Long-lived cytotoxic T lymphocyte memory in mucosal tissues after mucosal but not systemic immunization

The induction and maintenance of long-term CTL memory at mucosal surfaces may be a critical component of protection against mucosal pathogens and is one goal towards development of effective mucosal vaccines. In these studies we have functionally evaluated short and long-term CTL memory in systemic and respiratory or genital-associated lymphoid tissues following mucosal or systemic routes of immunization. Our results indicate that shortly after immunizing mice with a recombinant adenovirus vector expressing glycoprotein B (gB) of herpes simplex virus (AdgB8), gB-specific CTL memory responses were observed in systemic and mucosal immune compartments regardless of the route of inoculation. In contrast, several months after immunization, anamnestic CTL responses compartmentalized exclusively to mucosal or systemic lymphoid tissues after mucosal or systemic immunization, respectively. Furthermore, the compartmentalized CTL memory responses in mucosal tissues were functionally observed for longer than 1.5 yr after intranasal immunization, and CTL precursor frequencies one year after immunization were comparable to those seen shortly after immunization. Therefore, to our knowledge, this is the first functional demonstration that the maintenance of anti-viral memory CTL in mucosal tissues is dependent on the route of immunization and the time of assessment. These results have important implications for our understanding of the development, maintenance, and compartmentalization of functional T cell memory and the development and evaluation of vaccines for mucosal pathogens, such as HSV and HIV.