Transamniotic Fetal Immunotherapy (TRAFIT) with Secretory IgA: A Potential Novel Ancillary Strategy for the Prevention of Necrotizing Enterocolitis

Secretory immunoglobulin-A (SIgA), which is not produced perinatally, binds bacteria enhancing mucosal immunity. Higher levels of intestinal bacteria bound by SIgA are protective against necrotizing enterocolitis. Transamniotic fetal immunotherapy (TRAFIT) has previously been used to deliver SIgA to the fetal digestive tract, however with unclear functional impact. We sought to determine whether SIgA administered via TRAFIT could functionally bind intestinal bacteria postnatally. Fetuses (n=38) from four dams underwent intra-amniotic injections of human SIgA on gestational-day 19 (E19; term=E22-E23). After spontaneous delivery, pups were survived for 1-2 days postnatally before intestinal contents were procured and submitted to flow cytometry. Specimens were stained for bacteria (Syto-GFP) and human-SIgA (PE) to prevent cross-reactivity with maternal rat SIgA. Overall survival was 94.7% (36/38). SIgA-bacterial complexes were identified in all samples at all time points showing significantly higher positive PE events than unstained controls (p=0.03-0.05). The proportion of bacteria bound by IgA decreased daily, from 45.6% to 29.9% bound at 4 to 6 days post-TRAFIT, respectively (overall p=0.05). Transamniotic fetal immunotherapy with secretory-IgA leads to functionally IgA-bound bacteria into the postnatal period and may be a novel strategy for enhancing early mucosal immunity, potentially protecting the neonate against necrotizing enterocolitis.