Eosinophil Deficiency Compromises Parasite Survival in Chronic Nematode Infection

Abstract

Immune responses elicited by parasitic worms share many features with those of chronic allergy. Eosinophils contribute to the inflammation that occurs in both types of disease and helminths can be damaged or killed by toxic products released by eosinophils in vitro. Such observations inform the widely held view that eosinophils protect the host against parasitic worms. The mouse is a natural host for Trichinella spiralis, a worm that establishes chronic infection in skeletal muscle. We tested the influence of eosinophils on T. spiralis infection in two mouse strains in which the eosinophil lineage is ablated. Eosinophils were prominent in infiltrates surrounding infected muscle cells of wild-type mice; however, in the absence of eosinophils T. spiralis muscle larvae died in large numbers. Parasite death correlated with enhanced IFN-γ and decreased IL-4 production. Larval survival improved when mice were treated with inhibitors of inducible nitric oxide synthase, implicating the nitric oxide pathway in parasite clearance. Thus, the long-standing paradigm of eosinophil toxicity in nematode infection requires reevaluation, as our results suggest that eosinophils may influence the immune response in a manner that would sustain chronic infection and insure worm survival in the host population. Such a mechanism may be deployed by other parasitic worms that depend upon chronic infection for survival.

Increase in neutrophil count after repeated exposure of Plasmodium berghei-infected mice to artemisinin

“…Basophils have an important role in the allergic process, while eosinophils play a major role in the process of infection by parasitic worms. (19) The average value of basophils from this study ranged from 0 to 0.4%. These results do not show significantly different increases from the physiological value of basophils of 0 to 0.3%.…”

Domestic dog health worsens with socio-economic deprivation of their home communities

“…Underlying causes for the WBC abnormalities seen in the dogs are uncertain, but eosinophilia is often attributable to ectoparasites or other macroparasites, such as helminths (Fabre et al 2009). Leukocytosis and lymphocytosis may be due to epinephrine-mediated responses associated with blood collection or in some instances, inflammation.…”

Trichinella spiralis reinfection: changes in cellular and humoral immune response in BALB/c mice

“…Kang et al (2012) observed eosinophils around the nurse cells 4 weeks p.i. Eosinophils are not necessary for killing larvae and a recent study suggested that eosinophils may affect the immune response in a manner that would sustain chronic infection and ensure worm survival within the host (Fabre et al, 2009). T. spiralis muscle larvae death was correlated with enhanced IFN-γ and reduced IL-4 production (Kang et al, 2012).…”