- Recombinant Adenovirus type 5 constructs containing IL-6 cDNA can be used to infect cells in vitro and obtain a high level of IL-6 expression and secretion into culture media. Furthermore, Ad5-IL-6 viruses can also be used to infect Balb/c mice or Sprague-Dawley rats and obtain a high level of IL-6 expression that is sustained over a period of 3-5 days. Intratracheal infection was accompanied by dramatic increases in virus-encoded IL-6 mRNA levels in rat lung tissue, raised levels of IL-6 detected in bronchoalveolar lavage fluids and in serum, and IL-6-dependent sequelae such as liver acute phase responses. This occurs in a tissue-specific manner, depending on routes of infection by the virus. Rat lungs showed a prominent expansion (10 fold in numbers) of all classes of lymphocytes, including B cells, T helper cells (CD4+) and CTL (CD8+) at day 7 after infection which resolved significantly by day 12. Thus the associated biological effects of viral vector mediated IL-6 over-expression was also transient in nature. Other tissues can be infected with Ad5 and thus can also be induced to express selected genes in a transient fashion. We are currently examining the potential for Ad recombinant cytokine vectors in therapy for cancer and for bone marrow reconstitution after transplantation. Thus the use of recombinant Ad5 vectors may have a broad application in the study of cytokine function and possibly in future therapy as a transient gene transfer approach.