U.S. medical scientists say they've discovered how a virus can repeatedly infect people despite a strong and long-lasting immune response.
Researchers at the Oregon Health & Science University's Vaccine and Gene Therapy Institute said their study focused on the cytomegalovirus, known as CMV, which infects up to 80 percent of the U.S. population before age 40.
"CMV is one of a few virus types that can efficiently reinfect individuals who are already persistently infected by this virus," Dr. Louis Picker, the institute's associate director, said. "When most viruses infect a host, the immune system remembers the disease and protects against reinfection," Picker said, explaining that's why vaccines made with weakened or dead viruses work against such pathogens. "This research explains how CMV is able to overcome this immune response so that reinfection occurs."
The scientists studied monkeys naturally infected with CMV and discovered reinfection can only take place when the virus is able to evade a key portion of the immune system involving T cells, which attack and kill infected cells by identifying them by the presence of certain molecules on an infected cell's surface.
The scientists discovered CMV evades those T cell systems by disrupting the molecules' ability to communicate an infection to the T cells.
The study that included Professor Klaus Frueh appears in the early online edition of the journal Science.
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