Lymphatic filariasis is the major global cause of non-hereditary lymphoedema. We demonstrate the filarial nematode, Brugia malayi, induces lymphatic remodelling and impaired lymphatic drainage following parasitism of limb lymphatics in a mouse model. Lymphatic insufficiency was associated with elevated circulating lymphangiogenic mediators, including vascular endothelial growth factor C. Lymphatic insufficiency was dependent on type-2 adaptive immunity, interleukin-4 receptor, recruitment of C-C chemokine receptor-2 monocytes and alternatively-activated macrophages with pro-lymphangiogenic phenotype. Oral treatments with second-generation tetracyclines improved lymphatic function, while other classes of antibiotic had no significant effect. Second-generation tetracyclines directly targeted lymphatic endothelial cell proliferation and modified type-2 pro-lymphangiogenic macrophage development. Doxycycline treatment impeded monocyte recruitment, inhibited polarisation of alternatively-activated macrophages and suppressed T cell adaptive immune responses following infection. Our results determine a mechanism-of-action for the anti-morbidity effects of doxycycline in filariasis and supports clinical evaluation of second-generation tetracyclines as affordable, safe therapeutics for lymphoedemas of chronic inflammatory origin.
Julio Furlong-Silva, Stephen D. Cross, Amy E. Marriott, Nicolas Pionnier, John Archer, Andrew Steven, Stefan Schulte-Merker, Matthias Mack, Young-Kwon Hong, Mark J. Taylor, Joseph D. Turner