Protection against bacterial superantigen staphylococcal enterotoxin B by passive vaccination

Abstract

We investigated the ability of two overlapping fragments of staphylococcal enterotoxin B (SEB), which encompass the whole toxin, to induce protection and also examined if passive transfer of chicken anti-SEB antibodies raised against the holotoxin could protect rhesus monkeys against aerosolized SEB. Although both fragments of SEB were highly immunogenic, the fragments failed to protect mice whether they were injected separately or injected together. Passive transfer of antibody generated in chickens (immunoglobulin Y [IgY]) against the whole toxin suppressed cytokine responses and was protective in mice. All rhesus monkeys treated with the IgY specific for SEB up to 4 h after challenge survived lethal SEB aerosol exposure. These findings suggest that large fragments of SEB may not be ideal for productive vaccination, but passive transfer of SEB-specific antibodies protects nonhuman primates against lethal aerosol challenge. Thus, antibodies raised in chickens against the holotoxin may have potential therapeutic value within a therapeutic window of opportunity after SEB encounter.

FIG. 1.

Passive transfer of chicken-derived anti-SEB antibody to mice inhibits SEB-induced TNF-α and IFN-γ release. SEB (5 μg/mouse) was incubated for 1 h at 37°C with anti-SEB IgY or PBS. Mice were given the mixture, and then they were injected with a potentiating dose of LPS (75 μg). Serum cytokine levels were determined as described in Materials and Methods. The results are expressed as percentages of the positive control (mice treated with PBS and challenged with SEB and a potentiating dose of LPS). The standard errors of the means for duplicate wells were <10% for calculated values. An asterisk indicates that the P value compared with the positive control (mice treated with PBS and challenged with SEB and a potentiating dose of LPS) was <0.001. Solid bars, IFN-γ; cross-hatched bars, TNF-α; open bars, IL-1α.