A quest for universal anti-SARS-CoV-2 T cell assay: systematic review, meta-analysis, and experimental validation.

Measuring SARS-CoV-2-specific T cell responses is crucial to understanding an individual's immunity to COVID-19. However, high inter- and intra-assay variability make it difficult to define T cells as a correlate of protection against COVID-19. To address this, we performed systematic review and meta-analysis of 495 datasets from 94 original articles evaluating SARS-CoV-2-specific T cell responses using three assays - Activation Induced Marker (AIM), Intracellular Cytokine Staining (ICS), and Enzyme-Linked Immunospot (ELISPOT), and defined each assay's quantitative range. We validated these ranges using samples from 193 SARS-CoV-2-exposed individuals. Although IFNγ ELISPOT was the preferred assay, our experimental validation suggested that it under-represented the SARS-CoV-2-specific T cell repertoire. Our data indicate that a combination of AIM and ICS or FluoroSpot assay would better represent the frequency, polyfunctionality, and compartmentalization of the antigen-specific T cell responses. Taken together, our results contribute to defining the ranges of antigen-specific T cell assays and propose a choice of assay that can be employed to better understand the cellular immune response against viral diseases.

Fangchinoline inhibits SARS-CoV-2 and MERS-CoV entry.

The COVID-19 pandemic caused by SARS-CoV-2, lead to mild to severe respiratory illness and resulted in 6.9 million deaths worldwide. Although vaccines are effective in preventing COVID-19, they may not be sufficient to protect immunocompromised individuals from this respiratory illness. Moreover, novel emerging variants of SARS-CoV-2 pose a risk of new COVID-19 waves. Therefore, identification of effective antivirals is critical in controlling SARS and other coronaviruses, such as MERS-CoV. We show that Fangchinoline (Fcn), a bisbenzylisoquinoline alkaloid, inhibits replication of SARS-CoV, SARS-CoV-2, and MERS-CoV in a range of in vitro assays, by blocking entry. Therapeutic use of Fcn inhibited viral loads in the lungs, and suppressed associated airway inflammation in hACE2. Tg mice and Syrian hamster infected with SARS-CoV-2. Combination of Fcn with remdesivir (RDV) or an anti-leprosy drug, Clofazimine, exhibited synergistic antiviral activity. Compared to Fcn, its synthetic derivative, MK-04-003, more effectively inhibited SARS-CoV-2 and its variants B.1.617.2 and BA.5 in mice. Taken together these data demonstrate that Fcn is a pan beta coronavirus inhibitor, which possibly can be used to combat novel emerging coronavirus diseases.

Emerging Roles of Th9 Cells as an Anti-tumor Helper T Cells.

The newly discovered Th9 cells are the distinct subset of CD4+ T helper (Th) cells, which are involved in various pathophysiological conditions of an immune response. In addition to its role in allergic inflammation and elimination of extracellular pathogens, Th9 cells were found to play a key role in inducing anti-tumor immune response. Precisely, the anti-tumor functions of Th9 cells were found to be superior as compared to Th1 and other Th subsets. Th9 cells eliminate tumors via activating innate and adaptive immune cells, and in particular, generating a profound effector cytotoxic T lymphocyte (CTL) response against neo antigens. In addition, it was proposed that Th9 cells were found to induce effector functions of innate cells like dendritic cells, mast cells and NK cells, which further promote a robust anti-tumor immune response. In this review, we highlight the recent advances in differentiation and functions of Th9 cells in anti-tumor immunity.

A transgenic model of central nervous system autoimmunity mediated by CD4+ and CD8+ T and B cells.

Experimental autoimmune encephalomyelitis (EAE) is a widely used model of multiple sclerosis. In NOD mice, EAE develops as a relapsing-remitting disease that transitions to a chronic progressive disease, making the NOD model the only mouse model that recapitulates the full clinical disease course observed in most multiple sclerosis patients. We have generated a TCR transgenic mouse that expresses the α- and ß-chains of a myelin oligodendrocyte glycoprotein (MOG) 35-55-reactive TCR (1C6) on the NOD background. 1C6 TCR transgenic mice spontaneously generate both CD4(+) and CD8(+) T cells that recognize MOG and produce proinflammatory cytokines, allowing for the first time to our knowledge the simultaneous examination of myelin-reactive CD4(+) and CD8(+) T cells in the same host. 1C6 CD8(+) T cells alone can induce optic neuritis and mild EAE with delayed onset; however, 1C6 CD4(+) T cells alone induce severe EAE and predominate in driving disease when both cell types are present. When 1C6 mice are crossed with mice bearing an IgH specific for MOG, the mice develop spontaneous EAE with high incidence, but surprisingly the disease pattern does not resemble the neuromyelitis optica-like disease observed in mice bearing CD4(+) T cells and B cells reactive to MOG on the C57BL/6 background. Collectively, our data show that although myelin-reactive CD8(+) T cells contribute to disease, disease is primarily driven by myelin-reactive CD4(+) T cells and that the coexistence of myelin-reactive T and B cells does not necessarily result in a distinct pathological phenotype.

Tim-3/galectin-9 pathway: regulation of Th1 immunity through promotion of CD11b+Ly-6G+ myeloid cells.

IFN-gamma plays a central role in antitumor immunity. T cell Ig and mucin domain (Tim-3) is expressed on IFN-gamma-producing Th1 cells; on interaction with its ligand, galectin-9, Th1 immunity is terminated. In this study, we show that transgenic overexpression of Tim-3 on T cells results in an increase in CD11b(+)Ly-6G(+) cells and inhibition of immune responses. Molecular characterization of CD11b(+)Ly-6G(+) cells reveals a phenotype consistent with granulocytic myeloid-derived suppressor cells. Accordingly, we find that modulation of the Tim-3/galectin-9 (Gal-9) pathway impacts on tumor growth. Similarly, overexpression of Tim-3 ligand, Gal-9, results in an increase in CD11b(+)Ly-6G(+) cells and inhibition of immune responses. Loss of Tim-3 restores normal levels of CD11b(+)Ly-6G(+) cells and normal immune responses in Gal-9 transgenic mice. Our data uncover a novel mechanism by which the Tim-3/Gal-9 pathway regulates immune responses and identifies this pathway as a therapeutic target in diseases where myeloid-derived suppressor cells are disadvantageous.

Cutting edge: the Idd3 genetic interval determines regulatory T cell function through CD11b+CD11c- APC.

The Idd3 genetic interval confers protection against multiple autoimmune diseases, including type 1 diabetes and experimental autoimmune encephalomyelitis. The favored candidate gene in this interval is Il2, which is polymorphic between susceptible and resistant strains of mice. IL-2 regulates the growth/death of effector T cells as well as the generation/maintenance of regulatory T cells (Tregs), and recent studies have shown that NOD.Idd3 Tregs are more suppressive than their NOD counterparts. We have further dissected the mechanisms underlying the differential suppression by NOD and NODxIdd3 Tregs and find that it is determined by CD11b(+)CD11c(-) APCs. Thus, contrary to what might be expected, our data suggest that the differential suppressive activity of NOD and NODxIdd3 Tregs is not due to an effect of the Idd3 genetic interval on T cells but rather is due to differences in the APC compartment.

Chondroprotective Potential of Fruit Extracts of Phyllanthus emblica in Osteoarthritis.

There is a need for effective nutraceuticals for osteoarthritis care. The fruit of Phyllanthus emblica is used as a powerful rejuvenator in Ayurvedic medicine. This study measured the chondroprotective potential of P. emblica ('Amalaki') fruits in vitro. We used aqueous extracts of unprocessed P. emblica fruit powder (powder A), and the powder obtained after hot water extraction and drying of powder A (powder B). Chondroprotection was measured in three different assay systems. First, we tested the effects of both fruit powders on the activities of the enzymes hyaluronidase and collagenase type 2. Second, an in vitro model of cartilage degradation was set-up with explant cultures of articular knee cartilage from osteoarthritis patients. Cartilage damage was assayed by measuring glycosaminoglycan release from explants treated with/without P. emblica fruit powders. Aqueous extracts of both fruit powders significantly inhibited the activities of hyaluronidase and collagenase type 2 in vitro. Third, in the explant model of cartilage matrix damage, extracts of glucosamine sulphate and powder B (0.05 mg/ml) exhibited statistically significant, long-term chondroprotective activity in cartilage explants from 50% of the patients tested. This result is important since glucosamine sulphate is the leading nutraceutical for osteoarthritis. Powder A induced a statistically significant, short-term chondroprotective activity in cartilage explants from all of the patients tested. This is the first study to identify and quantitate new chondroprotective activities of P. emblica fruits. These data provide pilot pre-clinical evidence for the use of P. emblica fruits as a chondroprotective agent in osteoarthritis therapy.

The relationship between chondroprotective and antiinflammatory effects of Withania somnifera root and glucosamine sulphate on human osteoarthritic cartilage in vitro.

Using a validated explant model of in vitro cartilage damage, the effects of aqueous extracts of Withania somnifera (Ashwagandha) root and glucosamine sulphate (GlcS) were tested on the levels of nitric oxide (NO) and glycosaminoglycans (GAGs) secreted by knee cartilage from chronic osteoarthritis (OA) patients. W. somnifera extracts significantly decreased NO release by explants from one subset of patients (antiinflammatory response) and significantly increased levels of NO and GAGs released by explants from the second subset ('non-responders'). This is the first study showing direct, statistically significant, antiinflammatory effects of W. somnifera on human OA cartilage. It also confirmed that glucosamine sulphate exhibited statistically significant, antiinflammatory and chondroprotective activities in human OA cartilage. However, these beneficial effects of GlcS were observed in cartilage explants from 50% of patients tested ('responders'). In contrast, glucosamine significantly increased secretion of NO but not GAGs in explants from the second subset of OA patients ('non-responders'). Cartilage explants from the 11 OA patients gave differential responses to both drugs. Patient samples which responded to the antiinflammatory effects of W. somnifera did not always give a similar response to glucosamine, and vice versa. Thus, this in vitro model of human cartilage damage provides qualitative and statistically significant, quantitative pre-clinical data on antiinflammatory and chondroprotective activities of antiarthritic drugs.

Promotion of tissue inflammation by the immune receptor Tim-3 expressed on innate immune cells.

CD4+ T helper 1 (TH1) cells are important mediators of inflammation and are regulated by numerous pathways, including the negative immune receptor Tim-3. We found that Tim-3 is constitutively expressed on cells of the innate immune system in both mice and humans, and that it can synergize with Toll-like receptors. Moreover, an antibody agonist of Tim-3 acted as an adjuvant during induced immune responses, and Tim-3 ligation induced distinct signaling events in T cells and dendritic cells; the latter finding could explain the apparent divergent functions of Tim-3 in these cell types. Thus, by virtue of differential expression on innate versus adaptive immune cells, Tim-3 can either promote or terminate TH1 immunity and may be able to influence a range of inflammatory conditions.

Hyaluronidase and collagenase inhibitory activities of the herbal formulation Triphala guggulu.

Myrrh (guggulu) oleoresin from the Commiphora mukul tree is an important component of antiarthritic drugs in Ayurvedic medicine. Clinical data suggest that elevated levels of hyaluronidase and collagenase type 2 enzymes contribute significantly to cartilage degradation. Triphala guggulu (TG) is a guggulu-based formulation used for the treatment of arthritis. We assessed the chondroprotective potential of TG by examining its effects on the activities of pure hyaluronidase and collagenase type 2 enzymes. Triphala shodith guggulu (TSG), an intermediate in the production of TG, was also examined. A spectrophotometric method was used to assay Hyaluronidase activity, and to detect potential Hyaluronidase inhibitors. Aqueous and hydro-alcoholic extracts of TSG showed weak but dose-dependent inhibition of hyaluronidase activity. In contrast, the TG formulation was 50 times more potent than the TSG extract with respect to hyaluronidase inhibitory activity. A validated X-ray film-based assay was used to measure the gelatinase activity of pure collagenase type 2. Hydro-alcoholic extracts of the TG formulation were 4 times more potent than TSG with respect to collagenase inhibitory activity. Components of Triphala were also evaluated for their inhibitory activities on hyaluronidase and collagenase. This is the first report to show that the T2 component of Triphala (T.chebula) is a highly potent hyaluronidase and collagenase inhibitor. Thus, the TG formulation inhibits two major enzymes that can degrade cartilage matrix. Our study provides the first in vitro preclinical evidence of the chondroprotective properties of TG.