Clinical bottom line
Patients receiving emerging anti-CD19 chimeric antigen receptor (CAR) T-cell therapies for B-cell malignancies face a complex infectious risk profile characterized by early and late infections, including bacterial, viral reactivations, and opportunistic infections. Prophylactic antiviral strategies, particularly for hepatitis B virus (HBV) reactivation, and vigilant monitoring for cytopenias and immune recovery are critical components of infection management. Current evidence supports individualized infection risk assessment and multidisciplinary care to optimize outcomes in this vulnerable population (Yoo et al., 2023; Li et al., 2021).
What the evidence shows
Anti-CD19 CAR T-cell therapy has revolutionized treatment for relapsed/refractory B-cell malignancies but is associated with significant infectious complications due to profound and prolonged immunosuppression. Yoo et al. (2023) provide a detailed overview of adverse event management in young adults and children with acute B-cell lymphoblastic leukemia receiving anti-CD19 CAR T-cell therapy, highlighting infections as a major cause of morbidity. Early infections tend to be bacterial, often related to neutropenia and mucosal barrier injury, while late infections include viral reactivations and opportunistic pathogens.
Li et al. (2021) specifically investigated HBV reactivation risk in patients with resolved HBV infection undergoing anti-CD19 CAR T-cell therapy without antiviral prophylaxis. They reported a notable risk of HBV reactivation, underscoring the importance of pre-therapy HBV screening and consideration of prophylactic antiviral therapy to mitigate this risk.
Thrombocytopenia is a frequent hematologic toxicity post-CAR T-cell therapy, which can indirectly increase infection risk by complicating invasive procedures and prolonging hospitalization. Baur et al. (2021) describe the use of thrombopoietin receptor agonists to manage acquired thrombocytopenia after anti-CD19 CAR T-cell therapy, which may contribute to improved supportive care and infection risk reduction.
Molecular disease monitoring studies by Colton et al. (2024) emphasize the importance of close surveillance for disease relapse and immune recovery, which can inform infection risk stratification and timing of prophylactic interventions. Emerging CAR-T engager proteins (Su et al., 2022) may optimize CAR T-cell function and potentially modulate infection risk profiles, although clinical implications remain to be fully elucidated.
Caveats and uncertainty
The evidence base for infection management in anti-CD19 CAR T-cell recipients remains limited by small cohort sizes, heterogeneous patient populations, and evolving therapeutic protocols. Most data derive from single-center or retrospective studies, limiting generalizability. The optimal duration and choice of antiviral prophylaxis for HBV and other latent viruses are not yet standardized. Additionally, the long-term impact of CAR T-cell–induced B-cell aplasia and hypogammaglobulinemia on infection risk requires further prospective evaluation.
There is also uncertainty regarding the best strategies for bacterial and fungal prophylaxis, as well as vaccination timing post-CAR T-cell therapy, given the variable kinetics of immune reconstitution. The role of novel supportive agents like thrombopoietin receptor agonists in infection prevention warrants confirmation in larger studies.
How this may change practice
Clinicians managing patients undergoing anti-CD19 CAR T-cell therapy should implement comprehensive infection risk assessments, including screening for latent infections such as HBV, and consider antiviral prophylaxis in at-risk individuals. Early recognition and treatment of bacterial infections remain paramount, with attention to neutropenia and mucosal integrity.
Monitoring hematologic toxicities and employing supportive measures such as thrombopoietin receptor agonists may indirectly reduce infection-related complications. Molecular disease monitoring can guide individualized infection surveillance and prophylaxis strategies.
Multidisciplinary collaboration involving hematology, infectious diseases, and pharmacy is essential to optimize antimicrobial stewardship and supportive care protocols tailored to this emerging patient population. Ongoing research and clinical trials will be critical to refine evidence-based guidelines for infection prevention and management in anti-CD19 CAR T-cell therapy recipients.