The GI tract is considered a major ‘battlefield’ between the immune system and HIV. The intestinal mucosa is the site of early infection and aggressive transmission for HIV, making it the first line of defense against the infection. A better understanding of what happens in the GI tract may lead to knowledge of how to eradicate the HIV virus, new treatment options, and strategies for vaccine development.

A recent study by Dr. Chris Miller, CNPRC Infectious Diseases Unit, and Dr. Barbara Shacklett, UC Davis Department of Medical Microbiology and Immunology, used the monkey model of HIV, simian immunodeficiency virus (SIV), to determine if the ability of primary myeloid dendritic cells (mDCs) to promote the production of regulatory T cells (which modulate immune-system attacks) is affected by chronic SIV infection.

Results found that GI tissue in monkeys infected with SIV can ramp up production of regulatory T cells (Treg), weakening the body’s attack against the invading virus. Tissue mDCs from SIV- infected animals exhibited an enhanced capability to induce Treg and may contribute to the accumulation of Treg in lymphoid tissues during progressive infection. The activation status of dendritic cells impacts this process but the capacity to induce Treg was not restricted to mucosal dendritic cells in infected animals. The discovery could help explain how HIV evades the body’s immune defenses, and lead to a treatment strategy that could slow the production of this restraining type of T cell. This would let the immune system go after the virus more aggressively.