Meningiomas and fibroblastic neoplasia in calves induced with the bovine papilloma virus.

Test calves were inoculated at approximately one week of age and necropsied from 33 to 278 days postinoculation. There was marked variation in the response of fibroblasts in different tissues to bovine papilloma virus (BPV). Intracranial meningeal fibromas and cutaneous fibropapillomas (warts) were induced in 17 of 19 calves (89.5%) at the site of inoculation with suspensions of partially purified BPV. Intracranial fibromas were evident as early as 33 days and the skin tumors as early as 16 days postinoculation. Fibromatous tumors were also induced at inoculation sites in the rumen, urinary bladder, and tongue of these animals. There was moderate stimulation of fibroblasts in the perineurium and epineurium of peripheral nerves and spinal nerves at the level of the cauda equina following local exposure to BPV. A similar response was noted at inoculation sites in the abomasum and small intestine in some calves. The tumors were composed of spindle-shaped, fibroblastic cells arranged in interlacing bundles or whorls. Virus particles were not observed in the fibroblastic tumor cells of the brain by electron microscopic studies nor could infectivity be demonstrated following the inoculation of intracranial tumor tissue into the skin of susceptible calves.