DALLAS – Dallas researchers have successfully infected mice with the virus that causes AIDS, a major advance in researchers’ ability to test preventive medications, treatments and vaccines.
The mice were infected after rectal transmission, the most common way HIV is spread between men. HIV attacks immune cells and the mice have a humanized immune system to allow infection.
HIV is known to infect only people, and researchers trying to figure out how to stop the virus’ spread have relied mainly on monkeys infected with a monkey version of the virus. Mice are cheaper and easier to house than monkeys.
“If you want to figure out how to stop the spread of the virus, you have to have something like this,” said J. Victor Garcia, a professor of medicine at UT Southwestern Medical Center who led the new research. “This is the very first model where you can demonstrate transmission of HIV via a normal route.”
A report describing the mice appeared online Monday in the Journal of Experimental Medicine.
HIV can enter the body through the bloodstream, by needles shared by intravenous drug users, for example. But most commonly it is transmitted via sexual contact.
In the new study, six out of seven inoculated mice showed evidence of infection after the researchers introduced HIV particles.
Three of four mice tested made human antibodies to the virus, just like people do. Autopsies of the mice showed they were producing HIV in lymph nodes, spleen and other immune tissues. Virus also was being produced in the lungs, intestines, and male and female reproductive tracts.
Other researchers have infected mice with HIV, Garcia said, but those animals had a less complete humanized immune system. Also, he said, in those cases the virus was transmitted with an injection, not via a rectal route.
To create the mice, Garcia starts with mice that are born with no immune system of their own. A transplant of human fetal liver and thymus tissue kicks off a human immune system. After the immune system takes hold, the mice can be infected with HIV.
Garcia’s mice should allow researchers to search for topical antiviral medications known as microbicides that could be applied in the vagina or rectum, for example. That the mice mount an immune response to the virus also suggests that they could be used to test vaccines against HIV. New therapies for established infections could be studied using the mice, Garcia said.
Other researchers praised the new work.
“For people trying to prevent the epidemic from spreading, this is a significant advance,” said Dr. Ian McGowan, an associate professor of medicine at the University of California, Los Angeles. McGowan said he believed the biggest application of the mice would be in testing preventive medications such as microbicides.
The mice should allow researchers to get a glimpse of an infection as it’s taking place, said Dr. Martin Markowitz, an AIDS researcher at the Aaron Diamond AIDS Research Center.
“The exact time of infection is hard to pinpoint in people,” Markowitz said. “Even if you can, most people come in after they’ve been infected for several weeks.”
The biggest advantage to having HIV-susceptible mice is cost and ease of care, said molecular biologist Janet Young, program officer with the division of AIDS at the National Institute of Allergy and Infectious Diseases in Rockville, Md.
An estimated 1 million people in the United States are infected with HIV.