New Pox Vaccine Uses Genes Only

A vaccine using just four genes can protect monkeys against monkeypox and, in principle, its much more deadly cousin smallpox, U.S. government researchers said on Tuesday.

A vaccine using just four genes can protect monkeys against monkeypox and, in principle, its much more deadly cousin smallpox, U.S. government researchers said on Tuesday. The vaccine should be safer than the existing smallpox vaccine, which uses a live relative of the smallpox virus called vaccinia and which can cause serious and sometimes fatal side effects. “This work represents important progress toward a smallpox vaccine that is as effective as the current product, but safer,” said Col. Erik Henchal, commander of the U.S. Army Medical Research Institute of Infectious Diseases in Fort Detrick, Maryland, where the work was done. Writing in the May issue of the Journal of Virology, the USAMRIID team said they identified four key genes in the vaccinia virus used to make smallpox vaccines. “Rhesus macaques vaccinated with a DNA vaccine consisting of four vaccinia virus genes were protected from severe disease after an otherwise lethal challenge with monkeypox virus,” the researchers wrote. A vaccine using a single gene saved the monkeys’ lives, although they did develop a severe monkeypox infection. Smallpox was eradicated as a naturally occurring disease in 1979 and general vaccination against it stopped in the United States in 1972. But bioterrorism and security experts fear that some groups may have developed smallpox-based weapons. The United States has vaccinated 500,000 troops and about 40,000 health and emergency workers against smallpox just in case of attack. HEALTH-THREATENING SIDE EFFECTS But the vaccine is suspected of causing a few cases of heart inflammation and in the past it killed up to two in every 1 million people vaccinated. People with suppressed immune systems, such as the elderly, cancer patients and young children, are most at risk. And there may be a need to vaccinate people against monkeypox. Monkeypox kills between 1 percent and 10 percent of its human victims in the rain forests of central and western AfricaAn outbreak in the United States last June, traced to imported exotic pets, infected about 30 people. Virologist Jay Hooper, who led the USAMRIID study, said he would eventually like to test a vaccine using genes from the actual smallpox virus. His goal would be a vaccine that could protect humans and animals against all three related viruses — vaccinia, smallpox and monkeypox. But tests using smallpox, called variola by scientists, are a long way off. “It is not on track to go into humans right now,” Hooper said in a telephone interview. And to get samples of smallpox virus genes requires permission from the World Health Organization, which controls the two known repositories of smallpox virus in the United States, at the U.S. Centers for Disease Control and Prevention, and Russia. “People can work with the variola genome. You just can’t possess more than a certain percentage of the genome,” Hooper said. Genetically, the three viruses are so similar that it should be possible to find a few genes that will protect against all three viruses in a vaccine. “It is just a matter of figuring out which genes from which viruses make the best protection,” Hooper said. There is another hurdle — making it work well. “The problem with needle-injected DNA vaccines is they haven’t worked that well in humans,” Hooper said. Hooper said his work can help scientists understand just how vaccination protects against smallpox. The word vaccine comes from vaccinia and the first vaccine was against smallpox 200 years ago. But scientists still do not quite understand the body’s immune response to the vaccine.(Source: Reuters Health, April 2004)