Lung lesions in an individual infected with tuberculosis (TB) are surprisingly variable and independent of each other, despite whether the patient has clinically active or latent disease, finds study.
The research could point the way to new vaccines to prevent the hard-to-treat infection.
When the lungs become infected with Mycobacterium tuberculosis, the bacterium that causes TB, the body's immune system walls off the bacteria into lesions called granulomas, explained co-senior investigator JoAnne Flynn, Ph.D., professor of microbiology and molecular genetics, Pitt School of Medicine.
For the study, the research team infected monkeys with TB and then carefully tracked the granulomas that developed in the lungs. They determined that each granuloma starts with only one bacterium, and that bacterial replication continued for about four weeks before the body counters with an adaptive immune response to kill off the invaders.
Dr. Flynn said that this response was sufficient to kill all the bacteria and sterilize some granulomas, but bacteria persisted in others and spread to create new granulomas. You need only one granuloma to 'go bad' in order to get active TB.
Even when an animal had a severe, active infection, some of their granulomas were sterile, indicating the immune system was capable of killing bacteria, the researchers found.
The study was published in journal Nature Medicine.