Generation and Characterization of the Cellular Immune Response to a Clostridium perfringens anti-SIV Mucosal Vaccine

by Helmus, Ruth Anne

Most new human immunodeficiency virus (HIV) infections are acquired through vaginal or rectal mucosa, and gut mucosal tissue is a primary target of HIV infection. To generate mucosal immunity against HIV or its simian counterpart simian immunodeficiency virus (SIV), the Gram positive bacterium Clostridium perfringens was used to develop a vaccine that delivers SIV p27 to the gut and induces local T cell immunity. Under in vitro conditions, Clostridium perfringens expressing SIV p27 (Cp-p27) was found to induce dendrite cell (DC) maturation and stimulate p27-specific T cell responses. To improve intracellular delivery of p27 to DCs and thereby enhance immune priming, Cp-p27 variants expressing p27 conjugated with protein transduction domains (PTDs) at the 5 end were constructed. While internalization of p27 by DCs and gut epithelial cells was improved following exposure to the PTD-Cp-p27 variants, cellular p27-specific immune stimulation was not significantly improved compared with wild-type Cp-p27. The Cp-p27 vaccine was then tested in vivo in mice for its ability to prime gut mucosal T cell responses. First, an adjuvant optimization study with three mucosal adjuvants, cholera toxin (CT), mutant E. coli heat-labile enterotoxin (LT(R192G)), and unmethylated cytosine-phosphate-guanine oligodinucleotides (CpG ODNs) was performed to determine the best T cell immune response in the gut. While the combination of CpG ODNs and (LT(R192G)) induced the highest T cell immune response, (LT(R192G)) alone provided the best multifunctional CD8+ T cell response in the gut. Oral Cp-p27 vaccination was then tested for induction of T cell immunity in vivo in a prime-boost model by combining Cp-p27 with systemic immunization with an adenovirus expressing p27 (Ad-p27). Cp-p27 vaccination primed a strong multifunctional T cell immune response in gut lamina propria, although it could not stimulate a systemic immune response. In contrast, Ad-p27 vaccination stimulated strong systemic immunity but limited gut mucosal immunity. By sequentially delivering Cp-p27 and Ad-p27, immunity in both the gut and systemic tissues was achieved. Altogether, this study demonstrates that Cp-p27 can deliver p27 to gut T cells through dendritic cells to prime a strong, multifunctional immune response in the gut effector tissue.