Chimp test for oral hepatitis B vaccine.

Chimp test for oral hepatitis B vaccine 

Oral vaccination for hepatitis B has moved one step closer to human trials. Two years ago, virologists made a vaccine of viruses genetically engineered to carry parts of the hepatitis B virus (SN: 7/18/87, p.39) and showed it could immunize hamsters against the disease. Now, scientists at the same laboratory have successfully immunized chimpanzees, with their human-like immune systems, using a similar vaccine in a gelatin capsule.

An oral hepatitis B vaccine could cost less, hurt less and store better than the three-shot regimen of current vaccines for the disease. The virus, spread through blood and sexual contact, can cause liver diseases. It currently infects about 300 million people worldwide.

With their colleagues, Michael D. Lubeck of Wyeth-Ayerst Research in Philadelphia and Robert H. Purcell at the National Institute of Allergy and Infectious Diseases in Bethesda, Md., attached the major surface antigen of the hepatitis B virus to adenoviruses, which normally infect human lungs but can also grow in the gut. The team fed the still-viable viruses to three chimps.

The type 4 and 7 adenoviruses used in the study can cause acute respiratory disease if inhaled. But growing in the gut, they induce immunity rather than illness. The U.S. military has used oral vaccines to immunize millions of soldiers against adenovirus, achieving a safety record that makes adenoviruses good vaccine candidates, the researchers say.

Eight weeks after vaccination, the team experimentally infected all three vaccinated chimps and one unvaccinated control chimp with hepatitis B virus. Two chimps that developed some antibodies to hepatitis B virus successfully fought off infection. The third vaccinated chimp developed no antibodies and contracted the disease, as did the control chimp.

The study represents the first report of a virus-carried vaccine stimulating hepatitis B antibodies in chimps, says virologist Bernard N. Fields of Harvard University Medical School in Boston. Moreover, it demonstrates for the first time that chimps can be infected with adenoviruses 4 and 7, Purcell and his colleagues assert in the September PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (Vol.86, No.17). And because adenoviruses normally infect humans rather than chimps, Fields and Purcell say the vaccine might stimulate a stronger antibody response in people.

"This may be the last step before clinical trials because this also constitutes a safety test of the recombinant carrier in what I think is a relevant animal model system," Purcell says.