ΔgD-2

What it is

ΔgD-2 (sometimes written X-Vax ΔgD-2) is a genetically modified HSV-2 virus from which the glycoprotein D (gD) gene has been removed. Glycoprotein D is a protein on the virus surface that the virus needs to enter cells. Without it the virus is “single-cycle”: it can enter a cell once and make viral proteins there, but the progeny cannot infect further cells. The papers describe it as a vaccine candidate meant to prevent infection (prophylactic), and it was developed at Albert Einstein College of Medicine in the laboratories of William Jacobs and Betsy Herold.

The design differs from earlier gD protein vaccines, which aimed mainly at neutralizing antibodies (antibodies that block the virus from entering cells). The papers report that ΔgD-2 instead produces antibodies that work mainly through antibody-dependent cellular cytotoxicity, in which antibodies flag infected cells for killing by immune cells.

Where it stands

Every result published for ΔgD-2 so far is from mice. The 2020 papers report that vaccinated mice were protected against HSV-2 and HSV-1 disease in skin, vaginal and eye models. The npj Vaccines paper reports complete protection from death after HSV-2 challenge in mice already infected with HSV-1, where an adjuvanted gD protein vaccine gave no significant added protection. A 2023 paper reports that ΔgD-2 protected mice from lethal challenge at every time point out to ten months after the booster dose, while the gD protein vaccine’s protection fell off after six months. The three sources are from the Einstein group; the most recent was published in August 2023. This page found no later primary publication or announcement for this candidate.

A ClinicalTrials.gov search on 2026-10-21 for “ΔgD-2”, “deltagD-2” and “X-Vax Technology” returned no records, and the sources here do not report a regulatory filing or a human trial. We could not confirm from a primary source whether a company or an application to start human testing exists, so none is stated here.

What this does and doesn’t mean

These are animal results. Mouse studies do not show that a vaccine protects people, and the 2023 paper itself describes the human implication as a prediction. The comparison vaccine in the mouse studies is an experimental gD protein vaccine, so “better than the comparison” says nothing about how ΔgD-2 would compare with anything in people. No safety data in people exist for this candidate.