Elite athletes with a syndrome of fatigue, recurrent sore throat, and shedding of Epstein-Barr virus in the saliva appear to have an exercise-induced defect of mucosal T-cell immunity that can be reversed with probiotic therapy, said Dr. R.L. Clancy of the University of Newcastle, Australia, and associates.
This is the first study to report reduced gamma interferon secretion in athletes with the fatigue syndrome, and the first to suggest a possible treatment. Further study is needed to clarify the mechanisms of the immune impairment and the therapy. Future research should also assess whether the findings can be applied to patients with other chronic fatigue illnesses, Dr. Clancy and associates said.
The researchers noted that protracted, intense training can cause recurrent upper respiratory tract symptoms and fatigue along with the appearance of Epstein-Barr virus (EBV) DNA in the saliva. They reasoned that intensive exercise, like other stressors, can impair T-cell -mediated immunity, which in turn impairs the containment of latent EBV infection and leads to viral reactivation.
They assessed saliva and blood samples in 9 athletes (mean age 25 years) with fatigue and recurrent sore throat and in 18 healthy volunteer athletes (mean age 26) who served as control subjects.
Gamma interferon levels from CD4 cells in blood samples were significantly lower in the fatigued athletes. Eight of the nine (90%) also were seropositive for previous EBV infection, and five of these eight subjects (63%) were actively shedding EBV DNA in their saliva.
After observing that isolates of Lactobacillus acidophilus enhanced T-cell function and protected against mucosal infection in mouse studies, the researchers treated the fatigued athletes with daily capsules of the organism for 4 weeks. This treatment raised gamma interferon secretion in the fatigued athletes to levels comparable to those in the control group (Br. J. Sports Med. 2006;40:351–4).
Before treatment, 6 of 24 saliva samples (25%) from fatigued athletes had detectable levels of EBV DNA; after treatment only 1 of 24 samples (4%) did.
The findings “suggest that a subtle T-cell defect in control mechanisms contributes to EBV reactivation and virus shedding,” and that probiotic therapy reverses the defect. The results must be confirmed in a larger study so clinicians can devise treatment strategies for affected athletes and possibly for patients with other fatigue syndromes, they said.