Immunization of Mice with a Live Transconjugant Shigella Hybrid Strain Induced Th1 and Th17 Cell‐Mediated Immune Responses and Confirmed Passive Protection Against Heterologous Shigellae

Abstract

An avirulent, live transconjugant Shigella hybrid (LTSHDstx) strain was constructed in our earlier study by introducing a plasmid vector, pPR1347, into a Shiga toxin gene deleted Shigella dysenteriae 1. Three successive oral administrations of LTSHDstx to female adult mice produced comprehensive passive heterologous protection in their offspring against challenge with wildtype shigellae. Production of NO and different cytokines such asIL-12p70, IL-1b and IL-23 in peritoneal mice macrophages indicated that LTSHDstx induced innate and adaptive immunity in mice. Furthermore, production of IFN-c, IL-10 and IL-17 in LTSH-primed splenic CD4+ T cell suggested that LTSHDstx may induce Th1 and Th17 cell-mediated immune responses. Exponential increase of the serum IgG and IgA titre against whole shigellae was observed in immunized adult mice during and after the immunization with the highest peak on day 35. Antigen-specific sIgA was also determined from intestinal lavage of immunized mice. The stomach extracts of neonates from immunized mice, mainly containing mother's milk, contained significant levels of anti-LTSHDstx immunoglobulin. These studies suggest that the LTSHDstx could be a new live oral vaccine candidate against shigellosis in the near future.

Vaccination With Mouse Dendritic Cells Loaded With an IpaD-IpaB Fusion Provides Protection Against Shigellosis

“…CD4+ memory T cells were isolated from spleens of BALB/c mice previously immunized intranasally with DBF+dmLT (day 56 after first immunization) as previously described (14, 26, 28). A single cell suspension was stained with a PE anti-mouse CD4 antibody as described above.…”

“…Immunization can also mimic these primary responses present during infection. For example, it has previously been shown that an attenuated Shigella dysenteriae strain used as a vaccine elicited Th1/Th17 responses (14). Macrophages from immunized animals secrete significantly higher amounts of IL-6, IL-23, IL-12p70, and IL-1β, which in the context of antigen-presenting cells would create a polarization environment of CD4+ cells toward the Th1/Th17 lineages.…”

“…Indeed, CD4+ cells isolated from spleens of immunized animals secrete higher levels of the canonical Th1 cytokine IFN-γ and Th17 cytokine IL-17A relative to controls. Modulatory cytokine IL-10 was also elevated, whereas Th2 cytokine IL-4 had no significant change between groups (14).…”