ACTB and infection: Further, we were able to confirm actual infection of subsets through detection of viral DNA in co-cultivated subsets singly positive for CXCR4, integrin β7, and dually positive for both CCR5/CXCR4 and β7/CCR5 by amplifying the C2V3 region of the env gene with β-actin serving as housekeeping control (Figure 4C).