Integrin-mediated localization of Bordetella pertussis within macrophages: role in pulmonary colonization.

Abstract

SummaryThe adherence of Bordetella pertussis to human respiratory cilia is critical to the pathogenesis of whooping cough but the significance of bacterial attachment to macrophages has not been determined . Adherence to cilia and macrophages is mediated by two large, nonfimbrial bacterial proteins, filamentous hemagglutinin (FHA), and pertussis toxin (PT) . PT and FHA both recognize carbohydrates on cilia and macrophages; FHA also contains an Arg-Gly-Asp (RGD) sequence which promotes bacterial association with the macrophage integrin complement receptor 3 (CR3) . We determined that virulent R pertussis enter and survive in mammalian macrophages in vitro and that CR3 is important for this uptake process . We then determined the relative contribution of CR3 versus carbohydrate-dependent interactions to in vivo pulmonary colonization using a rabbit model. R pertussis colonized the lung as two approximately equal populations, one extracellular population attached to ciliary and macrophage surface glycoconjugates and another population within pulmonary macrophages. Loss of the CR3 interaction, either by mutation of FHA or treatment with antibody to CR3, disrupted accumulation of viable intracellular bacteria but did not prevent lung pathology. In contrast, elimination of carbohydrate-bound bacteria, either by a competitive receptor analogue or an anti-receptor antibody, was sufficient to prevent pulmonary edema. We propose that CR3-dependent localization of R pertussis within macrophages promotes persistence of bacteria in the lung without pulmonary injury. On the other hand, the presence of extracellular bacteria adherent to cilia and macrophages in carbohydrate-dependent interactions is associated with pulmonary pathology. ordetelia pertussis is a Gram-negative coccobacillus that is the causative agent of whooping cough. It has long been recognized that R pertussis establishes pulmonary colonization by adhering specifically to human ciliated epithelial cells, and this interaction has been studied in detail in vitro (1) . Recently, however, in vitro studies have shown that R pertussis also adheres specifically to human macrophages (2) and can enter and survive within tissue culture cells (3-5) . The purpose of this study was to determine the importance of the interaction between R pertussis and macrophages during pulmonary infection .Bacterial adherence to cilia and macrophages is mediated by two nonfimbrial bacterial proteins, filamentous hemagglutinin (FHA)t and pertussis toxin (PT) which are expressed only by virulent cells (1, 2) . These proteins are functional either when bound to the bacterial surface or when secreted into the surrounding medium during growth and serve as bifunctional ligands bridging the bacterial surface and glycoconjugates on eukaryotic cell membranes (1, 6). Both 'Abbreviations used in this paper. FHA, filamentous hemagglutinin ; PT, pertussis toxin; RGD, Arg-Gly-Asp sequence .adhesins are unusually large molecules with multiple binding affinities, features reminiscent of eukaryotic extra...

Exploiting Type 3 Complement Receptor for TNF-α Suppression, Immune Evasion, and Progressive Pulmonary Fungal Infection

“…Loss of the CR3 interaction, by either mutation of filamentous hemagglutinin or treatment with Ab to CR3, blocks the accumulation of viable intracellular bacteria, but not lung pathology. In concert with these earlier findings, Hellwig et al (54) found that competition between B. pertussis uptake via CR3 or Fc␥R determines the outcome of natural infection. Thus, in vivo studies with bispecific Abs revealed that Fc␥R-mediated uptake facilitates bacterial clearance, in contrast to uptake via CR3.…”

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“…The adherence of H. influenzae to mammalian cells is partly mediated by high-molecular-weight proteins (22) closely related to Bordetella pertussis filamentous hemagglutinin, which is a 220-kDa protein with several binding sites, of which one binds galactose-containing glycoconjugates (e.g., lactose and lactosamine), thereby promoting adhesion to epithelial cells, and another recognizes the macrophage integrin complement receptor CR3, which is important for the intracellular uptake process (17). It is known that particles phagocytosed via CR3 do not engender an oxidative burst, suggesting that this route of entry might promote survival within the macrophage (17).…”

Fc Receptor-Mediated Immunity Against Bordetella pertussis

“…In addition, bacterial constituents including fimbriae, pertussis toxin, and FHA up-regulate CR3 expression, suggesting that nonopsonized B. pertussis may stimulate its own attachment to immune cells (9,13,15). Both in vitro and in vivo studies provided evidence that uptake via CR3 does not lead to efficient bacterial killing by phagocytes, thus favoring intracellular survival (7,16,17).…”