Successful laboratory tests are pointing the way toward a new generation of safe, inexpensive vaccines that could help save millions of lives in developing countries, scientists say.
The goal is to create a one-shot vaccine that could be given at birth, earlier than most existing vaccines, and that would be effective for many years without the need for boosters, scientists from New York and Cambridge, Mass., said in separate reports being published today.
The new strategy involves modifying a long-used tuberculosis vaccine known as BCG, which is cheap and very safe. The scientists, from the Whitehead Institute in Cambridge and Albert Einstein College of Medicine in New York, used BCG, a bacterium that causes tuberculosis in cows, as a biological carrier into which they inserted genes from a variety of disease-causing microbes to create vaccines against the diseases.
The modified BCG, when injected into mice, produced immune reactions of the type that usually protect against subsequent infections, although more tests that could prove that the immunization is effective have not been conducted.
Some of the proposed vaccines would be cheaper and safer versions of ones already used to protect people against such diseases as tetanus, diphtheria, polio and whooping cough. The same technology might also pave the way for vaccines against AIDS, malaria, Lyme disease and widespread parasitic diseases.
The biologists are hopeful that the new type of vaccine could be produced in pill form, which would reduce the danger of spreading AIDS through contaminated needles. Another advantage for rural and underdeveloped areas is that the new vaccines would not have to be refrigerated.
Even in industrialized countries, such as the United States, the novel vaccines might have advantages over those now given to protect children against tetanus, diphtheria, whooping cough and other infections, said Barry Bloom of the Albert Einstein College of Medicine.
"My ambition would be that kids could get protection from Day Zero until the day they go to school, rather than needing boosters at one year or 18 months, the way it is now," Bloom said. Most vaccines are inactivated by antibodies from the mother's placenta and in breast milk and therefore can't be given until the antibodies have disappeared.
Researchers from Bloom's lab and MedImmune Inc. of Gaithersburg, Md., published one paper in today's issue of the journal Nature. Biologists Anna Aldovini and Richard A. Young of the Whitehead Institute in Cambridge published the other.
Young said he and Aldovini used key genes from the human immunodeficiency virus, or HIV, which causes AIDS, to modify the BCG bacterium. There should be no risk of causing AIDS or other disease because essential parts of the virus were omitted and the BCG had been rendered harmless.
In mice, the vaccine provoked the three different kinds of immune responses, ranging from short-acting to long-term, that are considered necessary for an effective vaccine.
Bloom reported that BCG vaccines his team developed also prompted all three types of immune response.
The research is supported by the National Institutes of Health and the World Health Organization.