Manipulation of iron to determine survival: competition between host and pathogen.

Iron is an essential nutrient that can determine cellular survival. Many organisms have evolved sophisticated mechanisms for iron uptake and transport to support their growth. The dual dependence on iron of both the host and invading pathogen initiates a competition for this nutrient following infection. Microorganisms have developed various strategies to acquire iron from the host. These are counter-balanced by an iron-withholding strategy that the host deploys as part of its defense system. This strategy, involving many iron-regulatory proteins, mediates iron depletion at the mucosal surfaces, in the extracellular environment, and within the cells. Iron is sequestered into storage by the host in order to deprive the pathogens of this factor and to prevent their proliferation. This system can be compromised. In particular, new evidence is emerging that suggests that viruses are able to specifically target and regulate proteins involved in iron homeostasis. This review focuses on the procedures employed by the host and viruses to regulate iron as a means of defense and survival, respectively.