Novel TLR4-Activating Vaccine Adjuvant Enhances the Production of Enterococcus faecium-binding Antibodies

Vaccines are one of the greatest
achievements of modern medicine.
Due to their safer profile, the latest investigations usually focus
on subunit vaccines. However, the active component often needs to
be coupled with an adjuvant to be effective and properly trigger an
immune response. We are developing a new synthetic monosaccharide-based
TLR4 agonist, such as glucosamine-derived compounds FP18 and FP20, as a potential vaccine adjuvant. In this
study, we present a new FP20 derivative, FP20Hmp, with a hydroxylated ester linked to the glucosamine core. We show
that the modification introduced improves the activity of the adjuvant
and its solubility. This study presents the synthesis of FP20Hmp, its in vitro characterization, and in
vivo activity while coupled with the ovalbumin antigen or
in formulation with an enterococcal antigen. We show that FP20Hmp enables increased production of antigen-specific antibodies that
bind to the whole bacterium.