The results build on previous success in animal studies with a nasal nanoemulsion vaccine for influenza, reported by University of Michigan researchers in 2003.
Nanoemulsion vaccines developed at the Michigan Nanotechnology Institute for Medicine and the Biological Sciences at U-M are based on a mixture of soybean oil, alcohol, water and detergents emulsified into ultra-small particles smaller than 400 nanometers wide, or 1/200th the width of a human hair. These are combined with part or all of the disease-causing microbe to trigger the body’s immune response.
The surface tension of the nanoparticles disrupts membranes and destroys microbes but does not harm most human cells due to their location within body tissues. Nanoemulsion vaccines are highly effective at penetrating the mucous membranes in the nose and initiating strong and protective types of immune response, Baker says. U-M researchers are also exploring nasal nanoemulsion vaccines to protect against bioterrorism agents and hepatitis B.
The smallpox results, which appear in the February issue of Clinical Vaccine Immunology, could lead to an effective human vaccine against smallpox that is safer than the present live-vaccinia virus vaccine because it would use nanoemulsion-killed vaccinia virus, says Baker.
Anna U. Bielinska, Ph.D., a research assistant professor in internal medicine at the U-M Medical School, and others on Baker’s research team developed a killed-vaccinia virus nanoemulsion vaccine which they placed in the noses of mice to trigger an immune response. They found the vaccine produced both mucosal and antibody immunity, as well as Th1 cellular immunity, an important measure of protective immunity.
When the mice were exposed to live vaccinia virus to test the vaccine’s protective effect, all of them survived, while none of the unvaccinated control mice did. The researchers conclude that the nanoemulsion vaccinia vaccine offers protection equal to that of the existing vaccine, without the risk of using a live virus or the need for an inflammatory adjuvant such as alum hydroxide.
In antibody immunity, antibodies bind invading microbes as they circulate through the body. In cellular immunity, the immune system attacks invaders inside infected cells. There is growing interest in vaccines that induce mucosal immunity, in which the immune system stops and kills the invader in mucous membranes before it enters body systems.
A National Institutes of Health program, the Great Lakes Regional Centers of Excellence for Biodefense and Emerging Infectious Diseases, funded the research. If the federal government conducts further studies and finds the nanoemulsion smallpox vaccine effective in people, it could be a safer way to protect citizens and health care workers in the event of a bioterrorism attack involving smallpox, Baker says.
That would allay concerns about the current vaccine’s safety which arose in 2002. On the eve of the Iraq War, the Bush administration proposed a voluntary program to vaccinate military personnel and 500,000 health care workers with the existing vaccine to prepare for the possible use of smallpox virus as a biological weapon.