Influence of method of systemic administration of adenovirus on virus-mediated toxicity: focus on mortality, virus distribution, and drug metabolism.

INTRODUCTION: Doses of 2 x 10(12) virus particles/kilogram (vp/kg) and higher of recombinant human adenovirus serotype 5 (HAdV-5) given via the tail vein induce significant toxicity and mortality in the rat. This was not observed when doses of 5.7 x 10(12) vp/kg were given through a surgically implanted jugular catheter. Here we assess how the manner by which HAdV-5 is introduced into the systemic circulation affects biodistribution, transgene expression, toxicity and mortality 0.25, 1, and 4 days after treatment in the rat. Animals were given 5.7 x 10(12) vp/kg of HAdV-5 expressing beta-galactosidase or saline through a jugular catheter or by direct tail vein injection. RESULTS: All animals survived after jugular vein dosing. Tail vein injection of HAdV-5 increased the mortality rate to 42% (p< or =0.01). All deaths occurred within 4 h. Animals dosed through the jugular vein had significantly higher levels of transgene expression in the liver and spleen and significantly more viral genomes in these tissues and kidney and lung within the first 24 h of viral infection compared to those dosed by tail vein injection (p< or =0.01). There was no significant difference between the groups thereafter. Samples from animals that died contained even higher levels of viral genomes and serum transaminases were elevated on average by a factor of 4 at the time of death. There was no significant difference between the two dosing methods with respect to changes in hepatic cytochrome P450 expression and activity throughout the study. CONCLUSION: These findings suggest that the method of systemic administration should be carefully considered when assessing toxicity data and other parameters at early time points after virus administration in the rat and possibly other animal models.

Renal pathophysiology after systemic administration of recombinant adenovirus: changes in renal cytochromes P450 based on vector dose.

Recombinant adenovirus (Ad) significantly alters hepatic cytochrome P450 (CYP). Because changes in renal function can alter hepatic CYP, the effect of Ad on renal CYPs 4A1, 4A2, 4F1, and 2E1 was evaluated. Male Sprague-Dawley rats were given one of six intravenous doses (5.7x10(6)-5.7x10(12) viral particles/kg [VP/kg]) of Ad expressing beta-galactosidase or saline. CYP protein, activity, gene expression, and serum creatinine (SCr) were evaluated 0.25, 1, 4, and 14 days later. Doses of 5.7x10(11) and 5.7x10(12) VP/kg increased CYP4A protein within 24 hr by 35 and 48%, respectively (p<0.05). A similar trend was observed on day 4. CYP4A1 mRNA doubled 6 hr after doses of 5.7x10(10)-10(12) VP/kg (p<0.01). Similar effects were observed 1 day after each dose tested. CYP4A2 gene expression was 20% above control 1 day after treatment with 5.7x10(10)-10(12) VP/kg and remained high through day 14. CYP4F1 expression was unaffected by all doses (p=0.08). CYP2E1 activity and gene expression were significantly suppressed 24 hr after administration of all doses and began to normalize by day 14 (p<0.01). SCr was significantly reduced (approximately 50%) throughout the study for doses at and below 5.7x10(11) VP/kg. SCr was increased by a factor of 3 by 5.7x10(12) VP/kg and glomerular filtration was significantly reduced (p<0.01). This suggests that changes in renal CYP and corresponding arachidonic acid metabolites may play a role in the documented toxicity associated with the systemic administration of recombinant Ad.

Impact of transgene expression on drug metabolism following systemic adenoviral vector administration.

BACKGROUND: Systemic administration of a first-generation adenovirus expressing E. coli beta-galactosidase (AdlacZ) alters expression and function of two hepatic drug-metabolizing enzymes, cytochrome P450 (CYP) 3A2 and 2C11, for 14 days. The objective of these studies was to determine how the transgene cassette influences CYP expression and function. METHODS: Sprague-Dawley rats were given 5.7 x 10(12) viral particles (vp)/kg of either: AdlacZ, Ad expressing murine erythropoietin (Epo), Ad without a transgene (Null), or phosphate-buffered saline (Vehicle). Hepatic CYP protein expression, activity, mRNA and alanine aminotransferase (ALT) levels were analyzed 0.25, 1, 4, and 14 days following a single intravenous injection. RESULTS: Administration of Epo did not alter CYP3A2 activity, but induced RNA levels by a factor of 2 at 4 and 14 days (P< or =0.01). This vector suppressed CYP2C11 activity levels by 45% at 1 day (P< or =0.05) and RNA levels throughout the study period (P< or =0.05). The Null vector suppressed CYP3A2 activity by 36, 63, 34, and 45% at 0.25, 1, 4 and 14 days, respectively (P< or =0.05). CYP2C11 activity was suppressed 1 day after administration (41%) and RNA levels were suppressed at 6 h (53%) and 1 day (36%, P< or =0.05). In contrast, AdlacZ suppressed both CYP3A2 and 2C11 at all time points. CONCLUSIONS: The immunogenic and biological nature of the transgene cassette can influence changes in CYP3A2, but not the 2C11 isoform. The shift in transcription and translation of protein for maintenance of physiologic homeostasis to production of viral proteins and transgene product and their associated toxicity during viral infection may explain our observations.