Prototype
foamy virus protease activity is essential
for intraparticle reverse transcription initiation but not absolutely required
for uncoating upon host cell entry.
However, subsequent studies carried out on small numbers (20 — 30) of CFS patients, failed to confirm evidence
for HTLV (type 1 or 11)[22]--[25] or other retroviruses, including the closely - related simian T lymphotropic
virus type l, the prototype
foamy virus, simian retrovirus, bovine and feline leukaemia
viruses [26] and HIV - 1 [23].