Liposomes loaded with bioactive lipids enhance antibacterial innate immunity irrespective of drug resistance

Phagocytosis is a key mechanism of innate immunity, and promotion of phagosome maturation may represent a therapeutic target to enhance antibacterial host response. Phagosome maturation is favored by the timely and coordinated intervention of lipids and may be altered in infections. Here we used apoptotic body-like liposomes (ABL) to selectively deliver bioactive lipids to innate cells, and then tested their function in models of pathogen-inhibited and host-impaired phagosome maturation. Stimulation of macrophages with ABLs carrying phosphatidic acid (PA), phosphatidylinositol 3-phosphate (PI3P) or PI5P increased intracellular killing of BCG, by inducing phagosome acidification and ROS generation. Moreover, ABLs carrying PA or PI5P enhanced ROS-mediated intracellular killing of Pseudomonas aeruginosa, in macrophages expressing a pharmacologically-inhibited or a naturally-mutated cystic fibrosis transmembrane conductance regulator. Finally, we show that bronchoalveolar lavage cells from patients with drug-resistant pulmonary infections increased significantly their capacity to kill in vivo acquired bacterial pathogens when ex vivo stimulated with PA-or PI5P-loaded ABLs. Altogether, these results provide the proof of concept of the efficacy of bioactive lipids delivered by ABL to enhance phagosome maturation dependent antimicrobial response, as an additional host-directed strategy aimed at the control of chronic, recurrent or drug-resistant infections

Monosodium urate crystals promote innate anti-mycobacterial immunity and improve BCG efficacy as a vaccine against tuberculosis

A safer and more effective anti-Tuberculosis vaccine is still an urgent need. We probed the effects of monosodium urate crystals (MSU) on innate immunity to improve the Bacille Calmette-Guerin (BCG) vaccination. Results showed that in vitro MSU cause an enduring macrophage stimulation of the anti-mycobacterial response, measured as intracellular killing, ROS production and phagolysosome maturation. The contribution of MSU to anti-mycobacterial activity was also shown in vivo. Mice vaccinated in the presence of MSU showed a lower number of BCG in lymph nodes draining the vaccine inoculation site, in comparison to mice vaccinated without MSU. Lastly, we showed that MSU improved the efficacy of BCG vaccination in mice infected with Mycobacterium tuberculosis (MTB), measured in terms of lung and spleen MTB burden. These results demonstrate that the use of MSU as adjuvant may represent a novel strategy to enhance the efficacy of BCG vaccination

Natural lysophospholipids reduce Mycobacterium tuberculosis-induced cytotoxicity and induce anti-mycobacterial activity by a phagolysosome maturation-dependent mechanism in A549 type II alveolar epithelial cells

Human alveolar epithelial cells actively contribute to the innate immune response in the lung and play an important role in mycobacterial dissemination during primary infection, by undergoing cell death and by releasing mycobacteria. In the present study, we report that natural lysophospholipids, such as lysophosphatidic acid or sphingosine 1-phosphate, reduce Mycobacterium tuberculosis-induced cytotoxicity and enhance anti-mycobacterial activity in the A549 cell line, used as a model of type II alveolar epithelial cells. Intracellular mycobacterial killing was strictly dependent on phagolysosome maturation, which in turn was promoted by the activation of a Ca2+dependent phospholipase D. Finally, the restriction of mycobacteria in highly microbiocidal compartments was associated, in vitro, with a significant decrease in mycobacterial dissemination to macrophages. Taken as whole, these results suggest that the pulmonary lysophospholipid microenvironment may play a protective role during the early phases of host–pathogen interaction by enhancing anti-mycobacterial activity in type II alveolar epithelial cells

Co-administration of BCG with MSU crystals enhances the clearance and efficacy of BCG vaccination.

<p>Five mice per group were vaccinated with i) 10^<b>6</b> CFU BCG, ii) 10^<b>6</b> CFU BCG+MSU [200 μg], or iii) PBS alone. (<b>A</b>) Mice were sacrificed after 15 days from immunization and BCG colonies enumerated by the draining axillary lymph nodes. Immunized and control mice were infected 10 weeks post immunization with <i>M</i>. <i>tuberculosis</i> Erdman (≈ 100 CFU/mouse) by the aerogenic route. Twenty-eight days later, mice were sacrificed and bacterial loads were determined by CFU counting in the lungs (<b>B</b>) and spleens (<b>C</b>). * p < 0.05 in comparison with BCG vaccinated mice.</p

MSU crystals enhance antimycobacterial activity.

<p>(<b>A</b>) Differentiated THP-1 (dTHP1) cells were infected with BCG at the MOI of 1 and then stimulated or not with 0.5, 5, 50 μg/ml of MSU for 3 and 5 days. The results are expressed as means ± Standard Deviation (SD) of CFU values performed in triplicate and are representative of three independent experiments. * p ≤ 0.001 in comparison with non-stimulated control cells. (<b>B</b>) Stimulation of human macrophages with MSU enhances phagocytosis of BCG. Differentiated THP-1 cells were exposed to BCG at the MOI of 1 for 3 hour in the presence or not of 0.05, 0.5, 5 μg/ml MSU. Results are expressed as mean ± SD of CFU values performed in triplicate and are representative of two independent experiments. * p < 0.05 in comparison with non-stimulated control cells.</p

MSU crystals enhance Ca²⁺ dependent ROS production.

<p>(<b>A</b>) dTHP-1 cells were incubated with 3 μM Fluo-3/AM at 37°C for 1 hour in the dark and were stimulated with 5 μg/ml MSU. After stimulation, fluorescence emission was continuously monitored for 30 minutes and expressed as to determine relative alteration in intensity. (<b>B</b>) dTHP-1 cells were incubated for 1 hour at the dark with 10 μM DCF, or with 3 μM Fluo-3/AM (inset of the figure), and were stimulated with 5 μg/ml MSU. Ca^<b>2+</b> dependence ROS generation was assessed by adding 20 μM BAPTA-AM or 3 mM EGTA 30 minutes and 15 minutes before MSU addition, respectively. Fluorescence emission was monitored at 20 minutes after stimulation. Results are expressed as mean ± SD of arbitrary fluorescence units performed in triplicate and are representative of three separate experiments. * p < 0.01 in comparison with non-stimulated control cells</p

MSU crystals induce trained anti-mycobacterial innate immunity.

<p>(<b>A</b>) Diagram showing the course of <i>in vitro</i> preincubation experiment. THP-1 cells were cultured with 5 or 50 μg/ml MSU for 3 days. Thereafter, the medium was changed to remove MSU stimulus and cells cultured for further 4 days. Finally, cells were exposed to BCG at the MOI of 10 for 3 hours (T0), washed and cultured for further 3 days (T3). (<b>B</b>) Intracellular mycobacterial growth was monitored in BCG infected THP-1 cells prestimulated or not with 5 or 50 μg/ml MSU. Results are shown as mean ± SD of CFU values performed in triplicate and are representative of three independent experiments. ° p < 0.05 and * p < 0.001 in comparison with same time non pre-stimulated control cells. (<b>C</b>) Intracellular mycobacterial growth was monitored in THP-1 cells, pre-stimulated or not with 50 μg/ml MSU, and exposed or not to 10 μM chloroquine after BCG infection for 3 days. Results are shown as mean ° SD of CFU values performed in triplicate. * p < 0.05 and ° p < 0.01 in comparison with same time non pre-stimulated control cells. (<b>D</b>) IL-1β production in the supernatant of BCG infected THP-1 cells pre-stimulated or not with either 5 or 50 μg/ml MSU. Results are shown as mean ± SD of values performed in triplicate and are representative of three independent experiments. * p < 0.05 in comparison with same time non pre-stimulated control cells.</p

MSU crystals induce phagolysosome dependent ROS generation.

<p>dTHP-1 cells were infected or not with BCG at the MOI of 5 and then labelled with 10 μM DCF for 60 min. Thereafter, cells were washed twice, stimulated or not overnight with 5 μg/ml MSU in the presence or absence of 10 μM Chloroquine (Cq). Results are expressed as means ± SD of arbitrary fluorescence units of triplicate values and are representative of two independent experiments. * p < 0.001 in comparison with non-stimulated control cells. ° p < 0.001 in comparison with MSU stimulated cells or with MSU-stimulated BCG-infected cells.</p

MSU crystals reduce intracellular BCG viability in a phagolysosome maturation dependent and ROS mediated manner.

<p>BCG infected dTHP-1 cells were stimulated or not with 5 μg/ml MSU and CFU assays were performed at day 3 post-infection. (<b>A</b>) In order to ascertain whether phagolysosome maturation was responsible for intracellular mycobacterial killing, 10 μM chloroquine (Cq) or 20 mM NH₄Cl was added to BCG-infected cells together with MSU. Results are expressed as mean ± SD of CFU values performed in triplicate and are representative of two independent experiments. * p < 0.001 in comparison with non-stimulated control cells. (<b>B</b>) In order to ascertain the role of ROS in intracellular mycobacterial killing, 100 U/ml PEG-catalase was added to BCG infected cells together with MSU. Results are expressed as mean ± SD of CFU values performed in triplicate and are representative of two independent experiments. * p < 0.001 in comparison with non-stimulated control cells.</p