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Oxidation by neutrophils-derived HOCl increases immunogenicity of proteins by converting them into ligands of several endocytic receptors involved in antigen uptake by dendritic cells and macrophages.

Biedroń R, Konopiński MK, Marcinkiewicz J, Józefowski S - PLoS ONE (2015)

Bottom Line: Paradoxically, endocytic receptors involved in antigen uptake do not bind the majority of proteins, which may be the main reason why purified proteins stimulate at most weak immune responses.Other scavenger receptors, SREC-I and LOX-1, as well as RAGE were also able to bind HOCl-modified proteins, but they did not contribute significantly to these ligands uptake by dendritic cells because they were either not expressed or exhibited preference for more heavily oxidised proteins.Our results indicate that oxidation by neutrophils-derived HOCl may be a physiological mechanism of conferring immunogenicity on proteins which in their native forms do not bind to endocytic receptors.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Jagiellonian University Medical College, Cracow, Poland.

ABSTRACT
The initiation of adaptive immune responses to protein antigens has to be preceded by their uptake by antigen presenting cells and intracellular proteolytic processing. Paradoxically, endocytic receptors involved in antigen uptake do not bind the majority of proteins, which may be the main reason why purified proteins stimulate at most weak immune responses. A shared feature of different types of adjuvants, capable of boosting immunogenicity of protein vaccines, is their ability to induce acute inflammation, characterized by early influx of activated neutrophils. Neutrophils are also rapidly recruited to sites of tissue injury or infection. These cells are the source of potent oxidants, including hypochlorous acid (HOCl), causing oxidation of proteins present in inflammatory foci. We demonstrate that oxidation of proteins by endogenous, neutrophils-derived HOCl increases their immunogenicity. Upon oxidation, different, randomly chosen simple proteins (yeast alcohol dehydrogenase, human and bovine serum albumin) and glycoproteins (human apo-transferrin, ovalbumin) gain the ability to bind with high affinity to several endocytic receptors on antigen presenting cells, which seems to be the major mechanism of their increased immunogenicity. The mannose receptor (CD206), scavenger receptors A (CD204) and CD36 were responsible for the uptake and presentation of HOCl-modified proteins by murine dendritic cells and macrophages. Other scavenger receptors, SREC-I and LOX-1, as well as RAGE were also able to bind HOCl-modified proteins, but they did not contribute significantly to these ligands uptake by dendritic cells because they were either not expressed or exhibited preference for more heavily oxidised proteins. Our results indicate that oxidation by neutrophils-derived HOCl may be a physiological mechanism of conferring immunogenicity on proteins which in their native forms do not bind to endocytic receptors. This mechanism might enable the immune system to detect infections caused by pathogens not recognized by pattern recognition receptors.

No MeSH data available.


Related in: MedlinePlus

LPS and SR-A ligands regulate uptake, acidification and proteolysis of endocytosed antigens.(A) Effects of 1-day pre-treatment with 100 ng/ml LPS on the total uptake of AF-OVA-Cl, internalisation of pHr-OVA-Cl and degradation of DQ-OVA by BM-DC and PEM. (B, C) Effects on indicated ligands on the acidification of pHr-OVA-Cl-containing endosomes (B) and proteolytic digestion of DQ-OVA (C) in BM-DC and PEM. The results shown are averages +SEM from 3 independent experiments, each performed in 4 replicates. The data were analysed by the Student’s t-test (A) or by ANOVA, with the Dunnett’s post-test applied to compare the control (“medium”) with other groups (B, C). *, p < 0.05.
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pone.0123293.g011: LPS and SR-A ligands regulate uptake, acidification and proteolysis of endocytosed antigens.(A) Effects of 1-day pre-treatment with 100 ng/ml LPS on the total uptake of AF-OVA-Cl, internalisation of pHr-OVA-Cl and degradation of DQ-OVA by BM-DC and PEM. (B, C) Effects on indicated ligands on the acidification of pHr-OVA-Cl-containing endosomes (B) and proteolytic digestion of DQ-OVA (C) in BM-DC and PEM. The results shown are averages +SEM from 3 independent experiments, each performed in 4 replicates. The data were analysed by the Student’s t-test (A) or by ANOVA, with the Dunnett’s post-test applied to compare the control (“medium”) with other groups (B, C). *, p < 0.05.

Mentions: In addition to the up-regulation of co-stimulatory molecules expression and induction of cytokine production in APC, the adjuvant effect of TLR agonists has also been suggested to involve stimulation of antigen processing [43]. The overnight pre-treatment with LPS strongly inhibited, by ~59%, uptake of AF-OVA-Cl by BM-DC (Fig 11A). In LPS-pre-treated BM-DC acidification of internalised pHr-OVA-Cl and degradation of DQ-OVA were less strongly decreased, by ~51–52%, indicating that in LPS-pre-treated BM-DC strongly decreased uptake of antigens is accompanied by their slightly (by ~20%) enhanced lysosomal degradation. In contrast, in PEM pre-treatment with LPS did not affect the uptake level of AF-OVA-Cl, but decreased by ~23% both pHr-OVA-Cl delivery into acidic endosomes and proteolytic degradation of DQ-OVA (Fig 11A).


Oxidation by neutrophils-derived HOCl increases immunogenicity of proteins by converting them into ligands of several endocytic receptors involved in antigen uptake by dendritic cells and macrophages.

Biedroń R, Konopiński MK, Marcinkiewicz J, Józefowski S - PLoS ONE (2015)

LPS and SR-A ligands regulate uptake, acidification and proteolysis of endocytosed antigens.(A) Effects of 1-day pre-treatment with 100 ng/ml LPS on the total uptake of AF-OVA-Cl, internalisation of pHr-OVA-Cl and degradation of DQ-OVA by BM-DC and PEM. (B, C) Effects on indicated ligands on the acidification of pHr-OVA-Cl-containing endosomes (B) and proteolytic digestion of DQ-OVA (C) in BM-DC and PEM. The results shown are averages +SEM from 3 independent experiments, each performed in 4 replicates. The data were analysed by the Student’s t-test (A) or by ANOVA, with the Dunnett’s post-test applied to compare the control (“medium”) with other groups (B, C). *, p < 0.05.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4388828&req=5

pone.0123293.g011: LPS and SR-A ligands regulate uptake, acidification and proteolysis of endocytosed antigens.(A) Effects of 1-day pre-treatment with 100 ng/ml LPS on the total uptake of AF-OVA-Cl, internalisation of pHr-OVA-Cl and degradation of DQ-OVA by BM-DC and PEM. (B, C) Effects on indicated ligands on the acidification of pHr-OVA-Cl-containing endosomes (B) and proteolytic digestion of DQ-OVA (C) in BM-DC and PEM. The results shown are averages +SEM from 3 independent experiments, each performed in 4 replicates. The data were analysed by the Student’s t-test (A) or by ANOVA, with the Dunnett’s post-test applied to compare the control (“medium”) with other groups (B, C). *, p < 0.05.
Mentions: In addition to the up-regulation of co-stimulatory molecules expression and induction of cytokine production in APC, the adjuvant effect of TLR agonists has also been suggested to involve stimulation of antigen processing [43]. The overnight pre-treatment with LPS strongly inhibited, by ~59%, uptake of AF-OVA-Cl by BM-DC (Fig 11A). In LPS-pre-treated BM-DC acidification of internalised pHr-OVA-Cl and degradation of DQ-OVA were less strongly decreased, by ~51–52%, indicating that in LPS-pre-treated BM-DC strongly decreased uptake of antigens is accompanied by their slightly (by ~20%) enhanced lysosomal degradation. In contrast, in PEM pre-treatment with LPS did not affect the uptake level of AF-OVA-Cl, but decreased by ~23% both pHr-OVA-Cl delivery into acidic endosomes and proteolytic degradation of DQ-OVA (Fig 11A).

Bottom Line: Paradoxically, endocytic receptors involved in antigen uptake do not bind the majority of proteins, which may be the main reason why purified proteins stimulate at most weak immune responses.Other scavenger receptors, SREC-I and LOX-1, as well as RAGE were also able to bind HOCl-modified proteins, but they did not contribute significantly to these ligands uptake by dendritic cells because they were either not expressed or exhibited preference for more heavily oxidised proteins.Our results indicate that oxidation by neutrophils-derived HOCl may be a physiological mechanism of conferring immunogenicity on proteins which in their native forms do not bind to endocytic receptors.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Jagiellonian University Medical College, Cracow, Poland.

ABSTRACT
The initiation of adaptive immune responses to protein antigens has to be preceded by their uptake by antigen presenting cells and intracellular proteolytic processing. Paradoxically, endocytic receptors involved in antigen uptake do not bind the majority of proteins, which may be the main reason why purified proteins stimulate at most weak immune responses. A shared feature of different types of adjuvants, capable of boosting immunogenicity of protein vaccines, is their ability to induce acute inflammation, characterized by early influx of activated neutrophils. Neutrophils are also rapidly recruited to sites of tissue injury or infection. These cells are the source of potent oxidants, including hypochlorous acid (HOCl), causing oxidation of proteins present in inflammatory foci. We demonstrate that oxidation of proteins by endogenous, neutrophils-derived HOCl increases their immunogenicity. Upon oxidation, different, randomly chosen simple proteins (yeast alcohol dehydrogenase, human and bovine serum albumin) and glycoproteins (human apo-transferrin, ovalbumin) gain the ability to bind with high affinity to several endocytic receptors on antigen presenting cells, which seems to be the major mechanism of their increased immunogenicity. The mannose receptor (CD206), scavenger receptors A (CD204) and CD36 were responsible for the uptake and presentation of HOCl-modified proteins by murine dendritic cells and macrophages. Other scavenger receptors, SREC-I and LOX-1, as well as RAGE were also able to bind HOCl-modified proteins, but they did not contribute significantly to these ligands uptake by dendritic cells because they were either not expressed or exhibited preference for more heavily oxidised proteins. Our results indicate that oxidation by neutrophils-derived HOCl may be a physiological mechanism of conferring immunogenicity on proteins which in their native forms do not bind to endocytic receptors. This mechanism might enable the immune system to detect infections caused by pathogens not recognized by pattern recognition receptors.

No MeSH data available.


Related in: MedlinePlus