Longitudinal analysis of mature breastmilk and serum immune composition among mixed HIV-status mothers and their infants *

Summary Background & aims Understanding mature breastmilk immunology may benefit infants chronically exposed to infectious pathogens in resource-limited regions. Methods This prospective rural/semi-rural Tanzanian cohort of women (n = 102 at delivery; 38% HIV-positive) and their infants (n = 102) investigated breastmilk, maternal and infant serum immunoglobulins (IgA/IgG 1–4 /IgM) and cytokines (IL-1β/IL-2/IL-6/IL-10/IL-12p70/IL-13/IL-15/TNF-α/IFN-γ) at 1, 2, 3, 6-months postpartum. Results Milk immunoglobulins followed an inverse U-shaped pattern, while cytokine patterns were mixed. Exclusive breastfeeding duration and feeding intensity were associated with greater breastmilk total immunoglobulin and IgA, IgG 1-3 and IL-12p70 concentrations. Maternal mastitis, fever or cough was associated with higher breastmilk total cytokine concentrations, while infant fever was associated with lower milk immunoglobulins or cytokines. Strong (r ≥ 0.40) to weak (r = 0.20–0.29) positive correlations between maternal serum-breastmilk or breastmilk-infant serum immunoglobulins were evident. Breastmilk cytokines were moderate to weakly negatively correlated with infant serum. Breastmilk immunology did not differ by maternal malnutrition or HIV-seropositivity. Conclusions Mature breastmilk is a dynamic source of many specific and non-specific immune factors associated with maternal and infant health and infant nutrition. Breastfeeding practices are associated with differential breastmilk immunological composition providing immunological support for universal recommendations to exclusively breastfeed for 6-months.