Fig. 4: Protein deficiency is required for Giardia-mediated weight loss and increased intestinal permeability in immunodeficient mice.

a–c Cubicle-housed GF-Rag 2^−/− mice fed either PD or control diet (CD) and challenged with either PBS or 10⁵-commercial Giardia cysts as indicated (a). Weights as percent change after challenge, two independent experiments: PD-PBS (N = 11, cohort-1 (N = 5), cohort-2 (N = 6); PD-Giardia (N = 12 cohort-1 (N = 5), cohort-2 (N = 7)), CD-Giardia (N = 12, cohort-1 (N = 3), cohort-2 (N = 9)) (mean ± SEM; ^{^^^}P = 0.001 CD-Giardia vs PD-PBS; ****P < 0.0001 PD-Giardia vs PD-PBS, ^####P < 0.0001 CD-Giardia vs PD-Giardia. Exact P-values provided in source data file. Details for each independent experiment in Supplementary Fig. 5). b Serum FITC concentration on day 15 (cohort-1) (median ± IQR; *P = 0.0067 Giardia^CD (N = 6, 3 mice excluded due to insufficient sample) versus Giardia^PD (N = 7), Kruskal-Wallis, Dunn’s multiple comparisons test; P = 0.035 for PBS^PD vs Giardia^PD two-sided Mann-Whitney U-test). c Trophozoites in the upper small intestine on day 15 (cohort-2) (CD (N = 3), PD (N = 5)) (mean ± SEM). d Weights as percent change in PD-fed mice after challenge with Giardia (N = 6), fecal microbiota transfer (FMT) from PD-fed SPF mice (N = 7), both (N = 7), or PBS (N = 6) (mean ± SEM; **P = 0.003 Giardia vs PBS; ^##P = 0.004, ^###P = 0.0007 Giardia-FMT vs PBS; ^{^}P = 0.02, ^{^^}P = 0.005, ^{^^^}P = 0.0005 Giardia-FMT vs FMT; ^%%P = 0.006, ^%%%P = 0.0006 Giardia vs FMT). e Trophozoites in the upper small intestine on day 12 (mean ± SEM, Giardia (N = 6), Giardia-FMT (N = 6, one mouse excluded due to a missing sample). f–j 10³ axenic Giardia cyst challenge in isolator-housed GF-Rag 2^−/− mice or GF-WT mice fed either CD or PD as indicated. f, g CD-fed mice. f Weights as percent change beginning 7 days prior to challenge (mean ± SEM, PBS (N = 5), Giardia (N = 6)). g Serum FITC concentration on day 25 (median ± IQR, PBS (N = 8), Giardia (N = 6)). h–j (left) WT mice fed PD diet since weaning (PBS (N = 6), Giardia (N = 4; excluded is one mouse with immediate gavage trauma) through day 21 post-challenge and (right) Rag 2^−/− mice fed PD diet for 7 days prior to challenge and through day 25 post-challenge (PBS(N = 8), Giardia (N = 9)). h Trophozoites in the small intestine. i Weights as percent change after challenge (mean ± SEM, **P = 0.003 day 11, 0.004 day 12, 0.001 day 13, and ***P < 0.0001 day 16, 18–25 (P = 0.0002 day 17) Rag 2^−/− PBS versus Rag 2^−/− Giardia). j Serum FITC concentration (median ± IQR, excluded are one PBS-challenged for N = 7 and three Giardia-challenged mice for N = 6 and due to insufficient sample, *P = 0.022, two-sided Mann-Whitney U-test). a, d, i Two-way ANOVA, repeated measures, Bonferonni multiple comparisons test. Data are from biologically independent mice/samples from each independent experiment. Source data are provided as a Source Data file.