Gonadectomy inhibits development of experimental amoebic liver abscess in hamsters through downregulation of the inflammatory immune response

Incidence of amoebic liver abscess (ALA) in human males is considerably higher than in females, suggesting a role for sex hormones in this parasite infection. We describe here the effect of hamster gonadectomization on the development of ALA. After monitoring the decrease of oestradiol in females and testosterone in males to undetectable levels by ELISA and Radio Immuno Assay (RIA) in serum, hamsters were intraportally infected with Entamoeba histolytica trophozoites and killed 7 days later. ALA was absent in 50% of male and 15% of female gonadectomized (Gdx) hamsters, in comparison with 100% infection in non-Gdx controls. This protection against ALA in Gdx hamsters was concomitant to a comparatively scarce inflammatory infiltrate and necrosis surrounding clusters of trophozoites in the liver tissue, as well as to a lack of response of spleen cells to Con A, evaluated in proliferation assays. As tissue damage in ALA has been associated with a local inflammatory Th1 response, we determined the profile of response in hamsters by immunohistochemistry on liver sections. In contrast to strong Th1 responses in non-Gdx animals, Gdx females and males exhibited Th2 and Th3 profiles of cytokines, respectively, suggesting that protection against ALA following gonadectomization, could be related to downregulation of liver Th1 response during amoebic infection.