Infection with Helicobacter pylori may protect against multiple sclerosis risk in women
There is emerging evidence that the increasing rate of autoimmune diseases like multiple sclerosis in developed countries may be linked to a decline in the rates of infectious disease. Specifically, the hygiene hypothesis suggests that higher standards of sanitation and antibiotic use, along with a corresponding decrease in exposure to certain types of infection during childhood, may trigger the emergence of allergies and autoimmune disorders later in life.
Helicobacter pylori (H. pylori) is a gut bacterium that infects roughly 50% of the world’s population, and rates of infection with H. pylori have been steadily decreasing in developed countries. Most individuals infected by H. pylori have no symptoms, although infection has been linked to certain diseases like peptic ulcer disease and chronic gastritis. Recent studies have suggested that H. pylori infection during childhood can in fact be beneficial and protect against certain autoimmune disorders such as MS.
An Australian study published in the Journal of Neurology, Neurosurgery & Psychiatry by Dr. Allan Kermode and colleagues set out to determine if H. pylori infection has a positive effect on MS risk.
The research team assessed 550 people with MS and 299 healthy controls. Blood samples from each participant were tested for the presence of antibodies to H. pylori. Additionally, participants with MS were subjected to a neurological examination to measure certain clinical parameters, including age at onset of initial symptoms, disease duration and clinical course, relapse rate, and Extended Disability Status Scale (EDSS) score.
The study found that infection with H. pylori is lower in female participants with MS than in healthy controls, suggesting that H. pylori infection may act as a protective factor against MS risk in women. There was no association between H. pylori infection and MS risk in male participants. Furthermore, the researchers found that H. pylori infection was related to the primary progressive course of MS in females, although interestingly, infection was higher among females with primary progressive MS. Finally, although there was no relationship between H. pylori infection and relapse rate in those with MS, the absence of H. pylori was associated with a poorer EDSS score in female participants with MS.
This is the largest study to date evaluating the association between H. pylori infection and MS risk, and demonstrates the possibility that H. pylori infection can protect against the risk of developing MS in women. This study builds on previous findings showing that infections during childhood may suppress both allergic conditions and autoimmune disorders later in life, a phenomenon referred to as the hygiene hypothesis. While this study only demonstrates a correlation between H. pylori infection and MS risk, the authors speculate that infection may act to prime the immune system during an important window of development during childhood and shift the balance away from immune cell types that can lead to autoimmunity. Some unanswered questions still remain, however, such as why H. pylori infection only appears to be protective in women and not men, and why infection is more strongly associated with the primary progressive course of the disease in people with MS. Further studies are necessary to fill these important gaps in our understanding and identify a potential therapeutic role for H. pylori as a protective factor against MS.
Pedrini MJF et al. (2015) Helicobacter pylori infection as a protective factor against multiple sclerosis risk in females. J Neurol Neurosurg Psychiatry. [Epub ahead of print]