PURPOSE: To obtain an excellent therapeutic agent for diseases caused by retroviruses useful for intractable diseases caused by infection with HTLV-I, HTLV-II, HIV-1, HIV-2, etc., which are human retroviruses.

CONSTITUTION: The characteristic of this therapeutic agent caused by retroviruses comprises a water-soluble or readily dispersible protein and glycoprotein separated from a cell membrane of a live cell in mammalian viscera, especially the water-soluble or readily dispersible protein and glycoprotein undergoing the denaturing action of the protein due to the immobilizing treatment with an aldehydic compound in separation as an active ingredient.