Antiviral potential of chemokines

In the past few years, a large number of new chemokines (chemotactic cytokines) and chemokine receptors have been discovered. The growth in knowledge about these molecules has been achieved largely through advances in bioinformatics and the expansion of expression sequence tag (EST) databases. It is now clear that chemokines are crucial in controlling both the development and functioning of leukocytes and that their role is not restricted to cell attraction, as originally assumed. In particular, recent findings provide strong support for the idea that chemokines and their receptors are especially important in the control of viral infection and replication. Thus, specific chemokines are now known to enhance the cytotoxic activity of infected cells, thus inhibiting further virus replication. In addition, some chemokines orchestrate the recruitment of activated leukocytes to foci of infection to aid viral clearance. Viruses, in turn, have evolved various defences against chemokines. These range from the production of proteins that inhibit biological activity of the host chemokine to the hijacking of the chemokine system, whereby certain viruses utilize chemokine receptors for their entry. The latter viral defence can itself be blocked by chemokines. Altogether, these findings illustrate the central role of chemokines in many different phases of the immune response, particularly those aspects involving antiviral defence, a variety and versatility that was not fully appreciated even a few years ago.