Griffithsin
Griffithsin, a lectin derived from red algae, binds on the surface of
various viral glycoproteins to oligosaccharides including HIV
glycoprotein 120 and SARS-CoV spike glycoprotein2. Griffithsin has low
cytotoxicity, is likely to interfere with any coronavirus spike protein
due to it is highly glycosylated nature, and may impede the role of
coronavirus spike protein. GRFT has been shown to inhibit SARS-CoV
replication and cytopathicity, as well as other coronaviridae viruses
[48] [49]. In particular, in Vero 76 cells, GRFT inhibited
various strains of SARS – infection with a low nanomolar EC50 with
limited toxicity on control cells. GRFT can bind with glycans to the
surface of the glycoprotein (S protein). A total of three GRFT molecules
are capable of binding the S with very high affinity in a dose, a lower
number compared to HIV which is presumably due to the lower number of
highglycans on the S surface. Interestingly, such an association does
not restrict the binding of SARS-CoV S glycoprotein to the human
angiotensin I conversion enzyme 2 (ACE2) host cell [49]. Griffithsin
has been studied as a gel or enema for HIV prevention in phase I trials,
but the efficacy and delivery mechanisms of spike inhibitors should be
re-evaluated for the 2019-nCoV treatment or prevention.