A recent study reveals significant differences in human milk antibody levels against infectious pathogens between mothers in low-and-middle-income countries and high-income countries. 

The research, published in JCI, conducted up to 2024, analyzed 878 milk samples (67 colostrum and 811 mature milk) and 94 paired serum samples from 695 women across five countries: Bangladesh, Finland, Peru, Pakistan, and the U.S.

Using multipathogen protein microarrays, researchers assessed specific immunoglobulin A (IgA) and immunoglobulin G (IgG) antibodies against 1,607 proteins from 30 enteric, respiratory, and bloodborne pathogens known to cause morbidity and mortality in infants. The findings, published in The Journal of Clinical Investigation, showed that mothers from low-and-middle-income countries (LMICs) (Bangladesh and Pakistan) had broader antibody coverage against enteric and respiratory pathogens compared to those from high-income countries (HICs) (U.S. and Finland).

The study identified pathogen-specific responses: Campylobacter and Cryptosporidium elicited a dominant IgA response in human milk, while Shigella, EPEC, pneumococcus, and Staphylococcus induced both IgA and IgG responses. Maternal factors influencing human milk antibody concentrations included body mass index, parity, and total IgA in milk.

Notably, higher levels of milk IgA against the rotavirus VP4 outer capsid protein were associated with delayed time to rotavirus infection in Bangladeshi infants. Conversely, increased IgA levels were linked to a higher incidence of Campylobacter infections, suggesting a complex relationship between antibody levels and infection risk.

The researchers acknowledge limitations such as convenience sampling and potential confounding factors. Nevertheless, this comprehensive study provides insights into the global variation of human milk antibodies and their potential impact on infant health. The findings may inform strategies to boost maternal antibody concentrations for improved infant protection against infectious diseases.

Full disclosures can be found in the published study.