Outwitting The Chameleon Known As Hepatitis C

Scientists have developed effective vaccines against hepatitis A and B. But a third, related virus--hepatitis C--continues to elude both prevention and cure. The problem with hep-C is that the protein coating of the virus constantly mutates. So even when scientists come up with a vaccine that primes the body's immune cells to recognize the intruder, it is effective for only a short period of time.

Epimmune Inc., a biotech company in San Diego, is developing a vaccine that may do a better job. Instead of priming immune cells known as killer T-cells to go after the whole virus, Epimmune tries to focus the immune assault on small chains of amino acids, called epitopes, on the virus' outer coat. Robert W. Chesnut, vice-president for research and development, says Epimmune has discovered which of hepatitis C's epitopes are retained as the outer coat goes through its mutations. What's more, Chesnut believes epitope-based vaccines will work for almost any ethnic population--even though the diversity of immune-cell activity among Caucasians, African Americans, and Asians makes it difficult to develop effective vaccines.

So far, Epimmune's experiments have been confined to transgenic mice. But the company expects to begin human clinical trials in 2001. Chestnut believes that the same research could lead to therapeutic drugs as well as vaccines. Within three to four years, Epimmune hopes to have a product to combat hepatitis C, which afflicts an estimated 176 million people around the world and is closely associated with often fatal cancer of the liver.