Suppression of acute experimental allergic encephalomyelitis in Lewis rats with a mycophenolic acid derivative

Mycophenolic acid inhibits replication of Type 2 Winnipeg, a cerebrospinal fluid-derived reovirus isolate

BACKGROUND

The role of reoviruses in human disease is uncertain. Most identified cases are sporadic and asymptomatic or produce minor upper respiratory or gastrointestinal symptoms. In November 1997, a reovirus was isolated from the cerebrospinal fluid of a severe combined immune deficient infant in Winnipeg, Manitoba. RNA characterization and sequencing studies demonstrated this reovirus isolate to be unique. Thus, the virus was named Type 2 Winnipeg (T2W).

OBJECTIVE

Mycophenolic acid (MPA), a drug primarily used as an immunosuppressive agent, was assessed in the capacity to inhibit T2W viral growth.

METHODS

The effects of MPA on viral growth were determined by plaque reduction assays. Cells were treated with different MPA concentrations, infected with T2W and incubated at 37 degrees C for 0 h to 72 h. Virus titres were determined and compared with untreated controls.

RESULTS

Production of infectious T2W progeny decreased more than 99% at 3 microg/mL MPA compared with untreated controls. Inhibition was not caused by cell toxicity because there was no difference in cell viability. The 50% cell toxic dose was 30 microg/mL MPA.

CONCLUSIONS

MPA was able to inhibit viral growth of the novel reovirus T2W. Although MPA is usually used as an immunosuppressive agent, and despite the fact that T2W was isolated from an immunocompromised patient, these results suggest that MPA could have been used as a possible treatment at subimmunosuppressive doses. Animal studies to better define the antiviral and immunosuppressive activities of MPA (and its prodrug mycophenolate mofetil) appear warranted.

Mycophenolate mofetil treatment accelerates recovery from experimental allergic encephalomyelitis

Mycophenolate mofetil (MM) acts through its metabolite mycophenolic acid to inhibit inosine monophosphate dehydrogenase (IMPDH), an enzyme essential for purine synthesis in lymphocytes. Oral treatment with MM from the day of immunization for 2 weeks significantly delayed both the development of active experimental allergic encephalomyelitis (EAE) in Lewis rats and reduced the antibody response to myelin basic protein (MBP). MM did not deplete T and B cells, nor did it prevent induction of Th1 or Th2 cytokine in the regional nodes. Treatment of EAE with MM at the onset of clinical symptoms resulted in more rapid recovery from EAE than in control or cyclosporin A (CsA)-treated. MM-treated rats had less infiltration of T cells, B cells, macrophages and dendritic cells into brainstems than either the control or CsA-treated. MM-treated brainstems also had lower level of mRNA for Thl (IL-2, IL-12Rbeta2, IFN-gamma), Th2 (IL-4, IL-10) cytokines and TNF-alpha and TGF-beta compared to that in CsA and controls groups. This study shows MM was superior to CsA in the treatment of EAE and acted by reducing the inflammatory infiltrate, not by suppression of Ig response or by promotion of regulatory cells such as Th2 or Th3.