Genetic manipulation of BCG leads to altered presentation of CD4 and CD8 epitiopes from Antigen 85B by mouse dendritic cells. (78.22)

Abstract

Abstract The partial efficacy of BCG vaccine has led to a search for more effective vaccines. The immuno-dominant antigen-85B (Ag85B) from BCG vaccine is processed in macrophages and dendritic cells (DCs) dependent upon the phagosomal pH and lysosomal delivery. However, BCG avoids lysosomal localization and its phagosomes are near neutral. We found that induction of autophagy enhanced the lysosomal delivery of BCG vaccine in DCs. This in turn increased the MHC-II dependent presentation of Ag85B which was detected using an Ag85B-specific T cell hybridoma. DCs also showed an enhanced presentation of Ag85B when infected with BCG that was engineered to over-express Ag85B. We found that over expressed (OE)-Ag85B triggered autophagy. Furthermore, Ag85B is secreted from BCG vaccine into the cytosol of DCs although BCG is inefficient in inducing CD8 T cells against Ag85B in mice. Since OE-Ag85B enhanced the MHC-II dependent presentation, we examined whether OE-Ag85B could also be routed through the proteasomal pathway. DCs were infected with BCG-OEAg85B and Ag85B presentation monitored with or without the blockade of proteasomes through lactacystin. Lactacystin enhanced the MHC-II dependent presentation of Ag85B suggesting that OE-Ag85B goes through the proteasome as well as lysosome during autophagy. Mice were then immunized with BCG-OEAg85B and the spleens were found to contain an increased number of CD8 T cells specific for an epitope of Ag85B detected using a pentamer-conjugate. We propose therefore that genetic manipulation of BCG may be used to alter the levels of CD4 and CD8 epitope presentation by DCs and alter vaccine efficacy.