One of the continuing mysteries of the HIV/AIDS epidemic is why women usually develop lower viral levels than men following acute HIV-1 infection but progress faster to AIDS than men with similar viral loads.
Now a research team based at the Ragon Institute of Massachusetts General Hospital (MGH), MIT and Harvard has found that a receptor molecule involved in the first-line recognition of HIV-1 responds to the virus differently in women, leading to subsequent differences in chronic T cell activation, a known predictor of disease progression. Their paper, which will be published in an upcoming issue of Nature Medicine, is receiving early online release.
"This study may help to account for reported gender differences in HIV-1 disease progression by demonstrating that women and men differ in the way their immune systems respond to the virus," says Marcus Altfeld, MD, PhD, of the Ragon Institute and the MGH Division of Infectious Disease, the study's senior author. "Focusing on immune activation separately from viral replication might give us new therapeutic approaches to limiting HIV-1-induced pathology."
It has become apparent in recent years that HIV-1-infected patients with a high level of immune activation progress to AIDS more rapidly. Why this happens is an area of intense investigation. To explore whether gender-based differences in immune activation were responsible for faster disease progression in women, the Ragon Institute team and their collaborators focused on plasmacytoid dendritic cells (pDCs), among the first cells of the immune system to respond to HIV-1 and other viral pathogens. Earlier studies indicated that pDCs recognize HIV-1 using a receptor called Toll-like receptor 7 (TLR7), leading to production of interferon-alpha and other important immune system molecules.
After initial in vitro experiments showed that a higher percentage of pDCs from uninfected women produced interferon-alpha in response to TLR7 stimulation by HIV-1 than did cells from uninfected men, the researchers examined whether women's hormone levels had any effect on pDC activation. Supporting previous evidence that progesterone may modulate pDC activity, the researchers found that pDCs from postmenopausal women produced levels of interferon-alpha in response to HIV-1 that were closer to levels observed in men. They also found that, in premenopausal women, higher progesterone levels correlated with increased activation of pDCs in response to HIV-1.
Since it is known that the activation of T cells predicts the progression of HIV-1 infection to AIDS, the research team conducted a series of in vitro experiments showing that the stimulation of pDCs in response to HIV-1 led to the subsequent activation of CD8+ T cells by means of interferon-alpha secretion. They then tested blood samples taken from a group of chronically HIV-1-infected women and men prior to treatment initiation and confirmed that women had higher levels of CD8+ T cell activation than did men with the same blood levels of HIV-1.
"Taken together, these results support a model in which the same amount of virus induces stronger pDC activation in women than in men. While stronger activation of the immune system might be beneficial in the early stages of infection, resulting in lower levels of HIV-1 replication, persistent viral replication and stronger chronic immune activation can lead to the faster progression to AIDS that has been seen in women," Altfeld explains.
He adds that the study's results raise a number of important new questions, including exactly how sex hormones modulate the TLR7-mediated response of pDCs to HIV-1 and whether anti-TLR agents may help reduce immune activation in chronic HIV-1 infection. His team is beginning preliminary laboratory studies of the ability of TLR antagonists to reduce HIV-1-induced activation of pDCs.
Altfeld is an associate professor of Medicine at Harvard Medical School and director of the Innate Immunity Program at the Ragon Institute of MGH, MIT and Harvard. Co-lead authors of the Nature Medicine paper are Angela Meier, MD, PhD, and J. Judy Chang, PhD, of the Ragon Institute. Additional co-authors are Harlyn Sidhu, Tom Fang Wen, Robert Lindsay, Suzane Bazner, Hendrik Streeck, MD, and Galit Alter, PhD, Ragon Institute; Gregory Robbins, MD, MGH Division of Infectious Diseases; Ronald Bosch, PhD, Ellen Chan, PhD, and Liliana Orellana, Harvard School of Public Health; Richard Pollard, MD, University of California at Davis Medical Center; Smita Kulkarni, PhD, Jeffrey Lifson, MD, and Mary Carrington, PhD, National Cancer Institute; and Donna Mildvan, MD, Beth Israel Medical Center, New York. The study was supported by grants from the National Institute of Allergy and Infectious Diseases, the Harvard Center for AIDS Research, the Bill & Melinda Gates Foundation, the Doris Duke Charitable Foundation, and the National Cancer Institute.
Massachusetts General Hospital, established in 1811, is the original and largest teaching hospital of Harvard Medical School. The MGH conducts the largest hospital-based research program in the United States, with an annual research budget of more than $500 million and major research centers in AIDS, cardiovascular research, cancer, computational and integrative biology, cutaneous biology, human genetics, medical imaging, neurodegenerative disorders, regenerative medicine, systems biology, transplantation biology and photomedicine.
Sue McGreevey | EurekAlert!
Further reports about: > Aids > Disease > Foundation > HIV > HIV-1 > HIV-1-induced > HIV-1-infected > Infectious > Infectious Diseases > MGH > Medical Wellness > Nature Immunology > T cell activation > T cells > blood sample > cell activation > immune activation > immune system > menopausal women > viral replication
The personality factor: How to foster the sharing of research data
06.09.2017 | ZBW – Leibniz-Informationszentrum Wirtschaft
Europe’s Demographic Future. Where the Regions Are Heading after a Decade of Crises
10.08.2017 | Berlin-Institut für Bevölkerung und Entwicklung
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
25.09.2017 | Power and Electrical Engineering
25.09.2017 | Health and Medicine
25.09.2017 | Physics and Astronomy