Summary by: Arooba Ahmed (CC '23)
Drs. Porotto and Moscona are applying their experience in designing inhaled antiviral peptides for respiratory viruses and now are focusing on preventing the disease and transmission. The entry step for the Sars-Cov-2 virus requires membrane fusion with the cell membrane and is mediated by glycoprotein Spike S. This has 2 domains, which are heptad repeats at the beginning and end of the protein. They must fold over onto each other and form 6 helix energetically stable bundle structures during the fusion process. This folding step is coupled with protein structural transition. In order to inhibit membrane fusion, they designed peptides that bind to transient intermediates and prevent the formation of 6 helix bundles.
They also designed a number of modifications, such as lipid conjugation & modifying the backbone sequence. These things increase the half life of peptides and work against viruses that fuse in the endosome, overall adding to efficacy. The mechanism of proposed administration has been used in Parainfluenza, Influenza, Measles, Nipah, & Ebola. When the antiviral peptides are given subcutaneously (a short needle is used to inject a drug into the tissue layer between the skin and the muscle) immediately after infection, 100% virus infection is inhibited. When given before, day of, and after infection, the viral infection was reduced as well.
They also conducted tests on inhibition of SARS mediated fusion. They completed quantitative fusion assays for the use of MER peptides to inhibit COVID-19 by asking the cells to fuse with target cells in presence or absence of MERS peptides. The MERS peptide, which is cholesterol conjugated, demonstrated very effective inhibition of SARS2. MERS peptides that were not lipid conjugated were not effective.
Next they tested the MERS peptide against live infection of both MERS and SARS. Plaque reduction assays show that treatment with cholesterol or tocopherol lipid conjugated MERS peptides resulted in very effective reduction of COVID-19.
They also synthesized new specific conjugated lipopeptides (a peptide backbone with cholesterol or tocopherol to block formation of 6 helix bundles to prevent entry, specific for Sars-Cov-2). With this, they have done fusion assays, testing the peptides against SARS fusion. The percent inhibition was extremely effective and was way better than what they needed to get efficacy in living organisms. They are also planning on using models such as organoids and live ferrets for testing.