612 Lymphodepletion blunts the antigen-spreading response post TAA-T cell therapy for pediatric solid tumors by Catherine M Bollard, Conrad Cruz, Fahmida Hoq, Haili Lang, Amy B Hont, Naomi Field, Samantha Murphy, Patrick J Hanley, Chase D McCann, Anushree Datar, Rachel DiCioccio, Holly J Meany