Avoidance, and inactivation of reactive oxygen species: novel microbial immune evasion strategies

A prominent aspect of host cell-mediated immune (CMI) reactions leading to the clearance of infections is the production of one or more reactive oxygen species (ROS) such as superoxide (O2-), hydrogen peroxide (H2O2), hydroxyl radical (OH.), and hypohalite (e.g., OC1-). These ROS are usually produced by phagocytes. A number of chemotherapeutic agents also produce ROS in the process of their curative mechanisms. In a variety of infections, these ROS constitute a formidable arsenal in the clearance of the infection. In some cases, the excess ROS could also cause tissue damage. Evidence is herewith presented that pathogenic intracellular microorganisms, in order to enhance their survival as well as effective virulence within the host, have evolved novel strategies in the nature of avoidance, or inhibition of ROS production by phagocytes, or neutralization of already produced ROS. It is advocated that more in depth studies be undertaken in these respects in order to be able to exploit these phenomena in the production of more efficacious chemotherapeutic agents and anti-pathogen vaccines.