Women account for one in four people living with HIV in the United States. The majority of HIV infections in women occur through intercourse with infected men.
Scientists in the Section on Intercellular Interactions, within the Division of Intramural Research Program in Physical Biology, conducted a laboratory study to assess whether immune system proteins in semen affected the spread of HIV. The researchers developed a culture system of small pieces of cervical tissue from women, and used this system to simulate male-to-female transmission of HIV. They observed the spread of the virus under controlled laboratory conditions.
Researchers focused on the protein interleukin 7 (IL-7), which belongs to a family of proteins that regulate the immune response. It is present in normal semen, and occurs in especially high levels in the semen of men with HIV.
When IL-7 was present at levels typically found in semen of men with HIV, the HIV virus spread to the female tissue more readily. These results indicate that IL-7, alone or in combination with other factors, may increase male-to-female transmission of HIV.
Researchers hope that one day they may be able to prevent or delay the spread of HIV by blocking IL-7 (PMID: 23408885).