At the present rate of progress in the immunological and parasitological sciences, it has become necessary to bring together these two branches of biological knowledge in order to get a bigger picture of the changes that occurred during the ancient battle between hosts and parasites, changes that are still happening today and will continue as long as evolution exists. To understand how immune responses are shaped by parasite molecules, developmental stages of a parasite s biology, the pathway and chronicity of infections, etc., we require the interaction of researchers with experience in several fields such as, immunology and parasitology, molecular biology and biochemistry. This book has been planned to incorporate new discoveries and concepts in immunoparasitology as well as the ever-growing areas of host-parasite relationships and cross-regulated responses among parasite development, the immune system and other host systems, such as the metabolism. It is remarkable that parasitic diseases still represent a tremendous worldwide health problem; in fact more than half of the human population is, in the course of their life, infected with some kind of parasite. Effective vaccines must offer long-term cost-effective solutions but, despite intense efforts, sufficiently efficacious and safe vaccines are as yet unavailable for many major parasites. These challenges demand a greater effort from investigators to perform more specifically delineated basic biomedical research to better understand the different pathways that parasites exploit in their hosts for survival and reproduction. Examples of areas where an impressive amount of new knowledge has been incorporated are the areas of genomics and proteomics of parasites such as Leishmania, Trypanosoma, Plasmodium, Toxoplasma and Entamoeba, among protozoan parasitic diseases. Likewise, some advances in similar topics are being developed regarding some helminthes such as Taenia and Brugia. With respect to immunity, the importance of early and differential recognition of parasites by the immune system (Innate Immunity) in order to mount the right and effective immune response as fast as possible to eliminate the invading parasite is now known. Thus, increasing highlights have been reported on pathogen recognition receptors (PRRs) on immune cells and Pathogen Associated Molecular Patterns (PAMPs) on parasites. This book includes current knowledge on the role of innate immunity, toll-like receptors, cytokines and chemokines and their respective receptors in maintaining the functional ability of the immune system to keep parasites restricted and maintain a healthy host as long as possible. Interestingly, the immune response is often not working alone when dealing with parasitic infections. In recent years, some research has focused on the interconnections of the immune system with other systems such as the neuro-endocrine, reproductive, and metabolic systems. There are several examples (such as some presented in this book), where the more integrative study of an infection, including not only the immune system but also the neuro-endocrine and metabolic systems, is necessary to fully understand resistance or susceptibility to pathogens. All the authors in this book have made invaluable contributions to the knowledge of the interaction between parasites and the immune response with great expertise, so that each chapter is an actualized and current review of a topic in which authors are leaders in the field and, of course, are directly involved in laboratory and field experimentation. Notwithstanding, I am sure there will be disagreement with other top researchers on certain issues, of course we do not expect a general agreement which rarely exists in the biological sciences, but I hope that such controversial areas will generate more intense and deep research. We all hope that this increasing interest in the multidisciplinary study of the interactions among parasites, immune responses, metabolism, molecular biology, genetics and other physiological systems in the host can produce an expanding universe of knowledge that could be translated, in few years, into benefits to humanity, especially to those individuals who are now suffering from some of these parasitic diseases. We hope that this knowledge could, in time, be used to design better and more effective vaccines, new methods of early diagnosis, better preventive measures, new rationales for drug development to fight parasitic diseases, and new individual susceptibility markers, as well as identify where immune mechanisms contribute to parasite restriction or facilitate host colonization. Finally, all we expect that new generations of young researchers get interested in these areas of knowledge, in order to contribute to fight then emerging infectious diseases which are another sign of the impact of warming climate.

The phenomena involved in infections of man and domestic animals with metazoan or protozoan parasites present formidable practical problems as well as a theoretical challenge to immunologists, molecular biologists, and evolu tionary biologists. With respect to the public health and economic problems, malaria, for example, remains a major health problem with approximately 200 million people being infected yearly and, on the basis of World Health Organiza tion estimates, more than 1 million children die each year of malaria infections (Chapter 4). This volume addresses state-of-the-art immunologic approaches to the development of vaccines for parasitic diseases (Chapter 9) and analyses of studies bearing on the antigenic characterization of protozoan and metazoan parasites (Chapters 4, 5, and 7), on investigations of the role of precise mecha nisms underlying natural resistance or non permissiveness of the host to parasitic infections (Chapters 1, 2, and 12), on induced mechanisms including the genera tion of parasite-specific T-cell lines and clones (Chapter 6), and on the generation of monoclonal antibodies (Chapters 4 and 5) to parasite antigens of distinct de velopmental stages. Great progress has been made in characterizing parasite antigens capable of inducing a protective response in the vaccinated host; further progress in this area strongly depends on biochemistry and molecular biology with the long-term goal of synthesizing such antigens chemically or producing them by means of recombinant DNA technology (Chapter 4).

Parasitic infections remain a significant cause of morbidity and mortality in the world today. Often endemic in developing countries many parasitic diseases are neglected in terms of research funding and much remains to be understood about parasites and the interactions they have with the immune system. This book examines current knowledge about immune responses to parasitic infections affecting humans, including interactions that occur during co-infections, and how immune responses may be manipulated to develop therapeutic interventions against parasitic infection. For easy reference, the most commonly studied parasites are examined in individual chapters written by investigators at the forefront of their field. An overview of the immune system, as well as introductions to protozoan and helminth parasites, is included to guide background reading. A historical perspective of the field of immunoparasitology acknowledges the contributions of investigators who have been instrumental in developing this field of research.

There are currently 3-5 million cases of leishmaniasis in the world and the prevalence is rising. The first chapter in this volume reviews the cell biology of the parasite and its transmission and survival. The second review addresses the apicomplexan protozoan parasites Theileria anulaga, T. parva and T. sergenti which globally cost agriculture over one billion US dollars annually. Current research in this area aims to produce effective, stable and cheap subunit viruses requiring only a single application and the authors predict that success will eventually be achieved with 'naked DNA' vaccines containing cytokine genes as immunopotentiators. The next review is the first in over 30 years to discuss the larva of the class Monogenea.The authors cover morphology, behaviour and structure of many examples providing a detailed reference for researchers. The penultimate chapter discusses the distribution of Schistosoma bovis and considers the reported interactions occurring between parasites and snails. The final chapter reviews one of the most serious parasitic diseases in salmonid aquaculture - sealice. In 1998 the costs due to sealice damage in Scotland alone were estimated at 15-30 million pounds. Discussion of biology and control of these ectoparasites emphasizes the need to understand the basic biology of the parasite. This volume will be essential reading for parasitologists in many branches of the subject.

The Advances in Parasitology series contains in-depth reviews on current topics of interest in contemporary parasitology. It includes medical studies on parasites of major influence, such as trypanosomiasis and scabies, and more traditional areas, such as zoology, taxonomy, and life history, which shape current thinking and applications. Series has the second highest ISI impact factor in the parasitology group! (4.818 in 2002) Contributors are international experts in the field

Dr. Paul Giacomin is a co-founder of Paragen Bio. Dr. Siracusa is the founder and president of Nemagen Discoveries. The other Topic Editors declare no competing interests with regard to the Research Topic subject.