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Figure 1. Vaginal homeostasis vs. dysbiosis. Glycobiology is key to understanding interactions within the vaginal microbiome since many elements encompassing the microbiota and the host are glycosylated or bind glycans. The immune state is affected^[90] in different ways between a healthy state of homeostasis (A) and a disease state of symbiosis, which in turn contributes to either health (A) or dysbiosis (B) characterized by distinct commensals and pathogens interacting with host factors and cells. (A) Homeostasis. Lactobacillus crispatus is deemed to be the preferred vaginal microbiome commensal when dominant due to its high lactic acid production, from glycogen degradation, resulting in beneficial low pH. (B) Dysbiosis. This condition does not have the beneficial protective effects of low pH. Presented by multi-species, non-Lactobacillus flora, including pathogens such as Prevotella and Gardnerella. Virulence factors are produced such as: biofilms, hydrolytic enzymes (e.g., sialidases), and cytolysins which can lead to the breakdown of mucins and epithelial cells, disruption of the homeostatic glycome, and immune response (e.g., deglycosylation of immunoglobulins and activation of immune factors). These conditions in turn promote the rise of undesirable members of the microbiome, such as viruses, yeast, and even protozoa^[6,91]. Figure created using BioRender.com.