Targeting Ischemia/Reperfusion Stress to Inhibit Cytomegalovirus Reactivation After Lung Transplant - PROJECT SUMMARY
Cytomegalovirus (CMV) is the most common opportunistic infection in lung transplant recipients, with the
highest risk seen in seronegative recipients (R-) of seropositive organ donors (D+). While anti-rejection
immunosuppression (IS) has been implicated as a primary cause of CMV reactivation, our studies have newly
suggested otherwise. We have recently shown that CMV reactivation occurs independent of IS and seemingly
independent of the allo-immune response following a D+/R- kidney transplant in mice. Treatment with a regimen
of clinically relevant IS, while failing to induce CMV reactivation in latently infected mice (no transplant), does
permit subsequent viral replication and dissemination following transplant, despite inhibition of the host rejection
response and inflammation. These findings suggest that ischemia/reperfusion (I/R) stress inherent in a transplant
procedure due to organ preservation and revascularization is necessary and sufficient to induce reactivation.
However, molecular mechanisms underlying I/R stress mediated transcriptional reactivation from latency in the
grafts remain elusive. The goal for this study is to identify key molecular pathways responsible for I/R stress-
mediated CMV reactivation and to develop effective therapeutics to prevent both I/R injury and CMV reactivation
following lung transplant. In our preliminary studies using a mouse model of syngeneic D+/R- lung transplant,
we observed that expression of MCMV immediate early (IE) genes is induced within 48 hours of transplant
surgery, followed by increased viral DNA replication in the lung grafts and dissemination to peripheral organs by
day 14 post-transplant. We revealed that pre-transplant depletion of donor alveolar macrophages (AMs)
decreased viral load in transplanted lungs and salivary glands, suggesting that AMs are primary sites of MCMV
latency and reactivation, consistent with the findings from HCMV studies. We have further showed that Myeloid
differentiation primary response 88 (Myd88) was critical in mediating transplant induced I/R injury, likely via
activation of transcription factors (TFs) NF-kB, AP-1 and XBP-1. These TFs are shown to bind to MIEP and
promote MCMV/HCMV reactivation. Thus, we hypothesize that I/R stress mediates Myd88 dependent activation
of TFs in viral harboring donor lung cells (e.g. AMs); leading to reactivation of latent CMV in the transplanted
lungs. Thus, tissue/cell specific inhibition of Myd88 pathways in latently infected lung donors may prevent viral
reactivation. We will use a preclinical mouse model of lung transplantation to test our hypotheses. In Aim 1, we
will 1) investigate how donor macrophage-derived Myd88 regulate expression of viral IE genes and viral DNA
replication by utilizing genetically modified time-specific myeloid Myd88 knockout mice and 2) delineate impact
of Myd88 on I/R stress mediated signaling pathways in the lung cells using single cells RNA analysis. In Aim 2,
we will determine the therapeutic potentials of tissue/cell-specific targeting of Myd88 in mitigating I/R stress and
MCMV reactivation and dissemination leveraging our novel nanocarrier delivery system. Data generated from
this study will provide proof of concept for developing novel therapeutics for further clinical translation.
