Early-life infection depletes preleukemic cells in a mouse model of hyperdiploid B-cell acute lymphoblastic leukemia

Epidemiological studies report opposing influences of infection on childhood B cell acute lymphoblastic leukemia (B-ALL). Although infections in the first year of life appear to exert the largest impact on leukemia risk, the effect of early pathogen exposure on the fetal preleukemia cells (PLC) that lead to B-ALL has yet to be reported. Using cytomegalovirus as a model early-life infection, we show that virus exposure within one week of birth induces profound depletion of transplanted B-ALL cells in two mouse models and of in situ-generated PLC in Eu-ret mice. The age_x0002_dependent depletion of PLC results from an elevated STAT4-mediated cytokine response in neonates, with high levels of IL-12p40-driven IFN-g production inducing PLC death. Similar PLC depletion can be achieved in adult mice by impairing viral clearance. These findings provide mechanistic support for an inhibitory effect of early-life infection on B-ALL progression and could inform development of therapeutic or preventative approaches. To investigate the specific cellular changes in PLC affected by an anti-MCMV immune response and the effector molecules driving them, we infected 6 day-old Eμ-ret pups with 3x10^3 plaque-forming unit (PFU) of K181-luc MCMV via intraperitoneal (i.p.) injection. We then performed RNA-seq on PLC flow-sorted from the spleens of 6 MCMV-infected and 4 PBS-infected mice 6 days after infection. RNA was isolated from 2x10^5 cells per mouse.