The use of trypan blue for counterstaining in the Sepharose bead immunofluorescence test. The application of the test for the demonstration of primate retrovirus-specific antibodies and antigens.

The Sepharose bead immunoflurorescence test was performed by counterstaining the beads with trypan blue. This results in a red staining of negative beads which allows an easy distinction from positive green-fluorescent beads. Sepharose beads conjugated with viral proteins or antiviral antibodies were used to demonstrate Mason-Pfizer monkey virus (MPMW)- and simian sarcoma virus (SSV) - specific antigens or antibodies. The test shows a high sensitivity and specificity and needs a small amount of material.