A multiplex immunostaining method for characterization of immune cells in non-human primate ocular tissue sections with intraocular inflammation.

The administration of biologics to the eyes of non-human primates in non-clinical studies can result in sporadic intraocular inflammation (IOI) in individual animals. When the biologic is a human (foreign) protein being administered to a non‑human primate (NHP), understanding the causes and clinical relevance of IOI can be especially challenging and represent an important data gap needed to advance the development of ocular biologic therapies. This study describes the development and validation of a multiplex immunostaining assay designed to address this need. It includes six markers that differentiate T cells (CD4+, CD8+), T regulatory cells (CD4+, FoxP3+), B cells (CD20+), macrophages (CD68+), and M2 macrophages and microglia cells (CD68+, IBA1+). Preliminary results in representative ocular samples with a biologic drug-induced IOI demonstrated the assay's ability to identify which immune cell types are present and their spatial relationships, which can significantly enhance the understanding of the immunology underlying IOI. This adds valuable interpretive information, facilitating better decision-making to develop safe and effective therapies.