Maternal Antibodies Offer Protection Against Herpes in Newborns

New insight has been provided by researchers from Dartmouth College’s Geisel School of Medicine regarding the most common sexually-transmitted disease (STD) that any sexually active individual can get: herpes.

Pregnant women who have been infected by herpes simplex virus type 1 (HSV-1) in the past, “maintain active antibodies” that protect against the virus, according to the press release. Now, in a recent study published in mBio, researchers have found that mothers can pass this protection on to the nervous systems of their offspring.

Through the use of a mouse model of HSV-1 and autopsied samples of human adult and fetal tissues, the investigators found that the adult women or female mice produced antibodies against HSV-1 that could travel to their unborn offspring, and thus, prevent the “development and spread of infection during birth.” The findings suggest that the key to preventing “serious brain disease related to these conditions” in fetuses and newborns lies in immunizing pregnant women against HSV, according senior study author David A Leib, PhD, professor of microbiology and immunology at Geisel School of Medicine.

“Our results underscore the previously underappreciated role of maternal antibodies in protecting fetal and newborn nervous systems against infection,” Dr. Leib explained. “Maternal antibodies have a potent protective role in the neonatal nervous system against HSV.”

According to Dr. Leib, cold sores are not the only associated symptom of HSV-1, another is eye infections. In fact, HSV keratitis “is the most common form of infectious corneal blindness in the United States.” Those with HSV keratitis can present with symptoms ranging from eye pain and redness to blurred vision and watery discharge. HSV-1 infection can also spread to the brain and result in encephalitis. HSV-1 infections in newborns—who get the virus from their mothers—can have severe, even life-threatening consequences.

However, after conducting several laboratory experiments, the investigators discovered that antibodies against HSV-1 remain in a key site of HSV infection for a long time after active infection has since cleared: the trigeminal ganglion, which is a group of nerve cells that receive signals from the eyes and face. The researchers found that maternal antibodies can travel to the trigeminal ganglion in the fetus, and those antibodies offered complete protection to newborn mice against HSV infection.

When it comes to the implications of these findings, Dr. Leib explained, “What this tells us is that women who get pregnant who have a pre-existing herpes infection have a mature immune response to that virus that will pass those antibodies to their baby.” He continued, “If that baby should be infected during delivery, it will be protected because the mother’s antibodies get into the nervous system before birth.” However, if a woman who is already pregnant gets infected by the virus, the newborn has a 50% risk of having severe complications.

Dr. Leib added that many HSV-1 vaccines designed to protect against adult-to-adult transmission have failed when tested in clinical trials; however, no HSV-1 vaccine has been tested to protect against vertical transmission, from adult-to-child, as of yet. There are studies evaluating if any of the vaccines are able to protect against vertical transmission that are currently ongoing in Dr. Leib’s laboratory.

This finding, that maternal antibodies offer protection to infants, “hasn’t been noted before,” according to lead study author Yike Jiang, MD/PhD student at Geisel School of Medicine. He stresses that this finding is “very important for pathogens that infect newborns because there is often some kind of neurologic consequence that may impact their entire lives.”

Maternal immunization may be an effective strategy to use against other pathogens, such as Zika virus, in newborns, Dr. Leib concluded.