Experimental exposure of Burkholderia pseudomallei crude culture filtrate upregulates PD-1 on T lymphocytes

Abstract

Burkholderia pseudomallei is the causative agent for melioidosis. Because of its intracellular nature, the bacterium is capable of replicating within a plethora of eukaryotic cell lines. B. pseudomallei can remain dormant within host cells without symptoms for years, causing recrudescent infections. Here, we investigated the pathogenesis mechanism behind the suppression of T cell responses by B. pseudomallei . Peripheral blood mononuclear cells (1×10 6 cells/well) isolated by Ficoll Paque (Sigma-Aldrich) density gradient centrifugation were incubated with optimized concentrations of bacterial crude culture filtrate antigens (CFAs) (10 ug ml −1 ) and heat-killed bacteria [1 : 10 multiplicity of infection (m.o.i.)]. Following incubation, cells were investigated for surface expression of coinhibitory molecules by flow cytometry. We found that B. pseudomallei induced the upregulation of programmed death 1 (PD-1), a molecule responsible for T cell exhaustion, on T cells in vitro following exposure to crude CFAs of B. pseudomallei . This upregulation of PD-1 probably contributes to poor immune surveillance and disease pathogenesis.

Dysfunctional host cellular immune responses are associated with mortality in melioidosis

“…While this may represent a unique inflammatory response to melioidosis, this lack of acquisition of a polyfunctional T cell response could also represent T cell exhaustion. Evidence of pathologic T cell exhaustion is limited in melioidosis but increased T cell expression of PD-1 can be induced during B. pseudomallei infection in vitro [ 43 , 44 ]. In our study, the overall increase in both T cell population frequency and effector memory phenotype over time in survivors suggests that any active T cell suppression during acute infection improves within weeks, and that T cell memory responses that develop may potentially provide immunity in the event of future exposure to B. pseudomallei .…”

Hijacking of the Host’s Immune Surveillance Radars by Burkholderia pseudomallei

“…Recently, Menon et al. (2020) ( 116 ) demonstrated up-regulation of PD-1 on T cells in vitro , upon exposure to crude culture filtrate antigens of B. pseudomallei and suggested that this possibly contributes to deprived immune surveillance and pathogenesis.…”

“…According to a study by Khakhum et al. (2019) ( 116 ), IgG and their subclasses are inevitably significant in the detection of B. pseudomallei infection. Besides, a few scientific findings revealed that a discerning absence of one or more IgG sub-classes likely increases the susceptibility to recurrent infections or extend the course of an established infection.…”

“…This likely could be attributed to the presence of high levels of B. pseudomallei-specific IgG, IgM, and IgA antibodies in melioidosis patients' sera, which persistently raised for the length of infection (106,117). According to a study by Khakhum et al (2019) (116), IgG and their subclasses are inevitably significant in the detection of B. pseudomallei infection. Besides, a few scientific findings revealed that a discerning absence of one or more IgG sub-classes likely increases the susceptibility to recurrent infections or extend the course of an established infection.…”

Release of pro-inflammatory cytokines TNF-α, IFN-γ and IL-6 by Burkholderia pseudomallei- stimulated peripheral blood mononucleocytes of acute myeloid leukemia patients

“…Three bacterial strains were used: two isolates of B. pseudomallei clinical isolates obtained from University Malaya Medical Center (UMMC), OB (WT, INSDC: APLK00000000.1) and OS (SCV, INSDC: APLL00000000.1) and K9 (B. pseudomallei K96243) isolated from a melioidosis patient in Thailand and is commonly used as a reference strain. Characterization of all strains were performed using analytical profile index API 20NE (BioMrieux) test and PCR assay specific for B. pseudomallei (Menon et al, 2020). All of them were cultured in Luria-Bertani (LB) broth in a shaking incubator (37°C at 200 rpm).…”