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Priming of Salmonella enterica serovar typhi-specific CD8(+) T cells by suicide dendritic cell cross-presentation in humans.

Salerno-Goncalves R, Sztein MB - PLoS ONE (2009)

Bottom Line: Typhi-infected human cells and release high levels of IFN-gamma and IL-12p70, leading to the subsequent presentation of bacterial antigens and triggering the induction of memory T cells, mostly CD3(+)CD8(+)CD45RA(-)CD62L(-) effector/memory T cells.This study is the first to demonstrate the effect of S.Typhi.

View Article: PubMed Central - PubMed

Affiliation: Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD, USA. rmezghan@medicine.umaryland.edu

ABSTRACT

Background: The emergence of antibiotic-resistant strains of Salmonella enterica serovar Typhi (S. Typhi), the etiologic agent of typhoid fever, has aggravated an already important public health problem and added new urgency to the development of more effective typhoid vaccines. To this end it is critical to better understand the induction of immunity to S. Typhi. CD8(+) T cells are likely to play an important role in host defense against S. Typhi by several effector mechanisms, including killing of infected cells and IFN-gamma secretion. However, how S. Typhi regulates the development of specific CD8(+) responses in humans remains unclear. Recent studies in mice have shown that dendritic cells (DC) can either directly (upon uptake and processing of Salmonella) or indirectly (by bystander mechanisms) elicit Salmonella-specific CD8(+) T cells.

Methodology/principal findings: We report here that upon infection with live S. Typhi, human DC produced high levels of pro-inflammatory cytokines IL-6, IL-8 and TNF-alpha, but low levels of IL-12 p70 and IFN-gamma. In contrast, DC co-cultured with S. Typhi-infected cells, through suicide cross-presentation, uptake S. Typhi-infected human cells and release high levels of IFN-gamma and IL-12p70, leading to the subsequent presentation of bacterial antigens and triggering the induction of memory T cells, mostly CD3(+)CD8(+)CD45RA(-)CD62L(-) effector/memory T cells.

Conclusions/significance: This study is the first to demonstrate the effect of S. Typhi on human DC maturation and on their ability to prime CD8(+) cells and highlights the significance of these phenomena in eliciting adaptive immunity to S. Typhi.

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Cross-priming DC are the most effective stimulus in promoting the expansion of S. Typhi-specific T cells.Net frequencies of IFN-γ-spot forming cells (SFC) were assessed by an IFN-γ ELISPOT assay using in vitro expanded PBMC as effectors and autologous blasts infected with live S. Typhi as stimulators. PBMC were co-cultured with their own DC alone or DC that had been pulsed with live or heat-killed S. Typhi, or uninfected or S. Typhi-infected autologous blasts at a 1∶4 blast∶DC ratio. Net frequencies of IFN-γ SFC were calculated as described in Materials and Methods. The dashed line represents the cut-off for positive-ELISPOT assays determined as described in Materials and Methods. Bar graphs show means+SE of 3 experiments using 4 different donors (*, p<0.05 compared with DC pulsed with S. Typhi-infected cells).
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pone-0005879-g010: Cross-priming DC are the most effective stimulus in promoting the expansion of S. Typhi-specific T cells.Net frequencies of IFN-γ-spot forming cells (SFC) were assessed by an IFN-γ ELISPOT assay using in vitro expanded PBMC as effectors and autologous blasts infected with live S. Typhi as stimulators. PBMC were co-cultured with their own DC alone or DC that had been pulsed with live or heat-killed S. Typhi, or uninfected or S. Typhi-infected autologous blasts at a 1∶4 blast∶DC ratio. Net frequencies of IFN-γ SFC were calculated as described in Materials and Methods. The dashed line represents the cut-off for positive-ELISPOT assays determined as described in Materials and Methods. Bar graphs show means+SE of 3 experiments using 4 different donors (*, p<0.05 compared with DC pulsed with S. Typhi-infected cells).

Mentions: We next examined the ability of primed T cells to expand. Eight to twelve days after co-culture of PBMC with DC under the various culture conditions discussed above, the frequency of S. Typhi-specificity of PBMC was evaluated by their capacity to secrete IFN-γ by ELISPOT. Significant increases in net frequencies of IFN-γ-SFC were observed between PBMC previously stimulated with DC pulsed with S. Typhi-infected cells and all other groups (Fig. 10). Although frequencies above the threshold of positive IFN-γ-SFC responses were observed in PBMC following stimulation with DC pulsed with live S. Typhi, no statistically significant differences were observed among these frequencies and the frequencies observed in cultures with heated S. Typhi, uninfected blasts and media controls (Fig. 10). Taken together, these observations suggest that DC cross-priming is very effective in promoting the expansion of S. Typhi-specific T cells.


Priming of Salmonella enterica serovar typhi-specific CD8(+) T cells by suicide dendritic cell cross-presentation in humans.

Salerno-Goncalves R, Sztein MB - PLoS ONE (2009)

Cross-priming DC are the most effective stimulus in promoting the expansion of S. Typhi-specific T cells.Net frequencies of IFN-γ-spot forming cells (SFC) were assessed by an IFN-γ ELISPOT assay using in vitro expanded PBMC as effectors and autologous blasts infected with live S. Typhi as stimulators. PBMC were co-cultured with their own DC alone or DC that had been pulsed with live or heat-killed S. Typhi, or uninfected or S. Typhi-infected autologous blasts at a 1∶4 blast∶DC ratio. Net frequencies of IFN-γ SFC were calculated as described in Materials and Methods. The dashed line represents the cut-off for positive-ELISPOT assays determined as described in Materials and Methods. Bar graphs show means+SE of 3 experiments using 4 different donors (*, p<0.05 compared with DC pulsed with S. Typhi-infected cells).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2691582&req=5

pone-0005879-g010: Cross-priming DC are the most effective stimulus in promoting the expansion of S. Typhi-specific T cells.Net frequencies of IFN-γ-spot forming cells (SFC) were assessed by an IFN-γ ELISPOT assay using in vitro expanded PBMC as effectors and autologous blasts infected with live S. Typhi as stimulators. PBMC were co-cultured with their own DC alone or DC that had been pulsed with live or heat-killed S. Typhi, or uninfected or S. Typhi-infected autologous blasts at a 1∶4 blast∶DC ratio. Net frequencies of IFN-γ SFC were calculated as described in Materials and Methods. The dashed line represents the cut-off for positive-ELISPOT assays determined as described in Materials and Methods. Bar graphs show means+SE of 3 experiments using 4 different donors (*, p<0.05 compared with DC pulsed with S. Typhi-infected cells).
Mentions: We next examined the ability of primed T cells to expand. Eight to twelve days after co-culture of PBMC with DC under the various culture conditions discussed above, the frequency of S. Typhi-specificity of PBMC was evaluated by their capacity to secrete IFN-γ by ELISPOT. Significant increases in net frequencies of IFN-γ-SFC were observed between PBMC previously stimulated with DC pulsed with S. Typhi-infected cells and all other groups (Fig. 10). Although frequencies above the threshold of positive IFN-γ-SFC responses were observed in PBMC following stimulation with DC pulsed with live S. Typhi, no statistically significant differences were observed among these frequencies and the frequencies observed in cultures with heated S. Typhi, uninfected blasts and media controls (Fig. 10). Taken together, these observations suggest that DC cross-priming is very effective in promoting the expansion of S. Typhi-specific T cells.

Bottom Line: Typhi-infected human cells and release high levels of IFN-gamma and IL-12p70, leading to the subsequent presentation of bacterial antigens and triggering the induction of memory T cells, mostly CD3(+)CD8(+)CD45RA(-)CD62L(-) effector/memory T cells.This study is the first to demonstrate the effect of S.Typhi.

View Article: PubMed Central - PubMed

Affiliation: Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD, USA. rmezghan@medicine.umaryland.edu

ABSTRACT

Background: The emergence of antibiotic-resistant strains of Salmonella enterica serovar Typhi (S. Typhi), the etiologic agent of typhoid fever, has aggravated an already important public health problem and added new urgency to the development of more effective typhoid vaccines. To this end it is critical to better understand the induction of immunity to S. Typhi. CD8(+) T cells are likely to play an important role in host defense against S. Typhi by several effector mechanisms, including killing of infected cells and IFN-gamma secretion. However, how S. Typhi regulates the development of specific CD8(+) responses in humans remains unclear. Recent studies in mice have shown that dendritic cells (DC) can either directly (upon uptake and processing of Salmonella) or indirectly (by bystander mechanisms) elicit Salmonella-specific CD8(+) T cells.

Methodology/principal findings: We report here that upon infection with live S. Typhi, human DC produced high levels of pro-inflammatory cytokines IL-6, IL-8 and TNF-alpha, but low levels of IL-12 p70 and IFN-gamma. In contrast, DC co-cultured with S. Typhi-infected cells, through suicide cross-presentation, uptake S. Typhi-infected human cells and release high levels of IFN-gamma and IL-12p70, leading to the subsequent presentation of bacterial antigens and triggering the induction of memory T cells, mostly CD3(+)CD8(+)CD45RA(-)CD62L(-) effector/memory T cells.

Conclusions/significance: This study is the first to demonstrate the effect of S. Typhi on human DC maturation and on their ability to prime CD8(+) cells and highlights the significance of these phenomena in eliciting adaptive immunity to S. Typhi.

Show MeSH
Related in: MedlinePlus