A study led by the University of Barcelona and the Institute for Advanced Chemistry of Catalonia (IQAC-CSIC) has introduced a novel therapeutic tool capable of inhibiting the proliferation of the SARS-CoV-2 virus, which caused COVID-19. The findings open new avenues in the fight against COVID-19 and other viral diseases that currently lack medical treatments, such as the Crimean-Congo hemorrhagic fever virus (CCHFV).
Published in The Journal of Biological Chemistry, the research is spearheaded by Carlos J. Ciudad and Verónica Noé from the Faculty of Pharmacy and Food Sciences and the Institute of Nanoscience and Nanotechnology (IN2UB) at the University of Barcelona. Collaborators include Ramon Eritja and Anna Aviñó from IQAC-CSIC and the CIBER in Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), as well as researchers Miguel Chillón from the Institute of Neurosciences at the Autonomous University of Barcelona (INc-UAB) and Noemí Sevilla from the Animal Health Research Center (CISA, INIA, CSIC). The study was also supported by the 2020 La Marató de TV3 initiative, dedicated to promoting COVID-19 research.
PolyPurine Hairpins (PPRHs) to Inhibit the Virus Responsible for COVID-19
In May 2023, the World Health Organization declared that COVID-19 was no longer a global emergency. Nevertheless, SARS-CoV-2 continues to infect a significant number of people worldwide.
The new approach relies on the capacity of molecules known as PolyPurine Hairpins (PPRHs) to halt the replication of SARS-CoV-2. This is the first scientific study to demonstrate how PPRHs can act as therapeutic agents to inhibit the growth of a pathogenic virus.
PPRHs are short, simple DNA molecules—single-stranded oligonucleotides—with high affinity for specific RNA sequences. The study reveals, for the first time, how specific PPRHs, CC1-PPRH and CC3-PPRH, can block the activity of this RNA-based virus.
“Specifically, one strand of each PPRH molecule—CC1-PPRH and CC3-PPRH—binds specifically to a fragment of the virus’s RNA genome, a poly-pyrimidine sequence, through Watson-Crick bonds,” explains Professor Carlos J. Ciudad from the Department of Biochemistry and Physiology at UB.
“Notably, CC1-PPRH binds to the RNA region encoding the replicase enzyme—essential for viral replication—while CC3-PPRH targets the coding region of the Spike protein, which plays a crucial role in infecting human cells,” the researcher adds.
This therapeutic approach was validated in vivo using laboratory animal models expressing the human ACE2 receptor, in collaboration with the Animal Health Research Center (CISA, CSIC). Additional in vitro studies were conducted on Vero E6 primate cells, which use ACE2 as the entry pathway for SARS-CoV-2, by teams at the Animal Biotechnology and Gene Therapy Center (CBATEG-UAB).
“The results show that both CC1-PPRH and CC3-PPRH are highly effective in Vero E6 cells. In transgenic mice, CC1-PPRH binds specifically to the genome region coding for the replicase protein, thereby inhibiting viral replication,” reveals the expert.
From Virus Detection to Cancer Therapy
These findings pave the way for new antiviral strategies and expand the biomedical applications of PPRHs, from diagnostics to therapeutic interventions. The team previously described the use of PPRHs as a diagnostic method for detecting RNA viruses like SARS-CoV-2 (International Journal of Molecular Sciences, 2023). This methodology, faster and more effective than PCR testing, leverages the high affinity of PPRHs to capture viral RNA and produce a detection signal upon contact with patient samples. This detection method is known as TENADA (Triplex Enhanced Nucleic Acid Detection Assay).
Beyond SARS-CoV-2, the TENADA technique can also detect the influenza A virus (H1N1) and the respiratory syncytial virus (RSV), which causes respiratory illnesses. “It is also used in diagnostic applications across other biomedical fields, such as biosensors to determine the methylation status of the PAX-5 gene in cancer and to detect the gene encoding the mtLSU rRNA ribosomal subunit in Pneumocystis jirovecii, responsible for severe pneumonia,” notes the researcher.
In cancer therapy, PPRHs have successfully silenced the expression of genes associated with cancer—such as those involved in telomerase synthesis, survivin, and topoisomerase—as well as untreatable targets like K-Ras and c-Myc genes. They have also been utilized as tools for repairing point mutations in endogenous gene loci and for gene-editing techniques, including exon skipping.
Ciudad, Carlos J.; Valiuska, Simona; Rojas, José Manuel et al. «Polypurine reverse hoogsteen hairpins as a therapeutic tool for SARS-CoV-2 infection». The Journal of Biological Chemistry, octubre de 2024. DOI: 10.1016/j.jbc.2024.107884
