No hes under a genjutsu By suishi's MS to Protect Kohona by all means
EDITED: but i do think Kabuto can Unsummon him still.......... not too sure tho!
Agree with these two!But Itachi destroyed shisui eye?. And it's not that easy cause why would kabuto unsummon Itachi cause there must be a prob that if he do that he unsummons all