TRIM5 and HIV-1 infection: Instead, they express novel isoforms of TRIM5 (TRIM5θ and TRIM5η) and TRIM5-cyclophilin A fusion protein (TRIMcyp) that do not interfere with HIV-1 infection (Liao et al., 2007; Brennan et al., 2008; Newman et al., 2008; Virgen et al., 2008).