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Time-dependent biodistribution and transgene expression of a recombinant human adenovirus serotype 5-luciferase vector as a surrogate for rAd5-FMDV vaccines in cattle

Montiel, N.A., Smoliga, G., Arzt, J.
Veterinary immunology and immunopathology 2013 v.151 no.1-2 pp. 37
Foot-and-mouth disease virus, antigen detection, antigen-presenting cells, antigens, cattle, enzyme activity, gene expression, humans, immune response, injection site, luciferase, messenger RNA, proteins, retroviral vectors, serotypes, transgenes, vaccines
Replication-defective recombinant adenovirus 5 (rAd5) vectors carrying foot-and-mouth disease virus (FMDV) transgenes elicit a robust immune response to FMDV challenge in cattle; however mechanistic functions of vaccine function are incompletely understood. Recent efforts addressing critical interactions of rAd5 vectors with components of the bovine immune system have elucidated important aspects of induction of protective immunity against FMDV. In the current study, a rAd5-Luciferase (rAd5-Luc) surrogate vector was utilized for indirect assessment of rAd5-FMDV distribution during the first 48hours post inoculation (hpi). To compare vector distribution dynamics and time-dependent transgene expression, bovine cells were inoculated in vitro with rAd5-FMDV and rAd5-Luc vectors. Superior transgene expression was detected in cells infected with rAd5-Luc compared to rAd5-FMDV. However, both vectors behaved remarkably similar in demonstrating elevated mRNA transcription at 24 and 48hpi with peak occurrence of transgene expression at 48hpi. Injection sites of cattle inoculated with rAd5-Luc contained mononuclear inflammatory infiltrates with hexon and transgene proteins associated with antigen-presenting cells. Luciferase activity, as well as microscopic detection of luciferase antigens, peaked at 24hpi. Presence of viral mRNA also peaked at 24hpi but unlike luciferase, remained strongly detected at 48hpi. Cell-associated luciferase antigens were detected as early as 6hpi at the cortical interfolicullar areas of local LN, indicating rapid trafficking of antigen-presenting cells to lymphoid tissues. This work provides mechanistic insights on rAd5-mediated immunity in cattle and will contribute to ongoing efforts to enhance rAd5-FMDV vaccine efficacy.