Fig 1. Protein malnutrition in weaned mice disrupts Giardia clearance, promotes increased microbial-pathogen abundance in small intestine, and establishes cytokine profiles associated with persistent Giardia infection.

(A) Experimental timeline of Giardia challenge in 3 week-old C56Bl/6 mice initiated on either control diet (CD) or protein-deficient diet (PD) upon arrival and continued throughout the duration of the experiment. G. lamblia (Assemblage B, H3) infection occurred on experimental day 0. Data for this and subsequent experiments were obtained during either early timepoints when mice on both diets remained infected with Giardia (day 5–7) or later timepoints (up to 28 days) (persistent) when only mice fed PD diet remained infected. (B) Duodenal Giardia burden at day 5 (left) and duodenal and ileal Giardia burden on day 28 (right) post-challenge in either CD or PD-fed mice and uninfected controls. (C) Histopathology of duodenum in infected mice fed PD diet (20x, H&E, arrows designate trophozoites). (D) Growth in mice (as % weight increase between day 5 and day 0). (E) Small intestinal bacterial abundance by total 16S rRNA universal primers and (F) quantification of the V3-V4 region amplification product. (G) Krona visualizations of 16S rRNA OTUs in the upper small intestine high-abundance taxa (>10,000 reads per OTU) in mice fed CD (left) or PD (right) 5 days after Giardia lamblia (bottom) compared with age and diet-matched controls (top) as indicated. (H) Phyla-level 16S rRNA relative abundances in upper small intestine 5 days after G. lamblia challenge compared with age and diet-matched controls. (I) Flow cytometry of duodenal lamina propria leukocytes (LPL) day 5 post-challenge, stained for leukocytes (CD45⁺) and frequency of myeloid (CD11b⁺), T- (CD3⁺) and B- (B220⁺) cells and (J) Cytokine protein levels in duodenum shown as fold change relative to uninfected CD-fed controls (PBS). For all studies n = 4/group; *P<0.05, **P<0.01.