NEW YORK--(BUSINESS WIRE)--Kroll Bond Rating Agency (KBRA) assigns preliminary ratings to 42 classes of mortgage pass-through certificates from J.P. Morgan Mortgage Trust 2015-4 (JPMMT 2015-4), a prime jumbo RMBS transaction. The underlying collateral for JPMMT 2015-4 consists of 534 first-lien, residential mortgage loans with an aggregate principal balance of $388,339,827 as of the cut-off date. The aggregate mortgage pool comprises two smaller loan groups and consists entirely of fully-amorti