Impact of Oral Pre-Exposure Secretory IgA Prophylactic Produced in Rice on Gut Microbiome Homeostasis

Background/Objectives: Enterotoxigenic Escherichia coli (ETEC) is a leading cause of diarrheal illness worldwide, resulting in approximately 380,000 deaths annually, with significant morbidity in children and travelers to endemic regions. ETEC infection begins with the attachment of the bacterium to the small intestine via filamentous colonization factors (CF), followed by the production of heat-labile (LT) and heat-stable (ST) toxins that induce watery diarrhea. Targeting CF to prevent ETEC attachment is challenging due to strain heterogeneity. Methods: In previous studies, we developed a class-switched human monoclonal antibody, 68–90, expressed as secretory IgA (SIgA) in rice for cost-effective and stable storage. Rice-produced SIgA exhibited comparable binding efficiency to CfaE, a component of CF, compared to CHO-produced SIgA in vitro. Results: In this work, we showed that oral administration of 68–90 SIgA to Aotus nancymaae did not alter gut microbiome distribution or show signs of systemic exposure. Conclusions: These findings suggest that oral delivery of ETEC-specific SIgA is safe and does not disrupt the gut microbial population, highlighting its potential as an effective and targeted therapeutic strategy.