Abstract

An increased rate of diffuse gliomas, including glioblastoma, has been noted in livestock farmers in Western countries. Some researchers have suggested that a zoonotic virus or bacteria present in the livestock animal’s feces or manure may be a possible etiologic factor. Mycobacterium avium subspecies paratuberculosis (MAP), the cause of a chronic enteropathy in domestic livestock and a probable zoonosis, is heavily excreted in an infected animal’s feces or manure, contaminating soil and ground on the animal’s farm. Once excreted in an animal’s feces, MAP lasts indefinitely in a dormant but viable form, and easily spreads outside farms to the surrounding environment. MAP’s presence throughout the soil in countries where MAP infection of domestic livestock is extensive and longstanding may explain the increased rates of glioblastoma in tennis and baseball players who handle balls coated with MAP-contaminated dirt. MAP infection is consistent with glioblastoma’s two defining histopathologic characteristics; endothelial cell proliferation and pseudopalisading necrosis. MAP is a nontuberculous or atypical mycobacterium, which can cause hypoxic necrotizing granulomas, granulomas that resemble areas of pseudopalisading necrosis, There are known bacterial causes of endothelial cell proliferation. Almost unique amongst intracellular bacteria, MAP’s variant isocitrate dehydrogenase 1 (IDH1) enzyme, a type 2-oxoglutarate ferredoxin oxidoreductase, can utilize a host cell’s cytosolic α-ketoglutarate in its own Krebs or tricarboxylic acid cycle. MAP’s ability to use a host cell’s α-ketoglutarate may explain the survival advantage of the cytosolic IDH1 enzyme mutation for patients with diffuse gliomas including glioblastoma, astrocytoma and oligdendroglioma, a mutation that results in a reduced supply of cytosolic α-ketoglutarate. MAP may therefore be one possible infectious cause of glioblastoma and the other histologic categories of diffuse glioma.

Key words: Diffuse gliomas infectious etiology; Endothelial cell proliferation; Necrotizing atypical mycobacterial granulomas; Transdifferentiation; Mycobacterium avium paratuberculosis