Breast cancer remains one of the most prevalent malignancies affecting women worldwide and continues to pose significant clinical challenges due to high rates of recurrence and limited therapeutic options for advanced disease, particularly in triple-negative breast cancer (TNBC). Emerging evidence suggests that infectious agents may contribute to breast cancer pathogenesis, with human cytomegalovirus (CMV), a ubiquitous double-stranded DNA virus infecting more than 90% of the global population, being increasingly implicated. CMV-positive cells have been detected in breast tumours and are frequently associated with malignant epithelial cells, where they are thought to modulate the tumour microenvironment by promoting immune evasion, angiogenesis, and metastatic progression. Consistent with these observations, immunohistochemical analysis of a 100-core breast cancer tissue microarray revealed the presence of CMV-positive cells across multiple tumour samples, supporting a potential role for CMV in breast cancer biology. Chimeric antigen receptor (CAR) T-cell therapy is a rapidly evolving form of personalized immunotherapy that involves the isolation of patient-derived T cells, their genetic modification to express tumour-targeting receptors, and subsequent reinfusion to mediate antigen-specific cytotoxicity. While CAR T-cell therapies have demonstrated remarkable success in haematological malignancies, their application in solid tumours such as breast cancer remains limited by tumour heterogeneity and an immunosuppressive microenvironment. My PhD project is aiming to develop and optimize CAR T-cell therapies targeting CMV-derived antigens, exploiting viral antigen expression within tumours, alongside established breast cancer-associated targets such as TROP2. By integrating viral and tumour-specific targeting strategies, this work seeks to establish a robust, multifaceted CAR T-cell immunotherapy platform with the potential to improve therapeutic outcomes for patients with breast cancer.