Microbial surface mannose-rich carbohydrates

Microbial surface mannose-rich carbohydrates, often termed high-mannose glycans or mannans, are critical components of the outer surfaces of various pathogens, including viruses, bacteria, and fungi (Dommett et al., 2006, Tissue Antigens; Snarr et al., 2017, Frontiers in Immunology). These structures consist of branched mannose polymers that serve as essential Pathogen-Associated Molecular Patterns (PAMPs) for the host's innate immune system. In humans, these glycans are recognized by pattern recognition receptors (PRRs) such as Mannose-Binding Lectin (MBL) and DC-SIGN, which initiate the lectin pathway of complement activation and facilitate phagocytosis (Dommett et al., 2006). Because high-mannose structures are typically sequestered within the endoplasmic reticulum of healthy mammalian cells and are less prevalent on their surfaces, they provide a selective target for anti-infective therapies (Lusvarghi & Bewley, 2016, Chemical Reviews). Therapeutic strategies include the use of recombinant MBL to restore immune function in deficient patients and the development of carbohydrate-binding agents (CBAs) like the algal lectin Griffithsin (O'Keefe et al., 2009, PNAS). These agents work by binding to the glycan shield of viruses such as HIV or SARS-CoV-2, thereby neutralizing the pathogen and preventing cellular entry (Sanders et al., 2002, Journal of Virology). Additionally, targeting fungal mannans is a key approach in diagnosing and treating invasive fungal infections like candidiasis.

Other names

High-mannose glycansMannansMannose-containing glycoconjugatesPathogen-associated molecular patterns (PAMPs)Fungal mannans

Carbohydrate-binding agents (CBAs) and pattern recognition receptors (PRRs) bind to terminal alpha-mannose residues on the microbial surface. This interaction leads to the physical neutralization of viral particles, inhibition of viral entry into host cells, opsonization for phagocytosis, and activation of the lectin complement pathway (Dommett et al., 2006; O'Keefe et al., 2009; Sanders et al., 2002).