Expression of Immune Checkpoints LAG-3, CTLA-4, TIM-3 and PD-1 in Beta Thalassemia patients Treated using HbF Augmentation Therapy and Regular Transfusions

Introduction: Beta-thalassemia is an inherited hemoglobin disorder caused by mutations in HBB gene encoding beta globin chains. Severe anemia secondary to defective globin chains, chronic hemolysis and ineffective erythropoiesis requires transfusion support from early childhood. Recently used treatment options with promising results in resource limited countries includes drugs which augment HbF such as hydroxyurea and thalidomide. Although effective in alleviating anemia and related symptoms, these drugs particularly thalidomide has been known for its immunomodulatory role. Similarly, repeated transfusions with compromised immune system increases the risk of infections and weakened immunity. One of the key regulators of immune systems includes immune checkpoints, cell surface molecules on immune cells. Limited studies are available on immune checkpoints such as LAG-3, CTLA-4, TIM-3 and PD-1 expression in thalassemia and its treatment.
Objectives: This study aimed to compare LAG-3, CTLA-4, TIM-3, and PD-1 expression in patients treated using HbF augmenting drugs or transfusions and with iron overload. These findings will provide an insight into the immune regulation in betathalassemia in response to treatment.
Methods: In this study, the expression of LAG-3, CTLA-4, TIM-3 and PD-1 was quantified using real time PCR in patients managed on blood transfusions (n=33) or HbF augmenting drugs (n=140) and compared with healthy controls (n=27).
Results: Our results show an increased expression of LAG-3 in patients regardless of treatment whereas increased CTLA-4 in patients on regular transfusions. On the other hand, the expressions of TIM-3 and PD-1 were higher in patients taking HbF augmentation therapy compared to patients on blood transfusions or the healthy controls. A very weak to no correlation was found between serum ferritin and immune checkpoints.
Conclusions: These findings are suggestive of alterations in immune regulation in betathalassemia which could be attributed to thalassemia itself, repeated exposure to blood products, recurrent infections and the immunomodulatory drugs.