ACAAI 2011: Diverse Gut Bacteria in Infancy Protects for Life

BOSTON—The array of bacteria in the gut biome in the first six months of life provides protective benefits for the rest of life, according to Larry Borish, MD, FACAAI, professor of medicine at the University of Virginia. Borish spoke this morning at the American College of Allergy, Asthma & Immunology’s annual meeting.

Borish discussed the link between bacteria and allergic and other autoimmune diseases. “There are dozens and dozens of bacteria in the gut but nobody knows what they’re doing.” They could reflect altered phenotypes or irrelevant colonization. Many questions exist, but the gut biome is actually the largest and earliest sources of microbial exposure.

“What the immune system sees in the gut in the first six months of life really determines our health for the rest of our lives,” Borish said. He discussed the “original antigen sin”—“you essentially create your own immune repertoire in the first six months of life. T cells cut their teeth on what they’re seeing in the gut. That is the mechanism for the education of the immune system.”

However, more than 90 percent of gut microorganisms cannot be cultured using current techniques. Borish predicted that the Phylochip will play a major role in advances in allergy, asthma and immunology over the next several years. The Phylochip is a high density nucleotide array with 500,000 probes that can detect 40,000 unique versions of the 16s RNA gene. “The Phylochip is going to define what we’re doing in the future,” he said.

Borish explained that the human immune system evolved and was genetically selected to function optimally in the environment and diet of our Neolithic ancestors. “We have really mucked with that” through changes in our diet and environment, he said. “Those changes are driving the epidemic we’re currently seeing in autoimmune disease.”

How does bacteria in the gut early in life explain what’s going on a decade later in your lungs? Borish posed this question and then discussed a study on mice and rheumatoid arthritis (RA). Only mice with a healthy gut biome developed RA. If there are no bacteria in the gut, no antibodies are made. The “healthy” mice had no Th17 cells. “I found this stunning,” Borish said.

The bacteria in our gut biome come from our immediate environment. “Every person evolved from children who sat in the back of the cave putting animal scat in their mouths,” he said. “That is evolutionary-ingrained behavior and I wondered why kids would do that if there was not some benefit.”

Linkage of neonatal gut microbiota to systemic immune disease is not obvious, Borish admitted, but an altered biome is associated with allergic diseases as well as diabetes, obesity and other diseases.