A recent study in Nature Medicine found that HIV-1 infected women have higher immune response rates compared to men with the same viral load, or amount of virus in the body.

The body’s immune response involves the activation of CD8+ T cells, which are specialized white blood cells known as cytotoxic T lymphocytes (CTLs). CTLs work to monitor all the cells in the body and destroy any foreign materials that enter the cells.

The study showed substantial sex differences in response to the HIV infection, specifically with regards to plasmacytoid dendritic cells (pDCs). pDCs are a type of dendritic cell, an immune cell, which are found in the blood and certain lymph organs. They express intracellular Toll-like receptors (TLR), which are proteins involved in the immune system that allows for the detection of viral and bacterial nucleic acids.

Results showed that pDCs derived from women produce more interferon-a (IFN-a) than men, which leads to an increase in activation of the immune system. INF-a are types of cell-signaling proteins produced by cells in the immune system in response to foreign invaders such as viruses, parasites, and tumor cells. This data is consistent with earlier findings that higher TLR responses to HIV-1 RNA in women lead to a more rapid HIV-1 disease progression.

The study recruited 980 antiretroviral treatment naïve HIV patients. Of these 980 subjects, 514 men and 109 women underwent comprehensive immunologic assessments, which included analysis of CD4 and CD8+ T cells activation.

pDC values were measured through intracellular cytokine staining (ICS). ICS is a technique used to detect product and accumulation of cytokines following stimulation. Cytokines are signaling molecules that are extremely important in cellular communication.

Additionally, progesterone was found to modulate pDC function in vitro. Progesterone is a steroid hormone that is commonly found in combination birth control pills. Sex hormone abundance can lead to an increase in pDCs’ immune response. In particular the study showed that in premenopausal women, higher progesterone levels were related to increased activation of pDCs.

The study concludes that sex differences can account for differences in immune response to HIV and its rate of progression. It also proposes that modulation of the TLR pathways in pDCs could be a method to reduce HIV progression and other RNA viruses.

For more information, please see this news article in eScience News or visit Nature Medicine’s website for the actual publication of the study.