Single point mutations cause >100-fold underestimation of HIV-1 viral load with the COBAS TaqMan HIV-1 real-time PCR assay Running title: Underestimation of viral load by COBAS TaqMan HIV-1

1 Institute of Clinical and Molecular Virology, National Reference Center for Retroviruses, University of Erlangen-Nuremberg, Erlangen, Germany 2 Institute of Virology and Immunobiology, University of Würzburg, Würzburg. Germany 3 Institute of Virology, Medical School Hannover, Hannover, Germany 4 Max von Pettenkofer-Institute, Ludwig-Maximilians-University, Munich, Germany 5 3rd Medical Department, Paracelsus Medical University of Salzburg, Salzburg, Austria