Publisher Correction: Group 3 innate lymphoid cells mediate early protective immunity against tuberculosis.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Group 3 innate lymphoid cells mediate early protective immunity against tuberculosis.

Tuberculosis is the leading cause of death by an infectious disease worldwide1. However, the involvement of innate lymphoid cells (ILCs) in immune responses to infection with Mycobacterium tuberculosis (Mtb) is unknown. Here we show that circulating subsets of ILCs are depleted from the blood of participants with pulmonary tuberculosis and restored upon treatment. Tuberculosis increased accumulation of ILC subsets in the human lung, coinciding with a robust transcriptional response to infection, including a role in orchestrating the recruitment of immune subsets. Using mouse models, we show that group 3 ILCs (ILC3s) accumulated rapidly in Mtb-infected lungs and coincided with the accumulation of alveolar macrophages. Notably, mice that lacked ILC3s exhibited a reduction in the accumulation of early alveolar macrophages and decreased Mtb control. We show that the C-X-C motif chemokine receptor 5 (CXCR5)-C-X-C motif chemokine ligand 13 (CXCL13) axis is involved in Mtb control, as infection upregulates CXCR5 on circulating ILC3s and increases plasma levels of its ligand, CXCL13, in humans. Moreover, interleukin-23-dependent expansion of ILC3s in mice and production of interleukin-17 and interleukin-22 were found to be critical inducers of lung CXCL13, early innate immunity and the formation of protective lymphoid follicles within granulomas. Thus, we demonstrate an early protective role for ILC3s in immunity to Mtb infection.

Slow progression of pediatric HIV associates with early CD8+ T cell PD-1 expression and a stem-like phenotype.

HIV nonprogression despite persistent viremia is rare among adults who are naive to antiretroviral therapy (ART) but relatively common among ART-naive children. Previous studies indicate that ART-naive pediatric slow progressors (PSPs) adopt immune evasion strategies similar to those described in natural hosts of SIV. However, the mechanisms underlying this immunophenotype are not well understood. In a cohort of early-treated infants who underwent analytical treatment interruption (ATI) after 12 months of ART, expression of PD-1 on CD8+ T cells immediately before ATI was the main predictor of slow progression during ATI. PD-1+CD8+ T cell frequency was also negatively correlated with CCR5 and HLA-DR expression on CD4+ T cells and predicted stronger HIV-specific T lymphocyte responses. In the CD8+ T cell compartment of PSPs, we identified an enrichment of stem-like TCF-1+PD-1+ memory cells, whereas pediatric progressors and viremic adults had a terminally exhausted PD-1+CD39+ population. TCF-1+PD-1+ expression on CD8+ T cells was associated with higher proliferative activity and stronger Gag-specific effector functionality. These data prompted the hypothesis that the proliferative burst potential of stem-like HIV-specific cytotoxic cells could be exploited in therapeutic strategies to boost the antiviral response and facilitate remission in infants who received early ART with a preserved and nonexhausted T cell compartment.

HIV specific CD8+ TRM-like cells in tonsils express exhaustive signatures in the absence of natural HIV control.

Lymphoid tissues are an important HIV reservoir site that persists in the face of antiretroviral therapy and natural immunity. Targeting these reservoirs by harnessing the antiviral activity of local tissue-resident memory (TRM) CD8+ T-cells is of great interest, but limited data exist on TRM-like cells within lymph nodes of people living with HIV (PLWH). Here, we studied tonsil CD8+ T-cells obtained from PLWH and uninfected controls from South Africa. We show that these cells are preferentially located outside the germinal centers (GCs), the main reservoir site for HIV, and display a low cytolytic and a transcriptionally TRM-like profile distinct from blood CD8+ T-cells. In PLWH, CD8+ TRM-like cells are expanded and adopt a more cytolytic, activated, and exhausted phenotype not reversed by antiretroviral therapy (ART). This phenotype was enhanced in HIV-specific CD8+ T-cells from tonsils compared to matched blood suggesting a higher antigen burden in tonsils. Single-cell transcriptional and clonotype resolution showed that these HIV-specific CD8+ T-cells in the tonsils express heterogeneous signatures of T-cell activation, clonal expansion, and exhaustion ex-vivo. Interestingly, this signature was absent in a natural HIV controller, who expressed lower PD-1 and CXCR5 levels and reduced transcriptional evidence of T-cell activation, exhaustion, and cytolytic activity. These data provide important insights into lymphoid tissue-derived HIV-specific CD8+ TRM-like phenotypes in settings of HIV remission and highlight their potential for immunotherapy and targeting of the HIV reservoirs.

Tissue-resident-like CD4+ T cells secreting IL-17 control Mycobacterium tuberculosis in the human lung.

T cell immunity is essential for the control of tuberculosis (TB), an important disease of the lung, and is generally studied in humans using peripheral blood cells. Mounting evidence, however, indicates that tissue-resident memory T cells (Trms) are superior at controlling many pathogens, including Mycobacterium tuberculosis (M. tuberculosis), and can be quite different from those in circulation. Using freshly resected lung tissue, from individuals with active or previous TB, we identified distinct CD4+ and CD8+ Trm-like clusters within TB-diseased lung tissue that were functional and enriched for IL-17-producing cells. M. tuberculosis-specific CD4+ T cells producing TNF-α, IL-2, and IL-17 were highly expanded in the lung compared with matched blood samples, in which IL-17+ cells were largely absent. Strikingly, the frequency of M. tuberculosis-specific lung T cells making IL-17, but not other cytokines, inversely correlated with the plasma IL-1ß levels, suggesting a potential link with disease severity. Using a human granuloma model, we showed the addition of either exogenous IL-17 or IL-2 enhanced immune control of M. tuberculosis and was associated with increased NO production. Taken together, these data support an important role for M. tuberculosis-specific Trm-like, IL-17-producing cells in the immune control of M. tuberculosis in the human lung.

HIV infection drives interferon signaling within intestinal SARS-CoV-2 target cells.

SARS-CoV-2 infects epithelial cells of the human gastrointestinal (GI) tract and causes related symptoms. HIV infection impairs gut homeostasis and is associated with an increased risk of COVID-19 fatality. To investigate the potential link between these observations, we analyzed single-cell transcriptional profiles and SARS-CoV-2 entry receptor expression across lymphoid and mucosal human tissue from chronically HIV-infected individuals and uninfected controls. Absorptive gut enterocytes displayed the highest coexpression of SARS-CoV-2 receptors ACE2, TMPRSS2, and TMPRSS4, of which ACE2 expression was associated with canonical interferon response and antiviral genes. Chronic treated HIV infection was associated with a clear antiviral response in gut enterocytes and, unexpectedly, with a substantial reduction of ACE2 and TMPRSS2 target cells. Gut tissue from SARS-CoV-2-infected individuals, however, showed abundant SARS-CoV-2 nucleocapsid protein in both the large and small intestine, including an HIV-coinfected individual. Thus, upregulation of antiviral response genes and downregulation of ACE2 and TMPRSS2 in the GI tract of HIV-infected individuals does not prevent SARS-CoV-2 infection in this compartment. The impact of these HIV-associated intestinal mucosal changes on SARS-CoV-2 infection dynamics, disease severity, and vaccine responses remains unclear and requires further investigation.

Irreversible depletion of intestinal CD4+ T cells is associated with T cell activation during chronic HIV infection.

HIV infection in the human gastrointestinal (GI) tract is thought to be central to HIV progression, but knowledge of this interaction is primarily limited to cohorts within Westernized countries. Here, we present a large cohort recruited from high HIV endemic areas in South Africa and found that people living with HIV (PLWH) presented at a younger age for investigation in the GI clinic. We identified severe CD4+ T cell depletion in the GI tract, which was greater in the small intestine than in the large intestine and not correlated with years on antiretroviral treatment (ART) or plasma viremia. HIV-p24 staining showed persistent viral expression, particularly in the colon, despite full suppression of plasma viremia. Quantification of mucosal antiretroviral (ARV) drugs revealed no differences in drug penetration between the duodenum and colon. Plasma markers of gut barrier breakdown and immune activation were elevated irrespective of HIV, but peripheral T cell activation was inversely correlated with loss of gut CD4+ T cells in PLWH alone. T cell activation is a strong predictor of HIV progression and independent of plasma viral load, implying that the irreversible loss of GI CD4+ T cells is a key event in the HIV pathogenesis of PLWH in South Africa, yet the underlying mechanisms remain unknown.

Unbiased Profiling Reveals Compartmentalization of Unconventional T-Cells Within the Intestinal Mucosa Irrespective of HIV Infection.

The intestinal mucosa is enriched for unconventional T-cells, including mucosal associated invariant T-cells (MAIT), invariant natural killer T-cells (iNKT) and γδ T-cells. These cells are activated by bacterial metabolites, lipid antigens and cytokines, and are important for intestinal barrier integrity. The loss of gut homeostasis observed in HIV infection is central to disease pathogenesis, and studies have highlighted impairment of particular unconventional T-cell subsets within a specific gut compartment. However, although the small and large intestine are distinct niches, the overall impact of HIV on unconventional T-cells across the gut mucosal has not been well-studied. We hypothesized that compartment specific differences in the unconventional T-cell repertoire would exist between the small and large intestine, due to increasing bacterial loads and microbial diversity; and that the impact of HIV infection might differ depending on the compartment examined. We used mass cytometry, flow cytometry and unbiased T-cell receptor profiling to quantify unconventional T-cells in blood and tissue from the small (duodenum) and large (colon) intestine in HIV infected and uninfected participants undergoing examination for a range of intestinal conditions. Overall, we find distinct compartmentalisation of T-cells between blood, duodenum and colon, with iNKT cells significantly enriched in the duodenum and δ-1 expressing γδ T-cells in the colon. In addition, we observe greater clonal expansion of conventional TCRs in the duodenum, suggestive of stronger adaptive immunity in this compartment. Conversely, we find evidence of an expanded unconventional TCR repertoire in the colon, which contained far more overlapping "donor unrestricted" sequences than the duodenum. Twelve of these TCRs were highly "MAIT-like" and 3 were unique to the colon, suggesting an enrichment of donor unrestricted T-cells (DURTs) in this compartment. Unexpectedly, however, no significant impact of HIV infection on any of the unconventional T-cell subsets measured was observed in either mucosal site in terms of frequency or TCR repertoire. Further studies are required to investigate the importance of these unconventional T-cell subsets to intestinal homeostasis within the different gut compartments and determine if they are functionally impaired during HIV infection.

Innate Lymphoid Cell Activation and Sustained Depletion in Blood and Tissue of Children Infected with HIV from Birth Despite Antiretroviral Therapy.

Innate lymphoid cells (ILCs) are important for response to infection and for immune development in early life. HIV infection in adults depletes circulating ILCs, but the impact on children infected from birth remains unknown. We study vertically HIV-infected children from birth to adulthood and find severe and persistent depletion of all circulating ILCs that, unlike CD4+ T cells, are not restored by long-term antiretroviral therapy unless initiated at birth. Remaining ILCs upregulate genes associated with cellular activation and metabolic perturbation. Unlike HIV-infected adults, ILCs are also profoundly depleted in tonsils of vertically infected children. Transcriptional profiling of remaining ILCs reveals ongoing cell-type-specific activity despite antiretroviral therapy. Collectively, these data suggest an important and ongoing role for ILCs in lymphoid tissue of HIV-infected children from birth, where persistent depletion and sustained transcriptional activity are likely to have long-term immune consequences that merit further investigation.

Antimycobacterial, docking and molecular dynamic studies of pentacyclic triterpenes from Buddleja saligna leaves.

Buddleja saligna (family Buddlejaceae) is a medicinal plant endemic to South Africa. Two isomeric pentacyclic triterpenes, oleanolic acid and ursolic acid, were isolated from the leaves of B. saligna using silica gel column chromatography. Compounds oleanolic acid and ursolic acid were subjected to derivatization with acetic anhydride in the presence of pyridine to obtain oleanolic acid-3-acetate and ursolic acid-3-acetate, respectively. The structures of these compounds were fully characterized by detailed nuclear magnetic resonance (NMR) investigations, which included 1H and 13C NMR. Molecular docking studies predicted the free binding energy of the four triterpenes inside the steroid binding pocket of Mycobacterium tuberculosis fadA5 thiolase compared to a reported inhibitor. Thus, their ability to inhibit the growth of M. tuberculosis was predicted and was confirmed to possess significant antimycobacterial activity when tested against Mycobacterium smegmatis, M. tuberculosis H37Rv (ATCC 25177), clinical isolates of multi-drug-resistant M. tuberculosis (MDR-TB) and extensively drug-resistant M. tuberculosis (XDR-TB) using the Micro Alamar Blue Assay. Ursolic acid was isolated from this plant for the first time.