According to new research, a vaccine has been produced in genetically engineered tomato and tobacco plants, which triggers anti-SARS antibodies in mice.
Severe Acute Respiratory Syndrome (SARS) is an atypical form of pneumonia. It first appeared in November 2002 in Guangdong Province, China. SARS is now known to be caused by the SARS coronavirus (SARS-CoV), a novel coronavirus. SARS has a mortality rate of around 10%.
After the People's Republic of China suppressed news of the outbreak both internally and abroad, the disease spread rapidly, reaching neighboring Hong Kong and Vietnam in late February 2003, and then to other countries via international travellers. The last case in this outbreak occurred in June 2003. In the outbreak, SARS caused 8,069 cases of disease and 775 deaths.
To date there have been no further outbreaks of SARS in the general population, but the fact that it spread so rapidly around the world has created a demand for an effective vaccine.
Dr. Hilary Koprowski and colleagues, from Thomas Jefferson University in Philadelphia, saw that findings from previous studies suggested that a protein on the virus' outer membrane, called the S protein, would be the best antigen for creating a vaccine.
The researchers also saw that using plants to produce vaccines would be inexpensive, and an oral vaccine is generally preferable to one requiring injection.
They found they were able to manipulate a tomato plant and a low-nicotine tobacco plant to express a fragment of the S protein, and when they fed mice the fruit of the tomato expressing this fragment, the animals produced SARS-specific antibodies.
The mice also produced antibodies after an injection containing a tobacco-derived fragment.
The scientists say that progress towards the goal of establishing a safe and inexpensive vaccination program needs further study with other animals.
The report can be seen in Proceedings of the National Academy of Sciences, June 21, 2005.