Human immune response to active immunization with rauscher leukemia virus. II. humoral immunity

Of 20 patients immunized with 100 μg formalin-killed Rauscher leukemia virus (RLV) every 2 weeks for 8 weeks, 10 developed a significant antibody titer as measured by a radioimmunoprecipitation assay. Among the responders, the mean titer, taken as the reciprocal of the highest serial twofold dilution yielding 50% virus precipitation, was ≈1:354. Antibody first appeared 2 weeks after immunization and reached a peak at 8 weeks. Antibody responses were most vigorous in patients with melanoma and in those receiving BCG plus chemotherapy; responses were least vigorous in patients with other solid tumors or acute leukemia, and in those receiving chemotherapy without immunotherapy. Correlation was excellent between the antibody response and the development of delayed hypersensitivity to the virus (P=0.005) and between the antibody response and in vitro lymphocyte blastogenic response to an antigen solubilized from RLV-infected cells (P=0.025). Extensive absorption studies indicated that sera from both immunized and nonimmunized subjects contained antimouse antibody. After in vivo absorption in mice, patients’ postimmunization sera retained antiviral activity.