Filarial Parasites Develop Faster and Reproduce Earlier in Response to Host Immune Effectors That Determine Filarial Life Expectancy
Litomosoides sigmodontis filarial nematodes developed slower during their larval stages in IL-5 deficient (IL-5−/−) mice than in C57BL/6 wild type controls as measured (A) by their shorter lengths (** p = 0.015, ANOVA; n = 50 larvae nested in 5 mice per group) and (B) by their delayed moulting to the 4th larval stage at D10 p.i. (** p = 0.0007, Chi2 test; n = 5 mice). (C) At D30 p.i., however, no differences in the moulting rate to the adult stage were observed between IL-5−/− mice and wild type controls (n = 5 mice). The constitutive absence of eosinophils in PHIL mice resulted in slower larval development as judged by (D) their lengths in both male and female mice (*, p = 0.04 for the effect of mouse strain when variation due to mouse sex is accounted for, GLM; n = 57 to 59 in 7 mice) and by (E) their moulting rates (p = 0.02, Fisher Exact Test; n = 7 mice) at D12 p.i. as compared to C57BL/6 wild type controls. None of the treatments affected larval survival (see Figure S2A and S2B). Error bars depict s.e.m.