None, that I am aware of, sorry 
Most of what i have seen coming out of the US is still unity based. All of our UE4 stuff is being done in house at the moment, but we’re an architecture firm, and not a viz studio.
UE4 is still pretty new, but I am sure some of the bigger rendering houses in the US are working on it. Maybe contact one of the larger companies and see if they will be wiling to work on something with you for a reduced fee, etc.