Abstract 4191: Delayed onset of GvHD in PBMC humanized NCG-B2m KO mice provides an enhanced model for oncology studies

Abstract Humanized mice are specialized animal models incorporating components of the human immune system. These models are valuable tools for assessing the efficacy of human immunotherapies on tumors. Humanized mice are created by injecting human CD34+ hematopoietic stem cells (HSCs) or human peripheral blood mononuclear cells (PBMCs) into an immunodeficient mouse. PBMC humanized (HuPBMC) mice engraft within a few weeks and can recapitulate a robust human T cell population. One challenge when using HuPBMC mice is the onset of graft versus host disease (GvHD), limiting their lifespan compared to hCD34+ HSC humanized mice. The onset of GvHD varies in the HuPBMC model depending on the donor cells. The development of xenogeneic GvHD is dependent on the expression of major histocompatibility complex (MHC) on host cells and lowering MHC expression can delay the onset of GvHD. NCG-B2m KO mice lack beta-2 microglobulin, a component of MHC I, and have lower cell surface expression of MHC I molecules. This leads to a decrease in recognition of host cells by human immune cells. Here we compared the onset of GvHD between HuPBMC NCG-B2m KO mice and HuPBMC NCG mice. PBMC donor variability was also compared between the two PBMC humanized models by evaluating multiple donors and assessing additional collections from the same donor. After the PBMC engraftment was characterized, HuPBMC NCG mice and HuPBMC NCG-B2m KO mice were enrolled in tumor studies comparing outcomes and tumor growth kinetics in mice treated with human immune checkpoint blockade therapy. NCG and NCG-B2m KO mice were injected with 1x107 PBMCs from individual donors. Animals were weighed three times a week to monitor for changes in body weight and general health status. Peripheral blood was collected at day 10, 20, 30, 40, 60 and 90 post injection for flow cytometry screening of human immune cell engraftment (hCD45+, hCD3+, hCD4+ and hCD8+). Human PBMCs isolated from additional collections from the same donors were also injected into both NCG-B2m KO mice and NCG mice and flow cytometry was performed. HuPBMC NCG-B2m KO mice survived longer than HuPBMC NCG mice allowing for the potential use in longer term tumor studies before the results are confounded by GvHD. PBMC humanized mice are an important model for translational research using immunotherapies and the PBMC humanized NCG-B2m KO model provides an expanded study window ideal for oncology studies. Citation Format: Steven Bronson, David Harris, Anya Avrutskaya, Christoph Eberle, Jenny Rowe. Delayed onset of GvHD in PBMC humanized NCG-B2m KO mice provides an enhanced model for oncology studies abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4191.