Question

Describe the detoxification mechanisms used by Leishmania to
counteract the toxic effects of reactive oxygen intermediates (ROIs)
and reactive nitrogen intermediates (RNIs) produced by the host. How
was the relative contribution of ROIs and RNIs in the control of
leishmaniasis determined in a mouse model of infection?

Answer 1

Reactive oxygen species (ROS) are a part of the immune system, and they confer protection on the host against a large number of pathogenic microorganisms. These ROS’ exhibit various activities parasites of the genus Leishmania: for example, some species are susceptible, while others are not.

In vitro experiments seem to suggest than ROS do not seem to be important in killing parasites, rather they regulate the inflammatory response probably by activating and regulating the numbers of neutrophils in lesions.

These species are also important agents which act against intracellular pathogens, induced by IFN-? or Toll-like receptors. Macrophages which are infected with parasites depend upon IFN-? and TNF for activation .

In vivo ROS control L. major parasitism in mice. In one study, C57BL/6 wild-type mice (WT) and mice genetically deficient in ROS production by phagocytes (gp91^phox?/?) were infected with the parasite to study the effect of ROS in controlling the parasites, however, no direct correlation was found between ROS production and killing of parasites.