SAMHD1 and HIV-1 infection: The results showed that mRNA levels of already known host restriction factors which inhibit HIV-1 infection, TRIM5α [19], MX2 [6], SAMHD1 [20], SERINC3 [21], SERINC5 [21,22], IFITM2 [8], IFITM3 [8], ApoE [23], and PSGL-1 [24] were not significantly elevated by γ-IFN (Table 1).