Differential modulation of innate immune cell functions by theBurkholderia cepaciacomplex:Burkholderia cenocepaciabut notBurkholderia multivoransdisrupts maturation and induces necrosis in human dendritic cells

Abstract

SummaryBurkholderia cepacia complex (BCC) bacteria cause pulmonary infections that can evolve into fatal overwhelming septicemia in chronic granulomatous disease or cystic fibrosis patients. Burkholderia cenocepacia and Burkholderia multivorans are responsible for the majority of BCC infections in cystic fibrosis patients, but B. cenocepacia is generally associated with a poorer prognosis than B. multivorans. The present study investigated whether these pathogens could modulate the normal functions of primary human monocyte-derived dendritic cells (DCs), important phagocytic cells that act as critical orchestrators of the immune response. Effects of the bacteria on maturation of DCs were determined using flow cytometry. DCs co-incubated for 24 h with B. cenocepacia, but not B. multivorans, had reduced expression of costimulatory molecules when compared with standard BCC lipopolysaccharide-matured DCs. B. cenocepacia, but not B. multivorans, also induced necrosis in DCs after 24 h, as determined by annexin V and propidium iodide staining. DC necrosis only occurred after phagocytosis of live B. cenocepacia; DCs exposed to heat-killed bacteria, bacterial supernatant or those pre-treated with cytochalasin D then exposed to live bacteria remained viable. The ability of B. cenocepacia to interfere with normal DC maturation and induce necrosis may contribute to its pathogenicity in susceptible hosts.

Interaction of Burkholderia pseudomallei and Burkholderia thailandensis with human monocyte-derived dendritic cells

“…After 7 days of incubation, including one complete replacement of media, at 37 uC in a 5 % CO 2 atmosphere, cells were removed from plates by gentle scraping and cells with an immature DC phenotype were confirmed by flow cytometry as detailed below. In concordance with other studies, cells were .95 % pure (MacDonald & Speert, 2008;Noske et al, 2009). …”

“…Meanwhile, imipenem is lipid insoluble and penetrates cells poorly if at all (Menashe et al, 2008;Murdoch & Peterson, 1991;Sahly et al, 2008). Numerous other studies have used imipenem (Boddey et al, 2007;Brown et al, 2004;MacDonald & Speert, 2008) rather than kanamycin. We have compared the effects of Table 1.…”

“…The related pathogen, Burkholderia cenocepacia disrupts DC maturation and induces necrosis after uptake of live bacteria (MacDonald & Speert, 2008). It therefore seems plausible that B. pseudomallei should also belong to the growing list of pathogens that elicit an abnormal immune response from DCs.…”

Immune Recognition of the Epidemic Cystic Fibrosis Pathogen Burkholderia dolosa

“…While it is clear that members of the BCC can induce immune responses in cultured mammalian cells (12,54,(60)(61)(62)(63) (Fig. 6), there is much less known regarding the host immune responses in vivo to this group of organisms.…”

Construction of Aminoglycoside-Sensitive Burkholderia cenocepacia Strains for Use in Studies of Intracellular Bacteria with the Gentamicin Protection Assay

“…However, the capacity for intracellular replication of B. cenocepacia in eukaryotic cells and the factors involved in bacterial survival remain unclear. Some studies have reported that B. cenocepacia and other Bcc strains can replicate inside eukaryotic cells (6,31,36,40,46,47,59) while others have shown minimal to no replication (29,30,39,45) (Table 1 summarizes intracellular survival/replication assays with Burkholderia species in phagocytic cells of mammalian origin). These discrepancies could be due to variations in the experimental procedure, including differences in eukaryotic cell types and Bcc strains, and the method for quantification of intracellular replication.…”