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Gut flora may influence HIV immune response
Normal microorganisms in the intestines appear to play a pivotal role in how HIV foils a successful attack from the body’s immune system, according to recent data from Duke Medicine.
“Gut flora keeps us all healthy by helping the immune system develop, and by stimulating a group of immune cells that keep bacteria in check,” study researcher Barton F. Haynes, MD, director of the Duke Human Vaccine Institute, said in a press release. “But this research shows that antibodies that react to bacteria also cross-react to the HIV envelope.”
According to Haynes, the body fights most new infections by deploying as naïve B cells, which then imprint a memory of the pathogen so the antibody knows how to fight it in the future.
When the HIV invades and begins replicating in the gastrointestinal tract, pre-existing memory B cells, which fight bacterial infections such as Escherichia coli respond instead of the naïve B cells.
This occurs because the region of the HIV virus that the immune system targets, the gp41 region on the virus’s outer envelope, appears to be a molecular mimic of bacterial antigens that B cells are primed to target.
The result is that antibodies sent to attack the virus are ineffective, allowing the virus to escape neutralization.
The researchers said the findings were confirmed people without HIV. Among people without HIV, the researchers isolated mutated gp41-gut flora antibodies that cross-react with intestinal bacteria.
“The hypothesis now is that the gp41 antibody response in HIV infection can be derived from a pre-infection memory B cell pool triggered by gut bacteria that cross-reacts with the HIV envelope,” said researcher Ashley M. Trama in a press release. “This supports the notion that the dominant HIV antibody response is influenced by previously activated memory B cells that are present before HIV infection and are cross-reactive with intestinal bacteria.”
Disclosure: The authors report no relevant financial disclosures