Vaccine Developed to Protect Against Cytomegalovirus
Vaccine is First to Be Proved Effective in Animal Model
CINCINNATI -- A genetically engineered vaccine developed and tested at Cincinnati Children's Hospital Medical Center is the first to be proved effective in protecting newborns, in an animal model, against cytomegalovirus (CMV), the most common congenital viral infection in the United States.
The study was presented at the annual meeting of the Pediatric Academic Societies in Baltimore.
The prestigious Institute of Medicine has identified CMV as one of only seven diseases for which vaccine development should be given the highest level priority for research and development. In fact, CMV infection is the second most common identified cause of mental retardation in newborns, after Down syndrome. A mother can pass CMV on to her newborn baby, even if she does not feel ill herself. Unfortunately, the infant, when infected in the womb, can suffer serious consequences. CMV infection is also a leading cause of deafness in children.
Mark Schleiss, MD, a physician in the Division of Infectious Diseases at Cincinnati Children's and lead author of the study, discovered a key gene in guinea pig CMV in the mid-1990s that became the basis for development of the current vaccine. The guinea pig is the most relevant, preclinical screening model for evaluating CMV vaccines, since CMV can cross to the newborn animal, just as it does in newborn infants.
In the current study, the cloned, recombinant (genetically engineered to be totally pure) vaccine proved to be effective in the guinea pig model in preventing transmission of CMV from mothers to their offspring.
"Although the CMV virus contains hundreds of genes, the most important ones to target for vaccine development are those that encode, or carry the genetic blueprint, for the outer protein coat of the virus, the region called the 'viral envelope'" says Dr. Schleiss. "These so-called glycoproteins surround and protect the virus. The vaccine we developed and tested targets the glycoprotein B, and we found it effective in protecting the newborn. This makes the protein an attractive candidate for human testing for this major public health problem."
The study is also important in demonstrating that targeting a single protein can confer protection to the fetus, according to Dr. Schleiss. And, it demonstrates the importance of proper choice of adjuvant, a product added to many vaccines to boost immune response, he says.
Up to 40,000 infants in the United States are born each year with CMV. If the mother has immunity to CMV, her baby may not seem ill at birth, but could later develop deafness and mental retardation. If women become infected with the virus for the first time while they are pregnant, their babies are born ill -- possibly with failure of any organ. "They are almost always neurologically abnormal," says Dr. Schleiss. "They are born with small heads and small brains, probably because the virus interferes with brain development."
The dangers of CMV are compounded because women can be exposed to the virus without knowing it, and only when the baby is born does it become clear what has happened. The virus is most often transmitted through bodily fluids, and women are often exposed to it by contact with children, particularly in day care centers. These centers are "large reservoirs for infection," says Dr. Schleiss. "If a woman has children attending a day care center or works in any job where she is in frequent contact with young children, she's at high risk to acquire CMV infection, and this can become a concern for future pregnancies."
Contact Information
Jim Feuer,
jfeuer@chmcc.org, 513-636-4656
