A Chlamydia trachomatis Strain Expressing Ovalbumin Stimulates an Antigen-Specific CD4T Cell Response in Mice.

Abstract

Antigen-specific CD4T cells againstare crucial for driving bacterial clearance and mediating protection against reinfection. Although theprotein Cta1 has been identified to be a dominant murine CD4T cell antigen, its level of expression during the bacterial developmental cycle and precise localization within the host cell are unknown. Newly developed tools forgenetic manipulation have allowed us to generate astrain expressing a heterologous CD4T cell epitope from ovalbumin (OVA) consisting of OVA residues 323 to 339 (OVA). By tagging proteins expressed inwith OVA, we can begin to understand how protein expression, developmental regulation, and subcellular compartmentalization affect the potential of those proteins to serve as antigens. When OVAwas expressed as a fusion with green fluorescent protein, we found that we were able to elicit an OT-II T cell response in an antigen-dependent manner, but surprisingly, these T cells were unable to reduce bacterial burden in mice. These data suggest that the subcellular localization of antigen, the level of antigen expression, or the timing of expression within the developmental cycle ofmay play a crucial role in eliciting a protective CD4T cell response.