Trypanosoma congolense Infections : Induced Nitric Oxide Inhibits Parasite Growth In Vivo

Abstract EN

Wild-type (WT) C57BL/6 mice infected intraperitoneally with 5×106 Trypanosoma congolense survive for more than 30 days.

C57BL/6 mice deficient in inducible nitric oxide synthase (iNOS−/−) and infected with 103 or 5×106 parasites do not control the parasitemia and survive for only 14±7 or 6.8±0.1 days, respectively.

Bloodstream trypanosomes of iNOS−/− mice infected with 5×106 T.

congolense had a significantly higher ratio of organisms in the S+G2+M phases of the cell cycle than trypanosomes in WT mice.

We have reported that IgM anti-VSG-mediated phagocytosis of T.

congolense by macrophages inhibits nitric oxide (NO) synthesis via CR3 (CD11b/CD18).

Here, we show that during the first parasitemia, but not at later stages of infection, T.

congolense-infected CD11b−/− mice produce more NO and have a significantly lower parasitemia than infected WT mice.

We conclude that induced NO contributes to the control of parasitemia by inhibiting the growth of the trypanosomes.