Association between the degree of immunosuppression measured by nuclear factor of activated T- cells regulated genes and cytomegalovirus infection in lung transplant recipients

Abstract

Lung transplantation (LT) is the last therapeutic option for patients with end-stage respiratory diseases. Despite advancements, LT has the lowest survival rate among all solid organ transplants (SOT), with 37% of deaths in the first year due to infections caused by the lungs’ exposure to the environment. Chronic lung allograft dysfunction (CLAD) remains the main barrier to long-term survival, causing 25-30% mortality within 3-5 years post-LT. Infections also increase the risk of CLAD, highlighting the need for better post-transplant management._x000D_ Proper immunosuppressant dosing is critical to balance infection prevention and rejection control. However, due to significant inter- and intra-patient variability, monitoring tacrolimus trough levels remains insufficient for assessing immunosuppressive states. Research is focused on identifying non-invasive biomarkers and pharmacodynamic tools to improve personalized therapy._x000D_ Cytomegalovirus (CMV) is a significant opportunistic infection after SOT, raising the risk of infections, acute rejection, and CLAD through its immunomodulatory effects. CMV disease rates range from 8% to 55%, depending on prophylaxis duration and type. Universal antiviral prophylaxis, usually given for six to 12 months, reduces CMV disease risk but can cause side effects. Notably, 25% of CMV-seropositive patients still develop CMV infection, and 15% develop CMV disease within 18 months post-LT. Although CMV-specific cellular immune response (CMV-CMI) is essential for infection control, current risk assessment focuses only on humoral markers, leaving a gap in evaluating CMV-CMI in LT recipients (LTR)._x000D_ This thesis aimed to evaluate two promising immunological tests: (1) measuring residual gene expression of three NFAT-regulated genes (IL-2, IFN-γ, and GM-CSF), and (2) using the CMV enzyme-linked immunosorbent spot (ELISPOT) test. These tests were designed to improve therapeutic drug monitoring and identify LTRs at higher infection risk, especially for CMV._x000D_ The first study found that tacrolimus trough levels, currently used for drug monitoring, did not correlate with immunosuppression levels measured by NFAT-regulated gene expression (NFAT-RGE) or predict infection or rejection risk. In contrast, tacrolimus peak levels showed a strong correlation with NFAT-RGE. Importantly, NFAT-RGE values below 30% were linked to a higher risk of severe bacterial infections, suggesting its potential as a non-invasive infection risk assessment tool. Additionally, pre-LT genotyping of cytochromes P450 3A4 (CYP3A4) and P450 3A5 (CYP3A5) could help identify fast metabolizers (FM), prone to infections, and poor metabolizers (PM), at risk of worse graft outcomes due to low tacrolimus levels._x000D_ The second study assessed the CMV ELISPOT test, which measures CMV-specific immune responses. Although it could not reliably predict which patients would develop CMV infection, its predictive value improved when both antigens were tested together. Among seropositive patients, those showing intermediate (response to one antigen) or weak (response to neither antigen) CMV-CMI had significantly higher infection rates between six and 18 months post-LT. In contrast, patients with strong CMV-specific responses were 49% less likely to develop severe CMV infections. This approach could guide personalized immunosuppression adjustments and CMV prophylaxis modifications._x000D_ In conclusion, this thesis highlights the potential of NFAT-RGE measurement as a tool for personalized immunosuppressive therapy and the CMV ELISPOT test for assessing CMV infection risk in LTRs. These findings open avenues for further clinical research and improved patient management strategies.

Date of Award	18 Mar 2025
Original language	English
Supervisor	Susana Gomez Olles (Director) & Victor Monforte Torres (Director)