Evaluation of the Biodistribution, Persistence, Toxicity, and Potential of Germ-Line Transmission of a Replication-Competent Human Adenovirus Following Intraprostatic Administration in the Mouse

Abstract

Adenovirus-mediated gene transfer may hold much promise in the treatment of human cancer. However, concerns regarding vector dissemination beyond the target tissue, particularly with replication-competent viruses, require an evaluation of the persistence of viral infection in collateral tissue and vector-associated toxicities. In addition, for indications such as prostate cancer, the proximity of the point of viral administration to organs of the male reproductive system raises concerns regarding inadvertent germ-line transmission of genes carried by the virus. To address these concerns, the biodistribution, persistence, toxicity, and potential of germ-line transmission of a replication-competent adenovirus (Ad5-CD/TKrep) following intraprostatic administration in the mouse was examined. Ad5-CD/TKrep (10(10) vp, 5 x 10(11) vp/kg) was injected intraprostatically on Day 1 of the study and its presence in the major organs of the male urogenital tract (prostate, testes, seminal vesicles, and urinary bladder) and liver was determined on Days 8 and 29. For comparison, a parallel group of animals was injected with the same dose of a related replication-defective Ad5-FGNR virus. To evaluate germ-line transmission, Ad5-CD/TKrep-injected males were mated to females on Days 8 and 29 and resulting embryos were examined for AdS-CD/TKrep viral DNA. Ad5-CD/TKrep viral DNA was detected in all major organs of the adult male urogenital tract and liver 7 and 28 Days postinjection. Interestingly, relative to the replication-defective Ad5-FGNR adenovirus, the replication-competent Ad5-CD/TKrep virus accumulated to a much greater level (approximately 300-fold) and persisted for a longer period of time in prostate, testes, and liver. This difference could not be explained on the basis of differences in viral infectivity, suggesting that the AdS-CD/TKrep virus may be capable of replicating in mouse tissues in vivo. In vitro infection of six mouse cell lines representing prostate, testes, and liver demonstrated that the Ad5-CD/TKrep virus was indeed capable of replicating in these mouse cell types, albeit with reduced efficiencies relative to human cells. Despite the fact that the Ad5-CD/TKrep vector persisted in the adult male gonads and may have replicated in vivo, we observed no evidence of germ-line transmission in 149 offspring examined. To evaluate the toxicity of combining Ad5-CD/TKrep viral therapy with CD/5-FC and HSV-1 TK/GCV suicide gene therapies as a prerequisite for a human trial, an escalating dose (10(8), 10(9), 10(10) vp) of Ad5-CD/TKrep was administered intraprostatically followed by 7 days of 5-FC and GCV double prodrug therapy. Although the virus persisted in the mouse urogenital tract and liver for up to 28 days postinjection, most of the toxicities observed were expected, minimal, and self-limiting. These results lead us to believe that intraprostatic administration of the Ad5-CD/TKrep virus to humans concomitant with double suicide gene therapy will be associated with acceptable toxicities and will not result in ve...

Antitumor efficacy and tumor-selective replication with a single intravenous injection of OAS403, an oncolytic adenovirus dependent on two prevalent alterations in human cancer

“…47 Although infectious viral particles are not produced, early gene expression can lead to viral DNA replication in the liver following i.v. administration.…”

“…[49][50][51] Furthermore, Ad DNA replication can occur in mouse cells in vivo. 47 At the doses used, SCID mice are sensitive to the replication-related toxicities associated with E1A expression and viral DNA replication. Repression of E4 expression is expected to decrease viral DNA replication and consequently E1A gene dosage.…”

Wild-type adenoviruses from groups A–F evoke unique innate immune responses, of which HAd3 and SAd23 are partially complement dependent

“…in the liver, a result in accord with previous studies directly or indirectly noting that HAd5 can indeed replicate its DNA to a limited degree upon infection of the murine liver. [32][33][34][35] In contrast, although each of the other Ad serotype genomes were detected in the murine liver at 6 h.p.i., none showed evidence of significant genomic increases (replication) by 24 h.p.i. In fact, there was a significant decrease in the liver content of HAd3, HAd37 and HAd41 genomes by 24 h.p.i.…”

Characterisation of systemic dissemination of nonreplicating adenoviral vectors from tumours in local gene delivery

“…It has been widely used in cancer clinical trials. Researchers often assume that viral vectors and transgene expression are confined to solid tumours after the infusion, thereby causing minimal toxicity in normal tissues (Lu et al, 1999;Paielli et al, 2000). On the other hand, researchers in some studies have observed that transgene expression in normal tissues can be as strong as that in tumours (Toloza et al, 1996;Bramson et al, 1997;Nasu et al, 1999;Tjuvajev et al, 1999;Lohr et al, 2001;Wang et al, 2003), that adenoviral vectors are present in systemic circulation of patients in clinical trials (DeWeese et al, 2001;Nemunaitis et al, 2001), and that some animals die within a short period after intratumoral infusion (Toloza et al, 1996;Tjuvajev et al, 1999).…”