Minor antigen solves major problem

DNA Fusion Vaccines Induce Targeted Epitope-Specific CTLs against Minor Histocompatibility Antigens from a Normal or Tolerized Repertoire

We have designed DNA fusion vaccines able to induce high levels of epitope-specific CD8(+) T cells, using linked CD4(+) T cell help. Such vaccines can activate effective immunity against tumor Ags. To model performance against minor histocompatibility (H) Ags important in allogeneic hemopoietic stem cell transplantation, responses against the H2D(b)-restricted Uty and Smcy male HY epitopes have been investigated. Vaccination of females induced high levels of tetramer-specific, IFN-gamma-producing CD8(+) T cells against each epitope. Vaccines incorporating a single epitope primed effector CTL able to kill male splenocytes in vitro and in vivo, and HY(Db)Uty-specific vaccination accelerated rejection of syngeneic male skin grafts. Priming against either epitope established long-term memory, expandable by injection of male cells. Expanded CD8(+) T cells remained specific for the priming HY epitope, with responses to the second suppressed. To investigate vaccine performance in a tolerized repertoire, male mice were vaccinated with the fusion constructs. Strikingly, this also generated epitope-specific IFN-gamma-producing CD8(+) T cells with cytotoxic function. However, numbers and avidity were lower than in vaccinated females, and vaccinated males failed to reject CFSE-labeled male splenocytes in vivo. Nevertheless, these findings indicate that DNA fusion vaccines can mobilize CD8(+) T cells against endogenous minor H Ags, even from a profoundly tolerized repertoire. In the transplantation setting, vaccination of donors could prime and expand specific T cells for in vivo transfer. For patients, vaccination could activate a potentially less tolerized repertoire against similar Ags that may be overexpressed by tumor cells, for focused immune attack.

Peyer's patch is the essential site in initiating murine acute and lethal graft-versus-host reaction

Acute graft-versus-host disease (a-GVHD) is initiated primarily by immunologically competent cytotoxic T cells (CTLs) that express anti-host specificities. However, the host lymphoid compartment in which these precursor CTLs are initially stimulated remains unclear. Here we show that gut Peyer's patches (PPs) are required to activate anti-host CTL responses in a well characterized murine acute graft-versus-host reaction (a-GVHR) model, involving transfer of parent lymphocytes into F1 hybrid recipients. The a-GVHR was prevented when recruitment of donor T cells into PP was interrupted either by disrupting the gene encoding chemokine receptor CCR5 or by blocking integrin alpha(4)beta(7)-MAdCAM-1 (mucosal vascular addressin) interactions. Mice deficient for PPs failed to develop a-GVHD in two models of disease induction. Thus, blockade of CTL generation in PPs might offer new strategies for circumventing a-GVHD.