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immunology

Present at the creation: immunology from chickens to lampreys

You can get far in biology by asking: “Which came first, the chicken or the egg?” Max Cooper discovered the basis of modern immunology by asking basic questions.

Cooper was selected for the 2012 Dean’s Distinguished Faculty Lecture and Award, and on Thursday evening dazzled an Emory University School of Medicine audience with a tour of his scientific career. He joined the Emory faculty in 2008 as a Georgia Research Alliance Eminent Scholar.

Max Cooper, MD

Cooper’s research on the development of the immune system, much of it undertaken before the era of cloned genes, formed the underpinnings of medical advances ranging from bone marrow transplants to monoclonal antibodies. More recently, his research on lampreys’ divergent immune systems has broadened our picture of how adaptive immunity evolved.

Cooper grew up in Mississippi and was originally trained as a pediatrician, and became interested in inherited disorders that disabled the immune system, leaving children vulnerable to infection. He joined Robert Good’s laboratory at the University of Minnesota, where he began research on immune system development in chickens.

In the early 1960s, Cooper explained, scientists thought that all immune cells developed in one place: the thymus. Working with Good, he showed that there are two lineages of immune cells in chickens: some that develop in the thymus (T cells) and other cells responsible for antibody production, which develop in the bursa of Fabricius (B cells). [On Thursday, he evoked chuckles by noting that a critical discovery that drove his work was published in the journal Poultry Science after being rejected by Science.]

Cooper moved on to the University of Alabama, Birmingham, and there made several discoveries related to how B cells develop. A collaboration with scientists at University College, London led to the identification of the places where B cells develop in mammals: fetal liver and adult bone marrow.

Cooper’s research on lampreys began in Alabama and has continued after he came to Emory in 2008. Primitive lampreys are thought to be an early offshoot on the evolutionary tree, before sharks, the first place where an immune system resembling those of mammals and birds is seen. Lampreys’ immune cells produce “variable lymphocyte receptors” that act like our antibodies, but the molecules look very different in structure. These molecules were eventually crystallized and their structure probed, in collaboration with Ian Wilson in San Diego.

Lampreys have variable lymphocyte receptors, which resemble our antibodies in function but not in structure

Cooper said he set out to figure out “which came first, T cells or B cells?” but ended up discovering something even more profound. He found that lampreys also have two separate types of immune cells, and the finding suggests that the two-arm nature of the immune system may have preceded the appearance of the particular features that mark those cells in evolution.

 

 

 

Posted on by Quinn Eastman in Immunology 1 Comment

One reason why SIV-infected sooty mangabeys can avoid AIDS

Sooty mangabeys are a variety of Old World monkey that can be infected by HIV’s cousin SIV, but do not get AIDS. Emory immunologist and Georgia Research Alliance Eminent Scholar Guido Silvestri, MD, has been a strong advocate for examining non-human primates such as the sooty mangabey, which manage to handle SIV infection without crippling their immune systems. Silvestri is division chief of microbiology and immunology at Yerkes National Primate Research Center.

Research shows sooty mangabeys have T cells that can do the same job as those targeted by SIV, even if they don't have the same molecules on their surfaces

A recent paper in the Journal of Clinical Investigation reveals that sooty mangabeys have T cells that perform the same functions as those targeted by SIV and HIV, but have different clothing.

Silvestri and James Else, the animal resources division chief at Yerkes, are co-authors on the paper, while Donald Sodora at Seattle Biomedical Research Institute is senior author.

One main target for SIV and HIV is the group of T cells with the molecule CD4 on their surfaces. These are the “helper” T cells that keep the immune system humming. Doctors treating people with HIV infections tend to keep an eye on their CD4 T cell counts.

In the paper, the scientists show that sooty mangabeys infected with SIV lose their CD4 T cells, without losing the ability to regulate their immune systems. What’s remarkable here is that sooty mangabeys appear to have “double negative” or DN T cells that can perform the same functions as those lost to SIV infection, even though they don’t have CD4.

CD4 isn’t just decoration for T cells. It’s a part of how they recognize bits of host or pathogen protein in the context of MHC class II (the molecule that “presents” the bits on the outside of target cells). Somehow, the T cells in sooty mangabeys have a way to get around this requirement and still regulate the immune system competently. How they do this is the topic of ongoing research.

The authors write:

It will be important to assess DN T cells in HIV-infected patients, particularly to determine whether these cells are preserved and functional in long-term nonprogressors. These efforts may lead to future immune therapies or vaccine modalities designed to modulate DN T cell function. Indeed, the main lesson we have learned to date from this cohort of SIV-infected CD4-low mangabeys may be that managing immune activation and bolstering the function of nontarget T cells through better vaccines and therapeutics has the potential to contribute to preserved immune function and a nonprogressive outcome in HIV infection even when CD4+ T cell levels become low.

Posted on by Quinn Eastman in Immunology Leave a comment

Another avenue of HIV trickery reveals opportunity

Emory and University of Rochester researchers have discovered an extra way by which HIV adapts to survive in a hiding spot in the human immune system. The results are published in the Journal of Biological Chemistry.

A team led by Baek Kim from the University of Rochester and Raymond Schinazi from Emory found that when HIV faces a shortage of the building blocks it usually uses to replicate, the virus adapts by using different building blocks. The discovery may offer scientists a new way to try to stop the virus.

One of HIV’s favorite hiding spots is an immune cell called a macrophage, whose job is to chew up and destroy foreign invaders and cellular debris. One can think of macrophages as worker bees: they don’t reproduce because they’re focused on getting stuff done.

Raymond Schinazi, PhD, DSc, is director of the Laboratory of Biochemical Pharmacology at Emory's Center for AIDS Research

Normally, HIV uses “dNTPs” (building blocks of DNA), but dNTPs are found at very low levels in macrophages because they’ve stopped dividing and making new DNA. Current drugs generally target dNTPs, and aim at the infection in a different type of cells: T cells.

Macrophages do have high levels of RNA building blocks (“rNTPs”). The team found that HIV uses primarily rNTPs instead of dNTPs to replicate inside macrophages. When the team blocked the ability of the virus to interact with rNTPs, its ability to replicate in macrophages was cut by more than 90 percent.

“The first cells that HIV infects in the genital tract are non-dividing target cell types such as macrophages,” Kim says. “Current drugs were developed to be effective only when the infection has already moved beyond these cells. Perhaps we can use this information to help create a microbicide to stop the virus or limit its activity much earlier.”

Compounds that interfere with the use of rNTPs already exist and have been tested as anti-cancer drugs.

“We are now developing new anti-HIV drugs jointly based on this novel approach that are essentially non-toxic and can be used to treat and prevent HIV infections,” Schinazi says.

Baek Kim, PhD

The first authors of the paper are graduate students Edward Kennedy from Rochester and Christina Gavegnano from Emory. Other authors include graduate students Laura Nguyen, Rebecca Slate and Amanda Lucas from Rochester, and postdoc Emilie Fromentin from Emory.

The research was funded by the National Institute of Allergy and Infectious Disease and the Department of Veterans Affairs.

University of Rochester press release

Posted on by Quinn Eastman in Immunology 1 Comment

Adjuvants: once immunologists’ “dirty little secret”

Two presentations on Emory research at last week’s AIDS Vaccine 2010 conference concerned adjuvants. These are substances that act as amplifiers, stimulating the immune system while keeping its focus on the specific components of a vaccine.

Charlie Janeway (1943-2003)

Immunologist Charlie Janeway once described adjuvants as immunology’s “dirty little secret,” because for a long time scientists did not know how they worked. Some adjuvants can sound irritating and nasty, such as alum and oil emulsion. Alum is the only vaccine adjuvant now licensed for human clinical use in the US. Over the last few years, scientists have learned that adjuvants rev up what is now known as the “innate immune system,” so that the body knows that the vaccine is something foreign and dangerous.

Rama Rao Amara, a vaccine researcher at Emory Vaccine Center and Yerkes National Primate Research Center, and Harriet Robinson, former head of microbiology and immunology at Yerkes and now chief scientific officer at the firm GeoVax, both described extra ingredients for the DNA/MVA vaccine that Robinson designed while at Yerkes in collaboration with NIH researchers.

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Posted on by Quinn Eastman in Immunology Leave a comment

Respiratory infection may lead to weaker immunological memory

How you vaccinate helps determine how you protect. This idea lies behind many researchers’ interest in mucosal vaccines. How a vaccine is administered (orally/nasally vs intramuscular, for example) could make a difference later, when the immune system faces the bad guys the vaccine is supposed to strengthen defenses against.

How does the route of immunization affect the quality of immunity later on? For example, is a nasal spray best when trying to prevent respiratory infections?

A recent paper from Emory Vaccine Center director Rafi Ahmed’s laboratory challenges this idea. The paper was published in the Journal of Immunology. Scott Mueller, now an Australian Research Council research fellow at the University of Melbourne, is first author.

Memory T cells are a key part of a response to a vaccine, because they stick around after an infection, enabling the immune system to fight an invading virus more quickly and strongly the second time around. In the paper, the Emory team compared memory T cells that form in mice after they are infected in the respiratory system by a flu virus or throughout their bodies by a virus that causes meningitis (lymphocytic choriomeningitis virus or LCMV).

The authors engineered a flu virus to carry a tiny bit of LCMV (an epitope, in immunological terms) so that they could compare apples to apples by measuring the same kind of T cells. They found that memory T cells generated after a flu infection are weaker, in that they proliferate and stimulate other immune cells less, than after a LCMV infection. This goes against the idea that after a respiratory infection, the immune system will be better able to face a challenge in the respiratory system.

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Posted on by Quinn Eastman in Immunology Leave a comment

When your immune system calls the shots

Bali Pulendran, PhD

A tiny invader, perhaps a virus or a microbe, enters the body, and our ancient immune system responds. But how does it know what kind of invader has landed? And once it knows, how does it decide what kind of immune response it should launch?

In humans, the immune system consists of two parallel systems working with one another to fend off invaders. One is the innate immune system, the other the adaptive immune system.

Immunologist Bali Pulendran studies how those two systems work together to identify and respond to all kinds of intruders including pathogens, viruses and microbes.

It’s the innate immune system’s job to recognize the first signs of infection—that is, the moment a pathogen enters the body. “In a sense they act as smoke detectors if you will,” says Pulendran. “Little alarms.”

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Posted on by Robin Tricoles in Immunology Leave a comment

Moving flu vaccine research forward

The scientists in the lab of Richard Compans, PhD, professor of microbiology and immunology at Emory, are hard at work, imagining the unimaginable: A time when patients can self-administer flu vaccines. A time when vaccination does not require exposure to inactive viruses. A time when a universal vaccine could protect from all varieties of influenza: swine, avian, seasonal and strains still emerging.

Richard Compans, PhD (right), with colleague Mark Prausnitz, PhD, from Georgia Tech

But it’s not just hope that motivates them as they work. Emory’s scientists are fighting the clock against another possible future: a time of pandemic and uncontrollable virus mutation. The recent emergence of H1N1 and H5N1, known colloquially as swine flu and avian flu, have added an even greater sense of urgency to their task.

“The H5N1—the virus derived from avian species—has a 60 percent mortality,” says Emory microbiologist Sang-Moo Kang, PhD. Yet that strain of influenza hasn’t resulted in many human deaths, because, so far, avian flu spreads only to humans who are in contact with infected birds.

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Posted on by Jennifer Johnson in Immunology Leave a comment

Eye diseases and immune system link studied

Drawing shows areas of the eye

Emory Eye Center researchers are looking at the role of the immune system in the inflammation of the eye and the progression of eye diseases.

Santa Ono, PhD, professor of ophthalmology, Emory School of Medicine and researcher at the Emory Eye Center, and Emory senior vice provost for undergraduate education and academic affairs, and his team at the R. Howard Dobbs Jr. Ocular Immunology Lab, focus on the immune component of age-related macular degeneration (AMD), ocular cancer (melanoma and retinoblastoma) and ocular inflammation.

Santa J. Ono, PhD

Macular degeneration is the leading cause of sight impairment and blindness in older people. The macula, in the center of the retina, is the portion of the eye that allows for the perception of fine detail. AMD gradually destroys a person’s central vision, ultimately preventing reading, driving, and seeing objects clearly

In a recent article of Emory Magazine, Ono, an ocular immunologist, says, “If a person with AMD looks at graph paper, some of the lines will be wavy instead of straight. Certain parts of the image are no longer being transferred to the brain.”

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Posted on by Joy Bell in Uncategorized Leave a comment

Tailoring transplant drugs for children

For adult organ transplant recipients, juggling a lifetime regimen of immunosuppressant drugs is difficult enough, but for children it presents an even greater challenge.  These drugs, which also can have toxic side effects, must strike a delicate balance between preventing organ rejection and protecting from infections.

But children’s immune systems are still “learning” what distinguishes them from the world around them, and children are constantly developing and changing, both physically and emotionally. This puts them at greater risk for complications either through inappropriate medication or failure to take these drugs properly.

A grant from the National Institute of Allergy and Infectious Diseases (NIAID), through the American Recovery and Reinvestment Act (ARRA), will support new studies at Emory University and Children’s Healthcare of Atlanta to help clinicians tailor therapies specifically for children receiving transplants.  The project will include hiring of additional personnel to undertake these studies.

Allan D. Kirk, MD, PhD, is principal investigator of the project, which is supported by a two-year grant of nearly $1.65 million. Kirk is professor of surgery and pediatrics in Emory University School of Medicine and a Georgia Research Alliance Eminent Scholar. He also is vice chair of research in the Department of Surgery and scientific director of the Emory Transplant Center.

The ARRA-funded project will not only help determine which medications children should take, but also will give them the support to care for their transplanted organs.  The Emory scientists are studying new biological monitoring technologies that can identify unique ways to determine exactly how much medication a child really needs. These studies are being combined with a novel transition care clinic specializing in helping children cope with their illness and assuming responsibility for their care.

“This award indicates exceptional insight by the NIAID into the critical link between a child’s physical well-being and their emotional maturity,” says Kirk. “It will accelerate progress in this vital area of research for a very deserving subset of chronically ill children.”

Posted on by Holly Korschun in Uncategorized 1 Comment

World AIDS Day reminds of research priorities

AIDS quilt panels_shadowsEmory University is hosting an 800-panel display of The AIDS Memorial Quilt in recognition of World AIDS Day. “Quilt on the Quad,” on the Emory quadrangle, is the largest collegiate display and the second largest in the world today. An opening ceremony featured a talk by Sandra Thurman, president and CEO of the International AIDS Trust, based at Emory’s Rollins School of Public Health. Members of the Emory community read the names of each individual memorialized by a quilt panel on the quad.

An estimated 60 million people have acquired HIV, and 25 million people have died from AIDS. Emory scientists and physicians have been leaders in research to develop effective drugs and vaccines against HIV and AIDS. The Emory Center for AIDS Research is an official National Institutes of Health CFAR site. More than 120 faculty throughout Emory are working on some aspect of HIV/AIDS prevention or treatment.

More than 94 percent of HIV patients in the U.S. on life saving antiviral therapy take a drug developed at Emory. And many of the scientists within the Emory Vaccine Center are focused on finding an effective vaccine against HIV. A vaccine developed at the Vaccine Center and Yerkes National Primate Research Center is being tested nationally in a phase II clinical trial.

The Hope Clinic of the Emory Vaccine Center is conducting several clinical trials of HIV vaccine candidates through the HIV Vaccine Trials Network (HVTN) sponsored by the NIH. The HVTN 505 vaccine trial, which is currently enrolling at the Hope Clinic and 13 other cities around the country, is a test-of-concept efficacy trial for an NIH vaccine (DNA + Adnovirus – gag/pol/nef/EnvABC).

Mark Mulligan, MD, executive director of Emory’s Hope Clinic, emphasizes that on World AIDS Day there would be no better way to honor those who have already died or are already infected than to produce a vaccine that will protect their families and friends.

“The recent analysis of the RV144 Thai trial surprisingly taught us that an envelope glycoprotein vaccine regimen can protect (albeit modestly, thus far)! This is an amazing result that has re-ignited the field, and is capturing the attention of the community. We must do all we can to leverage this result for success,” Mulligan says. “Albert Sabin said that no scientist can rest while a vaccine that might help humanity sits on the shelf. To me, this underscores the importance of successfully executing the HVTN 505 trial.”

Posted on by Holly Korschun in Immunology Leave a comment