Antiproliferative effect of sera from chagasic patients on Trypanosoma cruzi epimastigotes. Involvement of xanthine oxidase.

Serum from asymptomatic or symptomatic (with cardiovascular manifestations) chagasic patients depleted of the complement system displayed an antiproliferative effect on Trypanosoma cruzi epimastigotes, RA strain, when added to the growth medium. This effect was also observed when patient's serum was depleted of specific antibodies. The antiproliferative effect was both time and concentration dependent. It was confined to the non-dialyzable, high molecular weight, fraction of the serum. This effect was abrogated by allopurinol and catalase, and enhanced by N-ethylmaleimide. Xanthine oxidoreductase and xanthine oxidase activities were increased in the chagasic sera, while catalase activity remained unchanged. Parasites exposed to chagasic sera showed a decrease in Fe/superoxide dismutase activity as well as an increase in membrane lipoperoxidation. Our data provides evidence to support the idea that the antiproliferative activity observed in sera from chagasic patients may be due, at least partially, to a direct effect of hydrogen peroxide on the epimastigotes of T. cruzi. The increase of hydrogen peroxide to antiproliferative levels might result from an increase in xanthine oxidase activity in the serum of patients infected with the parasite.