Cytokine expression in the brains of Toxocara canis-infected mice

Toxocara canis can infect a number of hosts including mice and humans. In the murine host, larvae exhibit a predilection for the central nervous system, resulting in an increasing number of parasites migrating to the brain as infection progresses. Previous studies have shown that larval burdens vary between individual outbred mice receiving the same inocula, suggesting a role for immunity in the establishment of cerebral infection. Although the systemic immune response to T. canis has been widely reported, there has been no investigation of the cerebral immune response. The aim of the present study was to characterize the cerebral immune response in two inbred strains of T. canis-infected mice (BALB/c and NIH) at several time points post-infection (p.i.). Relative quantification of gene expression in the brains of these mice showed increased expression of IL-5, IL-10, IFN-gamma and inducible nitric oxide synthase (iNOS). This response was detected as early as 3 days p.i., persisting up to 97 days p.i., and was more pronounced in BALB/c-infected mice. These results have implications for the role of these cytokines and iNOS in the cerebral establishment of T. canis, and in the cerebral pathology reported during infection.