At the Immunology 2000 Conference held in Seattle during May 2000, an evaluation of the clinical impact of IsoprinosineŽ (inosine pranobex), an immunomodulator/antiviral on various immune functions in CFS patients was presented by Dr Ashok Kumar of the Children's Hospital of Eastern Ontario, Ottawa, Canada.

Chronic fatigue syndrome (CFS) is associated with several immune abnormalities, such as decreased NK cell mediated cytotoxicity and dysregulated production of cytokines. In this trial the effect of drug treatment on various immune functions in 16 CFS patients diagnosed according to the CDC CFS definition was assessed.

The patients were followed for a total of 28 weeks (12 weeks blinded, 4 weeks treatment free; 12 weeks open label phase). CFS patients at baseline compared to normal controls exhibited a significantly decreased NK cell activity as well as decreased mitogen-induced production of IL-10 and IL-12, as well as IFN-y in PBMC.

Clinical improvement based on the clinical staging was observed in 6 out of 10 patients (60%). The clinically improved patients showed a significantly enhanced NK activity, which correlated with the duration of treatment.

A significant increase in IL-12 production by T ceil mitogen stimulated PBMC was also observed in clinically improved patients treated for 28 weeks compared to patients on placebo. Treatment with IsoprinosineŽ for 12 weeks did not appreciably influence the production of IL-1a and IL -10. Discontinuation of treatment, however, resulted in enhanced production of both IL -1a and IL -10 only in clinically improved patients. When treatment was recommenced at week 16, significantly decreased production of these two cytokines was observed.

Treatment with IsoprinosineŽ for prolonged periods (28 weeks), also resulted in an enhanced number of CD4+ T helper cells, CD4+ and HLA-DR+ T cell numbers in peripheral blood only in clinically improved patients.

The results of this trial suggest the safety and efficacy of IsoprinosineŽ and its potential to enhance NK cell activity. In view of the small number of patients, further studies are required to investigate the contribution of IsoprinosineŽ- mediated immune effects to the pathogenesis of CFS.