Ultrasound molecular imaging of acute cardiac transplantation rejection using nanobubbles targeted to T lymphocytes

Clinical surveillance of acute heart transplantation rejection requires repeated invasive endomyocardial biopsies and noninvasive diagnostic techniques are desperately needed. It is acknowledged that T lymphocyte infiltration is the central process of acute rejection. We hypothesized that ultrasound molecular imaging with T lymphocyte-targeted nanobubbles could be used to detect acute rejection in heart transplantation. In this study, nanobubbles bearing anti-CD3 antibody (NBCD3) or isotype antibody (NBcon) were prepared and characterized. There was significant adhesion of NBCD3 to T lymphocytes compared with NBcon in vitro. The signal intensity of the adherent NBCD3 was significantly higher than that of the NBcon in allograft rats, but not significantly different in isograft rats. Furthermore, the signal intensity of NBCD3 in allograft rats was significantly higher than that in isograft rats, indicating more T lymphocyte infiltration in allograft rats compared with isograft rats. These results were further confirmed by immunohistochemistry examination, and the signal intensity of NBCD3 was positively correlated with the number of T lymphocytes in allograft rats. In summary, ultrasound molecular imaging with T lymphocyte-targeted nanobubbles can detect T lymphocyte infiltration in acute rejection and could be used as a noninvasive method in acute rejection detection after cardiac transplantation.