Quantitative and functional differences between peripheral blood myeloid dendritic cells from patients with pleural and parenchymal lung tuberculosis

Blood monocyte and dendritic cell profiles among people living with HIV with Mycobacterium tuberculosis co-infection

BACKGROUND

Understanding the complex interactions of the immune response mediated by Mycobacterium tuberculosis and HIV co-infection is fundamental to disease biomarker discovery, vaccine, and drug development. Using flow cytometry, we characterized the frequencies and phenotypic differences in monocytes and dendritic cell populations using peripheral blood mononuclear cells from individuals with recurrent, active pulmonary tuberculosis with and without coexisting HIV infection (CAPRISA 011, Clinicaltrials.gov, NCT02114684, 29/01/2014) and compared them to samples from HIV positive individuals and healthy controls. Additionally, we assessed the associations between the frequency of monocyte and dendritic cell subsets and time to culture conversion and cavitary disease in patients with active TB using a cox proportional hazards and logistic regression models.

RESULTS

Compared to healthy controls, the frequency of total monocytes (HLA-DR + CD14 +) was significantly higher in the TB/HIV and TB groups and the frequency of dendritic cells (HLA-DR + CD14-) was significantly higher in TB/HIV and HIV groups. We observed significant variation in the expression of CCR2, CD40, CD11b, CD86, CD163, CX3CR1 across different cell subsets in the four study groups. Increase in CCR2, CD11b and CD40 was associated with active TB infection, while decrease in CX3CR1 and increase in CD163 was associated with HIV infection. Expression of CX3CR1 (aHR 0.98, 95% CI 0.963 - 0.997, p = 0.019) on non-classical monocytes associated with longer time to TB culture conversion in the multivariable model correcting for randomization arm, age, sex, HIV status, lung cavitation, alcohol use, smoking and BMI. Higher surface expression of CD86 (aOR 1.017, 95% CI 1.001 - 1.032, p = 0.033) on intermediate monocytes associated with the presence of lung cavitation, while higher expression of transitional monocytes (aOR 0.944, 95% CI 0.892 - 0.999, p = 0.047) associated with the absence of lung cavitation in the multivariable model.

CONCLUSION

These data provide valuable insight into the heterogenous role of monocyte and dendritic cells in TB and HIV infections.

Human Pulmonary Tuberculosis: Understanding the Immune Response in the Bronchoalveolar System

Mycobacterium tuberculosis, the causal agent of one of the most devastating infectious diseases worldwide, can evade or modulate the host immune response and remain dormant for many years. In this review, we focus on identifying the local immune response induced in vivo by M. tuberculosis in the lungs of patients with active tuberculosis by analyzing data from untouched cells from bronchoalveolar lavage fluid (BALF) or exhaled breath condensate (EBC) samples. The most abundant resident cells in patients with active tuberculosis are macrophages and lymphocytes, which facilitate the recruitment of neutrophils. The cellular response is characterized by an inflammatory state and oxidative stress produced mainly by macrophages and T lymphocytes. In the alveolar microenvironment, the levels of cytokines such as interleukins (IL), chemokines, and matrix metalloproteinases (MMP) are increased compared with healthy patients. The production of cytokines such as interferon (IFN)-γ and IL-17 and specific immunoglobulin (Ig) A and G against M. tuberculosis indicate that the adaptive immune response is induced despite the presence of a chronic infection. The role of epithelial cells, the processing and presentation of antigens by macrophages and dendritic cells, as well as the role of tissue-resident memory T cells (Trm) for in situ vaccination remains to be understood.

Ex-vivo immunophenotyping and high dimensionality UMAP analysis of leucocyte subsets in tuberculous lymphadenitis

Tuberculous lymphadenitis (TBL) is defined by reduced proinflammatory cytokines and elevated CD4⁺, CD8⁺ T cells and decreased CD8⁺ cytotoxic markers. However, ex-vivo phenotyping of diverse leucocytes in TBL has not been done. We show activated and atypical B cells, myeloid dendritic cells (mDCs), classical, non-classical and intermediate monocytes, T regulatory (T regs) cells, CD4⁺ T cell effector memory RA (TEMRA), CD4⁺ effector and CD8⁺ central memory phenotypes were significantly increased in TBL compared to LTB individuals. In contrast, classical memory and plasma B cells, plasmacytoid DCs (pDCs), CD8⁺ TEMRA, CD4⁺ naïve and central memory cells were significantly decreased in TBL compared to LTB individuals. Some of the leucocyte frequencies (atypical memory B cells, pDCs, myeloid-derived suppressor cells, CD4⁺ effector and CD8⁺ central memory was increased; activated memory and plasma B cell, mDCs, classical, non-classical, intermediate monocytes, T regs, CD4⁺ TEMRA, CD4⁺, CD8⁺ naïve and effector memory cells and CD8⁺ central memory cells were decreased) were significantly modulated after anti-TB treatment among TBL individuals. UMAP analysis show that leucocyte subsets or islands expressing specific markers were significantly different in TBL baseline and post-treatment individuals. Overall, we suggest altered frequencies of diverse leucocytes influences the disease pathology and protective immunity in TBL individuals.

Interplay between alveolar epithelial and dendritic cells and Mycobacterium tuberculosis

The innate response plays a crucial role in the protection against tuberculosis development. Moreover, the initial steps that drive the host-pathogen interaction following Mycobacterium tuberculosis infection are critical for the development of adaptive immune response. As alveolar Mϕs, airway epithelial cells, and dendritic cells can sense the presence of M. tuberculosis and are the first infected cells. These cells secrete mediators, which generate inflammatory signals that drive the differentiation and activation of the T lymphocytes necessary to clear the infection. Throughout this review article, we addressed the interaction between epithelial cells and M. tuberculosis, as well as the interaction between dendritic cells and M. tuberculosis. The understanding of the mechanisms that modulate those interactions is critical to have a complete view of the onset of an infection and may be useful for the development of dendritic cell-based vaccine or immunotherapies.

High expression of BTLA and B7-H4 on the surface of myeloid dendritic cells has a negative regulatory effect on their anti-tuberculosis immunity activity in pleural tuberculosis patients

To investigate the effects of the surface markers B- and T-lymphocyte attenuator (BTLA) and B7 homologous body 4 (B7-H4) on expression of CD83, and Human Leukocyte Antigen-DR isotype (HLA-DR) that can activate dendritic cells (DCs). Flow cytometry was used to detect the co-expression of BTLA and B7-H4 on myeloid DCs (mDCs) in peripheral blood (PB) and pleural effusions (PE) in 15 volunteers and 20 tuberculous pleurisy (TP) patients. Co-expression of BTLA and B7-H4 (double positive (DP)) mDCs in PB and PE of TP patients were enhanced. The proportion of DP mDC in PB decreased markedly after 2 weeks treatment, but was still greater than in controls. Expression of CD83 and HLA-DR on DP mDCs was higher than on BTLA and B7-H4 double negative (DN) expressing mDCs in PB of different TP groups. Expression of CD83 on DP mDCs in PB and PE of TP patients was greater than that of controls. Expression of HLA-DR on DP mDCs in TP patient PB was lower than in TP PE and controls. In pleural tuberculosis (TB) patients, high expression of BTLA and B7-H4 promoted a high level of CD83 and HLA-DR, which had a negative regulatory effect on mDCs on anti-TB immunity.

Profiling dendritic cell subsets in the patients with active pulmonary tuberculosis

Dendritic cell (DC) plays an important role in the immune response against pulmonary tuberculosis. However, the phenotypic profile of DC subsets in peripheral blood in individuals with active pulmonary tuberculosis (APT) is still inconclusive. Here, we demonstrated that the absolute numbers of total DC (tDC), myeloid DC (mDC) and plasmacytoid DC (pDC) in individuals with APT were decreased compared to healthy controls (HCs). The decreased number of DCs, especially of pDC, seems to be a useful diagnostic marker of APT. Meanwhile, the number of DCs was associated with the prolonged/complicated TB, ATD treatment effect and lymphocyte immune reactions, as manifested that relapsed APT patients with a higher number of tDC and lower number of pDC compared to newly diagnosed patients. Interestingly, mDC from APT patients displayed high expressions of CD83 and CCR7, but pDC displayed low expressions of CD83 and CCR7. Moreover, DCs from APT patients expressed lower levels of HLA-DR and CD80, but expressed a higher level of CD86 than those from HCs. However, the antigen uptake capacity of DC subsets was not different between APT and HCs, despite the antigen uptake capacity of pDC was much lower than that of mDC in both APT patients and HCs. Our data represent a systematic profile of DC subsets in the blood of APT patients, and would represent a useful biomarker for APT.

T regulatory cells (TREG)(TCD4+CD25+FOXP3+) distribution in the different clinical forms of leprosy and reactional states

BACKGROUND

Leprosy is characterized histologically by a spectrum of different granulomatous skin lesions, reflecting patients' immune responses to Mycobacterium leprae. Although CD4+CD25+ FoxP3+ T regulatory cells are pivotal in the immuneregulation, presence, frequency, and distribution of Tregs in leprosy, its reactional states have been investigated in few studies.

OBJECTIVES

This study aimed to verify the frequency and distribution of regulatory T cells in different clinical forms and reactional states of leprosy.

METHODS

We performed an immunohistochemical study on 96 leprosy cases [Indeterminate (I): 9 patients; tuberculoid tuberculoid: 13 patients; borderline tuberculoid: 26 patients; borderline borderline: 3 patients; borderline lepromatous: 8 patients; lepromatous lepromatous: 27 patients; reversal reaction: 8 patients; and erythema nodosum leprosum: 2 patients].

RESULTS

FoxP3-positive cells were present in 100% of the cases with an average density of 2.82% of the infiltrate. Their distribution was not related to granulomatous structures or special locations. There was a statistically significant increment of FoxP3 expression in patients with leprosy reversal reactions when compared with patients presenting with type I leprosy (P= 0.0228); borderline tuberculoid leprosy (P = 0.0351) and lepromatous leprosy (P = 0.0344).

CONCLUSIONS

These findings suggest that Tregs play a relevant role in the etiopathogenesis of leprosy, mainly in type I leprosy reaction.

Impaired dendritic cell differentiation of CD16-positive monocytes in tuberculosis: role of p38 MAPK

Tuberculosis (TB) is one of the world's most pernicious diseases mainly due to immune evasion strategies displayed by its causative agent Mycobacterium tuberculosis (Mtb). Blood monocytes (Mos) represent an important source of DCs during chronic infections; consequently, the alteration of their differentiation constitutes an escape mechanism leading to mycobacterial persistence. We evaluated whether the CD16(+)/CD16(-) Mo ratio could be associated with the impaired Mo differentiation into DCs found in TB patients. The phenotype and ability to stimulate Mtb-specific memory clones DCs from isolated Mo subsets were assessed. We found that CD16(-) Mos differentiated into CD1a(+) DC-SIGN(high) cells achieving an efficient recall response, while CD16(+) Mos differentiated into a CD1a(-) DC-SIGN(low) population characterized by a poor mycobacterial Ag-presenting capacity. The high and sustained phosphorylated p38 expression observed in CD16(+) Mos was involved in the altered DC profile given that its blockage restored DC phenotype and its activation impaired CD16(-) Mo differentiation. Furthermore, depletion of CD16(+) Mos indeed improved the differentiation of Mos from TB patients toward CD1a(+) DC-SIGN(high) DCs. Therefore, Mos from TB patients are less prone to differentiate into DCs due to their increased proportion of CD16(+) Mos, suggesting that during Mtb infection Mo subsets may have different fates after entering the lungs.

Optimization of a whole blood intracellular cytokine assay for measuring innate cell responses to mycobacteria

Innate cells are essential for host defense against invading pathogens, and the induction and direction of adaptive immune responses to infection. We developed and optimized a flow cytometric assay that allows measurement of intracellular cytokine expression by monocytes, dendritic cells (DC) and granulocytes, as well as cellular uptake of green-fluorescent protein (GFP)-expressing mycobacteria, in very small volumes of peripheral blood. We show that innate cell stimulation resulted in increased granularity of monocytes and mDC and decreased granulocyte granularity that precluded flow cytometric discernment of granulocytes from monocytes and myeloid DC by forward and side scatter gating. Anti-CD66a/c/e antibody staining allowed reliable identification and exclusion of granulocytes for subsequent delineation of monocytes and myeloid DC. Intracellular cytokine expression by granulocytes, monocytes and mDC was remarkably sensitive to the dose of mycobacterial inoculum. Moreover, activation of monocytes and mDC with live BCG reduced expression levels of CD14 and CD11c, respectively, necessitating optimization of staining conditions to reliably measure these lineage markers. Finally, we characterized expression of IL-12/23p40, TNF-α, IL-6, and IL-10, by GFP(+) and GFP(-) monocytes and mDC from 25 healthy adults. This assay may be applied to the study of innate cell responses to any GFP-expressing pathogen, and can be performed on blood volumes as low as 200 μL per condition, making the assay particularly suitable for pediatric studies.

Disparity in circulating peripheral blood dendritic cell subsets and cytokine profile of pulmonary tuberculosis patients compared with healthy family contacts

Dendritic cell (DC) subsets, myeloid DCs (mDCs), and plasmacytoid DCs (pDCs) play a fundamental role in immune response to Mycobacterium tuberculosis (M. tuberculosis). Flow-cytometric estimation of DC subsets showed differences in the ratio of these subsets in untreated, smear-positive pulmonary tuberculosis patients compared with healthy family contacts (HFC, p < 0.05). The percentage of pDCs (0.14 +/- 0.01) was higher than mDCs (0.12 +/- 0.01) in patients, whereas in HFC, mDCs (0.15 +/- 0.01) was higher than pDCs (0.1 +/- 0.01). The percentage of mDCs (0.15 +/- 0.01) and pDCs (0.11 +/- 0.01) was restored in treated patients. Alteration in the DC subsets before and after chemotherapy was confirmed in the follow-up of acid-fast bacilli (AFB)-positive patients. This reversal in the percentage of mDC vs pDCs implicates the influence of active disease on circulating DC subsets. The cytokine bead array revealed an inverse relationship in the circulating levels of IL-12 and IFN-gamma. High IL-12 (37.9 +/- 15.2) and low IFN-gamma (11.09 +/- 3.6) was seen in HFCs derived serum samples compared with that of patients (p < 0.05). The higher percentage of mDCs and elevated IL-12 levels was found to be associated with high risk HFCs investigated. Furthermore CpG/LPS-stimulated whole-blood culture of untreated patients expressed high IFN-alpha in pDCs and less IL-12 in mDCs compared with those of treated patients.

Impaired phenotype and function of monocyte derived dendritic cells in pulmonary tuberculosis

Pulmonary tuberculosis (PTB) is often associated with impaired immunological functions. Blood monocytes, which can differentiate into dendritic cells upon cytokine stimulation, play a central role in adequate immune reactivity. Here, we investigated the morphologic, phenotypic and functional characteristics of in vitro-generated monocyte derived dendritic cells (MoDC) from PTB patients in comparison with healthy subjects. Phenotypic analysis revealed a defective differentiation of MoDC in PTB patients as assessed by a strong down regulation of CD1a, MHC II, CD80 and CD83 expression and impaired allostimulatory function under the influence of IL-4 and GM-CSF. In contrast, the expression of CD86 was not affected and remained same as in healthy subjects. Furthermore, the maturation status of lipopolysaccharide (LPS) stimulated MoDC was not optimal in PTB. However, the MoDC of PTB patients produced significantly higher levels of TNF-alpha and IL-6 but lower levels of IL-12 compared to healthy subjects. These findings suggest that there is a fundamental defect in the differentiation and maturation of dendritic cells during PTB that may compromise the antigen presentation and subsequent immune functions.

Alteration of the relative levels of iNKT cell subsets is associated with chronic mycobacterial infections

CD1d-restricted invariant natural killer T cells (iNKT cells) have been identified as an important type of effector and regulatory T cell, but their roles in the chronic infectious diseases caused by Mycobacterium tuberculosis and Mycobacterium leprae remain poorly defined. Here, we studied circulating human iNKT cells in blood samples from tuberculosis (TB) and leprosy patients. We found that the percentages of iNKT cells among total circulating T cells in TB and leprosy patients were not significantly different from those in normal controls. However, both TB and leprosy patients showed a selective reduction of the proinflammatory CD4(-)CD8beta(-) (DN) iNKT cells with a proportionate increase in the CD4(+) iNKT cells. Similar phenotypic alterations in circulating iNKT cells were observed in a mouse model of M. tuberculosis infection. Taken together, these findings indicate that the selective reduction of circulating DN iNKT cells is associated with chronic infections caused by M. tuberculosis and M. leprae.