How HIV Infection Shrinks the Brain’s White Matter

by Katherine Unger Baillie

Researchers from Penn and CHOP detail the mechanism by which HIV infection blocks the maturation process of brain cells that produce myelin, a fatty substance that insulates neurons.

A confocal microscope image shows an oligodendrocyte in cell culture, labeled to show the cell nucleus in blue and myelin proteins in red, green, and yellow. Researchers from Penn and CHOP have shown that HIV infection prevents oligodendrocytes from maturing, leading to a reduction in white matter in the brain. (Image: Raj Putatunda)

It’s long been known that people living with HIV experience a loss of white matter in their brains. As opposed to gray matter, which is composed of the cell bodies of neurons, white matter is made up of a fatty substance called myelin that coats neurons, offering protection and helping them transmit signals quickly and efficiently. A reduction in white matter is associated with motor and cognitive impairment.

Earlier work by a team from the University of Pennsylvania and Children’s Hospital of Philadelphia (CHOP) found that antiretroviral therapy (ART)—the lifesaving suite of drugs that many people with HIV use daily—can reduce white matter, but it wasn’t clear how the virus itself contributed to this loss.

In a new study using both human and rodent cells, the team has hammered out a detailed mechanism, revealing how HIV prevents the myelin-making brain cells called oligodendrocytes from maturing, thus putting a wrench in white matter production. When the researchers applied a compound blocking this process, the cells were once again able to mature.

The work is published in the journal Glia.

“Even when people with HIV have their disease well-controlled by antiretrovirals, they still have the virus present in their bodies, so this study came out of our interest in understanding how HIV infection itself affects white matter,” says Kelly Jordan-Sciutto, a professor in Penn’s School of Dental Medicine and co-senior author on the study. “By understanding those mechanisms, we can take the next step to protect people with HIV infection from these impacts.”

“When people think about the brain, they think of neurons, but they often don’t think about white matter, as important as it is,” says Judith Grinspan, a research scientist at CHOP and the study’s other co-senior author. “But it’s clear that myelination is playing key roles in various stages of life: in infancy, in adolescence, and likely during learning in adulthood too. The more we find out about this biology, the more we can do to prevent white matter loss and the harms that can cause.”

Jordan-Sciutto and Grinspan have been collaborating for several years to elucidate how ART and HIV affect the brain, and specifically oligodendrocytes, a focus of Grinspan’s research. Their previous work on antiretrovirals had shown that commonly used drugs disrupted the function of oligodendrocytes, reducing myelin formation.

In the current study, they aimed to isolate the effect of HIV on this process. Led by Lindsay Roth, who recently earned her doctoral degree within the Biomedical Graduate Studies group at Penn and completed a postdoctoral fellowship working with Jordan-Sciutto and Grinspan, the investigation began by looking at human macrophages, one of the major cell types that HIV infects.

Read the full story in Penn Today.

Kelly Jordan-Sciutto is vice chair and professor in the University of Pennsylvania School of Dental Medicine’s Department of Basic & Translational Sciences and is director of Biomedical Graduate Studies. She is a member of the Penn Bioengineering Graduate Group.

Penn Alumnus Peter Huwe Appointed Assistant Professor at Mercer University

Peter Huwe, Ph.D.

Peter Huwe, a University of Pennsylvania alumnus and graduate of the Radhakrishnan lab, was appointed Assistant Professor of Biomedical Sciences at the Mercer University School of Medicine beginning this summer 2020 semester.

Huwe earned dual B.S. degrees in Biology and Chemistry in 2009 from Mississippi College, where he was inducted into the Hall of Fame. At Mississippi College, Huwe had his first exposure to computational research in the laboratory of David Magers, Professor of Chemistry and Biochemistry. He went on to earn his Ph.D. in Biochemistry and Molecular Biophysics in 2014 in the laboratory of Ravi Radhakrishnan, Chair of the Bioengineering Department at Penn. As an NSF Graduate Research Fellow in Radhakrishnan’s lab, Huwe focused his research on using computational molecular modeling and simulations to elucidate the functional consequences of protein mutations associated with human diseases. Dr. Huwe then joined the structural bioinformatics laboratory Roland Dunbrack, Jr., Professor at the Fox Chase Cancer Center as a T32 post-doctoral trainee. During his post-doctoral training, Huwe held adjunct teaching appointments at Thomas Jefferson University and at the University of Pennsylvania. In 2017, Huwe became an Assistant Professor of Biology at Temple University, where he taught medical biochemistry, medical genetics, cancer biology, and several other subjects.

During each of his appointments, Huwe became increasingly more passionate about teaching, and he decided to dedicate his career to medical education. Huwe is very excited to be joining Mercer University School of Medicine as an Assistant Professor of Biomedical Sciences this summer. There, he will serve in a medical educator track, primarily teaching first and second year medical students.

“Without Ravi Radhakrishnan and Philip Rea, Professor of Biology in Penn’s School of Arts & Sciences, giving me my first teaching opportunities as a graduate guest lecturer at Penn, I may never have discovered how much I love teaching,” says Huwe. “And without the support and guidance of each of my P.I.’s [Dr.’s Magers, Radhakrishnan, and Dunbrack], I certainly would not be where I am, doing what I love.  I am incredibly thankful for all of the people who helped me in my journey to find my dream job.”

Congratulations and best of luck from everyone in Penn Bioengineering, Dr. Huwe!