CMV Specific Cellular Immunity in Recipients of Allogeneic Bone Marrow Transplantation: Association of CMV-Specific HLA-Peptide Tetramer Binding With Cytotoxic T-Cell Function, CMV Infection and Other Clinical Events

OBJECTIVES:

• To document the quantitative characteristics of a cytomegalovirus (CMV)-specific HLA-peptide tetramer-binding assay (TBA) for cytotoxic T lymphocytes (CTLs) in patients who have undergone allogeneic bone marrow transplantation (BMT) or peripheral blood stem cell transplantation (PBSCT).
• To confirm the optimal TBA conditions for CTL characterization in these patients.
• To compare the TBA results for these patients with conventional assays for CTL functions.
• To compare CMV-specific TBA during the first 3 months after allogeneic BMT or PBSCT and to determine whether this binding function, in either donor or recipient, is a surrogate marker for protection from risk of CMV infection in these patients.
• To determine whether acquisition of CMV-specific TBA protects from risk for CMV disease in patients having active CMV infection after allogeneic BMT or PBSCT.

OUTLINE: This is a multicenter study. Patients accrue initially to cohort 1 until a sufficient number of stem cell transplantation (SCT) recipients are enrolled. Patients then accrue to cohort 2 based on documented cytomegalovirus (CMV) infection and preemptive treatment with ganciclovir within 90 days after SCT (patients previously accrued to cohort 1 can be accrued to cohort 2 if they develop CMV infection).

• Cohort 1: Patients undergo blood sample collection on approximately days 40, 90, 120, 150, 180, and 360 post transplantation. Samples are analyzed (to determine the development of CMV immunity) for prevalence of CMV-specific cytotoxic T-lymphocytes (CTL) by HLA-peptide tetramer-binding assay (TBA) pp65, with and without in vitro stimulation (IVS). Samples collected on days 40 and 90 are also analyzed by chromium release assay (CRA). Patients suspected of developing CMV viremia may receive ganciclovir according to standard clinical practice.
• Cohort 2: Patients undergo blood sample collection on approximately days 90, 120, 150, 180, and 360 after SCT. Samples are analyzed by TBApp65 staining and for prospective measurement of CMV-specific CTL functions.

All patients undergo routine clinical surveillance for CMV infection on days 21 to 100 after SCT. CMV viral load measurements are obtained twice weekly by CMV-DNA PCR assays on blood cells and plasma and shell-vial blood cultures. In cohort 2, CMV viral load is also determined on days 90 (if not previously as part of cohort 1), 120, 150, 180, and 360. The CMV infection data obtained is then compared with TBA and CTL measurements using HLA-specific tetramers and IVS-induced cytotoxicity assays. Clinical events, such as graft-versus-host disease, underlying disease status, and procedure-related complications are also analyzed and correlated with TBA results.