Complement-fixation-inhibition as a test for antibodies in cats and humans to C-type RNA tumor virus antigen

The complement-fixation-inhibition (CFI) test was evaluated as a means of detecting humoral antibodies in cat sera and in human sera to mammalian C-type RNA virus interspecies antigen(s). CFI antibody titers of greater than or equal 1:2 were detected in sera from all tumor bearing (23) and normal cats (23), however, sera from most germ free cats were negative. When the same cat sera were tested for blocking antibody by the paired radioiodine labeled antibody technique the correlation between the radioimmune assay and CFI tests was 85%. Sera from 378 cancer patients and 193 normal people were tested for antibodies to the mammalian oncornavirus interspecies-specific antigen in the CFI test. This test used a rabbit antiserum prepared toward a purified feline leukemia virus (FeLV) interspecies antigen. Disrupted Rauscher murine leukemia virus (RLV) was used as source of interspecies antigen in the CFI test. A significantly (P=0.01) higher number of reactions occurred with sera from patients with lymphosarcoma (70.4%), osteosarcoma (41.0%), reticulum cell sarcoma (56.7%), and rhabdomyosarcoma (31.8%) as opposed to sera from normal individuals (6.2%). Of 51 sera from patients with acute lymphocytic leukemia 23.5% (P=0.05) were reactive. Of the sera from 88 breast cancer patients 22.7% reacted, as opposed to 7.8% of 116 normal females and 13.9% of 43 patients with benign breast disease. CFI antibody titers were shown to be dependent on RLV antigen concentration. Absorption with human A and B red blood cell (RBC) and Forssman antigen did not reduce the CFI titers in human sera whereas absorption with RLV reduced them significantly. By indirect radioimmunoelectrophoresis the antibody in selected human sera was shown to be an IgG.