Low expression of antigen-presenting and costimulatory molecules by lung cells from tuberculosis patients

Immunomodulatory Effects of Recombinant Mycobacterium smegmatis Expressing Antigen-85B Epitopes in Infected J774A.1 Murine Macrophages

Tuberculosis (TB) causes more than 1.5 million deaths each year, remaining a significant global health problem. Mycobacterium smegmatis (M. smegmatis) and Mycobacterium tuberculosis (M. tuberculosis) share features, which support the use of the former use in new generation TB vaccine development. In a previous study, the specific humoral and cellular immunogenicity of a recombinant M. smegmatis strain expressing epitopes from M. tuberculosis Ag85B protein (rMs064), was demonstrated in mice. In the current study, the immunomodulatory capacity of rMs064 was determined in a J774A.1 murine macrophage cell line. To determine the immunomodulatory effect of rMs064 in J774A.1 macrophages, the expression of inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO) was evaluated. The expression of activation surface markers (MHC-II, CD40, CD80 and CD86) and the production of cytokines (IL-1β, TNF-α, IL-12p70 and IL-6) was also determined in rMs064 infected J774A.1 macrophages. Our findings showed the ability of rMs064 to induce substantial increases in macrophage activation markers expression; MHC class II and CD40, compared with M. smegmatis transformed with the empty vector (rMs012) and uninfected cells. rMs064 induced significant increases in IL-12p70 compared to uninfected cells. The expression of iNOS and CD86, and the production of IL-1β, and TNF-α were increased in rMs064 and rMs012, compared to uninfected cells. rMs064 demonstrated its immunomodulatory ability by stimulating the innate immune response, which supports its further evaluation as a TB vaccine candidate.

Simvastatin Enhances the Immune Response Against Mycobacterium tuberculosis

Tuberculosis remains a serious threat worldwide. For this reason, it is necessary to identify agents that shorten the duration of treatment, strengthen the host immune system, and/or decrease the damage caused by the infection. Statins are drugs that reduce plasma cholesterol levels and have immunomodulatory, anti-inflammatory and antimicrobial effects. Although there is evidence that statins may contribute to the containment of Mycobacterium tuberculosis infection, their effects on peripheral blood mononuclear cells (PBMCs) involved in the immune response have not been previously described. Using PBMCs from 10 healthy subjects infected with M. tuberculosis H37Rv, we analyzed the effects of simvastatin on the treatment of the infections in an in vitro experimental model. Direct quantification of M. tuberculosis growth (in CFU/mL) was performed. Phenotypes and cell activation were assessed via multi-color flow cytometry. Culture supernatant cytokine levels were determined via cytokine bead arrays. The induction of apoptosis and autophagy was evaluated via flow cytometry and confocal microscopy. Simvastatin decreased the growth of M. tuberculosis in PBMCs, increased the proportion of NKT cells in culture, increased the expression of co-stimulatory molecules in monocytes, promoted the secretion of the cytokines IL-1β and IL-12p70, and activated apoptosis and autophagy in monocytes, resulting in a significant reduction in bacterial load. We also observed an increase in IL-10 production. We did not observe any direct antimycobacterial activity. This study provides new insight into the mechanism through which simvastatin reduces the mycobacterial load in infected PBMCs. These results demonstrate that simvastatin activates several immune mechanisms that favor the containment of M. tuberculosis infection, providing relevant evidence to consider statins as candidates for host-directed therapy. They also suggest that future studies are needed to define the roles of statin-induced anti-inflammatory mechanisms in tuberculosis treatment.

Mycobacteria exploit p38 signaling to affect CD1 expression and lipid antigen presentation by human dendritic cells

Group I CD1 proteins are specialized antigen-presenting molecules that present both microbial and self lipid antigens to CD1-restricted alpha/beta T lymphocytes. The production of high levels of gamma interferon and lysis of infected macrophages by lipid-specific T lymphocytes are believed to play pivotal roles mainly in the defense against mycobacterial infections. We previously demonstrated that Mycobacterium tuberculosis and bacillus Calmette-Guérin (Mycobacterium bovis BCG) induce human monocytes to differentiate into CD1- dendritic cells (DC), which cannot present lipid antigens to specific T cells. Here, we show that in human monocytes mycobacteria trigger phosphorylation of p38 mitogen-activated protein kinase to inhibit CD1 expression in DC derived from infected monocytes. Pretreatment with a specific p38 inhibitor renders monocytes insensitive to mycobacterial subversion and allows them to differentiate into CD1+ DC, which are fully capable of presenting lipid antigens to specific T cells. We also report that one of the pathogen recognition receptors triggered by BCG to activate p38 is complement receptor 3 (CR3), as shown by reduced p38 phosphorylation and partial reestablishment of CD1 membrane expression obtained by CR3 blockade before infection. In conclusion, we propose that p38 signaling is a novel pathway exploited by mycobacteria to affect the expression of CD1 antigen-presenting cells and avoid immune recognition.

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.

Effect of oral immunomodulator Dzherelo in TB/HIV co-infected patients receiving anti-tuberculosis therapy under DOTS

Open-label, phase II clinical trial was conducted in 40 HIV/TB dually infected patients to evaluate the effect of oral immunomodulator Dzherelo on immune and viral parameters. The anti-retroviral therapy naïve patients were randomized into two equal groups to be given anti-tuberculosis therapy (ATT) under DOTS. The arm A, which served as a control, received Isoniazid (H); Rimfapicin (R); Pyrazinamide (Z); Streptomycin (S); and Ethambutol (E), and arm B received 50 drops of Dzherelo twice per day in addition to the daily dose of HRZSE. After 2months the total CD3+ lymphocytes increased from 728 to 921cells/microl (P=0.025) in Dzherelo recipients, whereas in the control group they decreased from 651 to 585 cells (P=0.25). The population of CD4 T-cells expanded in Dzherelo arm (174 to 283; P=0.00003) but declined in ATT group (182 to 174; P=0.34). The CD8 cells fluctuated slightly upward in both groups: 159>180 (P=0.17) and 159>183 (P=0.13). The ratio between CD4/CD8 cells deteriorated in arm A (1.213>0.943; P=0.002) but improved in arm B (1.244>1.536; P=0.007). The percent of CD3+HLA-DR+ activated lymphocytes had fallen in ATT group (22.6>20.5; P=0.004), but rose in Dzherelo recipients (21.5>30.5; P=0.0001). The changes in CD20+ B lymphocytes were insignificant in both arms (28.4%>28.6%; P=0.4) and (27.2%>26.7%; P=0.38). No difference was seen in the amount of CD3-CD16+CD56+ natural killer (NK) cells in arm A (21.3%>22.6%; P=0.1), while in Dzherelo recipients they declined significantly (19.9%>14.5%; P=0.0026). The viral load, measured by plasma RNA-PCR, decreased in Dzherelo group (2174>1558; P=0.002), but increased in ATT group (1907>2076 copies/ml; P=0.03). Dzherelo has a favorable effect on the immune status and viral burden in HIV/TB patients when given as the immunomodulating adjunct to ATT.