Interactions between microbes (pathogen, symbiont or commensal) and (animal or plant) hosts include microbial recognition of host glycans, host recognition of microbial glycans resulting in either beneficial or detrimental outcomes. Irrespective of establishing either symbiotic or pathogenic interactions most microbes use host glycans as “keys” to adhere or to enter a host. Conversely, microbial glycosylated immunodominant epitopes, such as lipopolysaccharide (LPS), peptidoglycan (PGN), capsules (CPS) and exopolysaccharides (EPS) are recognized by the host innate immune system during the early stages of interaction, up- or down-regulating pathways controlling inflammation and host defence. The result of this recognition and successive elicitation can be microbial clearance, disease or symbiosis; therefore, a continuous and dynamic interplay (a molecular cross talk) exists between host and microbes in which glycans play a major role. Host-microbe interactions can be examined by the combination of biophysical, chemical and biochemical studies, at high levels of complexity, applied to key microbial molecular factors, such as EPSs, CPSs, LPSs, PGNs and other glycoconjugates that are recognized by the innate immune system of the host in the early stages of interaction.
Much of the glycans’ role in the interaction between microbe and host is still at a primitive stage and advances in understanding the function played by glycoconjugates with the factors which modulate their structure and function, will have great consequences and help the conception of new applications in biotechnology and agriculture. A prerequisite for such developments is to reach a deeper understanding of how microbial surfaces are recognized by the innate immune system of the host, and how signal transduction mechanisms induce beneficial or fatal inflammatory reactions.
In this communication I will show some examples of isolation, structure determination and elicitation and/or suppression of plant and animal innate immunity by complex microbial glycans.
