Interaction of recombinant human lactoferrin and SARS-CoV-2 virus to heparin-protein conjugate

Abstract

The advantages of the complex of recombinant human lactoferrin (rhLF) with europium ions have been used to establish quantitative parameters of specific interaction of rhLF with immobilized heparin-protein conjugate as a model of cell-surface heparan sulfate proteoglycans. Heparin coupled through terminal formyl by reductive amination to an inert protein was adsorbed through the protein part in the wells of a polystyrene microplate. The rhLF–Eu3+ complex obtained from native rhLF contains 0.8 mol of lanthanide ion per mol of protein (40 % saturation level). Equilibrium in the heterophase binding system is established within 1 min at room temperature, and the calculated association constant of the rhLF-heparin complex is 2.1 × 107 M–1. The reversible and saturable character of binding rhLF labeled by Eu3+ at the active site to heparin was confirmed by the transition of rhLF–Eu3+ into the liquid phase when a 1000-fold molar excess of unlabeled rhLF was added to the system. Based on the affinity of rhLF for glycosaminoglycan, a blocking effect of this protein on the binding of the SARS-CoV-2 virus to the immobilized heparin-protein conjugate that imitates proteoglycan on the host cell surface was revealed. Pretreatment of the adsorbed conjugate with a solution of rhLF (10 µg per well) reduces the specific binding of 100 ng of viral particles added to the well by approximately 80 %. The presented results allow one, in particular, to evaluate the integrity of the structure and activity of rhLF as a possible substance in food supplements and pharmaceuticals and may be useful in developing combined drugs for corona virus infection.