MSCs: what’s in a name?

Whether they are "stem" or "stromal", from adult tissues or from umbilical cord blood, MSCs are being used for a lot of clinical trials. Read more

Mopping up immune troublemakers after transplant

Memory CD8+ T cells play an important role in kidney transplant rejection, and they resist drugs that would otherwise improve Read more

Tracking a frameshift through the ribosome

Ribosomal frameshifting, visualized through X-ray Read more

Ali Ellebedy

How antiviral antibodies become part of immune memory

Weapons production first, research later. During wartime, governments follow these priorities, and so does the immune system.

When fighting a bacterial or viral infection, an otherwise healthy person will make lots of antibodies, blood-borne proteins that grab onto the invaders. The immune system also channels some of its resources into research: storing some antibody-making cells as insurance for a future encounter, and tinkering with the antibodies to improve them.

In humans, scientists know a lot about the cells involved in immediate antibody production, called plasmablasts, but less about the separate group of cells responsible for the “storage/research for the future” functions, called memory B cells. Understanding how to elicit memory B cells, along with plasmablasts, is critical for designing effective vaccines.

EbolaBcells

Activated B cells (blue) and plasmablasts (red) in patients hospitalized for Ebola virus infection, with a healthy donor for comparison. From Ellebedy et al Nature Immunology (2016).

Researchers at Emory Vaccine Center and Stanford’s Department of Pathology have been examining the precursors of memory B cells, called activated B cells, after influenza vaccination and infection and during Ebola virus infection. The Ebola-infected patients were the four who were treated at Emory University Hospital’s Serious Communicable Disease Unit in 2014.

The findings were published Monday, August 15 in Nature Immunology.

“Ebola virus infection represents a situation when the patients’ bodies were encountering something they’ve never seen before,” says lead author Ali Ellebedy, PhD, senior research scientist at Emory Vaccine Center. “In contrast, during both influenza vaccination and infection, the immune system generally is relying on recall.”

Unlike plasmablasts, activated B cells do not secrete antibodies spontaneously, but can do so if stimulated. Each B cell carries different rearrangements in its DNA, corresponding to the specificity and type of antibody it produces. The rearrangements allowed Ellebedy and his colleagues to track the activated B cells, like DNA bar codes, as an immune response progresses. Read more

Posted on by Quinn Eastman in Immunology Leave a comment

Key to universal flu vaccine: embrace the unfamiliar

Vaccine researchers have developed a strategy aimed at generating broadly cross-reactive antibodies against the influenza virus: embrace the unfamiliar.

In recent years, researchers interested in a “universal flu vaccine” identified a region of the viral hemagglutinin protein called the stem or stalk, which doesn’t mutate and change as much as other regions and could be the basis for a vaccine that is protective against a variety of flu strains.

In an Emory Vaccine Center study, human volunteers immunized against the avian flu virus H5N1 readily developed antibodies against the stem region of the viral hemagglutinin protein. In contrast, those immunized with standard seasonal trivalent vaccines did not, instead developing most of their antibodies against the more variable head region. H5N1, regarded as a potential pandemic strain, is not currently circulating in the United States and the volunteers had not been exposed to it before.

The results were published Monday, August 25 in PNAS.

The key to having volunteers’ bodies produce antibodies against the stem region seemed to be their immune systems’ unfamiliarity with the H5N1 type of virus, says lead author Ali Ellebedy, PhD, postdoctoral fellow in the laboratory of Rafi Ahmed, PhD, director of Emory Vaccine Center and a Georgia Research Alliance Eminent Scholar.

Note: for a counterpoint, check out this 2013 Science Translational Medicine paper on how vaccination that induces anti-stem antibodies contributes to enhanced respiratory disease in pigs.

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Posted on by Quinn Eastman in Immunology Leave a comment