The focus of this proposal is to develop a safe, effective subunit vaccine delivery system. To accomplish this, we will utilize our bacterial commensal vector (BCV) technology. BCV uses the Gram-positive commensal bacteria, Streptococcus gordonii, to express heterologous antigens of interest on its external surface. Phase I human clinical trials indicate that this S. gordonii strain is safe and well-tolerated in humans. Mucosal immunization of mice with S. gordonii expressing vaccinia virus (VV) proteins induced significantly increased vaccinia virus specific antibodies in saliva and serum compared to control animals. Furthermore, serum obtained from immunized mice contained neutralizing antibodies against vaccinia virus. However, immunization of mice with the BCV:VV constructs elicited only partial protection against lethal vaccinia challenge. We hypothesize that co-expression of immunomodulatory molecules by the BCV system will enhance humoral or cellular responses to the encoded antigens, thus providing a safe, effective, and inexpensive subunit vaccine delivery system suitable for use against many viral or bacterial pathogens. To further develop the BCV system the following specific aims are proposed: 1) To enhance the immunogenicity of S. gordonii recombinants by co-expressing cytokines with a model antigen. 2) To evaluate humoral and cellular immune responses to the model antigen after intranasal vaccination of mice with the S. gordonii double recombinants.
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