Date of Award


Document Type

Thesis (Ph.D.)

Department or Program

Quantitative Biomedical Sciences

First Advisor

Margaret Karagas

Second Advisor

Jiang Gui


The bidirectional relationship between the gut microbiome and immune system plays an important role in host immune status: the immune system provides the gut microbiome the optimal environment to thrive in, and the gut microbiome helps regulate the immune system. This relationship is especially important in infants, whose immune system is still premature and rely on innate immunity.

We investigated the three-way interplay among early-life exposures, the developing gut microbiome, and outcomes in infancy from the general population in New Hampshire, US. We used prospective cohort data from the New Hampshire Birth Cohort study to 1) determine whether timing of baby rice cereal introduction is related to respiratory infections, symptoms, and allergy in infancy; 2) identify gut microbiome composition and bacterial species that may influence respiratory infections and symptoms; 3) identify bacterial species and metabolic pathways that associate with antibody response to pneumococcal capsular polysaccharide and tetanus toxoid vaccination; and 4) develop a statistical approach to test the mediating effect of the microbiome on the “causal” path between exposure and outcome. Our studies highlight the potential to modulate the infant gut microbiome to improve health outcomes in infancy.

Original Citation

Moroishi, Y., Signes-Pastor, A.J., Li, Z. et al. Infant infections, respiratory symptoms, and allergy in relation to timing of rice cereal introduction in a United States cohort. Sci Rep 12, 4450 (2022).

Manuscript currently in press at Pediatric Research