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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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Related in: MedlinePlus

Passive protection with rabbit polyclonal AT-62aa (AT62-IgG) in bacteremia model.Protection from lethal challenge with S. aureus USA300 (A) or USA400 (B) after passive immunization with polyclonal rabbit antibodies AT62-IgG (black square) compared to mock-treated mice (grey diamond). Statistical analysis was performed using Log-Rank (Mantel-Cox) test, P<0.0001.
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pone-0038567-g005: Passive protection with rabbit polyclonal AT-62aa (AT62-IgG) in bacteremia model.Protection from lethal challenge with S. aureus USA300 (A) or USA400 (B) after passive immunization with polyclonal rabbit antibodies AT62-IgG (black square) compared to mock-treated mice (grey diamond). Statistical analysis was performed using Log-Rank (Mantel-Cox) test, P<0.0001.

Mentions: We hypothesized that the remarkable efficacy observed with AT-62aa vaccine is mediated by a protective antibody response. To examine this hypothesis, polyclonal antibodies were raised against purified AT-62aa in rabbits (IBT Bioservices #04–0010) and total IgG was purified by Protein A. Naïve rabbit IgG (Equitech-Bio, Inc., Kerryville, TX) was used as control. Groups of 10 mice were passively immunized with 4 mg of rabbit polyclonal anti-AT62aa antibodies (AT62-IgG) or naïve rabbit IgG by IP injection at 24 hours before challenge with 5×104 CFU of USA300 or 1×105 CFU of USA400 (MW2) in 3% Hog mucin. As shown in Figure 5A, while nine out of ten mice immunized with naïve IgG succumbed within 48 hours, all mice immunized with AT62-IgG showed slightly ruffled coat, remained active, and survived the challenge. Similarly, while 80% of control mice challenged with MW2 died within 48 h, all mice receiving AT62-IgG survived the lethal challenge (Figure 5B).


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)

Passive protection with rabbit polyclonal AT-62aa (AT62-IgG) in bacteremia model.Protection from lethal challenge with S. aureus USA300 (A) or USA400 (B) after passive immunization with polyclonal rabbit antibodies AT62-IgG (black square) compared to mock-treated mice (grey diamond). Statistical analysis was performed using Log-Rank (Mantel-Cox) test, P<0.0001.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0038567-g005: Passive protection with rabbit polyclonal AT-62aa (AT62-IgG) in bacteremia model.Protection from lethal challenge with S. aureus USA300 (A) or USA400 (B) after passive immunization with polyclonal rabbit antibodies AT62-IgG (black square) compared to mock-treated mice (grey diamond). Statistical analysis was performed using Log-Rank (Mantel-Cox) test, P<0.0001.
Mentions: We hypothesized that the remarkable efficacy observed with AT-62aa vaccine is mediated by a protective antibody response. To examine this hypothesis, polyclonal antibodies were raised against purified AT-62aa in rabbits (IBT Bioservices #04–0010) and total IgG was purified by Protein A. Naïve rabbit IgG (Equitech-Bio, Inc., Kerryville, TX) was used as control. Groups of 10 mice were passively immunized with 4 mg of rabbit polyclonal anti-AT62aa antibodies (AT62-IgG) or naïve rabbit IgG by IP injection at 24 hours before challenge with 5×104 CFU of USA300 or 1×105 CFU of USA400 (MW2) in 3% Hog mucin. As shown in Figure 5A, while nine out of ten mice immunized with naïve IgG succumbed within 48 hours, all mice immunized with AT62-IgG showed slightly ruffled coat, remained active, and survived the challenge. Similarly, while 80% of control mice challenged with MW2 died within 48 h, all mice receiving AT62-IgG survived the lethal challenge (Figure 5B).

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