Characterization of a CD52 Knockout Mouse to Investigate the Function of CD52 (P5.323)

OBJECTIVE: To investigate the function of CD52 in vivo.BACKGROUND: Alemtuzumab, approved for the treatment of relapsing-remitting MS in over 45 countries, is a humanized monoclonal antibody that binds to the CD52 antigen present at high levels on T and B lymphocytes, and at lower levels on natural killer cells, monocytes, and macrophages. There is little or no CD52 on neutrophils, plasma cells, platelets, or bone marrow stem cells. Although the function of CD52 is unknown, it has been proposed to play a potential role in several processes including participation in cell-cell interactions, regulatory T-cell function, and regulating activated T cells.DESIGN/METHODS: To investigate the function of CD52, a homozygous CD52 knockout mouse has been developed on the C57BL/6 background in which both coding exons of the CD52 gene were deleted. Flow cytometric analysis was used to confirm the absence of CD52 expression on cells and to evaluate homeostatic lymphocyte populations over time. Evaluation of immune function was also investigated by quantifying resting immunoglobulin (Ig) levels and immune responses following immunization with a neoantigen.RESULTS: Flow cytometric evaluation revealed that CD52 expression was undetectable on lymphocytic subsets. In support of this, treatment with a murine CD52-specific depleting antibody had no significant effect on lymphocyte populations. Furthermore, no differences were observed in resting T- and B-cell numbers or in the resting levels of total Ig isotypes. Immunization with a neoantigen also demonstrated no significant differences in specific Ig production.CONCLUSIONS: We have created a novel mouse to better understand the function of CD52 and the mechanism of action of alemtuzumab.STUDY SUPPORTED BY: Genzyme, a Sanofi company. Disclosure: Dr. Turner has received personal compensation for activities with Genzyme Corporation as an employee. Dr. Havari has received personal compensation for activities with Genzyme as an employee. Dr. Chretien has received personal compensation for activities with Genzyme as an employee. Dr. LaMorte has received personal compensation for activities with Genzyme as an employee. Dr. Garron has received personal compensation for activities with Genzyme as an employee. Dr. Pande has received personal compensation for activities with Genzyme. Dr. Roberts has received personal compensation for activities with Genzyme. Dr. Siders has received personal compensation for activities with Genzyme Corporation as an employee.