Distinct SARS-CoV-2 specific NLRP3 and IL-1β responses in T cells of aging patients during acute COVID-19 infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes Coronavirus Disease 2019 (COVID-19) that presents with varied clinical manifestations ranging from asymptomatic or mild infections and pneumonia to severe cases associated with cytokine storm, acute respiratory distress syndrome (ARDS), and even death. The underlying mechanisms contributing to these differences are unclear, although exacerbated inflammatory sequelae resulting from infection have been implicated. While advanced aging is a known risk factor, the precise immune parameters that determine the outcome of SARS-CoV-2 infection in elderly individuals are not understood. Here, we found aging-associated (age ≥61) intrinsic changes in T cell responses when compared to those from individuals aged ≤ 60, even among COVID-positive patients with mild symptoms. Specifically, when stimulated with SARS-CoV-2 peptides in vitro, peripheral blood mononuclear cell (PBMC) CD4+ and CD8+ T cells from individuals aged ≥61 showed a diminished capacity to produce IFN-γ and IL-1β. Although they did not have severe disease, aged individuals also showed a higher frequency of PD-1+ cells and significantly diminished IFN-γ/PD-1 ratios among T lymphocytes upon SARS-CoV-2 peptide stimulation. Impaired T cell IL-1β expression coincided with reduced NLRP3 levels in T lymphocytes. However, the expression of these molecules was not affected in the monocytes of individuals aged ≥61. Together, these data reveal SARS-CoV-2-specific CD4+ and CD8+ T-cell intrinsic cytokine alterations in the individuals older than 61 and may provide new insights into dysregulated COVID-directed immune responses in the elderly

TIM3 Mediates T Cell Exhaustion during Mycobacterium tuberculosis Infection

While T cell immunity initially limits Mycobacterium tuberculosis infection, why T cell immunity fails to sterilize the infection and allows recrudescence is not clear. One hypothesis is that T cell exhaustion impairs immunity and is detrimental to the outcome of M. tuberculosis infection. Here we provide functional evidence for the development T cell exhaustion during chronic TB. Second, we evaluate the role of the inhibitory receptor T cell immunoglobulin and mucin domain–containing-3 (TIM3) during chronic M. tuberculosis infection. We find that TIM3 expressing T cells accumulate during chronic infection, co-express other inhibitory receptors including PD1, produce less IL-2 and TNF but more IL-10, and are functionally exhausted. Finally, we show that TIM3 blockade restores T cell function and improves bacterial control, particularly in chronically infected susceptible mice. These data show that T cell immunity is suboptimal during chronic M. tuberculosis infection due to T cell exhaustion. Moreover, in chronically infected mice, treatment with anti-TIM3 mAb is an effective therapeutic strategy against tuberculosis

Tim3 binding to galectin-9 stimulates antimicrobial immunity

The interaction between Tim3 on Th1 cells and galectin-9 on Mycobacterium tuberculosis–infected macrophages restricts the bacterial growth by stimulating caspase-1–dependent IL-1β secretion

Fungal Colonization and Infections—Interactions with Other Human Diseases

Candida albicans is a commensal fungus that asymptomatically colonizes the skin and mucosa of 60% of healthy individuals. Breaches in the cutaneous and mucosal barriers trigger candidiasis that ranges from asymptomatic candidemia and mucosal infections to fulminant sepsis with 70% mortality rates. Fungi influence at least several diseases, in part by mechanisms such as the production of pro-carcinogenic agents, molecular mimicking, and triggering of the inflammation cascade. These processes impact the interactions among human pathogenic and resident fungi, the bacteriome in various organs/tissues, and the host immune system, dictating the outcomes of invasive infections, metabolic diseases, and cancer. Although mechanistic investigations are at stages of infancy, recent studies have advanced our understanding of host–fungal interactions, their role in immune homeostasis, and their associated pathologies. This review summarizes the role of C. albicans and other opportunistic fungi, specifically their association with various diseases, providing a glimpse at the recent developments and our current knowledge in the context of inflammatory-bowel disease (IBD), cancers, and COVID-19. Two of the most common human diseases where fungal interactions have been previously well-studied are cancer and IBD. Here we also discuss the emerging role of fungi in the ongoing and evolving pandemic of COVID-19, as it is relevant to current health affairs

iNKT cell production of GM-CSF controls Mycobacterium tuberculosis

Invariant natural killer T (iNKT) cells are activated during infection, but how they limit microbial growth is unknown in most cases. We investigated how iNKT cells suppress intracellular Mycobacterium tuberculosis (Mtb) replication. When co-cultured with infected macrophages, iNKT cell activation, as measured by CD25 upregulation and IFNγ production, was primarily driven by IL-12 and IL-18. In contrast, iNKT cell control of Mtb growth was CD1d-dependent, and did not require IL-12, IL-18, or IFNγ. This demonstrated that conventional activation markers did not correlate with iNKT cell effector function during Mtb infection. iNKT cell control of Mtb replication was also independent of TNF and cell-mediated cytotoxicity. By dissociating cytokine-driven activation and CD1d-restricted effector function, we uncovered a novel mediator of iNKT cell antimicrobial activity: GM-CSF. iNKT cells produced GM-CSF in vitro and in vivo in a CD1d-dependent manner during Mtb infection, and GM-CSF was both necessary and sufficient to control Mtb growth. Here, we have identified GM-CSF production as a novel iNKT cell antimicrobial effector function and uncovered a potential role for GM-CSF in T cell immunity against Mtb.This work was supported by National Institutes of Health (NIH) R01HL080330 to SMB, T32AR007530 supporting ACR, the American Lung Association postdoctoral research training fellowship, RT-123085-N, and Harvard University Center for AIDS Research (CFAR) Scholar Award, an NIH funded program, P30 AI060354, to PJ, and a PhD fellowship from Fundacao para a Ciencia e Tecnologia (Portugal) to CNA. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Microbiome Dependent Regulation of T and Th17 Cells in Mucosa.

Mammals co-exist with resident microbial ecosystem that is composed of an incredible number and diversity of bacteria, viruses and fungi. Owing to direct contact between resident microbes and mucosal surfaces, both parties are in continuous and complex interactions resulting in important functional consequences. These interactions govern immune homeostasis, host response to infection, vaccination and cancer, as well as predisposition to metabolic, inflammatory and neurological disorders. Here, we discuss recent studies on direct and indirect effects of resident microbiota on regulatory T cells (Tregs) and Th17 cells at the cellular and molecular level. We review mechanisms by which commensal microbes influence mucosa in the context of bioactive molecules derived from resident bacteria, immune senescence, chronic inflammation and cancer. Lastly, we discuss potential therapeutic applications of microbiota alterations and microbial derivatives, for improving resilience of mucosal immunity and combating immunopathology

The antimicrobial effector function of iNKT cells is a soluble factor.

<p>Transwell CFU assay for H37Rv-infected WT mϕ in a 24-well plate with either WT or IFNγ^−/− iNKT cells added directly (cis) or 0.4 µm transwell inserts with WT or IFNγ^−/− iNKT cells in the presence of uninfected WT mϕ (trans) added on d1. Error bars indicate mean ± SEM. *P<0.05, **P<0.01 (One-way ANOVA with Dunnet's post-test, compared to d5 untreated mϕ.) Data are representative of two independent experiments with four replicates each.</p

IFNγ-independent antimicrobial effector function of iNKT cells is independent of cytolytic activity.

<p>(A–D) CFU assay d1, d5, and/or d7 post-infection with H37Rv-infected WT mϕ (A, C), Fas^−/− mϕ (B), or TNFR1/2^−/− mϕ (D) with WT iNKT cells (A, B, D), IFNγ^−/− iNKT cells (B–D), or Prf^−/− iNKT cells (A) added on d1 post infection at a 1∶1 ratio. (C) H37Rv-infected mϕ were treated with 0.1–10 µM of caspase-3 inhibitor peptide (Z-DEVD-FMK) 2 hours prior to addition of iNKT cells. Error bars indicate mean ± SEM. *P<0.05, **P<0.01 (One-way ANOVA with Dunnet's post-test, compared to d5 or d7 untreated mϕ.) Data are representative of three (A, C, D) or two (B) independent experiments with three or more replicates.</p

iNKT cell mediated control is CD1d-dependent but does not require IL-12 or IL-18.

<p>(A) Colony forming unit (CFU) assay measuring Mtb bacterial growth in H37Rv-infected WT mϕ on d1 and d5 post-infection. iNKT cells, anti-IL-12p40, anti-IL-18 blocking or isotype control antibodies were added on d1 after infection. (B) CFU assay d1 and d5 post-infection for H37Rv-infected MyD88^−/− mϕ with iNKT cells added on d1. (C, E) CFU assay d1 and d5 post-infection for H37Rv-infected WT and CD1d^−/− mϕ with iNKT cells added on d1 at a ratio of 1∶1 (C) or HMNC at a ratio of 3∶1 (E). (D) Compiled data from 6 independent experiments as described in (C). (F) H37Rv-infected mϕ after 24 hours. CD1d MFI fold change over uninfected mϕ either without or with iNKT cells. Error bars indicate mean ± SEM. *P<0.05, **P<0.01, ***P<0.001 (One-way ANOVA with Dunnet's post-test, compared to d5 untreated mϕ). +++P<.001 (unpaired Student's t-test). Data are representative of two (A, B) six (C, D), and one (E) independent experiment(s) with three or more replicates, or more than 12 independent experiments (F).</p

iNKT cells are activated by Mtb-infected mϕ.

<p>(A) iNKT cells were cultured either alone, with uninfected thioglycollate-elicited peritoneal mϕ, or H37Rv-infected mϕ for 24 hours. Cells were stained for CD69 and CD25 and mϕ were distinguished from iNKT cells by F4/80 staining. (B) Fold change in CD69 and CD25 MFI on iNKT cells cultured with uninfected or H37Rv-infected mϕ compared to iNKT cells alone. Supernatant was harvested at 24 hours and IFNγ measured by ELISA. Error bars indicate mean ± SEM. *P<.05, **P<.01, ***P<.001. (One-way ANOVA with Dunnet's post-test, compared to iNKT cells alone). Data are representative of eight independent experiments. Mϕ, macrophage; UI, uninfected; , MOI titration, 1.5∶1, 3∶1, 6∶1.</p