You certainly can use USB but not by direct connection to the PIC. Using a serial port to program a PIC directly is possible but will rarely, if ever, meet full programming specification, however, it does work in most cases.
To use USB, you have to use another device, which may be another PIC with built in USB, as a link between the PC and target device. For example, the PicKit2 links between a PC and most PIC ICs and uses an 18F2550 as the USB node.
Brian.