Athens, Ga. – It begins with flu-like symptoms, but within days a victim of Legionnaires’ disease may experience severe chest pain, bloody coughing and even death. The illness, a severe type of pneumonia, affects only a small percentage of the population, but up to 30 percent of hospitalized cases can be fatal, and survivors often take a long time to recover.
University of Georgia researcher Vincent Starai was recently awarded $1,503,565 by the National Institutes of Health to investigate how the bacterium that causes Legionnaires’ disease, Legionella pneumophila, overcome the body’s defenses. Starai is an assistant professor who holds a joint appointment with the departments of microbiology in the Franklin College of Arts and Sciences and infectious diseases in the College of Veterinary Medicine.
Between 8,000 and 18,000 people are hospitalized in the U.S. with Legionnaires’ disease each year, according to the Centers for Disease Control and Prevention. The bacteria exist naturally in the environment but proliferate in still, warm water in poorly maintained ventilation and water systems such as cooling towers, hotel shower heads, hot tubs, and decorative fountains. It is transmitted when humans inhale mist, steam or other fine droplets from systems where the Legionella bacteria grow in concentrated numbers. It is not transmitted from person to person.
Bacteria enter the lungs and are attacked by phagocytes, the white blood cells that fight infection. Normally phagocytes eat foreign particles, engulfing and breaking them into smaller fragments within a specialized compartment called the lysosome, but Legionella bacteria somehow block this process. Instead of fusing with the lysosome and disintegrating, the pathogen survives as a whole entity inside the phagocyte. The microbe then multiplies and reproduces inside the larger host cell. When the phagocyte finally dies, it releases a batch of new Legionella microbes ready to infect more phagocytes.
Over the next five years, Starai will look at proteins secreted by Legionella that prevent the host cell’s internal membranes from fusing with the lysosome. The fusion of these membranes is an essential step in the degradation of invading microbes.
“Legionella pneumophila produces and secretes a number of proteins that alter or inhibit membrane fusion,” said Starai. “Our goals are to study the mechanisms through which the bacteria alter the host cell environment.”
Starai has already determined that one particular Legionella protein, LegC3, directly interferes with the fusion of membranes. Under the NIH grant, his team will identify where LegC3 binds inside the phagocyte host cells, and how the protein manipulates host cell membrane fusion processes. The researcher will also identify the function of several other proteins produced by the bacteria and ascertain what role they play in the bacteria’s survival.
The findings could shed light on how other microbes overcome the body’s defense mechanisms, and point to new antibacterial remedies. The information will also provide models for studying other diseases.
The research is funded under NIH project number 1R01AI100913-01A1.
Franklin College of Arts and Sciences
The Franklin College of Arts and Sciences, founded in 1801, is the oldest and largest college at the University of Georgia, comprising 30 departments in five divisions: Fine Arts, Social Sciences, Biological Sciences, Physical and Mathematical Sciences, and the Humanities. The Franklin College offers 76 graduate degrees and certificates in 42 fields of study. For more information, see http://www.franklin.uga.edu.
UGA College of Veterinary Medicine
The UGA College of Veterinary Medicine, founded in 1946, is dedicated to training future veterinarians, conducting research related to animal and human diseases and providing veterinary services for animals and their owners. The college enrolls 102 students each fall out of more than 800 who apply. For more information, see http://www.vet.uga.edu.