Stable mutualistic interactions between multicellular organisms and microbes are an evolutionarily conserved process with a major impact on host physiology and fitness. Humans establish such interactions with a consortium of microorganisms known as the microbiota. Despite the mutualistic nature of these interactions, some bacterial components of the human microbiota express immunogenic glycans that elicit glycan-specific antibody (Ab) responses. The ensuing circulating Abs are protective against infections by pathogens that express those glycans, as demonstrated for Plasmodium, the causative agent of malaria. Presumably, a similar protective Ab response acts against other vector-borne diseases.

Glossary

the product of Immunoglobin (Ig) genes that recognize specifically molecular structures known as epitopes, that is, antigenic determinants. These are part of a larger molecule that can trigger an Ab response (i.e., antigen). Abs are composed of a fragment antigen-binding (Fab) region that binds the epitope and a fragment crystallizable (Fc) region, which endows the Ab with effector function through the engagement of immune-based mechanisms. Different Fc regions define IgM, IgA, and IgG isotypes and subclasses of IgA (IgA1 and IgA2) or IgG (IgG1, IgG2, IgG3, and IgG4). The main function of Abs is to recognize and neutralize pathogens as well as to avoid microorganism transition into a pathobiont.

absence of germs, that is, microorganisms. Animals or other multicellular organisms can be maintained under experimental germ-free conditions to establish a causal relationship between the microbiota and a given aspect of host physiology. When colonized by a specific microorganism or group thereof, germ-free animals or other multicellular organisms are referred to as gnotobiotic. This experimental approach is often used to determine the causal relationship between a given microorganism or group of microorganisms and a given aspect of host physiology.

88 Varki A.

et al. Essentials of Glycobiology. 88 Varki A.

et al. Essentials of Glycobiology. is an evolutionary conserved biologic process defined as an ‘enzyme-catalyzed covalent attachment of a carbohydrate to a polypeptide, lipid, polynucleotide, carbohydrate, or other organic compound’ []. Glycosylation is catalyzed, in most cases, by glycosyltransferases that use specific sugar nucleotide donors as substrates to generate glycans, that is, ‘any sugar or assembly of sugars, in free form or attached to another molecule’ [].

include mutualistic interactions (i.e., commensalism) when organisms from both species benefit from their interaction, commensal interactions (i.e., commensalism) when one of the species benefits from the interaction without detriment to the other, and pathologic interaction (i.e., parasitism) where one species (i.e., the pathogen) benefits from the interaction in detriment of the other (i.e., the host). In some cases mutualistic or commensal interactions change such that they become pathologic. In that case, the organism species that benefits from this transition, in detriment of its host, is referred to as a pathobiont.

multicellular organisms establish structured interactions with dynamic communities of microorganisms, including viruses, bacteria, and fungi, collectively known as the microbiota. This interspecies relationship can range from mutualistic to commensal or pathogenic, depending on the inherent composition of the microbiota or the immune status of the host. Deregulation of host microbiota interactions impacts on host homeostasis and can have pathogenic effects.

living organisms are under a continuous selective pressure exerted by parasitic relationships so that both host and parasites coevolve to gain advantage over each other.