Antimurine retroviral effect of doxycycline.

The tetracycline family is composed of several molecules whose antibacterial properties are due to the fixation on the bacterial ribosomes. Among those, doxycycline is one of the most potent antibiotics for which additional features have been recently discovered. Doxycycline has been found to inhibit metalloproteinases, to decrease gelatinolytic and metastatic activities of cancer cells, to have a "chondroprotective" effect in inflammatory arthritides, and to have strong antimalarial properties. In this study, a murine retrovirus producing cell line (psi CRIP-pXT1) was incubated in variable concentrations of doxycycline. The retroviral titer of this cell line was measured by the ability to transfer resistance to G418 to NIH/3T3 cells. The retroviral titer was significantly decreased by 70% when the packaging cells had been incubated with 25 microM of doxycycline at 37 degrees C. The ID50 was around 8 micrograms/ml. Astonishingly, this effect was not observed at 32 degrees C. The mechanism of this effect is still to be determined. It may be useful to be aware of this effect for uncovering all of the possible antiviral qualities of doxycycline and its related molecules, such as glycylcyclines or anthracyclines.