Scholar of the Month

I became hooked on microbiology in the fall of 1991 while an undergraduate at Frostburg State University in Maryland. Our microbiology professor, Dr. William Vail, wowed us with how tiny microbes create big problems. During the summer, I got to work with Dr. Gene Johnson (who was featured in The Hot Zone by Richard Preston) at Fort Detrick studying a terrifying group of viruses related to Ebola.

In graduate school at the University of Pennsylvania, Dr. David Roos introduced me to the fascinating world of parasites. Ever since, I have been driven to understand these amazing microbes. As Yoda would say, we should not judge them by their size. Microbes are surprisingly complicated and have evolved to do wondrous (and unsettling) things, like manipulating their host. COVID-19 serves as a stark reminder that we cannot be complacent when it comes to our ongoing battle with pathogens. We need to continually interrogate the marvels of their biology so we can find new ways to kill the ones that misbehave.

I was recruited to IUSM in 2000 under the mentorship of Dr. Sherry Queener, who studied fungal and protozoan parasites. I am eternally grateful for my research mentors, whose skill and patience taught me how to think critically and do science. Their inquisitiveness and curiosity inspired me to become a biomedical scientist and lifelong learner.

Infectious disease remains a significant cause of morbidity and mortality across the world. In addition to new viruses that pop up, we must now contend with the alarming problem of antibiotic-resistant bacteria and fungi—so called superbugs. There are also many single-celled parasites that cause neglected infectious diseases resulting in devastating losses in humans and livestock. Parasites like Plasmodium (malaria), Toxoplasma, Cryptosporidium, and Trypanosomes collectively take an enormous toll on global health. Climate change is further fueling the spread of these dangerous pathogens.

My lab focuses on Toxoplasma gondii, a parasite people get from cat waste or contaminated food and water. I was drawn to study this parasite during the height of the HIV/AIDS pandemic, when toxoplasmosis gained notoriety as a major threat to immunocompromised patients. Toxoplasma also causes miscarriage or birth defects if a person becomes infected for the first time during pregnancy. Toxoplasma infection is surprisingly common but does not cause overt signs of illness in normal healthy people. Instead, it encysts in their tissues, including the brain, where it presumably hangs out for the rest of the host’s life. An astonishing one-third of the world carries this parasite in their brain and there is no way to get rid of it—that is the problem my lab is focused on solving. It’s important because the Toxoplasma brain cysts can reactivate again and again in susceptible people, potentially robbing them of their sight or causing life-threatening heart and brain damage. In addition, the presence of these parasite cysts, even in healthy people, have been correlated with neurological problems. People infected with Toxoplasma show a heightened risk of schizophrenia, rage disorder, and risk-taking behaviors. Infected mice show similar behavioral changes, presumably to make them more likely to be eaten by cats, suggesting that this parasite has evolved to alter—or “zombify”—the brain in ways that drive the host to get eaten by a feline predator. Why? Because Toxoplasma can only complete its sexual stage in the belly of a cat, which culminates in the shedding of its infectious oocysts (eggs) into the environment.

We are working to determine how Toxoplasma converts from its rapidly growing form into its latent cyst form, the latter of which has no treatment. By understand the molecular mechanisms underlying this process, called microbial latency, we hope to expose vulnerabilities that can lead to new drugs that attack the latent stages of Toxoplasma. Such drugs are likely to be effective against other germs that rely on dormant stages for transmission or to evade drug treatments and our immune response.

It has always been euphoric to be the first person in the world to discover something new. I never tire of that rush. Who doesn’t like that dopamine hit after solving a mystery? Especially one that might literally save millions of lives one day. Equally rewarding is passing along your passion for science to the next generation of researchers. Seeing the light of curiosity beam in their eye is just as thrilling as seeing the experimental compound you’re investigating slaughter parasites.

I deeply enjoy sharing the wonders of science with others. The taxpayers fund the bulk of our work, which is published in language so esoteric that only specialists know what most of it means. “Translational research” should include the translation of our findings to the public in understandable terms. I enjoy writing articles for popular science outlets and doing radio/TV/podcast interviews so a larger audience can share in the awe of discovery and realize how important it is to fund scientific research. I’ve also written a book that grew out of our laboratory’s work called Pleased to Meet Me: Genes, Germs, and the Curious Forces That Make Us Who We Are.

When I’m not doing science of communicating science, I like to (surprise!) read about science. I’m an avid reader of popular science, but I do take breaks to watch Star Trek, read MAD magazine, or listen to music. I also run nearly every day, as that is when ideas usually pop into my head.

Since I started my lab in 2003, I’ve had the privilege of training 8 MS students, 4 PhD, 4 MD/PhD, 18 postdoctoral fellows, and 3 Assistant Research Professors. None of this work would be possible without them—they are the true heroes uncovering the clues to the puzzles we need to solve.

Despite having infected billions of people, many have never heard of Toxoplasma, so I am committed to educating the public about this dangerous parasite. I participate on social media sites that have communities of people affected by toxoplasmosis and do a lot of outreach to let others know how to avoid the infection. Much of this is aimed at pregnant women and immunocompromised individuals since they are the most susceptible. I recently worked with physicians who are experts in congenital toxoplasmosis to try and make testing for the parasite during pregnancy a standard part of prenatal care in the U.S. like it is in other countries—we wrote an article in The Conversation to raise awareness: “Toxoplasma is a common parasite that causes birth defects – but the US doesn’t screen for it during pregnancy.”

We are continuing our study of the gene regulatory mechanisms that allow microbes to persist in patients in a latent form. We have found unexpected complexity in this process; there are many layers of gene control, like peeling an onion. But that can be good news for drug development as it provides a wealth of potential pharmaceutical targets to kill both growing and dormant forms of Toxoplasma and other pathogens.