A mixed-immunoglobulin rosette technique for detection of antibody to feline oncornavirus-associated cell membrane antigen.

A mixed-immunoglobulin rosette technique has been developed for the detection of antibodies to feline oncornavirus-associated cell membrane antigens. Lymphoblastoid cells infected with feline leukemia virus were incubated with test sera and then fixed in paraformaldehyde. They were then exposed to a rabbit anti-cat immunoglobulin G serum. Antigen-antibody reactions were detected by mixing the cells with sheep erythrocytes sensitized with cat anti-sheep red blood cell serum; the presence of cat antibody on the lymphoid cells was registered by the formation of sheep red blood cell rosettes around them. The method was shown to be at least 10 times more sensitive than indirect immunofluorescence. A high degree of correlation was shown between the mixed-immunoglobulin rosette and indirect immunofluorescence tests, using both feline leukemia virus-infected cat and dog cells as targets. The results indicate that the tests are likely to be measuring similar reactions. Using the indirect immunofluorescence test we found that 75% of cats with lymphoid neoplasia had no demonstrable antibodies. Twenty-four of such indirect immunofluorescence-negative sera were tested by the mixed-immunoglobulin rosette technique; antibody was shown in at least seven of these sera.