Absence of germline infection in male mice following intraventricular injection of adenovirus

The possibility of inadvertent exposure of gonadal tissue to gene therapy vectors has raised safety concerns about germline infection. We show here that the receptor for coxsackie B viruses and adenoviruses 2 and 5 (CXADR) is expressed in mouse germ cells, suggesting the possibility that these viruses could infect germ cells. To directly assess the risk of germline infection in vivo, we injected an adenovirus carrying the germ-cell-specific protamine promoter fused to the bacterial lacZ reporter gene into the left ventricular cavity of mice and then monitored expression of the reporter gene in germ cells. To differentiate between infection of stem cells and differentiating spermatogenic cells, we analyzed expression of the reporter cassette at different times after viral delivery. Under all conditions tested, mice did not express the Escherichia coli beta-galactosidase protein in developing spermatids or in mature epididymal spermatozoa. Primary germ cells cultured in vitro were also refractory to adenoviral infection. Our data suggest that the chance of vertical germline transmission and insertional mutagenesis is highly unlikely following intracoronary adenoviral delivery.

The interaction of thrombomodulin with Ca2+

Thrombomodulin (TM) is a cofactor for protein C activation by thrombin and each residue of a consensus Ca2+ site in the sixth epidermal growth factor domain (EGF6) is essential for this cofactor activity [Nagashima, M., Lundh, E., Leonard, J.C., Morser, J. & Parkinson, J.F. (1993) J. Biol. Chem. 268, 2888-2892]. Three soluble analogs of the extracellular domain of TM, solulin (Glu4-Pro490), TME1-6 (Cys227-Cys462) and TMEi4-6 (Val345-Cys462) were prepared for equilibrium dialysis experiments by exhaustive dialysis against Ca2+-depleted buffer. However, all three analogs still contained one tightly bound Ca2+ (Kd approximately 2 microm), which could only be removed by EDTA. Epitope mapping with Ca2+-dependent monoclonal antibodies to EGF6 provided further localization of this tight Ca2+ site. Equilibrium dialysis of the soluble TM analogs in [45Ca2+] between 10 and 200 microm revealed a second Ca2+ site (Kd = 30 +/- 10 microm) in both solulin and TME1-6, but not in TMEi4-6. Ca2+ binding to this second site was unaffected by bound thrombin and we attribute it to the consensus Ca2+ site in EGF3. A 75-fold decrease in the binding affinity of thrombin to TM was observed with immobilized solulin treated with EDTA to remove the high affinity Ca2+ by measuring kassoc and kdiss rates in a BIAcoretrade mark instrument. Ca2+-dependent conformational transitions detected by CD spectroscopy in the far UV indicate a more ordered structure upon Ca2+ binding. Bound Ca2+ stabilized soluble TM against protease digestion at a trypsin-like protease-sensitive site between Arg456 and His457 in EGF6 compared with protease treatment in EDTA. Finally, TM containing EGF domains 4-6, but lacking the interdomain loop between EGF3 and 4 (TME4-6), has an identical Ca2+ dependence for the activation of protein C as found for TMEi4-6, indicating this interdomain loop is not involved in Ca2+ binding.