In France, researchers at a biotech company named Affilogic have engineered inhalable alternative protein scaffolds, called Nanofitins, that have demonstrated the ability to neutralize the SARS-CoV-2 virus in both in vitro and in vivo models.
Nanofitins, derived from a protein found in a hyperthermophilic archaeal microorganism found in hot springs – Sulfolobus acidocaldarius – are small binding proteins that can be used for a variety of applications, including research, diagnostics, and therapeutics. They work by binding to target molecular protein markers with high affinity and specificity, thereby inhibiting the protein’s function and, in the case of SARS-CoV-2, reducing viral load. Researchers use molecular biology techniques to randomize surface residues of S. acidocaldarius, generating libraries of Nanofitins from which binders can be selected depending on the targeted protein of choice. In the study completed by Affilogic, the isolation and sequencing of 95 Nanofitin clones led to the selection of 31 unique Nanofitins that were compared for their ability to bind the SARS-CoV-2 spike protein either at subunit 1 (S1) or the receptor binding domain (RBD). This binding would block the interaction between the spike protein and host receptor angiotensin-converting enzyme 2 (ACE2) preventing viral entry. They found that three of the Nanofitin molecules targeting the RBD of the spike protein were capable of neutralizing RBD-ACE2 binding and highly potent against the ancestral SARS-CoV-2 viral particle but ineffective in neutralizing the Omicron variant. However, using the same approach, the group was able to generate a new highly potent molecule against the Omicron variant in approximately 100 days. This highlights the ability of this approach to engineer viable therapeutic solutions to address emerging infectious diseases within a constrained time frame. Furthermore, the fusion of multiple neutralizing Nanofitin molecules can be used to create a single, more powerful molecule that can simultaneously block several regions of the virus and potentially maintain blockade efficiency in the case of ongoing viral mutation.
Given that Nanofitins are derived from a microorganism found initially in hot springs, other benefits to using these protein scaffolds in treating SARS-CoV-2 or other pathogens, lie in their intrinsic high stability to chemical and physical stresses. Current treatments for SARS-CoV-2, such as biologic antibodies, require intravenous administration in high doses with poor lung distribution, resulting in increased costs and a delay in reaching therapeutic concentrations at target sites. Antibody-based inhaled treatments have been restricted due to the poor structural and functional stability of these molecules during the nebulization process. The researchers at Affilogic have shown that anti-spike Nanofitin fully retains functionality and is stable during nebulization. Considering the ease of high-yield production of Nanofitins in bacteria, there is potential for increased bioavailability of noninvasive therapy within lung tissue, preventing and clearing early infections for less cost.
The innovative engineering of inhalable Nanofitins has demonstrated remarkable potential for developing an effective, fast-tracked, low-cost, and noninvasive treatment for respiratory infections. The work conducted by the researchers at Affilogic offers a promising avenue in the fight against the SARS-CoV-2 virus and other emerging infectious diseases.
Resources
1. Viollet S, Enouf E, Picot J, et. al. Inhalable Nanofitin demonstrates high neutralization of SARS-CoV-2 virus via direct application in respiratory tract. Mol Ther. 2023;0(0). doi:10.1016/j.ymthe.2023.08.010
Alexandra is a 4th year medical student at the University of Texas Medical Branch John Sealy School of Medicine