Since 1988 we have been using a rabbit polyclonal antibody to SV40 (one of the three species of polyomaviruses) from LEE Biomolecular Research Labs, Inc. (San Diego, CA) to identify JC and BK viruses in formalin-fixed, paraffin-embedded human tissues.  Their telephone number is (619) 452-7700.  We use the antibody at a dilution of 1:5,000 for a 30' incubation (1:100,000 for overnight) with no pretreatment.  HIER may enhance immunoreactivity if the tissue is over-fixed.  I hope the antibody is still available!

RWC