Extracting signature snippets from AV databases

I'd like to create a set of test files containing (harmless) virus (and
spyware) signatures.  Can I extract the signatures from AV databases
(every PC has one)?   I'm thinking open source AV database may be easier
to extract signatures from than a commercial AV database.  If I can
automate the extraction and file creation, files won't become stale
because of lag time due to fluxuating interest of the maintainer (me).

Has this been done already?  Are specific signatures a 'secret sauce'?

The primary purpose is to create a test that safely verifies that our
browser protection product absolutely protects a computer from
intentional infection.

Thanks,
Bill Stout
www.greenborder.com