CXCR4 and infection: Furthermore, evidence of cell-type specificity in thiol/disulfide exchange and HIV-1 entry, where Trx-1 is preferentially involved in virus entry of macrophages while PDI is preferentially involved in virus entry of resting CD4+ T cells, presents opportunities for tailoring therapies for effect against different tropism (CXCR4 vs. CCR5) and phase of infection (acute vs. chronic) (Stantchev et al., 2012).