e14543 Background: Pulsed electric field (PEF) tissue destruction has demonstrated meaningful systemic immune responses in mice that are superior to thermal ablation, and synergize effectively with systemic chemotherapy and checkpoint blockade (CPB) immunotherapy. Immune cell populations are increased by PEF, including tumor specific activated CD8 T-cells and plasma B-cells. Antitumor immunity can include the presence of circulating anti-cancer antibodies. However, the presence and role of circulating tumor specific antibodies induced by PEF have not been explored. Serological antibodies are often detected with the ELISA assay, where tumor-associated antigens are coated to a microtiter plate to attract the corresponding serum antibodies. Here, we quantify IgG tumor specific antibodies after PEF using an in-house ELISA. Methods: Mice bearing immune-warm (EMT6) and immune-cold (4T1) orthotopic murine breast tumors were treated with a biphasic PEF dose comparable to Aliya titrated for mouse tumors. To detect tumor specific circulating IgG1 immunoglobulin in serum, an ELISA plate was coated with EMT6 and 4T1 protein lysate, as well as with a known 4T1-expressed tumor-specific antigen (gp70). Serum draws from the treated, untreated, and naïve mice were exposed to the coated wells for 1 hour. Bound IgG were detected by anti-mouse IgG (HRP tagged) antibody added to the wells and incubated 1 hour. A TMB substrate was added and color development was allowed for 15 minutes. The optical density was quantified using a microtiter plate reader. Results: ELISA quantification of serum IgG at multiple timepoints show that 4T1 tumor-specific IgG antibodies were increased 14.3- and 2.6-fold by day 20 in the PEF-treated and untreated group survivors relative to Naïve mice, respectively, (OD=0.86 and 0.15 v. 0.06). Furthermore, IgG antibodies specific to the gp70 antigen of the 4T1 cell line were increased by 44.9- and 2.7-fold in the PEF-treated and untreated groups relative to naïve mice (OD=3.14 and 0.19 v. 0.07). In the EMT6 model, at 3 months post-treatment, only the PEF-ablated group mice survived, and showed 15.5-fold higher antibodies against EMT6 tumor antigens compared to naive mice (OD=0.62 v. 0.04). Conclusions: The specific form of PEF in this study generated tumor-specific IgG long-lived antibodies in mice for immune-warm and immune-cold tumor models, corroborating previous findings of increased murine B-cell and plasma cell populations. This effect has not been well-reported for other ablation technologies. Increases were evident by Day 20 post-PEF and persisted at least 3 months. These murine data suggest the PEF used may invoke potent, long-lived immune responses and anti-tumor immune surveillance, offering a potential approach for in situ tumor vaccination to improve metastatic disease outcomes. Future studies should determine response durability and its role in attaining distant tumor clearance.