Virus Detection in Newly Diagnosed Pediatric Acute Lymphoblastic Leukemia
Authors: Leijonhufvud Gustaf , Machado Gabriel , Ljungman Gustaf , Bogdanovic Gordana , Allander Tobias , Andersson Björn , Gustafsson Britt 
Published: December 2024

Introduction: Viruses could play a role in the pathogenesis of pediatric acute lymphoblastic leukemia (ALL). Viruses may integrate into the genome of precursor B cells, resulting in disrupted differentiation and proliferation. Common pathogens may also act by causing an unusual response in genetically and immunologically disposed children, resulting into the development of ALL, especially in the childhood peak, 2-5 years of age. Lymphoid cancers are of special interest as viral infections in this group may affect immunologically untrained cells and thereby increase the risk of developing ALL (Greaves, et al. Leukemia 2021).

Metagenomic sequencing is a powerful tool for unbiased characterization of the viral flora of clinical samples and sample collections. Advantages of this approach include the possibility of finding all viruses, including novel strains and viruses that are normally not tested for by regular diagnostic assays. When screening for disease associations, including viruses involved in cancer development, this analysis method is well suited for the purpose. The rapid increase in the capacity of NGS and improved bioinformatics methods have enabled large scale metagenomics studies where microbial communities are characterized using shotgun sequencing (Capobianchi, et al.Clincial Microbiology and Infection 2013).

Methods: A large cohort of diagnostic samples from time of diagnosis from pediatric patients with various cancers at different ages was investigated for the presence of specific viruses by shotgun metagenomic sequencing, followed by PCR confirmation. Children were recruited from the Department of Pediatric Hematology and Oncology, Uppsala Children's University Hospital and registered at Uppsala Biobank. The study was approved by the Regional Ethical Review Board, Uppsala Dnr: 2018/258.

Several human viruses could be identified. A subset of this cohort, a total of 66 precursor B-cell-ALLpatient samples diagnosed between 0-5 years of age, collected between 1989 and 2018 were compared with a control group of 82 non-leukemic patients.

Results: GBV-C was the only virus with a significantly higher frequency in this group of leukemia patients compared to the non-leukemic controls. 11/66 (16.6%) from the ALL group was found positive and in the non-leukemia pool 4/82 (4.9%) individuals were positive. The higher frequency of GBV-C infection among leukemia patients was significant by chi-squared test (p &lt; 0.02).

Discussion:. GBV-C is a single-stranded RNA virus belonging to the genus Pegivirus in the Flaviviridae family. Documented routes of transmission are exposure to infected blood, vertical transmission from mother to child and sexual contact (Bhanich Supapol,et al.The Journal of Infectious Diseases 2009). In healthy individuals, the viremia is in most cases cleared within the first 1-2 years, but in in immunocompromised individuals the infections can persist (Gutierrez, et al. Journal of Medical Virology1997). Worldwide studies have shown that the prevalence of the viremia among healthy adult blood donors is 1-2% (Roth,et al.Transfusion1997). A study of otherwise healthy children presenting for elective day surgery in Melbourne, Australia showed 1.3% prevalence of the pegivirus (Sibert,et al.Journal of Paediatrics and Child. Health 2002). A similar prevalence, 1.4% was found in 901 school children in Denmark (Christensen, et al. Journal of Medical Virology 2003). The results from this study indicate that children diagnosed with ALL have a significantly higher prevalence of GBV-C viremia at diagnosis than non-leukemic controls.

In summary our results highlight the abundance of systemic virus infections in children, and the value of metagenomic sequencing for hypothesis forming regarding the associations between virus infections and development of ALL. The higher frequency of GBV-C infection among leukemia patients was significant, indicating a possible association with leukemia.