Introduction & aim: Changes in respiratory bacterial microbiome have been found in lung transplantation (LT) and have been related to chronic allograft dysfunction (CLAD). However, there is less information about changes in virome composition in LT. The aim of this study was to characterize plasma virome composition and dynamics following LT and its possible relationship with CLAD

Methods: In this retrospective longitudinal study, we analysed the virome of 286 plasma samples from 77 LT patients at different time-points and 20 from healthy controls. Nucleic acids were extracted, amplified by SISPA method and sequenced. Reads were filtered out by quality and taxons were assigned using Kaiju. Diversity was analysed by Shannon index, Bray-Curtis dissimilarity and Aitchison distance

Results: Anelloviridae family was the mostfrequent and abundant in the whole population. However, it was more frequent(p<0.0001) and abundant among LT patients than healthy controls (69.2% and 37.6% respectively). Interestingly, in LT patients the second more abundant family was Flaviridae (15.6%), a family not even found in controls. Alpha diversity was lower in LT patients comparing to healthy controls (p= 0.02) and virome composition was also different between both groups (p= 0.035). Virome composition from LT patients who developed CLAD (30 of 77 patients) was significantly different compared to LT CLAD-free patients (p=0.002)

Conclusion: Anelloviridae was the most frequent and abundant viral family. LT patients virome differ from that in healthy controls and interestingly, also a different virome composition was observed between CLAD and CLAD-free patients.

Funded by ISCIII (PI18/00035)