Bioavailability, biodistribution, and CNS toxicity of clinical-grade parvovirus H1 after intravenous and intracerebral injection in rats

Abstract

The autonomous parvovirus H1 (H1PV) is transmitted in rodent populations. The natural host is the rat, in which H1PV infection is pathogenic only in fetuses and newborns. H1PV infection of human cancer cells leads to strong oncolytic effects in preclinical models. In preparation for a clinical trial of H1PV injection in patients with malignant brain tumors, H1PV had to be prepared to Good Manufacturing Practice standards, including extensive toxicology testing in rats. Because the trial involves direct intracerebral injection of H1PV into the tumor and around the resection cavity, possible toxicity to CNS tissue had to be investigated. In addition, quantitative blood levels and the tissue distribution of H1PV after single intracerebral or intravenous injection were measured. Direct injection of H1PV into rat brain at 3 dose levels (maximum, 7.96 × 107 pfu) did not cause any macroscopic or histologic pathology. Furthermore, H1PV infection of the brain did not alter central or autonomous nervous system function. H1PV DNA was detected in almost all organs at 6 h, 48 h, and 14 d after intravenous and intracerebral injection, with the highest levels in liver and spleen. H1PV concentrations in most organs were similar after intravenous and intracerebral injection, indicating high permeability of the blood-brain barrier for this small virus. The current results demonstrate wide organ distribution of H1PV after intravenous or intracerebral injection, confirm that H1PV is nonpathogenic in adult rats even after direct injection into the brain, and form the basis for the ongoing ParvOryx01 clinical trial.

Figures

Figure 1.

(A) H1PV concentration in blood after a single intravenous administration of 7.96 × 107 pfu to male and female Wistar rats (n = 3 at each time point, except n = 6 rats of each sex at 6, 48, and 336 h). (B) H1PV concentration in blood after single intracerebral administration of 7.96 × 107 pfu to male and female Wistar rats (n = 3 at each time point, except n = 6 rats of each sex at 6, 48, and 336 h).

Figure 2.

Coronal brain sections (magnification, 4×) showing intracerebral injection channel in rats treated (A) with vehicle only or (B) 7.96 × 105 pfu, (C) 7.96 × 106 pfu, or (D) 7.96 × 107 pfu H1PV. (E) Parenchymal hemorrhages and focal minimal vasculitis (asterisk) in a rat treated with vehicle only (magnification, 20×). (F) Mild meningeal inflammatory cell infiltrates (arrows) and a small area of encephalomalacia (asterisk) near the injection channel in a rat treated with 7.96 × 106 pfu H1PV (magnification, 10×).