Workshop Explores Interactions Between Infectious Disease, Environment
Chemical exposures may prime the immune system for more extreme responses to infection, and infectious diseases influence the body’s response to exposures. The need to study this interplay is urgent, according to experts who joined a National Academy of Science, Engineering and Medicine workshop held recently in Washington, D.C.
NIEHS and National Toxicology Program director Dr. Linda Birnbaum provided opening remarks, during which she emphasized that an interdisciplinary approach is crucial for gaining insights into how environmental health and infectious disease management can interact. “Exposure to environmental contaminants can alter the immune response to pathogens, and, of course, the pathogens can alter the response to the toxicants as well,” she told the audience. “So we have a two-way street we have to look at.”
For example, in a 1996 paper, Birnbaum reported that exposures to 2,3,7,8-tetrachlorodibenzo-p-dioxin altered the immune response of mice to the influenza virus and resulted in increased mortality. “This response has now been shown for things like air pollution, [which] can impact the response not just to influenza, but to staph and strep infections,” she said.
The body’s microbiomes—especially the one in the gut—are likely suspects in the search for agents of this response, due to their important roles in immunity. Dr. Rodney Dietert of Cornell University pointed out that toxicological routes of exposure involve the same entryways—such as the skin, airway and the gastrointestinal tract—that allow access to infectious agents. “They are also the physical locations where the majority of the human microbiome is housed,” Dietert said. Dr. Carlos Santos-Burgoa of George Washington University underscored the point. “Somewhere we lost track of [the fact that] the microbial world and chemical world are the same world.”
Several speakers addressed the complex challenges involved in studying contaminants, infections and the microbiome. Dr. Jennifer Nyland of Salisbury University discussed mercury’s role in provoking an inflammatory response in parts of the body such as the brain and gut. People are exposed to different forms of mercury, both organic and inorganic. Nyland noted that while effects on the immune system are common across these forms, that is where the similarity ends. “They do not have the same level of toxicity. And they are not metabolized in your system the same way.” Her viral studies in exposed mice found increased inflammatory responses and decreased anti-inflammatory action. But the responses were not seen with mercury alone; they were triggered only in the presence of a virus.
One theme of the workshop was that interdisciplinary, multidisciplinary and transdisciplinary approaches are needed to uncover the interplay between pathogens and toxicants.
Disciplines such as global health, epidemiology and immunotoxicology, as well as sectors as diverse as agriculture, housing, health care and transportation, are needed for studying pathogen–toxicant interactions.
Dr. Robert Newman of the Aspen Institute suggested that instead of approaching diseases as communicable or noncommunicable, we should view them as acute or chronic, to help bring the right combination of experts to the table.
“Despite all this interconnectedness, our responses often remain siloed in animal, human and environmental disciplines,” he said.