GBV-C co-infection in HIV patients downregulates CCR5 and CXCR4 surface expression on CD4 cells - Schwarze-Zander, C; Neibecker, M; Othman, S; Schulz, M; Voigt, E; Vogel, M; Wasmuth, JC; Rockstroh, JK; Spengler, U (Zeitschrift für Gastroenterologie, 2007)