Powerful research tools that speed up vaccine development have led to the start of human tests for a preventive vaccine against the respiratory disease SARS. The disease killed hundreds of people around the world before it was brought under control in 2003 with aggressive conventional public health measures.

Researchers at the Vaccine Research Center, National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), will conduct the trials. The experimental vaccine against SARS, or severe acute respiratory syndrome, will be tested on 10 healthy volunteers at the NIH Center in Bethesda, MD. The clinic will do periodic follow-up exams on each volunteer for 32 weeks.

"This experimental vaccine is an outstanding achievement by NIAID researchers," said Health and Human Services Secretary Tommy G. Thompson. "It is a model for research that could greatly shorten the time needed to create vaccines to be tested against other diseases."

"The Vaccine Research Center, a cutting-edge facility established here at NIH just five years ago, encompasses the entire spectrum of vaccine development from basic research to clinical testing," says NIH director Elias A. Zerhouni, MD. "This is why our team at NIAID has been able to develop this vaccine at an unprecedented pace, using technological discoveries that were not available just a few short years ago."

The primary goal of the study is to determine if the experimental vaccine is safe in people. A secondary goal is to assess how well the vaccine stimulates the immune system to produce antibodies and cellular immunity, in this case, focusing on the SARS spike protein. The spike protein protrudes from the virus' outer envelope and helps it bind to cells it infects.

SARS was brought under control with classic public health techniques: epidemiological investigations, patient isolations, quarantines of exposed people and stringent restrictions on travel. SARS was spotted first in China in November 2002. The virus sickened 8,096 and killed 774 worldwide by July 2003, according to the World Health Organization (WHO).

The sudden appearance of SARS, its severity, and its ability to be spread far and fast by international travellers, spurred medical researchers. NIAID researchers developed the vaccine with unprecedented speed. Just 21 months passed from when international health officials recognized SARS as a new infectious disease to the opening of the NIAID human clinical vaccine trial.

It often takes decades for scientists to develop a successful vaccine against an infectious disease.

"In the case of SARS, we have dramatically cut vaccine development time with powerful new tools from two different fields, molecular biology and information technology," says Anthony S. Fauci, MD, director of NIAID.

Instead of using weakened or inactivated virus, which is typical for vaccine development, the new vaccine is composed of a small circular piece of DNA that encodes the viral spike protein. Scientists modified the DNA to minimize the risk of it combining with the SARS virus or other viruses of the SARS type, called coronaviruses.

Scientists expect that the DNA will direct human cells to produce proteins very similar to the SARS spike protein. The immune system should recognize these proteins as foreign and then mount a defence against them. If the vaccinated person ever encounters the actual SARS virus, his or her immune system will be primed to neutralize it.

"It is truly remarkable that less than two years ago we were facing an unknown global health threat, and now we are testing a promising vaccine that may help us to counter that threat should it re-emerge," Dr Fauci said.

After SARS was identified as a disease, researchers worked hastily to identify the cause of the mysterious respiratory ailment and to develop therapies and vaccines. By April 2003, NIAID-funded researchers in Hong Kong were the first to show that SARS is a viral disease. They soon proved that a newly emerging coronavirus causes SARS. By May, an international collaboration of researchers had decoded the genetic sequence of the SARS coronavirus, opening many avenues of research to develop diagnostic tests, therapies and vaccines.

An NIAID team, lead by NIAID Vaccine Research Center director Gary J. Nabel, MD, used the available SARS coronavirus genomic information to develop a vaccine based on the gene for the SARS spike protein. The vaccine performed very well in mice, reducing the levels of virus in the lungs of infected mice by more than a million-fold, Dr Nabel and colleagues reported in "Nature" in March 2004.

"Two years ago, we didn't know that this virus existed. Today, we begin clinical trials of a promising vaccine candidate. We owe the speed of this research to modern molecular genetics. The technology enables us rapidly to translate scientific discoveries into clinical interventions and improves our ability to battle these ever-evolving, highly lethal microbes," says Dr Nabel.

Under a contract with NIAID, Vical Inc. of San Diego, CA, is producing the SARS vaccine for the NIAID clinical trial.