Cell-secreted Gp96-Ig-peptide complexes induce lamina propria and intraepithelial CD8+ cytotoxic T lymphocytes in the intestinal mucosa.

Induction of mucosal immunity is critical for protection from enteric pathogens. Heat shock protein gp96 is one of the primary peptide and protein chaperones located in the endoplasmic reticulum. We reported previously that a cell-secreted gp96-Ig fusion protein (gp96-Ig) mediated strong systemic, antigen-specific CD8-CTL expansion in vivo. We now evaluate the mucosal immune response to stimulation by secreted gp96 using allogeneic NIH-3T3 transfected with ovalbumin (OVA) and gp96-Ig. A single intraperitoneal NIH-3T3-OVA-gp96-Ig immunization caused significant homing of OVA-specific TCR transgenic CD8 cells (OT-I) to Peyer's patches, to the intraepithelial compartment and to the lamina propria. Intraperitoneal immunization with cells secreting gp96-Ig provided stronger mucosal immunity than the same dose instilled vaginally or rectally or injected subcutaneously or intradermally. Our results provide the first evidence that cell-based gp96-Ig-secreting vaccines may serve as a potent modality to induce mucosal immunity.