Scientists at the University of Central Florida College of Medicine have discovered a link between rheumatoid arthritis and Mycobacterium avium ssp. paratuberculosis, a pathogenic bacterium found in about half the cows in the U.S. The study is published in the journal Frontiers in Cellular and Infection Microbiology.
This is the first study to report the detection of DNA of Mycobacterium avium ssp. paratuberculosis in the blood of rheumatoid arthritis patients. Image credit: Edwin P. Ewing, Jr. / CDC.
Researchers had previously discovered a connection between Mycobacterium avium ssp. paratuberculosis (MAP for short) and Crohn’s disease.
Rheumatoid arthritis and Crohn’s share the same genetic predispositions and both are often treated using the same types of immunosuppressive drugs.
Those similarities led Dr. Saleh Naser from the University of Central Florida College of Medicine and colleagues to investigate whether MAP could also be linked to rheumatoid arthritis.
“Here you have two inflammatory diseases, one affects the intestine and the other affects the joints, and both share the same genetic defect and treated with the same drugs,” Dr. Naser said.
“Do they have a common trigger? That was the question we raised and set out to investigate.”
For the study, the scientists recruited 100 patients who volunteered clinical samples for testing.
78% of the patients with rheumatoid arthritis were found to have a mutation in the PTPN2/22 gene, the same genetic mutation found in Crohn’s patients, and 40% of that number tested positive for MAP.
“We believe that individuals born with this genetic mutation and who are later exposed to MAP through consuming contaminated milk or meat from infected cattle are at a higher risk of developing rheumatoid arthritis,” Dr. Naser said.
Although case studies have reported that some rheumatoid arthritis patients suffer from Crohn’s disease and vice versa, a national study needs to investigate the incidence of the two diseases in the same patients.
“We don’t know the cause of rheumatoid arthritis, so we’re excited that we have found this association,” said co-author Dr. Shazia Bég, a rheumatologist at the University of Central Florida College of Medicine.
“But there is still a long way to go. We need to find out why MAP is more predominant in these patients — whether it’s present because they have rheumatoid arthritis, or whether it caused rheumatoid arthritis in these patients.”
“If we find that out, then we can target treatment toward the MAP bacteria.”
The authors are conducting further studies to confirm findings and plan to study patients from different geographical and ethnic backgrounds.
_____
Robert C. Sharp et al. Polymorphisms in Protein Tyrosine Phosphatase Non-receptor Type 2 and 22 (PTPN2/22) Are Linked to Hyper-Proliferative T-Cells and Susceptibility to Mycobacteria in Rheumatoid Arthritis. Front. Cell. Infect. Microbiol, published online January 25, 2018; doi: 10.3389/fcimb.2018.00011
