Image_3_Subversion of a family of antimicrobial proteins by Salmonella enterica.tif

Salmonella enterica is a food-borne pathogen able to cause a wide spectrum of diseases ranging from mild gastroenteritis to systemic infections. During almost all stages of the infection process Salmonella is likely to be exposed to a wide variety of host-derived antimicrobial peptides (AMPs). AMPs are important components of the innate immune response which integrate within the bacterial membrane, thus forming pores which lead ultimately to bacterial killing. In contrast to other AMPs Bactericidal/Permeability-increasing Protein (BPI) displayed only weak bacteriostatic or bactericidal effects towards Salmonella enterica sv. Typhimurium (STM) cultures. Surprisingly, we found that sub-antimicrobial concentrations of BPI fold-containing (BPIF) superfamily members mediated adhesion of STM depending on pre-formed type 1 fimbriae. BPIF proteins directly bind to type 1 fimbriae through mannose-containing oligosaccharide modifications. Fimbriae decorated with BPIF proteins exhibit extended binding specificity, allowing for bacterial adhesion on a greater variety of abiotic and biotic surfaces likely promoting host colonization. Further, fimbriae significantly contributed to the resistance against BPI, probably through sequestration of the AMP before membrane interaction. In conclusion, functional subversion of innate immune proteins of the BPIF family through binding to fimbriae promotes Salmonella virulence by survival of host defense and promotion of host colonization.</p

Table_2_Subversion of a family of antimicrobial proteins by Salmonella enterica.xlsx

Salmonella enterica is a food-borne pathogen able to cause a wide spectrum of diseases ranging from mild gastroenteritis to systemic infections. During almost all stages of the infection process Salmonella is likely to be exposed to a wide variety of host-derived antimicrobial peptides (AMPs). AMPs are important components of the innate immune response which integrate within the bacterial membrane, thus forming pores which lead ultimately to bacterial killing. In contrast to other AMPs Bactericidal/Permeability-increasing Protein (BPI) displayed only weak bacteriostatic or bactericidal effects towards Salmonella enterica sv. Typhimurium (STM) cultures. Surprisingly, we found that sub-antimicrobial concentrations of BPI fold-containing (BPIF) superfamily members mediated adhesion of STM depending on pre-formed type 1 fimbriae. BPIF proteins directly bind to type 1 fimbriae through mannose-containing oligosaccharide modifications. Fimbriae decorated with BPIF proteins exhibit extended binding specificity, allowing for bacterial adhesion on a greater variety of abiotic and biotic surfaces likely promoting host colonization. Further, fimbriae significantly contributed to the resistance against BPI, probably through sequestration of the AMP before membrane interaction. In conclusion, functional subversion of innate immune proteins of the BPIF family through binding to fimbriae promotes Salmonella virulence by survival of host defense and promotion of host colonization.</p

Image_1_Subversion of a family of antimicrobial proteins by Salmonella enterica.tif

Salmonella enterica is a food-borne pathogen able to cause a wide spectrum of diseases ranging from mild gastroenteritis to systemic infections. During almost all stages of the infection process Salmonella is likely to be exposed to a wide variety of host-derived antimicrobial peptides (AMPs). AMPs are important components of the innate immune response which integrate within the bacterial membrane, thus forming pores which lead ultimately to bacterial killing. In contrast to other AMPs Bactericidal/Permeability-increasing Protein (BPI) displayed only weak bacteriostatic or bactericidal effects towards Salmonella enterica sv. Typhimurium (STM) cultures. Surprisingly, we found that sub-antimicrobial concentrations of BPI fold-containing (BPIF) superfamily members mediated adhesion of STM depending on pre-formed type 1 fimbriae. BPIF proteins directly bind to type 1 fimbriae through mannose-containing oligosaccharide modifications. Fimbriae decorated with BPIF proteins exhibit extended binding specificity, allowing for bacterial adhesion on a greater variety of abiotic and biotic surfaces likely promoting host colonization. Further, fimbriae significantly contributed to the resistance against BPI, probably through sequestration of the AMP before membrane interaction. In conclusion, functional subversion of innate immune proteins of the BPIF family through binding to fimbriae promotes Salmonella virulence by survival of host defense and promotion of host colonization.</p

Table_1_Subversion of a family of antimicrobial proteins by Salmonella enterica.xlsx

Salmonella enterica is a food-borne pathogen able to cause a wide spectrum of diseases ranging from mild gastroenteritis to systemic infections. During almost all stages of the infection process Salmonella is likely to be exposed to a wide variety of host-derived antimicrobial peptides (AMPs). AMPs are important components of the innate immune response which integrate within the bacterial membrane, thus forming pores which lead ultimately to bacterial killing. In contrast to other AMPs Bactericidal/Permeability-increasing Protein (BPI) displayed only weak bacteriostatic or bactericidal effects towards Salmonella enterica sv. Typhimurium (STM) cultures. Surprisingly, we found that sub-antimicrobial concentrations of BPI fold-containing (BPIF) superfamily members mediated adhesion of STM depending on pre-formed type 1 fimbriae. BPIF proteins directly bind to type 1 fimbriae through mannose-containing oligosaccharide modifications. Fimbriae decorated with BPIF proteins exhibit extended binding specificity, allowing for bacterial adhesion on a greater variety of abiotic and biotic surfaces likely promoting host colonization. Further, fimbriae significantly contributed to the resistance against BPI, probably through sequestration of the AMP before membrane interaction. In conclusion, functional subversion of innate immune proteins of the BPIF family through binding to fimbriae promotes Salmonella virulence by survival of host defense and promotion of host colonization.</p

Image_4_Subversion of a family of antimicrobial proteins by Salmonella enterica.tif

Salmonella enterica is a food-borne pathogen able to cause a wide spectrum of diseases ranging from mild gastroenteritis to systemic infections. During almost all stages of the infection process Salmonella is likely to be exposed to a wide variety of host-derived antimicrobial peptides (AMPs). AMPs are important components of the innate immune response which integrate within the bacterial membrane, thus forming pores which lead ultimately to bacterial killing. In contrast to other AMPs Bactericidal/Permeability-increasing Protein (BPI) displayed only weak bacteriostatic or bactericidal effects towards Salmonella enterica sv. Typhimurium (STM) cultures. Surprisingly, we found that sub-antimicrobial concentrations of BPI fold-containing (BPIF) superfamily members mediated adhesion of STM depending on pre-formed type 1 fimbriae. BPIF proteins directly bind to type 1 fimbriae through mannose-containing oligosaccharide modifications. Fimbriae decorated with BPIF proteins exhibit extended binding specificity, allowing for bacterial adhesion on a greater variety of abiotic and biotic surfaces likely promoting host colonization. Further, fimbriae significantly contributed to the resistance against BPI, probably through sequestration of the AMP before membrane interaction. In conclusion, functional subversion of innate immune proteins of the BPIF family through binding to fimbriae promotes Salmonella virulence by survival of host defense and promotion of host colonization.</p

Image_2_Subversion of a family of antimicrobial proteins by Salmonella enterica.tif

Salmonella enterica is a food-borne pathogen able to cause a wide spectrum of diseases ranging from mild gastroenteritis to systemic infections. During almost all stages of the infection process Salmonella is likely to be exposed to a wide variety of host-derived antimicrobial peptides (AMPs). AMPs are important components of the innate immune response which integrate within the bacterial membrane, thus forming pores which lead ultimately to bacterial killing. In contrast to other AMPs Bactericidal/Permeability-increasing Protein (BPI) displayed only weak bacteriostatic or bactericidal effects towards Salmonella enterica sv. Typhimurium (STM) cultures. Surprisingly, we found that sub-antimicrobial concentrations of BPI fold-containing (BPIF) superfamily members mediated adhesion of STM depending on pre-formed type 1 fimbriae. BPIF proteins directly bind to type 1 fimbriae through mannose-containing oligosaccharide modifications. Fimbriae decorated with BPIF proteins exhibit extended binding specificity, allowing for bacterial adhesion on a greater variety of abiotic and biotic surfaces likely promoting host colonization. Further, fimbriae significantly contributed to the resistance against BPI, probably through sequestration of the AMP before membrane interaction. In conclusion, functional subversion of innate immune proteins of the BPIF family through binding to fimbriae promotes Salmonella virulence by survival of host defense and promotion of host colonization.</p

Human BPI-peptide damages the IAV particles.

<p>Virus particles were incubated either with 100 (100) and 500 μg/mL (500) of human (A) or murine BPI-peptides (B) for 1 h or left untreated (C). After the incubation the virus particles were visualized by transmission electron microscopy. Therefore, the particles were negatively stained with 2% uranylacetate and transmission electron microscopy was carried out using a JEOL TEM 2100 at 120kV. Micrographs were recorded with a fast-scan 2k x 2k CCD camera F214. One representative experiment out of 3 performed is displayed.</p

Human BPI-peptide specifically inhibits the replication of different IAV strains.

<p>Protease-deficient MDCK(H) cells were infected with 500 PFU/well of Influenza A virus strain A/PR/8/34 (H1N1) (A) and strain A/Aichi/2/68 (H3N2) (B) for 1 h. After the infection the virus containing supernatant was removed and the cells were grown for additional 13 h. Thereafter, the fixed and permeabilized cells were incubated with the mouse anti–nucleoprotein IAV monoclonal antibody. The binding of the antibody was detected by a donkey anti-mouse IgG-HRP antiserum and adding the reagent TMB Super Sensitive One Component HRP Microwell Substrate. Substrate conversion was detected by 450 nm. For the control sample is n = 8 ± SEM, all other samples n = 5 ± SEM. C) Calu-3 cells were infected with 300 PFU/well of Influenza A virus strain A/Aichi/2/68 (H3N2). Prior to the infection the virus was incubated in the presence or absences of the indicated amount of human or mouse BPI-peptide for 1 h. Thereafter, the virus solution was removed and the cells were incubated for 24 h. The virus amount in the supernatant was analysed by adding an aliquot of the supernatant to MDCK (H) cells for 1 h. After the infection the virus containing supernatant was removed and the cells were grown for additional 13 h. Thereafter, the fixed and permeabilized cells were incubated with the mouse anti–nucleoprotein IAV monoclonal antibody and detected as outlined above. (D) Furthermore, also the release of CCL5 into the supernatant of the infected Calu-3 cells was determined via a specific ELISA. One representative experiment out of 5 performed is displayed. Statistically significant differences are given as p values (** <0.01 and *** <0.001); n.s. is not significant; n = 3 ± SEM.</p

BPI peptides used.

<p>BPI peptides used.</p

Mutant human BPI-peptide corresponding to the mouse peptide loose its activity and human BPI peptide inhibits the replication of VSV.

<p>BHK-cells were infected with 360 PFU/well of VSV-GFP virus. Prior to infection the VSV was incubated with 20 μg/mL of human BPI (huBPI) and mouse BPI-peptide (mBPI), respectively or remained untreated (control) for 1 h. After 1.5 h of the cells were overlaid with 1.25% Avicel medium and incubated for 42 h. Thereafter, the cells were fixed and stained with crystal violet for 1 h at 4°C. Finally the plaques were counted (A). MDCK(H) cells were infected with 500 PFU/well Influenza A virus strain A/PR/8/34 (H1N1) for 1 h. Before the infection the virus was incubated in the presence or absence of 20 μg/mL of either human BPI-peptide (huBPI), murine BPI-peptide (mBPI), human BPI-peptide ^N1^D (mutant 1), human BPI-peptide ^K11^M (mutant 2), human BPI-peptide ^N1^D and ^K11^M (mutant 3) or left untreated (control) for 1 h (B) or incubated in the presence or absence of 20 μg/mL of either human BPI-peptide (huBPI), murine BPI-peptide (mBPI), mouse BPI-peptide ^D1^N and ^M11^K (mutant 4) or left untreated (control) for 1 h (C). After the infection the virus containing supernatant was removed and the cells were grown for additional 13 h. Thereafter, the fixed and permeabilized cells were incubated with the mouse anti–nucleoprotein IAV monoclonal antibody. The binding of the antibody was detected by a donkey anti-mouse IgG-HRP antiserum and adding of the reagent TMB Super Sensitive One Component HRP Microwell Substrate. Substrate conversion was detected by 450 nm. One representative experiment out of 3 performed is shown. Statistically significant differences are given as p values (*** <0.001); n.s. is not significant; n = 5 ± SEM.</p