Human antibody halts SARS in hamsters.

Scientists are working feverishly to develop treatments for severe acute respiratory, syndrome (SARS), unsure of when and where that recently discovered viral infection might reappear. Several potential vaccines have progressed to the testing stage in animals (SN: 1/10/04,p. 28; 7/3/04, p. 3).

Now, researchers have demonstrated that one treatment can not only prevent infections if received in advance of exposure to the SARS virus but also ameliorate an infection already in progress. The new treatment relies on antibodies derived from human immune cells exposed to the SARS virus.

Donna Ambrosino of Massachusetts Biological Labs in Worcester and her colleagues initially produced many copies of that antibody, which they had determined could recognize the SARS virus and molecularly mark it for destruction by immune cells. Injecting these antibodies into mice before exposing them to SARS prevented the virus from replicating in the animals' lungs, the scientists found.

In further tests in hamsters, Ambrosino and her collaborators administered the virus first. A day later, before lung symptoms would normally appear, the scientists injected some of the animals with the human antibodies. Several days later, those hamsters had no symptoms and less than one-hundredth the number of virus particles in their lungs as animals not receiving antibodies had.

The speed of the antibodies' effect indicates that they are directly neutralizing virus particles, not merely revving up the immune system as a vaccine would, Ambrosino says.--B.H.