The Comparison of In Vitro and In Vivo Anti-Host Responses as a Predictor of T Cell Reactivity after Allogeneic-BMT as Determined by TCR Vb Spectratype Analysis.

Immunotherapeutic strategies have gained recognition as viable alternatives to more conventional therapeutic modalities for the treatment of cancer. In this regard, adoptive T cell therapy through allogeneic blood and marrow transplantation (BMT) has offered the first evidence to demonstrate that anti-tumor effects could be achieved against hematological malignancies. However, complications which include graft failure, opportunistic infections, leukemic relapse and graft-versus-host disease (GVHD) underscore the importance for the development of more targeted strategies in order to promote the successful implementation of allogeneic-BMT as a long term curative approach. It is well understood that mature donor T cells present in the donor inoculum must be an integral part of any such strategy as they play a pivotal role in all of the above mentioned complications. The incidence of the first three complications is diminished by the presence of mature donor T cells while, unfortunately, the transplantation of mature alloreactive donor T cells also directly induces the latter complication of acute GVHD, which can be directed against either HLA or minor histocompatibility antigen (miHA) disparities. Efforts to pan deplete donor marrow inoculum of T cells have been successful in minimizing the development of disease but have been associated with increased leukemic relapse. Thus, one approach to solve this problem would be to identify and then selectively deplete alloreactive donor T cells while allowing the residual T cells to provide protection against infection and to mediate a leukemia-specific GVL response. We hypothesized that an in vitro culture system using a one-way mixed lymphocyte reaction generated between a potential allogeneic BMT donor and their respective recipient could give rise to many of the alloreactive T cell responses that would be predictive of those that would be generated in vivo, following BMT. We proceeded to test the predictive value of the in vitro culture system through the use of TCR CDR3 Vβ spectratype analysis in the clinical BMT setting. To this end we compared, by spectratype analysis, the in vitro and post-transplant in vivo responses of nine donor patient pairs. The results indicated a high association of overlapping Vβ CDR3-size skewing as defined by the reactive Vβ families in the patient post-transplant also found to be reactive in the in vitro culture system (range of overlap 50–100%, median 72.5%). Thus, in vitro spectratyping analysis may be useful in guiding the manipulation of the donor T cell inoculum in order to provide improved BMT outcomes.