IgA Targeting in the Infant Gut Is Modulated by Diet and Increasingly Directed Towards Persistent Species

Area of Science:

• Immunology
• Microbiome research
• Pediatric nutrition

Background:

• Immunoglobulin A (IgA) is crucial for gut health and host-microbe interactions.
• Infant IgA production and milk transfer are vital, but species-level IgA binding in infants remains understudied.
• Knowledge gaps exist regarding infant IgA targets and the impact of feeding practices.

Purpose of the Study:

• To adapt and apply Metagenomic Immunoglobulin Sequencing (MIg-Seq) for analyzing IgA binding in infant fecal samples.
• To characterize species-level IgA targeting in infants at 6 and 12 months.
• To investigate the influence of complementary feeding patterns and nutrients on infant IgA targeting.

Main Methods:

• Adapted MIg-Seq for low-biomass infant fecal samples.
• Analyzed 32 longitudinal samples from 16 infants in the MINT trial (comparing feeding patterns).
• Collected samples at 6 and 12 months to assess changes pre- and post-intervention.

Main Results:

• Infant IgA targeting patterns resemble adults, with higher targeting of Pseudomonadota and lower of Bacteroidota.
• IgA targeting remained more stable than microbiome composition during infant development.
• IgA targeting of persistent colonizers, especially Bifidobacterium, significantly strengthened from 6 to 12 months.
• Specific nutrient associations found: cholesterol correlated with Bifidobacterium longum IgA targeting; carotenoids with Flavonifractor plautii and Ruminococcus gnavus targeting.

Conclusions:

• Developed a framework for species-level IgA profiling in the infant gut.
• Strengthened IgA targeting of beneficial microbes suggests a role in reinforcing the infant microbiome.
• Dietary nutrients significantly impact IgA targeting, revealing immunological consequences of complementary feeding.
• Findings support early nutritional interventions and IgA-based therapies for healthy immune-microbiome development.