The Development of Monoclonal Antibodies Specific to the Soluble Form of CD155 in the Human Peripheral Blood

Abstract

CD155, also known as poliovirus receptor (PVR) or Necl-5, is an immunoreceptor with three immunoglobulin-like domains in the extracellular portion and is ubiquitously expressed on the cell surface of hematopoietic and nonhematopoietic cells. Human CD155 contains membrane-bound CD155 (mCD155) and soluble CD155 (sCD155) lacking the transmembrane region encoded by splicing variants of genes. The serum levels of sCD155 increased in patients with a variety of cancers. Furthermore, sCD155 suppresses tumor immunity through the blockade of DNAM-1 signaling. Therefore, sCD155 is potentially helpful for the diagnosis of cancer development and a novel therapeutic target in cancer treatment. However, monoclonal antibodies (mAbs) specific to sCD155, but not mCD155, have not yet been developed. Here, we generated 14 mAbs (named TX119 to TX122 and TX126 to TX135) that recognize the cytoplasmic region of CD155. These mAbs bind to sCD155, but not mCD155, when applied from the outside of the cell. Moreover, we established the assay system to quantify the sCD155 concentration in human serum. Thus, these mAbs can be utilized for the targeting and quantification of sCD155 in the human peripheral blood.