Myxobacteria-Derived Outer Membrane Vesicles: Potential Applicability Against Intracellular Infections

Abstract

In 2019, it was estimated that 2.5 million people die from lower tract respiratory infections annually. One of the main causes of these infections is Staphylococcus aureus, a bacterium that can invade and survive within mammalian cells. S. aureus intracellular infections are difficult to treat because several classes of antibiotics are unable to permeate through the cell wall and reach the pathogen. This condition increases the need for new therapeutic avenues, able to deliver antibiotics efficiently. In this work, we obtained outer membrane vesicles (OMVs) derived from the myxobacteria Cystobacter velatus strain Cbv34 and Cystobacter ferrugineus strain Cbfe23, that are naturally antimicrobial, to target intracellular infections, and investigated how they can affect the viability of epithelial and macrophage cell lines. We evaluated by cytometric bead array whether they induce the expression of proinflammatory cytokines in blood immune cells. Using confocal laser scanning microscopy and flow cytometry, we also investigated their interaction and uptake into mammalian cells. Finally, we studied the effect of OMVs on planktonic and intracellular S. aureus. We found that while Cbv34 OMVs were not cytotoxic to cells at any concentration tested, Cbfe23 OMVs affected the viability of macrophages, leading to a 50% decrease at a concentration of 125,000 OMVs/cell. We observed only little to moderate stimulation of release of TNF-alpha, IL-8, IL-6 and IL-1beta by both OMVs. Cbfe23 OMVs have better interaction with the cells than Cbv34 OMVs, being taken up faster by them, but both seem to remain mostly on the cell surface after 24 h of incubation. This, however, did not impair their bacteriostatic activity against intracellular S. aureus. In this study, we provide an important basis for implementing OMVs in the treatment of intracellular infections.

Within-species variation in OMV cargo proteins: theMyxococcus xanthusOMV pan-proteome

“…Each isolate produces a variety of secondary metabolites, some of which have been exploited for drug development. [29][30][31][32] Myxobacterial OMVs are predatory in their own right, with purified OMVs able to inhibit growth and kill both Gram-negative and Gram-positive prey bacteria, [33][34][35] and several proteomics studies have investigated the composition of myxobacterial OMVs. [35][36][37][38] However, no studies have compared the proteomes of myxobacterial OMVs from different strains, or indeed characterised the OMV proteome for any strain beyond the model organism M. xanthus DK1622.…”

Extracellular Vesicles and Their Interplay with Biological Membranes

“…Chemokines [25] Extracellular Vesicles and Gram-negative Beta-lactamase, coagulation factor, penicillin-binding protein [24,[37][38][39] Myxobacteria Chaperonin GroEL1, GroEL2, hydrolase, peptidase [24,40,41] Blood cells Platelets CD31, CD41, CD42a, CD62, C-type lectin, CXCR4, GPIIb/IIIa, PF4, SDF-1α [24,[42][43][44] Erythrocytes Glycophorin A, stomatin [24,34] Reticulocytes Galectin-5 [42,45] Bone cells Osteoblasts Cadherin-11 [42,46] Cancer cell lines Breast cancer cells (MM231, MM231LN)…”

Bacterial Outer Membrane Vesicles as Antibiotic Delivery Vehicles

“…OMVs produced by two additional myxobacterial strains, SBSr073 and Cbv34, were also shown to inhibit E. coli growth, a property the authors attributed to the presence of cystobactamids (myxobacterial-derived inhibitors of bacterial gyrase) within the OMVs ( 68 ). This group subsequently showed that OMVs produced by CBv34 and Cbfe23 (another myxobacterial strain) were taken up by host cells and inhibited intracellular growth of Staphylococcus aureus cells ( 69 ).…”