Mucosal Immunization with a Staphylococcus aureus IsdA-Cholera Toxin A2/B Chimera Induces Antigen-Specific Th2-Type Responses in Mice

Abstract

ABSTRACTStaphylococcus aureusis a leading cause of opportunistic infection worldwide and a significant public health threat. The iron-regulated surface determinant A (IsdA) adhesin is essential forS. aureuscolonization on human nasal epithelial cells and plays an important role in iron acquisition and resistance to human skin defenses. Here we investigated the murine immune response to intranasal administration of a cholera toxin A2/B (CTA2/B) chimera containing IsdA. Plasmids were constructed to express the IsdA-CTA2/B chimera and control proteins inEscherichia coli. Proper construction of the chimera was verified by SDS-PAGE, Western blotting, GM1 enzyme-linked immunosorbent assay (ELISA), and confocal microscopy. Groups of female BALB/c mice were mock immunized or immunized with IsdA-CTA2/B, IsdA mixed with CTA2/B, or IsdA alone, followed by one booster immunization at 10 days postpriming. Analysis of serum IgG and nasal, intestinal, and vaginal IgA suggested that mucosal immunization with IsdA-CTA2/B induces significant IsdA-specific humoral immunity. Functionalin vitroassays revealed that immune serum significantly blocks the adherence ofS. aureusto human epithelial cells. Splenocytes from mice immunized with IsdA-CTA2/B showed specific cellular proliferation and production of interleukin-4 (IL-4) afterin vitrostimulation. Immunization with IsdA-CTA2/B drove isotype switching to IgG1, indicative of a Th2-type response. Our results suggest that the immunogenicity of theS. aureusIsdA-CTA2/B chimera merits further investigation as a potential mucosal vaccine candidate.