SPAM-8,a mouse-human heteromyeloma fusion partner in the production of human monoclonal antibodies. Establishment of a human monoclonal antibody against cytomegalovirus

A heteromyeloma (mouse × human) cell line (SPAM-8) was produced by fusing mouse myeloma cells (SP2/0) with human peripheral blood lymphocytes. The cells were sensitive to aminopterin and resistant to ouabain. The cells showed a doubling time of about 19 hours and a cloning efficiency of 0.8 cells/well (to obtain growth in 50% of wells seeded) using mouse thymocytes as feeder cells. The number of chromosomes was about 86 and 1% of the total DNA was of human origin. Fusion of SPAM-8 cells with lymphocytes prepared from human spleens resulted in approximately one hybridoma per 10⁵ seeded lymphocytes. A trioma (human × [mouse × human]) cell line was established by fusing cells of an Epstein-Barr virus-transformed B cell line with SPAM-8 cells. The trioma cells produced antibodies (IgG1, κ) against cytomegalovirus, in a concentration of 7 μg/ml in spent medium, over a period of six months of continuous culture. The results obtained indicate that the heteromyeloma SPAM-8 may be used as a fusion partner in the production of human monoclonal antibodies.