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Gene editing and herpes: what it is, and why it isn't a vaccine

Last updated: October 25, 2026

Gene editing tries to damage the herpes virus already hiding inside a person's nerve cells, which is a different job from a vaccine's. Every published result is against HSV-1: large reductions of dormant virus in mice and rabbits, one study in three patients with eye disease, and one trial now enrolling. This explainer sets out what has been shown, what has not, and why this site tracks vaccines rather than gene-editing treatments.

People searching for herpes research often come across gene editing, usually under the name CRISPR. It is a real line of laboratory work, and it is not a vaccine. This page explains the difference, says what the published evidence shows so far, and explains why this site does not track gene-editing programs alongside vaccine candidates.

The short answer

A vaccine trains the immune system. Gene editing goes after the virus’s own DNA — the instruction code the virus is built from — and tries to break it.

The two approaches are aimed at different problems. Herpes simplex virus (HSV) settles permanently inside nerve cells after the first infection, in a sleeping state called latency. Standard antiviral drugs such as acyclovir block the virus while it is actively copying itself, but they have little effect on the sleeping virus and do not clear it from the body [S1]. Gene editing is one of the few approaches that tries to reach that sleeping virus directly [S1].

Two things are worth knowing before the detail. Every published result on this page is against HSV-1, the type behind most cold sores and herpes eye disease, not HSV-2, the type behind most genital herpes. And in people, the published evidence is one study in three patients with severe eye disease [S7]. One further trial is now enrolling [S9]. None of this has produced an approved treatment.

What “gene editing” means here

Gene editing uses a protein that cuts DNA at a chosen place. Researchers working on HSV have used two main kinds [S1]:

• A meganuclease, also called a homing endonuclease: a single small protein that both finds its target sequence and cuts it. Making one that recognises a new sequence takes substantial protein engineering [S1].
• CRISPR-Cas9: a cutting protein (Cas9) steered to its target by a short piece of RNA called a guide RNA, which matches about 20 letters of the target DNA. Changing the guide RNA re-aims the system, which is why CRISPR is easier to retarget than a meganuclease [S1].

A cut in the wrong place — in the patient’s own DNA rather than the virus’s — is called an off-target effect, and it is one of the main things these studies measure.

Either way, the cutting machinery has to get inside the cells where the virus lives. In the HSV work it is usually carried there by an adeno-associated virus (AAV) vector — a harmless virus shell emptied of its own genes and used as a delivery van [S3]. Some of the eye work instead uses lentiviral particles, shells built from an unrelated virus, to carry the Cas9 instructions into the cornea as mRNA [S6]; the product given to patients is an mRNA preparation injected into the cornea [S7][S8].

Why herpes is a target for this

After the first infection, HSV travels up sensory nerves and goes dormant in the ganglia, the clusters of nerve-cell bodies near the spine and skull. A dormant virus makes little or no protein, so there is almost nothing for the immune system or an antiviral drug to act on [S1]. That reservoir is the reason infection is lifelong and outbreaks keep returning.

This is also the reason gene editing is not a substitute for a vaccine, and a vaccine is not a substitute for gene editing. A vaccine is aimed mainly at people who are not yet infected, or at reducing outbreaks in people who are. Gene editing, as it is being studied, is aimed at virus that is already there. Our explainer on prophylactic versus therapeutic vaccines covers the same split on the vaccine side.

What the animal studies show

These are results in animals. Mice and rabbits are not people, and HSV research has a long record of animal results that did not carry over — a point our explainer on why HSV is hard to vaccinate against sets out in more detail.

The first demonstration that an engineered cutting protein could reach dormant HSV in a living animal and mutate it was published in 2016, in latently infected mice [S2]. Later work from the same group reported removing more than 90% of the dormant virus from one set of ganglia in mice. In that study meganucleases worked and CRISPR-Cas9 did not [S3].

A 2024 paper from the same group reported the largest reductions it has published: 90% or more of the latent HSV-1 DNA eliminated in mouse models of mouth-and-face infection, and up to 97% in mouse models of genital infection [S4]. Two caveats sit on those numbers.

The first is which nerve-cell cluster. The 90% figure is for the superior cervical ganglia. In the trigeminal ganglia — the cluster that matters for cold sores and eye disease in people — the same group reports it typically removes about half to two-thirds of the virus, not 90% [S4].

The second is shedding, meaning virus appearing at the surface where it can be passed on. Treated mice shed less, but mice barely reactivate on their own, so the researchers had to wake the virus with a drug first [S4]. Individual experiments did not reach statistical significance on their own, and the significant result comes from pooling every experiment in the paper [S4]. The shedding work was done in female mice [S4].

The authors describe their aim as eliminating the latent virus, and call their approach “potentially curative” [S4]. That is their phrase for the goal, not a result in people.

The same paper is also where the main safety signals appear. The authors report liver toxicity at high doses, and faint signs of nerve-cell injury under the microscope without any visible neurological problems in the animals. Using a single AAV type, a lower dose, and a switch that turns the editing protein on only in nerve cells each improved tolerability while keeping the effect [S4]. They also note that this kind of nerve-cell injury after AAV treatment has been described in several animal species and in at least two human trial participants examined after death, in gene-therapy work generally rather than HSV work [S4].

Two other groups have worked on HSV-1 eye disease. One reported that Cas9 delivered into mouse corneas blocked HSV-1 replication and the eye disease it causes, reached the trigeminal ganglion — the nerve-cell cluster at the base of the skull serving the face and eye — and worked in human corneas in the laboratory with no off-target effects found by whole-genome sequencing [S6].

The other worked in rabbits with latent HSV-1 eye infection [S5]. Scratching the surface of the cornea and applying an all-in-one AAV vector carrying CRISPR-Cas9 reduced viral shedding by more than half. Giving an AAV9 vector intravenously — into a vein — instead stopped detectable shedding in 92% of treated eyes [S5].

What has happened in people

One published study. In 2023, researchers in China reported injecting a single dose of an HSV-1-targeting CRISPR preparation into the cornea of three patients with severe, treatment-resistant herpetic stromal keratitis [S7], which is scarring inflammation deep in the cornea caused by HSV-1 and a leading infectious cause of blindness [S6]. The injection was given during a corneal transplant. Over an average of 18 months the authors found no detectable off-target cutting and no systemic side effects, and HSV-1 stayed undetectable [S7]. They describe the result as preliminary evidence of acceptable safety [S7].

Three patients cannot show whether a treatment works. There was no comparison group and everyone knew who had been treated [S7]. Each patient also received a new cornea during the same operation, which on its own removes infected tissue. The registry record for that study lists it as completed, with three participants and no phase assigned, and no results posted to the registry [S8].

A larger trial of the same product, BD111, is now under way. Its registry record describes a phase 2a trial — an early test for safety and a first look at whether the treatment does anything — in adults with HSV-1 stromal keratitis. It aims to enrol about 40 people, started on 28 April 2025, and is listed as recruiting. Participants are assigned at random to BD111 plus the standard three-drug treatment, or to a dummy injection plus the same three drugs [S9].

Two details in that record are worth stating carefully. Its official title calls the trial multicentre, while the record lists a single study location, in Wenzhou, China. The title also says single-blind, while the record’s own design field says four groups are kept unaware of who received what [S9]. The registry gives an estimated primary completion date of December 2026; that is an estimate on a record last updated on 18 May 2025, not a result [S9].

A trial existing is not the same as a trial succeeding. As of this page’s date, no efficacy results from that trial have been published or posted.

What is still unknown

• Whether it works in people. No completed, controlled trial has reported that gene editing reduces herpes outbreaks or transmission in people.
• HSV-2 and genital herpes. This is the largest gap. Every result above is against HSV-1. The mouse “genital infection” experiments were done by infecting mice vaginally with HSV-1, not HSV-2, and the authors say plainly that the cutting proteins they used target HSV-1 sequences that “are not well conserved in HSV-2” [S4]. No published gene-editing result exists against latent HSV-2, in an animal or a person.
• Reach. HSV hides in many separate clusters of nerve cells. Removing most of the virus from some ganglia in a mouse is not the same as reaching enough of it in a person for outbreaks to stop. The 2020 paper makes this point itself: the delivery vehicles and the virus are spread unevenly among nerve cell types, so better delivery would be needed for more complete removal [S3].
• Safety at the doses needed. The liver toxicity and the microscopic signs of nerve injury reported in mice at high doses are the open question that dose and delivery changes are meant to answer [S4].
• Off-target cutting over time. The studies above looked for unintended cuts and did not find them [S6][S7], but they were small and short.

Why this site tracks vaccines, not gene editing

This site covers HSV vaccines: how each candidate is doing, backed by registry records and published papers. Gene editing is a treatment aimed at virus already in the body, not a vaccine, so it sits outside what we track. Our methodology sets out that boundary, along with the other non-vaccine approaches it covers.

We have written this page because the question comes up constantly, and because the honest answer is specific: real laboratory progress, large reductions of latent HSV-1 in mice and rabbits, one three-patient study and one enrolling trial in people, nothing yet against HSV-2, and no approved treatment. We have put no date on any of it, because no public record supports one.