Surprisingly and in contrast to our findings in HeLa and NHEK cells, the infection rate was clearly enhanced in HaCaT cells (Fig. 2, upper panels), while CD9-specific siRNAs caused a strong reduction of total CD9 amounts in all cell lysates tested (Fig. 1a for HeLa, Fig. 2 lower panels for HaCaT and NHEK). This finding demonstrates that CD9 depletion causes cell-specific effects on HPV16 infection rate in different epithelial cells. The gene discussed is CD9; the disease is infection.