Cytomegalovirus (CMV) infections remain a serious problem in hematopoietic stem cell transplant patients. Following transplantation CMV infections can cause pneumonititis, hepatitis, enteritis, and marrow failure. CMV seropositive transplant recipients can be treated with antiviral agents such as ganciclovir at the onset of infection or at the time of stem cell engraftment, but ganciclovir therapy is associated with renal toxicity and suppression of neutrophil counts. Preliminary studies have found that adoptive immune therapy using CMV-reactive cytotoxic T lymphocytes (CTL) is an effective and less toxic alternative to prevention of CMV infection in transplant recipeints. The purpose of this study is to develop new treatment strategies for producing CMV-reactive CTLs that can be used for adoptive immunotherapy and to better understand the cellular immune response to CMV. Current studies are focused on identifying the immune dominant peptides that can be used to stimulate CMV reactive CTLs. CMV contains over 200 proteins, but two proteins CMV proteins pp65 and IE1, have been found to be immune dominant. We found that the peptide CMV pp65 91-100 was found an immune dominant peptide restricted to HLA-A33 and pp65 328-337 was an immune dominant peptide restricted to HLA-A2402. We are now using libraries of pp65 and IE1 overlapping peptides of 15 amino acids in length to identify new class I and class II epitopes. Class I and class II epitopes have been found among both the pp65 and IE1 peptides. To further characterize the class I eptitopes, the 9 amino acid peptides that made up the reactive 15 amino acid peptides were tested for reactivity toward CD8 cells. Several pp65 and IE1 reactive peptides 9 amino acids in length have been identified as well as their HLA restrictions.[unreadable] [unreadable] Preliminary studies have found that gene expression profiling is a useful tool for analyzing the potency of peripheral blood monocytes and immature dendritic cells. Studies are underway to determine if the addition of micro RNA expression profiling to gene expression profiling will improve the assessment of potency of immature dendritic cells and mature dendritic cells. In addition, since dentritic cells are sometimes produced from hematopoietic stem cells rather than peripheral blood monocytes, studies are underway to investigate the use of gene expression profiling and micro RNA expression profiling of hematopoietic stem cells from different sources.