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Novel structurally designed vaccine for S. aureus α-hemolysin: protection against bacteremia and pneumonia.

Adhikari RP, Karauzum H, Sarwar J, Abaandou L, Mahmoudieh M, Boroun AR, Vu H, Nguyen T, Devi VS, Shulenin S, Warfield KL, Aman MJ - PLoS ONE (2012)

Bottom Line: Efforts to develop effective vaccines against S. aureus have been largely unsuccessful, in part due to the variety of virulence factors produced by this organism.Our Hla-based vaccine is the first to be reported to reduce bacterial dissemination and to provide protection in a sepsis model of S. aureus infection.AT62-IgG and sera from vaccinated mice effectively neutralized the toxin in vitro and AT62-IgG inhibited the formation of Hla heptamers, suggesting antibody-mediated neutralization as the primary mechanism of action.

View Article: PubMed Central - PubMed

Affiliation: Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America.

ABSTRACT
Staphylococcus aureus (S. aureus) is a human pathogen associated with skin and soft tissue infections (SSTI) and life threatening sepsis and pneumonia. Efforts to develop effective vaccines against S. aureus have been largely unsuccessful, in part due to the variety of virulence factors produced by this organism. S. aureus alpha-hemolysin (Hla) is a pore-forming toxin expressed by most S. aureus strains and reported to play a key role in the pathogenesis of SSTI and pneumonia. Here we report a novel recombinant subunit vaccine candidate for Hla, rationally designed based on the heptameric crystal structure. This vaccine candidate, denoted AT-62aa, was tested in pneumonia and bacteremia infection models using S. aureus strain Newman and the pandemic strain USA300 (LAC). Significant protection from lethal bacteremia/sepsis and pneumonia was observed upon vaccination with AT-62aa along with a Glucopyranosyl Lipid Adjuvant-Stable Emulsion (GLA-SE) that is currently in clinical trials. Passive transfer of rabbit immunoglobulin against AT-62aa (AT62-IgG) protected mice against intraperitoneal and intranasal challenge with USA300 and produced significant reduction in bacterial burden in blood, spleen, kidney, and lungs. Our Hla-based vaccine is the first to be reported to reduce bacterial dissemination and to provide protection in a sepsis model of S. aureus infection. AT62-IgG and sera from vaccinated mice effectively neutralized the toxin in vitro and AT62-IgG inhibited the formation of Hla heptamers, suggesting antibody-mediated neutralization as the primary mechanism of action. This remarkable efficacy makes this Hla-based vaccine a prime candidate for inclusion in future multivalent S. aureus vaccine. Furthermore, identification of protective epitopes within AT-62aa could lead to novel immunotherapy for S. aureus infection.

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Neutralization of Hla with AT62-IgG.100 ng of purified alpha toxin was pre-incubated at RT with different concentration of polyclonal antibody ranging from 500 µg/ml to 0.5 µg/ml and then incubated with 2% rabbit blood at 37°C for 30 min. The suspension was centrifuged and hemolysis was measured at OD416 nm.
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pone-0038567-g008: Neutralization of Hla with AT62-IgG.100 ng of purified alpha toxin was pre-incubated at RT with different concentration of polyclonal antibody ranging from 500 µg/ml to 0.5 µg/ml and then incubated with 2% rabbit blood at 37°C for 30 min. The suspension was centrifuged and hemolysis was measured at OD416 nm.

Mentions: To delineate the mechanism of protection by AT-62aa vaccine, we tested the effect of AT62-IgG on neutralization and oligomerization of Hla. Toxin neutralization activity of the purified polyclonal antibody was tested using rabbit red blood cells. AT62-IgG effectively inhibited RBC lysis induced by 100 ng of purified Hla (Toxin tech, FL) with an EC50 of 14 μg/ml (Figure 8).


Novel structurally designed vaccine for S. aureus α-hemolysin: protection against bacteremia and pneumonia.

Adhikari RP, Karauzum H, Sarwar J, Abaandou L, Mahmoudieh M, Boroun AR, Vu H, Nguyen T, Devi VS, Shulenin S, Warfield KL, Aman MJ - PLoS ONE (2012)

Neutralization of Hla with AT62-IgG.100 ng of purified alpha toxin was pre-incubated at RT with different concentration of polyclonal antibody ranging from 500 µg/ml to 0.5 µg/ml and then incubated with 2% rabbit blood at 37°C for 30 min. The suspension was centrifuged and hemolysis was measured at OD416 nm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368876&req=5

pone-0038567-g008: Neutralization of Hla with AT62-IgG.100 ng of purified alpha toxin was pre-incubated at RT with different concentration of polyclonal antibody ranging from 500 µg/ml to 0.5 µg/ml and then incubated with 2% rabbit blood at 37°C for 30 min. The suspension was centrifuged and hemolysis was measured at OD416 nm.
Mentions: To delineate the mechanism of protection by AT-62aa vaccine, we tested the effect of AT62-IgG on neutralization and oligomerization of Hla. Toxin neutralization activity of the purified polyclonal antibody was tested using rabbit red blood cells. AT62-IgG effectively inhibited RBC lysis induced by 100 ng of purified Hla (Toxin tech, FL) with an EC50 of 14 μg/ml (Figure 8).

Bottom Line: Efforts to develop effective vaccines against S. aureus have been largely unsuccessful, in part due to the variety of virulence factors produced by this organism.Our Hla-based vaccine is the first to be reported to reduce bacterial dissemination and to provide protection in a sepsis model of S. aureus infection.AT62-IgG and sera from vaccinated mice effectively neutralized the toxin in vitro and AT62-IgG inhibited the formation of Hla heptamers, suggesting antibody-mediated neutralization as the primary mechanism of action.

View Article: PubMed Central - PubMed

Affiliation: Integrated Biotherapeutics Inc., Gaithersburg, Maryland, United States of America.

ABSTRACT
Staphylococcus aureus (S. aureus) is a human pathogen associated with skin and soft tissue infections (SSTI) and life threatening sepsis and pneumonia. Efforts to develop effective vaccines against S. aureus have been largely unsuccessful, in part due to the variety of virulence factors produced by this organism. S. aureus alpha-hemolysin (Hla) is a pore-forming toxin expressed by most S. aureus strains and reported to play a key role in the pathogenesis of SSTI and pneumonia. Here we report a novel recombinant subunit vaccine candidate for Hla, rationally designed based on the heptameric crystal structure. This vaccine candidate, denoted AT-62aa, was tested in pneumonia and bacteremia infection models using S. aureus strain Newman and the pandemic strain USA300 (LAC). Significant protection from lethal bacteremia/sepsis and pneumonia was observed upon vaccination with AT-62aa along with a Glucopyranosyl Lipid Adjuvant-Stable Emulsion (GLA-SE) that is currently in clinical trials. Passive transfer of rabbit immunoglobulin against AT-62aa (AT62-IgG) protected mice against intraperitoneal and intranasal challenge with USA300 and produced significant reduction in bacterial burden in blood, spleen, kidney, and lungs. Our Hla-based vaccine is the first to be reported to reduce bacterial dissemination and to provide protection in a sepsis model of S. aureus infection. AT62-IgG and sera from vaccinated mice effectively neutralized the toxin in vitro and AT62-IgG inhibited the formation of Hla heptamers, suggesting antibody-mediated neutralization as the primary mechanism of action. This remarkable efficacy makes this Hla-based vaccine a prime candidate for inclusion in future multivalent S. aureus vaccine. Furthermore, identification of protective epitopes within AT-62aa could lead to novel immunotherapy for S. aureus infection.

Show MeSH
Related in: MedlinePlus