Abstract Rationale Bronchiolitis obliterans syndrome (BOS) develops in approximately 2-4% of patients following hematopoietic stem cell transplantation (HCT), and remains a challenging condition with no curative therapy and limited predictive indicators. Existing mouse models often fail to fully capture the severity and consistency of BOS pathogenesis. We previously identified that herpesvirus reactivation within the first 100 days after HCT significantly increases BOS risk. In this study, we aim to establish a novel mouse model of BOS by combining allo-HCT with herpesvirus infection. Methods Allogeneic HCT was performed by transplanting bone marrow and splenocytes from C57BL/6 donors into lethally irradiated B6D2F1 recipients. Cyclophosphamide was administered post-transplantation to mitigate acute graft-versus-host disease (aGVHD). Sixty days after transplantation, recipient mice were infected with murine gammaherpesvirus 68 (MHV-68), a murine analogue of Epstein-Barr virus. At 21 days post-infection, tissues including lung, liver, skin, and gut were collected for histological analysis. Results A single dose of cyclophosphamide (25 mg/kg at day 4 post-transplantation) effectively prevented mortality due to aGVHD. High-dose MHV-68 infection (1 × 10⁴ PFU) resulted in complete lethality by 11-12 days post-infection, whereas lower-dose infection (4 × 10² PFU) permitted survival beyond 21 days. Histological analysis revealed mild immune cell infiltration and relatively normal airway architecture in naïve allo-HCT mice. In contrast, MHV-68-infected allo-HCT mice displayed pronounced immune cell infiltration, particularly around the airways, and Masson’s trichrome staining demonstrated collagen accumulation within parabronchial spaces, although airway architecture remained intact. These findings suggest that ongoing immune cell recruitment and collagen deposition may drive more severe BOS-like symptoms at later timepoints following MHV-68 infection. Conclusions Our results indicate that post-HCT administration of cyclophosphamide enables survival through aGVHD, facilitating the investigation of chronic lung pathology following herpesvirus infection. This model holds promise for elucidating BOS pathogenesis and may serve as a valuable platform for future therapeutic studies. This abstract is funded by: NIH
Zhou et al. (Fri,) studied this question.