NEW YORK--(BUSINESS WIRE)--Kroll Bond Rating Agency (KBRA) assigns preliminary ratings to 11 classes of notes from Freddie Mac Structured Agency Credit Risk (STACR) 2015-DNA2, a risk transfer securitization comprising a $32.0 billion reference pool with 141,967 mortgages. STACR 2015-DNA2 is the second credit risk transfer transaction featuring actual loss exposure issued by Freddie Mac this year. This is the fourth STACR transaction to be rated by KBRA. The reference pool has a weighted average