Research Shows First Evidence That a Vaccine is Possible for Multiple Strains of Hepatitis C

SAN ANTONIO -- Researchers have found new hope in

the battle against hepatitis C, the No. 1 cause of liver failure and liver

transplantation in the United States. Studies at the Southwest Foundation for

Biomedical Research offer the first evidence that a vaccine against all

strains of this elusive virus should be possible, since chimpanzees that have

previously cleared infection with one strain of the virus show protective

immunity to multiple strains.

While a vaccine could be years away, the finding is significant.

Scientists previously had thought that prior infection with hepatitis C virus

(HCV) only produced immunity to the specific strain with which one had been

infected, said lead investigator Dr. Robert E. Lanford of the Southwest

Foundation for Biomedical Research in San Antonio (SFBR). Lanford, his

colleagues at SFBR, and collaborators at the Johns Hopkins University School

of Medicine in Baltimore detail their discovery in an article published in the

Journal of Virology for its first edition for the month of February 2004.

Hepatitis C has six different genotypes, or highly divergent groups of

viruses, with numerous strains within each genotype. Researchers and

pharmaceutical companies have tried for years to develop an HCV vaccine,

focusing primarily on genotype 1, the most common genotype in the United

States and Europe. But there has been doubt that an HCV vaccine for one

genotype could be effective against others.

The discovery by Lanford's group that a potential vaccine against one

HCV strain could produce protective immunity to multiple strains was based on

research with chimpanzees at SFBR's Southwest National Primate Research Center

in San Antonio. Chimpanzees, initially developed by scientists at NIH and

SFBR as an animal model for HCV, are the only animals besides humans that can

be infected with the virus. As with humans, some chimpanzees maintain chronic

infections, while others manage to clear their infection; however, unlike

humans, chronically infected chimpanzees do not develop liver disease.

SFBR scientists found that chimpanzees that had cleared previous infection

with genotype 1 later showed protective immunity when rechallenged with

several different HCV strains. That was true even when the animals were

challenged with a highly complex mixture containing strains from genotypes 1,

2, 3 and 4 - the four major genotypes affecting most HCV victims around the

world.

Lanford explained that this finding has significant implications for

eventual development of an HCV vaccine "because it means when we are able to

make an effective vaccine and immunize a population, people should be

protected against all strains of hepatitis C to which they might be exposed."

In addition to being the No. 1 cause for cirrhosis of the liver, HCV

infects an estimated 3 percent of the world population, and accounts for

25 percent of all cases of liver cancer in the United States.

Source: Southwest Foundation for Biomedical Research