caused by HIV-1 infection.

BackgroundSevere dengue virus (DENV) disease is associated with extensive immune activation, characterized by a cytokine storm. Previously, elevated lipopolysaccharide (LPS) levels in dengue were found to correlate with clinical disease severity. In the present cross-sectional study we identified markers of microbial translocation and immune activation, which are associated with severe manifestations of DENV infection.MethodsSerum samples from DENV-infected patients were collected during the outbreak in 2010 in the State of São Paulo, Brazil. Levels of LPS, lipopolysaccharide binding protein (LBP), soluble CD14 (sCD14) and IgM and IgG endotoxin core antibodies were determined by ELISA. Thirty cytokines were quantified using a multiplex luminex system. Patients were classified according to the 2009 WHO classification and the occurrence of plasma leakage/shock and hemorrhage. Moreover, a (non-supervised) cluster analysis based on the expression of the quantified cytokines was applied to identify groups of patients with similar cytokine profiles. Markers of microbial translocation were linked to groups with similar clinical disease severity and clusters with similar cytokine profiles.ResultsCluster analysis indicated that LPS levels were significantly increased in patients with a profound pro-inflammatory cytokine profile. LBP and sCD14 showed significantly increased levels in patients with severe disease in the clinical classification and in patients with severe inflammation in the cluster analysis. With both the clinical classification and the cluster analysis, levels of IL-6, IL-8, sIL-2R, MCP-1, RANTES, HGF, G-CSF and EGF were associated with severe disease.ConclusionsThe present study provides evidence that both microbial translocation and extensive immune activation occur during severe DENV infection and may play an important role in the pathogenesis.

In late 2019, a novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) emerged in Wuhan, China. SARS‐CoV‐2 and the disease it causes, coronavirus disease 2019 (COVID‐19), spread rapidly and became a global pandemic in early 2020. SARS‐CoV‐2 spike protein is responsible for viral entry and binds to angiotensin converting enzyme 2 (ACE2) on host cells, making it a major target of the immune system – particularly neutralizing antibodies (nAbs) that are induced by infection or vaccines. Extracellular vesicles (EVs) are small membraned particles constitutively released by cells, including virally‐infected cells. EVs and viruses enclosed within lipid membranes share some characteristics: they are small, sub‐micron particles and they overlap in cellular biogenesis and egress routes. Given their shared characteristics, we hypothesized that EVs released from spike‐expressing cells could carry spike and serve as decoys for anti‐spike nAbs, promoting viral infection. Here, using mass spectrometry and nanoscale flow cytometry (NFC) approaches, we demonstrate that SARS‐CoV‐2 spike protein can be incorporated into EVs. Furthermore, we show that spike‐carrying EVs act as decoy targets for convalescent patient serum‐derived nAbs, reducing their effectiveness in blocking viral entry. These findings have important implications for the pathogenesis of SARS‐CoV‐2 infection in vivo and highlight the complex interplay between viruses, extracellular vesicles, and the immune system that occurs during viral infections.

Characterization of a novel monocyte subset that suppresses CD8+ proliferation during HIV and SIV infection.