Burkholderia mallei and Burkholderia pseudomallei stimulate differential inflammatory responses from human alveolar type II cells (ATII) and macrophages

Abstract

Alveolar type II pneumocytes (ATII) and alveolar macrophages (AM) play a crucial role in the lung's innate immune response. Burkholderia pseudomallei (BP) and Burkholderia mallei (BM) are facultative Gram-negative bacilli that cause melioidosis and glanders, respectively. The inhalation of these pathogens can cause lethal disease and death in humans. We sought to compare the pathogenesis of and host responses to BP and BM through contact with human primary ATII cells and monocytes-derived macrophages (MDM). We hypothesized that because BP and BM induce different disease outcomes, each pathogen would induce distinct, unique host immune responses from resident pulmonary cells. Our findings showed that BP adhered readily to ATII cells compared to BM. BP, but not BM, was rapidly internalized by macrophages where it replicated to high numbers. Further, BP-induced significantly higher levels of pro-inflammatory cytokine secretion from ATII cells (IL-6, IL-8) and macrophages (IL-6, TNFα) at 6 h post-infection compared to BM (p < 0.05). Interestingly, BM-induced the anti-inflammatory cytokine, IL-10, in ATII cells and macrophages at 6 h post-infection, with delayed induction of inflammatory cytokines at 24 h post-infection. Because BP is flagellated and produces LPS, we confirmed that it stimulated both Toll-like receptor (TLR) 4 and TLR5 via NF-κb activation while the non-flagellated BM stimulated only TLR4. These data show the differences in BP and BM pathogenicity in the lung when infecting human ATII cells and macrophages and demonstrate the ability of these pathogens to elicit distinct immune responses from resident lung cells which may open new targets for therapeutic intervention to fight against these pathogens.

Entry, Intracellular Survival, and Multinucleated-Giant-Cell-Forming Activity of Burkholderia pseudomallei in Human Primary Phagocytic and Nonphagocytic Cells

“…We show that B. pseudomallei has the capacity to invade normal bronchial epithelial cells (NHBE), vein endothelial cells (HUVEC), gingival fibroblasts (HGFs), and keratinocytes (KCs) and to survive in these cells for at least 19 h. The discovery of invasion and intracellular survival of B. pseudomallei in endothelial cells and keratinocytes is a novel finding, which has also not been reported for endothelial or keratinocyte cell lines. Infection of bronchial epithelial NHBE and HGFs is in agreement with previous studies reporting the isolation of viable bacteria from primary alveolar epithelial cells and immortalized fibroblast cells, respectively (9,34,36,42). HGFs and KCs appear to restrict efficient intracellular replication of B. pseudomallei as indicated by decreasing levels of intracellular CFU counts over the course of the infection.…”

“…In vitro, the bacteria actively invade various nonphagocytic cells. However, to the best of our knowledge, this notion is based on findings obtained with immortalized cells except for two studies using primary alveolar epithelial cells (8,(33)(34)(35)(36). Furthermore, the ability of B. pseudomallei to infect every tissue and the ubiquitous presence of glutathione in human cells raises the question of cell type specificity of T6SS-5 activity and therefore of MNGC formation.…”

Mechanisms of Disease: Host-Pathogen Interactions between Burkholderia Species and Lung Epithelial Cells

“…Items in bold are specific for Burkholderia pseudomallei and/or mallei . Invasion of bacteria is driven by several bacterial factors; capsule (Phewkliang et al, 2010 ), cable pili (Sajjan and Forstner, 1992 , 1993 ), pilA (Essex-Lopresti et al, 2005 ), adhesins [ boaA/B (Balder et al, 2010 ; Lu et al, 2012 ) and other auto-transporter adhesins (Mil-Homens and Fialho, 2012 ; Lafontaine et al, 2014 )], LPS (Dziarski and Gupta, 2000 ), Lipid A (Dziarski and Gupta, 2000 ), flagella (Tomich et al, 2002 ; Chuaygud et al, 2008 ; Allwood et al, 2011 ), irl locus (Jones et al, 1997 ), a 22kDa adhesion (Sajjan and Forstner, 1993 ), lipase (Mullen et al, 2007 ), and the metalloprotease ZmpA (Gingues et al, 2005 ). Receptor binding events on epithelial cells occur via mucin (Sajjan and Forstner, 1992 ), the asialogangliosides GM1/2 (Gori et al, 1999 ), toll-like receptors (West et al, 2009 , 2013 ), and cytokeratin 13 (Sajjan et al, 2002 ).…”

“…(B) The host response to Burkholderia infection from epithelial cells. Inflammation is driven by Nfk-B induction (Dziarski and Gupta, 2000 ) of IL-8 (Palfreyman et al, 1997 ; Fink et al, 2003 ; Utaisincharoen et al, 2005 ; Sim et al, 2009 ; Lu et al, 2012 ), IL-6 (Sim et al, 2009 ; Lu et al, 2012 ) and IL-1β (Sim et al, 2009 ; Lu et al, 2012 ; Gillette et al, 2013 ), TNF-α, MCP-1 and CCL20 (Sim et al, 2009 ; Lu et al, 2012 ). Tight junctions are disrupted (Kim et al, 2005 ; Duff et al, 2006 ; Ferreira et al, 2015 ) and extracellular matrix components degraded by matrix metalloproteases (Wright et al, 2011 ).…”

Immunomodulatory and Antibacterial Effects of Cystatin 9 against Francisella tularensis

“…Western blots were performed as we described previously (23). Briefly, MDM were given 50 pg of rCST9 and/or S4 (MOI 40:1).…”