Bench to Bedside | September 2017

A Problem Solver, Dimitri Monos, PhD, Receives Distinguished Scientist Award

Puzzles always captivated Dimitri Monos, PhD, as a young child in Greece. If you gave him a geometry problem, it would instantaneously “capture his brain.” Today, this passion for problem solving fuels the tremendous time and energy that Dr. Monos devotes to tackling some of the greatest challenges in immunogenetics — a dynamic field of science and medicine that explores the connections between the immune system and genetics.

“For me, this work is another extension of having fun,” said Dr. Monos, director of the Immunogenetics Laboratory in the department of Pathology and Laboratory Medicine that provides integral services to all of the transplantation programs at Children’s Hospital of Philadelphia, along with supporting other clinical and research efforts. “Our whole lab has this culture. They are passionate and interested in this type of work. They are motivated. They take initiatives.”

Those same qualities are among the many reasons why Dr. Monos received the prestigious 2017 Distinguished Scientist Award from the American Society of Histocompatibility and Immunogenetics (ASHI), an international society of professionals dedicated to advancing the science, education, and application of immunogenetics and transplant immunology. The annual award recognizes ASHI members who have made extraordinary scientific contributions in their field, which may also have broad clinical applications to autoimmune diseases, cancer, vaccine development, and pharmacogenomics.

A Fascinating Region of the Human Genome 

Dr. Monos is an expert on histocompatibility molecules called human leukocyte antigens (HLA) and the genes that encode them, known as the major histocompatibility complex (MHC). HLA genes are tremendously diverse, or polymorphic. This is good news for people because the HLA polymorphisms give our immune system an advantage to fight off a wide variety of foreign invaders such as infectious diseases. But because there are so many versions of HLA genes, called alleles, it has been extremely challenging for researchers to characterize all of them.

Identifying key HLA alleles is critical for the success of bone marrow, blood stem cell, and solid organ transplantation. The closer the genetic match between the donor’s and recipient’s HLA genes, the less likely that the transplanted donor cells will trigger an immune response by the recipient’s body to destroy the foreign tissue. To help prevent this reaction, Dr. Monos’ lab performs precise HLA typing to ensure that antigens between the donor and recipient are as similar as possible.

Dr. Monos became fascinated by these complex HLA molecules after he earned his doctorate in biochemistry/immunology from Georgetown University in Washington, D.C., and in 1982 began working for the nearby National Institutes of Health in Bethesda, MD. He recognized that the extent of the range of polymorphisms was much greater than what scientists had previously considered. Currently, about 16,000 HLA polymorphisms are known.

“The expected range of these polymorphisms is in the millions, so pursuing their identification is extremely exciting,” Dr. Monos said.

After completing his fellowship training in immunology at the Hospital of the University of Pennsylvania (HUP), Dr. Monos moved to Harvard University in Cambridge, Mass., to work on an NIH grant. He returned to HUP’s Immunogenetics Laboratory in 1990, became a professor of Pathology and Laboratory Medicine at the Perelman School of Medicine at the University of Pennsylvania, and then in 1996 established CHOP’s Immunogenetics Laboratory as its first director. So far, Dr. Monos has contributed to the publication of more than 100 scientific papers.

Next-generation Sequencing: A Game Changer

Over the course of his career, a continuous evolution of technologies has refined the way scientists define HLA polymorphisms. Everyone in Dr. Monos’ lab is open-minded, looks for new ideas, and is adaptable moment to moment, so when next-generation sequencing came along in the mid-2000s, the team quickly embraced it as a game changer.

“I immediately made the connection that this technology potentially could address the HLA typing problem entirely, giving us information about the whole gene, all polymorphisms, even for regions outside the gene that can be of regulatory nature,” Dr. Monos said. “The field was open to a thorough and accurate characterization of these genes.”

And that is exactly what Dr. Monos and his colleagues did, publishing their findings in a 2010 paper titled, “Next-generation sequencing: the solution for high-resolution, unambiguous human leukocyte antigen typing.” They demonstrated how this single test could provide the highest resolution possible by covering the full HLA genomic region.

But Dr. Monos and his team didn’t stop there. The Immunogenetics Laboratory at CHOP was the first clinical lab to offer a new protocol for using HLA genotyping at the allele level based on a next-generating sequencing platform that was faster, more precise, and cost less than existing testing procedures. The test may improve transplantation outcomes through an enhanced assessment of donor compatibility, and it expedites the donor selection process. CHOP licensed the new method in June 2014, and it is distributed commercially throughout the world.

Allison Gasiewski is a technical specialist in Dr. Monos’ lab who performs clinical testing, communicates with the transplant programs, and improves procedures and products. When she entered the field 15 years ago, Gasiewski couldn’t have predicted that it would be possible for the transformation in how HLA typing is performed to happen so quickly.

“The way we used to do testing now seems ancient,” Gasiewski said. “It’s quite amazing. The field has changed so much. We have much better results, and we can make decisions for matching of organs much more confidently… I love that the work we do directly benefits our patients’ care. It’s rewarding.”

HLA Sequencing and Disease Association Studies

Dr. Monos’ staff is constantly experimenting with ways to fine-tune the protocol and creative applications for the technology. They collaborate with physicians who are interested in a wide spectrum of HLA-related issues beyond the sphere of transplantation, including experts from CHOP’s clinical divisions of Oncology, Hematology, Nephrology, Cardiology, Gastroenterology, Rheumatology, Neurology, Immunology and Infectious Diseases.

“We’ve found that with this HLA typing via next-generation sequencing, we are in a position to aid the physicians in many different ways that we wouldn’t have imagined,” Dr. Monos said.

For example, the technology helped to give new insights into the mechanisms underlying a condition called acquired aplastic anemia. Research suggests that this is an autoimmune disease in which your immune system’s T cells attack your own blood cells. In order to evade the T cells, the blood cells change their HLA genes as part of a process called clonal hematopoiesis. HLA-typing using next-generation sequencing allowed researchers to recognize the clonal signature of acquired aplastic anemia and identify clone emergence, which may assist in earlier diagnosis of the disease.

Plethora of Data Reveals New Research Directions

During his Distinguished Scientist Award lecture at ASHI’s annual meeting held in San Francisco in September, Dr. Monos discussed how next-generation sequencing technology also provides an advanced tool that reveals uncharted directions in MHC research. The HLA gene family sits in a genomic region that has four million bases and is loaded with other immunologic genes. Dr. Monos and colleagues — some helping him from as far away as his homeland in Greece — are taking a systematic look to understand the content of this region in detail, which is associated with at least 100 known unique disease phenotypes.

In a paper published in May, Dr. Monos and his study team reported on a single intronic microRNA, a genomic element that regulates post-transcriptional gene silencing, that is encoded by a HLA gene and controls the expression of nearly 200 transcripts involved with immune response. Their findings suggest a new role for HLA genes that could influence numerous metabolic pathways.

“Imagine if each one of the thousands of microRNAs in the MHC controls hundreds of transcripts and therefore control an extremely large number of processes in the cell,” Dr. Monos said. “If we take advantage of these new sequencing tools, maybe they will help in the deconvolution of these relationships.”

It’s an entirely new puzzle that Dr. Monos is eager to unravel.


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Produced by The Children’s Hospital of Philadelphia Research Institute.

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