An experimental mRNA vaccine from US drugmaker Moderna has shown promise against human cytomegalovirus (CMV), a common virus that can infect babies during pregnancy.
While the virus rarely causes serious illness in healthy adults, it can cause birth defects and brain damage in newborns infected in utero and fatal infections in immunocompromised adults.
Although healthy adults are largely asymptomatic, one in 200 newborns worldwide becomes infected with CMV during the mother’s pregnancy.
“It is the most common congenital infection worldwide,” said Dr. Sallie Permar, chair of the Department of Pediatrics, and Nancy C. Paduano, professor of Pediatrics at Weill Cornell Medicine.
The study, published in The Journal of Infectious Diseases, provided evidence that the new mRNA vaccine candidate can protect adults against CMV.
Therefore, it could potentially prevent women from transmitting the harmful infection to their babies during pregnancy.
The new mRNA vaccine elicited responses that were better at preventing the CMV virus from infecting the epithelial cells that line the mouth and nose and provide the first line of defense against viral infection, compared to a previously moderately successful vaccine candidate called gB. /MF59, from Sanofi and Novartis, revealed the study conducted by the Weill Cornell Medicine team at Cornell University.
The mRNA vaccine was also more effective at activating the immune system to destroy CMV-infected cells.
“We learned that the newer vaccine has the potential to be more effective than an earlier CMV vaccine candidate because some of the functional immune responses it elicits are larger in magnitude,” Permar said.
The team used data and patient samples from the Phase 2 gB/MF59 trial in adolescent girls as a benchmark to evaluate the new mRNA-based vaccine.
Moderna used mRNA technology for the CMV vaccine and added a second target (a five-unit protein complex that allows the virus to infect the epithelial cells that line the nose and mouth) in addition to the B glycoprotein used by Sanofi and Novartis.
In the study, Permar and his team compared the immune responses of people vaccinated with gB/MF59 in the Phase 2 trial with those immunized with Moderna’s mRNA-based CMV vaccine in a Phase 1 clinical trial that ended in 2020.
Specifically, the team compared immune responses in people who were protected against CMV infection after receiving the older vaccine.
The Moderna vaccine has moved into the first Phase 3 clinical study for a CMV vaccine candidate, which will help determine whether these differences in immune responses will lead to stronger protection against CMV.
“After more than 50 years of research, we are closer than ever to having a licensed CMV vaccine,” Permar said.
“The new mRNA platform has a lot of potential.”