PREFACE [Hot topic: Molecules of Infectious Agents as Immunomodulatory Drugs (Guest Editor: William Harnett)]

Molecules of Infectious Agents as Immunomodulatory Drugs The continuous need to control infectious agents has invariably led to the application of emerging new biological disciplines and / or methodologies to their study. Particularly pertinent, advances in immunology and molecular biology during the first decades of the latter half of the twentieth century resulted in their application to research on infectious agents during the later decades. A consequence of this is that information is now available on the structure and function of a great deal of molecules derived from a wide variety of pathogens. The perceived benefit of this was that such information could be utilised to develop novel control tools for infectious agents, in particular vaccines and drugs. However the realisation that the function of some pathogen-derived products is to aid their survival by modulating immune responses of the infected host, allied to increasing awareness that many human illnesses are associated with an aberrant immune response, has recently led to the emergence of a new concept. This concept is that molecules derived from infectious agents rather than being detrimental to man, may actually benefit him. This special edition of Current Topics in Medicinal Chemistry is thus timely and brings together articles from a number of researchers who have recently began working in this new area. The molecules under study are derived from many sources including viruses, bacteria, parasites and even (although not officially an infectious agent !), a marine sponge. They have been investigated with respect to how they interact with the various cells of the immune system and a recurring theme is the induction of a polarised immune response, which is broadly anti-inflammatory in nature. Such a response, mediated by, for example, Th-2 or T-regulatory lymphocytes producing cytokines such as IL-4, IL-10 or TGF-beta, can be predicted to be of value in preventing or ameliorating pro-inflammatory diseases and this is indeed demonstrated in various models of such diseases including arthritis, diabetes, colitis and allergy. There is thus great hope that such molecules (or derivatives of them) will ultimately find use as drugs in the treatment of human disease. In retrospect it is perhaps not surprising that molecules of infectious agents may find employment as immunomodulatory drugs. During the last few decades there has been an explosive increase in the West, of allergic and autoimmune disease. Scientists and clinicians have struggled to explain this worrying situation but recently there has been emerging support for the idea that it may reflect improved hygiene resulting in lack of exposure to childhood pathogens that normally “prime” the immune system. Whether this theory - the “Hygiene Hypothesis” will hold up remains to be seen but what is certain, is that this new field of using pathogen products as drugs is likely to expand rapidly. The reason for this is the huge amount of data emerging from genome sequencing studies. More and more infectious agents are being exposed to this procedure and hence it is surely likely that more and more immunomodulators will be discovered.