[Histonet] Immunostaining for West Nile virus in old paraffin blocks

[Douglas Gregg]

I have developed two avidin-biotin alkaline phosphatase stains for
West Nile virus in tissues that are formalin fixed and paraffin
embedded. One uses a polyclonal and the other a monoclonal (7H2)
antibody. Both work fine in positive control chicken embryo heart
tissue. I have had difficulty in finding antigen in West Nile infected
brain tissues collected one year ago even though there is severe
encephalitis present.  It is possible that the tissue was collected
too late in disease. It was 10-14 days post exposure. However, I am
concerned that the negative results may be  due to the age of the
tissues in paraffin rather than having been collected too late in the
disease.  I have a good retrieval method and the tests are very
reliable on acute cases that are formalin fixed for up to one month
and paraffin embedded.

Has anyone done any retrospective studies on paraffin blocks of West
Nile virus infected  tissues as old as a year or more.If so, did they
stain? Also, I would very much like to find a paraffin block that is
one year old for a control. A crow heart would be a good choice. I am
sure there must be labs out there that have done testing of crows or
other animals found dead and submitted for testing. I would like to
try my staining on one that was collected a year ago. If it stains,
then it is not likely due to the age of the tissues in paraffin.

Help would be most appreciated if anyone can spare an old paraffin
block of a known case.

Douglas Gregg DVM PhD
Veterinary Pathologist
Southold, NY