A snort of a new nasal-spray vaccine could soon keep severe acute respiratory syndrome (SARS) at bay. The new vaccine, a hybrid of SARS and a human respiratory virus, prevented infection in monkeys and could soon lead to a new nasal spray in people.
Since SARS emerged in China in 2002, the virus has infected 8000 people, causing pneumonia in many of them and killing 774. The epidemic was controlled in 2003, and health officials have contained recent outbreaks, including an outbreak in China in April, by isolating patients. But the disease still lurks, and new strains could emerge and launch another epidemic, says virologist Peter Collins of the National Institute of Allergy and Infectious Diseases.
No SARS vaccine has proven its mettle yet in clinical trials, but researchers have developed several prototypes, including a dead SARS virus and a DNA vaccine, both of which have to be injected. Since Collins's lab makes genetically engineered nasal-spray vaccines against childhood respiratory diseases and SARS is also a respiratory virus, "it seemed natural," Collins says, to make a hybrid vaccine virus strain to ward off SARS.
The researchers spliced the gene for the SARS spike protein, which sits on the surface of the virus and enables it to invade human cells, into a weakened variant of the human parainfluenza virus 3. That strain was designed as a nasal-spray vaccine to protect children against pneumonia. After growing and isolating the hybrid virus, they administered it to a group of African green monkeys. A month later, the researchers infected each monkey with SARS. Then they swabbed noses and throats each day and tested the material. A group of sham-vaccinated green monkeys remained infected with SARS for up to 8 days, while the vaccinated animals showed no sign of infection, according to results to be published Saturday in The Lancet. Because the parainfluenza vaccine strain has already tested safe in a clinical trial, the hybrid vaccine is ready for clinical tests in children and, with modifications, for adults, Collins says.
"It's very clever work," says mucosal immunologist Ruth Foxwell of the University of Canberra in Australia. The new vaccine could protect infants and children, although the adult immune system may neutralize the vaccine, she says. But to develop a vaccine just a year after the virus was discovered "is fantastic compared to what it normally takes."