Immunostimulating Agents: What Next?

Abstract

Many chemical entities, either from natural sources or prepared by synthesis, are known to exert stimulating activities on various functions of the immune system, such as antibody production, resistance to infections, rejection of malignant cells, etc. In this review, the origin, chemical structures and main activities of several immunostimulants are described, with special emphasis on their present or potential medical usefulness. An attempt is made to envisage the future of this type of pharmacological agents, excluding however from the presentation the endogenous modulators of the immune system (cytokines), the production and activities of which are influenced by the immunostimulants themselves.

Modulation of the non-specific defence of fish by structurally conserved microbial polymers

“…Microbial polymers that stimulate the NSD include cell wall polysaccharides like fungal -1,3 glucans; bacterial lipopolysaccharides (LPS) and peptidoglycan; bacterial DNA rich in CpG-sequences; and viral double stranded RNA (Marcus, 1984;Stewart-Tull, 1988;Raetz et al, 1991;Yamamoto et al, 1992;Bohn & Bemiller, 1995;Werner & Jolles, 1996). What all of these polymers have in common are certain structural sequences that have been conserved throughout the evolution of microorganisms, but are not normal constituents of higher organisms.…”

“…For practical purposes, it is thus an important question whether the NSD of fish can be artificially up-regulated prior to or during stressful periods. A large body of evidence shows that structurally conserved microbial polymers have the ability to enhance the resistance of mammals against infection by pathogenic bacteria or viruses (Werner & Jolles, 1996) and in the last 10-15 years several groups have studied whether such compounds might be useful for enhancing disease resistance of fish (Anderson, 1992;Robertsen et al, 1994;Raa, 1996). The compounds used, the e#ects achieved and mechanisms that might be involved are the subject of this review.…”

Dietary microbial levan enhances cellular non-specific immunity and survival of common carp (Cyprinus carpio) juveniles

“…Unlike the use of vaccine/antigens that are directed against a few specific pathogens, immunomodulation directed against recognition of conserved microbial structures by use of immunostimulants acting on the non-specific defence mechanism can form an alternative therapy [15]. Though a variety of substances are known to act as immunostimulants, only a few are suitable for its use in aquaculture [16].…”

Selective Regulation of Human Immunodeficiency Virus-Infected CD4+Lymphocytes by a Synthetic Immunomodulator Leads to Potent Virus Suppression In Vitro and in hu-PBL-SCID Mice

“…For nearly 2 decades, muramyl peptides were evaluated mostly as nonspecific enhancers of host resistance against microbial infections and as vaccine adjuvants (32,73). The biological activities of these immunomodulators were also linked to their capacity to activate macrophages, and few studies have addressed the direct effects on T lymphocytes (4,63).…”