In what scientists say could be a significant breakthrough in AIDS prevention and treatment, researchers in Dallas have successfully infected humanized mice with HIV via rectal transmission.
"This is the very first model where you can demonstrate transmission of HIV via a normal route," said Dr. J. Victor Garcia, the team leader and a professor of medicine at the University of Texas Southwestern Medical Center.
Garcia said other researchers have infected mice with HIV, but those animals had a less completely humanized immune system. In addition, they were infected via injection. Rectal transmission is the most common way HIV is transmitted between men.
The mice were born with no immune system of their own; a human immune system developed after the transplantation of human fetal liver and thymus tissue and immune cells. After HIV particles were introduced into the rectums of the mice, six of seven showed evidence of HIV infection. Three of four mice produced antibodies to HIV, as humans do. On autopsy, HIV production was noted in the lymph nodes, spleen, other immune tissues, lungs, intestines, and male and female reproductive tracts.
That the mice's bodies produced an immune response suggests they could be used to test HIV vaccine candidates, Garcia said. They might also represent an important advancement in the search for protective microbicides that could be applied in the rectum or vagina.
"For people trying to prevent the epidemic from spreading, this is a significant advance," said Dr. Ian McGowan, associate professor of medicine at the University of California-Los Angeles. The biggest application for the mice would likely be in testing preventive products like microbicides, he said.
Previously, scientists researching HIV/AIDS have relied on monkeys infected with a simian version of the virus. Mice will be easier and less expensive to work with, said Dr. Janet Young, program officer at the division of AIDS at the National Institute of Allergy and Infectious Diseases.
The full report, "Intrarectal Transmission, Systemic Infection, and CD4+ T Cell Depletion in Humanized Mice Infected with HIV-1," appeared Monday in the online version of the Journal of Experimental Medicine (2007;doi:10.1084/jem.20062411).