Heike,
  If you have access to a virology laboratory, you may be able to request 
them to grow up an infected cell line, which you can then make into a 
cell block.  I have done this in the past with great success.  We usually 
worked out some sort of trade of supplies for services.  Cell lines may 
not be exactly the same as "naturally" infected human tissue, but they 
will sure work great in a pinch.
  Good Luck,

Phyllis Davie
PhenoPath Laboratories
Seattle, WA
pdavie@phenopath.com