Charting the impact of maternal antibodies and repeat exposures on sapovirus immunity in early childhood from a Nicaraguan birth cohort

Sapovirus is an important cause of acute gastroenteritis in childhood. While vaccines against sapovirus may reduce gastroenteritis burden, a major challenge to their development is a lack of information about natural immunity. We measured sapovirus-specific IgG in serum collected, between 2017 and 2020, of mothers soon after delivery and at 6 time points in Nicaraguan children until 3 years of age (n=112 dyads) using virus-like particles representing three sapovirus genotypes (GI.1, GI.2, GV.1). Sixteen (14.3%) of the 112 children experienced at least one sapovirus gastroenteritis episode, of which GI.1 was the most common genotype. Seroconversion to GI.1 and GI.2 was most common between 5 and 12 months of age, while seroconversion to GV.1 peaked at 18 to 24 months of age. All children who experienced sapovirus GI.1 gastroenteritis seroconverted and developed genotype-specific IgG. The impact of sapovirus exposure on population immunity was determined using antigenic cartography: newborns share their mothers' broadly binding IgG responses, which declined at 5 months of age and then increased as infants experienced natural sapovirus infections. By tracking humoral immunity to sapovirus over the first 3 years of life, this study provides important insights for the design and timing of future pediatric sapovirus vaccines.