Immunotherapy with Anti-CD3 x Anti-CMV bispecific antibody (CMVBi) armed donor derived activated T cells (ATC) - a novel strategy against cytomegalovirus (CMV) post allogeneic stem cell transplantation (SCT)

We hypothesize that CMVBi-armed ATC will exhibit specific cytotoxicity to eliminate CMV infected targets in vitro and will be safe and effective when given after allogeneic SCT in the treatment of patients infected with CMV. Adoptive immunotherapy with anti-CD3 x anti-CMV bispecific antibody-armed ATC is a novel strategy against CMV post alloSCT. This non-MHC restricted specific killing strategy could be easily adapted for the prevention and/or treatment of CMV infection/disease after alloSCT using donor-derived ATC.
Clinical and scientific problem: None of the current strategies are completely effective in preventing or treating CMV infections after transplantation. Post-alloSCT infusions of donor CMV-specific cytotoxic T lymphocytes (CTL) clones are encouraging, but are dose-limiting, time-restricted, expensive, and labor intensive.
Normal donor peripheral blood mononuclear cells (PBMC) were used to generate ATC by activation with anti-CD3 (OKT3) and interleukin 2 (IL-2). CMVBi was created by chemical heteroconjugation of OKT3 (murine IgG2a) monoclonal antibody and polyclonal anti-CMV (Cytogam^®). Specific cytotoxicity was tested by ⁵¹Cr release assay using CMV-infected or uninfected human fibroblasts as target cells. Effector populations tested included CMVBi armed ATC and ATC alone; additional controls included CMVBi alone, Cytogam^® alone, CMVBi armed, and unarmed PBMC. Cytotoxicity was assessed for CMVBi and an irrelevant BiAb at arming doses ranging from 1 to 500 ng/10⁶ ATC with effector to target ratios (E:T) ranging from 25:1 to 3.125:1. Interferon gamma (IFNγ) EliSpots were used to determine cytokine response after exposing CMV-infected and uninfected fibroblasts to unarmed and CMVBi-armed ATC.

Our data strongly support the hypothesis that CMVBi-armed ATC will specifically target and eliminate CMV infected cells with the following results:
We believe that our study will be the stepping stone for novel immunotherapeutic strategies in the field of infectious diseases.

This study was funded by: 1) R01 CA 092344 from the NIH, 2) Susan G. Komen Foundation Grant #BCTR0707125, 3) Leukemia and Lymphoma Society TRF grants #6066-05 and TRF #6092-09 and 4) Karmanos Cancer Institute.