Infectious diseaseStealthy leprosy pathogen evades immune response
Leprosy, one of the world’s oldest known diseases, is a chronic infectious disease that affects the skin, the peripheral nerves, the upper respiratory tract, and the eyes and can lead to disfigurement of the hands, face, and feet; scientists’ findings point to new treatment pathways for leprosy – and other infectious diseases
A team of UCLA scientists has found that the pathogen that causes leprosy has a remarkable ability to avoid the human immune system by inhibiting the antimicrobial responses important to our defenses.
In one of the first laboratory studies of its kind, researchers discovered that the leprosy pathogen Mycobacterium leprae was able to reduce and evade immune activity that is dependent on vitamin D, a natural hormone that plays an essential role in the body’s fight against infections.
A University of California-Los Angeles release reports that the pathogen manipulated micro-RNAs, tiny molecules made of ribonucleic acids that carry information and that help regulate genes to direct cell activity, including immune system defenses. Micro-RNAs are short RNAs that do not code information for proteins, which carry out all cell activity; rather, they bind to the RNAs that do code for proteins and block them.
Published in the 29 January online edition of the journal Nature Medicine, the findings demonstrate how an infectious disease pathogen like M. leprae can use micro-RNAs to impact the immune system’s fight response.
“We may find that these tiny micro-RNAs can be exploited by pathogens to weaken our immune response,” said the study’s first author, Dr. Philip T. Liu, an assistant professor of medicine at the Orthopaedic Hospital Research Center and in the department of dermatology at the David Geffen School of Medicine at UCLA. “By better understanding how pathogens can escape our immune cells, we can design more effective therapies to boost our immune responses to these difficult to treat infections like leprosy.”
Leprosy, one of the world’s oldest known diseases, is a chronic infectious disease that affects the skin, the peripheral nerves, the upper respiratory tract, and the eyes and can lead to disfigurement of the hands, face, and feet. In 2008, approximately 249,000 new cases of leprosy were reported worldwide, according to the World Health Organization.
For the study, researchers compared the micro-RNAs in human skin lesions from two types of leprosy: tuberloid leprosy, a milder infection that is more easily contained, and lepromatous leprosy, which is more serious and causes widespread infection throughout the body.
In the lab, the scientists identified thirteen micro-RNAs that differed between the two types of leprosy. The micro-RNAs that were found to be more common in lepromatous leprosy seemed to target the genes important for directing key immune system cells, including macrophages and T cells.
The team found that a particular micro-RNA, hsa-mir-21, inhibited the
