Pregnancy and Early-Life Gut Virome in the Lifelines NEXT cohort:Origin, Persistence, Influencing Factors and Health Implications

The human gut virome is a key modulator of gut microbial ecology and function, yet its role in early gut ecosystem development remains poorly understood. Here, we profiled the DNA virome from 4,523 fecal and 91 breastmilk metagenomes from 714 mother-infant pairs in the Dutch birth cohort Lifelines NEXT. This analysis generated a catalog of 31,205 unique vOTUs, with 31,019 detected in fecal and 248 in breastmilk samples, including 16,540 not previously reported in other databases. We find that the maternal virome is largely stable, in contrast to the infant viromes rapid diversification over time. We also identify delivery and feeding modes as major drivers of infant virome developmental trajectories, with additional influences of maternal parity, infections during pregnancy, socioeconomic factors, gestational age and infant birth weight. Notably, increased viral diversity was associated with the infant developing a food allergy. Strain-level virome profiling confirmed the maternal gut as the primary source of viruses for the infant gut, with increased sharing rates in vaginally delivered infants and with breastmilk as a secondary reservoir. We demonstrate that temperate phages frequently co-transmit with their bacterial hosts and identify multiple protein families associated with anti-defense functions enriched among maternally shared viruses. Finally, we show that DNA adenine N6-methyltransferase hin1523, together with widely active diversity-generating retroelements, promote long-term viral persistence in the infant and maternal gut. Together, these findings establish the origin, dynamics and modulating factors of the infant gut virome, along with the genetic strategies supporting its persistence in the gut ecosystem.