Cytomegalovirus after allogeneic hematopoietic stem cell transplantation: reactivation or reinfection?

Objective. To determine type of cytomegalovirus (CMV) infection (reactivation of a virus strain that was present before transplantation or re-infection with another virus strain) in allogeneic hematopoietic stem cell recipients by sequencing. Materials and Methods. Clinical and laboratory data of 179 recipients of allogeneic hematopoietic stem cells collected from 2014 to 2018 were analyzed for CMV DNA in clinical specimens before and after transplantation. A total of 14 patients (28 samples) were included in the study. The CMV UL139 gene encoding viral glycoprotein was chosen for virus genotyping and sequence alignment. The primers complementary to its conservative sites were used. The resulting DNA sequence was analyzed using nucleotide BLAST software (https://blast.ncbi.nlm.nih.gov/Blast.cgi) and Genome compiler (https://designer.genomecompiler.com). The type of infection was determined by comparing DNA sequences before and after transplantation. Results. All enrolled patients were anti-CMV-positive prior to transplantation, which indicates the presence of CMV infection. Therefore, none of the patients had a primary infection as a result of transplantation. Of 14 patients, high percentage of sequence alignment (~100%) was observed in 8 patients. For the other 6 patients, substantial differences in sequences which indicate the different genotypes and the different type of infection were found. However, there was no statistically significant difference in the time to viral DNA appearance after transplantation in patients with re-infection and reactivation (p > 0.05), nor was there a statistically significant correlation between the type of infection (reactivation/re-infection) and the main diagnosis or transfusion load. Conclusions. Reactivation of the previously registered viral strain and re-infection with another viral strain were equally probable (8 vs. 6 cases). There were no associations between the main diagnosis and the type of infection (reactivation/re-infection) possibly due to a small sample size. Time to post-transplantation CMV DNA detection in blood was longer for re-infection (median of 69.5 days) compared to reactivation (median of 27 days), but this difference was also non-statistically significant. In addition, there was no significant contribution of blood transfusion burden to the type of CMV infection, which may suggest the donor blood is not a source of the different strains.