Antiviral Actions of Polyphosphates against SARS-CoV-2 Variants Visualized with Super-resolution Microscopy

The global spread of COVID-19 with its relatively high mortality rate presents a current challenge to medical researchers to develop therapeutic strategies.

Long-chain, inorganic polyphosphates are chains of inorganic phosphate units. These are found in many cells in our blood and are cytoprotective with antiviral activities, including against HIV-1 infection.

We spoke with Dr. Massimo Zollo and his collaborator, Dr. Veronica Ferrucci, of the University Federico II and CEINGE Biotecnologie Avanzate, Italy, about their recent publication investigating the potential activities of phosphates against SARS-CoV-2 infection. Part of their investigations used the ZEISS Elyra 7 super-resolution microscope system.

Dr. Ferrucci and Dr. Zollo’s recent publication in Science Signaling which used ZEISS Elyra 7.

Please introduce yourselves and tell us about your laboratory.

I, Dr. Zollo, am a Full Professor of Genetics at the University Federico II, as well as a Principal Investigator at CEINGE, which is a center of excellence in Advance Biotechnology in Italy. Since March 2020, I also became the Scientific Coordinator of the Task-Force COVID-19 CEINGE which is funded by Regione Campania. I apply my expertise in Functional Genomics in both teaching and to applied research in brain development disorders, cancer and gene/RNA therapeutics.

My collaborator, Dr. Veronica Ferrucci, is a researcher in genetics at the University Federico II.

Our research team focuses on human molecular genetics discoveries including gene identification of inherited brain neurodevelopmental diseases and identification of somatic mutations responsible for tumorigenesis and metastasis in pediatric brain tumors.

With the emergence of Sars-Cov-2, the laboratory is now carrying out studies to identify (a) new rapid patterns of virus detection, (b) genetic studies to identify the role of disease-related genes in asymptomatic cases and (c) functional studies to identify the mechanisms of new anti-viral drugs that inhibit the entry and replication of the Sars-Cov-2 virus in primary human cells.

What did you present in your recent publication?

In our article in Science Signaling, we describe for the first time the role of polyphosphates (P120) to enhance protein degradation of two crucial component of the Sars-Cov-2 infection (ACE2 and RpRd proteins).

Both are key proteins which influence the early and middle phases of Sars-Cov-2 infection.

Within the manuscript we prove that these effects ameliorate the cytokine storm and negatively influence virus replication within infected cells in vitro.

Immunofluorescence (IF) staining with antibodies against ACE2 protein (red) and viral nucleoprotein (green). Vero E6 cells were infected with SARS-CoV-2 D particles 0.2 MOI/ cell for 72 hours. The SIM image was acquired with Elyra 7 and processed with Zeiss ZEN software (blue edition). Courtesy M. Zollo, CIENGE, Italy

Vero E6 cells were infected with SARS-CoV-2 Alpha, Beta and Delta virus particles and stained for ACE2 protein (red) and viral nucleoprotein (green). Image acquired with ZEISS Elyra 7 super-resolution system.

One surprising finding was the use of a nano-spray formula used in the Biosafety Level 3 (BLS3) studies which was able to impair virus replication in infected cells by several Sars-Cov-2 variants. These results put in frame a model that show the action of PolyP120 is independent of the virus burden mutation of any variants, with great therapeutic values.

How you use super-resolution microscopy in your publication?

Dr. Ferrucci performed the microscopy for this paper. Super-resolution microscopy using ZEISS Elyra 7 turned out to be a powerful tool that allowed us to visualize SARS-CoV-2 viral proteins (through immunofluorescence) and/or RNA (via HuluFISH) to be detected in specific cellular compartments, such as membrane or cytosol. These data allowed us to monitor the antiviral actions of polyphosphates against SARS-CoV-2 variants by using human infected-cells.

Where do you see this research going next?

At this time, we have three important efforts running.

The first is to confirm the results in animals. A pilot project using an aerosol formula of PolyP120 to treat K18-ACE2 transgenic mice previously infected with Sars-Cov-2 to verify its efficacy in vivo is showing promising results. This work is being done with a collaborator in Marseille, France.

Additionally, we are working to find additional targets at a cellular level which might be of importance to the mechanism of action.

Finally, we are producing cGMP PolyP120 particles for human Sars-Cov-2 patients Phase 1 and 2 trials, which will define the minimal dose able to impair virus replication in humans.

We are ready for all these efforts with collaborators and alliances between our University Federico II and the University of Mainz in Germany, collaborators in Seoul, South Korea and finally in the USA.

At this time, new industrial partners are welcome to us on this fascinating topics to fight the COVID-19 pandemic.

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