Researchers develop virus-like particle to edit proteins causing inherited eye diseases

ENVLPE takes a clustered regularly interspaced short palindromic repeats (CRISPR) gene editing approach. Image credit: AdobeStock/Daniel/AI

A National Eye Institute-funded research team has developed a virus-like particle (VLP) to enhance how specialists edit proteins causing inherited diseases. The VLP system, engineered nucleocytosolic vehicle for loading of programmable editors (ENVLPE), was found to have corrected 2 mutations associated with blindness.¹ The system takes a clustered regularly interspaced short palindromic repeats (CRISPR) gene editing approach, which is also being used to treat other inherited diseases, including cystic fibrosis and familial hypercholesterolemia, according to a news release.

The research team consists of University of California Irvine School of Medicine research in collaboration with a team from the Helmholtz Munich research institute in Germany.¹

“We have previously demonstrated VLPs that can efficiently deliver CRISPR prime editors to restore sight in live mice,” said Samuel Du, an NEI research fellow working in the lab of Krzysztof Palczewski, PhD, at the University of California Irvine School of Medicine.

The previous work with VLPs references research conducted by the UC Irvine School of Medicine in collaboration with the Broad Institute of MIT and Harvard, which directly fused CRISPR components to VLP structural components. The team had developed a highly efficient delivery system for therapeutic CRISPR/Cas9 prime editor (PE) constructs called PE-engineered virus-like particles (eVLPs).¹ A news release² stated that the delivery of the CRISPR/Cas 9 editing constructs was proving to be the biggest challenge in moving gene editing into the clinic.

The partnering team at Helmholtz Munich then discovered an alternative mechanism for recruiting and packaging CRISPR prime editors into VLPs.¹

“By systematically analyzing VLP methods for the delivery of gene editing RNP complexes, we identified 3 interrelated bottlenecks that limit their performance,” the researchers wrote in the published study.³ “First, the formation of guide RNA/Cas complexes in the nucleus is spatially separated from the budding process at the plasma membrane. Second, unbound guide RNAs, especially pegRNAs, are the least stable RNP components in the packaging cells. Third, the transport and packaging of RNP editors via protein fusions of an adapter to Gag protein instead of RNA aptamers limits the efficiency and modularity of the resulting VLPs.”

“Utilizing RNA-protein interactions, the VLPs underwent several rounds of modification and optimization to create highly efficient VLPs,” said Palczewski in the release. “A key advantage of this system is that it is highly modular — any CRISPR system can easily be put into the ENVLPE VLPs with no complicated cloning and optimization of cleavage patterns like with other VLP systems.”

The Helmholtz team has tested the ENVLPE VLPs in multiple CRISPR paradigms, including gene knockout, homology-directed repair, base editing, and CRISPR-activation assays. These VLPs were also applied in multiple cell types, such as workhouse tissue culture lines, brain organoids, and primary T cells.¹

“In summary, our characterization and application of the ENVLPE mechanism revealed that an optimized (pe)gRNA-mediated VLP packaging of gene editors as RNPs substantially improves editing efficacy per particle,” the study authors stated.³ “This makes ENVLPE a potent delivery tool for base- and prime-editing, as well as HDR-based insertions or transactivation.”

References

1. NEI-funded researchers “push the ENVLPE” with new virus-like particle to fix mutations causing blindness. News release. National Institutes of Health, National Eye Institute. April 9, 2025. Accessed April 14, 2025. https://www.nei.nih.gov/about/news-and-events/news/nei-funded-researchers-push-envlpe-new-virus-particle-fix-mutations-causing-blindness

2. Researchers engineer in vivo delivery system for prime editing, partially restoring vision in mice. News release. University of California Irvine School of Medicine. March 13, 2024. Accessed April 16, 2025. https://medschool.uci.edu/news/researchers-engineer-vivo-delivery-system-prime-editing-partially-restoring-vision-mice

3. Geilenkeuser J, Armbrust N, Steinmaßl E, et al. Engineered nucleocytosolic vehicles for loading of programmable editors. Cell. 2025. doi:10.1016/j.cell.2025.03.015