Immune response to recombinant Burkholderia pseudomallei FliC

Abstract

Burkholderia pseudomallei is a flagellated Gram-negative bacterium which is the causative agent of melioidosis. The disease poses a major public health problem in tropical regions and diabetes is a major risk factor. The high mortality rate of melioidosis is associated with severe sepsis which involves the overwhelming production of pro-inflammatory cytokines. Bacterial flagellar protein (flagellin) activates Toll-like receptor 5 (TLR5)-mediated innate immune signaling pathways and induces adaptive immune response. However, previous studies of TLR5 signaling in melioidosis have been performed using recombinant flagellin from Salmonella Typhimurium instead of B. pseudomallei. This study aimed to investigate human innate immune response and antibody response against a recombinant B. pseudomallei flagellin (rFliC). We prepared B. pseudomallei rFliC and used it to stimulate HEK-BlueTM-hTLR5 and THP1-DualTM cells to assess TLR5 activation. Subsequently, whole blood stimulation assays with rFliC were performed ex vivo. TLR5-flagellin interactions trigger activation of transcription factor NF-κB in HEK-BlueTM-hTLR5 cells. Pro-inflammatory cytokine (IL-1β, IL-6, and TNF-α) productions from whole blood in response to rFliC differed between fourteen healthy individuals. The levels of these cytokines changed in a dose and time-dependent manner. ELISA was used to determine rFliC-specific antibodies in serum samples from different groups of melioidosis patients and healthy subjects. IgG antibody to rFliC in melioidosis patients with diabetes were higher compared with non-diabetic patients. Our results show that B. pseudomallei flagellin is a potent immune stimulator and that the immune responses to rFliC are different among individuals. This may provide valuable insights toward the potential use of rFliC in vaccine development.

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“…RT-qPCR analysis of DEGs included in inflammatory response, such as IL1A, IL6, TNFAIP3, NFκB2, and GKN2 ( Figure 5), was therefore conducted. B. pseudomallei increased the mRNA expression of TNFAIP3 and IL-6 in human lung epithelial cell, which was consistent with the current research that proinflammatory mediators of TNF-α and IL-6 increased in the liver of mice following infection with B. pseudomallei and in serum samples of melioidosis patients (Ulett et al, 2000;Koosakulnirand et al, 2018). Activated UPR transcription factors can induce inflammatory response, which play an important role in the pathogenesis of inflammation (Bettigole and Glimcher, 2015).…”

Transcriptome Analysis Reveals Dynamic Changes of Inflammation and Stress Responses during Different Infected Stages with Burkholderia pseudomallei

“…In general, innate immune mechanisms are critical in determining the outcome of infections caused by bacterial pathogens. Recent studies have reported that B. pseudomallei increased the production of inflammatory cytokines such as TNF-α, IL-1β and IL-6 in vivo in serum samples of melioidosis patients [28]. Proinflammatory cytokine mRNA of TNF-α, IL-1β and IL-6 increased in the liver of mice following infected with B. pseudomallei [29].…”

Novel multi-component vaccine approaches for Burkholderia pseudomallei

“…PART 1 from human melioidosis patients as well as animal studies has greatly facilitated the selection of target antigens and rational design of candidate vaccines [33][34][35][36][37][38][39][40][41][42][43]. The identification of immunoreactive B and T cell antigens VACCINES FOR EMERGING PATHOGENS: FROM RESEARCH TO THE CLINIC.…”

“…The identification of immunoreactive B and T cell antigens VACCINES FOR EMERGING PATHOGENS: FROM RESEARCH TO THE CLINIC. PART 1 from human melioidosis patients as well as animal studies has greatly facilitated the selection of target antigens and rational design of candidate vaccines [33][34][35][36][37][38][39][40][41][42][43]. Certain bacterial antigens, such as capsule polysaccharide (CPS), FliC, BopE, AhpC and many outer membrane proteins (Omp), are routinely recognized as highly reactive with patient immune sera or peripheral blood mononuclear cells (PBMCs), and many of these antigens confer partial protection when used as individual subunit vaccines [7].…”