Fatal Meningitis in Swine after Intrathecal Administration of Adeno-associated Virus Expressing Syngeneic Interleukin-10

Abstract

Interleukin-10 (IL-10) delivered by intrathecal (i.t.) gene vectors is a candidate investigational new drug (IND) for several chronic neurological disorders such as neuropathic pain. We performed a preclinical safety study of IL-10. A syngeneic large animal model was used delivering porcine IL-10 (pIL-10) to the i.t. space in swine by adeno-associated virus serotype 8 (AAV8), a gene vector that was previously found to be nontoxic in the i.t. space. Unexpectedly, animals became ill, developing ataxia, seizures, and an inability to feed and drink, and required euthanasia. Necropsy demonstrated lymphocytic meningitis without evidence of infection in the presence of normal laboratory findings for body fluids and normal histopathology of peripheral organs. Results were replicated in a second animal cohort by a team of independent experimenters. An extensive infectious disease and neuropathology workup consisting of comprehensive testing of tissues and body fluids in a specialized research veterinary pathology environment did not identify a pathogen. These observations raise the concern that i.t. IL-10 therapy may not be benign, that previously used xenogeneic models testing the human homolog of IL-10 may not have been sensitive enough to detect toxicity, and that additional preclinical studies may be needed before clinical testing of IL-10 can be considered.

Human interleukin‐10 delivered intrathecally by self‐complementary adeno‐associated virus 8 induces xenogeneic transgene immunity without clinical neurotoxicity in swine

“…The model allowed for frequent CSF sampling using an approach similar to bedside methods and provided a longer time series with higher resolution of IT IL-10 secretion kinetics compared to similar studies in swine and dogs. 9,10 …”

“…These observations differed markedly from the microscopic evidence of sterile meningitis observed for moribund animals that received pIL-10 delivered under identical conditions. 9 …”

“…9 Animals developed fatal neurotoxicity and a neuropathologic workup demonstrated sterile, lymphocyte-predominant meningitis. 9 Fatality was positively correlated to IL-10 concentration in CSF and after an extensive analysis, no pathogen was identified to be the cause of demise.…”

“…10 Literature review revealed that testing of IL-10 in CSF had involved xenogeneic IL-10 in both small and large animal species or syngeneic IL-10 in small animal species only. 9 The fatal swine study was the first to test syngeneic IT IL-10 in a large animal model.…”

“…In dogs the human ortholog was used, 10 i.e., a xenogeneic form was tested, while in swine the porcine form was used, i.e., a syngeneic model. 9 To improve interpretation of available large animal data regarding safety of IT IL-10, we sought to study xenogeneic IL-10 in a second large animal species. We delivered vector-encoded hIL-10 to the IT space in swine and found the treatment to be well-tolerated by all animals.…”