Wake Forest School of Medicine website—January 2013
Over the past decade, the United States has seen outbreaks of mumps and whooping cough, despite childhood immunization programs in place since the 1960s. Wake Forest School of Medicine (WFSM) researchers are trying to learn how the microbes that cause both contagious diseases evade the body’s immune system.
“The vaccines for mumps and whooping cough were developed decades ago,” said Griffith D. Parks, PhD, professor and chair of Microbiology and Immunology. “It appears the vaccines are less effective than previously thought, but the reasons for this are unclear. That’s why we study these pathogens.”
The mumps virus causes fever, aches, and swelling under the ears. Usually mild in youngsters, mumps can cause serious complications after puberty. Children get a combination vaccine for mumps, measles and rubella (MMR) after their first birthday and a booster between ages 4 and 6. However, the Centers for Disease Control and Prevention (CDC) recorded 6,584 cases in 2006 and more than 4,000 cases in 2009, mostly among college students.
Parks has studied the virus family that causes mumps for the past 25 years. Different strains, some more virulent than others, are used to make vaccines for mumps in other countries.
“We need to understand why these strains are so different and what the advantages of using one versus another may be,” Parks said. “In our laboratory, we infect cells in tissue culture dishes and watch how the virus induces an immune response and how the cells eliminate the virus.”
[Continue reading about Mumps in our Health Encyclopedia.]
Whooping cough, known medically as Bordetella pertussis, the bacteria that causes it, starts like a cold but produces coughing fits for weeks. For infants, it is often fatal. The original vaccine, whole cells of inactivated bacteria, was effective but caused high rates of fever and seizures. The government switched in the 1990s to a vaccine containing five protein components of the bacteria. Children get combination diphtheria, tetanus and pertussis (DTaP) shots, and experts recommend boosters for teens and adults every 10 years.
Since 1990, CDC records show the incidence of pertussis rising, with spikes in 2004-05 (each with more than 25,000 cases) and 2010 (27,550 cases). This year, the CDC recorded more than 34,000 cases and 16 deaths through Oct. 27, 2012. While some attribute the increase to greater awareness and more diagnoses, the lower vaccine efficacy and short-lived, vaccine-induced immunity are also considered as causes for increase in pertussis. It is also likely that the bacteria are changing.
Rajender K. Deora, PhD, associate professor of Microbiology and Immunology, notes that pertussis becomes more difficult to treat when it forms a biofilm—or community structure—in the respiratory tract. “Identifying factors and mechanisms that contribute to the biofilm state and developing drugs that prevent this is a current research priority,” he said.
Deora began studying pertussis as a postdoctoral fellow at the University of California at Los Angeles in 1998. Since joining WFSM in 2003, he has made it a focus of his lab.
“Our studies have identified a new protein that is more effective in clearing the infection in mice,” Deora said. “Confirming this effect in larger animals will be necessary before trying it with humans.”
[Read more about Whooping Cough in our Health Encyclopedia.]
A Long Battle
Parks said that although his lab is not directly pursuing a new vaccine for mumps virus, the information his studies yield would help other researchers do so in the future. Deora said a new pertussis vaccine, such as one based on his supplemental proteins, is a decade or more away.
“These are long-term problems for human health,” Parks noted. “We’re trying to understand how these germs interact with immune cells now, and if we can understand that, then we can hopefully develop better vaccines that are more potent and last longer.”