Unicef expresses interest in tests on 'engineered' vaccine
By Rick Mitchell
Researchers in the United States have genetically engineered a versatile vaccine that may eventually make it possible to inoculate newborn children against a wide array of diseases with just one oral dose.
An all-in-one vaccine that can be given at birth would dramatically reduce the cost and complexity of inoculating against childhood diseases, allowing far more children to be protected than are now, say officials of the U.N. Children’s Fund (Unicef). A vaccine that does not have to be injected would eliminate risk of HIV contamination linked to re-use of needles, a common practice in developing countries.
In the 6 June issue of the journal Nature, two articles explain how scientists used recombinant DNA technology to splice antigens (protein particles from diseases) onto a live, but harmless, form of the tuberculosis bacteria, bacillus Calmette-Guerin (BCG). BCG has been used as a tuberculosis vaccine since 1948.
Injected into laboratory mice, the recombinant vaccine induced immune responses to the HIV virus (which causes AIDS), measles, polio, whooping cough and other diseases.
Clinical testing of the hybrid vaccine on humans should begin by late 1992, according to an author of one of the reports, Dr. Barry R. Bloom of the Albert Einstein College of Medicine in the Bronx. Bloom says recombinant BCG could be ready for use by decade's end, Unicef's target date for improving the means of protecting children from disease.
This is good news for Unicef, which distributed $60 million worth of vaccines to developing countries in 1990.
"We have direct a interest in the cost and effectiveness of vaccines," says Philip Vanhaecke, project officer of Universal Childhood Immunization at Unicef. Since the United Nations declared the 1990s the Decade of the Child last year, Unicef has made "a catalytic effort to bring people together through WHO [World Health Organization] to get research started," he said.
Research on recombinant BCG is funded in part by WHO, the U.N. Development Program (UNDP) and the World Bank. Other funding comes from the Howard Hughes Foundation and the U.S. National Institutes of Health.
"We need more refined, more heat-stable and more effective vaccines. These are always in need," said Rangit Atapatto, senior advisor in primary health care at Unicef. For example, "the current polio vaccine is 20 years old," and something better is needed, he said.
Because all vaccines have to be refrigerated, even in transport, storage costs can be prohibitively high in developing countries, Vanhaecke said.
Bloom said heat stability is not on the list of features that researchers are trying to hook on to recombinant BCG. However, the old vaccine was already among the most stable. Also, he said, BCG can be freeze-dried, and this should be explored.
Scientists at the Whitehead Institute for Biomedical Research in Cambridge, Mass., are pitting recombinant BCG against AIDS and other so-far incurable diseases. Results with laboratory animals have yielded significant immune responses, but the researchers caution that it is impossible to know whether the same reactions will occur in humans.
The original BCG is the world's most reliable and widely used vaccine, although it has been inexplicably ineffective in some countries. Since 1948, over 2 billion people have been inoculated with it. Because vaccines genetically resemble the diseases they immunize against, many are destroyed by maternal antibodies present in children's blood for the first six months of life. Consequently, it has proved impossible to inoculate newborns against measles.
BCG is one of the few vaccines that can be given at birth. This raises the possibility that, by attaching a measles antigen to recombinant BCG, it will be possible to inoculate children against the disease six months earlier, saving lives.
Effective for as long as 50 years, BCG is inexpensive to produce. Bloom says researchers hope to keep all these attributes on recombinant BCG, but they "have no way of knowing whether it will work or not."
There is still a lot of work ahead. First they have some fine-tuning to do on the vaccine, and "Then there is the long, arduous process of clinical trials in humans," Bloom said.
