The potential of viral metagenomics in blood transfusion safety

Viral Metagenomics for Identification of Emerging Viruses in Transfusion Medicine

Viral metagenomics has revolutionized our understanding for identification of unknown or poorly characterized viruses. For that reason, metagenomic studies gave been largely applied for virus discovery in a wide variety of clinical samples, including blood specimens. The emerging blood-transmitted virus infections represent important problem for public health, and the emergence of HIV in the 1980s is an example for the vulnerability of Blood Donation systems to such infections. When viral metagenomics is applied to blood samples, it can give a complete overview of the viral nucleic acid abundance, also named "blood virome". Detailed characterization of the blood virome of healthy donors could identify unknown (emerging) viral genomes that might be assumed as hypothetic transfusion threats. However, it is impossible only by application of viral metagenomics to assign that one viral agent could impact blood transfusion. That said, this is a complex issue and will depend on the ability of the infectious agent to cause clinically important infection in blood recipients, the viral stability in blood derivatives and the presence of infectious viruses in blood, making possible its transmission by transfusion. This brief review summarizes information regarding the blood donor virome and some important challenges for use of viral metagenomics in hemotherapy for identification of transfusion-transmitted viruses.

Post-donation information management

Post-donation information (PDI) can be defined as any information provided by the donor or other source following a donation, that, had it been known to the blood establishment during the selection process, would have resulted in the donor's deferral. PDI reflects the shortcomings, limitations and complexity of the donor selection process. Knowledge of the causes of PDI events, their types and frequency, is a prerequisite not only for their effective management, but also for the implementation of measures to improve the selection process and the safety of donated blood. Managing PDI requires a considerable investment of time and close collaboration between the various stakeholders involved in this process. Despite its regular occurrence and the fact that PDI points to a possible problem of blood safety, very few studies have been published so far, mostly by US and Canadian authors. This review article aims at collecting and discussing available information on all aspects of PDI management, with particular reference to European experiences.

Viral metagenomics in blood donations with post-donation illness reports from Brazil

BACKGROUND

Post-donation illness can be described as appearance of clinical symptoms in blood donors after donation. The consequent call back of the donor to report these symptoms to the blood collection institution is considered a post-donation illness report (PDIR). The most suitable way to examine whether PDIR is related to infection is to apply next-generation sequencing (NGS) and viral metagenomics. Investigation into a PDIR can reveal its importance for transfusion safety and help elaborate strategies for donor education in order to prevent the transfusion transmission of infections which are not routinely tested by the blood collection services.

MATERIALS AND METHODS

We applied NGS and viral metagenomics on blood donations which were deferred due to a PDIR. Thirty-three PDIR donations obtained in the Blood Center of Ribeirão Preto, Southeast Brazil, were evaluated. Sequencing was performed using Illumina NextSeq 550 (Illumina Inc, San Diego, CA, USA) equipment and the reads obtained for each sample were analysed by specific bioinformatic pipeline for the classification and discovery of emerging viruses. The identified viral agents by metagenomics were directly confirmed by molecular methods.

RESULTS

In all PDIR donations, we found abundant reads of commensal viruses belonging to the Anelloviridae family as well as human pegivirus-1. However, we were also able to identify blood donations positive for clinically important viruses like dengue serotype-2 (DENV-2) of the Asian-American genotype and parvovirus B19 (B19V). Both viruses were also confirmed by real-time polymerase chain reaction, detecting DENV-2 RNA in a significant number of cases (7 samples, 21.2%), compared to B19V which was confirmed in 1 case (3.0%).

DISCUSSION

Our study applies for the first time viral metagenomics to evaluate the significance of PDIRs. We confirm the crucial importance of the donor providing a timely PDIR for the prevention of transfusion transmission of viral infections which are not routinely tested in the blood banks worldwide.

Beyond Cytomegalovirus and Epstein-Barr Virus: a Review of Viruses Composing the Blood Virome of Solid Organ Transplant and Hematopoietic Stem Cell Transplant Recipients

Viral primary infections and reactivations are common complications in patients after solid organ transplantation (SOT) and hematopoietic stem cell transplantation (HSCT) and are associated with high morbidity and mortality. Among these patients, viral infections are frequently associated with viremia. Beyond the usual well-known viruses that are part of the routine clinical management of transplant recipients, numerous other viral signatures or genomes can be identified in the blood of these patients. The identification of novel viral species and variants by metagenomic next-generation sequencing has opened up a new field of investigation and new paradigms. Thus, there is a need to thoroughly describe the state of knowledge in this field with a review of all viral infections that should be scrutinized in high-risk populations. Here, we review the eukaryotic DNA and RNA viruses identified in blood, plasma, or serum samples of pediatric and adult SOT/HSCT recipients and the prevalence of their detection, with a particular focus on recently identified viruses and those for which their potential association with disease remains to be investigated, such as members of the Polyomaviridae, Anelloviridae, Flaviviridae, and Astroviridae families. Current knowledge of the clinical significance of these viral infections with associated viremia among transplant recipients is also discussed. To ensure a comprehensive description in these two populations, individuals described as healthy (mostly blood donors) are considered for comparative purposes. The list of viruses that should be on the clinicians' radar is certainly incomplete and will expand, but the challenge is to identify those of possible clinical significance.