EP1978960A1 - USE OF 6-(3-CHLORO-2-FLUOROBENZYL)-1-Ý(2S)-1-HYDROXY-3-METHYLBUTAN-2-YL¨-7-METHOXY-4-OXO-1,4-DIHYDROQUINOLINE-3-CARBOXYLIC ACID OR SALT THEREOF FOR TREATING RETROVIRUS INFECTION